Knowledge as a driver of public perceptions about climate change reassessed

Transcription

1 1. Method and measures 1.1 Sample Knowledge as a driver of public perceptions about climate change reassessed In the cross-country study, the age of the participants ranged between 20 and 79 years, with approximately 20% of the participants (n = 80) belonging to each age group among the surveyed countries. Participants educational level was generally higher than the average, with approximately 30% of respondents having received university degrees in Canada, Germany, Switzerland, and the United Kingdom. Participants from China and the United States possessing university degrees accounted for 57% and 37% of the samples, respectively (Table S1). In the additional Swiss study, the sample was similar with the cross-country study. About 20% of the participants were in each age group. 8% (n = 26) of the respondents fell into the low education category and 22% (n = 74) people had a university degree ( high education ). Table S1. Demographic characteristics of participants in the six different countries: Frequencies and percentages are shown (gender and age were quota variables). Canada (N = 426) China (N = 420) Germany (N = 421) Switzerland (N = 404) UK (N = 401) US (N = 423) n % n % n % n % n % n % Gender male % % % % % % female % % % % % % Age % 86 21% 83 20% 77 19% 69 17% 63 15% % 82 20% 77 18% 75 19% 74 19% 75 18% % 79 19% 86 20% 78 19% 79 20% 93 22% % 91 22% 85 20% 87 22% 85 21% 91 22% % 82 20% 90 21% 87 22% 94 23% % Education # low 17 4% 24 6% % 34 8% 15 4% 19 5% middle % % % % % % high % % % % % % Notes. Totals of percentages are not 100 for every demographic characteristic and country because of rounding and missing responses. # Low education indicates the highest degree participants received is below high school (including no education, primary school, secondary school, middle school, and some high school in different countries). Middle education indicates the participants have received the degree of high school or higher but not yet a university degree (including high school, vocational school, college, and some university). High education indicates the participants have received a university degree or higher (including Bachelor, Master, and PhD). NATURE CLIMATE CHANGE 1

2 1.2 Knowledge scale Our objective knowledge scale consisted of 12 items used in previous studies 1,2 and had three subscales representing three different forms of knowledge: knowledge about physical characteristics assessed fundamental knowledge about the physics underlying climate change, knowledge about the causes of climate change measured the reasons that climate change is happening, and knowledge about the consequences of climate change included items about the different natural hazards and environmental effects of climate change. Other authors discussed the relevance of procedural or action-related knowledge to explain ecological behaviors 3. Because procedural knowledge was not expected to explain people s perception of environmental issues 1,2, this was not investigated in the current research. Respondents answered each item with true, false or don t know. The latter response option was provided to avoid guesses from the participants. The wordings of the knowledge items were carefully selected in order to avoid indicating the correctness of the statements. Respondents answers on the knowledge scale were first reversed for knowledge items with incorrect statements. Hence, the results indicated whether the answers were correct, wrong, or whether the respondent did not know the answer. Don t know answers were recoded as wrong answers thereby allowing for an analysis of binary data (1 = correct ; 0 = wrong and don t know ). In the additional survey in Switzerland, we also included a self-assessed knowledge measure. Participants were asked to rate their level of knowledge about climate change on a 6-point scale ranging between very low knowledge and very high knowledge. 1.3 Value orientations and cultural worldviews We adopted three general value orientations in the present paper from De Groot and Steg 4 : 1) egoistic values reveal people s desire for personal interests and advancements; 2) altruistic values explore to what extent do participants care about the welfare of others; and 3) biospheric values indicate whether people concern about the environment and about supporting living organisms. The value items were assessed on a nine-point response scales, 2 NATURE CLIMATE CHANGE

