Comment by nostrademons

Yeah. There's a whole hierarchy from "inconvenient weather" to "natural disasters" to "cities wiped off the map" to "civilization collapse" to "all civilization collapses" to "we're back in the stone age" to "humanity goes extinct" to "vertebrates go extinct" to "almost everything goes extinct" to "earth can no longer support life as we know it". Each level is a couple orders of magnitude more severe than the last, and each level is a couple orders of magnitude less likely.

The first is already happening. The second is highly likely. #3 and 4 are possible, but beginning to strain the bounds of likelihood. Somehow whenever global warming comes up people tend to jump to the last level, ignoring all the other steps and the massive reduction in complexity that has to happen without adaptation from any other lifeform for us to get there.