You also don't need an international agreement to impose tariffs on any country that emits more than a given amount of CO2 per capita, and if more than a couple of countries impose those conditions (or even just one big one like the US) then it gives others domestic cover to do something meaningful because they can argue they have to do it to avoid the tariffs. Meanwhile they can "retaliate" by imposing the same conditions and soon enough everyone is hitting their targets to avoid all the tariffs, without anyone ever having to sign up for a unified agreement.
I want it to work. I'm just not sure it is, or if humans are even capable of coordinating on the scale required to address this problem outside of some geoengineering solution.
Just like we aren't capable of operating without corruption or war because a certain group of people won't "get out of the way"