Civ 2 had pollution and rising sea levels due to melting ice caps. The most interesting unintended gameplay that came out of that must have been the Eternal War savefile:

https://civilization.fandom.com/wiki/Eternal_War_(Civ2)

Civ 1 had global warming as well, triggered by pollution (which can be a result of industry/city-size, but also as a result of using nuclear weapons). In my very first civ1 game, I eventually took over the Earth with nkues, in the 2500s, but it caused terrible global warming turning the whole world into swamp and desert, which in turn shrunk nearly all the cities down to size 1 due to famine.

https://civilization.fandom.com/wiki/Global_warming_(Civ1)