I did a couple of "AI only" games yesterday, just to see how the AI was playing GS: I must say that in both those games, the global warming rate was quite moderate. It didn't start to become bad until late atomic era and information era. I have played two games (besides the AI only thing) and in my first game the world was gone quickly and that was probably my fault. In my second game I actually try to think about how I played. I still built coal power plants, but not in every city (since I have learned that I don't have to) and the really bad effects of global warming kicked in fairly late. Sure, there will be "bad guys" among the AI from game to game, but it seems that the AI play this well, perhaps better than the human does. I must also say here that in all four of these games, not all of the civs entered the industrial era at the same time, only roughly half was on par with the global era. In games where all the civs go into the industrial era at the same time, can certainly speed up global warming.