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Politics : Mainstream Politics and Economics
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To: Sdgla who wrote (19007)7/2/2012 9:44:46 AM
From: Wharf Rat  Read Replies (1) of 85487
 
I imagine some will persist, assuming Antarctica and Greenland don't move again. It'll be a while before Everest is ice free, too.

can determine this by looking at how the ice sheet has responded in the past. Some of the more optimistic emission scenarios from the IPCC predict warming of 1 to 2°C. The last time temperatures were this high were 125,000 years ago. At this time, sea levels were over 6 metres higher than current levels ( Kopp 2009). This tells us that the Greenland and Antarctic ice sheets are highly sensitive to sustained, warmer temperatures and that in upcoming centuries, we can expect sea level rise in the range of metres, not centimetres.

Further light is shed on Greenland ice sheet stability in a new paper The effect of more realistic forcings and boundary conditions on the modelled geometry and sensitivity of the Greenland ice-sheet (Stone 2010). This paper uses updated data on bedrock topography and ice thickness to produce more accurate modelling results of Greenland ice sheet behaviour. They model how the Greenland ice sheet will respond to three different scenarios with atmospheric CO2 held at 400 ppm, 560 ppm and 1120 ppm. The simulations are run over a 400 year period.

Although not completely collapsed, the 400 ppm ice-sheet loses ice mass in the north of the island, with a total reduction in ice volume ranging between 20 to 41%. Note - due to the large inertia of the Greenland ice sheet, this mass loss doesn't happen at the moment CO2 levels reach 400 ppm but over a period of centuries. Under a 560 ppm climate, the Greenland ice sheet loses between 52 to 87% of its ice volume. If CO2 reaches 1120 ppm, there is almost complete elimination of the Greenland ice sheet with loss between 85 to 92%. The important result from this paper is that there is a critical threshold where the Greenland ice sheet becomes unstable somewhere between 400 and 560 ppm.

skepticalscience.com
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