http://www.guardian.co.uk/environment/2009/mar/10/greenland-ice-sheet-climate-change

This is interesting because for once things don't seem to be getting 
worse but better.

Chris

Greenland ice tipping point 'further off than thought'

Previous studies have misjudged the so-called Greenland tipping point at 
which the ice sheet is certain to melt completely, expert claims

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* David Adam in Copenhagen
* guardian.co.uk, Tuesday 10 March 2009 16.31 GMT
* Article history

Melting ice sheet in Greenland

The vulnerability of Greenland's ice has been overestimated, says a 
climate expert. Photograph: Corbis

The giant Greenland ice sheet may be more resistant to temperature rise 
than experts realised. The finding gives hope that the worst impacts of 
global warming, such as the devastating floods depicted in Al Gore's 
film An Inconvenient Truth, could yet be avoided.

Jonathan Bamber, an ice sheet expert at the University of Bristol, told 
the conference that previous studies had misjudged the so-called 
Greenland tipping point, at which the ice sheet is certain to melt 
completely. "We're talking about the point at which it is 100% doomed. 
It seems quite an important number to get right." Such catastrophic 
melting would produce enough water to raise world sea levels by more 
than 6m.

"We found that the threshold is about double what was previously 
published," Bamber told the Copenhagen Climate Congress, a special 
three-day summit aimed at updating the latest climate science ahead of 
global political negotiations in December over a successor to the Kyoto 
treaty. It would take an average global temperature rise of 6C to push 
Greenland into irreversible melting, the new study found.

Previous estimates, including those in the recent reports from the 
Intergovernmental Panel on Climate Change, said the critical threshold 
was about 3C – which many climate scientists expect to be reached in the 
coming decades.

"The threshold temperature has been substantially underestimated in 
previous studies. Our results have profound implications for predictions 
of sea level rise from Greenland over the coming century," the 
scientists said.

Bamber said previous studies used a very simple model to mimic how the 
Greenland ice will melt as temperatures rise. The new study, conducted 
jointly with colleagues in the US and Denmark, used a more complex 
simulation to better recreate the conditions in the real world. "I'm not 
saying it's definitely right, but more of the physics is in there."

He said evidence from past climates confirmed that Greenland should be 
able to survive temperature rises higher than 3C. An ice sheet about 
half the size is known to have persisted there during the Eemian period, 
about 125,000 years ago, when temperatures were about 5C higher than today.

Bamber said the new study was only concerned with the tipping point at 
which melting becomes unstoppable. It does not mean that Greenland will 
not contribute to increased sea level rise if temperatures increase by a 
few degrees.

"I'm not saying that if you have a temperature rise of 2C then you're 
not going to lose mass from Greenland, because you are. You warm the 
planet, ice melts," he added.