If it gets that bad computers in a thousand years may be out of reach. We have consumed all of the easily accessible fossil fuels so it will be much harder or impossible to bootstrap a new civilisation. This is plausibly the last great civilisation.
Yes. Which is why I believe that keeping our civilization in the stable state should be the most important policy goal. A point explored here, earlier today: https://news.ycombinator.com/item?id=20447671.
It also bears reminding that climate change is not a threat to the planet or to humans as a species. Both will be fine. But it's an existential threat to technological civilization.
Or, in other words: if you want your children and grandchildren to have even a semblance of quality of life an average person has today, climate change must be stopped now.
The planet will be fine if you consider events like the Permian mass extinction to be "fine." If you doubt we could push things that far, see this recent MIT study:
I think some geographically isolated village may survive even a nuclear war, and as long as a village survives, humanity stands a chance.
I don't rule out the possibility of us making ourselves extinct, but I think it's a low-probability outcome. Also, if only few humans remained, I'd still call it game over.
WRT. the study, it's scary stuff. If that threshold truly exists, we can kiss humanity goodbye.
