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Scientists fear disaster by 2200

A DRASTIC climate shift such as a thaw of Greenland's ice or death of the Amazon forest is more than 50 percent likely by the year 2200 in cases of strong global warming, according to a survey of experts.

The poll of 52 scientists, looking 100 years beyond most forecasts, also revealed worries that long-term warming would trigger radical changes such as the disintegration of the ice sheet in West Antarctica, raising world sea levels.

"There's concern about the risks of massive changes in the climate system," said Elmar Kriegler of the Potsdam Institute for Climate Impact Research, lead author of the study.

Huge changes or "tipping points," which might also include a slowdown of the Gulf Stream current that keeps Europe warm, are often dismissed as unlikely or scaremongering.

The survey found that leading experts, when asked, reckoned there was a one in six chance of triggering at least one tipping point with a moderate temperature rise of between 2 and 4 degrees Celsius by 2200 from 2000.

But with a rise of between 4 and 8 degrees by 2200, the chances of surpassing at least one of five tipping points rose to 56 percent.

"The study shows that some of these events are not considered low probability," Kriegler said.

He said the poll was relevant to government policy makers because any of the climate shifts examined would have huge economic impacts.

"The results of the survey provide further evidence of the need for ambitious climate protection in order to minimise the risks of far-reaching consequences for our entire planet," Hans Joachim Schellnhuber, the institute's director, said.

Most likely of the five tipping points was the onset of a Greenland thaw that would make it largely ice free. Greenland contains enough water to raise world sea levels by 7 meters if it all melted.

Second most likely was the death of large tracts of the Amazon rainforest because of a drying trend, followed by the start of a disintegration of the West Antarctic ice sheet, which would raise sea levels by about 5 meters.

The other two potential tipping points, a collapse of the system of Atlantic currents including the Gulf Stream and a shift toward a constant El Nino warming of the Pacific Ocean, were considered far less likely.


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