Encyclopedia of Global Warming and Climate Change

Encyclopedia of Global Warming and Climate Change

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Edited by: S. George Philander

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Abstract

The Encyclopedia of Global Warming and Climate Change helps readers learn about the astonishingly intricate processes that make ours the only planet known to be habitable. These three volumes include more than 750 articles that explore major topics related to global warming and climate change—ranging geographically from the North Pole to the South Pole, and thematically from social effects to scientific causes.

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  • Front Matter
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    • Atmospheric Sciences
    • Climate
    • Climate and Society
    • Climate Change, Effects
    • Climate Feedbacks
    • Climate Models
    • Countries: Africa
    • Countries: Americas
    • Countries: Asia
    • Countries: Europe
    • Countries: Pacific
    • Glaciology
    • Government and International Agencies
    • Institutions Studying Climate Change
    • Oceanography
    • Paleoclimates
    • People
    • Programs and Conventions
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      About the General Editor

      S. George Philander, Ph.D., Knox Taylor Professor of Geosciences, Princeton University, Research Director, ACCESS

      S. George Philander, Knox Taylor Professor of Geosciences at Princeton University, and Research Director of ACCESS (African Centre for Climate and Earth System Science) in Cape Town, South Africa, has a Bachelor of Science degree from the University of Cape Town, and a Ph.D. (Applied Mathematics) from Harvard University.

      He is a member of the National Academy of Sciences, and a fellow of the American Academy of Arts and Sciences, the American Geophysical Union, and the American Meteorological Society. Philanders research interests include the oceanic circulation, interactions between the ocean and atmosphere that result in phenomena such as El Niño and La Niña, paleoclimates (including the recurrent Ice Ages of the past three million years), and future global climate changes. His two books for laypersons, Is the Temperature Rising? The Uncertain Science of Global Warming, and Our Affair With El Niño: How We Transformed an Enchanting Peruvian Current Into a Global Climate Hazard reflect his keen interest in improving communications between scientists and laymen.

      The goal of the African climate center, which Philander is currently directing, is to give Africa its own voice on environmental issues such as global warming.

      Preface

      PLANET EARTH HAS become the concern of everyone. The activities of conservation biologists are now of interest to economists and political scientists who wish to find out whether certain environmental problems are best solved by regulations or market forces. Businesspeople, government officials, and politicians have become involved in science.

      To be useful to such a diversity of people, the nearly 750 entries in this 3-volume encyclopedia cover a vast range of topics affecting global warming and climate change. The entries amount to more than a catalog of terms; they are all part of one story about global warming and how it is likely to affect our world.

      Scientific objectivity have been the watchwords for the editors of this encyclopedia, yet different perspectives that various authors have on some of these issues are part of a conversation that citizens or students concerned about the environment ignore at their own risk. Even the title of the work, Encyclopedia of Global Warming and Climate Change, was carefully considered to include paleoclimatology in the discussion of weather, climate, and the current debate about global warming.

      The authors of the entries include geographers, political scientists, chemists, anthropologists, medical practitioners, development experts, and sociologists. They are experts in their fields of specialty; many are researchers with extensive fieldwork experience; most of the entries on emerging techniques and technologies were written by innovators. As the volumes intend, it has become increasingly essential to bring the multiplying global warming issues, concepts, theories, examples, problems, and policies together in one place, with the goal of clearly explaining an emerging way of thinking about people and their planet.

      Among the selection of articles, specific country entries are included, rather than climatic or environmental regions, to give the reader the opportunity to get information on the status of global warming—its causes and effects—by country, from Afghanistan to Zimbabwe. Also included are articles within specific categories, including: atmospheric sciences; climate; climate change effects; climate and society; climate feedbacks; climate models; institutions studying climate change; oceanography; paleoclimates; programs and conventions; and people studying climate change.

      Pedagogical elements of this encyclopedia include the 4-color Introduction by General Editor Dr. S. George Philander, in which the reader can get a “birds-eye view” of the sciences behind global warming. Also included in the work are a chronology of climate change, resource guide, glossary, and appendix of charts and table graphically presenting relevant data. Altogether, we hope the encyclopedia provides some groundwork for further discussion and spur possible action to curb global warming.

      Reader's Guide

      This list is provided to assist readers in finding articles related by category or theme.

      An Introduction (8.4 MB)

      S. George Philander Princeton University

      IN ITS 2007 report, the Intergovernmental Panel on Climate Change (IPCC), a large, international panel of scientists, all experts on the Earth's climate, concluded that human activities, specifically those that cause an increase in the atmospheric concentration of carbon dioxide, have started affecting the Earth's climate. The panel further predicted that far more significant climate changes are imminent. This report, and Al Gore's documentary An Inconvenient Truth are persuading a rapidly increasing number of people that human activities can lead to possibly disastrous global climate changes.

      Those nonscientists are passionate about being wise and responsible stewards of the Earth, but at present they are handicapped because they take the words of the scientists on faith, and accept the reality of the threat of global warming without grasping the scientific reasons. This is most unfortunate, because our response to the threat of global warming is far more likely to be effective if it were motivated, not merely by the alarms scientists sound, but also by knowledge of how this very complex planet maintains the conditions that suit us so well. We need an awareness of how extremely fortunate we are to be the Earth's inhabitants at this moment in its long and eventful history, and an understanding of how our current activities are putting us at risk. The purpose of this encyclopedia is to help the reader learn about the intricate processes that make ours the only planet known to be habitable. This encyclopedia covers, in addition to the science of global warming, its social and political aspects that are of central importance to the ethical dilemmas that global warming poses: (1) How do we find a balance between regulations and freedom? (2) How do we find a balance between our responsibilities to future generations, and our obligations to the poor suffering today?

      The first dilemma, which generates strong emotions, has caused an unfortunate polarization of a complex, multifaceted issue. The extremists who find regulations abhorrent assert that there is no evidence of global warming. (They are sometimes referred to as deniers or skeptics.) Their opponents, the believers, claim that global warming is underway, and is already causing environmental disasters. For believers, the second dilemma assumes global warming is already contributing to the suffering of the poor and therefore is an urgent priority for everyone. They refuse to accept that, for the many people who are so poor that they have nothing to lose, global warming is not an urgent issue. Dilemmas 1 and 2 call for compromises and hence for an objective assessment of the scientific results. The IPCC reports, which provide such an assessment, are explicit about uncertainties in the available results and hence favor neither the deniers nor the believers. The magnitudes of the uncertainties vary, depending on the time and region under consideration, and depending on whether we focus on temperature, the height of the ocean surface, rainfall or some other parameter.

      The following is a very brief synopsis—a bird's eye view—of the discussion of these topics in the numerous entries of this encyclopedia. This information hopefully provides a basis for the development of an effective response to the threat of global warming.

      TINY FROM AFAR: In our solar system, Earth, third planet from the sun at left, is dwarfed by giants Jupiter and Saturn. The order of the planets starts with Mercury, which is closest to the Sun, then Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and controversial Pluto.

      Let us assume that we are aliens from another galaxy, in search of a habitable planet. On entering this particular solar system, our attention is at first drawn to the large, spectacular planets Jupiter and Saturn which are adorned with splendid rings and many moons. Earth, tiny by comparison, is a faint, blue dot from afar. Closer inspection shows that two of the Earth's main features are chaotically swirling white clouds, and vast oceans that cover nearly 70 percent of the surface. Both are vitally important to the Earth's most impressive feature of all: a great diversity of life forms that require water in liquid form The abundance of liquid water means that, on the Earth, temperatures fluctuate in a relatively narrow range; the Earth, unlike its neighbors Venus and Mars, is neither too warm nor too cold.

      The Earth's main source of energy is the sun, but this planet would be far too cold for most of its inhabitants were it not for its atmosphere, the thin veil of transparent gases that covers the globe. (If the Earth were an apple, its atmosphere would have the thickness of the peel.) This veil, by means of an intricate interplay between photons of light and molecules of air, serves as a shield that provides protection from dangerous ultraviolet rays in sunlight. The atmosphere serves as a parasol that reflects sunlight, thus keeping the planet cool; and as a blanket that traps heat from the Earth's surface, thus keeping us warm. The blanket is the greenhouse effect, which depends not on the two gases nitrogen and oxygen that are most abundant, but on trace gases that account for only a tiny part of the atmosphere, .035 percent in the case of carbon dioxide.

      The most important greenhouse gas is water vapor, which is capable of engaging in escalating tit-for-tats (or positive feedbacks in engineering terms.) If atmospheric temperatures were to increase by a modest amount, then evaporation from the oceans will increase, thus increasing the concentration of water vapor in the atmosphere. The result is an enhanced greenhouse effect that increases temperatures further, causing more evaporation, even higher temperatures, and so on. The consequence could be a runaway greenhouse effect—this is thought to be the reason why Venus has no water today. The Earth was spared this fate because it is further from the sun than Venus, and is sufficiently cool for the air to become saturated with water vapor, in which case clouds form. Clouds present the following question: Is their net effect cooling, because of the sunlight they reflect, or warming because of their greenhouse effect? The answer depends on the type of cloud. Occasional glances at the sky reveal that there are many, many types. Uncertainties about future global warming stem mainly from uncertainties concerning the types of clouds that are likely in a warmer world. Simulating these fantastical, ephemeral objects is the biggest challenge for scientists trying to reproduce climate in computer models.

      SATELLITE VIEW: A photograph from space of a setting sun shows how thin the atmosphere is. If the Earth were an apple, its atmosphere would have the thickness of the peel.

      If the atmosphere were static, we would be confined to a band of midlatitudes, because the tropics would be too hot, the polar regions too cold. Fortunately, the atmosphere has winds that redistribute heat and also moisture, cooling off the lower latitudes, while warming up higher latitudes. The circulation that effects this redistribution includes surface winds that are easterly (westward) in the tropics, where they converge onto the regions of maximum surface temperature at the equator. There the air rises into tall cumulus towers that provide plentiful rain. Aloft, the air flows poleward, cools, and sinks over the subtropical deserts. Some of the air continues further poleward to join the westerly jet streams that are so intense that some bands of latitude are known as the Roaring Forties and the Screaming Fifties. This atmospheric circulation, despite its chaotic aspects that we refer to as weather, creates distinctive climatic zones—jungles and deserts, prairies and savannahs—that permit enormous biodiversity.

      In the tropics, the atmospheric circulation, and hence the pattern of climatic zones, are strongly dependent on patterns of sea surface temperature that influence how much moisture the winds take (evaporate) from the ocean, and then deposit in rain-bearing clouds. The most surprising feature in the sea surface temperature patterns is the presence of very cold surface waters right at the equator in the eastern Pacifie Ocean. (When he visited the Galapagos Islands, Charles Darwin commented on the curiously cold water at the equator where sunlight is most intense.) To explain this we need to explore the oceans, the thin film of water that covers much of the globe.

      The average depth of the ocean, 3.1 miles or 5 kilometers, is negligible in comparison with the radius of the Earth, which is more than 3,700 miles or 6,000 kilometers. Both the atmosphere and ocean are very thin films of fluid, one air, the other water. Measurements made on expeditions from Antarctica to Alaska show that the ocean is composed of a very shallow layer of warm water that floats on a much colder, deep layer. So shallow is the warm layer that, at the equator near the dateline where the surface waters are warmest, the average temperature of a vertical column of water is barely above freezing. An important consequence is that the winds blowing in the right direction can easily expose cold water to the surface by driving oceanic currents in the right direction. The westward trade winds do this along the equator. They drive the warm surface water westward, causing cold water to appear near the Galapagos Islands. Winds parallel to the western coasts of Africa and the Americas, north and south, similarly drive currents that bring cold water to the surface.

      PRECIPITATION MAP: There is a strong relationship between amount of precipitation and ocean temperature. Charles Darwin remarked on the surprisingly cold waters off the Galapagos Islands.
      EARTH LIGHTS FROM SPACE: This map by NASA shows a composite image of lights on Earth, but both the landforms and lights appear brighter than would be visible to an unaided observer in space. Researchers were able to produce this map of lights showing urban surface activity
      BRIGHT LIGHTS, BIG CITY: What becomes remarkably clear in this image is the energy usage in the United States, western Europe, and Japan, as compared to Africa and the rest of the world. The major national and regional contributors to greenhouse gas emissions are evident.

      Some of the oceanic currents are very slow and deep, others are swift and shallow and include the Gulf Stream and Kuroshio—narrow, rivers of warm water that flow poleward. These currents redistribute heat and chemicals, thus determining patterns of sea surface temperature and oceanic climatic zones that are evident in satellite photographs of the distribution of chlorophyll at the surface of the Earth. Chlorophyll is produced by phytoplankton, literally plants that wander. Those plants, and other life forms that depend on them, are most abundant near the ocean surface, because they need light that penetrates only tens of feet or meters below the ocean surface. When that living matter dies, it sinks and decomposes so that the cold, deep ocean is rich in nutrients.

      It follows that ideal conditions for biological productivity—an abundance of light and nutrients—exists where the deep water rises to the surface. These are known as the oceanic upwelling zones, where surface waters are cold, such as off the western coasts of the Americas and Africa. The absence of a layer of warm surface waters around Antarctica makes the Southern Ocean another highly productive zone. Note that the subtropical ocean basins are in effect oceanic deserts with very few plants, because there is practically no exchange between the warm surface waters and the cold water at depth.

      The plants on land and at sea, by means of photosynthesis, capture carbon dioxide from the atmosphere during their growing season, and return it when they die and decay. This continual flow of carbon between the ocean, atmosphere, and biosphere (the assemblage of all life on Earth) causes variations in the atmospheric concentration of carbon dioxide. Many people think of the composition of the atmosphere as fixed, in the way that water in a glass is composed of two parts hydrogen and one part oxygen. In reality the atmospheric composition changes continually because each constituent participates in a biogeochemical cycle. (The best known is the hydrological cycle, which is associated with continual changes in the atmospheric concentration of water vapor.) At present, we are interfering with the carbon cycle by burning fossil fuels, and thus emitting carbon into the atmosphere. The oceans and the plants absorb a large fraction, but much remains in the atmosphere so that the concentration there is rising rapidly.

