In this timely work, Loren R. Cass argues that international norms and normative debates provide the keys to understanding the evolution of both domestic and international responses to the threat of global climate change. Ranging from the early identification and framing of this problem in the mid 1980s through the Kyoto Protocol's entry into force in 2005, Cass focuses on two normative debates that were critical to the development of climate policy—who should bear primary responsibility for reducing global greenhouse gas emissions and what principles would guide these reductions. He examines why some nations, but not others, have met their commitments, and concludes that while many states affirmed the international norms, most did not fully translate them into domestic policy. Cass offers an index to measure the domestic salience of international norms and compare the level of salience across states and within states over time, and uses it to assess the European Union, Germany, the United Kingdom, and the United States.