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A Bad Case of Gas

A getting-of-wisdom guide to the causes and consequences of an 'enhanced' greenhouse effect By Christopher Weir GLOBAL WARMING IS AN EXTRAPOLATION of a natural phenomenon called the "greenhouse effect." For more than a billion years, the greenhouse effect has encouraged and sustained life as we know it. It occurs today when about 60 percent of ultraviolet solar radiation evades atmospheric and surface reflection. This energy is absorbed by the planet and then jettisoned back toward space in the form of a lower-intensity infrared radiation. Some of this "heat" energy, however, is trapped by a layer of gases, a process that mimics the effect of a greenhouse. The result is a generally hospitable average earth temperature of about 60 degrees Fahrenheit. The natural gases that compose the earth's 12-mile-deep atmospheric greenhouse layer include water vapor, carbon dioxide, nitrous oxide, methane and ozone. The term "global warming" suggests an "enhanced" greenhouse effect in which an accelerated and prolonged rise in global temperatures is directly related to human activities, most notably fossil-fuel combustion. "We are essentially throwing a thermal blanket around the planet and slowly warming it," says Sierra Club's Daniel Becker. Although some maintain that a significant human effect on climate has yet to be proven, the Intergovernmental Panel on Climate Change concludes that a 30 percent increase in atmospheric carbon dioxide levels has contributed to an overall warming trend over the past century. Other industrial pollutants, such as sulfate aerosols, can temporarily offset localized warming by increasing solar reflectivity. Therefore, an enhanced greenhouse effect caused by pollution would be manifest as a mosaic of complex interactions within an even more complex natural weather dynamic. Warming would not occur at a steady global pace, but rather as an uneven amalgam of generally increasing regional temperatures. While global warming popularly connotes droughts and heat waves, researchers note that ice melting and heightened evaporation would create a schizophrenic climate conducive to floods and violent weather systems. [ Metro Santa Cruz | MetroActive Central | Archives ]