For a look at what's actually projected for the climate, read the book Six Degrees by Mark Lynas, who read about 3,000 peer-reviewed papers and summarized them, with extensive references. It's quite frightening, and far beyond anything that human civilization has ever experienced, even at +2C. If we go all the way to +6 it's hard to imagine anyone surviving. Somewhere between +2 and +3, climate feedbacks kick in and take it several degrees further with no more help from us. Right now we're at +0.8.