Elke U. Weber Paul C. Stern Columbia University National Research Council
This article considers scientiﬁc and public understandings of climate change and addresses the following question: Why is it that while scientiﬁc evidence has accumulated to document global climate change and scientiﬁc opinion has solidiﬁed about its existence and causes, U.S. public opinion has not and has instead become more polarized? Our review supports a constructivist account of human judgment. Public understanding is affected by the inherent difﬁculty of understanding climate change, the mismatch between people’s usual modes of understanding and the task, and, particularly in the United States, a continuing societal struggle to shape the frames and mental models people use to understand the phenomena. We conclude by discussing ways in which psychology can help to improve public understanding of climate change and link a better understanding to action. Keywords: risk perception, climate change perception, mental models, expert–novice differences limate change” is the name given to a set of physical phenomena and of a public policy issue, sometimes also referred to as “global warming,” even though climate change involves much more than warming. This article describes the development of scientiﬁc and public understanding1 of climate change in the United States, focusing especially on the riddle of noncorrespondence: Why, as scientiﬁc understanding of climate change has solidiﬁed, has U.S. public understanding not, and instead become more polarized? It also considers the implications of this situation for the future of public understanding and action. “Climate change” emerged as a public policy issue with improved scientiﬁc understanding of the phenomena involved, resulting in concerns. In 1959 an observatory on Mauna Loa, Hawaii, recorded a mean level of atmospheric carbon dioxide (CO2) of 315 parts per million, well above the highest concentration—no more than 300 parts per million—revealed in the 420,000year-old ice-core record. By the end of the 1970s, CO2 levels had reached 335 parts per million (Hecht & Tirpak, 1995). The National Research Council, asked to investigate the subject, suggested, “If carbon dioxide continues to increase, the study group ﬁnds no reason to doubt that climate changes will result and no reason to believe that these changes will be negligible” (Climate “ May–June 2011 ● American Psychologist © 2011 American Psychological Association 0003-066X/11/$12.00 Vol. 66, No. 4, 315–328 DOI: 10.1037/a0023253
Research Board, 1979, p. vii). In 1987, Congress passed the Global Climate Protection Act and directed the Environmental Protection Agency to propose to Congress a coordinated national policy on global climate change and the Secretary of State to coordinate diplomatic efforts to combat global warming. The Global Change Research Act of 1990 established a major national research program to study global environmental change, including climate change, its causes, its effects, and possible responses.
Scientific Understanding of Climate Change
Scientists’ understanding of climate change has evolved over more than 150 years through a process of collective learning that relies on the accumulation of observational data; the formation, testing, and reﬁnement of hypotheses; the construction of theories and models to synthesize knowledge; and the empirical testing of hypotheses, theories, and models (National Research Council, 2010a). The understanding of the scientiﬁc community is captured in carefully peer-reviewed collective assessments of the evidence, including those of the Intergovernmental Panel on Climate Change (IPCC). The most important recent assessments, particularly from a U.S. standpoint, are those of the U.S. Global Change Research Program (Karl, Melillo, & Peterson, 2009) and the National Research Council (2010a). These assessments support the...