The ozone layer is the atmospheric layer that shields the earth from harmful ultraviolet radiation. There is disagreement concerning the extent to which chlorofluorocarbons (CFCs) and other chemicals in the atmosphere attack the ozone layer. Predictions of the resultant ozone depletion occurring globally in the next century have ranged from 3 percent to 18 percent as scientists work to understand this complex problem. Researchers examining the data in search of subtle annual changes in global ozone chemistry noticed that the South Pole's ozone concentration dropped more each October than in other months.รก Initially researchers did not believe the data was significant.
Scientists now know that an ozone hole exists over the entire continent of Antarctica every October and has been getting larger each year. The question now is whether this effect is a warning of a significant change in global ozone or simply an isolated scientific curiosity. Because of its potential importance, however, the ozone hole has generated considerable excitement in the scientific community.
The first indication that October ozone levels were dropping came from Joe C. Farman and his colleagues at the British Antarctica Society, which has measured ozone levels from Halley Bay, Antarctica, since 1957. In May 1985, Farman's group published a paper in Nature showing how total ozone values at Halley Bay were much lower in October than in March, which is an effect that did not appear in the 1957-1973 data. Scientists intrigued by Farman's findings went through the data taken by an instrument called the Total Ozone Mapping Spectrometer (TOMS) on the polar orbiting Nimbus-7 satellite launched by NASA in 1978. The seasonal drop in ozone was clearly apparent. The hole begins to form in the Antarctic Spring, about a month after the sun starts to graze the horizon. In early November, the hole starts to disappear, in part because the sun has been hig...