I don't find it more absurd than unhappiness from "It's too crowded!", which has a pretty huge impact on the game right now.
Population pressure means resource scarcity, which absolutely makes people more likely to rebel.
Besides, as a gameplay mechanic it works well.
You don't think anyone would speak out if their leaders suddenly decided to chop down all forests in the surrounding area
No, not at all. This has happened many times through history, and the outcome is for people to be happy about all that newly cleared farmland.
Just look at Brazil today, its the locals doing the forest clearing.
Well, if you dislike not being able to do anything about it, and you dislike explicitly dealing with individual tiles to reduce pollution, how would you want to be able to do something about it?
I wouldn't, I'd cut the mechanic. Its intrinsically broken.
Just increase the unhealth benefits from industry, and then you can deal with them by building health-providing buildings.
I feel that you're missing the point. The affects of global warming are meant to be a bad thing. You're not meant to be thinking "wow, dealing with global warming is really fun, lets create a bunch of pollution so that I can experience the awesomeness of this feature".
Penalties from heavy industry that you have in your own empire is fine.
*Permanent* penalties from terrain degrading forever, and penalties that happen from what happens outside your empire, is NOT fine. Its broken.
It's like complaining that the process of dying in an FPS isn't fun. Sure it isn't, that's why you're meant to avoid it
Failed analogy. Its like dying in a FPS completely randomly because of something that happens outside your control, and then having to quit the game and reboot your computer before you can start playing again.
If it's an unavoidable pain in the ass then that would be bad for gameplay
It has been thus far.
it really is one of the biggest problems for the modern world
It might be, eventually, we'll have to see.
For most of the world I would argue that lack of clean water and the spread of drug-resistant infectious diseases are likely to be more significant.
But so what? Whether it is important or not IRL is not the point; its whether or not its fun in the game.
Having penalties that happen to you based on the industrialization of other empires is realistic, but it is in no way fun at all. Its not like you can negotiate an inter-government climate treaty in the game (or IRL it turns out).
Besides, playing in the real world today would be pretty boring. There's hardly any conflict, there hasn't been a major war in 65 turns, and most of the world have fairly good diplomatic relations with each other.
Environmental dystopia is a lame late-game. I'd rather much rather have a political/economic/military dystopia; think of the future options from alpha centauri and the like. Cyborgs, nanotechnology, cloning, arcologies, and so forth.
Cyberpunk is way cooler than resource depletion.