3 ranging from -1 ( opposed to my values ), 0 ( not important ) to 7 ( extremely important ). The reliability coefficients suggested three reliable scales (Cronbach s αs 0.84, Table S2). Table S2. Value orientations: The items, their means, standard deviations, corrected itemtotal correlations, as well as internal reliabilities, means and standard deviations of the scales of the cross-country study. Items per scale M SD Corrected itemtotal correlation Egoism (Cronbach s α = 0.84, M = 2.71, SD = 1.81) Social power: control over others, dominance Wealth: material possessions, money Authority: the right to lead or command Influence: having an impact on people and events Altruism (Cronbach s α = 0.90, M = 5.63, SD = 1.41) Equality: equal opportunity for all A world at peace: free of war and conflict Social justice: correcting injustice, care for the weak. Helpful: working for the welfare of others Biospherism (Cronbach s α = 0.95, M = 5.62, SD = 1.48) Preventing pollution: protecting natural resources Respecting the earth: harmony with other species Unity with nature: fitting into nature Protecting the environment: preserving nature In the additional study in Switzerland, we also measured participants cultural worldviews by adopting the 12-item scale from the study of Kahan et al. 5 (egoismcommunitarianism, hierarchy-egalitarianism) and slightly changed the items to better fit the Swiss society 2. All items were assessed on six-point Likert scales ranging from 1 ( strongly disagree ) to 6 ( strongly agree ). The internal consistency of these two subscales was fairly good, with Cronbach s α = 0.77, N = 6 for the individualism dimension and Cronbach s α = 0.68, N = 6 for the hierarchy dimension. NATURE CLIMATE CHANGE 3

4 1.4 Concern about climate change We studied people s concern about climate change using a scale consisting of four items taken from previous research in the cross-country study 1,2 (see Table S3). Participants rated their concern about climate change on these items on 6-point Likert scales, with higher scores indicating more concern about climate change. The internal reliability of the scale was high, Cronbach s α = Table S3. Climate change concern: The items, their means, standard deviations, and corrected item-total correlations in the cross-country study. Items M SD Corrected item-total correlation I worry that the state of climate is changing Climate change has severe consequences for humans and nature Climate protection is important for our future We must protect the climate s equilibrium Scale s Cronbach s α = 0.94, M = 4.88, SD = 1.21 Likewise, we assessed people s concern about climate change using the same approach in the additional Swiss study (see Table S4). The internal reliability suggested a sufficiently good scalability factor with Cronbach s α = NATURE CLIMATE CHANGE

5 Table S4. Climate change concern: The items, their means, standard deviations, and corrected item-total correlations in the additional Swiss study. Items M SD Corrected item-total correlation I worry that the state of climate is changing Climate change has severe consequences for humans and nature Climate protection is important for our future We must protect the climate s equilibrium Scale s Cronbach s α = 0.90, M = 4.88, SD = Data analysis Mokken scale analysis was conducted to test the quality of our knowledge scales. This method is subject to stricter assumptions than reliability analyses based on Cronbach s alpha 6 ; instead of assuming that all items have the same frequency distribution, a Mokken scale analysis explicitly takes into account (1) the latent knowledge of respondents about the subject of interest (i.e., climate change) and (2) key characteristics of the survey items (question difficulty on our case). Not only can a Mokken scale analysis rank participants according to their probability of positive responses (i.e., based on latent traits such as knowledge), it can also scale items based on their probability of being answered correctly. One of the important assumptions of a Mokken scale analysis is double monotonicity. Monotonicity firstly means that the expected order of respondents should be monotonically non-decreasing for each item. That is, the items that are responded to correctly by persons with little knowledge should also be answered correctly by persons with more knowledge. Secondly, the items should be monotonically ordered for each person: people who are able to correctly answer the difficult questions should also respond correctly to the less difficult and easier items. NATURE CLIMATE CHANGE 5

