Lol you're putting your faith in the same science that has consistently said "we got it wrong, it's actually much worse/happening much faster than expected", for the last decade - that has been the climate change song.

Systems are complex and their interactions often have wide reaching consequences.

Try maybe: a series of lethal Pandemic outbreaks caused by thawing permafrost, including a novel virus with a long incubation rate and also a very high mortality rate, at the same time as that same permafrost releasing gigatons of methane to poison the air (clathrate gun hypothesis), oceans dying along with the amazon, resultant shortages triggering a nuclear war/use of weaponized nanotech, viral/eugenic warfare, country's facing extinction deciding to fuck everyone else at the same time (US for example could carpet nuke most of the planet), on and on.