I recall hearing about this one informal conference between climate scientists, ethnographers, and collapse-aware economists. About two dozen ppl in total, IIRC.

Their exceedingly conservative estimate of the BAU path had humanity experience a 40-60% collapse (3.2B to 4.8B dead) by some point in the 2050s. And you don’t see that without a whole hell of a lot of secondary civilizational/technological collapse and loss of knowledge.

And they concluded that humanity existing past 2150 or 2200 was vanishingly unlikely due to polar restriction due to lethal wet bulb temperatures making the rest of the planet uninhabitable for year-round occupation, and the sheer lack of arable land in the polar region.

The problem is that we have been accelerating past 1.5℃ of warming in terms of CO2 production. We haven’t even begun to slow down, much less reverse to net zero. And since climate change has an inertia to it that is thousands of times stronger with our current change than in prior changes, there is now a non-zero possibility that - even if we go extinct - the planet itself could end up in a Venus scenario. Things are moving just far too fast for any ecosystem - much less the entire planetary ecosystem - to adapt and migrate in order to remain maximally productive in natural CO2 sequestration.