It is well established that conservatives in the United States are substantially less likely than liberals to accept that climate change is happening and is human caused and are less supportive of policies to limit climate change. However, it is likely that ideological differences in climate change beliefs, attitudes, and policy preferences are smaller when people have close friends and family members who care about climate change. Here, we use nine nationally representative survey samples (total N = 16,168) to evaluate this claim and test if perceived social consensus predicts a smaller difference in climate change beliefs between liberals and conservatives. We find that social consensus plays an important role in climate change beliefs, attitudes, and policy preferences for people across the ideological spectrum, but especially among conservatives. These findings provide important insights on how to bridge ideological divides in large social dilemmas such as climate change.

There is a strong scientific consensus that human-caused climate change is happening, and there is a significant threat to human societies and ecosystems worldwide (Cook et al., 2016). Although there is consensus among more than 97% of climate scientists that human-caused global warming is happening (Cook et al., 2016), many Americans do not believe that climate change is happening (30%) or that it is human caused (42%; Leiserowitz et al., 2018b). Political party and ideology currently have a strong influence on public opinion formation about climate change. For example, while 92% of registered Democratic voters believe climate change is real, only 51% of registered Republican voters do (Leiserowitz et al., 2018b). Including ideology, 95% of liberal Democrats believe climate change is real while only 40% of conservative Republicans do.

Does perceived social consensus—the degree to which people in one’s social group are in agreement about an issue—predict the extent to which people believe in climate change? It is well established that the judgments of other people have a powerful influence on our own thoughts and behaviors (Asch, 1955; Deutsch & Gerard, 1955; Sherif, 1936), especially when people are uncertain about what to think or how to behave (Festinger, 1954). For example, people often change their views about other groups to be consistent with the in-group consensus about a stereotype (i.e., perceived agreement about the percent of people to whom a certain trait or attribute applies, Haslam et al., 1996; Sechrist & Stangor, 2001). Research in the context of climate change has demonstrated the importance of communicating descriptive social norms (“most people do x”). For example, van der Linden (2015) finds that perceived social consensus on the issue is a key determinant of public risk perceptions of climate change. Similarly, many studies show that descriptive norms can encourage conformity in energy conservation (Allcott, 2011; Schultz, Nolan, Cialdini, Goldstein, & Griskevicius, 2007) and other sustainable behaviors, such as recycling (Cialdini, Reno, & Kallgren, 1990), towel reuse (Goldstein, Cialdini, & Griskevicius, 2008; van der Linden & Chryst, 2017), meat consumption (Sparkman & Walton, 2017), and sustainable transportation (Kormos, Gifford, & Brown, 2015).

However, what remains less clear in the context of climate change—which is characterized by large intergroup conflict in the United States—is the extent to which perceived in-group consensus is associated with belief formation and policy support. For example, some research shows that exaggerated perceptions of political polarization on climate change can lead to false norms of partisan opposition (Van Boven, Ehret, & Sherman, 2018). The perception of a positive social consensus in one’s close social network might help attenuate such intergroup pressures. In other words, are conservatives and liberals more likely to believe in climate change when (a) they perceive a social in-group consensus about either what to believe (i.e., climate change is human caused) or (b) about which pro-climate policies to support? This question is of theoretical and practical importance considering that people often misperceive what others around them believe (e.g., Jost, 2018; Mildenberger & Tingley, 2017).

The Current Research Data To address the current research questions, we draw primarily on data collected through the Climate Change in the American Mind (CCAM) project, which has conducted biannual nationally representative surveys from 2008 until the present. Data from this project are used to track key climate change beliefs over time (e.g., whether it is happening and human caused; see Leiserowitz et al., 2018a), gauge public opinion on relevant policies, and answer theory-based research questions. All samples from CCAM are nationally representative probability samples. Reports for each wave of CCAM are available online and contain demographic information for that specific sample and demonstrate that the data closely resemble U.S. population parameters (http://climatecommunication.yale.edu/publications/). As an additional robustness check, this study also includes an additional large national data set recruited from Qualtrics Panels (see sampling procedures in section “Participants”). Inclusion Criteria We included all CCAM survey waves that included a variable measuring social consensus, plus the Qualtrics survey, leading to a total of nine data sets. Including all data sets across four different social consensus variables offered the advantage of larger sample sizes as well as preliminary tests of which conceptualizations of social consensus variables are strongest in predicting global warming beliefs as a function of political ideology (see Supplementary Table 1 for information on all variables included). In addition, due to the importance of replicability and reproducibility of scientific findings (Open Science Collaboration, 2015), it is important to conduct direct and conceptual replications. Direct replications validate the phenomenon of interest and conceptual replications validate the underlying theoretical concept (Earp & Trafimow, 2015). The current data sets allow for both.