      JULY AND JANUARY: True color composite satellite maps of the Earth's surface in July (above) and January 2004 (at right) from NASA illustrate the significance of seasonal snowfall.

      The ocean, atmosphere, and biosphere form a complex interacting system capable of generating fluctuations on its own. This is known as natural variability, in contrast to variability forced by daily and seasonal changes in sunlight, or by human-induced changes in the composition of the atmosphere. Daily changes in the weather, the best-known examples of natural variability, are as natural as the swings of a pendulum and would be present even if there were no variations in sunlight. Another natural fluctuation, with a much longer timescale of years rather than days, is the oscillation between El Niño and La Niña in the Pacific Ocean. From a strictly oceanic perspective, these phenomena are associated with changes in sea surface temperatures, in the currents, and so on, that are attributable to changes in the winds. Along the equator, those winds are intense during La Nina, weak during El Niño. Why do the winds change? From a meteorological perspective, the large temperature contrast between the western and eastern equatorial Pacific during La Nina drives intense winds that weaken when the contrast weakens. This circular phenomenon—atmospheric changes are both the cause and consequence of oceanic changes—implies that El Niño and La Niña are consequences of interactions between the ocean and atmosphere.

      ALBEDO EFFECT: Snow-covered regions effectively cool the Earth by reflecting sunlight back into space, and hence changes in the range of snow cover can serve to amplify climate changes.

      We know a great deal about daily changes in weather because we have ample opportunities to study those changes. Over the past few decades, we learned a fair amount about El Niño, because that phenomenon occurred several times during that period. The past centuries and millennia were also characterized by naturally occurring fluctuations, but information about those climate fluctuations is scant, because of the lack of instrumental records. A thousand years ago, the northern Atlantic was so warm that Greenland had a large population, sufficiently large for the Pope to send a bishop.

      That warm period was followed by the frigid Little Ice Age. Those changes were presumably aspects of natural variability, but as yet they are unexplained. Because we know very little about natural variability, it is not possible to determine whether a few unusually warm years, or a few intense hurricanes such as Katrina, or the unusually strong El Niño of 1997, indicate the onset of global warming. Scientists had to search carefully for distinctive patterns, for the “footprints” of global warming, before they could conclude in the 2007 IPCC report that humans activities are affecting the global climate.

      NATURAL FLUCTUATION: With a timescale of years rather than days, the oscillation between El Niño and La Niña in the Pacific Ocean governs weather patterns and storm activity.
      OCEAN CURRENTS: The warm surface currents (red) intertwine with the deep cold currents (blue), creating climate patterns across the Earth. (Robert Simons/NASA)

      The composition of the atmosphere, which strongly influences climate, depends on biogeochemical cycles involving not only the ocean, atmosphere and biosphere, but also the solid Earth. Terra firma is anything but firm; its surface is composed of several slowly moving, nearly rigid plates, on some of which the continents float. This is the surface manifestation of motion deep in the interior of the Earth, where temperatures are very high because of the decay of radioactive material. Earthquakes are common along the plate boundaries, which feature tall mountains where the plates collide, or deep trenches where one plate dives (subducts) beneath another. In regions of subduction, volcanoes are common; that is why the Pacific rim is known as a “ring of fire.” When they erupt, volcanoes emit carbon dioxide into the atmosphere. That gas interacts with water vapor to form an acid that erodes rocks, causing the removal of carbon dioxide from the atmosphere. Hence, the building of mountains—the creation of extensive rock surfaces—promotes the removal of carbon dioxide from the atmosphere. Continental drift therefore affects the atmospheric composition by bringing into play processes that increase, and others that decrease, the concentration of carbon dioxide. Volcanic eruptions contribute to the increase, the building mountains to the decrease. Continental drift affects climate in a more direct manner by changing the distribution of continents. At one time all the continents were together and formed a supercontinent, Pangea, with a northern part known as Laurasia, and a southern Gondwanaland that included the Antarctic continent. With the breakup that started around 250 million years ago, Africa and South America separated to form the Atlantic Ocean. India traveled northward until it collided with Asia, and started creating the Himalayas.

      TEMPERATURE MAP: The areas in dark red with the highest temperatures correlate to the Precipitation Map—regions with the highest precipitation are also the warmest.

      For those interested in global warming, what happened after the demise of the dinosaurs some 65 million years ago is of special interest. At that time, the Earth was far warmer than it is today, so warm that there was no ice on the planet. Palm trees and crocodiles flourished in polar regions, in part because the atmospheric concentration of carbon dioxide was much higher than it is today. Subsequently, the continued drifting of the continents, accompanied by decreases in the atmospheric concentration of carbon dioxide, contributed to the global cooling. (This period is known as the Cenozoic, the age of new animals, specifically mammals.) What caused the Ice Ages? Why did they start 3 million years ago? The answers involve slight changes in sunlight. Sunlight varies daily and seasonally because the Earth rotates on its tilted axis once a day, while orbiting the sun once a year. Additional variations over much longer periods of thousands of years are associated with slight oscillations of the tilt of the axis, which also precesses, while the orbit changes gradually, from a circle into an ellipse, and back to a circle. The moon and several planets cause these Milankovitch cycles, which have been present throughout the Earth's history. The climate fluctuations induced by these sunlight cycles were modest up to 3 million years ago, but then started amplifying. That amplification required positive feedbacks that translated the slight variations in sunlight into Ice Ages. The feedbacks were brought into play by the drifting of the continents. A complex and poorly understood interplay between the slow, erratic drifting of continents, and the regular variations in sunlight, caused the Ice Ages to be absent during some periods, and prominent during others, such as the present.

      The global cooling associated with the drifting of the continents that started 60 million years ago inevitably led to the appearance of glaciers, first on Antarctica, then on northern continents around 3 million years ago. Glaciers, because they are white, reflect sunlight. This deprives the Earth of heat, lowers temperatures, and promotes the growth of glaciers. Hence, the appearance of continental glaciers was one of the feedbacks that amplified the response to Milankovitch variations in sunlight. Trapped in those glaciers are bubbles of air that tell us about past changes in the atmospheric composition, past variations in the atmospheric composition of carbon dioxide. As yet it is not known why the concentration varied, or to what degree the variations contributed to the temperature fluctuations.

      HURRICANE PATHS: A plot of the intensity and paths of hurricanes and typhoons. How global warming will affect the development and strength of storms is a subject of debate and study.
      POTENTIAL FLOODING: This is a topographic map designed to emphasize regions near sea level that could potentially be vulnerable to sea level rise, though over centuries rather than decades.

      Solving the puzzle of the Ice Ages will be a major contribution to our ability to anticipate future climate changes, because the solution will tell us a great deal about the sensitivity of the Earth's climate to changes in the atmospheric concentration of carbon dioxide. In the meanwhile, familiarity with the data can give us a valuable perspective on global warming by giving us a geological context for our activities over the past century. From a geological perspective, the present is a special moment in the history of our planet for at least two reasons. The first is that the Earth is currently in an era of high sensitivity to small disturbances. Starting approximately 3 million years ago, the Earth's response to slight variations in sunlight, the Milankovitch cycles, have included enormous climate fluctuations associated with recurrent Ice Ages. Only some of the feedbacks that are involved have been identified. The second reason why the present is special is that we are currently enjoying the temperates of one of the brief interglacial periods that separate prolonged Ice Ages.

      The previous interglacial was more than 100,000 years ago but, at that time, we humans were few in numbers, and had very limited capabilities. We were ready when the current interglacial started, some 10,000 years ago, and proceeded to advance with astonishing rapidity, inventing agricultures, domesticating certain animals, developing cultures, and building cities. We developed so rapidly that we are now geologic agents, capable of interfering with the processes that make this a habitable planet. For more than a century, we have caused the atmospheric concentration of carbon dioxide to grow exponentially. This, surely, is a time for circumspection and caution.

      HISTORY OF CLIMATE CHANGE: A compound graphic depicts Earth's climate change across the millennia and centuries. Top: Global cooling over the past 60 million years. Middle: Recurrent Ice Ages over the past 600,000 years. Bottom: Rise in temperature and carbon dioxide over the past four centuries. The information in the top panel comes from cores drilled into the ocean floor, where sediments contain remains of primitive organisms that live near the ocean surface. The information in the middle panel comes from Antarctica, where the accumulated snowfall of hundreds of millennia created deep glaciers.
      Maps and Plots Prepared by Robert A. Rohde University of California, Berkeley

      List of Articles

      List of Contributors

      Adler, Ruth, Ohio State University

      Akhtar, Rais, Jawaharlal Nehru University

      Akter, Farhana, King's College, London

      Allmon, Warren D., Paleontological Research Institute

      Andronova, Natasha, University of Michigan

      Araujo, John, US. Centers for Disease Control and Prevention

      Auerbach, Karl, University of Rochester

      Auerbach, Andrea S., Eastern Research Group, Inc.

      Auffhammer, Maximilian, University of California, Berkeley

      Backe, Andrew S., National Science Foundation

      Bader, Barbara, Université Laval

      Bakshi, Bhavik R., Ohio State University

      Ballabrera, Joaquim, Institut de Ciències del Mar Consejo Superior de Investigaciones Cientificas

      Ballamingie, Patricia, Carleton University

      Bardecki, Michal J., Ryerson University

      Barnhill, John H., Independent Scholar

      Beai, Lisa, University of Cape Town

      Beniston, Martin, University of Geneva, Switzerland

      Benson, Nsikak, Covenant University

      Bonds, Constance, U.S. Centers for Disease Control and Prevention

      Berg, Donald J., South Dakota State University

      Berhe, Asmeret Asefaw, University of California, Berkeley

      Bevington, Douglas Loyd, University of California, Santa Cruz

      Boersma, P. Dee, University of Washington

      Bonds, Constance M., U.S. Centers for Disease Control and Prevention

      Borovnik, Maria, Massey University

      Brönnimann, Stefan, ETH Zurich, Switzerland

      Brown, Roger, Western Illinois University

      Bruch, Carl, Environmental Law Institute

      Byun, John, Independent Scholar

      Chaudhury, Moushumi, University of Sussex

      Chew, Matthew K., Arizona State University

      Choi, Jongnam, Western Illinois University

      Choi, Jun-Ki, Ohio State University

      Choi, Woonsup, University of Manitoba

      Chrystal, Abbey E., School of Earth Sciences Ohio State University

      Coelho, Alfredo Manuel, UMR MOISA SupAgro, Montpellier, France

      Coffman, Jennifer Ellen, James Madison University

      Coleman, Jill S. M., Ball State University

      Collins, Timothy, Western Illinois University

      Connelly, Sandra, Rochester Institute of Technology

      Corfield, Justin, Geelong Grammar School, Australia

      Corfield, Robin S., Independent Scholar

      Coughlin, Steven S., U.S. Centers for Disease Control and Prevention

      Crivella, Ellen J., Vermont Law School

      Crompton, Samuel Willard, Independent Scholar

      Crooker, Richard A., Kutztown University

      Cumo, Christopher, Independent Scholar

      de Freitas, C R, University of Auckland

      Delang, Claudio O, Chinese University of Hong Kong

      de Ruitjter, Wilhelmus P.M., University of Cape Town

      de Souza, Lester, Independent Scholar

      Dillow, Robin K., Rotary International Archives

      Dixon, P. Grady, Department of Geosciences, Mississippi State University

      Duffy, Lawrence K., University of Alaska, Fairbanks, Arctic Division, AAAS

      Duffy, Philip B., Lawrence Livermore National Laboratory

      Dutt, Ashok K., University of Akron

      Edmunds, James, Thames Valley University

      Edwards, Richard Milton, University of Wisconsin Colleges

      Ennis, Christopher J., University of Teesside

      Ennis, Harriet, University of York

      Fang, Jiasong, Iowa State University

      Finley-Brook, Mary, University of Richmond

      Foltz, Gregory R., National Oceanic and Atmospheric Administration/Pacific Marine Environmental Laboratory

      Fry, Richard, Wayne State University

      Gabric, Al, Griffith University

      Gellers, Joshua Chad, Columbia University

      Ghezzehei, Teamrat A., Lawrence Berkeley National Laboratory

      Giardina, Christian P., Institute of Pacific Islands Forestry, USDA Forest Service

      Gray, Steven A., Rutgers University

      Greve, Wulf, Independent Scholar

      Grover, Velma I., Natural Resource Consultant

      Gunter, Michael M., Rollins College

      Gutierrez, Maria, International Institute for Sustainable Development

      Hanna, Edward, University of Sheffield

      Hart, Rachelle, Bringham Young University

      Hartmann, Ingrid, Independent Scholar

      Herrera, Fernando, University of California, San Diego

      Hoist, Arthur Matthew, Widener University

      Hope, Pandora, Centre for Australian Weather and Climate Research

      Howe, David V., Rutgers University

      Hume, Douglas William, University of Connecticut

      Hund, Andrew, University of Alaska, Anchorage

      Hurst, Kent, University of Texas at Arlington

      Isherwood, William F., Chinese Academy of Sciences

      Jaggard, Lyn, University of Birmingham

      Jordan, Rebecca C., Rutgers School of Environmental and Biological Sciences

      Kafarowski, Joanna, University of Northern British Columbia

      Kahn, Richard, University of North Dakota

      Kevorkian, Kriss A., Antioch University

      Klever, Robert G., Independent Scholar

      Koslowsky, Robert Karl, Independent Scholar

      Kte'pi, Bill, Independent Scholar

      Laberge, Yves, Université Laval

      Law, Kevin, Marshall University

      Lenschow, Donald H., National Center for Atmospheric Research

      Leopold, Estella B., University of Washington

      Lioubimtseva, Elena, Grand Valley State University

      Lomine, Loykie L., University of Winchester

      Lucarini, Valerio, Department of Physics University of Bologna

      Lutjeharms, Johann R. E., Independent Scholar

      Malilay, Josephine, U.S. Centers for Disease Control and Prevention

      Marchant, Rob, Environment Department University of York

      McManus, Phil, University of Sydney

      Mechoso, C.R., University of California, Los Angeles

      Meier, Ina Christin, University of Göttingen

      Meier, Walter N., National Snow and Ice Data Center University of Colorado

      Merrett, Christopher D., Western Illinois University

      Michaud, Lyn, Independent Scholar

      Michon, Heather K., Independent Scholar

      Miller, DeMond S., Rowan University

      Moni, Monir Hossain, University of Dhaka

      Mooney, Kieran, Department of Geography, Planning and Environment Concordia University

