Recent conflicting reports about whether Antarctica is warming or cooling can now at least be explained – it is all the fault of the ozone hole.
Changing wind patterns triggered by the ozone hole are causing some areas to warm while others cool, says a new study by David Thompson of Colorado State University in Fort Collins.
The temperature changes are so great that they are swamping the gradual warming trend caused by the greenhouse effect. Thompson says that the ozone hole has become “the largest and most significant” cause of climate change on the ice continent.
The climate around Antarctica is dominated by strong westerly winds that swirl around a giant vortex of cold air that forms over the continent for much of the year. This polar vortex stretches from the ground into the stratosphere.
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In the past 20 years, pollution has destroyed much of the ozone layer over Antarctica. That in turn has cooled the stratosphere by as much as 10°C. The cooling does not extent to ground level, but it has had the effect of strengthening the polar vortex and the westerly winds. This in turn, says Thompson, has caused the big changes in weather patterns at ground level that have alarmed climate scientists.
Blowing hot and cold
British scientists working in the Antarctic peninsula have reported that region warming by 2 or 3°C in recent decades – several times faster than the average global warming trend. But meanwhile other parts of the continent, such as the Ross Sea region in the east, have become cooler.
Until now, this patchwork has confused climate scientists, who had expected a general but gradual warming from the greenhouse effect. And the protagonists on opposite sides of the debate about global warming have chosen the data that suits their cause.
Now Thompson’s examination of trends in ozone, the polar vortex, wind and temperatures over the past 30 years implicates the ozone layer, and not global warming, for most of the climate change in Antarctica.
Howard Roscoe, at the British Antarctic Survey in Cambridge, says: “I agree it is probable the ozone is partially implicated.” But he adds that much of the warming at Faraday, the former British station on the Antarctic peninsula, “occurred between 1950 and 1969 – before the ozone hole started”.
The ozone hole and global warming are different phenomenon, caused by largely different pollutants. Massive reductions in emissions of the chemicals that eat the ozone layer are predicted to heal the hole after about 2020. But global warming is far from under control and it seems likely that in the long run, all of Antarctica can expect to get hotter.
Journal reference: Science (vol 296, p 895)
