Heatwaves and online climate sentiment: evidence from Chinese social media

As heatwaves grow in frequency and intensity under climate change, their effects extend beyond physical harm to shaping how people discuss and perceive climate change itself. Understanding these emotional and communicative responses is vital for effective climate engagement and for designing more responsive climate communication and policy strategies. This study analyzes 154,436 climate change-related posts from 31 Chinese provincial capitals across a five-year period (2019-2023) on Sina Weibo, integrating heatwave indicators with sentiment scores derived from three models (SKEP, SnowNLP and RoBERTa), based on monthly aggregated data. Leveraging fixed-effects OLS, Bartik-type instrumental variables and system GMM estimations, we uncover three key patterns. First, we find that heatwaves are associated with a significant increase in the volume of climate-related discussions. Second, this heightened attention is accompanied by a marked decline in sentiment, suggesting a paradox where rising awareness may coincide with emotional strain. Third, these associations are especially pronounced in Southern China and megacities, highlighting spatial disparities in observed emotional responses. These findings suggest that climate policies should integrate emotional resilience and region-specific communication strategies to enhance public engagement during heatwaves. Extreme heat events create short, context-dependent windows in which climate risks become emotionally salient, making the timing of climate communication as critical as institutional design. Time-sensitive emotional signals on social media can function as early indicators of public vulnerability and receptiveness, informing adaptive and responsive policy interventions. Emotional responses to heatwaves are heterogeneous and non-uniform, requiring balanced communication strategies that avoid both alarmism and emotional neglect. Beyond conventional indicators such as mortality or economic losses, heatwave risk assessment and policy design should incorporate broader psychological and emotional impacts.