      Moran, Tara, University of Calgary

      Mudie, Peta, Geological Survey of Canada Atlantic

      Mulvaney, Dustin, University of California, Santa Cruz

      Neves-Graca, Katja, Concordia University

      Newman, Lenore, Royal Roads University

      Nicholas, Sandra S., Environmental Law Institute

      Nilton, Renno, University of Michigan

      Novogradec, Ann, York University

      Nursey-Bray, Melissa, Australian Maritime College

      O'Sullivan, John, Gainesville State College

      Ogilvie, Astrid E.J., Institute of Arctic and Alpine Research University of Colorado

      Olanrewaju, Ajayi Oluseyi, Covenant University

      Paleo, Urbano Fra, University of Extremadura

      Palmer, Carl, Independent Scholar

      Palmer, Rob, Research Strategy Training

      Panda, Sudhanshu Sekhar, GIS/Environmental Science Gainesville State College

      Parsons, E.C.M., George Mason University

      Pearce, Joshua M., Clarion University of Pennsylvania

      Pedersen, Anders Branth, National Environmental Research Institute, University of Aarhus, Denmark

      Pendergrass, John, Environmental Law Institute

      Piguet, Etienne, University of Neuchâtel

      Pittermann, Jarmila, University of California, Berkeley

      Polonsky, Alexander Boris, Marine Hydrophysical Institute, Sebastopol

      Poulsen, Christopher J., University of Michigan

      Pringle, Kristy, University of Leeds

      Prono, Luca, University of Nottingham

      Purdy, Elizabeth R., Independent Scholar

      Rands, Gordon P., Western Illinois University

      Rands, Pamela, Western Illinois University

      Reay, Dave S., School of Geosciences University of Edinburgh

      Rebstock, Ginger A., University of Washington

      Renno, Nilton O., University of Michigan

      Rholetter, Wylene, Auburn University

      Ribbens, Barbara Ann, Western Illinois University

      Ribbens, Eric, Western Illinois University

      Richardson, Robert B., Michigan State University

      Rohde, Robert A., University of California, Berkeley

      Rohli, Robert V., Louisiana State University

      Rose, Naomi M., Human Society International

      Ross, Robert M., Paleontological Research Institute

      Rupper, Summer, Brigham Young University

      Sayers, Tyler, Western Illinois University

      Schoolman, Ethan, University of Michigan

      Sewall, Jacob O., Virginia Tech

      Sheeran, Paul, University of Winchester

      Shrivastava, Rahul J., Florida International University

      Simsik, Michael Joseph, U.S. Peace Corps

      Sinclair, Amber, University of Georgia

      Sinclair, Kate E., University of Calgary

      Smith, James N, Atmospheric Chemistry Division, National Center for Atmospheric Research

      Soria, Carlos, Universidad Nacional Mayor de San Marcos

      Srebric, Jelena, Pennsylvania State University

      Staneva, Marieta P., Pennsylvania State University, Altoona

      Steppe, Cecily Natunewicz, United States Naval Academy

      Stroeve, Julienne, University of Colorado

      Tomlin, Teagan, Brigham Young University

      Turner, Derek, Connecticut College

      van Oss, Hendrik G., U.S. Geological Survey

      Voskresenskaya, Elena, Marine Hydrophysical Institute, Sevastopol

      Walsh, John, Shinawatra University

      Warren, Karin, Randolph College

      Waskey, Andrew, Dalton State College

      Whalen, Ken, University of Florida

      Whitehead, Mark, University of Wales, Aberystwyth

      Williams, Akan Bassey, Covenant University

      Winograd, Claudia, University of Illinois at Urbana-Champaign

      Wise, Eruca, University of Arizona

      Wu, Charlene, Johns Hopkins University

      Zimmermann, Petra A., Ball State University

      Chronology

      4.5 billion years ago The Earth, newly formed, had the hottest climate in the planets long history. Temperatures were hot enough to liquefy rock. Radioactive elements in Earth's core generated heat and pressure as they decayed, pushing molten rock toward Earths surface. Volcanoes also brought molten rock to the surface, liberating heat. Volcanoes spewed carbon dioxide into the atmosphere, causing the Greenhouse Effect.

      3.8 billion years ago As the mass of radioactive elements in Earth's core diminished, the climate cooled and the first rock formed. The cooling of the atmosphere liquefied water vapor, which fell to Earth as rain.

      3.5 billion years ago to 3 billion years ago The origin of life enhanced the cooling of the climate, for among the first life were single-celled photosynthetic algae. Like plants, these algae consumed carbon dioxide and exuded oxygen. The reduction of carbon dioxide in the atmosphere weakened the Greenhouse Effect. With the reduction in carbon dioxide, temperatures dropped below freezing, causing the planet's first ice age 3 billion years ago.

      2.9 billion years ago The retreat of the glaciers inaugurated a long period of warm climate. The sun, burning steadily brighter, bathed Earth in its heat. Warm inland seas covered Earth, moderating the climate. Ocean currents circled the globe, spreading warm water from the equator to the poles.

      800 million years ago to 550 million years ago Glaciers covered the oceans as well as the land, killing photosynthetic algae that lived in the ocean. With algae in small numbers they were able to remove only a fraction of carbon dioxide from the atmosphere. With no check on its accumulation, carbon dioxide increased in the atmosphere, causing the Greenhouse Effect. The Greenhouse Effect ended the Late Proterozoic Ice Age roughly 550 million years ago, inaugurating a new warm period.

      350 million years ago to 280 million years ago The lush plant growth of the Carboniferous Era confirmed that the climate was warm and that carbon dioxide, essential for plant growth, was abundant.

      230 million years ago The continents gathered into a single landmass called Pangea. Because it was near the equator, Pangea's climate was tropical.

      135 million years ago to 65 million years ago Temperatures soared 20 degrees Fahrenheit warmer than today's temperatures during the Cretaceous Era. Forests covered Antarctica. Ocean currents again carried warm water to the poles.

      65 million years ago An enormous meteor impacted Earth, ejecting a gigantic cloud of debris and dust. It ignited widespread fires, which pumped ash into the atmosphere. The debris, dust, and ash blocked out much of the sun's light, chilling the climate. So severe was the reversal in climate that the dinosaurs and a large number of marine species, unable to cope with the new conditions, perished.

      55 million years ago to 35 million years ago Temperatures declined 20 degrees F (11 degrees C). Glaciers formed on Antarctica.

      130,000 years ago The climate was again warmer than it is today. The water from melting glaciers flowed to the oceans, raising the sea level 60 ft. (18 m.) higher than it is today.

      100,000 years ago The climate cooled yet again and glaciers once more spread across the continents, plunging Earth into its most recent ice age.

      16,000 to 13,000 years ago The glaciers were in retreat, temperatures rose nearly 15 degrees Fahrenheit.

      12,900 and 11,500 years ago Temperatures during the Younger Dryas fell 50 degrees Fahrenheit in only a decade

      7,000 years ago Temperatures peaked at 2–3 degrees F (1–1.5 degrees C) above current temperatures. The climate remained warm and wet for another 3,000 years.

      1,000 to 1,300 CE. The Medieval Warm Period rewarded peasants with bountiful crops. With food in surplus, human population increased.

      1400 to 1840 The Little Ice Age covered the globe with record cold, large glaciers, and snow. This massive climate change triggered disease, famine, and death. Today, many scientists around the world believe that global warming caused by the Greenhouse Effect will be the fastest warming of the Earth since the termination of the Little Ice Age.

      1824 French mathematician and physicist Jean Baptiste Joseph Fourier established that a buildup of carbon dioxide in Earth's atmosphere warms the climate.

      1859 Irish scientist John Tyndall discovered that some gases block infrared radiation. He suggested that changes in the concentration of the gases could bring climate change.

      1863 Tyndall announced that water vapor is a greenhouse gas.

      1875 British scientist James Croll established that ice and snow reflect sunlight into space and cool the Earth.

      1896 Swedish scientist and Nobel laureate Svente Arrhenius coined the phrase Greenhouse Effect and predicted that the Earth's climate is slowly warming. Arrhenius published the first calculation of global warming from human-induced emissions of carbon dioxide.

      1897 British scientist Thomas C. Chamberlin established the link between ice ages and low concentrations of carbon dioxide and between warm climates and high concentrations of carbon dioxide.

      1920 to 1925 The opening of Texas and Persian Gulf oil fields inaugurated an era of cheap energy. The burning of petroleum releases greenhouse gases into the atmosphere, warming the climate.

      1924 German climatologist and geologist Alfred Wegener posited that the continents move slowly across Earth. When they are near the equator their climate is warm, while near the poles their climate is cold.

      1930 Serbian geophysicist Milutin Milankovitch proposed that changes in the eccentricity of Earth's orbit cause climate change, including ice ages.

      1932 Meteorologist W.J. Humphreys elaborated the conditions for a return to an ice age. He believed that an increase in debris in the atmosphere and the reflection of sunlight by ice and snow might return Earth to an ice age.

      1933 to 1935 The drought of the 1930s created dust storms on the Plains. The worst dust storm of the Dust Bowl gripped the Plains on what later becomes known as Black Sunday. President Franklin Roosevelt established the Soil Erosion Service in response to the devastation of the Dust Bowl and as a part of his New Deal programs to create jobs. The Soil Erosion Service was the predecessor of the Soil Conservation Service established in 1935, which is known today as the Natural Resources Conservation Service (NCRS).

      1937 Royal Meteorological Society president George Simpson posited that an increase in solar radiation might cause an ice age. By warming the poles more than high altitudes, the increase in solar radiation would intensify the circulation of the atmosphere, carrying moisture to high latitudes, where it would fall as snow. If enough snow accumulated, a new ice age would ensue.

      1938 Amateur scientist G.S. Callendar recorded an increase in temperatures in the Artie and posited the Greenhouse Effect as the cause.

      1939 Simpson announced that the atmosphere seems to keep the climate nearly constant by regulating the amount of clouds. The more clouds, the lower the temperature, and the fewer clouds, the warmer the temperature.

      1940 Many scientists dismissed Callendar s claims. However, in response to his theory scientists began to develop new ways to measure the history of and current conditions of Earth's climate.

      1945 The U.S. Office of Naval Research began generous funding of many fields of science, some of them useful for understanding climate change.

      1950 American scientist Charles E Brooks announced that Artie ice might be melting and that, once started, the melting might shrink the ice to a vestige of its former size and raise sea levels.

      1950s The development of new technology led to an increased awareness of global warming and the Greenhouse Effect. Researchers began to show that the level of carbon dioxide in the atmosphere was rising each year and people became concerned about pollution.

      1956 American scientists Maurice Ewing and William Donn posited that the last ice age had rapidly descended on Earth when the North Pole wandered into the Arctic Ocean, triggering the accumulation of snow and ice in this region. American scientist Norman Phillips produces a somewhat realistic computer model of the global atmosphere. Canadian physicist Gilbert Plass calculated that adding carbon dioxide to the atmosphere would affect the radiation balance.

      1957 Launch of Soviet Sputnik satellite. Cold War concerns support the 1957–58 International Geophysical Year, bringing new funding and coordination to climate studies. U.S. oceanographer Roger Revelle warned that humanity is conducting a “large-scale geophysical experiment” on the planet by releasing greenhouse gases.

      1958 Astronomers identified the Greenhouse Effect on Venus, where temperatures are far above the boiling point of water.

      1960 A report found that global temperatures had declined since the early 1940s. American scientist Charles David Keeling set up the first continuous monitoring of carbon dioxide levels in the atmosphere. Keeling soon finds a regular rise in temperatures.

      1961 Soviet meteorologist Mikhail Budyko warned that the burning of fossil fuels, and the attendant accumulation of greenhouse gases in the atmosphere, would warm the planet.

      1963 Fritz Moller calculated that a doubling of carbon dioxide in the atmosphere might increase temperatures 50 degrees Fahrenheit.

      1965 Climatologists gather in Boulder, Colorado, to discuss climate change. Edward Lorenz and others point out the chaotic nature of the climate system and the possibility of sudden shifts.

      1966 Italian scientist Cesare Emiliani s analysis of deep-sea cores showed that the timing of ice ages was set by small orbital shifts, suggesting that the climate system is sensitive to small changes.

      1967 The International Global Atmospheric Research Program was established, mainly to gather data for better short-range weather prediction. Computer modelers Syukuro Manabe and Richard Wetherald predicted that an increase in the number of clouds might hold heat in the atmosphere and so increase temperatures.

      1968 Mikhail Budyko derived two mathematical models. One predicted an increase in temperatures due to the Greenhouse Effect. The other predicted the return of the ice age. Budyko favored the first model. Other models were also contradictory. Studies suggested that the Antarctic ice sheets might collapse, raising sea levels catastrophically

      1969 American climatologist William Sellers predicted that a 2 percent decrease in solar radiation, whether from a fluctuation in solar output or the result of debris in the air, might plunge Earth into a new ice age. Like Budyko, Sellers feared that the burning of fossil fuels might warm Earth. Nimbus III satellite begins to provide comprehensive global atmospheric temperature measurements.

      1970 The First Earth Day. The environmental movement attains strong influence, spreading concern about global degradation. The creation of the U.S. National Oceanic and Atmospheric Administration was the world's leading funder of climate research. Aerosols from human activity were increasing in the atmosphere. American scientist Reid Bryson claimed they counteracted global warming and may actually cool the Earth.

      1971 The Study of Man's Impact on Climate (SMIC), a conference of leading scientists, reported a danger of rapid and serious global change causedby humans and called for an organized research effort. The American Mariner 9 spacecraft found a great dust storm warming the atmosphere of Mars along with indications of a radically different climate in the planet's past.

