Genesis of Eden
Carbon-dioxide Emissions Scientific American 1996
Certain gases in the atmosphere allow visible light to pass through, but they block much of the heat reflected from Earth's surface-in the same fashion as the glass windows in a greenhouse. Without this greenhouse effect, worldwide temperatures would be lower by 35 degrees Celsius, most of the oceans would freeze, and life would cease or be totally altered. According to the theory of global warming, an increase in greenhouse gases in the atmosphere will produce unacceptable temperature increases. A doubling of the volume of gases, for example, would cause temperatures to go up by 1.5 degrees C or more, a phenomenal change by historical standards. The most dramatic consequence of the warming would be a rise in sea level from the melting of polar ice caps, a rise that the Environmental Protection Agency projects to be 20 feet as early as the year 2300-sufficient to submerge large parts of coastal cities. Global warming would result in profound shifts in agriculture and may, as some have suggested, hasten the spread of infectious diseases. Aside from water vapor, the principal greenhouse gases are carbon dioxide, resulting from the burning of fossil fuels; methane, produced by the breakdown of plant materials by bacteria; nitrous oxide, produced during the burning of fossil fuels and by the decomposition of chemical fertilizers and by bacterial action; and chlorofluorocarbons, used for industrial and commercial purposes, such as air conditioning. Of these, carbon dioxide is the most important. The atmospheric concentration of C02 was 280 parts per million before the Industrial Revolution; with the increasing use of fossil fuels, it has risen to more than 350 parts per million today. The idea of global warming gained support as temperatures soared to record levels in the 1980s and 1990s, but there are several problems with the theory, including doubts about the reliability of the temperature record. Despite this and other questions, a majority of climatologists feel that a risk of global warming exists, although there is much disagreement concerning the extent and timing. (One of the uncertainties is the possibility that large amounts of methane now locked in Arctic tundra and permafrost could be rapidly released if warming reaches a critical point.) At the 1992 United Nations Conference on Environment and Development, more than 150 countries signed the U.N. Framework Convention on Climate Change, which pledges signatories to control emissions of greenhouse gases. In 1992 the Persian Gulf states of Qatar and the United Arab Emirates had the highest per capita emissions of carbon dioxide-16.9 and 11.5 metric tons, respectivelywhereas the U.S. was in eighth highest place with 5.2 metric tons. Overall, the U.S. produced 23 percent of global emissions, western Europe 14 percent, the former communist countries of eastern Europe 20 percent, and Japan 5 percent. Of the developing countries, China was the biggest contributor in 1992 with 12 percent, followed by India with almost 4 percent. Although emissions have more than tripled during the past 40 years, they showed signs of leveling off in the late 1980s and early 1990s. -Rodaer Doyle