Colin Challen, a member of Parliament and chair of the All Party Parliamentary Climate Change Group, has a good editorial in the latest issue of Science (sub. rqd). He makes a key point that is often missed in the debate:
Not only must we reduce anthropogenic greenhouse gas emissions, we need a timetable that reduces the risk of positive feedbacks and sink failures that could lead to runaway catastrophic climate change.
We are "playing climate change poker," as Challen says, fighting not just to avoid the consensus prediction for climate change, but the plausible worst-case scenario, which is far worse. That's why even a 60 percent cut in emissions by mid-century may not be enough, and many are pushing for an 80 percent cut.
The entire editorial is reprinted here: