David Wallace-Wells: "In their retrospective analysis, they found that, despite much consternation about designing climate policy to prevent countries from 'cheating,' there was basically no evidence of any country ever pulling back from mitigation efforts to take a free ride on the good-faith efforts of others. There was, in other words, no collective-action problem on climate after all. For a generation, the argument for climate action was made on a moral basis. That case has only grown stronger. And now there are other powerful, more mercenary arguments to offer."