@seachanger The hard part of "capitalist planetary sovereignty" is the "planetary" bit. Basically nation-states would be agreeing to give up some sovereignty to a UN-like structure. It's not a given that they will succeed at that, look at the useless COP process.
2 other alternatives the author calls "Climate Mao" & "Climate Bohemoth" which are *not great* either. There is a fourth which so far the author is being coy about (I'm less than halfway through).