It is only a matter of time before the first state imposes an import tariff on goods from countries that are not taking action on climate change. On one level, that is fair enough. If domestic manufacturers are paying for their CO2 emissions through a cap-and-trade scheme or carbon tax, they have some legitimate objections against imports from foreign competitors who are not doing so. That said, the actual experience with the first such tariffs is likely to be a huge legal and political mess.
Membership in the World Trade Organization – something common to most big emitters – carries a number of obligations of varying levels of obscurity and enforcement. You can bet that countries that have such tariffs applied to them will protest such treatment aggressively. It would also be fair to bet that the winner of the contest will be determined on the basis of economic power, rather than the rightness or wrongness of arguments. It is even possible that the resulting compromise will be worse from a greenhouse gas mitigation standpoint than if the argument had never begun.
That said, it is at least logically possible for the global trading system to help in the development of an effective global regime of rules, norms, and decision-making procedures around the issue of climate change. It obviously won’t have an effect on countries that don’t do a lot of trading, but they are probably not the most essential ones to get on board anyhow. What will matter most is which of the two biggest economic blocs will triumph: the United States, still in denial about what solving climate change will require, or Europe, where at least some leading states are starting to get serious.