Ozone hole has shielded Antarctica from global warming
1 December 2009, by Tamera Jones
The hole in the ozone layer over Antarctica has shielded most of the continent from global warming, say scientists in the first ever comprehensive review of the state of the Antarctic climate.
The review, called Antarctic Climate Change and the Environment, is published today by the Scientific Committee on Antarctic Research (SCAR). It concentrates on changes in the region over the past 30 years.
Drawing on evidence from 100 scientists from 13 countries, it specifically focuses on the rapid warming seen in the Antarctic Peninsula, changes in ice cover over the entire continent, the effect climate change has had on plants and animals in the region, atmospheric carbon dioxide (CO2) levels and the differences between man-made changes and natural variability in the region.
The review puts together the latest research from the icy continent, addressing urgent questions about Antarctic melting, sea-level rise and changes in biodiversity. It also suggests areas for further research.
The scientists who contributed to the review were surprised to find that the ozone hole has delayed the effect of rising greenhouse gas levels on the continent's climate.
'The most astonishing evidence is the way that one man-made environmental impact - the ozone hole - has shielded most of Antarctica from another - global warming,' says the lead editor of the review, Professor John Turner of the British Antarctic Survey.
Strong winds surrounding the continent have intensified as a result of the ozone hole and have effectively isolated the continent from the warming that's happening elsewhere on the planet.
'The most astonishing evidence is the way that one man-made environmental impact - the ozone hole - has shielded most of Antarctica from another - global warming.'
Professor John Turner, British Antarctic Survey
This means that over the last 30 years, there's been little change in surface temperatures over most of Antarctica, with the exception of West Antarctica. The east coast of the Antarctic Peninsula in West Antarctica has warmed rapidly during the summer months.
Stronger winds have led to other changes. Around 90 per cent of the glaciers in the West Antarctic Peninsula have retreated in recent decades and sea-ice extent west of the peninsula has decreased.
In contrast, since 1980 the extent of Antarctic sea-ice has increased by 10 per cent in the Ross Sea region, a deep bay on the opposite side of West Antarctica to the peninsula.
Loss of ice west of the Antarctic Peninsula has led to changes in the numbers of tiny marine creatures called phytoplankton, which are at the base of the food chain and play a crucial role in absorbing CO2 from the atmosphere.
Rapid warming along the western Antarctic Peninsula, along with a switch from snow to rain in the summer months, has led to plant, animal and microbial communities to expand in newly available land.
The scientists also say people have inadvertently introduced 'alien' organisms like grasses, flies and bacteria.
But they are concerned that the expected recovery of the ozone hole this century will make the full effects of greenhouse gas increases felt across Antarctica.
The scientists also highlight that global CO2 levels are higher than they've ever been over the last 800,000 years. They say atmospheric levels of CO2 and methane are increasing at rates unlikely to have been seen in the geologically recent past.
Studies of sediments under recently lost ice shelves suggest ice shelf loss in some regions is also unprecedented over this time scale.
The scientists who contributed to the report maintain that human activity is linked to the changes they've seen in Antarctica.
Turner says, 'There is no doubt our world is changing and human activity is accelerating global change.'
But they hope that by integrating this multidisciplinary evidence into a single source, they'll help people who use the review understand the differences between environmental changes linked to the Earth's natural cycles, and those that are caused by humans.
The climate in the polar regions varies more than in other parts of the world, yet these remote regions are sparsely sampled. The researchers recommend that these regions should be monitored in much greater detail in order to detect changes.
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