Hi,
Count Iblis II, where did you get that figure? "It takes a few hundred years before all the Greenland ice cap can melt". How about two years?
This was what I was most interested in when originally studying glaciation/interglacial period boundaries. The conventional wisdom was that it takes three thousand years for a transition but the evidence just did not support that. The last glaciation ended at 11,300 years ago. There is a bit of an argument about the exact time but not too much about its rapidity. This one did not take thousands of years.
Now at 11,500 years, there was permanent ice over Chicago, over middle Europe. It was of comparable thickness and apparent permanency to Greenland. The difference is Greenland (which really should have been called Iceland and Iceland-Greenland but that is a naming mishap with a whole other story attached) is in the very high latitudes where it is cold. Funny that.
This means that for much of the time the prevailing weather (not climate, weather, the day to day stuff that affects what happens in days or weeks) means that ice will not melt. However, it snows in Denver and ice covers New York for periods of each year. Does this mean that it will stay there? No. The reason is that the climate of the region allows the area to warm beyond the point where ice coverage remains sustainable.
Greenland is in an area where the climate basically says, "stay covered in ice". But the balance is really very small. Ice melts very quickly indeed but in large quantities it creates its very own climate. That is the reason for glaciers in areas where the climate would not support them. They have created their own climate which has sustained them for thousands of years beyond when they should have melted.
From all of this, most people would assume a large ice mass in a very high latitude would take its own good time to melt regardless of global warming and they would be wrong. Their arguments would seem very valid but the evidence from the last melts just doesn't support it.
And this is where it actually gets complicated. Large quantities of ice create its own climate, leading to stability in the face of average temperature fluctuations. But even small changes in ice coverage can have devistating effects to the extent of ice coverage despite this seeming stability. The reason is partly due to the immense albedo difference between ice coverage and what remains when ice melts (95% down to around 35%). Instead of all the solar radiation being reflected away from the surface as with high albedo, it is absorbed, warming the ground at the ice boundaries and causing thawing.
It has a number of names but the one I like is the "snow blitz theory". More snow and ice means a higher albedo therefore less warming leading to ... wait for it ... more snow and ice. The reverse works just as well but much much faster. Of course it works better in lower latitudes where the energy per square metre from the solar radiation is a much higher unit anyway but it still works all the way to the poles due to the earth's tilted axis.
An average 5.8 degree temperature increase would be much more than enough to cause a massive retreat of snow and ice in the very short term. Oh, and there are a number of peer review articles available (most a few years old now but still valid none the less) concerning the argument as to the rapidity of global changes during the flip between glaciations and interglacial periods (a large rise in world temperature would be pretty much the same except the flip would be between an interglacial period and a super hot interglacial period - assuming the ice age did not end because of it).
The argument was a major one around 35 years ago when global warming was of no importance to anyone but scientists still had an interest in climate as an acadamic pursuit for its own sake. Before huge amounts of money was available to act as oracles rather than research scientists (Now that is a personal and rather pointed opinion of mine and not subject to peer review).
Richard
