Over at UN Dispatch, Mark Leon Goldberg explains why the meeting mattered. He also says that, "in a body composed of 192 member states, it is very difficult--practically speaking--for a tiny group of nations to hold out against the will of the rest. It is a basic negotiating tenet here at the UN that countries try to avoid being 'isolated.'...No country feels comfortable being a 'spoiler' by positioning itself against the will of an overwhelming majority of UN member states."
It's not clear to me that that's true. Rather, it seems that if George W. Bush stays in office, or is succeeded by Fred Thompson, we won't address global warming, while if he's replaced by, say, Christopher Dodd, we will. One thing the Bush administration has shown is that these traditional norms are rather toothless, and if an American leader is willing to be widely reviled, he can basically tell the world community to go fuck itself. There's no real method of enforcement here, The UN offers a powerful platform through which the world's other inhabitants can seek to pressure the US, but our sensitivity to their opinions appears to depend on how much our president actually cares what they think. If the answer is that he doesn't, they don't really have another option.
That said, it was interesting to see the unanimity of the rest of the world, and particularly Sarkozy, who was speaking on behalf of the entire EU. Given that it's unlikely Republicans will remain in power forever, we really are likely to some action on global warming, and the UN is effectively laying the groundwork to be the institution in which that action takes place -- an outcome that wasn't clear even a few years ago, but which could do much to underscore the relevance of the UN and help define its mission in the new millennia.