Method Participants The total number of respondents was N = 16,168. Data for eight of the nine surveys used in this article were collected via biannual waves of nationally representative surveys on climate change (n = 9,867). The number of respondents for each variable is available in Supplementary Table 1. Respondents were American adults aged 18 and older and recruited from GfK’s Knowledge Panel using probability sampling. Potential respondents were recruited using either random-digit dialing or address-based sampling techniques that cover nearly all resident phone numbers and addresses in the United States. Respondents who were recruited but did not have Internet access were loaned computers with access to the Internet, enabling their participation. We used an additional national data set of American adults (18+ years old), which was collected from Qualtrics panels (Qualtrics LLC, Provo, UT) in 2015 (n = 6,301). The sample used quotas to reflect the United States population for gender, age, region, education, and political party. All surveys and informed consent to participate in each survey were self-administered online by the respondent. All studies were approved by the Yale University Institutional Review Board and all procedures were carried out in accordance with their regulations. Materials and Procedure The data were drawn from eight waves of nationally representative surveys and one wave from a national survey (total N = 16,168) conducted between 2008 and 2017. In each survey, participants answered questions regarding global warming, including beliefs (e.g., do you think that global warming is happening?), policy preferences (e.g., how much do you support or oppose the following policies; “regulate carbon dioxide as a pollutant”), norm perceptions, political party, and ideology (1 = Very liberal, 5 = Very conservative). A full description of all questions used in this study is listed in Supplementary Table 1. Participants were asked one of four different questions about their perception of the social consensus on climate change within their group of friends and family, depending on the wave of survey. For example, “. . . what percentage of people who are important to you (friends, family, etc.) believe that human-caused global warming is happening?” (0%-100%) and “How important is it to your family and friends that you take action to reduce global warming?” (1 = Not at all important, 5 = Extremely important). Several dependent variables measured respondents’ belief that climate change is happening and human caused, their level of worry about climate change, and support for climate policies (see Supplementary Table 1). All variables were standardized and then combined into a single data set (see details below).