6 In a Mokken scale analysis, scalability is measured by Loevinger's coefficient H for the entire scale and H i for each item i. The Loevinger scalability coefficient H indicates the extent to which respondents can be accurately ordered by the suggested set of items, while scalability coefficient H i indicates the degree to which each item could be accurately ordered by the participants. H i and H will take values between 0 and 1, and the larger the H and H i values, the higher is the confidence in this ordering. A scale with a set of items with H values between 0.3 and 0.4 is considered to be an acceptable scale. H = indicates medium scalability, and H = suggests a strong scale. Concerning the individual items, the scalability coefficients H i for each individual item should be H i 0.3. The items kept in the knowledge scale were proved to be of good quality through the Mokken scale analysis both in the cross-country study (see Fig. 1) and the additional study. After conducting the Mokken scale analysis, we summed the number of correct responses for each respondent, for each of the three knowledge scales, and calculated the proportion of correct responses for each type of knowledge to examine what kind of knowledge was more present and which was less present in our participants. The three sum scores of the knowledge scales were included in the regression analyses described below. Further, in order to investigate the additional effects of knowledge on public concern about climate change after controlling for demographics and value orientations, we conducted hierarchical linear regression analyses with public concern as dependent variable in the crosscountry study. In Model 1, demographics, and value orientations were included as independent variables. In Model 2, the three types of knowledge were added as independent variables. The analysis was done for each country separately. In the main paper, we only reported the total effects of these predictors (Model 2 only) on concern about climate change for each different country (Table I). Here, we also present the results of the hierarchical regression analyses (Table S7). In order to examine the country differences regarding the three types of knowledge about climate change, a multivariate ANOVA was conducted 7. We included education level as covariate, country as independent variable (IV), and knowledge about physical 6 NATURE CLIMATE CHANGE

7 characteristics, knowledge about causes and knowledge about consequences as dependent variables (DVs). Likewise, using MANCOVA, we examined countries that differed in terms of the value orientations with egoistic value, altruistic value, and biospheric value as dependent variables and country as independent variable, and education level as covariate. In addition, a one-way ANCOVA was conducted to illustrate the country differences on the concern about climate change, with education level as covariate. In the additional study in Switzerland, we conducted hierarchical linear regression analysis to examine the impacts of cultural worldviews [Model 3(a)] and self-assessed knowledge [Model 3(b)]. With the concern about climate change as dependent variable, we included cultural worldviews in Model 3(a) and self-assessed knowledge in Model 3(b) in addition to Model 2 with demographics, value orientations, and objectively measured knowledge. 3. Additional results 3.1 Different types of knowledge According to the results in Fig. 1, our respondents seemed to be reasonably wellinformed about climate change related questions. Specifically, in the cross-country study, within the full sample of 2,495 people, average correct response constituted 49.2% for knowledge about the physical characteristics, 59.7% for knowledge about the causes and 70.4% for knowledge about the consequences of climate change. The scale with four items about the physical aspects of climate change was acceptable, H = 0.41, H i 0.27 and ρ = 0.57 (Fig. 1). Respondents appeared least knowledgeable on this dimension: more than half of the participants managed to respond correctly about how CO 2 is produced (item 1) and that CO 2 is not harmful for plants (item 2), which accounted for 80% and 56% correct responses, respectively. By contrast, few people knew about the CO 2 emissions during the operation of nuclear power plants (item 3, 31% correct) and about the comparison of environmental impact between CO 2 and methane (item 4, 29% correct). In addition, the four items that intended to assess respondents knowledge regarding NATURE CLIMATE CHANGE 7

