Australian voters’ attitudes to climate action and their social-political determinants

Sample The sample was accessed via the Life In Australia online panel [36], a national probability- based online panel comprising of Australian residents aged 18 and older. The survey was administered via telephone and online between 8 and 22 July 2019; 2,620 panel members were invited and 2,033 of these completed the survey. The sample broadly reflects the Australian population across key demographic variables, though the age profile of our sample is older than the Australian population. Of the sample, 52.7% were female and the median age was 55; the sample is therefore somewhat skewed towards older respondents as the median age of Aus- tralian adults (18 and over) is 45 [48]. Full demographic descriptive data on the sample is avail- able in Supporting information C. Data analysis Analyses of the ordinal climate opinion questions (Qs 1, 3, 4) were conducted using ordinal logistic regression (OLR) models. OLR analysis is appropriate for examining ordinal depen- dent variables with one or more independent variables [41], e.g. as used extensively by Tranter [4, 35, 40, 49–53]. We conducted univariate OLR analyses, then multivariate OLR analyses including the variables that were significant in univariate OLR analyses [following 54]. Analysis of the categorical question (Q2), regarding preferences for Australia’s future energy mix, was conducted using standard parametric (i.e. ANOVA) and nonparametric (i.e. Pearson’s chi-squared test of independence) analyses as appropriate based on data type. By

dividing the sample into sub-groups according to their response to Q2, we were able to assess for differences in demographic and voting variables within each of the Q2 response options. Following analysis of the trends and determinants of climate opinion in the context of the 2019 Australian federal election, we then constructed two basic population ageing scenarios to predict how aggregate opinion trends (related to Q1; importance of Australia reducing GHG emissions) might change in the future in line with the entry of younger voters and exit of older voters, if attitudes within each cohort remained stable. For this analysis, we used Australian Bureau of Statistics (ABS) population projections for 2017–2066 [48] from which we drew age distribution projections at the 5-year age bracket (18–22; 23–27 etc.) level. We then explored what would be the implications for the distribution of the opinion that climate action is ‘extremely important’ (Q1) based on a growing proportion of the voter base holding opinion in line with or stronger than current young people. An extended description of all analytical methods is available in Supporting information B. Results Here we present a summary of our key findings. Full results, including all statistical details, are available in Supporting information C. On the importance of Australia reducing greenhouse gas emissions Our analysis showed that over 80% of Australians in the survey profess that they view action to reduce Australia’s emissions as important, including almost 70% of conservative (Liberal,

National, Liberal-National Coalition) voters. But they are sharply divided along party lines about the importance of the issue. Three quarters (73%) of progressive voters see Australian action to reduce emissions as extremely important, while only one quarter (26%) of conserva- tive voters say it is extremely important (Fig 1). Using multivariate ordinal logistic regression (proportional odds), we identify characteris- tics that are statistically significant and meaningful in explaining the variation in stated support PLOS ONE Australian voters’ attitudes to climate action and their social-political determinants PLOS ONE | https://doi.org/10.1371/journal.pone.0248268 March 24, 2021 5 / 18