      1972 Budyko predicted that a 50 percent increase in greenhouse gases in the atmosphere might raise temperatures enough to melt all the ice on Earth, whereas a 50 percent reduction might plunge Earth into an ice age. Budyko favored the first scenario and predicted that temperatures might rise enough to melt all the ice by 2050. Ice cores and other evidence showed that the climate changed in the past in the space of 1,000 years or so, especially around 11,000 years ago.

      1972 to 1974 Serious droughts and other unusual weather since 1972 increased scientific and public concern about climate change, with cooling from aerosols suspected to be as likely as warming. Journalists wrote about ice ages.

      1975 Concern about the environmental effects of airplanes led to investigations of trace gases in the stratosphere and the discovery of danger to the ozone layer. Manabe and collaborators produced complex but plausible, computer models, which predicted an increase of several degrees Fahrenheit for a doubling of carbon dioxide.

      1975 to 1976 Studies showed that chlorofluorocarbons (CFCs) (1975) and also methane and ozone (1976) contribute to the Greenhouse Effect. Deep-sea cores show a dominating influence from 100,000-years ago. Milankovitch's prediction of orbital changes emphasized the role of feedbacks. Deforestation and other ecosystem changes were recognized as major factors in the future of the climate. American meteorologist Amos Eddy showed that the absence of sunspots in past centuries corresponded with cold periods.

      1977 Scientific opinion tended to converge on global warming, not cooling, as the chief climatic risk in next century.

      1978 Attempts to coordinate climate research in United States ended with an inadequate National Climate Program Act, accompanied by rapid, but temporary, growth in funding. American scientist James Hansen predicted that the accumulation of aerosol particles in the atmosphere might reflect sunlight back into space and so reduce temperatures.

      1979 The second oil energy crisis. A strengthened environmental movement encouraged the development of renewable energy sources and the reduction of technologies that burn fossil fuels. The U.S. National Academy of Sciences estimated that a doubling of carbon dioxide might increase temperatures 35 to 40 degrees Fahrenheit. The World Climate Research Program was launched to coordinate international research on climate change.

      1980 The election of President Ronald Reagan caused a backlash against the environmental movement. Political conservatism is linked to skepticism about global warming. Some scientists predicted greenhouse warming should be measurable by about the year 2000.

      1982 Greenland ice cores revealed temperature oscillations over a single century in the distant past. Strong global warming since the mid-1970s was reported, with 1981 the warmest year on record.

      1983 Reports from U.S. National Academy of Sciences and Environmental Protection Agency spark conflict, as greenhouse warming becomes prominent in mainstream politics.

      1984 Theories about global warming and the Greenhouse Effect became more prevalent, gaining attention from the mass media. However, many people believe the threat is not imminent and some doubt that global climate change is a danger.

      1985 The Center for Atmospheric Science Director Veerabhadran Ramanathan and collaborators announced that methane and other trace gases together could bring as much global warming as carbon dioxide itself. The Villach conference in Indonesia declared consensus among experts that some global warming seems inevitable and called on governments to consider international agreements to restrict emissions of greenhouse gases. Antarctic ice cores show that carbon dioxide and temperature went up and down together through past ice ages, pointing to powerful biological and geochemical feedbacks. American scientist Wallace Broecker speculated that a reorganization of North Atlantic Ocean circulation could bring swift and radical climate change.

      1987 This was the warmest year since humans began to keep records. The 1980s were the hottest decade on record, with seven of the eight warmest years recorded up to 1990. Even the coldest years in the 1980s were warmer than the warmest years of the 1880s. The Montreal Protocol of the Vienna Convention imposed international restrictions on the emission of ozone-destroying gases.

      1988 Global warming attracts worldwide headlines after scientists at Congressional hearings in Washington, D.C., blamed the U.S. drought on its influence. A meeting of climate scientists in Toronto subsequently called for 20 percent cuts in global carbon dioxide emissions by 2005. The United Nations set up the Intergovernmental Panel on Climate Change (IPCC) to analyze and report on scientific findings. News media coverage of global warming leapt upward following record heat and droughts. The Toronto conference called for strict, specific limits on greenhouse gas emissions. British Prime Minister Margaret Thatcher is the first major leader to call for action. Ice-core and biology studies confirmed that living ecosystems give climate feedback by way of methane, which could accelerate global warming. The level of carbon dioxide in the atmosphere reached 350 parts per million.

      1989 Fossil-fuel suppliers and other industries formed the Global Climate Coalition in the United States to lobby politicians and convince the media and public that climate science is too uncertain to justify action.

      1990 American meteorologist Richard Lindzen predicted that an increase in carbon dioxide in the atmosphere might not cause a concomitant increase in water vapor. Consequently, the Greenhouse Effect might be less severe than some were forecasting. The first IPCC report stated that the world has been warming and continued warming seems likely in the future. Industry lobbyists and some scientists disputed the tentative conclusions.

      1991 Mount Pinatubo erupted. Hansen predicted that the eruption would cool Earth, verifying (by 1995) computer models of aerosol effects. Global warming skeptics emphasized research indicating that a significant part of 20th-century temperature change was due to solar influences. Studies from 55 million years ago show the possibility of the eruption of methane from the seabed causing enormous warming.

      1992 A conference in Rio de Janeiro produced the United Nations Framework Convention on Climate Change, but the United States blocked calls for serious action. The study of ancient climates revealed climate sensitivity in the same range as predicted by computer models.

      1993 Greenland ice cores suggested that great climate changes (at least on a regional scale) could occur in the timespan of a single decade.

      1995 The second IPCC report detected the “signature” of human-caused Greenhouse Effect warming, declaring that serious warming is likely in the coming century. Reports of the breaking up of the Antarctic ice sheets and other signs of current warming in polar regions began to affect public opinion.

      1997 Japanese automobile manufacturer Toyota introduces the Prius in Japan, the first mass-marketed electric hybrid car. Engineers progressed in the design of large wind turbines and other energy alternatives. An international conference in Japan produced the Kyoto Protocol, setting targets to reduce greenhouse gas emissions—if enough nations would approve and sign the treaty.

      1998 The warmest year on record globally averaged (1995, 1997, and 2001–2006 were near the same level). Borehole data confirmed extraordinary warming trend. Qualms about arbitrariness in computer models diminish as teams model ice-age climate and dispense with special adjustments to reproduce current climate.

      1999 A National Academy Panel dismissed criticism that satellite measurements showed no warming. V. Ramanathan detected massive “brown cloud” of aerosols from South Asia.

      2000 The Global Climate Coalition dissolved as many corporations grappled with the threat of warming, but the oil lobby convinced the U.S. administration to deny the problem. Various studies emphasized variability and the importance of biological feedbacks in the carbon cycle that are liable to accelerate warming.

      2001 The Third IPCC report stated that global warming, unprecedented since the end of last ice age, is “very likely,” with possible severe surprises. The National Academy panel marked a “paradigm shift” in scientific recognition of the risk of abrupt climate change (decade-scale). Warming is observed in ocean basins. These observations match computer models, giving a clear signature of Greenhouse Effect.

      2002 Studies found surprisingly strong “global dimming,” due to pollution. This factor had retarded greenhouse warming, but dimming is now decreasing.

      2003 Numerous observations raised concern that the collapse of ice sheets (West Antarctica, Greenland) might raise sea levels faster than most had believed. A deadly summer heat wave in Europe deepens divergence between European and U.S. public opinion.

      2004 In a controversy over temperature data covering the past millennium, most scientists concluded that climate variations were substantial, but not comparable to post-1980 warming. The first major books, movies and artwork feature global warming.

      2005 The Kyoto Treaty, signed, by all major industrial nations except the United States, took effect. Work to retard greenhouse emissions accelerated in Japan, Western Europe, U.S. regional governments, and corporations. Hurricane Katrina and other major tropical storms spurred debate over the impact of global warming on storm intensity.

      2006 An Inconvenient Truth premiered at the 2006 Sundance Film Festival and opened in New York and Los Angeles on May 24, 2006, earning $49 million.

      2007 The fourth IPCC report warned that serious effects of warming have become evident. The cost of reducing emissions would be far less than the damage they will cause. Al Gore shared the Nobel Peace Prize for his efforts to spread knowledge about global warming. The level of carbon dioxide in the atmosphere reaches 382 parts per million.

      Christopher Cumo Independent Scholar, & Fernando Herrera University of California, San Diego
    • Resource Guide

      Resource guide
      Books

      Abrahamson, D.E. (ed.). The Challenge of Global Warming (Island Press, 1989)

      Adger, N., et al. Climate Change 2007: Impacts, Adaptation and Vulnerability Working Group II (Intergovernmental Panel on Climate Change, 2007)

      Aguado, E., and Burt, James E. Understanding Weather and Climate (Prentice Hall, 2006)

      Ahrens, C. Donald. Meteorology Today (Thomson Brooks/Cole, 2007)

      Archer, David. Global Warming: Understanding the Forecast (Blackwell Publishing, 2007)

      Attneld, Robin. Environmental Ethics: An Overview for the Twenty-First Century (Polity, 2003)

      Bailey, R.A., Clark, H.M., Ferris, J.R, Krause, S., and Strong, R.L. Chemistry of the Environment (Academic Press, 2002)

      Baumert, Kevin, Pershing, Jonathan, Herzog, Timothy, and Markoff, Matthew. Climate Data: Insight and Observations (Pew Center on Global Climate Change, 2004)

      Beatley, Timothy. Green Urbanism: Learning from European Cities (Island Press, 1999)

      Brennan, Scott, and Withgott, Jay H. Environment: The Science Behind the Stories (Pearson Education, Inc., 2004)

      Burton, I., Diringer, N., and Smith, J. Adaptation to Climate Change: International Policy Options (Pew Center on Global Climate Change, 2006)

      Ciambrone, David F. Environmental Life Cycle Analysis (CRC, 1997)

      Consultative Group on International Agricultural Research. Global Climate Change: Can Agriculture Cope? (CGIAR, 2007)

      Coward, Harold, and Hurka, Thomas, (eds.). Ethics and Climate Change: The Greenhouse Effect (Laurier Press, 1993)

      Cudworth, Erica. Environment and Society (Routledge, 2003)

      Curran, Mary Ann. Environmental Life-Cycle Assessment (McGraw-Hill, 1996)

      Dardo, Mario. Nobel Laureates and Twentieth-Century Physics (Cambridge University Press, 2004)

      Dryzek, John. The Politics of the Earth: Environmental Discourses (Oxford University Press, 1997)

      Dunne, Thomas, and Leopold, Luna B. Water in Environmental Planning (W.H. Freeman and Company, 1978)

      Energy Information Administration, Impact of the Kyoto Protocol on US. Energy Markets and Economic Activity (U.S. DOE, 1998)

      Feenstra, J., Burton, I., Smith, J.B., and Toi, R. (eds.). Handbook on Methods for Climate Change Impact Assessment and Adaptation Strategies (United Nations Environment Programme and Institute for Environmental Studies, 1998)

      Frakes, Lawrence. Climate Throughout Geologic Time (Elsevier/North-Holland, 1979)

      Frederick, Kenneth D., and Gleick, Peter H. Water and Global Climate Change: Potential Impacts on U.S. Water Resources (Pew Center on Global Change, 1999)

      Gasch, Robert, and Twele, Jochen (eds.). Wind Power Plants: Fundamentals, Design, Construction and Operation (Earthscan Publications Ltd., 2004)

      Gipe, Paul. Wind Power, Revised Edition: Renewable Energy for Home, Farm, and Business (Chelsea Green Publishing Company, 2004)

      Gordon, David. Green Cities: Ecologically Sound Approaches to Urban Space (Black Rose Books Ltd., 1990)

      Gottlieb, Roger. Forcing the Spring: The Transformation of the American Environmental Movement (Island Press, 1993)

      Graedel, Thomas. Atmosphere, Climate and Change (W. H. Freeman, 1995)

      Hart, David M. The Forged Consensus: Science, Technology, and Economic Policy in the United States (Princeton University Press, 1998)

      Hartmann, Dennis L. Global Physical Climatology (Academic Press, 1994)

      Harvey, L. D. Danny. Climate and Global Environmental Change (Prentice-Hall, 2000)

      Hay, Peter. Main Currents in Western Environmental Thought (Indiana University Press, 2002)

      Held, D., McGrew, A., Goldblatt, D, and Peraton, J. Global Transformations: Politics, Economics, Culture (Cambridge Polity Press, 1999)

      Hughes, Donald J. An Environmental History of the World: Humanity's Changing Role in the Community of Life (Routledge, 2001)

      Intergovernmental Panel on Climate Change (IPCC). Climate Change, Contribution of Working Group I to the Third Assessment Report (Cambridge University Press, 2001)

      IPCC. Climate Change 1994, Radiative Forcing of Climate Change (Cambridge University Press, 1995)

      IPCC. Climate Change 1995, The Science of Climate Change (Cambridge University Press, 1996)

      IPCC. Climate Change 2001: The Scientific Basis (Cambridge University Press, 2001)

      IPCC. Climate Change 2007: The Physical Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (Cambridge University Press, 2007)

      Jain, R.L., Urban, L.V., Stacey, G.S., and Baibach, H. Environmental Assessment, 2nd ed. (McGraw-Hill, 2002)

      Jenks, Mike, and Dempsey, Nicola. Future Forms and Design for Sustainable Cities (Architectural Press, 2005)

      Kendrew, Wilfrid. The Climates of the Continents (Clarendon Press, 1961)

      Kiely, Gerard. Environmental Engineering (McGraw-Hill, 1996)

      Krech, Shepard, McNeill, John Robert, and Merchant, Carolyn. Encyclopedia of World Environmental History (Routledge, 2004)

      Leroy, Francis (ed). A Century of Nobel Prize Recipients: Chemistry, Physics, and Medicine (Neurological Disease and Therapy) (CRC, 2003)

      Linacre, Edward, and Geerts, Bart. Climates and Weather Explained (Routledge, 1997)

      Maroto, M., and Valer, M. (eds). Environmental Challenges and Greenhouse Gas Control for Fossil Fuel Utilization in the 21st Century (Kluwer Academic/Plenum Publishers, 2002)

      Masters, G.M. Introduction to Environmental Engineering and Science, 2nd ed. (Prentice-Hall, New Jersey, 1990)

