GLOBAL WARMING

GLOBAL WARMING. Gases created through human industrial and agricultural practices (primarily carbon dioxide from burning fossil fuels and wood, as well as methane, nitrous oxide, and chlorofluorocarbons) increase the heat-reflecting potential of the atmosphere, thereby raising the planet's average temperature.

Early Scientific Work

Since the late nineteenth century, atmospheric scientists in the United States and overseas have known that significant changes in the chemical composition of atmospheric gases might cause climate change on a global scale. In 1824, the French scientist Jean-Baptiste Fourier described how the earth's atmosphere functioned like the glass of a greenhouse, trapping heat and maintaining the stable climate that sustained life. By the 1890s, some scientists, including the Swedish chemist Svante Arrhenius and the American geologist Thomas Chamberlain, had discerned that carbon dioxide had played a central role historically in regulating global temperatures.

In 1896, Arrhenius provided the first quantitative analysis of how changes in atmospheric carbon dioxide could alter surface temperatures and ultimately lead to climatic change on a scale comparable with the ice ages. In 1899, Chamberlain similarly linked glacial periods to changes in atmospheric carbon dioxide and posited that water vapor might provide crucial positive feedback to changes in carbon dioxide. In the first decade of the twentieth century, Arrhenius further noted that industrial combustion of coal and other fossil fuels could introduce enough carbon dioxide into the atmosphere to change the temperature of the planet over the course of a few centuries. However, he predicted that warming would be delayed because the oceans would absorb most of the carbon dioxide. Arrhenius further posited various societal benefits from this planetary warming.

Developing Scientific Consensus

Over the course of the twentieth century, scientists con-firmed these early predictions as they probed further into the functioning of the earth's atmospheric system. Early in the century, dozens of scientists around the world contributed to an internationally burgeoning understanding of atmospheric science. By the century's close, thousands of scientists collaborated to refine global models of climate change and regional analyses of how rising temperatures might alter weather patterns, ecosystem dynamics, agriculture, oceans and ice cover, and human health and disease.

While no one scientific breakthrough revolutionized climate change science or popular understanding of the phenomenon, several key events stand out to chart developing scientific understanding of global warming. In 1938, Guy S. Callendar provided an early calculation of warming due to human-introduced carbon dioxide and contended that this warming was evident already in the temperature record. Obscured by the onset of World War II and by a short-term cooling trend that began in the 1940s, Callendar's analysis received short shrift. Interest in global warming increased in the 1950s with new techniques for studying climate, including analysis of ancient pollens, ocean shells, and new computer models. Using computer models, in 1956, Gilbert N. Plass attracted greater attention to the carbon dioxide theory of climate change. The following year, Roger Revelle and Hans Suess showed that oceanic absorption of atmospheric carbon dioxide would not be sufficient to delay global warming. They stressed the magnitude of the phenomenon:

Human beings are now carrying out a large scale geophysical experiment of a kind that could not have happened in the past nor be reproduced in the future. Within a few centuries we are returning to the atmosphere and oceans the concentrated organic carbon stored in sedimentary rocks over hundreds of millions of years. (Cristianson, Greenhouse, pp. 155–156)

At the same time, Charles Keeling began to measure the precise year-by-year rise in atmospheric carbon dioxide from the Mauna Loa Observatory in Hawaii. In 1965, the President's Scientific Advisory Committee issued the first U.S. government report that summarized recent climate research and outlined potential future changes resulting from increased atmospheric carbon dioxide, including the melting of the Antarctic ice cap, the rise of sea level, and the warming of oceans.

By the late 1970s, atmospheric scientists had grown increasingly confident that the buildup of carbon dioxide, methane, chlorofluorocarbons, and related gases in the atmosphere would have a significant, lasting impact on global climate. Several jointly written government reports issued during President Jimmy Carter's administration presented early consensus estimates of global climate change. These estimates would prove consistent with more sophisticated models refined in the two decades following. A 1979 National Research Council report by Jule G. Charney, Carbon Dioxide and Climate: A Scientific Assessment, declared that "we now have incontrovertible evidence that the atmosphere is indeed changing and that we ourselves contribute to that change. Atmospheric concentrations of carbon dioxide are steadily increasing, and these changes are linked with man's use of fossil fuels and exploitation of the land" (p. vii). The Charney report estimated a doubling of atmospheric carbon dioxide concentrations would probably result in a roughly 3-degree Celsius rise in temperature, plus or minus 1.5 degrees.

Global Warming Politics

As climate science grew more conclusive, global warming became an increasingly challenging political problem. In January 1981, in the closing days of the Carter administration, the Council on Environmental Quality (CEQ) published Global Energy Futures and the Carbon Dioxide Problem. The CEQ report described climate change as the "ultimate environmental dilemma," which required collective judgments to be made, either by decision or default, "largely on the basis of scientific models that have severe limitations and that few can understand." The report reviewed available climate models and predicted that carbon dioxide–related global warming "should be observable now or sometime within the next two decades"

(p. v). With atmospheric carbon dioxide increasing rapidly, the CEQ report noted that the world was already "performing a great planetary experiment" (p. 52).

