Reporter 434, 29 March 1999

Ozone oh-no revealed at University

Recent repairs to the ozone layer could be completely wiped out by a phenomenon discovered by a University researcher. The process could undo all the environmental benefits of banning CFCs.

Ken Carslaw at the Environment Centre and colleagues working in Germany and Switzerland suggest the thinning of the protective layer above the Arctic depends on temperature - and will accelerate with global warming. They believe nitric acid high in the polar stratosphere protects ozone by mopping up harmful chemicals, including chlorine. As carbon dioxide emissions trap warm air in the lower atmosphere, less heat escapes to the higher reaches. The resulting lower air temperature in the ozone layer allows cloud particles to form and fall, taking the ozone-protecting nitric acid with them.

Their results - published in Science this week - are among the first to link global warming with ozone depletion, and suggest the anticipated recovery of the ozone layer may have to be reviewed. Based on measurements and model projections, the researchers estimate future climate changes could completely reverse the benefits of reduced CFCs until the end of the 21st century.

"We've known for years this damaging process occurs at the much colder Antarctic, but finding evidence of it in Arctic ozone is very worrying," said Dr Carslaw.

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