8 climate change causes formed a satisfactory one-dimensional scale, H = 0.42, H i 0.38, and ρ = 0.56 (Fig. 1). Most participants knew about the CO 2 increase in the atmosphere (item 5, 83% correct responses). Also, the items about the facts that human activities are responsible for climate change and temperature increases in the past centuries were well known (item 6: 75% correct on average and item 7: 64% correct responses). However, only 18% of the respondents knew about the changes in CO 2 concentrations during the past centuries (item 8). The four items about the consequences of climate change formed a reliable onedimensional scale with a Loevinger scalability coefficient of H = 0.41, the individual scalability coefficients where Hi 0.37, and a reliability coefficient of ρ = 0.61 (Fig. 1). Respondents were best informed about the consequences of climate change. Most participants knew about the rising see level (Fig. 1, item 9) and the increase of extreme weather events (item 10), which accounted for 90% and 89% correct responses, respectively. By contrast, participants seemed to be less knowledgeable about the expected pattern in climate change (item 11) and precipitation change (item 12), which made up 52% and 51% correct responses respectively. In the additional Swiss study, the Loevinger scalability coefficients (H) and reliabilities (ρ) for the three scales of knowledge about climate change were H = 0.43, ρ = 0.57 for knowledge about physical characteristics; H = 0.48, ρ = 0.62 for knowledge about causes; and H = 0.50, ρ = 0.62 for knowledge about consequences. The individual scalability coefficients (H i ) for each item were above 0.40 in each knowledge scale. Consistent with the results of the cross-country study, the proportions of correct responses for knowledge about the physical characteristics, about the causes, and about the consequences of climate change were 50%, 59% and 75%, respectively. Participants tended to report their own knowledge level about climate change as moderate on a scale from 1 to 6 (M = 3.53, SD = 1.11). 3.2 Differences among countries regarding different types of knowledge We examined the differences between the six countries for the three types of knowledge (Table S5). The MANOVA results indicated significant differences among countries on 8 NATURE CLIMATE CHANGE

9 knowledge about physical characteristics, causes, and consequences of climate change (see Table S5). To be more specific, respondents from Germany and Switzerland had significantly higher scores on knowledge about physical aspects of climate change than participants from Canada and the US. Chinese respondents knew significantly more about the causes of climate change than the respondents from the other countries. German and Swiss respondents were most knowledgeable about the consequences of climate change. In contrast, participants from the US had the lowest level of knowledge about climate change among the six countries we surveyed, independent of the type of knowledge. The effect size (η 2 ) suggested that the sample size used in this study was sufficient to detect the significance (at p < 0.05) of country differences about climate change knowledge (Table S5) 8. Table S5. Knowledge about physical characteristics, causes, and consequences of climate change: Means and 95% confidence intervals per country. Physical knowledge Causes knowledge Consequences knowledge M 95%CI M 95%CI M 95%CI Canada 0.45 b [0.42, 0.48] 0.60 b [0.57, 0.62] 0.67 b [0.64, 0.69] China 0.50 a,b [0.47, 0.53] 0.68 a [0.65, 0.71] 0.69 b [0.66, 0.71] Germany 0.55 a [0.52, 0.57] 0.62 b [0.59, 0.64] 0.79 a [0.76, 0.81] Switzerland 0.53 a [0.50, 0.56] 0.61 b [0.58, 0.63] 0.77 a [0.75, 0.80] UK 0.49 a,b [0.46, 0.52] 0.58 b [0.55, 0.61] 0.71 b [0.69, 0.74] US 0.45 b [0.43, 0.48] 0.52 c [0.49, 0.54] 0.61 c [0.59, 0.64] F(df 1, df 2 ) 7.59***(5, 2413) 16.64*** (5, 2413) 26.22*** (5, 2413) η Notes. Means with different superscripts within a column are significantly different from each other at p < 0.05 (after Bonferroni correction). *** p < Education level was included as a covariate. 3.3 Differences between countries regarding value orientations In addition, differences between countries regarding the three value orientations were investigated (Table S6). Results of the MANOVA suggested significant differences among countries on egoism, altruism, and biospherism (see Table S6). More exactly, the participants from China had significantly higher scores on egoism than the ones from other countries. NATURE CLIMATE CHANGE 9

