1. Foreword . Preface . Introduction to Sustainability: Humanity and the Environment 1. An Introduction to Sustainability: Humanity and the Environment . What is Sustainability? . The IPAT Equation . Human Consumption Patterns and the “Rebound” Effect . Challenges for Sustainability 6. Chapter Review Questions 4. The Evolution of Environmental Policy in the United States 1. The Evolution of Environmental Policy in the United States — Chapter Introduction 2. The American Conservation Movement 3. Environmental Risk Management 4. Sustainability and Public Policy 5. Public Health and Sustainability 5. Climate and Global Change 1. Climate and Global Change — Chapter Introduction 2. Climate Processes; External and Internal Controls 3. Milankovitch Cycles and the Climate of the Quaternary 4. Modern Climate Change 5. Climate Projections 6. Biosphere 1. Biosphere — Chapter Introduction 2. Biogeochemical Cycles and the Flow of Energy in the Earth System 3. Biodiversity, Species Loss, and Ecosystem Function 4. Soil and Sustainability 7. Physical Resources: Water, Pollution, and Minerals
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1. Physical Resources: Water, Pollution, and Minerals - Chapter Introduction . Water Cycle and Fresh Water Supply . Case Study: The Aral Sea - Going, Going, Gone . Water Pollution . Case Study: The Love Canal Disaster . Mineral Resources: Formation, Mining, Environmental Impact 7. Case Study: Gold: Worth its Weight? 8. Environmental and Resource Economics 1. Environmental and Resource Economics - Chapter Introduction . Tragedy of the Commons . Case Study: Marine Fisheries . Environmental Valuation . Evaluating Projects and Policies . Solutions: Property Rights, Regulations, and Incentive Policies 9. Modern Environmental Management 1. Modern Environmental Management — Chapter Introduction 2. Systems of Waste Management 3. Case Study: Electronic Waste and Extended Producer Responsibility 4. Government and Laws on the Environment 5. Risk Assessment Methodology for Conventional and Alternative Sustainability Options 10. Sustainable Energy Systems 1. Sustainable Energy Systems - Chapter Introduction 2. Environmental Challenges in Energy, Carbon Dioxide, Air, Water and Land Use 3. Case Study: Greenhouse Gases and Climate Change
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4. Energy Sources and Carriers 1. Electricity 1. Electricity 2. Fossil Fuels (Coal and Gas) 3. Nuclear Energy 4. Renewable Energy: Solar, Wind, Hydro and Biomass 2. Liquid Fuels 1. Fossil Fuel (Oil) 2. The Conversion of Biomass into Biofuels 3. Heat 1. Geothermal Heating and Cooling o. Energy Uses 1. Electric and Plug-in Hybrids 2. Combined Heat and Power 6. Applications of Phase Change Materials for Sustainable Energy 11. Problem-Solving, Metrics, and Tools for Sustainability 1. Problem-Solving, Metrics, and Tools for Sustainability - Chapter Introduction 2. Life Cycle Assessment 3. Derivative Life Cycle Concepts 1. Sustainability Metrics and Rating Systems 2. Footprinting: Carbon, Ecological and Water 3. Case Study: Comparing Greenhouse Gas Emissions, Ecological Footprint and Sustainability Rating of a University 4. Food Miles . Environmental Performance Indicators 6. Case Study: UN Millennium Development Goals Indicator 4. Sustainability and Business
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12. Sustainability: Ethics, Culture, and History
1
ie 8.
. The Human Dimensions of Sustainability: History,
Culture, Ethics
. It’s Not Easy Being Green: Anti-Environmental
Discourse, Behavior, and Ideology
. The Industrialization of Nature: A Modern History (1500
to the present)
. Sustainability Studies: A Systems Literacy Approach
. The Vulnerability of Industrialized Resource Systems:
Two Case Studies
. Case Study: Agriculture and the Global Bee Colony
Collapse Case Study: Energy and the BP Oil Disaster Sustainability Ethics
13. Sustainable Infrastructure
1. . The Sustainable City
. Sustainability and Buildings
. Sustainable Energy Practices: Climate Action Planning . Sustainable Transportation: Accessibility, Mobility, and
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Sustainable Infrastructure - Chapter Introduction
Derived Demand
. Sustainable Stormwater Management . Case Study: A Net-Zero Energy Home in Urbana, Illinois
Foreword
Sustainability is derived from two Latin words: sus which means up and tenere which means to hold. In its modern form it is a concept born out of the desire of humanity to continue to exist on planet Earth for a very long time, perhaps the indefinite future. Sustainability is, hence, essentially and almost literally about holding up human existence. Possibly, the most succinct articulation of the issue can be found in the Report of the World Commission on Environment and Development. The report entitled “Our Common Future!!2™otel” primarily addressed the closely related issue of Sustainable Development. The report, commonly know as the Brundtland Report after the Commission Chair Gro Harlem Brundtland, stated that “Humanity has the ability to make development sustainable to ensure that it meets the needs of the present without compromising the ability of future generations to meet their own needs.” Following the concept of Sustainable Development, the commission went on to add ” Yet in the end, sustainable development is not a fixed state of harmony, but rather a process of change in which the exploitation of resources, the direction of investments, the orientation of technological development, and institutional change are made consistent with future as well as present needs. We do not pretend that the process is easy or straightforward. Painful choices have to be made. Thus, in the final analysis, sustainable development must rest on political will.” Sustainability and the closely related concept of Sustainable Development are, therefore, very human constructs whose objective is to insure the very survival of humanity in a reasonably civilized mode of existence. Here, however, I will focus primarily on Sustainability.
Report of the World Commission on Environment and Development: Our Common Future. 1987. www.un-documents.net/wced-ocf.htm.
The seriousness of the issue of Sustainability has become increasingly important and obvious over the last fifty years driven by an increasing human population with increasing per capita resource consumption on a planet which is after all finite. Note that the World population ome! increased from approximately 2.5 billion in 1950 to about 7.0 billion in 2012. Furthermore, total World consumption expenditures! {omote] rose from about 171 Billion in 1960 to approximately 44,000 billions in 2010 expressed in 2012 U.S. dollars. This is not to say that consumption is
necessarily bad, but rather that there are so many people consuming so many resources that both the World environment and human consumption will have to be managed with far more care and delicacy than has been necessary in all of the historical past.
U.S. Census Bureau, 2012. http://www.census.gov/population/international/data/idb/worldpoptotal.php. World Bank, 2012. http://databank.worldbank.org/ddp/home.do? Step=3&id=4.
A text such as the one being presented here is of paramount importance because it will help to educate the next generation of students on the very important subject of sustainability. Now sustainability is not exactly a discipline such as, for example, physics. Rather it is truly a metadiscipline drawing on nearly all of existing human knowledge in approximately equal parts and with more or less equal importance. This is not to say that different disciplines have not in the past drawn ideas from each other, creating hybrid disciplines such as, for instance, biophysics - a fusion of physics and biology. Rather, in Sustainability the range of ideas and issues reach from the depth of biological sciences to the physical sciences and to the social sciences, including politics. Additionally, the relative importance of each of these aspects seems to be about the same. The reasons for this inherent, perhaps unprecedented complexity, is that sustainability is about sustaining human existence which requires many things to be sustained including functioning economic, social, and political systems along with a supportive physical and biological environment and more.
Hence, the effort to produce a text covering the breadth of sustainability must by necessity come from a comprehensive group of specialists as is the case here. This allows each field of study to bring its own unique perspective and shed its own light on a very complex and important subject which could otherwise be intractable. The authors very interestingly point out in the preface that the text does not necessarily present a self-consistent set of ideas. Rather, a degree of diversity is accepted within the overall rubric of Sustainability and Science itself. This may be unusual for an academic text, but it is necessary here. The reason is that environmental problems of our time are both time-sensitive and evolving, and a complete understanding does not exist and may never exist. But the issues still have
to be addressed in good faith, in a timely manner, with the best science on hand. With the reader’s indulgence, I would like to draw an analogy to a physician who has the responsibility of healing or attempting to heal patients using the best available medical science in a timely manner, knowing that a complete understanding of medical science does not exist and, in fact, may never exist.
It is my sincerest hope this work shared freely and widely will be an educational milestone as humanity struggles to understand and solve the enormous environmental challenges of our time. Further, the text “Sustainability: A comprehensive Foundation,” helps to provide the intellectual foundation that will allow students to become the engines that move and maintain society on the path of Sustainability and Sustainable Development through the difficult process of change alluded to in “Our Common Future.”
Heriberto Cabezas Cincinnati, Ohio
March 2012
Preface
This text is designed to introduce the reader to the essential concepts of sustainability. This subject is of vital importance — seeking as it does to uncover the principles of the long-term welfare of all the peoples of the planet — but is only peripherally served by existing college textbooks.
The content is intended to be useful for both a broad-based introductory class on sustainability and as a useful supplement to specialist courses which wish to review the sustainability dimensions of their areas of study. By covering a wide range of topics with a uniformity of style, and by including glossaries, review questions, case studies, and links to further resources, the text has sufficient range to perform as the core resource for a semester course. Students who cover the material in the book will be conversant in the language and concepts of sustainability, and will be equipped for further study in sustainable planning, policy, economics, climate, ecology, infrastructure, and more.
Furthermore, the modular design allows individual chapters and sections to be easily appropriated — without the purchase of a whole new text. This allows educators to easily bring sustainability concepts, references, and case studies into their area of study.
This appropriation works particularly well as the text is free — downloadable to anyone who wishes to use it. Furthermore, readers are encouraged to work with the text. Provided there is attribution to the source, users can adapt, add to, revise and republish the text to meet their own needs.
Because sustainability is a cross-disciplinary field of study, producing this text has required the bringing together over twenty experts from a variety of fields. This enables us to cover all of the foundational components of sustainability: understanding our motivations requires the humanities, measuring the challenges of sustainability requires knowledge of the sciences (both natural and social), and building solutions requires technical insight into systems (such as provided by engineering, planning, and management).
Readers accustomed to textbooks that present material in a unitary voice might be surprised to find in this one statements that do not always agree. Here, for example, cautious claims about climate change stand beside Sweeping pronouncements predicting future social upheaval engendered by a warming world. And a chapter that includes market-based solutions to environmental problems coexists with others that call for increased government control. Such diversity of thought characterizes many of the fields of inquiry represented in the book; by including it, we invite users to engage in the sort of critical thinking a serious study of sustainability requires.
It is our sincerest hope that this work is shared freely and widely, as we all struggle to understand and solve the enormous environmental challenges of our time.
An Introduction to Sustainability: Humanity and the Environment
Learning Objectives After reading this chapter, students should be able to
e learn the meaning of sustainability in its modern context
e acquire a basic facility for using the IPAT equation
e learn about patterns of human consumption
e understand the major factors that contribute to unsustainable impacts
What is Sustainability?
In 1983 the United Nations General Assembly passed resolution 38/161 entitled “Process of Preparation of the Environmental Perspective to the Year 2000 and Beyond,” establishing a special commission whose charge was:
a. To propose long-term environmental strategies for achieving sustainable development to the year 2000 and beyond;
b. To recommend ways in which concern for the environment may be translated into greater co-operation among developing countries and between countries at different stages of economic and social development and lead to the achievement of common and mutually supportive objectives which take account of the interrelationships between people, resources, environment and development;
c. To consider ways and means by which the international community can deal more effectively with environmental concerns, in the light of the other recommendations in its report;
d. To help to define shared perceptions of long-term environmental issues and of the appropriate efforts needed to deal successfully with the problems of protecting and enhancing the environment, a long-term agenda for action during the coming decades, and aspirational goals for the world community, taking into account the relevant resolutions of the session of a special character of the Governing Council in 1982.
The commission later adopted the formal name “World Commission on Environment and Development” (WCED) but became widely known by the name of its chair Gro Harlem Brundtland, a medical doctor and public health advocate who had served as Norway’s Minister for Environmental Affairs and subsequently held the post of Prime Minister during three periods. The commission had twenty-one members drawn from across the globe, half representing developing nations. In addition to its fact-finding activities on the state of the global environment, the commission held fifteen meetings in various cities around the world seeking firsthand experiences on the how humans interact with the environment. The Brundtland Commission issued its final report “Our Common Future” in 1987.
Although the Brundtland Report did not technically invent the term “sustainability,” it was the first credible and widely-disseminated study that probed its meaning in the context of the global impacts of humans on the environment. Its main and often quoted definition refers to sustainable development as “...development that meets the needs of the present without compromising the ability of future generations to meet their own needs.” The report uses the terms “sustainable development,” “sustainable,” and “sustainability” interchangeably, emphasizing the connections among social equity, economic productivity, and environmental quality. The pathways for integration of these may differ nation by nation; still these pathways must share certain common traits: “the essential needs of the world's poor, to which overriding priority should be given, and the idea of limitations imposed by the state of technology and social organization on the environment's ability to meet present and future needs.”
Thus there are three dimensions that sustainability seeks to integrate: economic, environmental, and social (including sociopolitical). Economic interests define the framework for making decisions, the flow of financial capital, and the facilitation of commerce, including the knowledge, skills, competences and other attributes embodied in individuals that are relevant to economic activity. Environmental aspects recognize the diversity and interdependence within living systems, the goods and services produced by the world’s ecosystems, and the impacts of human wastes. Socio-political refers to interactions between institutions/firms and people, functions expressive of human values, aspirations and well-being, ethical issues, and decision-making that depends upon collective action. The report sees these three elements as part of a highly integrated and cohesively interacting, if perhaps poorly understood, system.
The Brundtland Report makes it clear that while sustainable development is enabled by technological advances and economic viability, it is first and foremost a social construct that seeks to improve the quality of life for the world’s peoples: physically, through the equitable supply of human and ecological goods and services; aspirationally, through making available the widespread means for advancement through access to education, systems of justice, and healthcare; and strategically, through safeguarding the interests of generations to come. In this sense sustainability sits among a series of
human social movements that have occurred throughout history: human rights, racial equality, gender equity, labor relations, and conservation, to name a few.
Overlapping Themes of the Sustainability Paradigm A depiction of the sustainability paradigm in terms of its three main components, showing various intersections among them. Source: International Union for the Conservation of Nature
The intersection of social and economic elements can form the basis of social equity. In the sense of enlightened management, "viability" is formed through consideration of economic and environmental interests. Between environment and social elements lies “bearability,” the recognition that the functioning of societies is dependent on environmental resources and services. At the intersection of all three of these lies sustainability.
The US Environmental Protection Agency (US EPA) takes the extra step of drawing a distinction between sustainability and sustainable development, the former encompassing ideas, aspirations and values that inspire public and private organizations to become better stewards of the environment and that promote positive economic growth and social objectives, the latter implying that environmental protection does not preclude economic
development and that economic development must be ecologically viable now and in the long run.
The Chapter The Evolution of Environmental Policy in the United States presents information on how the three components that comprise sustainability have influenced the evolution of environmental public policy.
greater detail the ethical basis for sustainability and its cultural and historical significance.
Glossary
sustainable development Development that meets the needs of the present without compromising the ability of future generations to meet their own needs.
The IPAT Equation
As attractive as the concept of sustainability may be as a means of framing our thoughts and goals, its definition is rather broad and difficult to work with when confronted with choices among specific courses of action. The Chapter Problem-Solving, Metrics, and Tools for Sustainability is devoted to various ways of measuring progress toward achieving sustainable goals, but here we introduce one general way to begin to apply sustainability concepts: the IPAT equation.
As is the case for any equation, IPAT expresses a balance among interacting factors. It can be stated as Equation:
I=PxAxT
where I represents the impacts of a given course of action on the environment, P is the relevant human population for the problem at hand, A is the level of consumption per person, and T is impact per unit of consumption. Impact per unit of consumption is a general term for technology, interpreted in its broadest sense as any human-created invention, system, or organization that serves to either worsen or uncouple consumption from impact. The equation is not meant to be mathematically rigorous; rather it provides a way of organizing information for a “first- order” analysis.
Suppose we wish to project future needs for maintaining global environmental quality at present day levels for the mid-twenty-first century. For this we need to have some projection of human population (P) and an idea of rates of growth in consumption (A).
World Population: 1950-2050
os
Population (billions)
OFNWA TAN OOO
World Population Growth Source: U.S. Census Bureau, International Data Base, December 2010 Update
Figure World Population Growth suggests that global population in 2050 will grow from the current 6.8 billion to about 9.2 billion, an increase of 35%. Global GDP (Gross Domestic Product, one measure of consumption) varies from year to year but, using Figure Worldwide Growth of Gross Domestic Product as a guide, an annual growth rate of about 3.5% seems historically accurate (growth at 3.5%, when compounded for forty years, means that the global economy will be four times as large at mid-century as today).
Real 2 Growth
Rate
(%) 0
-4 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
Year
Worldwide Growth of Gross Domestic Product Source: CIA World Factbook, Graph from IndexMundi
Thus if we wish to maintain environmental impacts (1) at their current levels (i.e. Ino59 = In919), then
Equation: P2019 X Azoio X T2010 = P2050 < Azos0 X T2050 or Equation: Toso _ Poono0 ¥ Aw _ 1 5 1 _ ft T5010 P2950 A250 1.35 4 5.4
This means that just to maintain current environmental quality in the face of growing population and levels of affluence, our technological decoupling will need to reduce impacts by about a factor of five. So, for instance, many recently adopted “climate action plans” for local regions and municipalities, such as the Chicago Climate Action Plan, typically call for a reduction in
greenhouse gas emissions (admittedly just one impact measure) of eighty percent by mid-century. The means to achieve such reductions, or even whether or not they are necessary, are matters of intense debate; where one group sees expensive remedies with little demonstrable return, another sees opportunities for investment in new technologies, businesses, and employment sectors, with collateral improvements in global and national well-being.
Human Consumption Patterns and the “Rebound” Effect
In 1865 William Jevons (1835-1882), a British economist, wrote a book entitled “The Coal Question,” in which he presented data on the depletion of coal reserves yet, seemingly paradoxically, an increase in the consumption of coal in England throughout most of the 19" century. He theorized that significant improvements in the efficiency of the steam engine had increased the utility of energy from coal and, in effect, lowered the price of energy, thereby increasing consumption. This is known as the Jevons paradox, the principle that as technological progress increases the efficiency of resource utilization, consumption of that resource will increase. Increased consumption that negates part of the efficiency gains is referred to as “rebound,” while overconsumption is called “backfire.” Such a counter-intuitive theory has not been met with universal acceptance, even among economists (see, for example, “The Efficiency Dilemma”). Many environmentalists, who see improvements in efficiency as a cornerstone of sustainability, openly question the validity of this theory. After all, is it sensible to suggest that we not improve technological efficiency?
Whether or not the paradox is correct, the fact that it has been postulated gives us pause to examine in somewhat greater depth consumption patterns of society. If we let Q be the quantity of goods and services delivered (within a given time period) to people, and R be the quantity of resources consumed in order to deliver those goods and services, then the IPAT equation can be rewritten in a slightly different way as:
Equation: _ GDP Q es I | P |» Fea «|B * |
R
where 13 represents the “resource intensity,” and [4] is the impact created per unit of resources
consumed. Rearranging this version of the equation gives: Equation:
ro-(f
which says simply that resources consumed are equal to the quantity of goods and services Q R use efficiency, also known as “resource productivity” or “eco-efficiency,” an approach that seeks to minimize environmental impacts by maximizing material and energy efficiencies of production. Thus we can say:
Equation:
delivered times the resource intensity. The inverse of resource intensity is called the resource
Eco — efficiency
R=Q*x foray |
that is, resources consumed are equal to goods and services delivered divided by eco-efficiency. Whether or not gains in eco-efficiency yield genuine savings in resources and lower environmental
impacts depends on how much, over time, society consumes of a given product or service (i.e. the
relative efficiency gain, a) must outpace the quantity of goods and services delivered a . In the
terms of Jevons paradox, if af = ac then the system is experiencing “backfire.”
Part of the problem in analyzing data pertaining to whether or not such “overconsumption” is happening depends on the specific good or service in question, the degree to which the data truly represent that good or service, and the level of detail that the data measure. Table Historical Efficiency and Consumption Trends in the United States summarizes some recent findings from the literature on the comparative efficiency and consumption for several activities over extended periods of observation. Taken collectively these activities capture several basic enabling aspects of modern society: major materials, transportation, energy generation, and food production. In all cases the data oe that over the long term, consumption outpaces gains in efficiency by wide
margins, (i.e., woe = Ae), It should also be noted that in all cases, the increases in consumption
are significantly greater than increases in population. The data of Table Historical Efficiency and Consumption Trends in the United States do not verify Jevons paradox; we would need to know something about the prices of these goods and services over time, and examine the degree to which substitution might have occurred (for instance aluminum for iron, air travel for automobile travel). To see if such large increases in consumption have translated into comparable decreases in environmental quality, or declines in social equity, other information must be examined. Despite this, the information presented does show a series of patterns that broadly reflect human consumption of goods and services that we consider essential for modern living and for which efficiency gains have not kept pace; in a world of finite resources such consumption patterns cannot continue indefinitely.
Avg Annual Avg Annual Efficiency Increase in Time Improvement Consumption Ratio: Activity Period (%) (%) Consumption/Efficiency ; 1800- Pig Iron 1990 14 4.1 3.0 : 1900- Aluminum 2005 12 9.8 AS a 1920- Fertilizer 2000 1.0 8.8 8.9 Electricity- 1920- 13 5.7 45
Coal 2007
Activity
Electricity- Oil
Electricity- Nat Gas
Freight Rail Travel
Air Passenger Travel
Motor Vehicle Travel
Time Period
1920- 2007
1920- 2007
1960- 2006
1960- 2007
1940- 2006
Avg Annual Efficiency Improvement (%)
15
0.3
Avg Annual Increase in Consumption (%)
Oc
9.6
2.0
6.3
3.8
Ratio: Consumption/Efficiency
4.2
5.5
12
4.9
11.0
Historical Efficiency and Consumption Trends in the United States Source: Dahmus and
Gutowski, 2011
Our consumption of goods and services creates a viable economy, and also reflects our social needs. For example, most of us consider it a social good that we can travel large distances rather quickly, safely, and more or less whenever we feel the need. Similarly, we realize social value in having aluminum (lightweight, strong, and ductile) available, in spite of its energy costs, because it makes so many conveniences, from air travel to beverage cans, possible. This is at the center of the sustainability paradigm: human behavior is a social and ethical phenomenon, not a technological one. Whether or not we must “overconsume” to realize social benefits is at the core of sustainable solutions to problems.
