What about that most of the ice is so far north though? 2 degrees can't effect much above/below a certain latitude when it 40 below all winter long, and a steamy 10 degrees in the summer.
10.000 years ago Neatherthal man walked along the outskirts of the glaciers of the last ice-age. One of which covered new-york and Chicago all year around and was a mile hight. The whole of Canada was covered by a massive icesheet. I think he said much the same thing as you do right now.
How much difference can 1 or 2 degrees make ?
Wouter
