Here’s a reasonably good paper (well, good based on my pedestrian understanding of climate science) regarding the relative impact of possible CO2 mitigation:

http://www.nature.com/nature/journal/v468/n7326/abs/nature09653.html

(sorry to those of you that cannot get the Nature papers directly)

The general gist of the article seems to be twofold and of relatively good news. First they say that CO2 mitigation efforts could have a definite impact on the conditions in the arctic. As such, they find that we have not yet crossed a “tipping point” from which the reversal of changes becomes much more difficult. Secondly they do not seem to find any tipping point, at least in the short term, to exist. All of that should come as welcome news, especially if you happen to like polar bears. Figures 3 and 5 seem particularly easy to follow.