Resources
For more information about eco-efficiency, see the World Business Council for Sustainable Development report titled "Eco-Efficiency: Creating more value with less impact"
References
Dahmus, J. B., and T. G. Gutowski (2011) “Can Efficiency Improvements Reduce Resource Consumption? A Historical Analysis of Ten Activities” Journal of Industrial Ecology (accepted for
publication).
Glossary
eco-efficiency An approach that seeks to minimize environmental impacts by maximizing material and energy efficiencies of production.
Jevons paradox The principle that as technological progress increases the efficiency of resource utilization, consumption of that resource will increase.
overconsumption A long-term result in which the increase in consumption is greater than the efficiency improvement
Challenges for Sustainability
The concept of sustainability has engendered broad support from almost all quarters. In a relatively succinct way it expresses the basis upon which human existence and the quality of human life depend: responsible behavior directed toward the wise and efficient use of natural and human resources. Such a broad concept invites a complex set of meanings that can be used to support divergent courses of action. Even within the Brundtland Report a dichotomy exists: alarm over environmental degradation that typically results from economic growth, yet seeing economic growth as the main pathway for alleviating wealth disparities.
The three main elements of the sustainability paradigm are usually thought of as equally important, and within which tradeoffs are possible as courses of action are charted. For example, in some instances it may be deemed necessary to degrade a particular ecosystem in order to facilitate commerce, or food production, or housing. In reality, however, the extent to which tradeoffs can be made before irreversible damage results is not always known, and in any case there are definite limits on how much substitution among the three elements is wise (to date, humans have treated economic development as the dominant one of the three). This has led to the notion of strong sustainability, where tradeoffs among natural, human, and social capital are not allowed or are very restricted, and weak sustainability, where tradeoffs are unrestricted or have few limits. Whether or not one follows the strong or weak form of sustainability, it is important to understand that while economic and social systems are human creations, the environment is not. Rather, a functioning environment underpins both society and the economy.
This inevitably leads to the problem of metrics: what should be measured and how should the values obtained be interpreted, in light of the broad goals of the sustainability paradigm? The Chapter Problem-Solving, Metrics, and Tools for Sustainability addresses this in detail, but presented here is a brief summary of the findings of the Millennium Ecosystem Assessment (MEA), a project undertaken by over a thousand internationally recognized experts, from 2001-2005, who assessed the state of the world’s major ecosystems and the consequences for humans as a
result of human-induced changes. In its simplest form, a system is a collection of parts that function together. The MEA presents findings as assessments of ecosystems and ecosystem services: provisioning services such as food and water; regulating services such as flood control, drought, and disease; supporting services such as soil formation and nutrient cycling; and cultural services such as recreational, spiritual, religious and other nonmaterial benefits. MEA presents three overarching conclusions:
"Approximately 60% (15 out of 24) of the ecosystem services examined are being degraded or used unsustainably, including fresh water, capture fisheries, air and water purification, and the regulation of regional and local climate, natural hazards, and pests. The full costs of the loss and degradation of these ecosystem services are difficult to measure, but the available evidence demonstrates that they are substantial and growing. Many ecosystem services have been degraded as a consequence of actions taken to increase the supply of other services, such as food. These trade-offs often shift the costs of degradation from one group of people to another or defer costs to future generations." "There is established but incomplete evidence that changes being made are increasing the likelihood of nonlinear changes in ecosystems (including accelerating, abrupt, and potentially irreversible changes) that have important consequences for human well- being. Examples of such changes include disease emergence, abrupt alterations in water quality, the creation of “dead zones” in coastal waters, the collapse of fisheries, and shifts in regional climate." "The harmful effects of the degradation of ecosystem services are being borne disproportionately by the poor, are contributing to growing inequities and disparities across groups of people, and are sometimes the principal factor causing poverty and social conflict. This is not to say that ecosystem changes such as increased food production have not also helped to lift many people out of poverty or hunger, but these changes have harmed other individuals and communities, and their plight has been largely overlooked. In all regions, and particularly in sub-Saharan Africa, the condition and management of ecosystem services is a dominant factor influencing prospects for reducing poverty."
Organizations such as the World Commission on Environment and Development, the Millennium Ecosystem Assessment, and several others
including the Intergovernmental Panel on Climate Change, the Organization for Economic Cooperation and Development, and the National Academy. Report to Congress have all issued reports on various aspects of the state of society and the environment. The members of these groups are among the best experts available to assess the complex problems facing human society in the 21° century, and all have reached a similar conclusion: absent the enactment of new policies and practices that confront the global issues of economic disparities, environmental degradation, and social inequality, the future needs of humanity and the attainment of our aspirations and goals are not assured.
Glossary
ecosystems Dynamic systems of human, plant, animal, and microorganism communities and the nonliving environment that interact as a functional unit
ecosystem services The benefits humans receive from ecosystems
strong sustainability All forms of capital must be maintained intact independent of one another. The implicit assumption is that different forms of capital are mainly complementary; that is, all forms are generally necessary for any form to be of value. Produced capital used in harvesting and processing timber, for example, is of no value in the absence of stocks of timber to harvest. Only by maintaining both natural and produced capital stocks intact can non-declining income be assured.
weak sustainability All forms of capital are more or less substitutes for one another; no regard has to be given to the composition of the stock of capital. Weak sustainability allows for the depletion or degradation of natural resources, so long as such depletion is offset by increases in the stocks of other forms of capital (for example, by investing royalties from depleting mineral reserves in factories).
Chapter Review Questions Exercise:
Problem: What are the essential aspects of “sustainability” as defined in the Brundtland Report?
Exercise:
Problem:
Define “strong” and “weak” sustainability and give examples of each. Exercise:
Problem:
State, in your own words, the meaning of the “IPAT” equation? Exercise: Problem:
What is the “rebound” effect and how is it related to human patterns of consumption?
The Evolution of Environmental Policy in the United States — Chapter Introduction
In this module, the Chapter The Evolution of Environmental Policy in the United States is introduced.
Introduction
It is not uncommon to think of the sustainability paradigm as being a recent interpretation of environmental policy, one that was given credence by the United Nations report "Our Common Future" (the Brundtland Report) when it was first presented in 1987. Certainly the period during the final decade of the twentieth century was witness to significant growth in our understanding of the complexity and global reach of many environmental problems and issues, and as discussed in Chapter An Introduction to Sustainability; Humanity and the Environment, the Brundtland report gave a Clear voice to these concerns through its analysis of human dependency and quality of life on ecological systems, social networks, and economic viability—systems that are closely intertwined and that require more integrated approaches to solving the many problems that confront humanity at this time. It is also true that it was among the first widely disseminated writings to define and use the modern meaning of the term "sustainable" through the often-quoted concept of "sustainable development." However, it would be a mistake to conclude that sustainability as a mental construct and policy framework for envisioning the relationship of humans and nature came into being suddenly and at a single moment in time. Most environmental historians who have studied U.S. policy have discerned at least three distinct periods during which new concepts and ideas, scientific understandings, technological advances, political institutions, and laws and regulations came or were brought into being in order to understand and manage human impacts on the environment. These were (1) the American conservation movement, (2) the rise of environmental risk management as a basis for policy, and (3) the integration of social and economic factors to create what we now refer to as the sustainability paradigm. In this chapter we will explore the roots of modern sustainability (Module The American Conservation Movement), see how our thinking about the environment has shifted (Module Environmental Risk Management), and examine the ways that our
environmental public policies have changed through time (Module Sustainability and Public Policy). Along the way it is important to understand that this has been an evolutionary process and that these environmental "eras," while reflecting the norms, attitudes, and needs of the day, are still very much embodied within the modern concept of sustainability.
The American Conservation Movement In this module, the history of environmental policy in the United States and the role of different groups in shaping environmental policy is discussed.
Learning Objectives After reading this module, students should be able to
¢ understand the history of environmental policy in the United States and the role of different groups in shaping environmental policy
Introduction
To most early colonists who immigrated to North America, for whom the concept of “wastage” had no specific meaning, the continent was a land of unimaginably vast resources in which little effort was made to treat, minimize, or otherwise manage. This is not surprising, when one stand of trees was consumed for housing or fuel, another was nearby; when one field was eroded to the point of limited fertility, expansion further inland was relatively simple; when rivers became silted so that fisheries were impaired, one moved further upstream; and when confronted with endless herds of wild animals, it was inconceivable that one might over-consume to the point of extinction. European-settled America was a largely agrarian society and, apart from the need to keep spaces productive and clear of debris, there was little incentive to spend time and energy managing discharges to the “commons” (see Module The Tragedy of the Commons). These attitudes persisted well into the 19" century and aspects of them are still active in the present day. While such practices could hardly be said to constitute an “environmental policy,” they did serve the purpose of constellating a number of groups into rethinking the way we went about managing various aspects of our lives, in particular our relationship to the land and the resources it contained or provided. As early as the mid-18" century, Jared Eliot (1685-1763) of Connecticut, a minister, doctor, and farmer, wrote a series of treatises on the need for better farming methods. He summarized:
"When our fore-Fathers settled here, they entered a Land which probably never had been Ploughed since the Creation, the Land being new they
depended upon the natural Fertility of the Ground, which served their purpose very well, and when they had worn out one piece they cleared another, without any concer to amend their Land...(Carman, Tugwell, & True, 1934, p. 29)."
Although Eliot avidly instructed his fellow farmers on better methods of “field husbandry,” there is little evidence that his writings had a lasting effect (he is most known for advances in the design of the “drill plough,” an early planter that produced even rows of crops, increasing yields).
By 1850, the population of the United States was approaching 25 million and increasing at the rate of three to four percent per year (for comparison the population of England was about 26 million, of France 36 million, and Germany about 40 million). Although the westward migration across North America was well underway, most people still lived within a relatively narrow strip of land along the east coast. By modern measures the United States was not densely populated, and yet the perception of the country as “big” and on the international stage was in contrast to the mentality just a few decades before of a new world that had broken with the old, one of endless open spaces and inexhaustible resources. The country was also becoming more urbanized (about 15 percent of the population lived in cities, three times the proportion of just fifty years before), and increasingly literate.
Thus by the mid-19" century the American public was prepared to listen to the messages of various groups who had become concerned about the impacts of growth on society. Three groups in particular, of considerably different sympathies and character, came to have profound influences on the way we thought of ourselves in relation to the environment, on our land use policies, and on providing environmental goods and services to the growing population: the “resource efficiency” group, the transcendentalist movement, and organized industrial interests.
Resource Efficiency
As typified by the concerns of Jared Eliot nearly a century before, there were always some who were alarmed at widespread agricultural practices
that were wasteful, inefficient and, using the modern terminology, unsustainable. By the early 1800s the cumulative impacts of soil erosion and infertility, decreasing crop yields, and natural barriers to expansion such as terrain and poor transportation to markets led to an organized effort to understand the causes of these problems, invent and experiment with new, more soil-conserving and less wasteful practices, communicate what was being learned to the public, and begin to build government institutions to promote better stewardship of the land and its resources. Although initial conservation concerns were associated with farming, the same approach soon found its way into the management of forests and timbering, wastes from mining and smelting, and by the end of the century the control of human disease outbreaks (most commonly associated with cholera and typhoid) and the impact of chemical exposure on workers. There were many individuals who contributed to understanding the scientific underpinnings of the environment and educating practitioners: Eugene Hilgard (agricultural science), John Wesley Powell (water rights), George Perkins Marsh (ecological science), Franklin Hough and Gifford Pinchot (sustainable forestry), J. Sterling Morton (forestry and environmental education; co-founder of Arbor Day), Frederick Law Olmsted (landscape architecture), and Alice Hamilton (industrial hygiene), to name a few. These resource conservationists were instrumental in applying scientific methods to solving the problems of the day, problems that were rooted in our behavior toward the environment, and that had serious consequences for the well-being of people. It was as a result of these efforts that the basis for the fields of environmental science and engineering, agronomy and agricultural engineering, and public health was established. Over time these fields have grown in depth and breadth, and have led to the establishment of new areas of inquiry.
Just as importantly, several federal institutions were created to oversee the implementation of reforms and manage the government’s large land holdings. Legislation forming the Departments of the Interior (1849), and Agriculture (1862), the U.S. Forest Service (1881), the Geological Survey (1879), and the National Park Service (1916) were all enacted during this period. It was also the time when several major conservation societies, still active today, came into being: the Audubon Society (1886), the Sierra Club
(1892), and the National Wildlife Federation (1935). Arbor Day was first celebrated in 1872, and Bird Day in 1894.
The Transcendental Movement
It is beyond the scope of this text to analyze in great depth the basis of the transcendental movement in America. It arose in the 1830s in reaction to the general state of culture and society, increasing urbanism, and the rigidity of organized religions of the time. It professed a way of thinking in which the individual’s unique relationship to their surroundings was valued over conformity and unreflective habits of living. But however philosophical its aims and ethereal its goals, transcendentalism had a profound connection to the natural environment; indeed, it is difficult to understand without reference to human-environmental interactions and a re-envisioning of the social contract of humanity with nature. Such were conditions at the time that transcendentalism resonated with an increasingly literate society, and became a major force in the further development of conservation as an accepted part of the American experience.
The acknowledged leader of the transcendental movement was Ralph Waldo Emerson (1803-1882). In his seminal essay Nature (1836), Emerson sets the tone for a new way of envisioning our relation to the natural world:
To speak truly, few adult persons can see nature. Most persons do not see the sun. At least they have a very superficial seeing. The sun illuminates only the eye of the man, but shines into the eye and the heart of the child. The lover of nature is he whose inward and outward senses are still truly adjusted to each other; who has retained the spirit of infancy even into the era of manhood. His intercourse with heaven and earth, becomes part of his daily food. In the presence of nature, a wild delight runs through the man, in spite of real sorrows. Nature says, -- he is my creature, and maugre all his impertinent griefs, he shall be glad with me. Not the sun or the summer alone, but every hour and season yields its tribute of delight; for every hour and change corresponds to and authorizes a different state of the mind, from breathless noon to grimmest midnight. Nature is a setting that fits equally well a comic or a mourning piece. In good health, the air is a cordial of incredible virtue. Crossing a bare common, in snow puddles, at twilight,
under a clouded sky, without having in my thoughts any occurrence of special good fortune, I have enjoyed a perfect exhilaration. I am glad to the brink of fear. In the woods too, a man casts off his years, as the snake his slough, and at what period so ever of life, is always a child. In the woods, is perpetual youth. Within these plantations of God, a decorum and sanctity reign, a perennial festival is dressed, and the guest sees not how he should tire of them in a thousand years. In the woods, we return to reason and faith. There I feel that nothing can befall me in life, -- no disgrace, no calamity, (leaving me my eyes,) which nature cannot repair. Standing on the bare ground, -- my head bathed by the blithe air, and uplifted into infinite space, -- all mean egotism vanishes. I become a transparent eye-ball; I am nothing; I see all; the currents of the Universal Being circulate through me; I am part or particle of God. The name of the nearest friend sounds then foreign and accidental: to be brothers, to be acquaintances, -- master or servant, is then a trifle and a disturbance. I am the lover of uncontained and immortal beauty. In the wilderness, I find something more dear and connate than in streets or villages. In the tranquil landscape, and especially in the distant line of the horizon, man beholds somewhat as beautiful as his own nature. (Emerson, 1836).
Here Emerson makes clear that his connection to the “Universal Being” is made possible through communion with Nature, a creation so much greater than he that he sees his physical reality as “nothing,” but his true nature (i.e. his soul) becomes visible in the “tranquil landscape,” and the “distant line of the horizon.” Such metaphorical language was and remains a powerful reminder that our existence is dependent on the natural world, and that we mismanage the environment at our peril.
Kindred Spirits. The painting, dated 1849, depicts the artist, Thomas Cole, and poet, William Cullen Bryant. Source: Asher Brown Durand via Wikimedia Commons
Yet, it is difficult to fully appreciate Emerson’s vision of humans and nature through language alone. As might be expected, the counter-reaction to the state of society and its attitudes toward the environment found expression in other media as well, in particular the rise of a cadre of American landscape artists. The camera had not yet been perfected, and of course there was no electronic media to compete for people’s attention, thus artists’ renditions of various scenes, especially landscapes, were quite popular. Figure Kindred
Spirits, a rendering by A.B. Durand (1796-1886) of an artist and a poet out for a hike amid a lush forest scene captures much of the essence of transcendental thought, which had strongly influenced Durand’s style. The offset of the human subjects, to left-of-center, is purposeful: the main subject is nature, with humans merely a component. This theme carried through many of the landscapes of the period, and helped to define what became known, among others, as the “Hudson River School,” whose artists depicted nature as an otherwise inexpressible manifestation of God. This is further expressed in the painting, In the Heart of the Andes, by Frederic Church (Figure In the Heart of the Andes). Here, the seemingly sole theme is the landscape itself, but closer inspection (see detail in red square) reveals a small party of people, perhaps engaged in worship, again offset and virtually invisible amid the majesty of the mountains.
In the Heart of the Andes. The painting, dated 1859, depicts a
majestic landscape and closer inspection reveals a small party of
people near the bottom left. Source: Frederic Edwin Church via Wikimedia Commons.
Other notable contributors to the transcendental movement were Henry David Thoreau (1817-1862), abolitionist and author of Walden and Civil Disobedience, Margaret Fuller (1810-1850), who edited the transcendental journal “The Dial” and wrote Woman in the Nineteenth Century, widely considered the first American feminist work, and Walt Whitman (1819-
1892) whose volume of poetry Leaves of Grass celebrates both the human form and the human mind as worthy of praise.
It is important to recognize that the transcendental redefinition of our social contract with the environment was holistic. Within it can be found not only a new appreciation of nature, but also the liberation of the human mind from convention and formalism, attacks on slavery, the need for racial equality, concern for universal suffrage and women’s rights, and gender equity. In many ways it was a repositioning of the ideals of the enlightenment that had figured so prominently in the founding documents of the republic. These social concerns are represented today within the sustainability paradigm in the form of such issues as environmental justice, consumer behavior, and labor relations.
Transcendentalism as a formal movement diminished during the latter half of the 19" century, but it had a far-reaching influence on the way society perceived itself relative to the environment. Perhaps no one is more responsible for translating its aspirations into environmental public policy than John Muir (1838-1914), a Scottish-borm immigrant who was heavily influenced by Emerson’s writings (it is said that the young Muir carried with him a copy of Nature from Scotland). The two first met in 1871 during a camping trip to the Sierra Mountains of California. Upon learning of Emerson’s planned departure, Muir wrote to him on May 8, 1871 hoping to convince him to stay longer, “I invite you join me in a months worship with Nature in the high temples of the great Sierra Crown beyond our holy Yosemite. It will cost you nothing save the time & very little of that for you will be mostly in Eternity” (Chou, 2003).
Muir was a naturalist, author, organizer (founder of the Sierra Club), and as it turns out a remarkably effective political activist and lobbyist. His association with Theodore Roosevelt (1858-1919, 26" president of the United States), began with a 1903 campaign visit by Roosevelt to California, where he specifically sought out Muir, whose reputation was by then well known, as a guide to the Yosemite area (see Figure Roosevelt and Muir).
Roosevelt and Muir Theodore Roosevelt and John Muir at Yosemite National Park in 1903.
It was one of Muir’s special talents that he could bridge across their rather different views on the environment (he a strict preservationist, Roosevelt a practical outdoorsman). By all accounts they had frank but cordial exchanges; for example, upon viewing the giant Sequoias, Muir remarked to Roosevelt, “God has cared for these trees...but he cannot save them from fools — only Uncle Sam can do that.” Roosevelt was so taken with his companion that he insisted they avoid political crowds and camp together overnight in the mountains.
The subsequent legacy of the Roosevelt administration in the name of conservation, even by today’s standards, was significant. Known as the “conservation president,” Roosevelt was responsible for 225 million acres of land added to the U.S. Forest Service, and the creation of 50 wildlife refuges and 150 national forests representing, in total, 11 percent of the total land area of the 48 contiguous states.
The Role of Industry
Today the behavior of industry toward the environment is often portrayed as either indifferent or hostile, whether true or not, and it was no different during the formative period of American conservation. The industries of the day — agriculture, timber, and mining — enabled by the major transportation sector — railroads and steamboats — had little incentive to manage their emissions to the environment responsibly, or to use natural resources wisely. Regulations were few, the science underpinning environmental impacts was nascent, the commons itself was viewed as essentially infinite, and however misguided, exploitation of resources and the generation of a certain amount of waste was seen as a necessary byproduct of expansion, job creation, and social well-being. And yet, as human-created organizations go, industries are extraordinarily sensitive to economic conditions. If the sustainability paradigm is to be believed, then economic viability is of paramount concern and the engagement of industrial forces must of necessity be part of its enactment. These are the engines that provide employment, and that control large quantities of capital for investment. Further, viewed from the life cycle perspective of the flow of materials (refer to Module Life Cycle Assessment), products that turn raw materials into mostly waste (defined here as a quantity of material that no one values, as opposed to salable products) are simply inefficient and reduce profitability.
The Oregon Trail. The painting, dated 1869, depicts the westward migration of settlers via wagon trains, on horseback, and by foot. Source: Albert Bierstadt via Wikimedia Commons.
As noted in Resource Efficiency above, industrial activities during this time were responsible for significant environmental degradation. Policy reformers of the day, such as Carl Schurz (as secretary of the Interior) turned their attention in particular to land reforms, which impacted the expansion of railroads, and forest preservation. And yet, industry played an unquestionable role as enablers of societal shifts occurring in America by making goods and services available, increasing the wealth of the emerging middle class, and in particular providing relatively rapid access to previously inaccessible locations — in many cases the same locations that preservationists were trying to set aside. Reading, hearing stories about, and looking at pictures of landscapes of remote beauty and open spaces was alluring and stirred the imagination, but being able to actually visit these places firsthand was an educational experience that had transformative
powers. Alfred Bierstadt’s The Oregon Trail (Figure The Oregon Trail), painted in 1868, depicts the westward migration of settlers via wagon trains, on horseback, and simply walking — a journey, not without peril, that took about six months. The next year saw the completion of the transcontinental railroad, and within a few years it became possible to complete the same journey in as little as six days in comparative comfort and safety.
