LONDON: The hole in the Earth's ozone layer has protected Antarctica from the worst effects of global warming until now, according to the most comprehensive review to date of the state of the Antarctic climate. But scientists warned that as the hole closes up in the next few decades, temperatures on the continent could rise by about 3 degrees on average, with melting ice contributing to a global sea-level increase of up to 1.4 metres.
The western Antarctic peninsula has seen rapid ice loss as the world has warmed, but other parts of the continent have paradoxically been cooling, with a 10 per cent increase in ice in the seas around the region in recent decades. Many climate change sceptics have used the Antarctic cooling as evidence against global warming.
John Turner of the British Antarctic Survey said scientists are now ''very confident'' that the anomaly had been caused by the ozone hole above Antarctica. ''We knew that, when we took away this blanket of ozone, we would have more ultraviolet radiation. But we didn't realise the extent to which it would change the atmospheric circulation of the Antarctic.''
These changes in weather have increased winds in the Southern Ocean and meant that a large part of the continent has remained relatively cool compared with the western peninsula. But because the chlorofluorocarbon gases that caused the ozone hole have now been banned, scientists expect the damage to repair itself within the next 50 to 60 years. By then the cooling effect will have faded away and Dr Turner said the Antarctic would face the full effects of global warming.
This means an increase in average air temperatures of about 3 degrees and a reduction in sea ice by about a third.
The biggest threat to the continent comes from warming seas. Robert Bindschadler, a glaciologist at NASA who monitors Antarctic ice sheets, said: ''The heat in the ocean is getting underneath the floating ice shelves, these floating fringes of the ice sheet that are hundreds of metres thick. That warm water is melting the underside of the ice shelf, reducing the buttressing effect.''
Published by the Scientific Committee on Antarctic Research, a coalition of experts that co-ordinates research in the region, the report has been published to give negotiators in Copenhagen the most up-to-date science available. ''Everything is connected - Antarctica may be a long way away but it is an important part of the Earth's system,'' said Colin Summerhayes, the executive director of SCAR.
SCAR's review also corroborated recent work by Stefan Rahmstorf, a climate scientist at the Potsdam Institute for Climate Impacts Research in Germany, which says average sea-level rises will be closer to 1.4 metres by the end of the century. This is higher than the rise predicted by the Intergovernmental Panel on Climate Change in 2007, Dr Turner said, because the IPCC's forecasts did not include the impact of melting ice sheets on sea level rises. Many of the climate models used by the IPCC have also not taken the ozone hole into account in their simulations.