It鈥檚 official: there is nowhere left to hide from global warming. The notion that Antarctica is the last continent not to be heating up because of climate change is dead, according to a new study.
The results suggest that the southernmost continent is warming roughly as fast as the rest of the planet. They overturn previous suggestions that only the Antarctic peninsula, which stretches points north towards South America, was heating up while the continent鈥檚 interior cooled.
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When the Intergovernmental Panel on Climate Change published its 2007 report, it declared: 鈥渋t is likely there has been significant anthropogenic warming over the past 50 years averaged over each continent (except Antarctica)鈥�.
The exception wasn鈥檛 made because there was proof that Antarctica was cooling, says Gareth Marshall of the British Antarctic Survey, but because there was not sufficient proof that the continent was warming. Since then, data from isolated parts of the seventh continent have confirmed Antarctica is not immune to global warming.
And now, of the University of Washington, Seattle, and colleagues have used satellite data covering the entire continent to show that on average the entire continent warmed by 0.5掳C between 1957 and 2006. On average, the planet has warmed 0.6掳C in 50 years.
Sparse data
The majority of weather stations on Antarctica sit around the coast, with only two providing an unbroken record from the continent鈥檚 interior. Steig and colleagues overcame this lack of data by using satellite data and statistical techniques to fill in the gaps.
鈥淓ric has done a very clever analysis with extremely sparse data,鈥� says David Vaughan of the British Antarctic Survey, whose scientists were not part of the study.
The results (see map) show that the continent is not warming uniformly. Temperatures on the West Antarctica ice sheet, which includes the Antarctic peninsula and is as large as California, Texas, Alaska and Kansas put together, are rising much faster than in East Antarctica.
Climate model simulations provided clues about the cause of the warming, and point to the decline in regional sea ice cover and atmospheric circulation. 鈥淚t is almost certain that greenhouse gases are contributing to the warming but from this data it is difficult to say how much,鈥� says Steig.
Fragile ice sheets
The west Antarctic ice sheet more likely to collapse, causing global sea levels to rise, than the east Antarctica ice sheet 鈥� in 2002 the Larsen B ice shelf virtually vanished and the Wilkins ice shelf is currently teetering on the edge of collapse.
However, Vaughan cautions that Steig鈥檚 results do not mean the ice is even more fragile than previously thought. 鈥淚f you change surface temperatures from -50掳C to -40掳C it makes no difference to the ice,鈥� he says. Antarctic ice shelves are breaking up because of rises in sea surface temperatures, not air temperatures.
Vaughan was speaking from Antarctica where he and his colleagues are monitoring the Wilkins ice sheet. 鈥淔rankly, most of us are surprised that it is still here,鈥� he told New 杏吧原创, 鈥渂ut there was a lot of snow this year鈥�. The team have placed a GPS receiver on the ice shelf to track its movements but Vaughan says they expect it to disappear by the end of the austral summer.
Journal reference: (, in press)