The movement to designate certain areas as national parks is an illustrative example of the role of industry in promoting land conservation, thereby setting in motion subsequent large conservation set-asides that reached their zenith during the Roosevelt administration. It began, in 1864, with the efforts of several California citizens to have the U.S. Congress accept most of Yosemite, which had been under the “protection” of the State of California as a national preserve. The petition cited its value “for public use, resort, and recreation,” reasoning that already reflected the combined interests of the resource efficiency group, preservationists, and business opportunists. Frederick Law Olmsted (1822-1903), the landscape architect most well known for the design of New York’s Central Park, and an ardent believer in the ability of open spaces to improve human productivity, oversaw the initial efforts to manage the Yosemite area. Although the effort was infused with renewed vigor after John Muir’s arrival in the late 1860s, it wasn’t until 1906 that the park was officially designated.
In the meantime, similar interests had grown to name Yellowstone as a national park, with the same basic justification as for Yosemite. Since there were no States as yet formed in the region the pathway was more straightforward, and was made considerably easier by the lack of interest by timber and mining companies to exploit (the area was thought to have limited resource value), and the railroads who, seeing potential for significant passenger traffic, lobbied on its behalf. Thus the first national park was officially designated in 1872, only three years after the completion of the transcontinental railroad. Indeed, in relatively rapid succession the Union Pacific Railroad got behind the Yosemite efforts, and the Northern Pacific Railroad lobbied heavily for the creation of parks at Mount Rainier (1899) and Glacier (1910). By 1916, when the National Park Service was formed, sixteen national parks had been created. States too began to see value in creating and, to a degree, preserving open spaces, as evidenced by
New York’s Adirondack Park (1894), still the largest single section of land in the forty-eight contiguous states dedicated to be “forever wild.”
Results of the American Conservation Movement
With the advent of the First World War, and subsequent political, social, and economic unrest that lasted for another thirty years, actions motivated by the conservation movement declined. The coalition between the resource efficiency group and those wishing to preserve nature, always uncomfortable, was further eroded when it became clear that the main reason Congress was “setting aside” various areas was mainly to better manage commercial exploitation. And yet, the period from 1850 to 1920 left a remarkable legacy of environmental reform, and laid the foundation for future advances in environmental policy. In summary, the conservation movement accomplished the following:
e Redefined the social contract between humans and the environment, establishing a legacy of conservation as part of the American character, and a national model for the preservation of natural beauty.
e Invented the concept of national parks and forests, wildlife refuges, and other sites for commercial and recreational uses by society.
¢ Developed the first scientific understanding of how the environment functioned, integrating the scientific approach to resource management into government policy.
e Pioneered technological practices to improve resource management.
e Established the major federal institutions with responsibility for land and resource conservation.
e Communicated the impact of pollution on human health and welfare.
e Through publications and travel, exposed many to the beauty of the natural environment and the consequences of human activities.
e Finally, although sustainability as a way of envisioning ourselves in relation to the environment was still many years away, already its three principal elements, imperfectly integrated at the time, are seen clearly to be at work.
References
Carman, H.J., Tugwell, R.G., & True, R.H. (Eds.). (1934). Essays upon field husbandry in New England, and other papers, 1748-1762, by Jared Eliot. New York: Columbia University Press.
Chou, P.Y. (Ed.). (2003). Emerson & John Muir. WisdomPortal. Retrieved December 11, 2011 from http://www.wisdomportal.com/Emerson/Emerson- JohnMuir.html.
Environmental Risk Management
In this module, the following topics are covered: 1) the basic elements of the sustainability paradigm through the evolution of U.S. environmental policy, and 2) the role of risk management as modern environmental policy has been implemented.
Learning Objectives After reading this module, students should be able to
e trace the basic elements of the sustainability paradigm through the evolution of U.S. environmental policy, including the National Environmental Policy Act of 1970
e understand the role of risk management as modern environmental policy has been implemented
General Definitions
For most people, the concept of risk is intuitive and, often, experiential; for instance most people are aware of the considerably greater likelihood of suffering an injury in an automobile accident (116/100 million vehicle miles) versus suffering an injury in a commercial airplane accident (0.304/100 million airplane miles). Environmental risk can be defined as the chance of harmful effects to human health or to ecological systems resulting from exposure to any physical, chemical, or biological entity in the environment that can induce an adverse response (see Module Risk Assessment Methodology for Conventional and Alternative Sustainability Options for more detail on the science of risk assessment). Environmental risk assessment is a quantitative way of arriving at a statistical probability of an adverse action occurring. It has four main steps:
1. Identification of the nature and end point of the risk (e.g. death or disability from hazardous chemicals, loss of ecological diversity from habitat encroachment, impairment of ecosystem services, etc.)
2. Development of quantitative methods of analysis (perturbation-effect, dose-response)
3. Determination of the extent of exposure (i.e. fate, transport, and transformation of contaminants to an exposed population), and 4. Calculation of the risk, usually expressed as a statistical likelihood.
Risk management is distinct from risk assessment, and involves the integration of risk assessment with other considerations, such as economic, social, or legal concerns, to reach decisions regarding the need for and practicability of implementing various risk reduction activities. Finally, risk communication consists of the formal and informal processes of communication among various parties who are potentially at risk from or are otherwise interested in the threatening agent/action. It matters a great deal how a given risk is communicated and perceived: do we have a measure of control, or are we subject to powerful unengaged or arbitrary forces?
The Beginnings of Modern Risk Management
The beginnings of environmental risk management can be traced to the fields of public health, industrial hygiene, and sanitary engineering, which came into prominence in the latter decades of the 19" century and beginning of the 20". The spread of disease was a particularly troublesome problem as the country continued to urbanize. For instance if you lived your life in, say, Chicago during the period 1850-1900 (a typical lifespan of the day), you had about a 1 in 100 chance of dying of cholera (and a 1 in 2000 chance of dying of typhoid), of which there were periodic epidemics spread by contaminated drinking water. Chicago's solution was to cease polluting its drinking water source (Lake Michigan) by reversing the flow of its watercourses so that they drained into the adjacent basin (the Mississippi). The widespread chlorination of municipal water after 1908 essentially eliminated waterborne outbreaks of disease in all major cities (with some notable exceptions—the outbreak of chlorine-resistant Cryptosporidium parvum in Milwaukee's drinking water in 1993 resulted in the infection of 403,000 people with 104 deaths).
Parallel work on the effects of chemical exposure on workers (and poor working conditions in general) were pioneered by Alice Hamilton (1869- 1970), who published the first treatise on toxic chemical exposure
"Industrial Poisons in the United States" in 1925. Hamilton is considered the founder of the field of occupational health. In 1897 she was appointed professor of pathology at the Women's Medical School of Northwestern University, and in 1902 she accepted the position of bacteriologist at the Memorial Institute for Infectious Diseases in Chicago. Dr. Hamilton joined Jane Addams's Hull House, in Chicago, where she interacted with progressive thinkers who often gravitated there, and to the needs of the poor for whom Hull House provided services.
Environmental Contamination and Risk
Events during the period 1920-1950 took an unfortunate turn. Global conflicts and economic uncertainty diverted attention from environmental issues, and much of what had been learned during the previous hundred years, for example about soil conservation and sustainable forestry, ceased to influence policy, with resultant mismanagement on a wide scale (see Figures Texas Dust Storm and Clear Cutting, Louisiana, 1930).
Texas Dust Storm. Photograph shows a dust storm approaching Stratford, TX in 1935. Source: NOAA via
Wikimedia Commons
Clear Cutting, Louisiana, 1930. Typical cut- over longleaf pine area, on Kisatchie National Forest. Areas of this type were the first to be planted on this forest. Circa 1930s. Source: Wait, J.M. for U.S. Forest Service. U.S. Forest Service photo courtesy of the Forest History Society,
Durham, N.C.
In the aftermath of the World War II, economic and industrial activity in the United States accelerated, and a consumer-starved populace sought and demanded large quantities of diverse goods and services. Major industrial sectors, primary metals, automotive, chemical, timber, and energy expanded considerably; however there were still few laws or regulations on waste management, and the ones that could and often were invoked (e.g. the Rivers and Harbors Act of 1899) were devised in earlier times for problems of a different nature. The Module Systems of Waste Management
provides a more detailed accounting of the current framework for managing waste. Here we recount the circumstances that eventually resulted in the promulgation of environmental risk as a basis for public policy, with subsequent passage of major environmental legislation.
Zinc Smelter. Photograph shows a local smelter in a small valley town in Pennsylvania with, essentially, uncontrolled emissions. Source: The Wire Mill, Donora, PA, taken by Bruce Dresbach in 1910. Retrieved from the Library of Congress
If there were any doubts among American society that the capacity of the natural environment to absorb human-caused contamination with acceptably low risk was indeed infinite, these were dispelled by a series of well-publicized incidents that occurred during the period 1948-1978. Figure Zinc Smelter shows a local smelter in a small valley town in Pennsylvania with, essentially, uncontrolled emissions. During periods of atmospheric stability (an inversion), contaminants became trapped, accumulated, and caused respiratory distress so extraordinary that fifty deaths were recorded. Figure Noon in Donora illustrates the dramatically poor air quality, in the
form of reduced visibility, during this episode. Such incidents were not uncommon, nor were they limited to small American towns. A well- documented similar episode occurred in London, England in 1952 with at least 4000 deaths, and 100,000 illnesses resulting.
Noon in Donora. Photograph, dated October 29, 1948, illustrates the extremely poor air quality in the Pennsylvania town at the time. Source: NOAA
The generally poor state of air quality in the United States was initially tolerated as a necessary condition of an industrialized society. Although the risks of occupational exposure to chemicals was becoming more well known, the science of risk assessment as applied to the natural environment was in its infancy, and the notion that a polluted environment could actually cause harm was slow to be recognized, and even if true it was not clear what might be done about it. Nevertheless, people in the most contaminated areas could sense the effects of poor air quality: increased incidence of respiratory disease, watery eyes, odors, inability to enjoy being outside for more than a few minutes, and diminished visibility.
Cuyahoga River Fire, 1969. Photograph illustrates a 1969 fire on the Cuyahoga River, one of many fires during the time period. Source: NOAA.
Environmental degradation of the era was not limited to air quality. Emissions of contaminants to waterways and burial underground were simple and common ways to dispose of wastes. Among the most infamous episodes in pollution history were the periodic fires that floated through downtown Cleveland, Ohio on the Cuyahoga River, causing considerable damage (Figure Cuyahoga River Fire 1969), and the discovery of buried hazardous solvent drums in a neighborhood of Niagara Falls, NY in 1978, a former waste disposal location for a chemical company (Figure Love Canal).
Infrared aerial photo of Love Canal area (taken in spring 1978) showing 99th Street elementary school in center, two rings of homes bordering the landfill and LaSalle Housing Development in upper right. White patchy areas indicate barren sections where vegetation will not grow, presumably due to leaching chemical contamination.
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Love Canal. The Love Canal region of Niagara Falls, NY, 1978 showing the local grade school and neighboring houses. Source: New York State Department of Health (1981, April). Love Canal: A special report to the Governor and Legislature, p. 5.
Risk Management as a Basis for Environmental Policy
Environmental scientists of the day were also alarmed by the extent and degree of damage that they were documenting. The publication of Silent Spring in 1962 by Rachel Carson (1907-1964), about the impact of the widespread and indiscriminate use of pesticides, was a watershed moment, bringing environmental concerns before a large portion of the American, and global, public. Carson, a marine biologist and conservationist who initially worked for the U.S. Bureau of Fisheries, became a full time nature writer in the 1950s. She collected scientifically documented evidence on the effects of pesticides, particularly DDT, heptachlor, and dieldrin, on humans and mammals, and the systemic disruption they caused to ecosystems. Silent Spring is credited with bringing about a ban on the use of DDT in the United States, and setting in motion a chain of events that would ultimately result in the transformation of environmental public policy from one based on the problems and attitudes that brought about nineteenth century conservation, to one based on the management of risks from chemical toxins. The U.S. Environmental Protection Agency was established in 1970, just eight years after the publication of Silent Spring. The same year Earth Day was created.
As noted, the modules in the Chapter Modern Environmental Management contain a comprehensive treatment of the major laws and regulations that underpin the risk management approach to environmental policy. However it is worth considering one law in particular at this point, the National Environmental Policy Act of 1970 (NEPA), because it provides a legal basis for U.S. environmental policy, and lays out its terms clearly and unambiguously. NEPA established a national goal to create and maintain "conditions under which [humans] and nature can exist in productive harmony, and fulfill the social, economic and other requirements of present and future generations of Americans[emphasis added]" (NEPA, 1970). Further, NEPA saw the need for long term planning, to "fulfill the responsibilities of each generation as trustee of the environment for succeeding generations," for equity "to assure for all Americans safe, healthful, productive, and esthetically and culturally pleasing surroundings," and for economic prosperity as we "achieve a balance between population and resource use that will permit high standards of living and a wide sharing of life's amenities" (NEPA, 1970). Although the exact word "sustainable" does not appear, NEPA is in all major respects
congruent with the goals of the Brundtland Report (written 17 years later, see Chapter Introduction to Sustainability: Humanity and the Environment), retains the character of American conservation, and anticipates the need to integrate environmental quality with social and economic needs.
Every four to six years the U.S. EPA releases its Report on the Environment, a collection of data and analysis of trends on environmental quality. It is quite comprehensive; reporting on an array of measures that chart progress, or lack thereof, on human impacts on the environment and, in turn, the effects of our actions on human health. It is difficult to summarize all the information available in a concise way, however most measures of human exposure to toxic chemicals, dating in many cases back to the late 1980s, show clear downward trends, in some cases dramatically so (for example DDT in human tissues, lead in blood serum, exposure to hazardous wastes from improper disposal, exposure to toxic compounds emitted to the air). In addition, many of other indicators of environmental quality such as visibility, drinking water quality, and the biodiversity of streams, show improvement. These are success stories of the risk management approach to environmental quality. On the other hand, other measures, such as hypoxia in coastal waters, quantities of hazardous wastes generated, and greenhouse gases released are either not improving or are getting worse.
References
National Environmental Policy Act of 1970, 42 U.S.C., 4321, et seq.
Sustainability and Public Policy In this module, the problem-driven nature of policy development is discussed.
Learning Objectives After reading this module, students should be able to
e understand the problem-driven nature of policy development, from relatively local agricultural problems to regional problems often driven by industrial development to global problems associated with population- driven human consumption
Complex Environmental Problems
NEPA, both in tone and purpose, was in sharp contrast to the many environmental laws that followed in the 1970s and 1980s that defined increasingly proscriptive methods for controlling risks from chemical exposure (this is sometimes termed the "command-and-control" approach to environmental management). In many ways these laws and regulations are ill-suited to the types of environmental problems that have emerged in the past twenty years. Whereas the focus of our environmental policy has been on mitigating risk from local problems that are chemical — and media — (land, water, or air) specific, the need has arisen to address problems that are far more complex, multi- media, and are of large geographic, sometimes global, extent.
An early example of this type of shift in the complexity of environmental problems is illustrated by the phenomenon of acidic rainfall, a regional problem that occurs in many areas across the globe. Although the chemical cause of acid rain is acidic gases (such as sulfur dioxide and nitrogen oxides) released into the atmosphere from combustion processes (such as coal burning), the problem was made considerably worse because of the approach to problem solving typical of the day for episodes such as the Donora disaster (see Figures Zinc Smelter and Noon in Donora).
Hydrogen ion concentrations as pH for 1996 from measurements made at the Central Analytical Laboratory
National Atmospheric Deposition Program/National Treads Network
Printed: 09/01/97
Hydrogen Ion Concentrations as pH for 1996. Figure shows the distribution in rainfall pH in the United States for the year 1996. Source: National Atmospheric Deposition Program/National Trends Network via National Park Service.
In order to prevent the local accumulation of contaminants, emission stacks were made much taller, effectively relying on the diluting power of the atmosphere to disperse offending pollutants. The result was a significant
increase in the acidity of rainfall downwind of major sources, with associated impacts on aquatic and forest resources. Figure Hydrogen Jon Concentrations as pH for 1996 shows this pattern for the eastern United States in 1996. A more comprehensive solution to this problem (short of replacing coal as a fuel source), has involved integrated activity on many fronts: science to understand the impacts of acid rain, technology to control the release of acidic gases, politics in the form of amendments to the Clean Air Act, social equity that defined the role of regional responsibilities in the face of such large geographic disparities, and economics to understand the total costs of acid rain and design markets to spread the costs of control. Although acidic rainfall is still an issue of concern, its impacts have been mitigated to a significant degree.
Sustainability as a Driver of Environmental Policy
The level of complexity illustrated by the acid rain problem can be found in a great many other environmental problems today, among them:
e Hypoxic conditions in coastal regions of the world caused by excessive release of nutrients, principally dissolved nitrogen and phosphorous from artificial fertilizer applied to crops (in addition to the Gulf of Mexico and Chesapeake Bay in the United States, there are over 400 such areas worldwide),
e Stratospheric ozone depletion caused by the release of certain classes of chlorofluorocarbon compounds used as propellants and refrigerants (with increases in the incident of skin cancers and cataracts),
e Urbanization and sprawl, whereby the population density in urban areas, with its attendant problems (degradation of air and water quality, stormwater management, habitat destruction, infrastructure renewal, health care needs, traffic congestion, loss of leisure time, issues of social equality), continues to grow (for example eighty percent of the population of the United States, about fifty percent of global, now lives in urban regions),
e Global climate change, and its resultant impacts (increases in temperature and storm and flooding frequency, ocean acidification, displacement of human populations, loss of biodiversity, sea-level rise), caused by the human-induced emission of greenhouse gases.
Problems such as these, which require highly integrated solutions that include input from many disciplines and
problems have certain key characteristics:
e There is not universal agreement on what the problem is — different stakeholders define it differently.
e There is no defined end solution, the end will be assessed as "better" or "worse."
e The problem may change over time.
e There is no clear stopping rule — stakeholders, political forces and resource availability will make that determination on the basis of "judgments."
e The problem is associated with high uncertainty of both components and outcomes.
e Values and societal goals are not necessarily shared by those defining the problem or those attempting to make the problem better.
Wicked problems are not confined to environmental issues, for example the same characteristics arise for problems such as food safety, health care disparities, and terrorism, but in the context of environmental policy they create the need to reassess policy approaches and goals, laws and regulations, as well as methods and models for integrated research.
Table The Evolution of U.S. Environmental Policy summarizes the major attributes of U.S. environmental policy as it has evolved over the past two centuries. To most observers it would seem to be true that advances in public policy, in any realm, are driven by problems, real and perceived, that require systemic solutions. Environmental policy is no exception. Early conservationists were alarmed at the inefficiencies of human resource management and the encroachment of humans on unspoiled lands. During the 20" century many groups: scientists, economists, politicians, and ordinary citizens, became alarmed and fearful of the consequences of toxic pollutant loads to the environment that included localized effects on human health and well-being. And now, as we proceed into the 21% century, an array of complex problems that have the potential to alter substantially the structure and well-being of large segments of human societies, calls for a renewal and reassessment of our approach to environmental policy. This has, thus far, proven to be a difficult transition. Many of these complex problems have multiple causes and
impacts, affect some groups of people more than others, are economically demanding, and are often not as visibly apparent to casual observers as previous impacts, nor are the benefits perceived to be commensurate with costs. Devising a regulatory strategy for such problems requires an adaptive and flexible approach that current laws do
not foster.
Focus
Outcome
Principal Activity
Economic Focus
Regulatory Activity
Conceptual Model
Disciplinary Approach
1850-1920
Conservation/sanitation
Land
preservation/efficiency/control
of disease
Resource management reform/simple contaminant controls
Profit maximization/public health
Low
Expansion vs. preservation
Disciplinary and insular
1960-1990
Media/site/problem specific
Manage anthropocentricand ecological risk Compliance/ remediation/technological
emphasis on problem solving
Cost minimization
Heavy
Command-and-control
Multidisciplinary
1990-present
Complex regional/ global problems
Global sustainable development
Integration of social, economic, and technological information for holistic problem solving;
Strategic investments/long- term societal well-being
Adaptive and Flexible
Systems/life cycle approac!
Interdisciplinary/Integrativ
The Evolution of U.S. Environmental Policy Table summarizes the major attributes of U.S. environmental policy :
et al. (2009).
References
Batie, S. S. (2008, December). Wicked problems and applied economics. American Journal of Agricultural Economics, 90, 1176-1191 doi: 10.1111/j.1467-8276.2008.01202.x
Fiksel, J., Graedel, T., Hecht, A. D., Rejeski, D., Saylor, G. S., Senge, P. M., Swackhamer, D. L., & Theis, T. L. (2009). EPA at 40: Bringing environmental protection into the 21° century. Environmental Science and
Technology, 43, 8716-8720. doi: 10.1021/es901653f
Kreuter, M. W., DeRosa, C., Howze, E. H., & Baldwin, G. T. (2004, August). Understanding wicked problems: A key to advancing environmental health promotion. Health, Education and Behavior, 31, 441-54. doi: 10.1177/1090198104265597
Public Health and Sustainability
In this module, the following topics will be covered: 1) definition of public health, 2) public health impacts of non-sustainable development, 3) key public health impacts of climate change.
Learning Objectives After reading this module, students should be able to
e understand what public health is e recognize public health impacts of non-sustainable development e identify key public health impacts of climate change
Introduction
“Much discussion about sustainability treats the economy, livelihoods, environmental conditions, our cities and infrastructure, and social relations as if they were ends in themselves; as if they are the reason we seek sustainability. Yet their prime value is as the foundations upon which our longer-term health and survival depend.” (McMichael, 2006)
Ecological sustainability is more than just continuing the resource flows of the natural world to sustain the economic machine, while maintaining diversity of species and ecosystems. It is also about sustaining the vast support systems for health and life which could be considered the real bottom line of sustainability. Before examining the public health effects of non-sustainable development, we should define public health.
e The website for UIC’s School of Public Health says “we are passionate about improving the health and well-being of the people of Chicago, the state of Illinois, the nation and the world.”
