Sea levels will rise much faster over the next century than has been expected, even if governments are successful at controlling greenhouse gas emissions, scientists warned yesterday.
Advances in the understanding of the mechanisms that control how quickly ice sheets melt have shown that sea levels are likely to rise by a metre before 2100. The estimate is almost double the projection of 20cm to 59cm made in 2007 by the United Nations' Intergovernmental Panel on Climate Change. Equally worrying, the sea rises would continue to speed up and would have catastrophic impacts for generations, scientists were told at a conference in Copenhagen.
Professor Stefan Rahmstorf, of Potsdam Institute for Climate Change, said that unless greenhouse gas emissions were controlled within 50 years, the planet would be locked into rises of "tens of metres".
He presented data suggesting that a one-metre rise by the end of the century was the minimum that could be expected. "Sea level is rising faster than expected," he told the audience of climate change researchers.
"I'm afraid it's quite likely we'll get a substantially higher rise. Even for a low-emission scenario, the basic estimate here is above one metre. Sea level rise doesn't stop in 2100. We are setting in motion processes now that will lead to sea level rises for centuries to come. They will burden many generations coming after us."
Professor Rahmstorf said that analysis of previous sea level rises had shown a direct relationship between the amount of ice cover and the depth of seas.
In the Pleiocene period, three million years ago, temperatures were about 3C warmer and sea levels were 25-30 metres higher. Temperatures by the end of the century are forecast to rise by more than 6C if emissions are not reduced greatly and rapidly. Each degree of temperature was associated with "tens of metres" of sea level and, although Professor Rahmstorf was confident that the ice caps would lose nothing like that over the next 200 years, he said that the future of the Arctic and Antarctic would be decided in the next 50 years.
He said: "We could over the next 50 years commit the planet to major ice losses that would likely lead to the complete loss of ice sheet. We may be committing our planet to major sea level rises that will lose us many coastal communities."
Professor Rahmstorf was one of several of the world's leading researchers on sea levels and ice cap melting to address the conference. John Church, of the Centre for Australian Weather and Climate Research, said: "We need to recognise the ice sheet uncertainty. It could cross a threshhold where it commits the world over a long timeframe to many metres of sea level rise."
The worst-affected regions of the world are expected to be low-lying places such as Bangladesh, Burma, much of southeast Asia, parts of Africa, and island states. British towns and cities such as London, Hull and Grimsby also face severe problems.