10 They were followed by people from Canada, the UK, and the US while German and Swiss participants appeared to have least interest in self-importance and self-benefits. Chinese and Swiss respondents were found to be most altruistic in our research. Respondents from the United States, by contrast, found it least important to consider other people when making decisions. Likewise, respondents from China and Switzerland reported significantly higher biospheric values than the respondents from other countries. Table S6. Egoism, altruism, and biospherism: Means and 95% confidence intervals per country. Egoism value Altruism value Biospherism value M 95%CI M 95%CI M 95%CI Canada 2.57 b [2.41, 2.73] 5.59 a,b [5.46, 5.72] 5.53 b [5.39, 5.67] China 4.24 a [4.07, 4.41] 5.76 a [5.62, 5.91] 6.04 a [5.89, 6.19] Germany 2.10 c [1.94, 2.26] 5.66 a,b [5.52, 5.80] 5.55 b [5.40, 5.69] Switzerland 2.23 b,c [2.07, 2.39] 5.73 a [5.59, 5.87] 5.88 a [5.73, 6.02] UK 2.66 b [2.49, 2.83] 5.66 a,b [5.52, 5.80] 5.51 b [5.37, 5.66] US 2.54 b [2.38, 2.70] 5.40 b [5.26, 5.53] 5.28 b [5.14, 5.42] F (df 1, df 2 ) 81.80*** (5, 2413) 3.59** (5, 2413) 14.17*** (5, 2413) η Notes. Means with different superscripts within a column are significantly different from each other at p < 0.05 (after Bonferroni correction). *** p < Education level was included as a covariate. 3.4 Differences between countries regarding concern about climate change A one-way ANCOVA revealed significant differences between countries about the concern about climate change. As shown in Table S7, European respondents appeared to be rather concern about climate change and Chinese participants were substantially more concerned about climate change than people from the other countries. Participants from the US seemed to be the least worried about climate change. The results seem to be in line with previous studies NATURE CLIMATE CHANGE

11 Table S7. Concern about climate change: Means and 95% confidence intervals per country. Concern about climate change M 95%CI Canada 4.84 b [4.72, 4.95] China 5.37 a [5.25, 5.49] Germany 4.90 b [4.78, 5.01] Switzerland 4.95 b [4.83, 5.06] UK 4.78 b [4.66, 4.90] US 4.51 c [4.39, 4.62] F (df 1, df 2 ) 22.37*** (5, 2413) η Notes. Means with different superscripts within a column are significantly different from each other at p < 0.05 (after Bonferroni correction). *** p < Education level was included as a covariate. 3.5 Hierarchical regression analyses on concern about climate change According to the results of the hierarchical regression analyses of the cross-country study, the introduction of demographics and value orientations in Model 1 was significant and explained a great part of the variance (17% 34% explained variances) in concern about climate change across the countries (Table S8). The inclusion of knowledge about physical characteristics, causes, and consequences of climate change (Model 2) further increased the explained variance of concern about climate change across the countries. That is, including the three types of knowledge about climate change significantly improved the explained variance with 2% to 18% (Table S8). In China, different types of knowledge about climate change only marginally improved the regression model with 2%, F change (3, 378) = 2.55, p = A possible explanation for this finding may be that the Chinese participants in general had a higher level of knowledge about the causes of climate change than people from the other countries (Table S4), the inclusion of the three types of knowledge therefore did not additionally improve their concern about climate change. In all six countries, the correlations NATURE CLIMATE CHANGE 11

12 between the three types of knowledge were small (r < 0.4) and variance inflation factors (VIF) were slightly bigger than 1 (1.10 < VIF < 1.47), so that multicollinearity was not a concern 7,12. Table S8. Hierarchical regression analyses predicting public concern about climate change in the cross-country survey. Models and predictors per country R 2 ΔR 2 F (df 1, df 2 ) ΔF (df 1, df 2 ) Canada Model 1(without knowledge as *** (7, 418) predictor) Model 2 (with knowledge as *** (10, 415) 20.91*** (3, 415) predictor) China Model *** (7, 381) Model *** (10, 378) 2.55 (3, 378) Germany Model *** (7, 402) Model *** (10, 399) *** (3, 399) Switzerland Model *** (7, 385) Model *** (10, 382) 34.94*** (3, 382) UK US Model *** (7, 371) Model *** (10, 368) 25.18*** (3, 368) Model *** (7, 415) Model *** (10, 412) 33.88*** (3, 412) Notes. Model 1 included gender, age, dummy variables for low education vs. high education and for middle education vs. high education, egoistic values, altruistic values, and biospheric values; Model 2 additionally included knowledge about physical characteristics, causes, and consequences of climate change; *** p < In the additional Swiss study, the regression analysis with concern about climate change as dependent variable, the introduction of cultural worldviews, in addition to demographics, value orientations and three types of knowledge, slightly but significantly increased the 12 NATURE CLIMATE CHANGE