¢ The Illinois Department of Public Health is responsible for protecting the state's 12.4 million residents, as well as countless visitors, through the prevention and control of disease and injury.”
e The New Zealand Ministry of Health defines it as “the science and art of promoting health, preventing disease and prolonging life through organized efforts of society.”
e The National Resources Defense Council an NGO devoted to environmental action, states that public health is “the health or physical well-being of a whole community.”
Impacts of Non-Sustainable Development
We have built our communities in ways that are unsustainable from many aspects. Not only does development create urban sprawl, impact land use, and fuel consumption, we can identify negative health consequences related to these development trends.
Obesity
If our communities are not walkable or bikeable, we need to drive to schools, shops, parks, entertainment, play dates, etc. Thus we become more sedentary. A sedentary lifestyle increases the risk of overall mortality (2 to 3-fold), cardiovascular disease (3 to 5-fold), and some types of cancer, including colon and breast cancer. The effect of low physical fitness is comparable to that of hypertension, high cholesterol, diabetes, and even smoking (Wei et al., 1999; Blair et al., 1996).
Economic Segregation
Walkable and safe communities provide sidewalks, bike paths, proximity, and connections to community services such as grocery stores, schools, health care, parks, and entertainment. Community design that creates a segregated housing environment with only expensive housing and no affordable housing segregates people by socio-economic level (i.e. poor from non-poor) and this generally leads to segregation by race. Lack of physical activity will occur in neighborhoods with no good green and safe recreational sites. If we have poor public transit systems partly due to lack of density (only more expensive, low-density housing) and our love of the automobile, then we have increased emissions that contribute to global warming.
The Olympics as an Example
A natural experiment during the 1996 Summer Olympic Games in Atlanta shows the impact of car use on health. During the games, peak morning traffic decreased 23% and peak ozone levels decreased 28%. Asthma- related emergency room visits by children decreased 42% while children’s emergency visits for non-asthma causes did not change during same period (Friedman, Powell, Hutwagner, Graham, & Teague, 2001). We also saw that with the Beijing Olympics in 2008 where driving days were rationed, more than 300,000 heavy-emitting vehicles (about 10% of total) were barred from the city’s administrative area in order to decrease pollution for athletes and visitors This reduced the number of vehicles by about 1.9 million or 60% of the total fleet during the Olympic Games. Emissions of black carbon, carbon monoxide and ultrafine particles were reduced by 33%, 47%, and 78% respectively compared to the year before the Olympics. Frequency of respiratory illnesses during the 2008 games were found to be significantly less in certain populations compared to previous years and this was hypothesized to be related to the reduction of vehicles on the road (Wang et al., 2009; Jentes et al., 2010).
Minutes Americans Walk per Day Source: National Household Travel Survey, 2001, USDOT
Figure Minutes Americans Walk per Day shows the average time Americans spend walking a day. People who walk to and from public transit get an fair amount of physical activity related to using transit, thus the name given to modes of transit that do not involve driving: active transit. Those people who did not own a car or were not a primary driver had higher walking times (Besser & Dannenberg, 2005).
Water Quality
Increasing numbers of roads and parking lots are needed to support an automobile transportation system, which lead to increased non-point source water pollution and contamination of water supplies (road runoff of oil/gas, metals, nutrients, organic waste, to name a few) with possible impacts on human health. Increased erosion and stream siltation causes environmental damage and may affect water treatment plants and thus affect water quality.
Social Capital
On the social sustainability side, we can look at social capital otherwise defined as the “connectedness” of a group built through behaviors such as social networking and civic engagement, along with attitudes such as trust and reciprocity. Greater social capital has been associated with healthier behaviors, better self-rated health, and less negative results such as heart disease. However, social capital has been diminishing over time. Proposed causes include long commute times, observed in sprawling metropolitan areas. Past research suggests that long commute times are associated with less civic participation; Robert Putnam suggests that every ten additional minutes of commuting predicts a 10% decline in social capital (Besser,
most long commutes.
As of 2011, according to an article in the Chicago Tribune, Chicago commuting times are some of the worst — with Chicagoans spending 70 hours per year more on the road than they would if there was no congestion —up from 18 hours in 1982. They have an average commute time of 34 minutes each way. These drivers also use 52 more gallons per year per commuter, increasing their costs and pollution.
Residents of sprawling counties were likely to walk less during leisure time, weigh more, and have greater prevalence of hypertension than residents of compact counties (Ewing, Schmid, Killingsworth, Zlot, & Raudenbush, 2003).
While more compact development is found to have a negative impact on weight, we also find that individuals with low BMI are more likely to select
locations with dense development. This suggests that efforts to curb sprawl, and thereby make communities more exercise-friendly, may simply attract those individuals who are predisposed to physical activity (Plantinga & Bernell, 2007).
Impacts of Climate Change
Public health studies have been conducted with regard to many of the predicted environmental effects of climate change. Thus, it is somewhat easier to examine the public health implications of this outcome of unsustainable behavior. Figure How Climate Change Affects Population describes the pathways by which climate change affects public health. To the left we see the natural and anthropogenic, or human-caused activities that affect climate change, which result in climatic conditions and variability; if we can mitigate those events we can reduce climate change. These activities first result in environmental impacts such as severe weather events, disturbed ecosystems, sea-level rise, and overall environmental degradation. Those impacts can then result in a broad range of health effects that we can adapt to, to a certain extent. These impacts are generally categorized into three areas: heat induced morbidity and mortality, infectious diseases, and impacts due to the effect of extreme weather such as flooding and drought on the social welfare of the population.
Health effects
Greenhouse gas emissions due ta hurnan activity
Environmental effects
Thermal stress: deaths, illness Extreme weather (asthma, allergies) events Injury/death from floods, storms, “frequency cyclones, bushfires “severity Effect of these events onfood yields
"geography
Microbial proliferation:
Changes in Food poisoning—Salmonetia spp, frequency etc; unsafe drinking water intensity, and
Climate phate Effects on ecosystems;
change “temperature : Changes in vector-pathogen-host “precipitation Lela peel on relations and in infectious disease humidity p P geography/seasonality - e.g. «wind patterns Malaria dengue, tickborne viral
disease, schistosomiasis
Sea-level rise: Salination of coastal land and freshwater; storm surges
Impaired crop, livestock and fisheries yields, leading to impaired nutrition, health, survival
Natural climate determinants: terrestrial, solar, planetary, orbital
Environmental degradation: Land, coastal ecosystems, fisheries
Loss of livelihoods, displacement, leading to poverty and adverse health: mental health, infectious diseases, malnutrition, physical risks
How Climate Change Affects Population Diagram summarizing the main pathways by which climate change affects population health. Source:Created by Cindy Klein-Banai, based on McMichael et al.,
2006
Measurement of health effects from climate change can only be very approximate. One major study, by the World Health Organization (WHO), was a quantitative assessment of some of the possible health impacts that looked at the effects of the climate changes since the mid-1970s and determined that this may have resulted in over 150,000 deaths in 2000. The study concluded that the effects will probably grow in the future (World Health Organization, 2009).
Extreme Weather
Climate change can influence heat-related morbidity and mortality, generally a result of the difference between temperature extremes and mean climate in a given area. Higher temperatures in the summer increase mortality. Studies on the effects of heat waves in Europe indicate that half of the excess heat during the European heat wave of 2003 was due to global warming and, by inference, about half of the excess deaths during that heat wave could be attributed to human-generated greenhouse gas emissions (see & Nadelhoffer, 2007; McMichael, 2006). Urban centers are more susceptible due to the urban heat island effect that produces higher temperatures in urban areas as compared to the near-by suburbs and rural areas. Lack of vegetation or evaporation, and large areas of pavement, in cities result in an “Urban Heat Island,” where urban areas are warmer than the neighboring suburban and rural areas (See Figure Sketch of an Urban Heat-Island Profile). Adaptation can help reduce mortality through greater prevention awareness and by providing more air-conditioning and cooling centers.
wo ao
Commercial
~ Suburban Residential
co ol :
® — = — 13°) = ® a 5 — jong °o =] 4 a ® ons = <x @ — oO J)
Sketch of an Urban Heat-Island Profile. Source: Heat Island Group.
The reduction of extreme cold due to global warming, could reduce the number of deaths due to low temperatures. Unlike for heat, those deaths are usually not directly related to the cold temperature itself but rather to influenza. Also, deaths related to cold spells would increase to a lesser extent by (1.6%), while heat waves increase them by 5.7%.
Since volatile organic compounds are precursors of ozone, and VOC emissions increase with temperature, this could lead to an increase in ozone concentrations. For fifteen cities in the eastern United States, the average number of days exceeding the health-based eight-hour ozone standard is projected to increase by 60 percent (from twelve to almost twenty days each summer) by the 2050s because of warmer temperatures (Lashof, & Patz, 2004). Pollen levels may increase with increased CO; levels since that promotes growth and reproduction in plants. This will increase the incidence of allergic reactions. Similarly, poison ivy will grow more and be more toxic.
Infectious diseases are influenced by climate as pathogen survival rates are strongly affected by temperature change. Diseases carried by birds, animals, and insects (vector-born) — such as malaria, dengue fever, and dengue hemorrhagic fever — may be influenced by temperature as mosquitoes are sensitive to climate conditions such as temperature humidity, solar radiation, and rainfall. For example, there has been a strengthening of the relationship between the El Nino global weather cycle and cholera outbreaks in Bangladesh. Increases in malaria in the highlands of eastern Africa may be associated with local warming trends. Temperature also affects the rate of food-born infectious disease. In general, however, it is hard to isolate the effects of climate change that affect the transmission rate and geographic boundaries of infectious disease from other social, economic, behavioral, and environmental factors (see McMichael et al., 2006). Increased precipitation from extreme rainfall events can cause flooding which, especially in cities with combined sewer and stormwater systems can be contaminated by sewage lines. This can happen when the
deep tunnels that carry stormwater in Chicago reach capacity and untreated sewage then must be released into Lake Michigan. E. Coli levels in the lake then increase, forcing beaches to close to prevent the spread of infection.
Diseases are re-emerging and emerging infectious due to intensified food production in “factory” farms. Examples include mad cow disease (1980s in Britain); the encroachment on rain forest by pig farmers exposed pigs and farmers to the “Nipah” virus carried by rainforest bats that were seeking food from orchards around the pig farms — driven by deforestation and the drought of El Nino. This caused infection of pigs which lead to human illness and more than one hundred deaths. Poultry farming (avian influenza viruses) - crowded ‘factory farming’ may increase the likelihood of viral virulence when there is no selective advantage in keeping the host bird alive. Other food related issues are discussed in the next section.
Food Production
Climate change can influence regional famines because droughts and other extreme climate conditions have a direct influence on food crops and also by changing the ecology of plant pathogens (Patz et al., 2005).
There are likely to be major effects of climate change on agricultural production and fisheries. This can be both positive and negative depending on the direct effects of temperature, precipitation, CO>, extreme climate variations, and sea-level rise. Indirect effects would have to do with changes in soil quality, incidence of plant diseases and weed and insect populations. Food spoilage will increase with more heat and humidity. Persistent drought has already reduced food production in Africa. There could be reduction in nutritional quality due to a reduction in the amount of nitrogen crops incorporate when CO> levels increase.
Malnutrition will be increased due to drought, particularly poorer countries. Increasing fuel costs also increase the cost of food, as we are already seeing in 2011. Again, this incremental cost rise affects those who already spend a large portion of their income on food and can contribute to malnutrition.
About one-third, or 1.7 billion, of all people live in water-stressed countries
and this is anticipated to increase to five billion by 2025. Frequency of diarrhea and other diseases like conjunctivitis that are associated with poor hygiene and a breakdown in sanitation may increase.
Lower Emissions @ Higher Emissions
Avg No. of Yrs per Decade with EHW-like Summers
1980 2000 2020 2040 2060 2080
Projection for Future EHW-like Summers in Chicago. The average number of summers per decade with mortality rates projected to equal those of the Chicago analog to the European Heat Wave of 2003. Values shown are the average of three climate models for higher (orange) and lower (yellow) emission scenarios for each decade from 1980 to 2090 Source: Hellmann et al., 2007.
Various studies suggest that increases in population at risk from malnutrition will increase from 40-300 million people over the current 640 million by 2060 (Rosenzweig, Parry, Fischer & Frohberg, 1993). A more recent study said that today 34% of the population is at risk and by 2050 this value would grow to 64-72%. Climate change is associated with decreased pH (acidification) of oceans due to higher CO, levels. Over the past 200 years ocean pH has been reduced by 0.1 units and the IPCC predicts a drop of 0.14 to 0.35 units by 2100. This may affect shell-forming organisms and the species that depend on them. There could be a reduction in plankton due to the North Atlantic Gulf Stream (Pauly & Alder, 2005). With already overexploited fish populations, it will be harder for them to recover.
Natural disasters like floods, droughts, wildfires, tsunamis, and extreme storms have resulted in millions of deaths over the past 25 years and negatively affected the lives of many more. Survivors may experience increased rates of mental health disorders such as post-traumatic stress disorder. Wildfires reduce air quality, increasing particulate matter that provokes cardiac and respiratory problems. Sea level rise will increase flooding and coastal erosion. Indirect effects of rising sea levels include the infiltration of salt water and could interfere with stormwater drainage and sewage disposal. This could force coastal communities to migrate and create refugees with health burdens such as overcrowding, homelessness, and competition for resources. Air pollution is likely to be worse with climate change. It can also lead to mobilization of dangerous chemicals from storage or remobilize chemicals that are already in the environment.
Specific regional effects have may be more severe. Vulnerable regions include temperate zones predicted to experience disproportionate warming, areas around the Pacific and Indian Oceans that are currently subject to variability in rainfall, and large cities where they experience the urban heat island effect (Patz et al., 2005). The Chicago area is one urban area where analysis has been performed to determine the specific health effects that are projected due to climate change (see Figure Projection for Future EHW- like Summers in Chicago). Those effects are similar to the ones described above.
An evaluation of the reductions in adverse health effects that could be achieved by 2020 in four major cities with a total population of 45 million found that GHG mitigation would “reduce particulate matter and ozone ambient concentrations by about 10% and avoid some 64,000 premature deaths, 65,000 person-chronic bronchitis case, and 37 million days of restricted activities (Cifuentes, Borja-Aburto, Gouveia, Thurston & Davis, 2001). The cities’ ozone levels are estimated to increase under predicted future climatic conditions, and this effect will be more extreme in cities that already suffer from high pollution. The estimates of elevated ozone levels could mean a 0.11% to 0.27% increase in daily total mortality (Bell et al., 2007). Therefore, reduction of GHG emissions, along with actions to mitigate the effects of climate change are likely to reduce the public health outcomes associated with climate change.
Conclusions
The implications of climate change on public health are broad and vast. The interconnectedness of all of earth’s systems and human health is an area that is a challenge to study; the climate change scenarios are variable. Public health is directly tied to the human ecosystem that we create through our unsustainable activities. The deterioration of public health on this planet is perhaps the most important consequence of our own unsustainable choices. Without good public health outcomes, human life on this planet is threatened and ultimately our actions could cause significant changes in human health, well-being and longevity. It is not the earth that is at stake - it is humanity.
Review Questions
Exercise:
Problem:
Think about the major sources of energy: coal, nuclear and petroleum. Name some health effects that are associated with each, as portrayed in recent world events. Find one popular and one scientific source to support this.
Exercise:
Problem: Describe three health impacts of climate change. Exercise: Problem: Modern farming practices are meant to increase productivity and feed
the world solving the problems of malnutrition and starvation. How would you argue for or against this?
Exercise: Problem:
What are some outcomes that could be measured to determine if a community is healthy?
Resources
Health Impacts of Climate Change — Society of Occupational and Environmental Health http://www. youtube.com/watch?v=aLfhwaS677c
References
Bell, M. L., Goldberg, R., Hogrefe, C., Kinney, P. L., Knowlton, K., Lynn, B.,... Patz, J. A. (2007). Climate change, ambient ozone, and health in 50 US cities. Climatic Change, 82, 61-76.
Besser L. M., & Dannenberg A. L. (2005, November). Walking to public transit steps to help meet physical activity recommendations. American Journal of Preventive Medicine, 29(4), 273-280.
Besser, L. M., Marcus, M., & Frumkin, H. (2008, March). Commute time and social capital in the U.S. American Journal of Preventive Medicine, 34(3), 207-211.
Blair S. N., Kampert, J. B., Kohl III, H. W., Barlow, C. E., Macera, C. A., Paffenbarger, Jr, R. S., & Gibbons, L. W. (1996). Influences of cardiorespiratory fitness and other precursors on cardiovascular disease and all-cause mortality in men and women. Journal of American Medical Association, 276(3), 205-210.
Cifuentes, L., Borja-Aburto, V. H., Gouveia, N., Thurston, G., & Davis, D. L. (2001). Hidden health benefits of greenhouse gas mitigation. Science, 293(5533), 1257-1259.
Ewing, R., Schmid, T., Killingsworth, R., Zlot, A., & Raudenbush, S. (2003, September/October). Relationship between urban sprawl and physical activity, obesity, and morbidity. American Journal of Health Promotion, 18(1), 49-57.
Friedman, M. S., Powell, K. E., Hutwagner, L., Graham, L. M., & Teague, W. G. (2001). Impact of changes in transportation and commuting behaviors during the 1996 Summer Olympic Games in Atlanta on air quality and childhood asthma. JAMA: The Journal of the American Medical Association, 285(7), 897-905.
Haines, A., Kovats, R. S., Campbell-Lendrum, D., & Corvalan, C. (2006). Climate change and human health: Impacts, vulnerability and public health. Journal of the Royal Institute of Public Health. 120, 585-596.
Hellmann, J., Lesht, B., & Nadelhoffer, K. (2007). Chapter Four — Health. In Climate Change and Chicago: Projections and Potential Impacts. Retrieved from http://www.chicagoclimateaction.org/filebin/pdf/report/Chicago climate i
Jentes, E. S., Davis, X. M., MacDonald, S., Snyman, P. J., Nelson, H., Quarry, D., ... & Marano, N. (2010). Health risks and travel preparation among foreign visitors and expatriates during the 2008 Beijing Olympic and Paralympic Games. American Journal of Tropical Medical Hygene, 82, 466-472.
Lashof, D. A., & Patz, J. (2004). Heat advisory: How global warming causes more bad air days. Retrieved from http://www.nrdc.org/globalwarming/heatadvisory/heatadvisory.pdf.
McMichael, A. J. (2006) Population health as the ‘bottom-line’ of sustainability: A contemporary challenge for public health researchers. European Journal of Public Health, 16(6), 579-582.
McMichael, A. J., Woodruff, R. E., & Hales, S. (2006). Climate change and human health: Present and future risks. Lancet, 367, 859-869.
Patz, J. A., Campbell-Lendrum, D., Holloway, T., & Foley, J. A. (2005). Impact of regional climate change on human health. Nature, 438, 310-317.
Pauly, D., & Alder, J. (2005). Marine Fisheries Systems. In R. Hassan, R. Scholes, & N. Ash (eds.), Ecosystems and Human Well - being: Current State and Trends . (Vol. 1). Washington, D.C., Island Press.
Plantinga, A. J., & Bernell, S. (2007). The association between urban sprawl and obesity: Is it a two-way street?, Journal of Regional Science, 47(5), 857-879.
Rosenzweig, C., Parry, M. L., Fischer, G., & Frohberg, K. (1993). Climate change and world food supply. Research Report No. 3. Oxford, U.K. : Oxford University, Environmental Change Unit.
Wang, X., Westerdahl, D., Chen, L., Wu, Y., Hao, J., Pan, X., Guo, X., & Zhang, K. M. (2009). Evaluating the air quality impacts of the 2008 Beijing Olympic Games: On-road emission factors and black carbon profiles. Atmospheric Environment, 43, 4535-4543.
Wei, M., Kampert, J. B. , Barlow, C. E. , Nichaman, M. Z. , Gibbons, L. W., Paffenbarger, Jr., R. S., & Blair, S. N. (1999). Relationship between low cardiorespiratory fitness and mortality in normal-weight, overweight, and obese men. Journal of the American Medical Association, 282(16), 1547- 1553,
World Health Organization. (2009). Climate change and human health. Fact sheet, July 2005. Retrieved from http://www.who.int/globalchange/news/fsclimandhealth/en/index.html.
Glossary
morbidity The relative frequency of occurrence of a disease.
mortality The number of deaths that occur at a specific time, in a specific group, or from a specific cause.
post-traumatic stress disorder PTSD - a psychological condition affecting people who have suffered severe emotional trauma as a result of an experience such as combat, crime, or natural disaster, and causing sleep disturbances, flashbacks, anxiety, tiredness, and depression.
volatile organic compounds (VOC - an organic compound that evaporates at a relatively low temperature and contributes to air pollution, e.g. ethylene, propylene, benzene, or styrene).
urban sprawl Any environment characterized by (1) a population widely dispersed in low density residential development; (2) rigid separation of homes, shops, and workplaces; (3) a lack of distinct, thriving activity centers, such as strong downtowns or suburban town centers; and (4) a network of roads marked by large block size and poor access from one place to another) has been found to correlate with increased body mass index.
Climate and Global Change — Chapter Introduction In this module, the Chapter Climate and Global Change is introduced, previewing the content of the modules included in the chapter.
Module by: Jonathan Tomkin
The Earth’s climate is changing. The scientific consensus is that by altering the composition of the atmosphere humans are increasing the average temperature of the Earth’s surface. This process has already begun — the planet is measurably warmer than it was at the start of the last century — but scientists predict the change that will occur over the 21st century will be even greater. This increase will have unpredictable impacts on weather patterns around the globe. We are all experiencing climate change. Our descendants will likely experience far more.
This chapter focuses on the science of climate change. We recognize that climate change can be a controversial subject, and that prescriptions for solutions quickly take on a political character, which can raise suspicions of bias. Some argue that the climate is too complicated to predict, and others suggest that natural variations can explain the observed changes in the climate.
