Concern about the health effects of climate change according to experiences of climate events: International comparison of UK and Australian adults

• Australia and United Kingdom (UK) nationally representative surveys of 4,378 adults. • Adults reported climate event experiences and perceived health threats. • 60% of Australians reported experiencing a climate event in the past five years compared to 29% of UK residents. • Heatwaves were the most common experience in both countries. • Climate event experiences accounted for 23-35% of perceived climate health threats. Climate change is now recognised as a global public health emergency, characterised by increasing frequency and severity of climate hazards worldwide. There is limited evidence on the proportion of the population that has directly experienced climate events, how this varies between countries, and the subsequent micro (focused on oneself) and macro (focused on wider society) perceived impact on health. We conducted nationally representative surveys of 4,378 individuals in Australia and the United Kingdom in February 2025. Participants reported climate event experiences over five years, micro and macro perceived health threats, and sociodemographic characteristics. Logistic regression models estimated the likelihood of perceiving climate change as a health threat based on experiences of climate events, while population attributable fractions examined the proportion of health concerns cases attributable to specific climate events. Results revealed significant cross-national differences: 59% of Australian respondents experienced climate events within five years versus 29% in the UK. Heatwaves were the most common experience in both countries and showed the strongest association with perceived health threats to ‘my health’, particularly among Australians (odds ratio: 1.74, 95% CIs: 1.46-2.07). Climate event experiences accounted for 23-35% of perceived climate health threats. Our findings demonstrate that experiencing climate events elevates health threat perceptions across contrasting geographical contexts. Mental health burden is likely to increase as climate-related events—including heatwaves, wildfires, and floods—become more frequent and severe due to accelerating global heating. This underscores an urgent need for climate change mitigation alongside targeted mental health interventions addressing climate-related psychological impacts.