I've only ever heard the claim that climate change is civilization ending as a strawman from so-called climate skeptics. Also occasionally from those that are poorly informed, but they also tend to believe things like GMOs being the end of agriculture, and have basically zero impact on society due to lack of influence and small number of people. Nordhous' extreme situations may have been possible back in the 1990s with zero action and without the advent of solar, wind, and storage that have been created since then, but his statements are kind of wacky.

We've known for almost a decade now that the RCP8.5 scenarios are no longer on the table, and even that worst case scenario wasn't civilization ending.

I read Bill Gates' note as not an evolution on his view at all, it seems 100% consistent with everything he has worked for, but rather trying to place climate change in a more humanity-focused context for evaluating tradeoffs of where to put money. That's very important for governments and for wealthy philanthropists like him, and for the COP 3 audience he's talking to.

>I've only ever heard the claim that climate change is civilization ending as a strawman from so-called climate skeptics

Did you see what happened in Europe with a rather small mass migration 10/15 years ago due to Arab Spring ? People have short memories.

Can you imagine what will happen when 100 of thousands start migrating north when they can no longer feed themselves and maybe even work outside ? Italy was close to sinking boats coming across the the sea. Other countries in the EU started building walls. And even Germany took a slight right turn. Once these large migrations start, I expect bombs will be dropped. Same applies to North America.

"I've only ever heard the claim that climate change is civilization ending as a strawman from so-called climate skeptics. "

And yet, sentence from current top comment: " We're in a mass extinction."