These objections have some merit. It should be no surprise that the Earth’s climate is a complicated subject. First, the atmosphere is vast: it extends over 600 km (370 miles) above the ground, and it weighs over five quadrillion tons (that’s a five followed by 15 zeros). Second, the atmosphere is a dynamic system, creating blizzards, hurricanes, thunderstorms, and all the other weather we experience. And it is true that this dynamic system is largely controlled by natural processes — the Earth’s climate has been changing continually since the atmosphere was produced.
And yet scientists can still confidently say that humans are responsible for the current warming. We can do this because this complicated system obeys underlying principles. In the modules Climate Processes; External and Internal Controls and Milankovitch Cycles and the Climate of the Quaternary, we will describe how these principles work, and how they have been observed by scientists. We can then use these principles to understand how, by producing greenhouse gases, humans are altering the
physical properties of the atmosphere in such a way as to increase its ability to retain heat.
In the module Modern Climate Change we show how this theoretical prediction of a warming world is borne out by ever stronger evidence. Temperatures have been measured, and are shown to be increasing. These increases in temperatures are significant and have observable effects on the world: glaciers are shrinking, sea ice is retreating, sea levels are rising — even cherry blossoms are blooming earlier in the year.
In the module Climate Projections, we describe how we can attempt to predict the climate of the future. This is a doubly difficult problem, as it involves not only physics, but, harder yet, people. What will today’s societies do with the foreknowledge of the consequences of our actions? The climate has become yet another natural system whose immediate fate is connected to our own. The reader may find it either reassuring or frightening that we hold the climate’s future in our hands.
Climate Processes; External and Internal Controls In this module, you will explore the processes that control the climate.
Learning Objectives After reading this module, students should be able to
e define both "climate" and "weather" and explain how the two are related
e use the Celsius temperature scale to describe climate and weather
e discuss the role and mechanisms of the major controls on Earth's climate using the concepts of insolation, albedo and greenhouse gases
e identify and describe the mechanisms by which major external and internal changes to the climate (including solar output variation, volcanoes, biological processes, changes in glacial coverage, and meteorite impacts) operate
e know that the Earth's climate has changed greatly over its history as a result of changes in insolation, albedo, and atmospheric composition
e describe the processes that can lead to a "Snowball Earth" using the "positive feedback" concept, and be able to contrast the climate factors that influenced this period of Earth's history with others, including the dominant factors that operated during the Cretaceous
e state the major ways in which carbon dioxide is both added to and removed from the atmosphere, and be able to describe why levels of carbon dioxide and other greenhouse gases can be kept in balance
Introduction
The Earth's climate is continually changing. If we are to understand the current climate and predict the climate of the future, we need to be able to account for the processes that control the climate. One hundred million years ago, much of North America was arid and hot, with giant sand dunes common across the continent's interior. Six hundred and fifty million years ago it appears that the same land mass—along with the rest of the globe— was covered in a layer of snow and ice. What drives these enormous changes through Earth's history? If we understand these fundamental processes we can explain why the climate of today may also change.
In discussing climate in this chapter, we will be using degrees Celsius (°C) as the unit of temperature measurement.
A Thermometer This
thermometer shows how the two scales compare for typical atmospheric temperatures. A change of one degree Celsius (1 °C) is equivalent to a change of one and four fifths degrees Fahrenheit (1.8 °F). Source: Michiel1972 at nl.wikipedia.
The Celsius scale is the standard international unit for temperature that scientists use when discussing the climate. In the Celsius scale, water
freezes at 0 °C and boils at 100 °C. A comfortable room might be heated to 20 °C (which is equivalent to 68 °F). Temperatures can be converted from the Celsius scale to the Fahrenheit scale with the following equation: Equation:
9 f= 5 Ot 82
Weather describes the short term state of the atmosphere. This includes such conditions as wind, air pressure, precipitation, humidity and temperature. Climate describes the typical, or average, atmospheric conditions. Weather and climate are different as the short term state is always changing but the long-term average is not. On The 1° of January, 2011, Chicago recorded a high temperature of 6 °C; this is a measure of the weather. Measurements of climate include the averages of the daily, monthly, and yearly weather patterns, the seasons, and even a description of how often extraordinary events, such as hurricanes, occur. So if we consider the average Chicago high temperature for the 1%‘ of January (a colder 0.5 °C) or the average high temperature for the entire year (a warmer 14.5 °C) we are comparing the city's weather with its climate. The climate is the average of the weather.
Insolation, Albedo and Greenhouse Gases
What controls the climate? The average temperature of the Earth is about 15 °C (which is the yearly average temperature for the city of San Francisco), so most of the Earth's water is in a liquid state. The average temperature of Mars is about -55 °C (about the same as the average winter temperature of the South Pole), so all of the water on the Martian surface is frozen. This is a big difference! One reason Earth is so much hotter than Mars is that Earth is closer to the Sun. Mars receives less than half as much energy from the Sun per unit area as Earth does. This difference in insolation, which is the measure of the amount of solar radiation falling on a surface, is a very important factor in determining the climate of the Earth.
On Earth, we notice the effects of varying insolation on our climate. Sunlight falls most directly on the equator, and only obliquely (at an angle) on the poles. This means that the sunlight is more concentrated at the equator. As shown in Figure Insolation Angle, the same amount of sunlight covers twice as much area when it strikes a surface at an angle of 30° compared to when it strikes a surface directly: the same energy is spread more thinly, weakening its ability to warm the Earth.
1 mile
X mile
\ 30 degrees
'1 mile
2 miles
Insolation Angle Insolation is the effect of incidence angle on sunlight intensity. Note that the same amount
of sunlight is spread out over twice
the area when it strikes the surface at a 30-degree angle. Source: Wikipedia
As a consequence, the tropics receive about twice the insolation as the area inside the Arctic Circle — see Figure Insolation Comparison. This difference in energy explains why the equator has a hot climate and the poles have a cold climate. Differences in insolation also explain the existence of seasons. The Earth's axis is tilted at 23° compared to its orbit, and so over the course of the year each hemisphere alternates between directly facing the Sun and obliquely facing the Sun. When the Northern
hemisphere is most directly facing the Sun (the months of May, June and July) insolation is thus higher, and the climate is warmer. This variation in insolation explains why summer and winter occur (we get less energy from the Sun in winter then we do in summer), and why the timing of the seasons is opposite in the Southern and Northern hemispheres.
Polar Insolation
Equatorial Insolation
Insolation Comparison A cartoon of how latitude is important in determining the amount of insolation. The same amount of sunlight (yellow bars) is spread out over twice the planet's surface area when the rays strike the Earth at an angle (compare the length of the dark lines at the equator and at the poles). Source: Jonathan H. Tomkin.
Figure Insolation shows both the equatorial and seasonal impacts of insolation. High levels of insolation are shown in warm colors (red and pink) and low levels of insolation are shown in cold colors (blue). Notice that in January (top map) the maximum levels of insolation are in the Southern Hemisphere, as this is when the Southern Hemisphere is most directly facing the sun. The Arctic receives very little insolation at this time
of year, as it experiences its long polar night. The reverse is true in April (bottom map).
April 1984-1993
Solar Insolation (kWnh/m2/day)
Insolation Average insolation over ten years for the months of January (top) and April (bottom). Source: Roberta DiPasquale, Surface Meteorology and Solar Energy and the ISCCP Project. Courtesy of NASA's Earth Observatory.
The equator always receives plenty of sunlight, however, and has a much higher average temperature as a consequence; compare the average temperature of the equator with that of the poles in Figure Annual Mean Temperature
-50 -40 -30 -20 -10 0 10 20 30 Annual Mean Temperature
Annual Mean Temperature The Earth's average annual temperature. Source: Robert A. Rohde for Global Warming Art.
The level of insolation affecting Earth depends on the amount of light (or solar radiation) emitted by the Sun. Over the current geologic period, this is very slowly changing—solar radiation is increasing at a rate of around 10% every billion years. This change is much too slow to be noticeable to humans. The sun also goes through an 11-year solar cycle, in which the amount of solar radiation increases and decreases. At the solar cycle peak, the total solar radiation is about 0.1% higher than it is at the trough.
The Earth's orbit is not perfectly circular, so sometimes the Earth is closer to or further from the Sun than it is on average. This also changes the amount of insolation, as the closer the Earth is to the Sun the more concentrated the solar radiation. As we shall see in the next section, these
orbital variations have made a big difference in conditions on the Earth during the period in which humans have inhabited it.
In addition to considering how much energy enters the Earth system via insolation, we also need to consider how much energy leaves. The climate of the Earth is controlled by the Earth's energy balance, which is the movement of energy into and out of the Earth system. Energy flows into the Earth from the Sun and flows out when it is radiated into space. The Earth's energy balance is determined by the amount of sunlight that shines on the Earth (the insolation) and the characteristics of the Earth's surface and atmosphere that act to reflect, circulate and re-radiate this energy. The more energy in the system the higher the temperature, so either increasing the amount of energy arriving or decreasing the rate at which it leaves would make the climate hotter.
One way to change how quickly energy exits the Earth system is to change the reflectivity of the surface. Compare the difference in dark surface of tilled soil (Figure Reflectivity of Earth's Surface (a)) with the blinding brightness of snow-covered ice (Figure Reflectivity of Earth's Surface
(b)).
Reflectivity of Earth's Surface
Tilled soil. Source: Tim Hallam.
The snow surface at Dome C Station, Antarctica Source: Stephen Hudson
The dark soil is absorbing the sun's rays and in so doing is heating the Earth surface, while the brilliant snow is reflecting the sunlight back into space. Albedo is a measure of how reflective a surface is. The higher the albedo the more reflective the material: a perfectly black surface has zero albedo, while a perfectly white surface has an albedo of 1 - it reflects 100% of the incident light. If a planet has a high albedo, much of the radiation from the Sun is reflected back into space, lowering the average temperature. Today, Earth has an average albedo of just over 30%, but this value depends on how much cloud cover there is and what covers the surface. Covering soil with grass increases the amount of light reflected from 17% to 25%, while adding a layer of fresh snow can increase the amount reflected to over 80%. Figure Surface of Earth with Cloud Cover Removed is a composite photograph of the Earth with the cloud cover removed. As you can see,
forests and oceans are dark (low albedo) while snow and deserts are bright (high albedo).
SN nit aa
Surface of Earth with Cloud Cover Removed The surface of the Earth with cloud cover removed. The poles and deserts are much brighter than the oceans and forests. Source: NASA Goddard Space Flight Center Image by Reto St6ckli. Courtesy of NASA's Earth Observatory.
Changes in albedo can create a positive feedback that reinforces a change in the climate. A positive feedback is a process which amplifies the effect of an initial change. If the climate cools, (the initial change), snow covers more of the surface of the land, and sea-ice covers more of the oceans. Because snow has a higher albedo than bare ground, and ice has a higher albedo than water, this initial cooling increases the amount of sunlight that is reflected back into space, cooling the Earth further (the amplification, or positive feedback). Compare the brightness of Figure Surface of Earth with Cloud Cover Removed with a similar photo montage from February (Figure Surface of the Earth in February with Cloud Cover Removed): the extra snow has increased the Earth's albedo. Imagine what would happen if the Earth produced even more snow and ice as a result of this further cooling. The Earth would then reflect more sunlight into space, cooling the planet further and producing yet more snow. If such a loop continued for long enough, this process could result in the entire Earth being covered in ice! Such a feedback loop is known as the Snowball Earth hypothesis, and scientists have found much supporting geological evidence. The most recent period in Earth's history when this could have occurred was around 650 Million years ago. Positive feedbacks are often described as "runaway" processes; once they are begun they continue without stopping.
Surface of the Earth in February with Cloud Cover Removed This image shows the surface of the Earth in February (the Northern Hemisphere winter) with cloud
cover removed. The seasonal snow cover is brighter (and so has a higher albedo) than the land surface it covers. Source: NASA Goddard Space Flight Center Image by Reto St6ckli. Courtesy of NASA's Earth Observatory
Albedo does not explain everything, however. The Earth and the Moon both receive the same amount of insolation. Although the Moon is only slightly more reflective than the Earth, it is much colder. The average temperature on Earth is 15 °C, while the Moon's average temperature is -23 °C. Why the difference? A planet's energy balance is also regulated by its atmosphere. A thick atmosphere can act to trap the energy from sunlight, preventing it from escaping directly into space. Earth has an atmosphere while the Moon does not. If the Earth did not have an atmosphere, it would have an average temperature of -18 °C; slightly warmer than the Moon since it has a lower albedo.
How does the atmosphere trap the energy from the Sun? Shouldn't the Earth's atmosphere reflect as much incoming radiation as it traps? It is true the atmosphere reflects incoming solar radiation—in fact, only around half the insolation that strikes the top of the atmosphere reaches the Earth's surface. The reason an atmosphere generally acts to warm a planet is that the nature of light radiation changes as it reaches the planet's surface. Atmospheres trap more light than they reflect.
Humans see the Earth's atmosphere as largely transparent; that is, we can see a long way in air. This is because we see light in the visible spectrum, which is the light radiation in the range of wavelengths the human eye is able to perceive, and visible light is able to travel a long way through the Earth's atmosphere before it is absorbed. Light is also transmitted in wavelengths we can't see, such as in the infrared spectrum, which is sometimes referred to as infrared light, heat, or thermal radiation. Compared to visible light, infrared light cannot travel very far in the Earth's atmosphere before it is absorbed. Solar radiation striking the Earth is largely
in the visible part of the spectrum. The surface of the Earth absorbs this energy and re-radiates it largely in the infrared part of the spectrum. This means that solar radiation enters the Earth in the form of visible light, unhindered, but tries to leave in the form of infrared light, which is trapped. Thicker atmospheres keep this infrared radiation trapped for longer, and so warm the Earth—just like an extra blanket makes you warmer in bed.
This effect is shown in Figure Earth Atmosphere Cartoon. The visible light radiation enters the atmosphere, and quickly exits as infrared radiation if there is no atmosphere (top Earth). With our atmosphere (the middle Earth), visible light enters unhindered but the infrared light is partially reflected back to the surface, increasing the amount of energy and thus the temperature at the Earth's surface. If the atmosphere is made thicker (bottom Earth) the infrared radiation is trapped for longer, further warming the planet's surface.
No Atmosphere
Standard Atmosphere
Thickened Atmosphere
Earth Atmosphere Cartoon A cartoon of the greenhouse effect.
(Top) Visible light radiation emitted by the sun (yellow arrows) strikes the Earth and reflects as infrared radiation (orange arrow); (middle) an atmosphere reflects some of the infrared radiation back toward the planet; (bottom) a thickened atmosphere reflects greater amounts of infrared radiation. Source: Jonathan H. Tomkin.
The way the atmosphere acts to trap light radiation is referred to as the greenhouse effect, and the gases that prevent the thermal radiation from exiting the Earth system are described as greenhouse gases. The four most important greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, methane, and ozone. All four are found naturally in the Earth's atmosphere. As we will discuss in Section 4.4, however, human activities are adding to the natural amount of carbon dioxide and methane, and even adding new greenhouse gases, such as chlorofluorocarbon (CFC).
Earth's Changing Atmosphere
The composition of Earth's atmosphere has changed over geologic time. The atmosphere has largely come from volcanic venting of gas from Earth's interior (see Figure Volcanic Outgassing), but biology has also made important changes by producing oxygen and removing carbon dioxide. Greenhouse gases currently make up only a small fraction of the Earth's atmosphere—99% of air consists of nitrogen and oxygen molecules.
Volcanic Outgassing The Mt. Bromo volcano in Indonesia emitting gas into the atmosphere. Source: Jan-Pieter Nap, taken
on July 11, 2004.
While volcanoes can warm the Earth by adding carbon dioxide to the atmosphere, which produces a greenhouse effect, they can also cool the Earth by injecting ash and sulfur into the atmosphere. These additions raise the albedo of the atmosphere, allowing less sunlight to reach the surface of the Earth. The effect lasts until the particles settle out of the atmosphere, typically within a few years. Volcanic eruptions have impacted human societies throughout history; the Mt. Tambora eruption in 1815 cooled the Earth so much that snow fell during June in New England, and the more recent Mt. Pinatubo eruption in 1991 (see Figure Mt. Pinatubo Explosion) ejected so much sulfuric acid into the atmosphere that global temperatures were lowered by about 0.5 °C in the following year.
Mt. Pinatubo Explosion The 1991 eruption of Mt. Pinatubo. Source: U.S. Geological
Evidence from the geologic past indicates that similar events have caused mass extinctions wherein a significant fraction of all species on Earth were wiped out in a relatively short amount of time. Sustained outgassing from continuous volcanic eruptions is thought to have produced so much ash and aerosols that light sufficient to support photosynthesis in plants was unable to penetrate the atmosphere, causing the food chain to collapse. The ash particles produced by extended eruptions would also have increased the Earth's albedo, making conditions inhospitably cool for plants and animals adapted to a warmer environment.
Asteroid impacts can also cause the climate to suddenly cool. When large asteroids strike the Earth, ash is ejected into the atmosphere, which
increases albedo in the same way as volcanic eruptions. Everyday clouds (made up of water droplets) both cool and warm the Earth. They can cool the Earth by increasing the planet's albedo, reflecting sunlight into space before it reaches the surface. Clouds can also warm the Earth, by reflecting infrared radiation emitted by the surface back towards the planet. Different types of clouds, and different conditions, determine which effect predominates. On a hot summer's day, for example, clouds cool us by shielding us from the sun's rays, but on a winter's night a layer of cloud can act as a warming blanket.
The composition of the Earth's atmosphere is not fixed; greenhouse gases can be added to and removed from the atmosphere over time. For example, carbon dioxide is added by volcanoes and the decay or burning of organic matter. It is removed by photosynthesis in plants, when it is dissolved in the oceans and when carbonate sediments (a type of rock) are produced. Over geologic time, these processes have significantly reduced the proportion of carbon dioxide in the atmosphere. Atmospheric carbon dioxide levels just prior to the industrial revolution are thought to have been only one twentieth of those of 500 million years ago. Natural processes also remove carbon dioxide added by human activity, but only very slowly. It is estimated that it would take the Earth around a thousand years to naturally remove most of the carbon dioxide released by the industrial consumption of fossil fuels up to the present.
Greenhouse gases other than carbon dioxide are shorter-lived: methane is removed from the atmosphere in around a decade, and chlorofluorocarbons break down within a century. Individual water molecules spend only a few days at a time in the atmosphere, but unlike the other greenhouse gases, the total amount of water vapor in the atmosphere remains constant. Water evaporated from the oceans replaces water lost by condensation and precipitation.
Changing the composition of the Earth's atmosphere also changes the climate. Do you remember the Snowball Earth — how increasing ice cover also increased the Earth's albedo, eventually covering the entire planet in ice and snow? Today's climate is temperate—so we must have escaped this frozen trap. But how? The leading hypothesis is that the composition of the
Earth's atmosphere changed, with volcanoes slowly adding more and more carbon dioxide to it. Without access to the oceans, plants, or surface rocks, this carbon dioxide was not removed from the atmosphere and so continued to build up over millions of years. Eventually, the additional warming caused by the increase in greenhouse gases overcame the cooling caused by the snow's high albedo, and temperatures rose enough to melt the ice, freeing the Earth.
For most of Earth's history, carbon dioxide concentrations have been higher than they are today. As a consequence, past climates have often been very warm. During the late stage of the dinosaur era (the Cretaceous, a period that lasted between 65 and 145 million years ago), carbon dioxide levels were about 5 times higher than they are today, and the average global temperatures were more than 10 °C higher than today's. There were no large ice sheets, and dinosaur fossils from this period have been found as far north as Alaska. These animals would not survive the cold conditions found in the arctic today. Further south, fossil crocodiles from 60 million years ago have been found in North Dakota. The modern average winter temperature in North Dakota is around -10 °C —but being cold-blooded, crocodiles are most at home when the air temperature is around 30 °C! The climate was warmer in the past when the amount of carbon dioxide was higher.
Review Questions
Exercise:
Problem:
The text describes how the high albedo of snow acts as a positive feedback—if the Earth is made cooler, the highly reflective snow can act to further cool the Earth. Today, part of the Earth is covered with snow and ice. Can you describe a mechanism by which warmer temperatures would also produce a positive feedback—this time heating the Earth further—through a similar albedo mechanism?
Exercise:
Problem:
Mars is colder than the Earth. Venus, on the other hand, is much hotter, with average surface temperatures of around 450 °C. Venus is closer to the Sun than the Earth is, and so receives about twice as much solar radiation. Venus's atmosphere is also different than Earth's, as it is much thicker and mainly consists of carbon dioxide. Using the terms insolation and greenhouse gases, can you suggest reasons why Venus is so hot?
Exercise:
Problem:
Oxygen makes up over 20% of Earth's atmosphere, while carbon dioxide makes up less than 0.04%. Oxygen is largely transparent to both visible and infrared light. Explain why carbon dioxide is a more important greenhouse gas in the Earth's atmosphere than oxygen, even though there is much more oxygen than carbon dioxide.
Exercise:
Problem:
Figure Insolation shows the insolation at the surface of the Earth. The Earth is spherical, so we would expect the values to be the same for places of the same latitude. But notice that this is not true — compare, for example, central Africa with the Atlantic Ocean at the same latitude. What feature of the atmosphere might explain this variation, and why?
Resources
The National Aeronautical and Space Administration (NASA) Earth Observatory website has an array of climate resources. For a more in-depth discussion of Earth's energy budget, go to http://earthobservatory.nasa.gov/Features/EnergyBalance/
Are you interested in finding more about the controversial Snowball Earth hypothesis? The National Science foundation and Harvard University have set up a website with more about the hypothesis and the evidence. Go to http://www.snowballearth.org/
Glossary
albedo A measure of how reflective a surface is. A perfectly black surface has an albedo of 0, while a perfectly white surface has an albedo of 1.
climate The average of the weather.
cretaceous period The period between 65 and 145 million years ago, which was the final period of Earth's history that included dinosaurs.
greenhouse effect The process by which the atmosphere acts to trap heat, warming the climate.
greenhouse gases Those gases in the atmosphere that warm the climate, most importantly, water vapor, carbon dioxide, methane, and ozone.
infrared spectrum The light radiation just below the range of wavelengths visible to the human eye. Also referred to as thermal radiation.
insolation The measure of the amount of solar radiation falling on a surface.
positive feedback A runaway process which amplifies the effect of an initial change.
snowball earth
A condition in which the entire planet is covered in ice, last thought to have happened 650 million years ago.
solar radiation The energy emitted by the sun in the form of light.
visible spectrum The light radiation that is in the range of wavelengths that is visible to the human eye.
weather A description of the short term state of the atmosphere.
