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Friday, 11 February, 2000, 11:39 GMT
Limited sea rises expected
Antarctic ice sheet could increase in volume
Sea levels will rise by "several tens of centimetres" over the next century, according to Australian research.

The finding is based on a computer model of future climate change that assumes the Earth's surface temperatures will rise by two to three degrees over the coming century.

The Antarctic Co-operative Research Centre (CRC) says melting ice in both Antarctica and Greenland will cause some increase in sea levels, but stresses that we are unlikely to see the catastrophic melting forecast in some quarters.

The centre's director, Professor Garth Paltridge, told BBC News Online that he hoped the research would help dispel the myth that we are heading for a drowning world as a result of global warming.

Informed opinion

"Many of the public are still under the impression that there is a distinct possibility the ice cap on Antarctica will slide off into the sea and melt, thereby raising sea levels by quite disastrous amounts over the next few years or decades," he said.

"One often hears this sort of implication when, for instance, somebody reports that a particularly large part of an ice shelf has broken off from somewhere in Antarctica. It seems well worth while to make the point that informed scientific opinion does not agree with such extreme scenarios."

The Antarctic ice sheet is a very important focus for climate change research, not least because it helps to cool the Earth by reflecting the Sun's energy back into space. Were it to melt completely, it would add 55 meters to global sea levels. But the Antarctic CRC says this is not going to happen with a warming of just two or three degrees.

However, it is possible, it says, that the projected warming could increase the flow rate of grounded ice into the sea, adding perhaps one or two meters to sea levels over the next one or two thousand years.

Higher evaporation

The Antarctic CRC says its calculations suggest that a significant proportion of the slightly smaller Greenland ice sheet could disappear - but again over a period of millennia.

Indeed, the centre believes that in the short term, there will be relatively little melting of the ice-sheets with perhaps even an increase in volume of the Antarctic sheet as a result of greater snowfall caused by higher evaporation from warmer oceans.

Thus, for the next century or two, the rise worldwide in sea levels will come mainly from thermal expansion of the oceans and the melting of non-polar glaciers.

The findings are part of Australia's contribution to the Intergovernmental Panel on Climate Change (IPCC), an international body that is reviewing scientific estimates on long-term climate change. Part of the IPCC's role is to put together best-guess scenarios for the future.

Model problems

There will be some scientists who will reject this latest work because, like much of the other material assessed by the IPPC, it is based on computer models which sceptics of global warming regard as deeply flawed.

The models have to incorporate a multitude of complex interactions, including cloud formation, precipitation, oceanic heat transport and sea-ice formation. Many of these measurements have to be averaged otherwise the computing task would simply be impossible. Neither do we have a full understanding of some of these climate processes.

Critics argue that the task of forecasting climate accurately even ten years ahead is beyond current technology.

They also doubt the evidence that the Earth is currently experiencing a rapid warming, pointing to the inconsistencies in temperature records.

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