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U.N. scientists: Arctic ozone appears to have recovered for now

By Jonathan Fowler, Associated Press, 4/24/2001 15:37

GENEVA (AP) The protective ozone layer over the North Pole appears to have stabilized after years of thinning, but the gain may be temporary, U.N. weather experts said Tuesday.

Scientists from the United Nations' World Meteorological Organization said the recovery may be attributed to a warmer than usual winter and the current peak in the 11-year cycle of the sun, and not to global cuts in the use of harmful chemicals.

''At the peak of the solar cycle there's an intensity of radiation that produces more ozone,'' said Michael Proffitt, a senior scientific officer at the organization.

''Therefore you're going to find less sign of ozone depletion.''

The sun is now moving back into an 11-year period of declining radiation, meaning the production of ozone will be at its lowest in 2006, said Proffitt. Also, a return to colder winters would likely cause Arctic ozone levels to fall faster, he said.

Ozone depletion has already produced an annual hole in the layer in the stratosphere high above the South Pole.

Depletion of the ozone layer over the Arctic and Antarctica is being monitored because ozone protects Earth from harmful ultraviolet radiation. Too much UV radiation can cause skin cancer and destroy tiny plants.

The hole in the layer above Antarctica is believed to have caused a rise in skin cancer cases in Australia, Chile and Argentina.

Arctic ozone depletion starts in November, when sunlight triggers chemical reactions in cold air trapped over the North Pole during the winter. It intensifies during January and February before tailing off in April as temperatures rise.

Circular winds, known as a vortex, trap air, giving chemicals the chance to react with the ozone.

Scientists are establishing a link between global warming and ozone depletion, Proffitt told The Associated Press.

''In essence, warmer temperatures in the atmosphere mean cooler temperatures in the stratosphere, where the ozone is,'' he said. ''And cold means ozone depletion.''

In 1989, a gradual, global ban was imposed on chlorofluorocarbons, chemicals commonly used in aerosol sprays, refrigerators and air conditioners.

Chloroflourocarbons contain chlorine, one of the major destroyers of ozone.

But bromides, another destroyer often used in weed and pest killers, are not being eliminated as quickly, particularly in developing countries.

''Even with the cut in chemical use, it's going to be at least 50 years before ozone levels recover,'' said Proffitt.

Measurements of ozone depletion vary from year to year, making it difficult for scientists to determine the long-term environmental impact of changes in the ozone layer.

''The atmosphere is a delicate balance of things,'' said Proffitt. ''When we start disturbing it, we don't really know what it will do.''

-- Anonymous, April 25, 2001