Environmental policy: Regional commitment to reducing emissions.

The non-participation of the United States in the recently ratified Kyoto Protocol is a matter for global concern because it is estimated that the country produces 24% of all greenhouse-gas emissions worldwide. Here we analyse the commitment of individual states and municipalities to addressing this problem and find that, despite the federal policy, between 24 and 35% of the US population are currently (or soon will be) engaged in policies directed towards significantly reducing anthropogenic climate change. The importance of this sub-national effort, which we estimate corresponds to 27–49% of the gross domestic product, will depend — like the targets adopted in Kyoto — on the real reductions achieved in greenhouse-gas emissions. [ABSTRACT FROM AUTHOR]