Unfortunately the crisis will get much, much worse before ordinary people go "Wait, so, we're all going to die? How do we prevent that?" and the idea that it's too late isn't compatible with their model of the world so they will reach for increasingly crude "solutions" to what they have belatedly realised is a dire situation.

It might I suppose be fun to catalogue, what are the priorities? Do we kill all the poor people before we decide that maybe we can't afford to keep obligate carnivores as pets? How about the elderly? When do the animals kept for meat go, is that later? At some point I expect there's a backlash, a phase where the populists who insisted that say, if we just murdered everybody with the wrong skin colour, or the wrong religious beliefs or whatever that would fix it - well what if we kill the populists instead? But it won't last, following is in people's nature.

Fossil fuel consumption declines, belatedly, as the human population goes extinct. The mass extinctions eventually settle into a new order. The warm, damp rock is slightly warmer, for a while, and a few non-human niches expand and something else occupies them. And maybe one day an intelligent life eventually wonders why, according to the best available data, in the long depths of pre-history there was a weird climate spike. Huh.