I agree with your assessment on the difficulty of the problem. Where I differ is my (somewhat optimistic, admittedly) view that an existential climate crisis is

I agree with your assessment on the difficulty of the problem. Where I differ is my (somewhat optimistic, admittedly) view that an existential climate crisis is the kind of exogenous shock needed to force humanity to cooperate against a "common enemy" so to speak. We've had models before with the CFC / Montreal Treaty, and on a national scale with WW2, and the Sputnik / Apollo missions. There are very few problems humanity cannot solve by coordinated effort. The trick is to force that coordination, and I don't see that happening in the near future.