Hellen Temme

PurposeClimate policy acceptance and sustainable behavior partially depend on accurate CO₂ estimates and perceived policy effectiveness. We tested whether seeding, an intervention in which people learn accurate CO₂ values for representative foods that serve as anchors for estimating other foods' emissions, can increase carbon numeracy (i.e., the ability to estimate carbon footprints of foods without explicit calculations). MethodTwo pre-registered experiments examined whether increased carbon numeracy also enhances perceived effectiveness and acceptance of a value-added tax (VAT) reform on food and food choice. Study 1 (N = 974) tested whether seeding increased the effectiveness and acceptance of a VAT increase for meat. Study 2 (N = 1,023) extended this by explaining the policy mechanism. Food choice was assessed by asking participants to select a food box (vegan, vegetarian, or meat-based) in a lottery.ResultsBoth studies found that seeding improved carbon numeracy (ηp² = .55−.58, p < .05). However, neither seeding nor policy explanations significantly increased policy acceptance or food choice, although explaining the policy increased perceived effectiveness (β = .21−.24, p < .05). In both studies, perceived effectiveness (r = .31−.41, p < .001) and policy acceptance (r = .30−.49, p < .001) were significantly related to selecting a non-meat food box. Exploratory analyses revealed that perceptions of a potential price change were the strongest predictor of policy acceptance (β = -.47, p < .001). ConclusionThese findings suggest that VAT policy changes could require both explaining environmental benefits and addressing perceived personal costs.

Climate change poses an existential threat to humanity, with profound ecological, social, and health consequences. Beyond policy and structural transformations, effective mitigation and adaptation require widespread behavioural change. Knowledge about the causes, impacts, and solutions of climate change is therefore a key target of climate communication. Yet, the empirical role of knowledge in fostering climate action remains unclear, partly due to varying conceptualizations and limited psychometric quality of existing measures. To address these limitations, we developed the 15-item Climate Change Knowledge (CCK) scale using a mixed-methods approach that integrates expert input and psychometric validation. The scale captures three domains: ecological mechanisms, societal impacts, and mitigation/adaptation measures, reflecting content validity grounded in both scientific literature and real-world understanding. Based on a representative German sample (N = 10,377), the CCK scale demonstrated good factorial, convergent, divergent, and criterion validity. It captures climate-specific knowledge that is distinct from general/ environmental knowledge and risk perception, and it explains unique variance in readiness for climate action, particularly individual behaviour, policy acceptance and political participation beyond these constructs. The CCK scale provides a concise, domain-specific and empirically validated instrument for assessing climate-related knowledge. By clarifying construct boundaries and enabling precise tests of how knowledge relates to engagement, it supports theory development and evaluation of climate education and communication initiatives. In doing so, it strengthens the evidence base for policies and interventions that aim to promote climate action.

Objectives: This study examines the psychological construct vaccination readiness against cholera in six African countries (Ghana, Kenya, Nigeria, South Africa, Tanzania, and Uganda) based on the 7C model of vaccination readiness (measuring confidence, complacency, constraints, calculation, collective responsibility, compliance, conspiracy). This allows testing the generalizability of the 7Cs to a non-WEIRD and previously under-researched infection context with a low to moderate vaccination rate (< 50%), which can provide valuable insights for vaccine roll-out and epidemic (and pandemic) preparedness. Methods: A total of 14,132 English-speaking participants were recruited via an online survey on Facebook. Measurement invariance analyses showed scalar invariance, which allows cross-country mean comparisons and supports the generalizability of cholera vaccination readiness across countries. Results: At the individual level, vaccination readiness was significantly associated with self-reported vaccination status against cholera (d = 0.32) and general vaccination status across several vaccines (r = .35). Individuals with personal experience with cholera showed higher vaccination readiness (d = 0.14). At the country level, average vaccination readiness correlated strongly with cholera incidence over the past three years (ρ = .89), suggesting a higher vaccination readiness in countries with higher disease burden and risk. Conclusion: The study provides evidence for the generalizability of the 7C model across countries and infectious diseases and shows that cholera vaccination readiness is related to self-reported risk and disease experience. For pandemic preparedness the data suggest that vaccination readiness builds where disease experience already exists, leaving populations without prior exposure at greatest risk during a novel outbreak.

Beyond geophysical challenges, climate change imposes unequal risks and burdens across affected groups and is unequally caused by them, exacerbating social injustices. Psychological measures to assess climate justice beliefs are missing. We therefore developed the Sensitivity to Climate Injustice (SCI) Scale to capture individuals’ evaluations of climate-related disparities between groups. Across four studies with German-speaking samples (N1 = 1,084; N2 = 1,998, N3 = 1,092; N4 = 1,119), the eight-item scale was validated, assessing two correlated factors: cause (perceived contribution disparities) and suffer (perceived burden disparities). The SCI showed mostly expected relations with other traits in a nomological network. Sensitivity to climate injustice also demonstrated strong criterion validity: the two factors differentially predict readiness for climate action and climate-relevant behaviour. By providing a theory-derived, reliable, and valid measure, the SCI fills a crucial gap, enabling psychological research on sensitivity to inequality as a potential driver of climate action.