13 explained variance of the dependent variable with 6.9%. Individualism was negatively related to concern about climate change while hierarchy had no significant relation (see Model 3(a) in Table S9). Similarly, we included self-assessed knowledge after the demographics, value orientations, and three types of knowledge. No significant impact of subjective measured knowledge was found on concern about climate change (see Model 3(b) in Table S9). Additionally, the main results remained the same after including cultural worldviews and subjective measured knowledge at the same time (see Model 4 in Table S9). In short, including cultural worldviews somewhat improved the model fit and therefore seem to have a unique relation with concern about climate change, which is independent of the relation between value orientations and concern about climate change. The additional explained variance of cultural worldviews to the model is however not as large as that of the value orientations and knowledge together (R 2 = 0.35). It is thus likely that there is some overlap between cultural worldviews and value orientations. Nevertheless, an interesting question to address in a future study would be whether cultural worldviews are more important in explaining public concern about climate change in some countries than in other countries. NATURE CLIMATE CHANGE 13

14 Table S9. Hierarchical regression analysis predicting public concern about climate change in the additional Swiss survey. Model 2 Model 3(a) Model 3(b) Model 4 B 95%CI B 95%CI B 95%CI B 95%CI Gender # -0.26* [-0.46, -0.06] -0.22* [-0.42, -0.03] -0.26* [-0.46, -0.05] -0.22* [-0.42, -0.03] Age 0.00 [-0.01, 0.01] 0.00 [0.00, 0.01] 0.00 [-0.01, 0.01] 0.00 [-0.01, 0.01] Low education Ϯ Middle education Ϯ Egoistic values 0.06 [-0.33, 0.46] 0.26 [-0.12, 0.64] 0.06 [-0.34, 0.46] 0.26 [-0.12, 0.64] 0.08 [-0.15, 0.31] 0.17 [-0.05, 0.39] 0.08 [-0.15, 0.31] 0.17 [-0.05, 0.39] 0.02 [-0.04, 0.09] 0.00 [-0.06, 0.07] 0.02 [-0.04, 0.09] 0.01 [-0.06, 0.07] Altruistic values [-0.11, 0.09] [-0.12, 0.09] [-0.11, 0.09] [-0.12, 0.09] Biospheric values 0.30*** [0.20, 0.40] 0.27*** [0.17, 0.36] 0.30*** [0.20, 0.40] 0.27*** [0.17, 0.36] Physical knowledge [-0.44, 0.29] [-0.40, 0.30] [-0.45, 0.30] [-0.41, 0.30] Causes knowledge 1.00*** [0.64, 1.37] 0.84*** [0.49, 1.19] 1.00*** [0.64, 1.37] 0.84*** [0.49, 1.19] Result knowledge 0.35 [-0.06, 0.75] 0.36 [-0.03, 0.75] 0.35 [-0.07, 0.76] 0.36 [-0.03, 0.75] Individualism -0.30*** [-0.40, -0.20] -0.30*** [-0.40, -0.20] Hierarchy [-0.15, 0.10] [-0.16, 0.10] Self-assessed knowledge 0.00 [-0.10, 0.10] 0.00 [-0.09, 0.09] R F(df 1, df 2 ) 17.40*** (10, 324) 19.28*** (12, 322) 15.77*** (11, 323) 17.74*** (13, 321) F(df 1, df 2 ) N.A *** (2, 322) 0.00 (1, 323) 12.64*** (3, 321) Notes. # Gender: 0 = female, 1 = male. Ϯ Dummy variable with high education as reference group. * p < 0.05, ** p < 0.01, *** p < NATURE CLIMATE CHANGE

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