The geopolitical reality of, say, a billion people in India becoming climate refugees is likely to have worldwide implications.

India is a big and diverse place. I don't see any realistic scenario where 1 billion Indians become climate refugees.

Ok, several hundred million?

The ballistics industry should be rubbing their hands.

You're far more optimistic than I about

1) how quickly agriculture can adapt to large shifts in rain and wind patterns -- for instance, what if "more rain" includes torrential downpours with massive flooding, at unpredictable intervals? 2) how quickly the world economy can adapt to most of its major cities becoming uninhabitable (even where temps stay reasonable, sea levels won't) 3) how adaptable political systems will be to unprecedented climate-driven mass migrations, both within and between states, and in the face of collapsing states?

I don't think it'll be a gradual change at all -- more a series of rolling crises, where places spared a particular crisis either are at risk of being hit directly by the next one, or have to deal with the social, political, and economic upheaval as people die or flee areas directly impacted.

With "more rain" also comes more floods and hurricanes.

Also, gradual changes are definitely not guaranteed. Weather and chaos theory have a lot in common; Small perturbations can cause massively different outcomes. Adding 3°C to the entire planet is not a small perturbation.

Will they adapt to the raging wildfires that ~1.2C has already induced across much of the west coast? That's some adaptin'!

Wildfires on the west coast are far less common than they were 80 years ago. Humans are going to be a-ok

The northern US and Canada were barren mud and rock 12000 years ago. They'll adapt.

Oh the world will be absolutely fine, it will be we that suffer.

Like the wooly mammoths did!

Adaptation by extinction, the best one.

Except people can adapt to living in very warm areas and will adapt even more by using science. e.g. better (GMO) crop, bioreactors, solar powered desalinators, huge water pipes (why not? when we can have huge oil pipes) and so on

Gradual? On earth timescales? There have been tons of articles showing that's not happening, read one today about the great heat wave 'die off' from the last weeks. plants/animals can't adapt on near the timescale of decades from what I've read.

But maybe we can assist finding survivors, I remember reading an article a while ago about assisted coral evolution found a bunch of google scholar on it.

https://scholar.google.fr/scholar?q=climate+change+coral+evo...

That is profoundly myopic. Sure, the "planet will adapt" or whatever. But how well do you think it's gonna go when a bunch of nuclear weapon armed nations decide that the land they live on is no longer hospitable?

Nuclear weapons cause more stability, not less. Nuclear armed countries will never fight each other directly (MAD). So I presume that no nuclear war will ensue. Non-nuclear armed countries might get subsumed

"Gradual" ... Ob. xkcd:

https://xkcd.com/1732/