Like everything else, the global wealthy will survive with the wealthiest elite thriving. The global poor (mostly in the the global south) will suffer the majority of the consequences. It’ll start with crops withering for lack of water and get worse from there.

There’ll be a great sorting between those two groups as the dividing line becomes starker. It probably won’t be pretty. It definitely won’t be fair. There’s no guarantee the line won’t be drawn within a country and not just between them.

How fast does this happen? If left to just “natural” processes, loss of modern agriculture will take many decades - - just slow enough to boil the frog. But humans have a particular tendency to drive faster than we can see. So in the likely chances whatever actions we take to “mitigate” climate change backfire in our face (fingers crossed on Elon dropping a bunch of rust in the ocean and killing all the krill), I think it’s more likely that many decades is optimistic.