Milankovitch Cycles and the Climate of the Quaternary In this module, we will look at the recent natural changes in Earth’s climate, and we will use these drivers to understand why the climate has changed.
Learning Objectives After reading this module, students should be able to
e describe the changing climate of the Quaternary
e explain why Milankovitch cycles explain the variations of climate over the Quaternary, in terms of the similar periods of orbital variations and glacial cycles
e explain how the glacier/climate system is linked via albedo feedbacks
e describe how sediment and ice cores provide information about past climates
e use the mechanisms that cause stable isotope fractionation to predict the impact of changing climate on stable isotope records
Introduction
In Module Climate Processes; External and Internal Controls we saw the major drivers of the climate—the energy that comes from the Sun (insolation) and the properties of the planet that determine how long that energy stays in the Earth system (albedo, greenhouse gases). In this section, we will look at the recent natural changes in Earth's climate, and we will use these drivers to understand why the climate has changed.
The most recent period of Earth's geologic history—spanning the last 2.6 million years—is known as the Quaternary period. This is an important period for us because it encompasses the entire period over which humans have existed—our species evolved about 200,000 years ago. We will examine how the climate has changed over this period in detail. By understanding recent natural processes of climate change, we will be able to better understand why scientists attribute the currently observed changes in global climate as being the result of human activity.
Quaternary Climate — Information From Ice Cores
How do we know about the Quaternary climate? After all, most of the period predates human existence, and we have only been recording the conditions of climate for a few centuries. Scientists are able to make informed judgments about the climates of the deep past by using proxy data. Proxy data is information about the climate that accumulates through natural phenomena. In the previous module, for example, we discussed how 60-million-year-old crocodile fossils have been found in North Dakota. This gives us indirect information about the climate of the period—that the climate of the region was warmer than it is today. Although not as precise as climate data recorded by instruments (such as thermometers), proxy data has been recovered from a diverse array of natural sources, and provides a surprisingly precise picture of climate change through deep time.
One highly detailed record of past climate conditions has been recovered from the great ice sheets of Greenland and Antarctica. These ice sheets are built by snow falling on the ice surface and being covered by subsequent snowfalls. The compressed snow is transformed into ice. It is so cold in these polar locations that the ice doesn't melt even in the summers, so the ice is able to build up over hundreds of thousands of years. Because the ice at lower depths was produced by progressively earlier snowfalls, the age of the ice increases with depth, and the youngest ice is at the surface. The Antarctic ice sheet is up to three miles thick. It takes a long time to build up this much ice, and the oldest ice found at the bottom of the Antarctica ice sheet is around 800,000 years old.
Scientists drill into these ice sheets to extract ice cores, which record information about past climates. Figure Ice Cores shows what these cores look like when they are cut open. Like tree rings, ice cores indicate years of growth. Note how the middle core (which required over a mile of drilling to extract!) has distinct layers—this is because the seasons leave an imprint in the layers of snow. Scientists can use this imprint to help calculate the age of the ice at different depths, although the task becomes more difficult the deeper the core sample, since the ice layers become more compressed. The ice records several different types of climate information: the temperature
of the core, the properties of the water that make up the ice, trapped dust, and tiny entombed bubbles of ancient atmosphere.
1836-1837 meters
3050-3051 meters
Ice Cores Three different sections of an ice core. The seasonal layers are most clear in the middle section (note the dark and light bands). The deepest section (bottom core) is taken from almost two miles down and is colored brown by rocky debris from the ground under the ice. Source: National Ice Core Laboratory
The water molecules that make up the ice record information about the temperature of the atmosphere. Each water molecule is made up of two hydrogen atoms and one oxygen atom (and so has the chemical name H20). Not all oxygen atoms are the same however; some are "light" and some are "heavy". These different types of oxygen are called isotopes, which are atoms that have same number of protons but different numbers of neutrons. The heavy isotope of oxygen (oxygen-18, or !8O) is more than 10% heavier than the light isotope (oxygen-16 or '°O). This means that some water molecules weigh more than others. This is important because lighter water molecules are more easily evaporated from the ocean, and once in the atmosphere, heavier water molecules are more likely to condense and fall as precipitation. As we can see from Figure Oxygen Schematic, the water in the ice sheets is lighter (has a higher proportion of !°O relative to ‘8O) than the water in the oceans.
The process of differentiation between heavy and light water molecules is temperature dependent. If the atmosphere is warm, there is more energy available to evaporate and hold the heavier !8O water in the atmosphere, so the snow that falls on the polar ice sheets is relatively higher in !®O. When the atmosphere is cold, the amount of energy is less, and so less !®O makes it to the poles to be turned into glacial ice. We can compare the amount of ‘80 in different parts of the ice core to see how the atmosphere's temperature—the climate—has changed.
Near the poles, atmospheric water vapor is increasingly depleted in ""O.
Heavy, "O-ich water condenses over
mid-atitudes. water from glacial
§ depleted in “O
Water, slightly Gepleied in “ov
we evaporates from warm sub-tropical Boters
Oxygen Schematic Water becomes lighter as it travels toward the poles. The heavy (180) water drops out of the atmosphere (as rain or snow) before reaching the ice sheet. This means that the snow that forms the glacial ice is lighter than the ocean water (has more 160 than 180, compared to ocean water). Source: Robert Simmon, NASA GSFC, NASA Earth Observatory
Figure Ice Age Temperature shows what this record looks like over the last 400,000 years. The blue and green lines depict two different Antarctic ice cores (taken from ice about 350 miles apart) and the variations in oxygen isotopes are converted into temperature changes. The y-axis shows
temperature change; today's climate is at zero—the dashed line. Notice that the Earth's climate has not been stable! Sometimes the temperature is higher than it is today—the blue and green lines are higher than the dashed about 120,000 years ago, for example. Most of the time the climate is much colder than today's, however: the most common value is around -6 °C (-13 °F). On average, the earth's temperature between 25,000 and 100,000 years ago was about 6 °C lower than it is today. These changes can be double- checked by measuring the temperature of the ice in the cores directly. Ice that is 30,000 years old is indeed colder than the ice made today, just as the isotope data predicts.
Ice Age Temperature Changes EPICA -
Ww T
awo T
ATemperature (°C) oO
too a Ww
° =
Ice Volume
High? 1 1 L 1 1 1 4 450 400 350 300 250 200 150 100 £50 0 Thousands of Years Ago
Ice Age Temperature The blue and green lines depict two different Antarctic ice cores (taken from ice about 350 miles apart) and the variations in oxygen isotopes are converted into temperature changes. The red line depicts global ice volume. The y-axis shows temperature change; today's climate is at zero — the dashed line. Source: Robert A. Rohde
41 kyr cycle 100 kyr cycle
Five Million Years of Climate Change From Sediment Cores
55 5 45 4 35 Oo «20 2 “h 1 #05 0°
Millions of Years Ago
Equivalent Vostok AT (°C) oOo ® KR © O WN
5'°O Benthic Carbonate (per mil)
Five Myr Climate Change A comparison of the age of sediment (x- axis) and the change in temperature over time (left y-axis) as derived from oxygen isotope ratios (right y-axis). The dashed line shows today's climate. Note that the climate is cooling over the last few million years, but it is highly variable. In the last one million years the climate alternates between warm and cool conditions on a 100,000- year time scale ("100 kyr cycle"), before this it alternated on a 41,000 year cycle. Both these period lengths are the same as Milankovitch cycles. These cores suggest that today's temperature is higher than almost all of that of the Quaternary (the last 2.6 Million years). Source: Jo Weber
The changes in climate recorded in ice sheets are thought to be worldwide. The same climate changes observed in Antarctica are also found in cores taken from Greenland, which is on the other side of the Earth. Isotope data can also be taken from sediment cored from the ocean floor—all over the planet—and these cores also show the same changes in climate, alternating between cold and warm. Because ocean sediment is deposited over millions of years, the sediment can give an indication of the climate across the whole of the Quaternary and beyond. Figure Five Myr Climate Change shows how temperature has changed over time (blue line), compared with today (dashed line). The temperature has, on average, gotten colder over the Quaternary, but it also appears to oscillate between warm and cold periods. We'll investigate these periodic changes in the next section of this chapter.
As falling snow accumulates on the ground, tiny bubbles of air become trapped in it. These bubbles are retained as the snow transforms to ice, and constitute tiny samples of the ancient atmosphere that can be analyzed to find out if the changes in temperature (as recorded in the oxygen isotopes) are related to changes in the atmosphere. The temperature recorded by the isotopes in the ice is directly related to the amount of carbon dioxide in the trapped air (Figure Vostok Petit Data): the times with higher carbon dioxide are also times of high temperature.
Falling snow also captures and entombs atmospheric dust, which is topsoil born aloft by the wind, and which is especially prevalent during droughts. The fact that more dust occurs in the ice accumulated during cold periods suggests that the glacial climate was dry, as well as cold.
i variation (AT) ———
400
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Thousands of years ago
Vostok Petit Data These graphs depict how changes in temperature— inferred from changes in isotope ratios (blue line)--correspond to changes in atmospheric carbon dioxide (green line) and dust (red line) over the last 400,000 years as recorded in an ice core extracted from Antarctica. Carbon dioxide varies directly with temperature — the warmer the climate the higher the carbon dioxide level. Atmospheric dust is highest during the coolest periods (such as 25,000 and 150,000 years ago). Source: William M. Connolley produced figure using_data from the National Oceanic and Atmospheric Administration, U.S.
Data.
Quaternary Climate — Cycling Between Glacials and Interglacials
Ice Age Earth An artist's impression of the Earth during an ice age. Note that the
Northern parts of North America and Europe (including Canada and Scandinavia) are entirely covered by ice-sheets. Source: I[ttiz
During the Quaternary, the Earth has cycled between glacial periods (sometimes referred to as "ice ages") and interglacial periods. The ice was at its most recent extreme around 20,000 years ago in a period known as the Last Glacial Maximum, or LGM. As we can see from the ice core record, the Quaternary climate is usually cold (see Figure Ice Age Temperature), with long periods of cold punctuated with shorter (10,000 year long, or so) periods of warmer conditions, like those we experience today. In many ways, our current climate is exceptional—for most of human existence, the Earth has been a much colder place.
What was the Earth like during these glacial periods? Almost all the world was cold; average temperatures were around 6 °C (-13 °F) colder than today. Such conditions allow ice sheets to grow—much of North America, Asia and Europe were covered under mile-thick ice (see Figure Ice Age Earth). Because this ice was made of water that was once in the oceans, sea levels were much lower. At the LGM, sea level was about 120 meters (or about 400 feet) lower than it is today. As the seas retreated, the continents grew larger, creating land bridges that joined Asia with North America, Britain with Europe, and Australia with Papua New Guinea.
During glacial periods the climate was also much drier, as evidenced by the increase in atmospheric dust (Figure Vostok Petit Data). The lands at and near the poles were covered with ice, and dry grasslands occupied areas where temperate forests occur today. Deserts were much larger than they are now, and tropical rainforests, having less water and less warmth, were small. The animals and plants of glacial periods were different in their distribution than they are today, as they were adapted to these different conditions. Fossils of Mastodons (Figure Knight Mastodon) have been
found from all across what is now the United States, including from Florida, which currently enjoys a subtropical climate.
Knight Mastodon An artist's impression of a Mastodon, an elephant-like mammal with a thick wooly coat. Mastodon fossils dating from past glacial periods have been found across North America—from Florida to Alaska. Source: Charles R. Knight
During glacial periods humans would have been unable to occupy the globe as they do today because all landmasses experienced different climactic conditions. Some countries of the present could not exist, as they would be almost completely covered by ice. As examples, look for Canada, Iceland and The United Kingdom in Figure 800pn Northern Icesheet.
Milankovitch Cycles
Why has the Earth cycled through hot and cold climates throughout the Quatemary? As we learned in the previous module, the Earth's climate is controlled by several different factors—insolation, greenhouse gases, and
albedo are all important. Scientists believe that changes in insolation are responsible for these climate swings, and the insolation varies as a result of wobbles in the Earth's orbit.
The Earth's orbit is not fixed — it changes regularly over time. These periodic changes in Earth's orbit named are referred to as Milankovitch Cycles, and are illustrated in Figure Milankovitch Cycles. Changes in the Earth's orbit alter the pattern of insolation that the Earth receives. There are three principle ways in which the Earth's orbit varies:
1. Eccentricity (or Orbital shape). The Earth's orbit is not perfectly circular, but instead follows an ellipse. This means that the Earth is, through the course of the year, sometimes closer and sometimes further away from the Sun. Currently, the Earth is closest to the Sun in early January, and furthest from the Sun in Early July. This changes the amount of insolation by a few percent, so Northern Hemisphere seasons are slightly milder than they would be if the orbital was circular (cooler summers and warmer winters). The orbital shape changes over time: the Earth moves between being nearly circular and being mildly elliptical. There are two main periods over which this change occurs, one takes around 100,000 years (this is the time over which the orbit goes from being circular, to elliptic, and back to circular), another takes around 400,000 years.
2. Axial Tilt (or Obliquity). The Earth axis spins at an angle to its orbit around the Sun — currently this angle is 23.5 degrees (this angle is known as the axial tilt). This difference in orbit creates the seasons (as each hemisphere takes turns being tilted towards and away from the Sun over the course of the year). If the axis of spin lined up with the direction of the Earth's orbit (so that the tilt angle was zero) there would be no seasons! This axial tilt also changes over time, varying between 22.1 and 24.5 degrees. The larger the angle, the larger the temperature difference between summer and winter. It takes about 41,000 year for the axial tilt to change from one extreme to the other, and back again. Currently, the axial tilt is midway between the two extremes and is decreasing—which will make the seasons weaker (cooler summers and warmer winters) over the next 20,000 years.
3. Axial Precession. The direction of Earth's axis of rotation also changes over time relative to the stars. Currently, the North Pole points towards the star Polaris, but the axis of rotation cycles between pointing to that star and the star Vega. This impacts the Earth's climate as it determines when the seasons occur in Earth's orbit. When the axis is pointing at Vega, the Northern Hemisphere's peak summer is in January, not July. If this were true today, it would mean that the Northern Hemisphere would experience more extreme seasons, because January is when the Earth is closest to the Sun (as discussed above in eccentricity). This cycle takes around 20,000 years to complete.
Milankovitch Cycles
Precession 26,000 years
Eccentricity
100,000 - 413,000 years —
\
ec
\
Tilt 41,000 years
21.5° - 24.5° Currently 23.5°
©The COMET Program
Milankovitch Cycles Illustration of the three variables in Earth's orbit, with periods of variation marked. Source: COMET® at the University Corporation for
Commerce. ©1997-2009 University Corporation for Atmospheric Research. All Rights Reserved.
The three cycles described above have different periods, all of which are long by human standards: 20,000, 40,000, 100,000 and 400,000 years. If we look at the temperature data from ice and sediment cores, we see that these periods are reflected in Earth's climate. In the last million or so years, the 100,000-year eccentricity in the orbit has determined the timing of glaciations, and before that the 40,000-year axial tilt was dominant (Figure Five Myr Climate Change). These cycles have been important for a long time; geologists have even found evidence of these periods in rocks that are hundreds of millions of years old.
But how do the Milankovitch Cycles change our climate? These orbital cycles do not have much impact on the total insolation the Earth receives: they change only the timing of that insolation. Since the total insolation does not change, these orbital variations have the power to make the Earth's seasons stronger or weaker, but the average annual temperature should stay the same. The best explanation for long term changes in average annual temperature is that the Milankovitch cycles initiate a positive feedback that amplifies the small change in insolation.
Insolation and the Albedo Feedback
Today, the Earth's orbit is not very eccentric (it is almost circular), but at the beginning of each of the recent ice age periods, the orbit was much more elliptical. This meant that the Earth was further away from the sun during the northern hemisphere summers, reducing the total insolation. Lower insolation meant that the summer months were milder than they would otherwise be, with cooler temperatures. Summer temperatures were also lower when the Earth's axial tilt was smaller, so the two different orbital parameters could reinforce one another's effects, in this case producing especially mild summers.
It is thought that these mild northern summers produced an albedo feedback that made the whole planet slip into an ice age. The northern hemisphere has continents near the poles—Europe, Asia, and North America. Today, these continents have largely temperate climates. During the winter, snow falls across much of the land (see Figure Surface of the Earth in February with Cloud Cover Removed in the previous module) only to melt during the summer months. If the summers are not hot enough to melt all the snow and ice, glaciers can advance, covering more of the land. Because ice has a high albedo, more sunlight is reflected than before, and the Earth is made cooler. This creates a positive feedback, as the cooler conditions allow the ice to advance further—which, in turn, increases the albedo and cools the Earth! Eventually, a large proportion of the northern continents became covered in ice (Figure 800pn Northern Icesheet).
800pn Northern Icesheet Glacial coverage (light blue) of the northern hemisphere during the ice ages. Source: Hannes Grobe
This positive feedback process works in the other direction, as well. The interglacial periods are ushered in when the orbital parameters create summers that are unusually warm, which melts some of the ice. When the ice sheets shrink, the Earth's albedo decreases, which further warms the system. The giant northern ice sheets shriveled up in a few thousand years as warm summers and decreasing albedo worked together.
These cycles of alternating cooling and warming are also related to changes in the amount of greenhouse gases in the atmosphere. As we observed in Figure Vostok Petit Data, the climate contains higher levels of carbon dioxide during interglacial periods. Although this appears to make sense— carbon dioxide is a greenhouse gas, and so should produce warmer climates —it is also a puzzle, because it is not clear how changes in Milankovitch cycles lead to higher levels of carbon dioxide in the atmosphere. It is clear that these changes in carbon dioxide are important in making the change in temperature between interglacial and glacial periods so extreme. Several different hypotheses have been proposed to explain why glacial periods produce lower levels of carbon dioxide (it may be related to how the physical changes influence the Earth's ecosystems ability to absorb carbon dioxide: perhaps lower sea levels increase the nutrient supply in the ocean, or the drop in sea level destroys coral reefs, or iron-rich dust from new deserts fertilizes the oceans) but further work on this question remains to be done.
It is a concern for all of us that there are gaps in our understanding of how the feedbacks between insolation, albedo and greenhouse gases operate, as it makes it hard to predict what the consequences of any changes in the climate system might lead to. The current level of atmospheric carbon dioxide is unprecedented in human experience; it is at the highest level ever recorded in the Quaternary. Will the current increase in greenhouse gases lead to a positive feedback, warming the Earth even more?
Review Questions
Exercise:
Problem:
In the text, we discuss how polar ice has a smaller !8O to !°O ratio (that is, it has proportionally less heavy isotope water) than ocean water does. Hydrogen also has isotopes, the two most common being hydrogen-1 (‘H) and hydrogen-2 (7H, also known as deuterium). Water is made up of both hydrogen and oxygen, and scientists analyze both elements when examining ice cores. Do you predict that polar ice sheets would have a higher ratio or a lower ratio of 'H to 7H than ocean water? Will colder global temperatures increase or decrease the amount of 7H in polar ice?
Exercise:
Problem:
In the text, we discuss how polar ice has a smaller !8O to !°O ratio (that is, it has proportionally less heavy-isotope water) when the climate is cooler. We also discuss how changes in the ratio of !8O to ‘60 ratio in sediment cores can also be used to determine the climate's average temperature. In ocean sediments, the ratio of 80 to '°O increases when the climate is cooler (that is, it has proportionally more heavy isotope water). Explain why isotope ratios in ocean sediment have the opposite reaction to those in polar ice.
Exercise: Problem: There are three different ways in which the Earth's orbit changes through time. What combination of orbital parameters would be most
likely to start an ice age? (Hint: Ice ages require cool northern summers. )
Resources Do you want to know more about how ice cores are extracted and analyzed?
NASA's Earth Observatory has details about the practical issues of drilling ice cores (deep ice needs to "relax" for as long as a year at the surface
before being cut open — or it can shatter!) and how chemical data is interpreted. Go to http://earthobservatory.nasa.gov/Features/Paleoclimatology_IceCores/ for an in-depth article with great links.
Glossary
axial precession The movement in the axis of rotation, which change in the direction of Earth's axis of rotation relative to the stars.
axial tilt The angle between a planet's axis of rotation and the line perpendicular to the plane in which it orbits. The Earth's current axial tilt is 23.5 degrees.
eccentricity A measure of how much an ellipse departs from circularity.
glacial period A long period of time in which ice -sheets and glaciers are advanced in their extent.
ice sheets Glaciers big enough to cover a continent. Currently, ice sheets are found in Antarctica and Greenland, but during glacial periods, ice sheets have covered other land masses, including North America.
interglacial period The warm periods of the Quaternary in which glaciers and ice-sheets retreat. These occur between the longer glacial periods.
isotopes Atoms that have same number of protons but different numbers of neutrons. This means that they are the same element (e.g. oxygen), have the same chemical properties, but different masses.
last glacial maximum
The time at which ice sheets were at their greatest extent during the latest glacial period.
milankovitch cycles Periodic variations in the Earth's orbit that influence its climate. These cycles are named after Milutin Milankovitch, a mathematician who quantified the theory.
quaternary period The most recent geological period, spanning the time from 2.6 million years ago to today.
obliquity See Axial Tilt.
proxy data Information about the climate that accumulates through natural phenomena.
