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Scientists’ views and positions on global warming and climate change: A content analysis of congressional testimonies

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Among many potential causes for policymakers’ contention over whether there is a largely unified scientific agreement on global warming and climate change (GWCC), one possible factor, according to the information deficit theory, is that the scientists who testified in congressional hearings might be substantially divided in their views and positions associated with GWCC. To clarify this, we perform content analysis of 1350 testimonies from congressional GWCC hearings over a period of 39 years from 1969 to 2007 and use the data derived from this content analysis to provide an overview of scientist witnesses’ stances on GWCC. The key findings include: (1) among the scientists’ testimonies with an expressed view on whether GWCC is real, a vast majority (86 %) indicates that it is happening; (2) among the scientists’ testimonies with an identified stance on whether GWCC is anthropogenic, a great majority of them (78 %) indicates that GWCC is caused, at least to some degree, by human activity; (3) even under Republican controlled congresses, there is still a supermajority (75 %) - among the scientists’ testimonies with an expressed position on GWCC existence or GWCC cause - that believes that GWCC is real and that GWCC is anthropogenic; (4) most scientists’ testimonies (95 %) endorse pro-action policy to combat GWCC; and (5) the percentages of scientists’ views and positions are consistent across different types of scientist testimony groups. Our findings suggest that the scientific information transmitted to Congress is not substantially different from the general agreement in the climate science community.

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  1. The LexisNexis searchable database of congressional records ( was accessed and all the hearing and testimony data were collected in the spring of 2008 for a larger research project on national climate change policy processes.

  2. We used the wildcard key term ‘greenhouse gas*’ in order to obtain any record containing “greenhouse gas” or “greenhouse gases.”

  3. Over twenty different congressional committees in both the House and the Senate held GWCC-related hearings during the 39-year study period. These committees covered various jurisdiction areas and a wide range of issue interests, including agriculture, natural resources, science and technology, commerce, small business, energy, transportation, environment, public works, foreign affairs and relations, governmental affairs, budget, appropriations, etc.

  4. After training, the coders were given 40 testimony records (randomly sampled from all 1350 testimonies) to code. We performed an inter-coder reliability check of these 40 coded testimonies and found over 90 % agreement between the coders (exceeding the 0.80-or-greater standard for reliable concordance in most content analysis practices). With this encouraging result, we had the coders continue with the remaining testimonies.

  5. Witness’s stances across the three questions on GWCC existence, human cause, and GWCC policy, may vary. For example, a witness may agree on one question (i.e. GWCC existence) but disagree on another (e.g. GWCC human cause). In our coding and data analysis, witness’s stance on each of these three questions was treated separately.

  6. The focus on reported profession and affiliation is a limiting condition of our measurement approach. Witnesses might have multiple affiliations, different past professions, etc. The data that were readily available did not include these potential alternative affiliations and professions. We believe this source of measurement error is rare (in most cases, the reported profession and affiliation are primary and representative of the witnesses’ identities) and unlikely to bias the results.

  7. Data for partisan composition of Congress were drawn from official US House and Senate websites. See, and

  8. While the terms “mitigation” and “adaptation” were not always used during testimony, specific policy proposals can be directly linked to these strategies. Policies that would reduce the amount of greenhouse gas emissions, with the goal of limiting the impact of GWCC at the source of the pollution, are mitigation strategies; policies designed to adapt to the repercussions of GWCC, such as the construction of sea walls in preparation for rising sea levels, are adaptation strategies. While these represent different strategies for addressing GWCC, they were coded as a single category, ‘Pro-action,’ to identify those who testified before Congress and made policy recommendations that would address GWCC.

  9. While this study focused on committee hearings specifically on GWCC, it is possible that contrary positions on GWCC might be more commonly found during hearings that were excluded from this examination because they were not specifically on GWCC. This possibility indicates an additional avenue for future research.


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The material used in this study is based upon research conducted by the Institute for Science, Technology and Public Policy in the George Bush School of Government and Public Service at Texas A&M University and supported under Award No. award NA04OAR4600172 by the National Oceanic and Atmospheric Administration (NOAA), U.S. Department of Commerce. The statements, findings, conclusions, and recommendations are those of the authors and do not necessarily reflect the views of the National Oceanic and Atmospheric Administration or the Department of Commerce. We would like to thank the following people for their assistance: Carol Goldsmith, Ivy Cui, Jessie Wang, and Charles Lindsey. We would also like to thank the anonymous reviewers for their insightful comments and suggestions.

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Correspondence to Xinsheng Liu.

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Liu, X., Vedlitz, A., Stoutenborough, J.W. et al. Scientists’ views and positions on global warming and climate change: A content analysis of congressional testimonies. Climatic Change 131, 487–503 (2015).

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