> that's unlikely given that the payoff is very high for defecting.
Trade policy (e.g. through the WTO) can be designed in a way that allows countries to internalise the damage caused by greenhouse gas emissions by imposing higher tariffs on countries that do not cooperate.
But you still need everyone else to cooperate. And in a multipolar world (or at least a world with some viable political blocs outside of the US led order) that will be difficult to say the least.
Most of the world is defecting at the moment. Few are truly serious about cutting emissions dramatically.
The US is relatively high (but by no means the highest) in per capita CO2 while China is the #1 emitter in total and also per dollar GDP (last I checked). The per dollar GDP number would make China the largest emitter in terms of carbon intensity of its economic activity.
Trade policy (e.g. through the WTO) can be designed in a way that allows countries to internalise the damage caused by greenhouse gas emissions by imposing higher tariffs on countries that do not cooperate.