Ice Sheet Melt - New Information

by Dave Lindorff Jul 6 2007

The bad news, so far completely ignored in the mainstream US media, comes from James Hansen, the top climate expert at NASA's Goddard Institute for Space Studies.

Hansen, lead author of a new scientific study published in the May issue of the British journal, Philosophical Transactions of the Royal Society, says that the slow melting of the Greenland and West Antarctic Ice Sheets predicted by the IPCC as the basis for their estimate of a rise in sea levels of only 59 centimeters (less than two feet) by the end of this century is wildly off the mark and doesn't fit current data on ice melting.

The reason for Hansen's much more dire outlook on the ice sheets' longevity is that the IPCC apparently did not consider the effect of a change in reflectivity of ice when the surface melts and becomes wet, a so-called "albedo switch," which Hansen says makes it much more absorptive of solar energy. As well, it is now known that instead of simply melting slowly from the top down, ice sheets form large surface pools of water, which both absorb more heat, and also melt their way through the ice, forming a kind of "Swiss cheese" effect that weakens the ice sheet structure. That same water then lubricates the sheet and allows it to move more rapidly to the sea. All of this makes loss of ice sheets much more rapid than in the IPCC model.

Similarly, there has been no reporting on Hansen's other warning, embedded in this same May Royal Society report--that failure to hold the global temperature rise to within about two degrees Fahrenheit (quite a challenge, and highly unlikely) could lead to massive release of methane from the arctic permafrost, thus tossing out all current predictions about the future (methane is 24 times as potent a global warming gas as carbon dioxide, and there are 400 billion tons of the stuff frozen as so-called methane cathrates under the permafrost).

http://www.smirkingchimp.com/thread/8548