In your leader on the upcoming Copenhagen summit on climate change, you contrast carbon-dioxide emission targets that are internationally binding with targets that are binding only nationally, but have the force of domestic law (“Avoiding a Crash at Copenhagen,” September 26, 2009). The Kyoto protocol relies on the former, while the alternative approach, recently proposed by Australia, would rely on the latter. Most important, such an approach would be much more palatable to American legislators, who eschew international treaties of any kind. As witnessed by the fact that global carbon-dioxide emissions have grown by twenty-five percent since 1997, when the Kyoto protocol was adopted, the international approach is not working very well, if at all. As you put it, Kyoto has no teeth. A variant of the Australian proposal would be to engage regional clubs, such as the European Union or the Association of Southeast Asian Nations, in the promotion and supervision of national legislation of member states concerning emission targets. While providing regional perspectives, so vital in connection with climate change, this would give such clubs more teeth, as well. Collaboration and competition between regional clubs would eventually lead to an agreement on emission targets that would be both global and binding.