I see a darker possibility. Maybe we are acting.
Maybe governments and oligarchs in richer more powerful nations have concluded in secret that the situation is hopeless and that it's too late to prevent major climate change, so they are deploying totalitarianism.
When I see Trump's push to build the wall, I think maybe the wall is not for today's migrant workers and trickle of refugees. Maybe it's to wall off America from millions of refugees fleeing climate change related catastrophes and the resulting political instability. Trump's bizarre floating of a Greenland purchase? Maybe Greenland will be more valuable when the ice melts. The push to bring back lower-margin manufacturing even at the cost of an expensive and economically dangerous trade war? Maybe the people behind Trump see a global melt down (pun intended) as leading to a world with less international trade and more animosity and they want to make sure we have our own manufacturing capacity under our control. (I see Trump as a figurehead with a certain faction of the intelligence and American oligarch community behind him. He's an actor playing a part.)
When I see China's social credit system I think extreme system of social control to deal with the unrest that's likely to come. Maybe China is adding another 250GW of coal because the situation is hopeless anyway and they've calculated that it's better to accelerate their economic development so they have more resources going into this period. If the ship is sinking who cares if you put another hole in it, especially if it buys you more lifeboats.
Maybe Russia is building nuclear cruise missiles and other doomsday weapons to defend itself from China. (Others too, but China is the scariest threat in this scenario.) It like Canada has a huge territory with a small population relative to its size, but unlike Canada it does not have a superpower ally neighbor. If climate change warms northern Russia it could become prime farm land. Russia also has massive natural resources including probably a ton of undiscovered rare Earths and lithium for high technology and batteries. I could see China with its 1.3 billion people living in low-lying areas that are likely to be flooded in a worst case scenario deciding that it's going to just seize the sparsely populated half of Russia to its North. Right now China with its tens-of-millions-strong army could walk right up there and take it and there's not much Moscow could do about it.
This scenario is not "the end of the world." The richer nations actually might not fare that bad. Some could even benefit. The poorer nations and their inhabitants could suffer mightily. It could be an unprecedented humanitarian disaster.
I'm not advocating this by any stretch. Don't shoot the messenger. This is the horrible Realpolitik outcome that we'll get if we choose defection over cooperation in a game theoretic sense.
Personally if this scenario unfolded I would advocate unification of the United States and Canada (to whatever extent is politically possible) and opening our borders to anyone without a provable criminal record. Let all those migrants head all the way up to the far North, settle it, and establish farms and industry. Brain drain from places like Nazi Germany, China, the USSR, etc. created the last American century, so maybe it could happen again. In any case the economic growth we would get from this would help us afford to do things like build the great New York and Boston sea walls, the system of locks and pumps to save much of Los Angeles, and New Miami.
We're unlikely to do that though. That's not how most people think in a scarcity or threat scenario.