Global Climate Change
The Effects of Greenhouse Gases
The increases during the past century in the atmospheric concentrations of greenhouse gases, especially carbon dioxide, has been unambiguously established. The potential consequences of these increases are controversial and the appropriate policy responses are even more controversial. The conclusions of the Intergovernmental Panel on Climate Change, as put forth in 2001 in its Third Assessment, represent the “conventional wisdom” of the world community of atmospheric scientists—although not a unanimous opinion.Theconclusions depend on both the scenario assumed for energy production during the coming century and the results of complex computer models of theresponse of the environment to the input of greenhouse gases. There is a wide range in the quoted effects, reflecting uncertainties in the atmospheric models and in future rates of greenhouse gas production. The projected effects for the period until 2100 include the following:
◆ An increase in global average temperature on the Earth’s surface of 1.4◦C to 5.8◦C (2.5–10.4◦F). About one-half of this rise is anticipated to take place by 2050.
◆ Increased average global precipitation.
◆ A rise in the average sea level due to the melting of glaciers and the thermal expansion of the oceans, by an amount projected to lie in the broad interval of 9–88 cm.
◆ Increased frequency and intensity of “extreme events,” including “more hot days, heat waves, heavy precipitation events, and fewer cold days,” with possibly “increased risks of floods and droughts in many regions”
The IPCC warns that “large-scale, high-impact, nonlinear, and potentially abrupt changes” could be caused by the greenhouse gases . These changes might be irreversible, locked in by positive feedbacks associated, for example, with greater emissions of greenhouse gases from the soil when the temperature rises. Most of these possibilities are stated in broad terms, reflecting the uncertainties. Additional warnings are contained in a 1997 book by Sir John Houghton, then co-chairman of the Scientific Assessment Working Group of the IPCC and chairman of the United Kingdom’s Royal Commission on Environmental Pollution. He pointed out that storms and floods claimed over 700,000 lives in the period from 1947 to 1980 and suggested that the projected climate changes are likely to lead to more frequent and severe floods (and droughts). Some models suggest an increased intensity of storms as well, but this effect is not well established. Even a slight increase in the frequency or severity of floods and storms could mean many additional casualties.
A potentially devastating, but also quite uncertain, possibility is the collapse of the West Antarctic Ice Sheet. If it occurs, it would cause a 5-m rise in sea level, affecting millions of people living in low-lying coastal regions. In the words of Houghton, “there is no reason to suppose there is a danger in the short-term (for instance, during the next century) of the collapse of any of the major ice sheets”. The IPCC report suggests a somewhat longer time scale, indicating that “after sustained warming the ice sheet could lose significant mass and contribute several meters to the projected sea-level rise over the next 1000 years”.
In ordinary thinking, a danger postponed 1000 years is not a matter of much concern. However, the discussions of nuclear waste disposal—where EPA regulations establish a 10,000-year period of responsibility and suggest considering a longer one—point up the question of our responsibility to future generations. How concerned should we be if our actions today may impact people hundreds or thousands of years from now?
◆ An increase in global average temperature on the Earth’s surface of 1.4◦C to 5.8◦C (2.5–10.4◦F). About one-half of this rise is anticipated to take place by 2050.
◆ Increased average global precipitation.
◆ A rise in the average sea level due to the melting of glaciers and the thermal expansion of the oceans, by an amount projected to lie in the broad interval of 9–88 cm.
◆ Increased frequency and intensity of “extreme events,” including “more hot days, heat waves, heavy precipitation events, and fewer cold days,” with possibly “increased risks of floods and droughts in many regions”
The IPCC warns that “large-scale, high-impact, nonlinear, and potentially abrupt changes” could be caused by the greenhouse gases . These changes might be irreversible, locked in by positive feedbacks associated, for example, with greater emissions of greenhouse gases from the soil when the temperature rises. Most of these possibilities are stated in broad terms, reflecting the uncertainties. Additional warnings are contained in a 1997 book by Sir John Houghton, then co-chairman of the Scientific Assessment Working Group of the IPCC and chairman of the United Kingdom’s Royal Commission on Environmental Pollution. He pointed out that storms and floods claimed over 700,000 lives in the period from 1947 to 1980 and suggested that the projected climate changes are likely to lead to more frequent and severe floods (and droughts). Some models suggest an increased intensity of storms as well, but this effect is not well established. Even a slight increase in the frequency or severity of floods and storms could mean many additional casualties.
A potentially devastating, but also quite uncertain, possibility is the collapse of the West Antarctic Ice Sheet. If it occurs, it would cause a 5-m rise in sea level, affecting millions of people living in low-lying coastal regions. In the words of Houghton, “there is no reason to suppose there is a danger in the short-term (for instance, during the next century) of the collapse of any of the major ice sheets”. The IPCC report suggests a somewhat longer time scale, indicating that “after sustained warming the ice sheet could lose significant mass and contribute several meters to the projected sea-level rise over the next 1000 years”.
In ordinary thinking, a danger postponed 1000 years is not a matter of much concern. However, the discussions of nuclear waste disposal—where EPA regulations establish a 10,000-year period of responsibility and suggest considering a longer one—point up the question of our responsibility to future generations. How concerned should we be if our actions today may impact people hundreds or thousands of years from now?
posted by Nuclear Engineer @ 1:21 AM
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