Not so fast. According to a new paper in Science (PDF here), the reality may not be so dire:
Specifically, if atmospheric carbon dioxide levels are to double from pre-industrial levels of 280 ppm to 560 ppm, the researchers say Earth’s average temperature is likely to rise from 1.7 to 2.6 Celsius degrees, a decrease from the previous, accepted range of 2 to 4.5 degrees.
source: Schmittner et al at 14
Oregon State's Andreas Schmittner, the paper's lead author, says
Many previous climate sensitivity studies have looked at the past only from 1850 through today, and not fully integrated paleoclimate date, especially on a global scale. When you reconstruct sea and land surface temperatures from the peak of the last Ice Age 21,000 years ago -- which is referred to as the Last Glacial Maximum -- and compare it with climate model simulations of that period, you get a much different picture.No wonder Canada and Europe are cooling on global warming.
If these paleoclimatic constraints apply to the future, as predicted by our model, the results imply less probability of extreme climatic change than previously thought.
(via Watts Up With That?)