Bob Barker reminding you: Help control the Liberal population! Have your Liberals spayed or neutered!
Back to global warming in Civilization:
I really don't care if global warming is real or not as far as the game's concerned. I'm a Civilization traditionalist, which means I'm for keeping features in the game so long as they aren't annoying or unbalanced. Global warming has been in since Civ 2 at least (don't know about 1) with varying ranges of effects.
In Civ 2, if you had a lot of polluted squares, it could trigger global warming (you got a warning first) which would change about half the squares on the map to something worse (jungle, etc.) While this was annoying it didn't necessarily ruin the game, and you had a chance to clean up the pollution first to stop it.
In Civ 3, GW was caused by pollution, and it would cause terrain to change/disappear ("global warming has turned forest into plains!") Again, this was a little annoying but not a game-breaker.
Now, in Civ 4, what do we have? Tiles get turned into desert. Yep, that's right, desert--no food, usually no production, and maybe one or two commerce. If it happens enough, your cities will begin to starve and there's nothing you can do about it.
The two problems I have are 1) it's not linked to pollution/unhealthiness, but only to nukes; and 2) there's not a bloody thing you can do to combat it. Whatever you want to say about real GW, most of the environmentalists like Al Gore say there's something you can do to slow it down. Even if there weren't, assuming humans can affect it at all, so what? The sun will eventually explode and kill all life on Earth in about 5 billion years, too (with other disasters coming long before then.) I'm not aware that there's anything we can do except leave before it happens. Should we put that in the game, too? No, because it's not fun to have your whole map disappear and for you to lose the game just because the RNG decided it's time to go nova.
So I'd say GW should be in, if for no other reason than I prefer to keep "traditional" mechanics in Civ as long as they're good. Trouble is, this is not the traditional way it's been done--you used to be able to combat it. Firaxis dropped the ball on this one.