      McNeill, John Robert. Something New Under the Sun. An Environmental History of the Twentieth Century World (Norton, 2000)

      Merchant, Carolyn (ed). Major Problems in American Environmental History, 2nd ed. (Houghton Mifflin, 2005)

      Moran, Emilio F. People and Nature. An Introduction to Human Ecological Relations (Blackwell Publishing, 2006)

      Oxfam. Adapting to Climate Change, What's Needed in Poor Countries and Who Should Pay, (Oxfam Briefing Paper, V.104, 2007)

      Petty, G.W. A First Course in Atmospheric Radiation (Sundog Publishing, 2004)

      Phelps, Edmund. Private Wants and Public Needs. (W.W. Norton & Company Inc., 1962)

      Ponting, Clive. A Green History of the World. The Environment and the Collapse of Great Civilizations (Penguin, 1991)

      Rampino, Michael R. Climate: History, Periodicity, and Predictability (Van Nostrand Reinhold, 1987)

      Raupach, M.R., Marland, G., Ciais, P., Quéré, J. C. Le, Canadell, G., Klepper, G., and Field, C. B. Global and Regional Drivers of Accelerating CO2 Emissions (PNAS, 2007)

      Register, Richard. Ecocities: Rebuilding Cities in Balance With Nature (New Society, 2006)

      Richards, John E The Unending Frontier: An Environmental History of the Early Modern World (University of California Press, 2003)

      Robinson, Peter, and Henderson-Sellers, Ann. Contemporary Climatology (Prentice-Hall, 1999)

      Sawyer, C.N, McCarty, PL., and Parkin, G.E Chemistry for Environmental Engineering and Science, 5th ed. (McGraw-Hill, 2003)

      Shanley, Robert A. Presidential Influence and Climate Change (Greenwood Press, 1992)

      Siedler, Gerold, Church, John, and Gould, John (eds). Ocean Circulation and Climate: Observing and Modelling the Global Ocean (Academic Press, 2001)

      Singer, S. Fred, and Avery, Dennis T. Unstoppable Global Warming: Every 1,500 Years (Rowman and Littleneld, 2007)

      Singh, Ram Babu. Urban Sustainability in the Context of Global Change: Towards Promoting Healthy and Green Cities (Science Publishers, 2001)

      Solomon, S., Qin, D., Manning, M., Chen, Z., Marquis, M., Avery, K.B., Tignor M., and Miller, H.L. (eds). Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (Cambridge University Press, 2007)

      Spray, Sharon. Global Climate Change (Rowman & Littleneld, 2002)

      Stern, Nicholas. The Economics of Climate Change: The Stern Review (Cambridge University Press, 2007)

      Stow, Dorrik. Oceans: An Illustrated Reference (University of Chicago Press, 2005)

      Szasz, Andrew. EcoPopulism: Toxic Waste and the Movement for Environmental Justice (University of Minnesota Press, 1994)

      Udall, Stewart L. The Quiet Crisis (Holt, Rinehart and Winston, 1963)

      United Nations Framework Convention on Climate Change. An Introduction to the Kyoto Protocol Compliance Mechanism (UNFCC, 2006)

      Viessman, Warren Jr., and Lewis, Gary L. Introduction to Hydrology (Prentice Hall, 2003)

      Weart, Spencer. The Discovery of Global Warming (Harvard University Press, 2004)

      Weir, Gary E. Ocean in Common: American Naval Officers, Scientists, and the Ocean Environment (Texas A&M University Military History Series) (Texas A&M University Press, 2001)

      Williams, Mary E. Global Warming: An Opposing Viewpoints Guide (Greenhaven Press, 2006)

      Wise/TranTolo. Bioremediation of Contaminated Soils (Environmental Science and Pollution Control) (CRC, 2000)

      Worster, Donald. Nature's Economy: A History of Ecological Ideas (Cambridge University Press, 1994)

      Yamin, Farhana, and Depledge, Joanna. The International Climate Change Regime: A Guide to Rules, Institutions and Procedures (Cambridge University Press, 2004)

      Yoshino, Masatoshi. Climates and Societies: A Climatological Perspective (Kluwer Academic Publishers, 1997)

      Articles

      Bates, Diane. “Environmental Refugees? Classifyng Human Migrations Caused by Environmental Change.” Population and Environment (v. 23/5, May 2002)

      Bindoff, N, Willebrand, V., Artale, A., Cazenave, J., Gregory, S., Gulev, K., Hanawa, C, Quéré, S. Le, Levitus, Y, Nojiri, C, Shum, L., Talley, A., and Unnikrishnan, A. “Observations: Oceanic Climate Change and Sea Level”, in Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., Qin, D., Manning, M., Chen, Z., Marquis, M., Avery, K., Tignor, M., and Miller, H.L. (eds.)], (Cambridge University Press, 2007)

      Brown, Donald. “The ethical dimensions of global environmental issues.” Daedalus (2001, pp. 59–77)

      Bryden, Harry L., Longworth, Hannah R., and Cunningham, Stuart A. “Slowing of the Atlantic Meridional Overturning Circulation at 25° N,” Nature (v.438, Dec. 2005)

      Caldeira, Ken, and Wickett, Michael E. “Anthropogenic carbon and ocean pH.” Nature (v.425/6956, September 2003)

      Coughlin, Steven S. “Educational intervention approaches to ameliorate adverse public health and environmental effects from global warming,” Ethics in Science and Environmental Politics (2006, pp. 13–14)

      Crowley, T.J. “Causes of climate change over the past 1000 years.” Science (v.289, pp. 270–277)

      Dybas, Cheryl. “Increase in Rainfall Variability Related to Global Climate Change.” Earth Observatory, NASA (December 12, 2002)

      Ganopolski, A. and Rahmstorf, S. “Rapid changes of glacial climate simulated in a coupled climate model.” Nature (v.409, pp. 153–158, 2001)

      Gardiner, Stephen. “Ethics and global climate change.” Ethics (2004, pp. 555–600)

      Gordon, Arnold L. “Inter-ocean Exchange of Thermocline Water.” Journal of Geophysical Research (v.91,1986)

      Guha, Ramachandra. “Radical American Environmentalism and Wilderness Preservation: A Third World Critique.” Environmental Ethics, Vol. 11, No.l (Spring 1989, pp. 71–83)

      Haque, C, and Burton, I. “Adaptation Options Strategies for Hazards and Vulnerability Mitigation An international Perspective”, (Mitigation and Adaptation Strategies for Global Change, (v. 10, 2005)

      Hay, J., and Mimura, N. “Sea Level Rise: Implications for water Resources Management.” Mitigation and Adaptation Strategies for Global Change. (v. 10, 2005)

      Keeling, Charles David. “Is Carbon Dioxide from Fossil Fuels Changing Man's Environment?” Proceedings of the American Philosophical Society (v.114/1: 10–17, 1970)

      McCarthy, Michael. “Charles David Keeling-Climate Scientist Who First Charted the Rise of Greenhouse Gases,” The Independent. (June 27, p. 32, 2005)

      Meier, Mark F, Dyurgerov, Mark, Ursula, Rick, O'Neel, Shad, Pfeffer, W. Tad, Anderson, Robert, Anderson, Suzanne, and Glazovsky, Andrey “Glaciers Dominate Eustatic Sea-Level Rise in the 21st Century.” Science (v.298/5602, December, 2002)

      Mirza, M. M. Q., Warrick, R. A. and Ericksen, N. J. “The Implications of Climate Change on Floods of the Ganges, Brahmaputra and Meghna Rivers in Bangladesh.” Climate Change. (v.57(3), pp. 287–318, 2003)

      Myhre, M., Highwood, E.J., Shine, K.P. and Stordal, F. “New estimates of radiative forcing due to well mixed greenhouse gases,” Geophysical Research Letters (v.25(14), pp. 2715–18, 1998)

      Neumann, James, Yohe, Gary, Nicholls, Robert and Manion, Michelle. Sea-Level Rise & Global Climate Change: A Review of Impacts to U.S. Coasts (Pew Center on Global Climate Change, 2000)

      Ormerod, WG., Ferund, P., and Smith, A. “Ocean Storage of CO2.” (IEA Greenhouse Gas R&D Program, Cheltenham, UK, 2002)

      Poulsen, C.J., Seidov, D., Barron, E.J., and Peterson, W.H. “The Impact of Paleogeographic Evolution on the Surface Oceanic Circulation and the Marine Environment Within the Mid-Cretaceous Tethys.” (Paleoceanog, 13, 546–559)

      Randerson, James. “Should governments play politics with science?” New Scientist, 184.2468 (10/9/2004) 12–14

      Schubert, C. “Global Warming Debate Gets Hotter,” Science News, 159.24 (06/16/2001), 372

      Simmonds, Mark P., and Isaac, Steven J. “The Impacts of Climate Change on Marine Mammals: Early Signs of Significant Problems”, Oryx (v.41, 2007, pp.19–26)

      Supreme Court of the United States, Opinion of the Court: Commonwealth of Massachusetts, et al., v. U.S. Environmental Protection Agency, et al. (549 U.S. No. 05.1120, 2007)

      UNESCO. “Changes in Climate.” Arid Zone Research (No. 20,1963)

      Periodicals

      Energy and Environment - Multi-Science Publishing

      Environmental Ethics - Center for Environmental Philosophy

      Environmental Justice: Issues, Policies, and Solutions Environmental Law - Oxford University Press

      Environmental Management - Academic Press

      Environmental Politics - Frank Cass

      Environmental Science and Technology - Center for Environment and Energy Research and Studies

      EPA Journal - Environmental Planning Agency

      Global Environmental Change - Royal Society of Chemistry

      Global Environment Politics - MIT Press

      Hazardous Waste - BPI News

      Journal of Environmental Economics and Management - Academic Press

      Journal of Environmental Education - Heldref Education

      Journal of Environmental Management - Academic Press

      Journal of Environment and Development - SAGE Publications

      Journal of Forestry - Oxford University Press

      Journal of Geochemical Exploration - Elsevier Science

      Journal of Geophysical Research - American Geophysical Union

      National Geographic - National Geographic Society

      Nature - Palgrave Macmillan

      Oryx - Fauna and Flora International

      Paleoceanography - American Geophysical Union

      Proceedings of the American Philosophical Society - The American Philosophical Society

      Science Trends in Ecology and Evolution - Oxford University Press

      Glossary

      Glossary
      A

      Acid Deposition Acidic aerosols in the atmosphere are removed from the atmosphere by wet deposition (rain, snow, fog) or dry deposition (particles sticking to vegetation). Acidic aerosols are present in the atmosphere primarily due to discharges of gaseous sulfur oxides (sulfur dioxide) and nitrogen oxides.

      Aerosol A collection of airborne solid or liquid particles, with a typical size between 0.01 and 10 micrometers (μm) and residing in the atmosphere for at least several hours. Aerosols may be of either natural or anthropogenic origin. Aerosols may influence climate in two ways: directly through scattering and absorbing radiation, and indirectly through acting as condensation nuclei for cloud formation or modifying the optical properties and lifetime of clouds.

      Afforestation The planting of new forests on land which historically had been covered by forest.

      Albedo The fraction of solar radiation reflected by a surface or object, often expressed as a percentage. Most snow-covered surfaces have a high albedo; the albedo of soils ranges from high to low; vegetation covered surfaces and oceans have a low albedo. The Earths albedo varies mainly through varying cloudiness, snow, ice, leaf area, and land cover changes.

      Alleroed A village in Denmark whose name is used for a warm period at the end of the last glacial.

      Alliance of Small Island States (AOSIS) The group of Pacific and Caribbean nations who call for relatively fast action by developed nations to reduce greenhouse gas emissions. The AOSIS countries fear the effects of rising sea levels and increased storm activity predicted to accompany global warming. Its plan is to hold Annex I Parties to a 20 percent reduction in carbon dioxide emissions by 2005.

      Allometric Equation An equation that uses known growth measurements to estimate related unknown growth measurements.

      Alternative Energy Energy derived from nontraditional sources (e.g., compressed natural gas, solar, hydroelectric, wind, and others).

      Annex I Parties Industrialized countries that, as parties to the Framework Convention on Climate Change, have pledged to reduce their greenhouse gas emissions by the year 2000 to 1990 levels. Annex I Parties consist of countries belonging to the Organisation for Economic Cooperation and Development (OECD) and countries designated as Economies-in-Transition.

      Anthropogenic Made by people or resulting from human activities. Usually used in the context of emissions that are produced as a result of human activities.

      Atmosphere The gaseous envelope surrounding the Earth. The dry atmosphere consists almost entirely of nitrogen (78.1 percent volume mixing ratio) and oxygen (20.9 percent volume mixing ratio), together with a number of trace gases, such as argon (0.93 percent volume mixing ratio), helium, radiatively active greenhouse gases such as carbon dioxide (0.035 percent volume mixing ratio), and ozone. In addition the atmosphere contains water vapor, whose amount is highly variable but typically 1 percent volume mixing ratio. The atmosphere also contains clouds and aerosols. The atmosphere can be divided into a number of layers according to its mixing or chemical characteristics, generally determined by its thermal properties (temperature). The layer nearest the Earth is the troposphere, which reaches up to an altitude of about about 5 mi. (8 km) in the polar regions and up to nearly 11 mi. (17 km) above the equator. The stratosphere, which reaches to an altitude of about 31 mi. (50 km.) lies atop the troposphere. The msosphere which extends up to 50–56 mi. (80–90 km.) is atop the stratosphere, and finally, the thermosphere, or ionosphere, gradually diminishes and forms a fuzzy border with outer space.

      Atmospheric Lifetime The lifetime of a greenhouse gas refers to the approximate amount of time it would take for the anthropogenic increment to an atmospheric pollutant concentration to return to its natural level (assuming emissions cease) as a result of either being converted to another chemical compound or being taken out of the atmosphere via a sink. This time depends on the pollutants sources and sinks as well as its reactivity. The lifetime of a pollutant is often considered in conjunction with the mixing of pollutants in the atmosphere; a long lifetime will allow the pollutant to mix throughout the atmosphere. Average lifetimes can vary from about a week (sulfate aerosols) to more than a century (chlorofluorocarbons [CFCs], carbon dioxide).