Increasing the value-added tax (VAT) on animal- and reducing it on plant-based foods can reduce greenhouse gas emissions and diet-related disease burden by shifting consumption toward more sustainable dietary patterns. Yet, public acceptance remains low. Two pre-registered online experiments in Germany examined whether acceptance is linked to cost overestimation and whether communicating accurate price information increases public support. In Study 1 (N = 161), participants submitted a personal grocery receipt and were randomly assigned to one of three VAT scenarios: an increase on animal-based products (7% to 19%), a reduction on plant-based products (7% to 0%), or both. Policy acceptance was measured before and after participants estimated the price change of their receipt and received feedback on the actual change. Although participants systematically misestimated costs, initial acceptance (β = .92, p < .001) rather than misestimation (β = .03, p = .329) was the dominant predictor of subsequent acceptance. When given the opportunity to eliminate products from their receipt after receiving feedback on the actual change, participants predominantly removed meat and dairy. Study 2 (N = 299) focused on the VAT combination policy using a standardized €30 receipt. Participants either estimated costs before receiving feedback, received accurate price information only, or received only a policy description. Acceptance in the estimation (d = .54) and information (d = .33) conditions significantly increased compared to the control condition, while misestimation showed no significant relationship with acceptance. These findings suggest that expressing price changes in Euros rather than VAT percentages represents a simple, scalable strategy for increasing public support for sustainable food taxation.

Climate change poses an existential threat to humanity, with profound ecological, social, and health consequences. Beyond policy and structural transformations, effective mitigation and adaptation require widespread behavioural change. Knowledge about the causes, impacts, and solutions of climate change is therefore a key target of climate communication. Yet, the empirical role of knowledge in fostering climate action remains unclear, partly due to varying conceptualizations and limited psychometric quality of existing measures.To address these limitations, we developed the 15-item Climate Change Knowledge (CCK) scale using a mixed-methods approach that integrates expert input and psychometric validation. The scale captures three domains: ecological mechanisms, societal impacts, and mitigation/adaptation measures, reflecting content validity grounded in both scientific literature and real-world understanding.Based on a representative German sample (N = 10,377), the CCK scale demonstrated good factorial, convergent, divergent, and criterion validity. It captures climate-specific knowledge that is distinct from general/ environmental knowledge and risk perception, and it explains unique variance in readiness for climate action, particularly individual behaviour, policy acceptance and political participation beyond these constructs.The CCK scale provides a concise, domain-specific and empirically validated instrument for assessing climate-related knowledge. By clarifying construct boundaries and enabling precise tests of how knowledge relates to engagement, it supports theory development and evaluation of climate education and communication initiatives. In doing so, it strengthens the evidence base for policies and interventions that aim to promote climate action.

Effective communication about climate change, climate action, and their health impacts is central to the Planetary Health approach, which emphasizes the inseparable linkage between safeguarding human well-being and protecting ecological systems. Prior research indicates that trust shapes individuals’ readiness for climate action. Accordingly, the perceived credibility of communicators, particularly their trustworthiness, is a central driver of audiences’ acceptance of information and recommendations. Guided by Source Credibility Theory and the Elaboration Likelihood Model, this mixed-methods study examines which communicators are perceived as trustworthy in integrated climate–health communication and whether expert recommendations align with public trust.The study combined qualitative interviews and an online survey with open-ended responses from experts across various fields, followed by a quota-representative survey of the German general public (N = 1,130). Experts nominated communicators across scientific, medical, institutional, educational, and community-based sectors and made stronger distinctions between communicators for climate action and health topics. In contrast, public trust patterns were highly consistent across both domains, largely independent of the communication topic. Scientists, medical professionals, and public health institutions received the highest trust ratings, whereas the federal government and public figures were trusted the least.Overall, the results highlight alignments and discrepancies between those who shape communication strategies and those who receive them. Aligning communication strategies with audience perceptions of credibility and integrating trusted professional and community-based communicators may strengthen Planetary Health communication and enhance readiness for climate action.

Understanding climate action—from everyday choices to backing policies and engaging in politics—is essential for accelerating mitigation. Using German samples (total N = 6,918) we find evidence for a common tendency that cuts across these areas, which we call readiness for climate action. We also identify key predictors linked to this readiness: health risks due to climate change , trust in institutions, social norms, perceived effectiveness of policies, self-efficacy, and knowledge about climate issues. Higher readiness was tied to real, costly climate friendly behaviors—completing a demanding task to protect the environment, paying money to reduce CO₂-emissions, and donating to an environmental cause—and improved prediction beyond established measures. This work advances behavioral climate science by introducing the overarching concept and allowing to test what is shared versus specific across behaviors. It provides validated measures for readiness and its predictors; links the disposition to consequential behavior; and points to testable mechanisms and levers for policy making and communication.