The question of commitments lies at the heart of the climate change debate. Ever since climate change first emerged as a political issue in the late 1980s, attention has focused on quantified ‘targets and timetables’ as the principal type of commitment-the model used with great success in the 1987 Montreal Ozone Protocol. Although legally binding targets and timetables for greenhouse gas mitigation could not be agreed in the 1992 UN Framework Convention on Climate Change (due primarily to opposition by the United States), they became the centerpiece of the Kyoto Protocol-and the lightning rod for its opponents.