[scarmig]

I don't even think it's a risk to culture and knowledge, speaking as someone who ranks climate change as our highest long-term priority. Unmitigated it will cause millions of excess deaths and have a substantial drag effect on GDP growth, but it's not going to cause us to revert back to paleolithic or even 19th century living standards. Humanity will just be substantially better off in a century if we deal with it now instead of shrugging our shoulders.