Modern Climate Change
Recent climate change, which has occurred during the modern instrument era, is the focus of this module. It is through the lens of long-term climate change (occurring on thousands to millions of years) that we will view earth’s current climate and recent climate change. The goal is to investigate how the principles listed above are shaping current climate events
Learning Objectives After reading this module, students should be able to
e assess long-term global temperature records and place recent climate change into the context of historical temperature observations
e explain how changes in the Sun's energy output have impacted the last 1300 years of global temperature records
e analyze the human impact on the planetary albedo and relate these changes to recent climate change
e predict the response of the global average temperature when large volcanic eruptions occur
e explain the enhanced greenhouse effect
e discuss how recent observations of change measured within regional ecosystems are related to global climate change
Introduction
In previous modules, an examination of the geologic record of the earth’s climate in the Quaternary Period revealed the primary drivers of climate change. The most important conclusions to be drawn from the Modules Climate Processes; External and Internal Controls and Milankovitch Cycles and the Climate of the Quaternary are the following:
1. In the past, Earth has been significantly warmer (and mostly ice free) and significantly colder (especially during the so-called “Snowball Earth” eras) than it is today.
2. Climate change occurs when there are changes in insolation, albedo, and composition of the atmosphere.
3. Climate is the average of weather, and changes to the earth’s climate occur on long time scales.
Recent climate change, which has occurred during the modern instrument era, is the focus of this module. It is through the lens of long-term climate change (occurring on thousands to millions of years) that we will view earth’s current climate and recent climate change. The goal is to investigate how the principles listed above are shaping current climate events.
Mechanisms
Temperature Records
Figure Northern Hemisphere Surface Air clearly shows that the current global average temperature reflects an interglacial warm period. If we focus in on the end of this record we can observe some of the fine scale changes in the global temperature records. Figure Northern Hemisphere Surface Air combines proxy data (i.e., information from ice cores and tree rings) with the modern instrument record to create a graph showing the last 1300 years of Northern Hemisphere (hereafter, NH) temperatures. Each line on the top two panels represents a different temperature data set collected in the NH and the bottom panel color codes the percentage of overlap among these data sets.
1750 1800 1850 1900 1950 2000
——__ Unfiltered HadCRUT2v CRUTEM2v
_(a) Instrumental temperatures
Temperature anomaly (°C wrt 1961-1990) ° oO ° Oo
0.5 ——— MBHi999 ———— MJ2003 BOS..2001 B2000 f}0.5 —— JBB..1998 ECS2002 RMO..2005 MSH..2005 ——— +pw2006 ———— HCA.2006 ———— 02005 === PS2004
Instrumental
(HadCRUT2v) nA f MM
2 (=)
Temperature anomaly (°C wrt 1961-1990)
800 1000 1200 1400 1600 1800 2000
Temperature anomaly (°C wrt 1961-1990)
(c) Overlap of reconstructed temperatures
800 1000 1200 1400 1600 1800 2000 Year
Northern Hemisphere Surface Air Panel (a) — Northern Hemisphere surface air temperature data from the modern instrument era from various sources. Panel (b) — Northern
Hemisphere surface air temperature reconstruction dating back 1300 years from various sources. Panel (c) - Percent of overlap between the various sources of Panel (b). Source: Climate Change 2007: The Physical Science Basis: Contribution of Working_Group I
to the Fourth Assessment Report of the Intergovernmental Panel on
Major features in these data include the Medieval Warm Period approximately 1,000 years ago and the Little Ice Age approximately 400 years ago. Even with these events, the bottom panel shows that most of the variability in the NH temperature fits within a 0.5°C temperature range. Rarely has the temperature exceeded the 1961-1990 average, which is the dividing line on this graph. The only major fluctuation outside of this range is during the modern instrument era of the last 300 years, where confidence between the data sets is high. Beginning in the 1800s, the solid black line in each panel traces out approximately a 1°C increase in global temperatures. It is this increase that is the central focus in recent climate change science. Remember from the previous chapter that a 1°C change in the earth’s temperature is a large change; reduce the global average by 4°C to 6°C and much of the NH will be covered with ice as it was 20,000 years ago.
There has been much debate over recent climate change, especially in the news media and among political parties around the world. This debate is centered on the cause of the recent 1°C increase—is it a part of the natural variability in the climate system or have anthropogenic, which simply means human caused, influences played a major role? In a recent survey given to more than 3,000 college students at the University of Illinois at Urbana-Champaign, it was found the approximately two thirds of those surveyed agreed that recent climate change was due to reasons beyond natural variability in the climate system. (see Figure Recent Climate Change Student Responses) Approximately 20% reported that the climate change is due to natural changes and the remainder was undecided. Let’s investigate both sides of this argument!
Yes, 66.9%
No, 19.6% J
Undecided, 13.5%
Recent Climate Change Student Responses Survey results from 3,000+ college students at the University of Illinois at Urbana-Champaign when
asked if climate was changing beyond natural
variability. Source: Snodgrass, E.
Recall from the Module Milankovitch Cycles and the Climate of the Quaternary that global climate will change as a response to changes in insolation, albedo and the composition of the atmosphere. It was shown that the amount of energy entering the earth-atmosphere system from the sun varies less than 0.1% during the 11-year solar cycle in sunspot activity. Outside of this cycle, the amount of energy from the sun has increased 0.12 Watts per square meter (W/m) since 1750. Is this enough excess energy to produce the 1°C increase in global temperatures that has been observed since the 1800s? As it turns out, the climate system needs nearly 8 times that amount of energy to warm by 1°C. This essentially eliminates fluctuations in solar output as the culprit for recent climate change.
Has the earth’s albedo changed since the 1800s? As we know from the Module Climate Processes; External and Internal Controls, increases in the Earth’s albedo lead to global cooling and decreases lead to warming. The net effect of human existence on Earth is to brighten the surface and increase the global albedo. This change is primarily accomplished through intensive agriculture where forest, marshland, and open prairie are cut down
and crops like soybeans, corn, wheat, cotton, and rice are grown in their place. Add this to the current high rates of deforestation in South America and Africa and the evidence is clear that mankind has increased the Earth’s albedo, which should have led to global cooling. (see Figure Deforestation
Deforestation in the Amazon (2010) Satellite image shows the extent of deforestation in the Amazon as of 2010. Source: NASA
Outside of human influence, planetary albedo can also be changed by major volcanic eruptions. When volcanoes erupt, they spew enormous amounts of soot, ash, dust, sulfur, and other aerosols into the atmosphere. During major eruptions, like that of Mt. Pinatubo in 1991, some particles of this debris find their way into ne ane ae were they reside for a few years. (see Figure Mt. Pinatubo Erupting in 1991) The presence of these particles
high in the earth’s atmosphere acts like a shield that prevents sunlight from penetrating through the lower atmosphere to warm the earth’s surface. Instead, the energy is either absorbed by the particles or reflected and scattered away. The net effect is that large volcanic eruptions can cool the planet for a few years by changing the earth’s albedo.
Mt. Pinatubo Erupting in 1991 Photograph of Mt. Pinatubo erupting in the Philippines in 1991. Source: USGS/Cascades Volcano Observatory
Observations of Solar Output and Volcanic Eruptions
At first glance the Figure Radiative Forcings & Simulated Temperatures looks quite complicated, but let’s break this graph down to understand how changes in the sun’s output and volcanic eruptions have contributed to recent climate change. In the top panel (a), changes in the amount of energy, measured in W/m?, are graphed against time to show how volcanic eruptions have impacted the amount of energy the earth receives from the sun. Notice that around the year 1815, when Mt. Tambora erupted, there is a large downward spike in the plot. Now, examine the bottom panel, which shows the NH temperatures, just as Figure Northern Hemisphere Surface Air displayed, and see how the temperatures in the years following 1815 took a sharp downward turn. This is a direct consequence of the changes in albedo caused by large volcanic eruptions. Next, look at the time period between 1000 and 1300 A.D., the so-called Medieval Warm Period. In panel (b), changes in solar output are graphed against time; notice that during the Medieval Warm Period, the amount of insolation was high compared to the average. The opposite occurred during the Little Ice Age which peaked around 400 years ago.
8 i 8 8 8 38 oS a
(2. MA) Buyos0y o}UeTI|OA,
Solar irradiance forcing (W m7”)
— — GSZ2003 —— ORB2006 —— TBC..2006 ——- AJS..2006 —— BLC..2002 ———- CBK..2003 ——— GRT..2005 —— GJB..2003 B..2003-14C —-- B..2003-10Be —-- GBZ..2006 ——- SMC2006
(c) All other forcings
(.-w mM) sBuyo10) JeuI0 liv
Overlap of reconstructed temperatures
| | |i
0 10 20 30 40 50 60 70 80 90 %
Temperature anomaly (°C wrt 1500-1899)
Radiative Forcings & Simulated Temperatures Plot (a) - Radiative forcing due to volcanic eruptions over the last 1,300 years. Plot (b) - Radiative forcing due to fluctuations in solar irradiance over the last 1,300 years. Plot (c) - Radiative forcing due to all other forcing over the last 1,300 years. Plot (d) — Northern Hemisphere temperature reconstruction with overlap (shading) over the last 1,300 years. Source: Climate Change 2007: The Physical Science Basis: Contribution of Working Group I to the Fourth Assessment Report of the
University Press
Alterations to the Natural Greenhouse Effect
We have ruled out the first two mechanisms (i.e., changes in albedo and insolation) as reasons for the recent increase in global temperatures. But when we look at panel (c) in Figure Radiative Forcings & Simulated Temperatures, we notice that the “all other forcing” curves point to a rapid increase in the amount of energy retained by the earth-atmosphere system over the last 200 years. What is responsible for the increasing tail on this graph? Have humans altered the composition of the Earth’s atmosphere to make it more efficient at absorbing the infrared radiation that would have otherwise been lost to space? Is there proof of a human enhancement to the natural greenhouse effect? Can we explain the recent warming on an anthropogenic adjustment to the greenhouse gases like carbon dioxide (CO>)? Is an “enhanced greenhouse effect” to blame for the fact that the top ten warmest years since the modern era of instrument measurements have occurred since 1995, as seen in Figure Annual Global Temperature Anomalies.
Jan-Dec Global Mean Temperature over Land & Ocean
if
1880 1900 1920 1940 1960 1980 2000 NCDC/NESDIS/NOAA
@ Anomaly (°C) relative to 1901-2000
Annual Global Temperature Anomalies Global average surface temperature from 1880 to 2007. Source: National Climate Data Center
Long before the term “global warming” became a common household phrase, nineteenth-century Irish physicist John Tyndall said, “Remove for a single summer-night the aqueous vapor from the air which overspreads this country, and you would assuredly destroy every plant capable of being destroyed by a freezing temperature.” This now famous quote reveals the importance of greenhouse gases, like water vapor, in maintaining a balance between the incident solar radiation and the emitted terrestrial radiation. Tyndall understood that without greenhouse gases, water vapor being the most abundant, the earth’s temperature would be markedly cooler. The global average surface temperature is approximately 15°C (59°F) but if the greenhouse gases were removed, the average global temperature would plummet to -18°C (0°F). Remember that these gases make up a small fraction of the composition of the atmosphere! Therefore, adjustments to their concentration will produce dramatic effects.
To understand why these gases are so efficient at keeping the planet warm, let’s examine Figure Atmospheric Transmission. The top panel of this
figure shows the normalized intensity of the radiation emitted by both the sun and earth as a function of wavelength. The middle panel shows the total atmospheric absorption spectrum and the bottom panel shows the individual gas absorption spectrum (excluding Nitrogen and Argon). Notice from the top panel that the sun’s peak energy emission falls within the visible portion of the spectrum and suffers very little atmospheric absorption (middle panel). The peak emission wavelength for the earth is in the thermal infrared (IR), and it is effectively absorbed by water vapor (H20), carbon dioxide (CO), methane (CHy) and nitrous oxide (NO>). The primary purpose of this figure is to show that the gases in the earth’s atmosphere are transparent to the sun’s peak energy emission (visible light) but not the earth’s peak emission (thermal IR). It is through the absorption of the earth’s outgoing thermal infrared radiation that the global average temperature warms approximately 60°F over what it would be without greenhouse gases.
Radiation Transmitted by the Atmosphere 2 1 10 70
Downgoing Solar Radiation Upgoing Thermal Radiation 70-75% Transmitted 15-30% Transmitted
Spectral Intensity
-_
Percent of SaaS
ye
Oxygen and Ozone
Nitrous Oxide
Major Components
Rayleigh Scattering 70
0.2 1 10 Wavelength (um)
Atmospheric Transmission Top graph — normalized spectral intensity (radiant energy) emitted by the earth and sun as a function of wavelength. Middle graph — total atmospheric absorption as a function of wavelength. Bottom graph — individual gas absorption as a function of wavelength. Source: R.A. Rohde for Global Warming Art Project
Are humans altering the natural greenhouse effect? Based upon our assessment so far, this is the final mechanism by which the global climate can be changed. Let’s look into the alteration of the chemistry and composition of the earth’s atmosphere. First are humans increasing the amount of water vapor, the most abundant but also weakest greenhouse gas in the atmosphere? As the air temperature increases, the amount of water vapor the atmosphere can hold also increases. However, a closer investigation of the water cycle is needed to understand what will happen to this increase in water vapor. In this cycle, the amount of evaporation must equal the amount of condensation and thus precipitation on a global scale. This equilibrium must be achieved or else water would end up entirely in its liquid form or in its vapor form. Also due to the speed at which the hydrological cycle operates, a large increase in water vapor would be quickly precipitated out of the atmosphere.
Other greenhouse gases progress through their respective cycles much more slowly than water. There are vast amounts of carbon and carbon dioxide in the earth-atmosphere system. Most carbon is locked up in rocks, where it may remain for millions of years. The carbon dioxide that is mobile, however, is mostly found in other places: the ocean, soils, vegetation, fossil fuels like coal, oil, and natural gas, and also in small concentrations in the atmosphere. These reservoirs of CO can exchange mass like oceans and clouds do in the water cycle, but with one extremely important difference— the exchange rate is much slower. That means the system can get out of balance and remain out of balance for a long time, hundreds or thousands of
years. There are two primary mechanisms for sequestering carbon dioxide that is released into the atmosphere: it can be captured by the respiration of plants, or dissolved in the ocean.
However, the rate at which plants and oceans can take CO, out of the atmosphere is fixed. Therefore, if a surplus of CO, is added to the atmosphere, it will stay there for a long time. This has major implications, given the fact that CO, is a powerful greenhouse gas. The question then to ask becomes, “is this exchange rate out of balance?”
The current average concentration of CO, in the atmosphere is about 390 parts per million (PPM), which means there are 390 parts of CO> per million parts of air. That does not seem like very much, but if that small amount of carbon dioxide were removed from the air, the global average temperature would plummet. Has this concentration been changing? To answer the question, we will turn to the findings of Richard Keeling, whose life’s work was the observation of CO, concentrations at the Mauna Loa Observatory in Hawaii. Beginning in the early 1950s, observations of COs, a well-mixed gas in our atmosphere, have shown a remarkable climb in concentration. (see Figure CO» Concentrations at the Mauna Loa Observatory) The “Keeling Curve,” as it is sometimes called, clearly shows that since the 1950s CO, concentrations have increased steadily from 315 ppm to 390 ppm. The zigzag nature of this graph is due to life cycle of plants in the NH. The NH has much more land area that the SH, so when spring and summer arrive in the NH, the abundance of new plant life reduces the CO» concentrations in the atmosphere. When the plants die or become dormant in the fall and winter, CO concentrations spike again.
380- i a |
wts per million)
Co, (p<
Mauna Loa Observatory
1960 1970 1980 1990 2000 Year
CO, Concentrations at the Mauna Loa Observatory The “Keeling Curve” of CO) concentrations measured in Mauna Loa, Hawaii, since the 1950s. Source: NASA Earth Observatory
What is troublesome about this figure is that the carbon cycle is out of its normal rhythm and a surplus of CO», a known greenhouse gas, is building in the earth’s atmosphere. Where is this surplus coming from? To answer this question, let’s look at two historical records of CO, concentrations taken from ice core deposits. The top panel in Figure Changes in Greenhouse Gases from Ice Core and Modern Data shows the past 10,000 years of atmospheric CO, concentrations. Before 1750, the amount of CO, in the atmosphere was relatively steady at 280 ppm. Since 1750 there has been a dramatic increase in CO, concentrations.
Methane (ppb) Carbon Dioxide (ppm)
Nitrous Oxide (ppb)
i £ 350 = a £ 5 irs @ 300 = s co c 250 2000 i £ 1500 = b°)) [=] 9 © 1000 g rs 5 co) c 500 330 @IPCC 2007: WG1-AR4 i £ 300 = t)) c¢ ° £ g 270 = s iy c
10000 5000 0 Time (before 2005)
Changes in Greenhouse Gases from Ice Core and Modern Data Top panel shoes CO, concentrations (ppm) over the
last 10,000 years. Source: Climate Change 2007: The Physical Science Basis: Contribution of Working_Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change
If we look even further back in time, over the last half million years, we see a similar story. (see Figure Evidence of Climate Change) The current concentration of CO, in the earth’s atmosphere is higher than at any time in the past half million years. Where is this abundance of CO, coming from? Which reservoirs are being depleted of their CO, while the atmosphere takes on more? The answer lies in the burning of fossil fuels and in the deforestation of significant chunks of the earth’s forest biomes. Notice the spike in CO» concentrations beginning around 1750. This time period marks the beginning of the industrial revolution, when fossil fuels overtook wood as the primary energy source on our planet. Over the subsequent two and a half centuries, oil, coal, and natural gas have been extracted from their underground reservoirs and burned to generate electricity and power modern forms of transportation. The exhaust from this process is currently adding 30 billions of tons, or gigatons (Gt), of carbon dioxide to the atmosphere each year. Combine this addition of CO2, a known greenhouse gas, to the subtraction of one of the sinks of CO, through deforestation and the imbalance grows even further.
current level ——>
c ° & n ~ a
N O
400,000 350,000 300,000 250,000 200,000 150,000 100,000 50,000
YEARS before today (0 = 1950)
Evidence of Climate Change CO, concentrations over the last 400,000+ years. Source: NASA/NOAA
What is the end result? By examining the earth’s climate, both current and past and by investigating the three ways in which climate can change, we have arrived at the conclusion that the current warming is being caused by an imbalance in the carbon cycle that has been induced by human activity, namely the burning of fossil fuels. The record warmth over the last 1,300 years is very likely to have been caused by human decisions that have lead to a change in the chemistry of the atmosphere, and which has altered the natural climate variability toward warmer global temperatures. We are essentially changing the climate faster and in a different direction than natural processes have intended.
Observed Effects of Climate Change
Cherry Blossoms
In Japan each spring millions of people celebrate the blossoming of the cherry trees to mark the arrival of warmer weather. These celebrations have
a long and storied history, and records of the cherry blossom festivals date back more than a thousand years. In fact, the record of the timing of the cherry blossoms in Japan is the oldest for any flowering plant! Two scientists and historians. Richard Primack and Hiroyoshi Higuchi recently analyzed this record and found that beginning in the early 1800s the mean air temperature in March has slowly risen, similar to the increase shown in Figure Northern Hemisphere Surface Air. During this same time period, the flowering date has slowly crept earlier in the season, and the trees are now flowering several days before they traditionally flowered. Although urbanization of Japan has lead to an increase in temperature, recent climate change is blamed for the earlier flowering of the Japanese cherry blossom tree. Primack and Higuchi show how Kyoto has warmed an average of 3.4°C over the last 170 years. Climate change has contributed 18% to this total warming in Japan and Primack and Higuchi demonstrate the correlation of this warming with the industrial revolution.
Cherry Blossoms Photograph of cherry blossoms. Source: Uberlemur via Wikimedia Commons
Birds, Mosquitoes, and Fire Ants
A recent article in the journal Nature discussed the response of plants and animals to current climate change. Phenologists, scientists who study how the periodic life cycle events of animals and plants are affected by variations in climate over the course of seasons and years, are finding that many species of birds are breeding and singing earlier in the year. Migrant birds are arriving earlier, butterflies are appearing earlier and some amphibians are spawning weeks ahead of their historical schedule. In addition, mountain tree lines, which are controlled by air temperature, have been advancing to higher altitudes in Europe, and Arctic shrubs are now found in regions that were once too cold for their existence in Alaska. While ecological changes such as these may not be threatening from a human perspective, others are. For example, malaria-carrying mosquitoes in Africa are now being found at altitudes that were once too cold for them, and outbreaks of malaria are showing up in towns and villages once thought to be out of their reach. In parts of California and Australia, fire ants are migrating to regions that historically have been too cold to support them.
Fire Ants Photograph of fire ants on a piece of wood. Source: Scott Bauer of the Agricultural Research Service, U.S. Department of Agriculture via Wikimedia Commons
Mosquitos Photograph of a mosquito on skin. Source: Centers for Disease Control and Prevention
Impacts of Change in the Arctic and the Antarctic
The Arctic and Antarctic are the regions experiencing the most rapid changes due to the recent warming of the earth’s atmosphere. These two regions on Earth are a part of the cryosphere, which is defined as the part of the Earth that is occupied by sea ice, lake ice, ice caps and permafrost. (For a comprehensive overview of the current state of the cryosphere and an excellent archive of data, please check out “The Cryosphere Today’) As explained in the Module Milankovitch Cycles and the Climate of the Quaternary, these regions are most vulnerable due to the powerful ice- albedo effect. One amazing depiction of polar warming can be found in the drunken forests of Siberia. Larch and spruce trees there are often seen tilted over on their sides and growing at strange angles. Why? Because the once continually frozen soil, or permafrost, in which they are rooted has been melting in recent years. As the soil thaws it becomes more malleable and the trees begin to slant as the soil beneath them sinks. Farther north, Arctic sea ice has been decreasing both in extent and concentration. In 2007, the
smallest extent of sea ice was measured since the 1970s, and the Northwest Passage opened for commerce and exploration. As the sea ice extent and concentration decreases, so does the habitat of polar bears. The sea ice is a vital part of their hunting grounds, and recent decreases of this ice have greatly reduced their access to certain prey. In addition to sea ice reductions, surface melt of the ice sheet on Greenland has increased in recent years, especially along its edges. This melt has lead to large pools and streams forming on top of this mile-thick sheet of ice. On the other side of the world, the Larsen B ice shelf in Antarctica recently collapsed, sending a large section of ice into the sea. This section of the Antarctic ice cap was roughly as large as the state of Rhode Island and it had been stably attached to the ice shelf for the past 12,000 years. Scientists are closely watching the Antarctic ice as nearly two-thirds of the world’s fresh water resides there. Finally, alpine glacier retreat has been observed on every continent. With few exceptions, these glaciers have been retracting heavily since the 1960s, and over that time period NASA reports a global loss of 8,000 cubic kilometers of ice, which represents a what percentage reduction?
