How much sea rise will climate change cause?

6/5/2009 New Scientist - Gaia VinceSea level has risen 52 millimetres on average in the past 15 years. Much of this can be put down to thermal expansion of the water, in which the molecules become agitated and move further apart as temperature rises. We know this is happening because sea level rise has so far been directly proportional to global warming. Some scientists, however, are concerned that melting ice may now have overtaken thermal expansion as the leading cause of sea-level rise. “How these factors will influence regional sea rise over the century is the great unknown,” says Steve Nerem at the University of Colorado in Boulder, who monitors sea-level rise.

While we wait for data, we are left with an array of models that vary widely in when they estimate sea level rise will swamp the Maldives. In its latest assessment, the Intergovernmental Panel on Climate Change predicted a rise of up to 59 centimetres by the end of 2100 - a figure that does not include glacial melting. At the other end of the scale, James Hansen’s group at NASA Goddard predicts a global sea-level rise of up to 25 metres by 2100, assuming that feedback mechanisms will accelerate melting in Greenland and Antarctica. More conservative models without feedback scenarios, such as that by Stefan Rahmstorf at the Potsdam Institute in Germany, put it at 1.4 metres by 2100.

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