By the early 1980s, the scientific models of global warming had established the basic contours of this atmospheric phenomenon. Federal environmental agencies and scientific advisory boards had urged action to curb carbon dioxide emissions dramatically, yet little state, federal, or international policymaking ensued. Decades-old federal and state subsidies for fossil fuel production and consumption remained firmly in place. The federal government lessened its active public support for energy efficiency initiatives and alternative energy development. Falling oil and natural gas prices throughout the decade further undermined political support for a national energy policy that would address the problem of global warming.

A complicated intersection of climate science and policy further hindered effective lawmaking. Scientists urged political action, but spoke in a measured language that emphasized probability and uncertainty. Many scientists resisted entering the political arena, and expressed skepticism about their colleagues who did. This skepticism came to a head in reaction to the government scientist James Hansen's efforts to focus national attention on global warming during the drought-filled summer of 1988. As more than 400,000 acres of Yellowstone National Park burned in a raging fire, Hansen testified to Congress that he was 99 percent certain that the earth was getting warmer because of the greenhouse effect. While the testimony brought significant new political attention in the United States to the global warming problem, many of Hansen's scientific colleagues were dismayed by his definitive assertions. Meanwhile, a small number of skeptical scientists who emphasized the un-certainty of global warming and the need to delay policy initiatives fueled opposition to political action.

In 1988, delegates from nearly fifty nations met in Toronto and Geneva to address the climate change problem. The delegates formed the Intergovernmental Panel on Climate Change (IPCC), consisting of more than two thousand scientists from around the world, to assess systematically global warming science and policy options. The IPCC issued its first report in 1990, followed by second and third assessments in 1995 and 2001. Each IPCC report provided increasingly precise predictions of future warming and the regional impacts of climate change. Meanwhile, books like Bill McKibben's The End of Nature (1989) and Senator Albert Gore Jr.'s Earth in the Balance (1992) focused popular attention in the United States on global warming.

Yet these developments did not prompt U.S. government action. With its major industries highly dependent on fossil fuel consumption, the United States instead helped block steps to combat climate change at several international conferences in the late 1980s and 1990s. At the United Nations Conference on Environment and Development in Rio de Janeiro in 1992, U.S. negotiators successfully thwarted a treaty with mandatory limits on greenhouse gas emissions. As a result, the Rio conference adopted only voluntary limits. In 1993, the new administration of Bill Clinton and Albert Gore Jr. committed itself to returning United States emissions to 1990 levels by the year 2000. The administration also attempted to adjust incentives for energy consumption in its 1993 energy tax bill. Defeated on the tax bill and cowed when Republicans gained control of Congress in 1994, however, the Clinton administration backed away from significant new energy and climate initiatives.

At the highly charged 1997 United Nations Conference on Climate Change in Kyoto, Japan, more than 160 countries approved a protocol that would reduce emissions of carbon dioxide, methane, nitrous oxide, and three chlorofluorocarbon substitutes. In the United States, powerful industry opponents to the Kyoto Protocol, represented by the Global Climate Coalition (an industry association including Exxon, Mobil, Shell Oil, Ford, and General Motors, as well as other automobile, mining, steel, and chemical companies), denounced the protocol's "unrealistic targets and timetables" and argued instead for voluntary action and further research. Along with other opponents, the coalition spent millions of dollars on television ads criticizing the agreement, focusing on possible emissions exemptions for developing nations. Although the Clinton administration signed the Kyoto Protocol, strong Senate opposition to the agreement prevented ratification. In 2001, President George W. Bush withdrew his executive support for the protocol.

Growing Signals of Global Warming

By the end of the 1990s, climate science had grown increasingly precise and achieved virtual worldwide scientific consensus on climate change. The 2001 report of the Intergovernmental Panel on Climate Change concluded that global average surface temperature had increased by 0.6 degrees Celsius during the twentieth century, largely due to greenhouse gas emissions. Carbon dioxide concentrations in the atmosphere had increased by approximately 30 percent since the late nineteenth century, rising from 280 parts per million (ppm) by volume to 367 ppm in 1998.

By 2001, signs of global warming were increasingly widespread. With glaciers around the world melting, average sea levels rising, and average precipitation increasing, the 1990s registered as the hottest decade on record in the past thousand years. Regional models predicted widespread shifting of ecosystems in the United States, with alpine ecosystems expected largely to disappear in the lower forty-eight states while savannas or grasslands replace desert ecosystems in the Southwest. The IPCC 2001 report estimated an increase of between 1.4 and 5.8 degrees Celsius by 2100, a projected increase in global temperature very likely "without precedent during at least the last 10,000 years."

GLOBAL WARMING

Early Scientific Work

Developing Scientific Consensus

Global Warming Politics

Growing Signals of Global Warming

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