      B

      Baseline Emissions The emissions that would occur without policy intervention (in a business-as-usual scenario). Baseline estimates are needed to determine the effectiveness of emissions reduction programs.

      Berlin Mandate A ruling negotiated at the first Conference of the Parties (COP 1), which took place in March, 1995, concluding that the present commitments under the Framework Convention on Climate Change are not adequate. Under the Framework Convention, developed countries pledged to take measures aimed at returning their greenhouse gas emissions to 1990 levels by the year 2000.

      Biogeochemical Cycle The chemical interactions that take place among of key chemical constituents essential to life, such as carbon, nitrogen, oxygen, and phosphorus.

      Biomass Organic nonfossil materials that are biological in origin, including organic material (both living and dead) from above and below ground, for example, trees, plants, crops, roots, and animals and animal waste.

      Biomass Energy Energy produced by combusting renewable biomass materials such as wood. The carbon dioxide emitted from burning biomass will not increase total atmospheric carbon dioxide if this consumption is done on a sustainable basis (i.e., if in a given period of time, regrowth of biomass takes up as much carbon dioxide as is released from biomass combustion). Bio-mass energy is often suggested as a replacement for fossil fuel combustion, which has large greenhouse gas emissions.

      Biome A naturally occurring community of flora and fauna (or the region occupied by such a community) adapted to the particular conditions in which they occur (e.g., tundra).

      Biosphere The region of land, oceans, and atmosphere inhabited by living organisms.

      Black Carbon Operationally defined species based on measurement of light absorption and chemical reactivity and/or thermal stability; consists of soot, charcoal, and/or possible light-absorbing refractory organic matter.

      Borehole Any exploratory hole drilled into the Earth or ice to gather geophysical data. Climate researchers often take ice core samples, a type of borehole, to predict atmospheric composition in earlier years.

      Bubble A system that lets several countries meet a reduction target together while having different individual targets.

      C

      Capital Stocks The accumulation of machines and structures that are available to an economy at any point in time to prune goods or render services. These activities usually require a quantity of energy that is determined largely by the rate at which that machine or structure is used.

      Carbon Cycle The global scale exchange of carbon among its reservoirs, namely the atmosphere, oceans, vegetation, soils, and geologic deposits and minerals. This involves components in food chains, in the atmosphere as carbon dioxide, in the hydrosphere, and in the geosphere.

      Carbon Dioxide (CO2) The greenhouse gas whose concentration is being most affected directly by human activities. CO2 also serves as the reference to compare all other greenhouse gases. The major source of CO2 emissions is fossil fuel combustion. CO2 emissions are also a product of forest clearing, biomass burning, and non-energy production processes such as cement production. Atmospheric concentrations of CO2 have been increasing at a rate of about 0.5 percent per year and are now about 30 percent above preindustrial levels.

      Carbon Equivalent (CE) A metric measure used to compare the emissions of the different greenhouse gases based upon their global warming potential (GWP). Greenhouse gas emissions in the United States are most commonly expressed as “million metric tons of carbon equivalents” (MMTCE). Global warming potentials are used to convert greenhouse gases to carbon dioxide equivalents.

      Carbon Sequestration The uptake and storage of carbon. Trees and plants, for example, absorb carbon dioxide, release the oxygen and store the carbon. Fossil fuels were at one time biomass and continue to store the carbon until burned.

      Carbon Sinks Carbon reservoirs and conditions that take in and store more carbon (carbon sequestration) than they release. Carbon sinks can serve to partially offset greenhouse gas emissions. Forests and oceans are common carbon sinks.

      Chlorofluorocarbons and Related Compounds This family of anthropogenic compounds includes chlorofluorocarbons (CFCs), bromofluorocarbons (halons), methyl chloroform, carbon tetrachloride, methyl bromide, and hydrochlorofluorocarbons (HCFCs). These compounds have been shown to deplete stratospheric ozone, and therefore are typically referred to as ozone-depleting substances. The most ozone-depleting of these compounds are being phased out under the Montreal Protocol.

      Clean Development Mechanisms (CDM) Article 12 of the Kyoto Protocol provides for the CDM whereby developed countries are able to invest in emissions-reducing projects in developing countries to obtain credit to assist in meeting their assigned amounts. The details of the CDM have yet to be negotiated at the international level.

      Climate The average weather for a particular region and time period. Climate is not the same as weather, but rather, it is the average pattern of weather for a particular region. Climatic elements include precipitation, temperature, humidity, sunshine, wind velocity, phenomena such as fog, frost, and hail storms, and other measures of the weather.

      Climate Change The term climate change refers to all forms of climatic inconsistency. Climate change has been used synonymously with the term global warming.

      Climate Change Action Plan Unveiled in October 1993 by President Clinton, the CCAP is the U.S. plan for meeting its pledge to reduce greenhouse gas emissions under the terms of the Framework Convention on Climate Change (FCCC). The goal of the plan was to reduce U.S. emissions of greenhouse gases to 1990 levels by 2000.

      Climate Feedback An atmospheric, oceanic, terrestrial, or other process that is activated by the direct climate change induced by changes in radiative forcing. Climate feedbacks may increase (positive feedback) or diminish (negative feedback) the magnitude of the climate change.

      Climate Lag The delay that occurs in climate change as a result of some factor that changes only very slowly.

      Climate Model A quantitative way of representing the interactions of the atmosphere, oceans, land surface, and ice.

      Climate Modeling The simulation of the climate using computer-based models.

      Climate Sensitivity The equilibrium response of the climate to a change in radiative forcing; for example, a doubling of the carbon dioxide concentration.

      Climate System (or Earth System) The five physical components (atmosphere, hydrosphere, cryosphere, lithosphere, and biosphere) that are responsible for the climate and its variations.

      Cloud Condensation Nuclei Airborne particles that serve as an initial site for the condensation of liquid water and which can lead to the formation of cloud droplets.

      CO2 Fertilization The enhancement of plant growth as a result of elevated atmospheric CO2 concentrations.

      Coalbed Methane Coalbed methane is methane contained in coal seams, and is often referred to as virgin coalbed methane, or coal seam gas. For more information, visit the Coal-bed Methane Outreach program site.

      Coal Mine Methane Coal mine methane is the subset of CBM that is released from the coal seams during the process of coal mining. For more information, visit the Coalbed Methane Outreach program site.

      Cogeneration The process by which two different and useful forms of energy are produced at the same time. For example, while boiling water to generate electricity, the leftover steam can be sold for industrial processes or space heating.

      Compost Decayed organic matter that can be used as a fertilizer or soil additive.

      Conference of the Parties (COP) The supreme body of the United Nations Framework Convention on Climate Change (UNFCCC). It comprises more than 180 nations that have ratified the Convention. Its first session was held in Berlin, Germany, in 1995 and it is expected to continue meeting on a yearly basis. The COP's role is to promote and review the implementation of the Convention.

      Cryosphere One of the interrelated components of the Earth's system, the cryosphere is frozen water in the form of snow, permanently frozen ground (permafrost), floating ice, and glaciers. Fluctuations in the volume of the cryosphere cause changes in ocean sea level, which directly impact the biosphere.

      D

      Deforestation Those practices or processes that result in the change of forested lands to nonforest uses. This is often cited as one of the major causes of the enhanced greenhouse effect for two reasons: (1) the burning or decomposition of the wood releases carbon dioxide; and (2) trees that once removed carbon dioxide from the atmosphere in the process of photosynthesis are no longer present and contributing to carbon storage.

      Desertification The progressive destruction or degradation of existing vegetative cover to form desert. This can occur due to overgrazing, deforestation, drought, and the burning of extensive areas.

      Diurnal Temperature Range The difference between maximum and minimum temperature over a period of 24 hours.

      E

      Economic Potential The portion of the technical potential for GHG emissions reductions or energy-efficiency improvements that could be achieved cost-effectively in the absence of market barriers. The achievement of the economic potential requires additional policies and measures to break down market barriers.

      Eddy Mixing Mixing due to small scale turbulence processes (eddies). Such processes cannot be explicitly resolved by even the finest-resolution atmosphere-ocean general ciculation models currently in uses and so their effects must be related to the larger-scale conditions.

      El Niño A climatic phenomenon occurring irregularly, but generally every three to five years. El Ninos often first become evident during the Christmas season (El Niño means Christ-child) in the surface oceans of the eastern tropical Pacific Ocean. The phenomenon involves seasonal changes in the direction of the tropical winds over the Pacific and abnormally warm surface ocean temperatures. The changes in the tropics are most intense in the Pacific region; these changes can disrupt weather patterns throughout the tropics and can extend to higher latitudes.

      Emission Permit A nontransferable or tradeable allocation of entitlements by a government to an individual firm to emit a specific amount of a substance.

      Emission Quota The portion or share of total allowable emissions assigned to a country or group of countries within a framework of maximum total emissions and mandatory allocations of resources or assessments.

      Emissions The release of a substance (usually a gas when referring to climate change) into the atmosphere.

      Emission Standard A level of emission that under law may not be exceeded.

      Energy Intensity Ration of energy consumption and economic or physical output. At the national level, energy intensity is the ratio of total domestic primary energy consumption or final energy consumption to gross domestic product or physical output.

      Enhanced Greenhouse Effect The natural greenhouse effect has been enhanced by anthropogenic emissions of greenhouse gases. Increased concentrations of carbon dioxide, methane, and nitrous oxide, CFCs, HFCs, PFCs, SF6, NF3, and other photochemically important gases caused by human activities such as fossil fuel consumption and adding waste to landfills trap more infrared radiation, thereby exerting a warming influence.

      Equilibrium Response The steady state response of the climate system (or a climate model) to an imposed radiative forcing.

      Evap otr anspir ation The sum of evaporation and plant transpiration. Potential évapotranspiration is the amount of water that could be evaporated or transpired at a given temperature and humidity, if there was water available.

      F

      Fluorocarbons Carbon-fluorine compounds that often contain other elements such as hydrogen, chlorine, or bromine. Common fluorocarbons include chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydro-fluorocarbons (HFCs), and perfluorocarbons (PFCs).

      Forcing Mechanism A process that alters the energy balance of the climate system, i.e., changes the relative balance between incoming solar radiation and outgoing infrared radiation from Earth. Such mechanisms include changes in solar irradiance, volcanic eruptions, and enhancement of the natural greenhouse effect by emissions of greenhouse gases.

      G

      Geosphere The soils, sediments, and rock layers of the Earth's crust, both continental and beneath the ocean floors.

      Glacier A multiyear surplus accumulation of snowfall in excess of snowmelt on land and resulting in a mass of ice at least 0.1 km2 in area that shows some evidence of movement in response to gravity. A glacier may terminate on land or in water. Glaciers are found on every continent except Australia.

      Global Warming Global warming is an average increase in the temperature of the atmosphere near the Earth's surface and in the troposphere, which can contribute to changes in global climate patterns. Global warming can occur from many causes, both natural and human induced.

      Global Warming Potential (GWP) Defined as the cumulative radiative forcing effects of a gas over a specified time horizon resulting from the emission of a unit mass of gas relative to a reference gas. The GWP-weighted emissions of direct greenhouse gases in the U.S. inventory are presented in terms of equivalent emissions of carbon dioxide, using units of teragrams of carbon dioxide equivalents.

      Greenhouse Effect Trapping and buildup of heat in the atmosphere (troposphere) near the Earth's surface. Some of the heat flowing back toward space from the Earth's surface is absorbed by water vapor, carbon dioxide, ozone, and several other gases in the atmosphere and then rera-diated back toward the Earth's surface. If the atmospheric concentrations of these greenhouse gases rise, the average temperature of the lower atmosphere will gradually increase.

      Greenhouse Gas (GHG) Any gas that absorbs infrared radiation in the atmosphere. Greenhouse gases include, but are not limited to, water vapor, carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), ozone (O3), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6).

      H

      Halocarbons Compounds containing either chlorine, bromine, or fluorine and carbon. Such compounds can act as powerful greenhouse gases in the atmosphere. The chlorine and bromine containing halocarbons are also involved in the depletion of the ozone layer.

      Hydrocarbons Substances containing only hydrogen and carbon. Fossil fuels are made up of hydrocarbons.

      Hydrochlorofluorocarbons (HCFCs) Compounds containing hydrogen, fluorine, chlorine, and carbon atoms. Although ozone-depleting substances, they are less potent at destroying stratospheric ozone than chlorofluorocarbons (CFCs). They have been introduced as temporary replacements for CFCs and are also greenhouse gases.

      Hydrologie Cycle The process of evaporation, vertical and horizontal transport of vapor, condensation, precipitation, and the flow of water from continents to oceans. It is a major factor in determining climate through its influence on surface vegetation, the clouds, snow and ice, and soil moisture. The hydrologie cycle is responsible for 25 to 30 percent of the midlatitudes' heat transport from the equatorial to polar regions.

      Hydrosphere The component of the climate system comprising liquid surface and subterranean water, such as oceans, seas, rivers, freshwater lakes, underground water.

      I

      Ice Core A cylindrical section of ice removed from a glacier or an ice sheet in order to study climate patterns of the past. By performing chemical analyses on the air trapped in the ice, scientists can estimate the percentage of carbon dioxide and other trace gases in the atmosphere at a given time.

      Infrared Radiation Radiation emitted by the Earth's surface, the atmosphere and the clouds. It is also known as terrestrial or longwave radiation. Infrared radiation has a distinctive range of wavelengths longer than the wavelength of the red color in the visible part of the spectrum.

      Intergovernmental Panel on Climate Change (IPCC) The IPCC was established jointly by the United Nations Environment Program and the World Meteorological Organization in 1988. The purpose of the IPCC is to assess information in the scientific and technical literature related to all significant components of the issue of climate change. With its capacity for reporting on climate change, its consequences, and the viability of adaptation and mitigation measures, the IPCC is also looked to as the official advisory body to the world's governments on the state of the science of the climate change issue.

      L

      Landfill Land waste disposal site in which waste is generally spread in thin layers, compacted, and covered with a fresh layer of soil each day.

      Longwave Radiation The radiation emitted in the spectral wavelength greater than 4 micrometers corresponding to the radiation emitted from the Earth and atmosphere.

