December 1, 2009 – Original Source: New Scientist
A review of climate change in Antarctica forecasts that by 2100 the world’s seas will have risen to levels previously considered too extreme to be realistic.
The review, Antarctic Climate Change and the Environment (PDF), was compiled by 100 scientists associated with the international Scientific Committee on Antarctic Research. Using 20 of the most up-to-date models that take into account the complex behaviour of the ozone hole over Antarctica, as well as the most recent observations of ice loss, the review predicts that the area of sea ice around Antarctica could shrink by 33 per cent – 2.6 million square kilometres – by 2100, leading to a sea-level rise of 1.4 metres.
“This is the first comprehensive review of Antarctic climate change that covers how the climate of the icy continent has changed from deep time,” says John Turner of the British Antarctic Survey, lead editor of the report. The report also makes predictions about how the Antarctic climate will change over the next century.
For the past 30 years, the hole in the atmosphere’s ozone layer above Antarctica has protected the bulk of the continent from the effects of climate change by generating fierce winds. In that time, sea ice around the continent has increased by 10 per cent.
The new report warns that when the ozone hole heals – and it will, possibly by the end of the century – Antarctica will feel the full force of global warming, with temperatures rising by as much as 3 °C by 2100.
From sea ice to sea
The report backs the predictions of Stefan Rahmstorf at Potsdam University, Germany, whose own work suggests that given the speed at which West Antarctica’s ice sheets are shrinking, sea levels are likely to rise by 1.4 metres by 2100. In contrast, the Intergovernmental Panel on Climate Change’s Fourth Assessment, published in 2007, predicted 59 centimetres.
“I am not the one to judge my own paper, but there is indeed [some] indication that these higher numbers – not only from my study, by the way – are now the new mainstream,” says Rahmstorf.
The IPCC’s sea-level rise projections are considered to be conservative, as they don’t take into account the fact that Antarctica’s loss of ice will accelerate as temperatures rise over the continent.
By 2100, the West Antarctic Ice Sheet alone could lose enough ice mass to raise sea levels globally by “tens of centimetres,” Turner says.
Despite the transformations climate change will create on Antarctica, the study concludes on an upbeat note: only a few of the continent’s species are likely to become extinct by 2100.
Many marine creatures can survive a change in temperature of 5 to 10 °C before dying, but “a rise of this magnitude in the Southern Ocean is extremely unlikely by 2100”, the study says.