Climate change belief systems across political groups in the United States

the density of each group was compared with that of Republicans. It is worth noting that the choice of a reference group does not influence or alter the outcomes of the analysis. While the group with no political affiliation generally had less dense belief systems compared to Republi- cans (b = -.02, p <. 001, 95% CI [-.03, -.01]), the density of the no affiliation group increased significantly over time relative to Republicans (b = .001, p < .01, 95% CI [.001,.002]). The results of the simple slope analysis further reveals a significant increase in the density of the no affiliation group (estimated slope b = .002, 95% CI [.001,.002]), whereas the density of groups with political affiliations remained relatively stable over time (Republicans: b = .0002, 95% CI [-.0004,.001]; Democrats: b = .0003, 95% CI [-.0003,.001]; Independent/Other: b = .0002, 95% CI [-.0004,.001]). We compared the overall structure of belief systems to evaluate the extent to which political groups develop homogeneous or heterogeneous belief systems both within and between groups. Fig 4 illustrates the results. First, intra-group comparisons of belief systems across mul- tiple time points revealed that the politically unaffiliated developed more heterogeneous belief systems within the group (M = .49, SD = .14) compared to other groups, including Democrats (M = .27, SD = .03; difference (diff, hereafter) = .21, p < .001), Republicans (M = .27, SD = .04, diff = .21, p < .001), and Independents (M = .39, SD = .04, diff = .09, p < .001). Republicans

developed relatively more homogenous belief systems within their group than Independents (diff = .12, p < .001). In addition, Democrats also developed more homogenous belief systems than did Independents (diff = .12, p < .001). There was no significant difference in GDD score between Republicans and Democrats, indicating that the level of intra-homogeneity was simi- lar between the two groups (diff = .001, p = 1.00). We also conducted inter-group comparisons to compare the overall structure of belief sys- tems between different political groups. The politically unaffiliated had more heterogeneous belief systems compared to other political groups. Specifically, the unaffiliated shared the least Fig 3. Changes in belief system density across political affiliations for the past decade. https://doi.org/10.1371/journal.pone.0300048.g003 PLOS ONE Climate change belief system PLOS ONE | https://doi.org/10.1371/journal.pone.0300048 March 20, 2024 10 / 16