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Joined: 14 Jul 2003
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Ozone disappears
 Tue Nov 25, 2003 12:09 am
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South Pole ozone layer hole has disappeared: UN
Thu Nov 20, 6:37 PM ET
GENEVA (AP) - The seasonal "ozone hole" over the South Pole has disappeared again after reaching record size earlier this year, UN officials said Thursday.
The hole is a thinner-than-usual area in the protective layer of gas high up in the Earth's atmosphere. It has been forming in the extremely low temperatures that mark the end of Antarctic winter every year since the mid-1980s, largely due to chemical pollution. This year, the hole peaked at 28 million square kilometres in mid-September - matching the record size set three years ago.
Scientists have said the phenomenon results from destruction of the gas in the atmosphere by chemical compounds, such as chlorofluorocarbons released in some aerosols and refrigerants. The hole refills with surrounding ozone-rich air as temperatures rise.
In addition to its record size, researchers said this year's ozone depletion also persisted longer.
In October, researchers said the conditions raised concerns about more harmful UV radiation reaching Earth.
"The ozone hole size and persistence have developed similarly to the year 2000, with an early rapid growth observed during August, a record size observed in September and finally its disappearance in mid-November," said a statement by the World Meteorological Organization (news - web sites).
The use of chlorofluorocarbons has been curbed under a global accord and levels of the chemicals in the atmosphere have been declining. But scientists predict it will take about 50 years for the ozone hole to stop forming.
The lack of ozone can let harmful ultraviolet rays from the sun reach the Earth's surface, causing skin cancer and cataracts, as well as destroying tiny plants and organisms at the beginning of the food chain.
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