ENVIRONMENT REPORT
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ENVIRONMENT REPORT - Shrinking Ozone Hole over Antarctica
By Cynthia Kirk
Australian researchers say the hole in the ozone layer over Antarctica probably would start
closing within five years. They say it may be completely closed within fifty years. The ozone
layer protects the Earth from dangerous radiation from the sun. The hole in the ozone layer
was discovered over Antarctica almost thirty years ago. At the time, it was three times the size
of Australia.
Paul Fraser is chief researcher of the Commonwealth Scientific and Industrial Research
Organization in Australia. Mr Fraser led a study about the ozone layer for the United Nations
and the World Meteorological Organization.
The report found that ozone-destroying gases in the upper atmosphere had been at or near
their highest levels in the year2000. But since then, there has been continued progress toward
recovery of the ozone layer. Satellite information showed levels of ozone-destroying gases in
the atmosphere are slowly decreasing.
Chlorine from chlorofluorocarbons, or C-F-Cs, is responsible for destroying part of the ozone
layer over Antarctica. C-F-Cs have been widely used since the nineteen-thirties in cooling
devices such as refrigerators and air conditioners. C-F-Cs remain in the atmosphere for years.
Government scientists say the level of chlorine in the atmosphere is decreasing because of
restrictions on the use of chlorofluorocarbons. The chemicals were restricted under an
international agreement called the Montreal Protocol in 1987.
Under the Montreal agreement, developing countries promised to cut their use of
chlorofluorocarbons in half by the year 2005. They also agreed to an 85% cut by the year
two-thousand-seven.
The ozone hole forms over Antarctica in August and September, when the temperatures are
coldest. Thin clouds form in these cold conditions. Chemical reactions on the cloud particles
help chlorine-based chemicals to rapidly destroy ozone. By early October, temperatures begin
to warm and the ozone layer begins to recover.
At its largest this year, the ozone hole covered more than fifteen-million square kilometers.
That is down from an average of twenty-three-million square kilometers over the last six years.
