The world's coastal cities could be under water within a few hundred years, swamped by rising sea levels caused by melting glaciers and ice packs. It may also be far too late to do anything about it, according to a researcher who predicts that ice currently landlocked in the western Antarctic could dump 3.8 million cubic kilometres of meltwater into the world's oceans in as little as 200 years. Such an event would raise average sea levels by up to 20ft, according to Dr Michael Oppenheimer of the Environmental Defense Fund in a review article in the science journal, Nature.
Dr Oppenheimer hedges his predictions, given the difficulties in foretelling how climate might change and what conditions would be necessary to cause the entire western Antarctic ice pack to disappear.
His review is based on what is currently known about the massive ice sheets off Antarctica and the ground ice which these are thought to hold in place. The possible meltdown is not wholly dependent on our understanding of how warmer climate might melt ice at the surface, he explains. Far more interesting is what is happening thousands of feet below, where the ice rests on bedrock.
It can be much warmer there, warm enough to cause the ice to melt and meltwater streams to flow. He presents three scenarios of what might happen in the future. The most chilling is a sudden collapse of the ice pack, forcing sea level up sharply in 50 to 200 years. On the other hand, very little could happen, with new ice forming as quickly as ice melts underneath with only marginal change in sea levels.
The most likely, he believes, is a slower but inexorable sea-level rise of 13ft to 20ft, but taking place over 500 to 700 years, still uncomfortably close if you are a shoreline property speculator.
We don't have to wait nearly so long for the mid-latitude glaciers to go, however, according to research presented yesterday at a meeting of the American Geophysical Union in Boston, Massachusetts.
In the United States, western Europe, Africa, Russia, China and New Zealand glaciers are shrinking and disappearing at an alarming rate.
Researchers from the University of Colorado in Boulder found that the number of glaciers in Spain had dropped from 27 to 13 since 1980. Both the Alps and the Caucasus Mountains, in Russia, had lost about half their glacial ice in the last century, while New Zealand glaciers had shrunk by about 26 per cent since 1890.
Prof Mark Meier of Boulder said: "The rate of warming is unprecedented in the last 600 years, and the retreat of glaciers is probably unprecedented, too, although we do not have the figures to prove it. But I am convinced there is a detectable human influence in the pattern of climate change we are seeing."
--Additional reporting by PA
