Sea Levels Rising Faster than ExpectedPolar ice is melting much faster than previously predicted and raising ocean levels more rapidly.
Sea level rises could bust official estimates – that’s the first big message to come from the climate change congress that kicked off in Copenhagen, Denmark, today.
Researchers, including John Church of the Centre for Australian Weather and Climate Research, presented evidence that Greenland and Antarctica are losing ice fast, contributing to the annual sea-level rise. Recent data shows that waters have been rising by 3 millimetres a year since 1993.
Church says this is above any of the rates forecast by the IPCC models. By 2100, sea levels could be 1 metre or more above current levels, he says. And it looks increasingly unlikely that the rise will be much less than 50 centimetres.
In 2007, the Intergovernmental Panel on Climate Change forecast a rise of 18 cm to 59 cm by 2100. But the numbers came with a heavy caveat that often went unnoticed by the popular press.
Because modelling how the Greenland and Antarctic ice sheets will react to rising temperatures is fiendishly complicated, the IPCC did not include either in its estimate. It’s no small omission: the Greenland ice cap, the smaller and so far less stable of the two, holds enough water that if it all melted, it would raise sea levels by 6 metres on average across the globe.
“As a result of the acceleration of outlet glaciers over large regions, the ice sheets in Greenland and Antarctica are already contributing more and faster to sea level rise than anticipated,” says Eric Rignot of the University of California in Irvine and NASA’s Jet Propulsion Laboratory. “If this trend continues, we are likely to witness sea level rise 1 metre or more by year 2100”, he says.
Church says even 50 cm would have a huge effect on flooding events. “Our study on Australia showed that coastal flooding events that today we expect only once every 100 years will happen several times a year by 2100,” he says.
Jason Lowe of the UK Met Office remains cautious. He accepts that recent data shows ice from Greenland and Antarctica is rapidly pushing up sea levels, but says the models simply are not yet sophisticated enough to say how this affects the future. Catherine Brahic, New Scientist
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