      M

      Methane (CH4) A hydrocarbon that is a greenhouse gas with a global warming potential most recently estimated at 23 times that of carbon dioxide (CO2). Methane is produced through anaerobic (without oxygen) decomposition of waste in landfills, animal digestion, decomposition of animal wastes, production and distribution of natural gas and petroleum, coal production, and incomplete fossil fuel combustion.

      Metric Ton Common international measurement for the quantity of greenhouse gas emissions. A metric ton is equal to 2,205 lbs. or 1.1 short tons.

      Mount Pinatubo An active volcano located in the Philippine Islands that erupted in 1991. The eruption of Mount Pinatubo ejected enough particulate and sulfate aerosol matter into the upper atmosphere to block some of the incoming solar radiation from reaching Earth's atmosphere.

      N

      Natural Gas Underground deposits of gases consisting of 50 to 90 percent methane (CH4) and small amounts of heavier gaseous hydrocarbon compounds such as propane (C3H8) and butane (C4H10).

      Nitrogen Oxides (NOx) Gases consisting of one molecule of nitrogen and varying numbers of oxygen molecules. Nitrogen oxides are produced in the emissions of vehicle exhausts and from power stations. In the atmosphere, nitrogen oxides can contribute to formation of smog, can impair visibility, and have health consequences.

      Nitrous Oxide (N2O) A powerful greenhouse gas with a global warming potential of 296 times that of carbon dioxide (CO2). Major sources of nitrous oxide include soil cultivation practices, especially the use of commercial and organic fertilizers, fossil fuel combustion, nitric acid production, and biomass burning.

      O

      Oxidize To chemically transform a substance by combining it with oxygen.

      Ozone (O3) Ozone, the triatomic form of oxygen (O3), is a gaseous atmospheric constituent. In the troposphere, it is created both naturally and by photochemical reactions involving gases resulting from human activities (photochemical smog). In high concentrations, tropospheric ozone can be harmful to a wide range of living organisms. Tropospheric ozone acts as a greenhouse gas. In the stratosphere, ozone is created by the interaction between solar ultraviolet radiation and molecular oxygen (O2). Stratospheric ozone plays a decisive role in the stratospheric radiative balance. Depletion of stratospheric ozone, due to chemical reactions that may be enhanced by climate change, results in an increased ground-level flux of ultraviolet (UV-) B radiation.

      Ozone-Depleting Substance (ODS) A family of man-made compounds that includes chlorofluorocarbons (CFCs), bromofluorocarbons (halons), methyl chloroform, carbon tetrachloride, methyl bromide, and hydrochlorofluorocarbons (HCFCs). These compounds have been shown to deplete stratospheric ozone, and therefore are typically referred to as ODSs.

      Ozone Layer The layer of ozone that begins approximately 9 mi. (15 km.) above Earth and thins to an almost negligible amount at about 31 mi. (50 km.), shields the Earth from harmful ultraviolet radiation from the Sun.

      Ozone Precursors Chemical compounds, such as carbon monoxide, methane, nonmethane hydrocarbons, and nitrogen oxides, which in the presence of solar radiation react with other chemical compounds to form ozone, mainly in the troposphere.

      P

      Particulate Matter (PM) Very small pieces of solid or liquid matter such as particles of soot, dust, fumes, mists, or aerosols.

      Parts per Billion (ppb) Number of parts of a chemical found in one billion parts of a particular gas, liquid, or solid mixture.

      Parts per Million (ppm) Number of parts of a chemical found in one million parts of a particular gas, liquid, or solid.

      Perfluorocarbons (PFCs) A group of human-made chemicals composed of carbon and fluorine only. These chemicals were introduced as alternatives, along with hydrofluorocarbons, to the ozone-depleting substances.

      Photosynthesis The process by which plants take CO2 from the air (or bicarbonate in water) to build carbohydrates, releasing O2 in the process. There are several pathways of photosynthesis with different responses to atmospheric CO2 concentrations.

      Precession The comparatively slow torquing of the orbital planes of all satellites with respect to the Earths axis, due to the bulge of the Earth at the equator which distorts the Earth's gravitational field.

      R

      Radiation Energy transfer in the form of electromagnetic waves or particles that release energy when absorbed by an object.

      Radiative Forcing Radiative forcing is the change in the net vertical irra-diance (expressed in Watts per square meter: Wm-2) at the tropopause due to an internal change or a change in the external forcing of the climate system, such as, for example, a change in the concentration of carbon dioxide or the output of the Sun.

      Recycling Collecting and reprocessing a resource so it can be used again. An example is collecting aluminum cans, melting them down, and using the aluminum to make new cans or other aluminum products.

      Reforestation Planting of forests on lands that have previously contained forests but that have been converted to some other use.

      Residence Time The average time spent in a reservoir by an individual atom or molecule. With respect to greenhouse gases, residence time usually refers to how long a particular molecule remains in the atmosphere.

      Respiration The biological process whereby living organisms convert organic matter to CO2, releasing energy and consuming O2.

      S

      Short Ton Common measurement for a ton in the United States. A short ton is equal to 2,000 lbs. or 0.907 metric tons.

      Sink Any process, activity, or mechanism which removes a greenhouse gas, an aerosol, or a precursor of a greenhouse gas or aerosol from the atmosphere.

      Soil Carbon A major component of the terrestrial biosphere pool in the carbon cycle. The amount of carbon in the soil is a function of the historical vegetative cover and productivity, which in turn is dependent in part upon climatic variables.

      Solar Radiation Radiation emitted by the Sun. It is also referred to as shortwave radiation. Solar radiation has a distinctive range of wavelengths (spectrum) determined by the temperature of the Sun.

      Stratosphere Region of the atmosphere between the troposphere and mesosphere, having a lower boundary of approximately 5 mi. (8 km.) at the poles to 9 mi. (15 km.) at the equator and an upper boundary of approximately 31 mi. (50 km.). Depending upon latitude and season, the temperature in the lower stratosphere can increase, be isothermal, or even decrease with altitude, but the temperature in the upper stratosphere generally increases with height due to absorption of solar radiation by ozone.

      Streamflow The volume of water that moves over a designated point over a fixed period of time. It is often expressed as cubic feet per second (ft3/sec).

      Sulfate Aerosols Particulate matter that consists of compounds of sulfur formed by the interaction of sulfur dioxide and sulfur trioxide with other compounds in the atmosphere. Sulfate aerosols are injected into the atmosphere from the combustion of fossil fuels and the eruption of volcanoes.

      Sulfur Hexafluoride (SF6) A colorless gas soluble in alcohol and ether, slightly soluble in water. A very powerful greenhouse gas used primarily in electrical transmission and distribution systems and as a dielectric in electronics.

      T

      Thermohaline Circulation Large-scale density-driven circulation in the ocean, caused by differences in temperature and salinity. In the North Atlantic the thermohaline circulation consists of warm surface water flowing northward and cold deep water flowing southward, resulting in a net poleward transport of heat.

      Trace Gas Any one of the less common gases found in the Earths atmosphere. Nitrogen, oxygen, and argon make up more than 99 percent of the Earths atmosphere. Other gases, such as carbon dioxide, water vapor, methane, oxides of nitrogen, ozone, and ammonia, are considered trace gases.

      Troposphere The lowest part of the atmosphere from the surface to about 6 mi./10 km. in altitude in mid-latitudes (ranging from 5.5 mi. [9 km.] in high latitudes to 10 mi. [16 km.] in the tropics on average) where clouds and “weather” phenomena occur.

      U

      Ultraviolet Radiation (UV) The energy range just beyond the violet end of the visible spectrum. Although ultraviolet radiation constitutes only about 5 percent of the total energy emitted from the sun, it is the major energy source for the stratosphere and mesosphere, playing a dominant role in both energy balance and chemical composition.

      United Nations Framework Convention on Climate Change (UNFCCC) The Convention on Climate Change sets an overall framework for intergovernmental efforts to tackle the challenge posed by climate change. It recognizes that the climate system is a shared resource whose stability can be affected by industrial and other emissions of carbon dioxide and other greenhouse gases.

      W

      Wastewater Water that has been used and contains dissolved or suspended waste materials.

      Water Vapor The most abundant greenhouse gas, it is the water present in the atmosphere in gaseous form. Water vapor is a part of the natural greenhouse effect.

      Weather Atmospheric condition at any given time or place. It is measured in terms of such things as wind, temperature, humidity, atmospheric pressure, cloudiness, and precipitation.

      Fernando Herrera University of California, San Diego

      Appendix

      Appendix
      Graphic Plots and Text Prepared by Robert A. Rohde University of California, Berkeley
      Global Temperatures

      This image shows the instrumental record of global average temperatures as compiled by the Climatic Research Unit of the University of East Anglia and the Hadley Centre of the UK Meteorological Office. Data set Had-CRUT3 was used, which follows the methodology outlined by Brohan et al. (2006). Following the common practice of the IPCC, the zero on this figure is the mean temperature from 1961 tol990.

      The uncertainty in the analysis techniques leading to these measurements is discussed in Foland et al. (2001) and Brohan et al. (2006). They estimate that global averages since 1950 are within −0.05 degrees C of their reported value with 95 percent confidence. In the recent period, these uncertainties are driven primarily by considering the potential impact of regions where no temperature record is available. For averages prior to −1890, the uncertainty reaches −0.15 degrees C driven primarily by limited sampling and the effects of changes in sea surface measurement techniques. Uncertainties between 1880 and 1890 are intermediate between these values.

      Incorporating these uncertainties, Foland et al. (2001) estimated the global temperature change from 1901 to 2000 as 0.57 ± 0.17 degrees C, which contributed to the 0.6 ± 0.2 degrees C estimate reported by the Intergovernmental Panel on Climate Change (IPCC 2001a, [1]). Both estimates are 95 percent confidence intervals.

      Recent Sea Level Rise

      This figure shows the change in annually averaged sea level at 23 geologically stable tide gauge sites with long-term records as selected by Douglas (1997). The thick dark line is a three-year moving average of the instrumental records. This data indicates a sea level rise of −18.5 cm. from 1900–2000. Because of the limited geographic coverage of these records, it is not obvious whether the apparent decadal fluctuations represent true variations in global sea level or merely variations across regions that are not resolved.

      For comparison, the recent annually averaged satellite altimetry data from TOPEX/Poseidon are shown in the thick gray line. These data indicate a somewhat higher rate of increase than tide gauge data, however the source of this discrepancy is not obvious. It may represent systematic error in the satellite record and/or incomplete geographic sampling in the tide gauge record. The month-to-month scatter on the satellite measurements is roughly the thickness of the plotted gray curve.

      Much of recent sea level rise has been attributed to global warming.

      Achieved Hurricane Intensity under Idealized Conditions

      This figure, which reproduces one of the key conclusions of Knutson and Tuleya (2004), shows a prediction for how hurricanes and other tropical cyclones may intensify as a result of global warming. Specifically, Knutson and Tuleya performed an experiment using climate models to estimate the strength achieved by cyclones allowed to intensify over either a modern summer ocean or over an ocean warmed by carbon dioxide concentrations 220 percent higher than present day. A number of different climate models were considered as well as conditions over all the major cyclone-forming ocean basins. Depending on site and model, the ocean warming involved ranged from 0.8 to 2.4 degrees C. Results, which were found to be robust across different models, showed that storms intensified by about one-half category (on the Saffir-Simpson Hurricane Scale) as a result of the warmer oceans. This is accomplished with a ∼6 percent increase in wind speed or equivalently a −20 percent increase in energy (for a storm of fixed size). Most significantly these result suggest that global warming may lead to a gradual increase in the probability of highly destructive category 5 hurricanes. This work does not provide any information about future frequency of tropical storms. Also, since it considers only the development of storms under nearly ideal conditions for promoting their formation, this work is primarily a prediction for how the maximum achievable storm intensity will change. Hence, this does not directly bear on the growth or development of storms under otherwise weak or marginal conditions for storm development (such as high upper-level wind shear). However, it is plausible that warmer oceans will somewhat extend the regions and seasons under which hurricanes may develop.

      Annual Carbon Emissions by Region

      This figure shows the annual fossil fuel carbon dioxide emissions, in million metric tons of carbon, for a variety of non-overlapping regions covering the Earth. Data source: Carbon Dioxide Information Analysis Center. Regions are sorted from largest emitter (as of 2000) to the smallest:

      • United States and Canada
      • Western Europe (plus Germany)
      • Communist East Asia (China, North Korea, Mongolia, etc.)
      • Eastern Europe, Russia, and Former Soviet States
      • India and Southeast Asia (plus South Korea)
      • Australia, Japan and other Pacific Island States
      • Central and South America (includes Mexico and the Caribbean)
      • Middle East
      • Africa

      Ice Age Temperature Changes

      This figure shows the Antarctic temperature changes during the last several glacial/interglacial cycles of the present ice age and a comparison to changes in global ice volume. The present day is on the right.

      The first two curves show local changes in temperature at two sites in Antarctica as derived from deuterium isotopie measurements (δD) on ice cores (EPICA Community Members 2004, Petit et al. 1999). The final plot shows a reconstruction of global ice volume based on δ180 measurements on benthic foraminifera from a composite of globally distributed sediment cores and is scaled to match the scale of fluctuations in Antarctic temperature (Lisiecki and Raymo 2005). Note that changes in global ice volume and changes in Antarctic temperature are highly correlated, so one is a good estimate of the other, but differences in the sediment record do not necessarily reflect differences in paleotemperature. Horizontal lines indicate modern temperatures and ice volume. Differences in the alignment of various features reflect dating uncertainty and do not indicate different timing at different sites.

      The Antarctic temperature records indicate that the present interglacial is relatively cool compared to previous interglacials, at least at these sites. It is believed that the interglacials themselves are triggered by changes in Earths orbit known as Milankovitch cycles and that the variations in individual interglacials can be partially explained by differences within this process. For example, Overpeck et al. (2006) argues that the previous interglacial was warmer because of increased solar radiation at high latitudes. The Liesecki and Raymo (2005) sediment reconstruction does not indicate significant differences between modern ice volume and previous interglacials, though some other studies do report slightly lower ice volumes/higher sea levels during the 120 ka and 400 ka interglacials (Karner et al. 2001, Hearty and Kaufman 2000). It should be noted that temperature changes at the typical equatorial site are believed to have been significantly less than the changes observed at high latitude.

