Annals of the Association of American Geographers, 91(2), 2001, p. 307–337 © 2001 by Association of American Geographers Published by Blackwell Publishers, 350 Main Street, Malden, MA 02148, and 108 Cowley Road, Oxford, OX4 1JF, UK. The Construction of Global Warming and the Politics of Science David Demeritt Department of Geography, King’s College London Having outlined a theory of heterogeneous social construction, this article describes the scientific construction of climate change as a global-scale environmental problem caused by the universal physical properties of greenhouse gases. Critics have noted that this reductionist formulation serves a variety of political purposes, but instrumental and interest-based critiques of the use of scientific knowledge tend to ignore the ways in which a politics gets built into science at the upstream end. By retracing the history of climate modeling and of several scientific controversies, I unmask the tacit social and epistemic commitments implied by its specific practices. The specific scientific framing of global climate change has reinforced and been reinforced by the technocratic inclinations of global climate man- agement. The social organization of climate change science and its articulation with the political process raise im- portant questions about trust, uncertainty, and expertise. The article concludes with a discussion of the political brittleness of this dominant science-led and global-scale formulation of the climate change problem and the need for a more reflexive politics of climate change and of scientific knowledge based on active trust. Key Words: climate change, social constructionism, social studies of science. n little more than a decade, global warming has been transformed from an obscure technical concern into a subject of widespread public anxiety and interna- tional regulatory interest. Only a dozen years separate the World Meteorological Organization’s 1985 Villach conference, at which years of previous scientific research and technical debate crystallized into one of the first widely publicized warnings about an anthropogenically enhanced greenhouse effect due to rising concentrations of carbon dioxide (CO 2 ) and other radiatively sensitive greenhouse gases (GHGs), from the recent Kyoto Proto- col to United Nations Framework Convention on Climate Change (UNFCCC), at which politicians hammered out a package of legally binding targets for reducing the GHG emissions of industrialized countries. The speed with which scientific knowledge of climate change has been translated into an international diplomatic consensus is remarkable, if not unprecedented. It is testimony to the authority of science to provide legitimacy for political action. However, science cannot be given all the credit for spurring the rapid political response to climate change. The 1988 heat wave and drought in North America were arguably as influential in fostering public concern as any of the more formal scientific advice, such as NASA sci- entist James Hansen’s infamous 1988 declaration to Congress that he was “99 percent sure” that global warm- ing was already happening (quoted in Ungar 1992, 491– 92; cf. Mazur and Lee 1993). The relationships among the diverse expert and lay understandings of climate change are complex, as are their connections to climate change politics and policy-formation (Jasanoff and Wynne 1998). A variety of powerful political interests served as mid- wives to the birth in the mid- to late 1980s of climate change as a pressing global environmental problem. Since the leading cause of increasing atmospheric GHG con- centrations is fossil fuel consumption, which is rapidly increasing worldwide, the politics of climate change are closely intertwined with the politics of energy (Boehmer- Christiansen 1990; Levy and Egan 1998; Newell and Paterson 1998; Rowlands 2000) and the politics of devel- opment (Rajan 1997; Grubb, Vrolijk, and Brack 1999; Sachs 1999). Political analysis has focused primarily on the power- ful interests competing to set climate change policy. Po- litical scientists and geographers have charted the fate of local climate change mitigation and energy conservation initiatives (Hinchliffe 1996; Lambright, Changnon, and Harvey 1996; Bulkeley 1997; Collier 1997) and intra- state struggles to fashion coherent national energy and environmental policy responses to global warming (Hatch 1993; O’Riordan and Jäger 1996; Sewell 1996; Pleune 1997; Rajan 1997). Students of international re- lations have studied the geopolitics of negotiating inter- national environmental agreements on climate change (Hecht and Tirpak 1995; Rowlands 1995; Paterson 1996; Yearley 1996; Grubb, Vrolijk, and Brack 1999). This I