Changes caused by human activities in the high health-risk hot-dry and hot-wet events in China

Compound heat anomalies associated with humidity, such as compound hot-dry events and hot-wet events, pose greater health risks than single heat anomalies. Here, we utilize ambulance dispatch data along with air temperature and relative humidity to study human impacts on these events in China. We show that relying solely on temperature without considering humidity may underestimate the health risks of these events on populations. Over the past 40 years, anthropogenic activities have increased hot-dry events by 2.34 times and decreased hot-wet events by 0.63 times, especially in the Yangtze River region, compared to natural forcing. We also speculate that, in the future up to 2060, under the carbon-neutral scenario, the frequencies of high health-risk hot-dry events and hot-wet events caused by human activities can be reduced by one-half and over one-fifth, respectively, compared to the high-emissions scenario. These findings provide guidance for assessing health risks under global warming.Over the past 40 years, human activities in China have led to high health-risk compound heat anomalies, especially in the Yangtze River region, which could be reduced by 2060, if carbon-neutral scenarios are implemented, according to analysis of the ambulance dispatch data, air temperature, and relative humidity.