The Ozone Depletion Phenomenon (1996) / Chapter Skim
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The Ozone Depletion Phenomenon
The Ozone Depletion Phenomenon
Pages 1-8
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~nder~tand nay tare often leads to practical results of immense societal benefit that could not have been anticipated when the research first began. The Problem For four months of every year, Antarctica's McMurdo Research Station lies shrouded in darkness.
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Although the entire increase cannot be blamed on ozone loss and increased exposure to ultraviolet radiation, there is evidence of a relationship. Scientists estimate that for each 1 percent decline in ozone levels, humans will suffer as much as a 2 to 3 percent increase in the incidence of certain skin cancers.
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Other less common compounds with an odd number of electrons known as free radicals readily undergo chemical reactions and do not survive for long. These compounds play crucial roles in such phenomena as urban smog, the loss of stratospheric ozone, and the global removal of .
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After developing such a detector, the British scientist James Lovelock, in 1970, became the first to detect CFCs in the air. He reported that one of these compounds, CFC-ll, had an atmospheric ~ 15 a)
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At this height, the harsh, high-energy ultraviolet radiation from the sun impinges directly on the CFC molecules, breaking them apart into chlorine atoms and residual fragments. If Rowland and Molina had ended their CFC study with these findings, no one other than atmospheric scientists would ever have heard about it.
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To make matters worse, other scientists had demonstrated that an entirely different group of compounds could fi~rther reduce ozone levels. Paul Crutzen first showed in 1970 that nitrogen oxides react catalytically with ozone, playing an important role in the natural ozone balance.
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In 1986 and 1987, these scientists, including Susan Solomon and Tames Anderson, established that the unprecedented ozone loss over Antarctica involved atomic chlorine and chlorine oxide radicals. At the same time, measurements in the lower atmosphere established that CFC levels had increased steadily and dramatically since the first recordings taken by Lovelock in 1970.
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Scientists estimate, for example, that if active research in stratospheric chemistry had not been in place at the time the ozone hole was discovered in 1985 and confirmed in 1986, global ozone depletion, measuring 4 percent today, would be close to 10 percent by the year 2000. Even larger ozone depletion would have been observed over the United States and Eastern Europe, substantially exceeding the current : ~B E Y O N D D I S C O V E n Y ..~jI measurements there of about 10 percent loss in winter and spring and 5 percent in summer and autumn.
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