Abstract
Climate change-induced extreme heat (EH) events intensify atmospheric surface ozone (O(3)) pollution, posing growing threats to public health and environment. To address the lack of rigorous empirical confirmation regarding the causal impact of EH on O(3) despite their observed co-occurrence, this study develops a robust statistical framework to assess this relationship across China. The framework integrates three checkpoints: (1) correlational checkpoint based on linear mixed model; (2) causal checkpoint based on instrumental variable, Heckman two-step selection model, and propensity score methods with generalized bootstrap validation; and (3) directional (of causality) checkpoint based on transfer entropy. Results consistently demonstrate a statistically significant causal effect of EH on elevated O(3) levels, with the dominant influence flowing from EH to O(3) nationwide and across most provinces in China. These findings support integrated air quality management and climate adaptation strategies, guiding policy interventions to mitigate the compound risks of EH and O(3) pollution.