A capped mechanic:
Once all ice on earth is melted, nothing can get worse. Why should anyone reduce their CO2 emission after the irreversible is done? The few ones who "reduce" it, did not do it for ecological reason but for the diplomatic one. My understanding of the evolution of global warming is rather limited, so I might say something non-sensical but... why this do not lead to a global game-over? If the Earth becomes uninhabitable, this should also lead to the end of all civilizations (and here: to the end of the game for everyone). Do not see it as a "hard" Game Over, but more like removing Food from tiles, leading to global rebellion and depopulation througth seething and starvation...
In the end, I think I am starting to figure out why I kind of disliked Apocalypse mode: the CO2 mechanic was already weird (and not realistic to some degree). Going wild on CO2 is leading to sudden random destruction instead to global waning of all civilizations was kind of a last straw for this mode. I understand why Apocalypse is more into "spectacular" and "RNG" approach (so: it was never made to please me), but this is highlighting me how the CO2 mechanic is quite weird to begin with outside of the Apocalypse mode.
Yeah, I was really disappointed by the implementation of Apocalypse mode for this reason. Like, random meteors tied to CO2 emissions? Why?
I would have been so much more interested in it if they'd stuck with a more scientifically-grounded worst case scenario for climate change. Imagine:
- forests burn almost immediately after regrown (without adding extra yields)
- jungles burn and turn into plains tiles that quickly loose their fertility
- freshwater lakes next to farms and cities dry up
- all non-forested plains tiles next to desert progressively turn into desert
- every river starts to flood, and floodplains are inundated nearly every turn (again without any bonus yields)
- tundra turns into "submerged" tiles as the permafrost melts
- aqueducts stop providing regular fresh water from mountains
- seas rise up to the ~70 meter rise that would actually happen if all land ice melted.