Abstract:How do we understand national climate change politics in the United States? Using a methodological innovation in network analysis, this paper analyzes discussions about the issue within the US Congress. Through this analysis, the ideological relationships among speakers providing Congressional testimony on the issue of climate change are mapped. For the first time, issue stances of actors are systematically aggregated in order to measure coalitions and consensus among political actors in American climate politics in a relational way. Our findings show how consensus formed around the economic implications of regulating greenhouse gases and the policy instrument that should do the regulating. The paper is separated into three sections. First, we review the ways scholars have looked at climate change policymaking in the United States, paying particular attention to those who have looked at the issue within the US Congress. Next, we present analysis of statements made during Congressional hearings on climate change over a four year period. Our analysis demonstrates how a polarized ideological actor space in the 109 th Congress transforms into a more consensual actor landscape in the 110 th Congress, which is significantly less guided by partisan differences. This paper concludes by discussing how these findings help us understand shifting positions within American climate politics and the implications of these findings.Keywords: Climate change, Policy, Ideology, Congress, USA, Network This research was supported by the U.S. National Science Foundation (BCS-0826892). The authors would like to thank the many students who helped code these data. Earlier versions of this paper were presented at the 2010 meeting of the American Geophysical Union, the 2011 meeting of the American Association for the Advancement of Science, the US National Oceanic and Atmospheric Administration, and the Brookings Institution.2 Introduction How do we understand the lack of a national climate policy in the United States? Under both Democratic and Republican Party leadership, the US has been unsuccessful in passing legislation that regulates the emission of greenhouse gases. Since the Kyoto Protocol entered into legal force on 16 February 2005, a number of bills have been proposed in the US Congress that would establish a federal climate change policy, but none have successfully been passed through both houses of the Congress and entered into law. 1 Social scientists have attempted to understand this lack of a federal climate change policy in many ways, focusing on various aspects of the issue (e.g. Christiansen, 2003;Fisher, 2004;Fletcher, 2009;Harris, 2000;Hovi and Skodvin, 2008;Jacques et al., 2008;Lisowski, 2002;Lutzenhiser, 2001;McCright and Dunlap, 2000;Rabe, 2004;2010;Rudel, 2001;Selin and VanDeveer, 2007;Victor, 2004; see also Gelbspan, 1997;Leggett, 1999;Ward, et al., 2008 for more popular accounts). On the one hand, there have been numerous studies that focus on climate change politics in the US to understand how national...