      Sixty-Five Million Years of Climate Change

      This figure shows climate change over the last 65 million years. The data is based on a compilation of oxygen isotope measurements (δ180) on benthic foraminifera by Zachos et al. (2001), which reflect a combination of local temperature changes in their environment and changes in the isotopie composition of seawater associated with the growth and retreat of continental ice sheets.

      Because it is related to both factors, it is not possible to uniquely tie these measurements to temperature without additional constraints. For the most recent data, an approximate relationship to temperature can be made by observing that the oxygen isotope measurements of Lisiecki and Raymo (2005) are tightly correlated to temperature changes at Vostok, Antarctica as established by Petit et al. (1999). Present day is indicated as 0. For the oldest part of the record, when temperatures were much warmer than today, it is possible to estimate temperature changes in the polar oceans (where these measurements were made) based on the observation that no significant ice sheets existed and hence all fluctuation in (δ180) must result from local temperature changes (as reported by Zachos et al).

      The intermediate portion of the record is dominated by large fluctuations in the mass of the Antarctic ice sheet, which first nucleates approximately 34 million years ago, then partially dissipates around 25 million years ago, before re-expanding toward its present state 13 million years ago. These fluctuations make it impossible to constrain temperature changes without additional controls. Significant growth of ice sheets did not begin in Greenland and North America until approximately 3 million years ago, following the formation of the Isthmus of Panama by continental drift. This ushered in an era of rapidly cycling glacials and interglacials (upper right). Also appearing on this graph are the Eocene Climatic Optimum, an extended period of very warm temperatures, and the Paleocene-Eocene Thermal Maximum (labeled PETM). Due to the coarse sampling and averaging involved in this record, it is likely that the full magnitude of the PETM is underestimated by a factor of 2 to 4 times its apparent height.

      Five Million Years of Climate Change from Sediment Cores

      This figure shows the climate record of Lisiecki and Raymo (2005) constructed by combining measurements from 57 globally distributed deep-sea sediment cores. The measured quantity is oxygen isotope fractionation in benthic foraminifera, which serves as a proxy for the total global mass of glacial ice sheets.

      Lisiecki and Raymo constructed this record by first applying a computer-aided process of adjusting individual “wiggles” in each sediment core to have the same alignment (i.e. wiggle matching). Then the resulting stacked record is orbitally tuned by adjusting the positions of peaks and valleys to fall at times consistent with an orbitally driven ice model (see Milankovitch Cycles). Both sets of these adjustments are constrained to be within known uncertainties on sedimentation rates and consistent with independently dated tie points (if any). Constructions of this kind are common, however, they presume that ice sheets are orbitally driven, and hence data such as this can not be used in establishing the existence of such a relationship.

      The observed isotope variations are very similar in shape to the temperature variations recorded at Vostok, Antarctica, during the 420 kyr for which that record exists. Hence the right-hand scale of the figure was established by fitting the reported temperature variations at Vostok (Petit et al. 1999) to the observed isotope variations. As a result, this temperature scale should be regarded as approximate and its magnitude is only representative of Vostok changes. In particular, temperature changes at polar sites, such as Vostok, frequently exceed the changes observed in the tropics or in the global average. A horizontal line at 0 degrees C indicates modern temperatures (circa 1950).

      Labels are added to indicate regions where 100 kyr and 41 kyr cyclicity is observed. These periodicities match periodic changes in Earths orbital eccentricity and obliquity, respectively, and have been previously established by other studies (not relying on orbital tuning).

      Reconstructed Temperature, 2,000 Years

      This image is a comparison of 10 different published reconstructions of mean temperature changes during the last 2,000 years. More recent reconstructions are plotted toward the front and in redder colors, older reconstructions appear towards the back and in bluer colors. An instrumental history of temperature is also shown in black. The medieval warm period and Little Ice Age are labeled at roughly the times when they are historically believed to occur, though it is still disputed whether these were truly global or only regional events. The single, unsmoothed annual value for 2004 is also shown for comparison.

      It is unknown which, if any, of these reconstructions is an accurate representation of climate history; however, these curves are a fair representation of the range of results appearing in the published scientific literature. Hence, it is likely that such reconstructions, accurate or not, will play a significant role in the ongoing discussions of global climate change and global warming.

      For each reconstruction, the raw data has been decadally smoothed with a σ = 5 yr Gaussian weighted moving average. Also, each reconstruction was adjusted so that its mean matched the mean of the instrumental record during the period of overlap.

      Holocene Temperature Variations

      The main figure shows eight records of local temperature variability on multi-centennial scales throughout the course of the Holocene, and an average of these (thick dark line). The records are plotted with respect to the mid-20th-century average temperatures, and the global average temperature in 2004 is indicated. The inset plot compares the most recent two millennia of the average to other high resolution reconstructions of this period. At the far left of the main plot climate emerges from the last glacial period of the current ice age into the relative stability of the current interglacial. There is general scientific agreement that during the Holocene itself temperatures have been quite stable compared to the fluctuations during the preceding glacial period. The average curve above supports this belief. However, there is a slightly warmer period in the middle which might be identified with the proposed Holocene climatic optimum. The magnitude and nature of this warm event is disputed, and it may have been largely limited to summer months and/or high northern latitudes.

      Because of the limitations of data sampling, each curve in the main plot was smoothed, and consequently, this figure can not resolve temperature fluctuations faster than approximately 300 years. Further, while 2004 appears warmer than any other time in the long-term average, an observation that might be a sign of global warming, it should also be noted that the 2004 measurement is from a single year. It is impossible to knowwhether similarly large short-term temperature fluctuations may have occurred at other times but are unresolved by the resolution available in this figure. The next 150 years will determine whether the long-term average centered on the present appears anomalous with respect to this plot. Since there is no scientific consensus on how to reconstruct global temperature variations during the Holocene, the average shown here should be understood as only a rough, quasi-global approximation to the temperature history of the Holocene. In particular, higher resolution data and better spatial coverage could significantly alter the apparent long-term behavior.

      Phanerozoic Climate Change

      This figure shows the long-term evolution of oxygen isotope ratios during the Phanerozoic eon as measured in fossils, reported by Veizer et al. (1999), and updated online in 2004 [1]. Such ratios reflect both the local temperature at the site of deposition and global changes associated with the extent of continental glaciation. As such, relative changes in oxygen isotope ratios can be interpreted as rough changes in climate. Quantitative conversion between this data and direct temperature changes is a complicated process subject to many systematic uncertainties, however, it is estimated that each 1 part per thousand change in δ180 represents roughly a 1.5–2 degrees C change in tropical sea surface temperatures (Veizer et al. 2000). Also shown on this figure are blue bars showing periods when geological criteria (Frakes et al. 1992) indicate cold temperatures and glaciation as reported by Veizer et al. (2000). AU data presented here have been adjusted to the 2004 ICS geologic times-cale. The “short-term average” was constructed by applying a σ = 3 Myr Gaussian weighted moving average to the original 16,692 reported measurements. The gray bar is the associated 95 percent statistical uncertainty in the moving average. The “low frequency mode” is determined by applying a band-pass filter to the short-term averages in order to select fluctuations on timescales of 60 Myr or greater.

      On geologic time scales, the largest shift in oxygen isotope ratios is due to the slow radiogenic evolution of the mantle. It is not possible to draw any conclusion about very long-term (>200 Myr) changes in temperatures from this data alone. However, it is usually believed that temperatures during the present cold period and during the Cretaceous thermal maximum are not greatly different from cold and hot periods during most of the rest the Phanerozoic. Some recent work has disputed this (Royer et al. 2004) suggesting instead that the highs and lows in the early part of the Phanerozoic were both significantly warmer than their recent counterparts. Common symbols for geologic periods are plotted at the top and bottom of the figure for reference.

      Global Fossil Carbon Emissions

      Global annual fossil fuel carbon dioxide emissions, in million metric tons of carbon, as reported by the Carbon Dioxide Information Analysis Center.

      Original data: [full text] Marland, G., T.A. Boden, and R. J. Andres (2003). “Global, Regional, and National CO2 Emissions” in Trends: A Compendium of Data on Global Change. Oak Ridge, Tenn., U.S.A.: Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy.

      The data is originally presented in terms of solid (e.g., coal), liquid (e.g., petroleum), gas (i.e., natural gas) fuels, and separate terms for cement production and gas flaring (i.e., natural gas lost during oil and gas mining). In the plotted figure, the gas flaring (the smallest of all categories) was added to the total for natural gas. Note that the carbon dioxide releases from cement production result from the thermal decomposition of limestone into lime, and so technically are not a fossil fuel source.

      Global Warming Predictions

      This figure shows the predicted distribution of temperature change due to global warming from the Hadley Centre HadCM3 climate model. These changes are based on the IS92a (“business as usual”) projections of carbon dioxide and other greenhouse gas emissions during the next century, and essentially assume normal levels of economic growth and no significant steps are taken to combat global greenhouse gas emissions.

      The plotted gray tints show predicted surface temperature changes expressed as the average prediction for 2070–2100 relative to the model's baseline temperatures in 1960–90. The average change is 3.0 degrees C, placing this model on the lower half of the Intergovernmental Panel on Climate Change's 1.4–5.8 degrees C predicted climate change from 1990 to 2100. As can be expected from their lower specific heat, continents are expected to warm more rapidly than oceans with an average of 4.2 degrees C and 2.5 degrees C in this model, respectively. The lowest predicted warming is 0.55 degrees C south of South America and the highest is 9.2 degrees C in the Arctic Ocean (points exceeding 8 degrees C are plotted as black).

      This model is fairly homogeneous except for strong warming around the Arctic Ocean related to melting sea ice and strong warming in South America related to predicted changes in the El Nino cycle and Brazillian rainforest. This pattern is not a universal feature of models, as other models can produce large variations in other regions (e.g., Africa and India) and less extreme changes in places like South America.

      Global Warming Projections

      This figure shows climate model predictions for global warming under the SRES A2 emissions scenario relative to global average temperatures in 2000. The A2 scenario is characterized by a politically and socially diverse world that exhibits sustained economic growth but does not address the inequities between rich and poor nations, and takes no special actions to combat global warming or environmental change issues. This world in 2100 is characterized by large population (15 billion), high total energy use, and moderate levels of fossil fuel dependency (mostly coal). At the time of the IPCC Third Assessment Report, the A2 scenario was the most well-studied of the SRES scenarios.

      The IPCC predicts global temperature change of 1.4–5.8 degrees C due to global warming from 1990 to 2100 (IPCC 2001a). As evidenced above (a range of 2.5 degrees C in 2100), much of this uncertainty results from disagreement among climate models, though additional uncertainty comes from different emissions scenarios.

      Economic Efficiency of Fossil Fuel Usage

      This figure shows an estimate of how efficiently the world s 20 largest economies convert fossil fuel usage into wealth as expressed by the ratio of their gross domestic product (calculated by the method of purchasing power parity in U.S. dollars) over the number of kilograms of fossil fuel carbon released into the atmosphere each year. The relatively narrow range of variation between most countries in this figure suggests that the pursuit of wealth in the present world is strongly tied to the availability of fossil fuel energy sources.

      As countries maybe reluctant to combat fossil fuel emissions in ways that cause economic decline, this figure serves to suggest the degree to which different large economies can decrease emissions through short-term improvements in efficiency and alternative fuel programs.

      The two countries that produce the highest GDP per kilogram carbon, Brazil and France, are heavily reliant on alternative energy sources, hydroelectric and nuclear power, respectively.

      Fossil Fuel Usage per Person

      This figure shows the disparity in fossil fuel consumption per capita for the countries with the twenty largest populations. The large range of variation is indicative of the separation between the rich, industrialized nations and the poor/developing nations. The global average is also shown.

      As most countries desire wealth and aim to develop that wealth through the development of industry, this figure suggests the degree to which poor nations may strive to increase their emissions in the course of trying to match the industrial capacity of the developed world. Managing such increases and dealing with the apparent social inequality of the present system will be one of the challenges involved in confronting global warming.

      Global Trends in Greenhouse Gases

      Global trends in major greenhouse gas concentrations. The rise of greenhouse gases, and their resulting impact on the greenhouse effect, are believed to be responsible for most of the increase in global average temperatures during the last 50 years. This change, known as global warming, has provoked calls to limit the emissions of these greenhouse gases (e.g., Kyoto Protocol). Notably, the chlorofluorocarbons CFC-11 and CFC-12 shown above have undergone substantial improvement since the Montreal Protocol severely limited their release due to the damage they were causing to the ozone layer.

      At present, approximately 99 percent of the 100-year global warming potential for all new emissions can be ascribed to just the three gases: carbon dioxide, methane, and nitrous oxide.

      Milankovitch Cycles

      The Earth's orbit around the sun is slightly elliptical. Over time the gravitational pull of the moon and other planets causes the Earth's orbit to change following a predictable pattern of natural rhythms, known as Milankovitch cycles. Over a 100,000 year cycle the Earth migrates from an orbit with near-zero eccentricity (a perfect circle) to one with approximately 6 percent eccentricity (a slight ellipse). In addition, the tilt of the Earth axis, known as its obliquity, varies from 21.5 to 24.5 degrees with a 41,000 year rhythm. And lastly, the orientation of the Earth's axis rotates with a ∼ 20,000-year cycle relative to the orientation of the Earth's orbit. This cycle, known as “precession” affects the intensity of the seasons.

      The figure shows the pattern of changes in each of the three modes of orbital variability: eccentricity, obliquity, and precession. These changes in the Earth's orbit lead to a complex series of changes in the amount of sunlight that a given location on Earth can expect to receive during a given season. An example is shown for summer sunlight near the Arctic circle. Sunlight at this location is believed to influence the growth and decay of ice sheets during ice ages. The last line shows measured changes in climate during the last million years with warm interglacials highlighted in gray bands. As can be seen, such interglacials appear to preferentially occur near maxima in eccentricity and slightly following times of maximum summer sunlight.

      Photo Credits

      Photo credits

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