Drunken Forests of Siberia Source: NASA Science blog
Annual Sea Jce Minimum
million square 5 km
1980. wt. “4985. 1990 1995 2000 2005
2007 Sea Ice Extent in the Arctic Source: NASA Goddard Space Flight Center
The Oceans’ Response
Further dramatic changes brought on by recent warming have been observed by scientists concerned with the world’s oceans. Observations of the world’s coral reefs have revealed an alarming rate of coral bleaching (which is not caused by chlorine). As the oceans attempt to uptake the abundance of CO, and absorb nearly 80% of the heat added to the earth- atmosphere system from the enhanced greenhouse effect, the waters will inevitably warm. As these waters have warmed over the past 40 years, the delicate ecological balance within some of the world’s coral reefs has been upset leading to coral bleaching. Under warmer waters the rate at which the algae, which is an important part of the coral ecosystem, undergoes photosynthesis is too much for the coral to manage. As a result, the coral rids itself of the algae, which leads to an exposure of the white skeleton of the coral. Another consequence of warming oceans is an increase in sea level. Since 1880, sea level has risen 20 cm (8 inches). The rise in sea level
is associated both with an increase in glacial melt water and in the thermal expansion of the seawater. An interesting consequence of this rise in sea level has been the disappearance of the long-disputed New Moore Island between Bangladesh and India. Both countries laid claim to the shallow, uninhabited island due to the speculation that oil reserves may lie beneath it, but in 2010, the sea swallowed it. Scientists at the School of Oceanographic Studies at Jadavpur University, Kolkatta, India suggest global warming played an important part.
Coral Bleaching A part of coral that has experienced coral bleaching. Source: NOAA
Finally, as the planet has adjusted to warmer temperatures the proliferation of drought conditions in some regions has dramatically affected human populations. The Sahel, for example, is a border region between the Sahara Desert in the north of Africa and the tropical rainforests that occupy the central part of the continent. (see Figure The Sahel in Africa) This region is experiencing desertification as the Sahara steadily expands southward.
Since the 1970s, the amount of precipitation in this region has been steadily below normal. The combination of over irrigation and recent climate change has made the region uninhabitable and forced millions to relocate.
Vegetation (NDVI) i) 0.3 06 0.9
The Sahel in Africa Source: NASA Earth Observatory
Sahel Rainfall Index
' ' ' ' , 1900 1910 1920 1930 1940 1960 1960 1970 1980 1990 2000 Year
The Sahel Rainfall Index Source: NASA Earth Observatory
Review Questions
Exercise: Problem: In Figure Northern Hemisphere Surface Air the dividing line on the
graph is the 1961-1990 average temperature. Explain the relevance of this line to the data presented in this figure.
Exercise: Problem: Explain how deforestation can lead to both a warming effect and cooling effect for global temperatures. Exercise: Problem: In Figure Atmospheric Transmission, which gas is contributing the
most to the absorption of ultra-violet light? If this gas were removed from the atmosphere, how might global temperatures respond?
Exercise:
Problem:
If the surface of the Greenland Ice Sheet continues to melt, how will this impact the albedo of this region and what impact will this have on the air temperature there?
Exercise:
Problem: When sea ice melts, what happens to global sea level?
References
Walther, G. R., Post, E., Convey, P., Menzel, A., Parmesan, C., Beebee, T. J .C., et al. (2002, March 28). Ecological responses to recent climate change. Nature, 416, 389-395. doi: 10.1038/416389a
Glossary
anthropogenic Caused or produced by humans.
hydrological cycle The continuous movement of water on, above and below the surface of the earth. This cycle is dominated by the global equilibrium in evaporation and condensation.
little ice age A cool period in the NH, primarily in Europe from the sixteenth to the nineteenth century.
medieval warm period A warm period in the NH during the tenth and eleventh centuries.
northwest passage A sea route for commerce through the Arctic Ocean north of Canada.
permafrost
Soil that has a temperature that has remained below freezing (0°C or 32°F) for at least two years.
radiative forcing Change in net irradiance (an energy flux) measured at some boundary. For this text the boundary is typically at the surface of the earth or the top of atmosphere. A positive change indicates warming and a negative change indicates cooling.
watts per square meter (W/m?) Energy (Joules) per second moving through a surface (square meter). A flux of energy through a surface area.
well-mixed gas A gas that can be found at the same concentration throughout the lower atmosphere regardless of location.
Climate Projections
In this module, we will investigate the findings of the Intergovernmental Panel on Climate Change (IPCC) and look at future climate projections. We will inspect these findings and analyze their impacts on a global scale.
Learning Objectives After reading this module, students should be able to
e assess global CO, emissions and determine which countries and regions are responsible for the greatest emissions currently and historically
e explain the relationship between fossil fuel usage and CO, emissions
e link variables such as wealth, population, fuel imports, and deforestation to CO, emissions
e use IPCC future climate projections to assess future global temperature scenarios
e distinguish between weather events and climate change, and discuss the differences between weather forecasting and climate projections
e analyze the anthropogenic impact on climate by examining climate change without people
e assess the regional and global impacts of climate change on air temperature and precipitation
Introduction
In the Module Modern Climate Change we discovered that the global warming of approximately 1°C over the past 200 years was human induced through an enhancement of the natural greenhouse effect. We learned that the burning of fossil fuels has upset the natural carbon cycle, which has steadily increased the amount of carbon dioxide (CO>) in the atmosphere since the 1750s. Finally we looked at ancillary evidence of this warming to see the immediate impact of these changes. In this module we will investigate the findings of the Intergovernmental Panel on Climate Change (IPCC) and look at future climate projections. We will inspect these findings and analyze their impacts on a global scale.
Who is Responsible? Factors to Consider
In 2007, the IPCC was awarded a share of the Nobel Prize for its work in the area of global climate change. The IPCC is organized through the United Nations and is composed of over 3,000 scientists from around the world who are working together to understand current climate change and project future climate scenarios. As of 2011, the IPCC has released four comprehensive reports, and it has concluded, “Most of the observed increase in global average temperature since the mid-twentieth century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.” This widely known statement essentially means that the probability of occurrence is greater than 90% that the current global warming is caused by humans burning fossil fuels. In response to these findings, the United Nations Framework Convention on Climate Change has called for numerous international meetings in cities including Kyoto, Bali, Copenhagen, and others where the leaders of world have gathered to discuss strategies to mitigate this looming disaster. At these meetings, scientists, politicians and world leaders review the current state of knowledge about the problem and strategize for the future. This chapter will take a large-scale view of the global challenges of climate change.
Over the past few years, China has surpassed the United States to become the nation that emits more greenhouse gasses than any other (see Figure CO, Emissions for the United States and China). Currently, China is responsible for just over 25% of global CO, emissions, which are approximately 30 Gt per year, with the United States in a close second place. It is important to consider population when reviewing these numbers because there are over four times as many people living in China than in the United States. When you compare these two countries on a per capita basis, the average U.S. citizen emits approximately 19 metric tons of CO, per year while the average Chinese citizen emits approximately five metric tons. In 2009, the United States consumed more than double the amount oil than the second largest consumer, China, according to the U.S. Energy Information Administration. Topping the list in per capita CO, emissions is the oil rich nation of Qatar. This small country located on the Persian Gulf has the largest per capita production of oil and natural gas. It also has the world’s
highest gross domestic product (GDP) per capita. An average citizen in this country emits nearly 60 metric tons of CO, into the atmosphere each year.
|
Million Metric Tons of CO2 Million Metric Tons of CO2
1K
Soo
So T
0-+ 7 0 "80 '82 '84 ’86 '88 90 '92 94 '96 98 00 02 '04 06 09 ’80 '82 '84 ’86 '88 '90 '92 '94 96 98 00 02 04 06 0 Year
Carbon Dioxide Emissions from Consumption Carbon Dioxide Emissions from Consumption
CO, Emissions for the United States and China CO, emissions in millions of metric tons graphed against time for the United States and China. Source: Snodgrass, _E. created graphs using data from the U.S. Energy Information Association
Rather than point the finger at individual countries, let’s examine the bigger problem. The maps in Figure Global Influence Maps distort the size of each country based on a certain variable, like CO, emissions, with respect to the rest of the world. In the upper left panel, the map is based on population, which is why China and India appear so large. The upper right map distorts the size of the country based upon fuel imports. Notice that the
United States, much of Europe, and Japan are expanded the most, while Africa, the Middle East, and much of South America are barely visible. Compare these two maps with absolute wealth and carbon emissions and the story is quite clear. The industrialized and wealthy nations are responsible for the largest quantities of carbon emissions and fuel imports. These societies are built on the foundation of energy production through the consumption of fossil fuels.
The bottom two panels tell another aspect of this story. Focus first on the graph in the lower right, which shows forest loss by country. The world’s forest biomes are a large part of the CO, cycle and with deforestation, a large sink for atmospheric CO; is taken away. Notice that deforestation is most prevalent in Africa, South America, and Indonesia while the United States is barely visible on this map. In the United States, reforestation is practiced, but in the rainforests of the world, which are those areas in South America, Africa, and Indonesia that are ballooned on this map, deforestation is commonplace.
Population
oe Absolute a :
Poverty — Z Forest Loss ~_
Global Influence Maps The variables labeled on each map are used to distort the size of each country to show their global influence. Source: WorldMapper, © Copyright SASI Group (University of Sheffield) and Mark Newman (University of Michigan).
The last graph in Figure Global Influence Maps distorts each country’s size according to poverty. Much of Asia and Africa are distorted the most, and it is in these regions that we need to pay close attention over the upcoming years. Many of the nations found within these countries are what economists and politicians call “emerging economies.” Although much of the current abundance of CO, in the atmosphere is from developed countries such as the United States, CO» emissions from these countries are not increasing with time according to a 2008 report from the Energy Information Administration. In Figure Global CO) Emissions from Coal
Combustion, the world’s CO, emissions from coal combustion in billions of metric tons are plotted against time. Notice that countries of the Organization for Economic Co-operation and Development (OECD), which comprises a large group of developed and industrialized nations, have not increased their CO, emissions from coal combustion since 1990, and future projections also reveal a flat line in CO, emissions. Compare this to the non-OECD countries, many of which are emerging economies like China and India, and you see that CO, emissions are set to triple in the next 25 years. There is much debate over information like this now that recent climate change has been linked so closely to anthropogenic emission of CO>. This debate revolves around the fact that developed nations used coal, oil, and natural gas during a time when the impacts of CO, and climate change were not well researched. This meant that during the time these countries, including the United States, industrialized there were no regulations on the emissions of CO». Now that CO> emissions have been shown to cause global warming, pressure is being applied to these emerging economies to regulate and control their CO, emissions. This is subject of much of the debate at the international climate summits at Kyoto, Bali, and Copenhagen. What is important to remember when discussing developed countries vs. emerging economies is that the per capita emissions of CO, in emerging economies are approximately one third of those for developed countries.
15 History Projections
Non-OECD 10 “w § uv b 3) E g 2 5 OECD 0 r + 1990 2000 2007 2015 2025 2035
Global CO, Emissions from Coal Combustion The world’s CO2 emissions from coal combustion in billions of metric tons are plotted against time for OECD countries and non-OECD countries. Source:
U.S. Energy Information Administration (Oct 2008)
Climate Projections
One of the greatest obstacles climate scientists face in educating the public on issues of climate change is time. Most people take weather and climate to be one branch of scientific study. In reality, this could not be further from the truth. Weather and climate are two separate fields of study that are
joined only by one definition—climate is the average of weather. It is important to understand this statement because people—news reporters, broadcast meteorologists, politicians, and even scientists—often make the mistake of attributing weather events, such as Hurricane Katrina (2005), to global climate change. Katrina was a weather event and, as such, it cannot be said to have been caused by global climate change. Are the ingredients for stronger hurricanes present in greater frequency now than they have been in the past? That’s the type of question climate scientists seek to answer, and they do so by analyzing decades worth of data. Thirty years is the lowest value used in the denominator of climate calculations. In other words, 30 years is the shortest time period over which weather can be averaged to extract climate information. Therefore, it is impossible to blame a single weather event on climate change—this branch of science does not work that way.
To better understand the differences between weather and climate, take a look at Figure High Temperature vs. Low Temperature, Champaign, IL which shows in red the actual high temperatures for each day in 2005 in Champaign, Illinois, compared to the average high temperature in black over a period beginning in 1899 and ending in 2009. It is completely normal for the temperature to vary +20°F around this average. In 2005 there were only a handful of days where the actual high was the same as the average high. This graph shows the highly variable and chaotic behavior of weather. But, when data from a long span of time is averaged, the climatological mean emerges.
2005 High Temperature vs. Average Temperature (1899-2009) Champaign, Illinois
Temperature (°F)
10 ~ ~——2005 High Temperature —Average High Temperaure
High Temperature vs. Low Temperature, Champaign, IL The average high temperature for Champaign-Urbana Illinois in black (1899-2009).
The 2005 actual high temperature are graphed in red. Source: E. Snodgrass using data from the National Climate Data Center
To think of it another way, imagine you are in a large lecture hall with over 300 college students. If the professor were to call out one student and try to predict the course of her life over the next 70 years it would be nearly impossible! It would even be difficult to predict when that person would eat her next meal. However, the professor could project with great confidence that on average, most of the people in the room will eat dinner at 6:30PM on a given night. Beyond this meal, most of them will graduate from college by the time they are 22 years old. Many will be married by 27 years old and have their first children at 30. Most will have a job by the time they are 24 and most will have a job they like by 34. Most will have a total of 2.1 children by the time they are 36, and by the time they are 50 most will have gone to the doctor to have their first routine procedure. Most will
retire at 67, and since they are college grads in the United States, there is a safe bet that they will retire with over a million dollars in assets. On average, the men in the room will die at 85 years old and most of the women will die before their ninetieth birthday. Now, if the professor were to single out one individual, the chances that her life would follow this path exactly are small, but when an entire class of 300 is averaged, this is the result. Weather is like the individual life. Climate is like the average of 300 lives. Weather and Climate are two separate branches of study in atmospheric science.
In addition to keeping in mind the difference between weather and climate, remember that the focus of this chapter is global climate change. It is tempting to forget the global nature of this problem because it is happening very slowly on a large scale and it is averaged over long time periods. Recall the differences between weather and climate and remember that in conjunction with global warming there can still be weather events that take temperatures far below normal. The temptation during these events is to discount the science behind global climate change. For example, during the winter of 2009-2010, the weather patterns were such that the east coast of the United States experienced repeated record-setting snowstorms and cold air outbreaks. Many television news reports, weather broadcasts, and newspaper headlines scoffed at the idea of global warming during this winter and proclaimed that it was not happening or that it was a hoax. The shortsightedness of such responses is evidenced by the fact that globally, 2009 and 2010 were among the warmest years during the instrument record: 2009 ranked seventh, and 2010 tied for first. These were likely two of the warmest years of the last 1,300.
Climate Modeling and Future Climate Predictions
Sometimes people discount climate predictions based on their understanding of weather predictions. They will say something like, “Meteorologists can’t even give me a reliable forecast of the weather over the next three days, how am I supposed to trust them to give me the forecast for the next 100 years.” You’re not! Climate scientists do not use weather forecast models to forecast climate conditions 100 years in advance. The computer models that are used to predict the weather over the next few days
are entirely different from those used to predict the climate. Instead of predicting the highly chaotic nature of temperature, precipitation, and other common weather variables at very high spatial and temporal resolution, climate models forecast changes in the flux of energy between earth and its atmosphere and space. These two computer-modeling techniques differ substantially in their computational expense as well. Although weather forecast models are run on extremely fast computer systems at the National Center for Environmental Prediction, the fastest computers in the world, like the Earth Simulator in Japan and Blue Waters at the University of Illinois at ivan -Champaign are oa with climate simulations (see
nputi hg
Petascale Computing Facility The petascale computing facility “Blue Waters” located at the pena ie ae ok at oe Champaign. Source: HorsePunchKid via Wikim n
What are these climate models predicting will happen by the year 2100? First, we will look at the global average surface temperature projections. Figure Climate Simulation Scenarios plots global surface warming against time with the present day in the middle of this chart. Recall that over the last 200 years, there has been a 1°C increase in global temperatures, and that the rate of change has been extremely fast compared to natural changes in the earth’s climate. The graphs in Figure Climate Simulation Scenarios show the range of model projections from different climate simulation scenarios based upon various greenhouse gas emission scenarios (left graph). Focus on the top and bottom curves in the right panel, which show the most dramatic warming and the most conservative warming. The worst- case scenario, found in the top line, shows the “business as usual” projections. If nothing is done to mitigate the emission of greenhouse gases into the atmosphere, these climate models are predicting a 4°C to 6°C increase in global average temperature by 2100. The best-case scenario, from a climate change perspective, would be for a cessation of CO> emissions or for the current emission rates to not increase. In this case, there would still be a warming of 0.5° to 2°C by 2100 as indicated by the bottom curves.
post-SRES (max) /
2 °
MM post-SRES range (80%)
= ~ _ 5.0 == AIT a == AiB 8 2 40 = © 120 E — AIFi @ § 3.0 c w= Year 2000 constant 100 8 concentrations 2 = 2.0 = 20" centu § 80 5 - ro) 3 60 8 1.0 B sol - $ 5 0 - 20 -1.0 fe) 2000 2100 1900
Year
Climate Simulation Scenarios Left — multiple climate model projections (or scenarios) of greenhouse gas emissions (including CO2, CH4 and N2O) emissions in
Gt-CO2-equivalent through 2100. Right — multiple climate model projections of globally averaged surface air temperature through 2100. Source: Climate Change
2007: Synthesis Report, Contribution of Working Groups I, II and III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, IPCC, figures 3.1 and 3.2, pages 44 and 46.
In addition to predicting warming of the atmosphere, climate models also suggest that sea level will continue to rise. Since 1880, sea level has risen 20 cm (approximately 8 inches) as seen in Figure Sea Levels since 1880. This rise has been primarily the result of the water thermally expanding as it warms along with the atmosphere. Polar ice cap melt from land-based ice sheets and glaciers has also added to increase in sea level. The current projection is that sea level will rise at the rate of at least 2 mm per year over the next century, with an overall increase ranging from 15 to 60 inches cm.
Sea level (mm)
1 _ = 5
1880 1900 1920 1940 1960 1980 2000 year
Sea Levels since 1880 Measured sea level rise since
1880. The different colors represent different data sets used to make this graph. Source: Climate Change 2007: The Physical Science Basis: Contribution of the Intergovernmental Panel on Climate Change, | Cambridge University Press, figure 5.13, page 410
How much confidence can we place in predictions about temperature and sea level by climate scientists? Let’s take a little detour before we address this important question directly. Imagine you are contemplating signing up with a psychic so you can better plan for the future—why save for retirement if money is tight and you’re not sure how long you’|I live? But you are uncertain about whether she can really see what lies ahead. You could pay her $20 a week for her predictions, and discover over time whether they come true or not. The trouble is, during this trial period you wouldn’t know whether to spend your money as fast as you make it or put some aside. But you come up with a better plan. You’!l pay the psychic $20 one time, but instead of asking her to predict your future, you’ ll ask her to tell what has happened to you in the past week. If she gets that right, she gets your business.
Along similar lines, climate scientists assess the trustworthiness of their models by checking how well they “predict” the past. In Figure Model Simulations, 58 different climate model simulations were tasked with predicting the past climate from 1900 to 2005. By comparing the model simulations to the observed temperature record the scientists with the IPCC tested the accuracy of their models. In Figure Model Simulations, the yellow lines in the top panel trace out the individual model simulations, the red line shows the model ensemble mean, and the black line represents the actual observed mean temperature. The models performed exceedingly well, as evidenced by the very small variability around the observed temperature. The success of this test demonstrates the high-quality construction of these models and shows they are capable of accurately projecting the earth’s future climate.
Temperature anomaly ((C) ©
Temperature anomaly ((C) &
Pinatubo Santa Maria Agung EF! Chichon
-1.0
1900 1920 1940 1960 1980 2000 Year
1.0
0.5
-1.0 1900 1920 1940 1960 1980 2000 Year
Model Simulations Top panel - Climate model simulations of the global mean surface temperature compared to the observed global mean surface temperature in black. Each yellow line is one of 58 climate model simulations of which the red line is the ensemble mean. Bottom panel — 19 climate model simulations in blue with the ensemble mean in dark blue. These simulations were run without anthropogenic influences. The thick black line is the observed global mean surface
temperature. For a description of each scenario, please click here. Source: Climate Change 2007: The Physical Science Basis: Contribution of Working_Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate
Press, figure 9.5, page 684
The bottom of Figure Model Simulations and Figure Global Surface Temperature Comparisons presents the most compelling argument that current climate change is caused in large part by humans. The bottom panel of Figure Model Simulations shows 19 climate model simulations between 1900 and 2000 with human influences left out of the simulations. The thick black line represents the observed global mean surface temperature over this time. Compare this figure with that of Figure Global Surface Temperature Comparisons, which depicts a series of graphs that plot temperature anomalies against time from the early 1900s to 2000. The blue color shading on these graphs shows the computer model projections without anthropogenic effects, while the pink shading includes them. The black line represents the actual measured air temperatures in each of the locations over which the inlaid graphs are positioned. Notice that without humans the blue shading stays level or decreases with time. Compared with the pink shading and the black line, which both increase with time, and we find that these climate simulations cannot accurately represent the past climate without anthropogenic effects. Simply put, these models are unable to represent our current climate without greenhouse contributions from humans. Rigorous testing like this proves these models are robust and well- designed to simulate future climate conditions.
ee eee
Year Sse models using only natural forcings ——— observations models using both natural and anthropogenic forcings GPCG 20s: WOT