What causes global warming?

[MasterDave]

I got global warming happen twice in a game last night where I had no nuclear weapons, had passed Non-Proliferation before Manhattan Project was built, and no power plants at all! (I had Three Gorges Dam). The cities that were hit were two of my higher-producing cities, and both had forges, factories, airports, and laboratories. One of them may have had a drydock. Both used hydro power.

I guess global warming not tied to nuclear fallout is just one of those many undocumented features.

Diadem: Cleaning all of the pollution in Civ3 used to drive me crazy with its tediousness. It made an already slow endgame draaaaaag. I am very glad that that whack-a-mole crap isnt there any more. I do think that the current unhealthiness penalty could be more drastic, perhaps affecting production and commerce as well as city growth, much like polluted tiles affected the player in Civ3.

[Common Sensei]

There's two theories I'd put forth. First, perhaps the game tracks worldwide unhealth and the more total unhealth, the more likely you are to have global warming. The number would be probably pretty high so that you'd reach it in the modern age when all of the large cities add to that number.

From various past games where I've had spies wandering around rival sims, they certainly seem to build coal plants. If the above is true, perhaps the AI generates as much worldwide unhealth as possible to make it difficult for you?

Second, maybe any city in the industrial age forward that is unhealthy and losing food is a polluting, smog city and contributes to global warming.

[mblaschke]

I'm wondering what can be done about global warming because it's ruining my current game. It's happening every 3-4 turns and is ruining some of my best terrain. I've built recycling centers in most cities to no avail. I will go back and invest in other structures to reduce unhealthiness to try to get it under control. If it continues at this rate, the world will soon be uninhabitable.

To my knowledge, no nukes have been fired.