This is simply not going to happen - there's a preponderance of historical evidence indicating that's not how the human race behaves. Either we're going to rise

This is simply not going to happen - there's a preponderance of historical evidence indicating that's not how the human race behaves. Either we're going to rise to the challenge and save ourselves with our technology and ingenuity or we're going to flame-out. As we've gone global the stakes have risen higher - instead of a single civilization flaming-out as has happened in the past now we're facing the prospect of the entirety of civilization flaming-out. Note too that "the end of civilization" is not "the end of humanity." As you point out even in the worst-case scenario there will still be humans, but life will bear little semblance to what life is like today. I think our COVID-19 response offers a glimpse as to how climate change is going to affect us. There's denial that a problem even exists, people start dying by the hundreds of thousands, there's still a denial that a problem exists, we develop treatment therapies and vaccines (we hope!) significantly reducing the risk and life goes on. You can see global climate change has been on the same trajectory and getting the same response - largely denial with a few people rolling up their sleeves and figuring out what we can do about it. Sadly, tens of millions of people will probably die - and there will still be people denying there's a problem - and we'll (hopefully) hit on a solution. I really don't see things progressing any other way.