Ozone hole over Antarctica healing, says New Zealand scientist
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E-mail Xinhua, September 10, 2012
Ozone hole over Antarctica healing, says New Zealand scientist
WELLINGTON, Sept. 10 (Xinhua) -- International efforts to curb emissions of ozone-depleting substances appear to be paying off as the hole of the ozone layer over the Antarctic slowly diminishes, a New Zealand scientist said Monday.
However, it was too difficult to say when the ozone would return to natural levels because of the complexity of interactions between greenhouse gases and their impacts at different levels of the atmosphere, said Dr Adrian McDonald, of the physics and astronomy department at the University of Canterbury.
"Ozone levels above Antarctica are projected to return to 1980 levels (previous to the ozone hole) after 2050. The Montreal Protocol means that emissions of ozone depleting substances (CFCs) have largely been banned worldwide," McDonald said in a statement.
The thin layer of ozone about 25 kilometers up in the Earth's stratosphere acts as a filter of ultraviolet radiation from the sun, and its depletion has led to health and environmental problems in Southern Hemisphere countries such as New Zealand.
CFCs, which were once widely used in common household items such as refrigerators and aerosol sprays, were blamed for the hole in the ozone layer, but their uses were curbed under the Montreal Protocol which was agreed by the international community in 1987.
Most CFC emissions occurred in the Northern Hemisphere, but ozone depletion is a worldwide issue and global atmospheric air circulation has resulted in the worst hole in the ozone layer over Antarctica.
"The increasing ozone hole has until now acted to change the circulation of the southern hemisphere so that the strong winds linked to the jet streams have moved towards the pole," said McDonald.
The southward shift of jet streams due to the ozone hole had been linked to a range of climate trends at mid to high latitudes during summer, including warming over the Antarctic peninsula and cooling over the rest of Antarctica.
"Ironically, ozone depletion may have protected Antarctica from the worst of greenhouse gas-related warming. With the ozone recovery the future of Antarctic climate is less certain. Though the complex interactions in the atmosphere associated with climate change make this region particularly hard to predict. We have a lot of research to carry out so we can understand how ozone recovery will impact on the southern hemisphere," he said. Enditem
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