Without active collaboration between the United States and China, not only will the odds for successful negotiations in Copenhagen this December to secure a successor treaty to the Kyoto Protocol be diminished, but it will be unlikely that any meaningful remedy will be found in time to arrest rising global temperatures. Yet talks between the US and China on climate change currently present two contrasting scenarios, one hopeful, the other discouraging.

In the first scenario, the two countries' senior delegations remain deadlocked, with their polarised stances frozen in place. Moreover, the failure of developed countries - particularly, the US - to take responsibility for their historical emissions of greenhouse gases continues, representing a major sticking point because these...