Discussion Together, these results suggest an important role of perceived social consensus in climate change beliefs and support for mitigation policies. Perceived social consensus is associated with a higher percentage of people who believe climate change is real and human caused. The same pattern emerges for worry and climate policy support. Perceived social consensus remains a strong predictor even when controlling participant ideology as well as demographic variables. Importantly, perceived social consensus appears to be particularly important for predicting the views of conservatives. This is consistent with prior research that finds conservatives place greater value on in-group loyalty, conformity, and desire to identify with others (Caprara et al., 2006; Jost, 2017a; Jost et al., 2018; Stern et al., 2014). In particular, these findings suggest the importance of norm-perception as a means for social change, as (mis)perceptions of group norms are often easier to change than deep-seated private beliefs and worldviews (Tankard & Paluck, 2017; van der Linden et al., 2018). In addition, we observed the same pattern of results when examining political party. That is, for people who perceived low social consensus, Republicans had significantly lower pro-climate beliefs than did Democrats, but this difference was substantially smaller for people who perceived high social consensus. These findings, together with those on ideology, have implications for how to use social identity as a messaging strategy. For example, while there is substantial overlap between those who are conservative and those who identify with the Republican party, it is likely that some people more strongly identify with one of the two groups (i.e., conservatives vs. Republicans). Thus, it would be fruitful for future research to investigate the extent to which appeals to people’s conservative versus Republican identity are more effective in communicating about climate change. We also used random effects meta-analyses to explore the extent to which some measures of social consensus were stronger than others in predicting weaker ideological biases. First, results from social consensus questions that asked about friends and family were clearly stronger than the question that only included friends. Second, and perhaps more interesting, results consistently showed that ideological biases became weakest (i.e., interaction was strongest) when respondents perceived that their friends and family thought it was important for the respondent to take action on global warming. These findings suggest that this conceptualization of social consensus might be most intuitively salient to participants (e.g., Cialdini et al., 1990). That is, it might be easier to bring to mind what one’s family and friends find important, as opposed to what they are doing or what percentage of one’s social group believe human-caused global warming is happening. While this explanation is plausible and deserves attention in future research, the available data in this study make it difficult to draw firm conclusions on which way of measuring social consensus is most informative. For example, the strongest effects were observed in the most recent survey waves, thus it is difficult to know whether the stronger social consensus results were due to data being closer to the present or because this conceptualization of social consensus is most informative. Furthermore, the confounding effects of survey wave and social consensus questions make it difficult to interpret the effect of survey wave. We observed that the ideology × perceived social consensus interaction got stronger as survey wave got closer to the present day. This makes sense in light of the increase in ideological and partisan polarization in the United States (Pew Research Center, 2017). That is, as people become more aligned with their ideological and partisan in-groups, social consensus can become even more predictive of weaker ideological biases on climate change when biases are larger to begin with. However, we view this finding as preliminary because of the reasons described above as well as the relatively small effect of survey wave. It is important to note the limitations of this study. First, these data cannot demonstrate causality. As the data are not experimental, we take the next best approach and attempt to rule out plausible alternative explanations. The primary alternative explanation for these data is that conservatives who believe climate change is happening, human caused, worry about it, and support mitigation policy are predisposed to believe that the rest of their own social group feels the same way, or perhaps choose friends that feel the same way. To compare the support for this Social Projection hypothesis and the Social Influence hypothesis (i.e., the primary hypothesis in this article), we conducted two random effects meta-analyses to determine which models better explained the variability in the data. Results consistently showed more support for the Social Influence hypothesis and showed that the meta-analytic effect was significantly stronger than for the Social Projection hypothesis. In addition, experimental findings demonstrate that manipulating perceived scientific consensus can shift private beliefs and support for action (van der Linden, Leiserowitz, Feinberg, & Maibach, 2015) and that climate change messages from in-group Republicans are seen as more persuasive (Benegal & Scruggs, 2018), which increases confidence in the Social Influence explanation. Importantly, however, the majority of the effects were significant for the Social Projection models. Thus, it is plausible that causality among these variables is bidirectional, albeit at different magnitudes. It would be fruitful for future research to investigate both causal pathways in experimental or longitudinal research. Importantly, although establishing causality has important practical implications for applied research, the contribution of the current findings is not entirely contingent on demonstrating causality. For example, we used our most recent data, weighted to census parameters, to show that more than one third of conservatives perceived at least moderately high social consensus about climate change among their friends and family. From a strategic standpoint, this is important for identifying conservatives that are likely to be pro-climate, which is a crucial step toward encouraging them to take action. An important consideration in interpreting the current findings is the extent to which the results observed here are driven by ideological differences in conformity and in-group loyalty. That is, the results may be explained by the larger opportunity for conservatives’ beliefs to vary as a function of social consensus rather than fundamental differences in ideological values. Although the current data cannot definitively answer this question, a large literature shows that—compared to liberals—conservatives have a stronger motivation to affiliate with in-group members. This ideological asymmetry is evident in basic differences in life values across individuals from many different countries (Piurko et al., 2011), in moral judgments (Graham et al., 2009), and even in consumer behavior (Fernandes & Mandel, 2014; for a review see Jost, 2017b). Thus, the current findings are consistent with a large body of previous research documenting ideological asymmetries. An unanswered question that remains in this line of research is what level of agreement is perceived as a “persuasive” consensus. That is, it remains unclear whether a majority of one’s friends and family members (e.g., 51%) qualifies as a majority consensus or whether people only perceive high social consensus when it is extremely high like the consensus on climate change observed among climate scientists (i.e., 97%). The psychological “threshold” for what level of consensus is regarded as persuasive likely depends on a person’s experience and motivations. For example, for someone who is motivated to reject climate science, it may take extremely high consensus to move their beliefs. Whereas for someone who is simply disengaged from the issue of climate change, it may only take a slim majority to move their beliefs. Future research should address these open questions and determine the extent to which social context and individual differences moderate the effects of different levels of social consensus. Another avenue by which to extend the current research is by measuring the political identity of people’s close friends and family. Those data were not available in this study, but likely would contribute to a greater understanding of the boundaries of social consensus effects. Social consensus should be more influential when, for example, conservatives are part of a social network of pro-climate conservatives than when they are part of a network of pro-climate liberals. The results from this study have important practical implications. For example, from a social identity perspective, most conservatives likely affiliate and identify more strongly with their own friends and family than conservatives as a broad category (i.e., outside their own social group) because people in their immediate social network are more important to their daily lives and identity. Thus, if their own friends and family care about climate change, they are more likely to care as well. These results align with the suggestion that communicators could try to engage people based on non-political identities (Pearson, Schuldt, Romero-Canyas, 2016), such as hunting and fishing, or parenting and grandparenting, which may enable more constructive conversations about climate change than partisan discourse. The research reported here underscores the importance of encouraging people, especially conservatives, to talk about climate change and their support for climate policies. Most Americans say the issue of global warming is personally important, yet rarely hear about it from their friends and families (Maibach et al., 2016). This dynamic can lead to lower climate policy support simply because people may mistakenly believe that other important people in their lives do not care about climate change. Thus, our results highlight the importance of breaking the silence on climate change (Maibach et al., 2016).

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This research was supported by the 11th Hour Project, the Energy Foundation, the Grantham Foundation for the Protection of the Environment, the MacArthur Foundation, and the VK Rasmussen Foundation. Supplemental Material

Supplemental material for this article is available online. ORCID iDs

Matthew H. Goldberg https://orcid.org/0000-0003-1267-7839 Sander van der Linden https://orcid.org/0000-0002-0269-1744