Mirjam Annina Jenny

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.

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.

Conspiracy narratives, particularly those related to vaccines, pose a significantchallenge to vaccine acceptance. Vaccine-related conspiracy narratives are sometimesendorsed and spread even by medical experts, such as physicians. In an exploratorystudy, we investigated whether vaccine-related conspiracy narratives spread bymedical experts are more persuasive than conspiracy narratives spread by laypeople.In a 2 (source: physician vs layperson) x 2 (time: pre- vs post-exposure to conspiracynarrative) experimental design, UK-based participants (N = 291) were exposed to aninterview in which either a physician or a layperson endorsed a vaccine-relatedconspiracy narrative.The results indicated that exposure to the conspiracy narrative led to more negativeattitudes towards vaccination and reduced the intention to vaccinate independent ofthe source. However, the decline in vaccination intention was significantly greater whenthe conspiracy narrative was shared by a physician. Further, the results showed thatparticipants with a higher level of conspiracy mentality attributed more expertise to thesource of the conspiracy narrative than participants with a lower level of conspiracymentality.These findings suggest that expert sources can amplify the persuasive impact ofconspiracy narratives, potentially exacerbating vaccine hesitancy. Given that somephysicians engage in the dissemination of conspiracy narratives, interventions toreduce the spread of and belief in conspiracy narratives should focus not only on thegeneral public but also on medical experts.

Introduction Climate change is a paramount global health threat with multifaceted implications. Societal change is required to mitigate the negative effects of climate change, as well as help people adapt to the associated health risks. This requires situation-specific, large-scale data to help scientists and policymakers understand public perceptions and behaviours and identify the levers to increase public readiness to act against climate change and protect health. The Planetary Health Action Survey (PACE) assesses this readiness to act as a regular monitoring of representative samples in Germany. The ongoing monitoring seeks to develop and refine an integrated conceptual model of the trait-like readiness to act, comprising policy acceptance, political participation and individual behaviours as indicators of the trait. It also proposes as set of determinants to explain different levels of readiness to act. This study protocol provides newly developed valid measurement instruments and the methodological details of the monitoring. Method and analysis PACE assesses indicators of the readiness to act and a set of sociocognitive factors predicting the readiness to act in continuous cross-sectional data collections. The latter comprise climate change knowledge, trust in institutions, perceived health risks, self-efficacy, social norms and perceived effectiveness of policy measures. The online questionnaire is updated regularly. Data collection involves non-probabilistic quota samples from Germany (n≈1000 at each collection). Ethics and dissemination The project adheres to the ethical guidelines of the University of Erfurt and the German Research Foundation. Ethical clearance was granted by the University’s Institutional Review Board (No #20220525/No #2024-01). Participants are guaranteed confidentiality and anonymity, and informed consent is obtained before participation. Results will be published in peer-reviewed journals. Additionally, we aim to inform and empower the public and support stakeholders (media, policymakers, climate protection organisations) in preparing climate communication and assisting policymakers through the project website including an interactive tool, detailed reports and short summaries for practitioners.

Conducting high‐quality overviews of reviews (OoR) is time‐consuming. Because the quality of systematic reviews (SRs) varies, it is necessary to critically appraise SRs when conducting an OoR. A well‐established appraisal tool is A Measurement Tool to Assess Systematic Reviews (AMSTAR) 2, which takes about 15–32 min per application. To save time, we developed two fast‐and‐frugal decision trees (FFTs) for assessing the methodological quality of SR for OoR either during the full‐text screening stage (Screening FFT) or to the resulting pool of SRs (Rapid Appraisal FFT). To build a data set for developing the FFT, we identified published AMSTAR 2 appraisals. Overall confidence ratings of the AMSTAR 2 were used as a criterion and the 16 items as cues. One thousand five hundred and nineteen appraisals were obtained from 24 publications and divided into training and test data sets. The resulting Screening FFT consists of three items and correctly identifies all non‐critically low‐quality SRs (sensitivity of 100%), but has a positive predictive value of 59%. The three‐item Rapid Appraisal FFT correctly identifies 80% of the high‐quality SRs and correctly identifies 97% of the low‐quality SRs, resulting in an accuracy of 95%. The FFTs require about 10% of the 16 AMSTAR 2 items. The Screening FFT may be applied during full‐text screening to exclude SRs with critically low quality. The Rapid Appraisal FFT may be applied to the final SR pool to identify SR that might be of high methodological quality.

Vaccine effectiveness and safety concerns can prevent people from receiving their first Covid-19 vaccines or boosters. Understanding the vaccine mechanism may lead people to perceive vaccine effectiveness appropriately. This study tested whether helping people understand the vaccine’s mechanism could improve their perceived vaccine safety and effectiveness. In a preregistered study, N = 1,548 unvaccinated or non-boosted participants were randomly presented with one of three communication formats: a fact box (a benefit-risk profile in tabular format; control condition), an expository text (i.e., a purely factual explanation) plus fact box, or an analogy plus fact box. Participants rated the vaccine’s effectiveness in preventing a Covid-19 disease, their perceived risk of getting vaccinated, and their intention to get vaccinated or boosted (depending on their vaccination status). Reading either additional text about the vaccines’ mechanism increased participants’ effectiveness ratings for the vaccine to prevent Covid-19 but did not affect risk ratings or vaccination intentions. The participants’ vaccine-related perceptions and intentions did not differ between the two text types. Elaborating on the vaccine’s mechanism of protection, in addition to presenting the benefit-risk profile of a vaccine, can lead people to perceive the vaccine effectiveness as slightly higher, yet it is insufficient to increase vaccination intentions.