Detectable human influence on daytime-nighttime compound heat waves over China

Daytime-nighttime compound heat waves (CHWs) pose severe threats to human society. In the context of climate warming, China has experienced significant increases and intensification of CHWs since the 1960s. This article performs a detection and attribution analysis on observed changes in CHWs over China and within its four subregions: northwestern China, northeastern China, the Yangtze River valley, and southern China, based on the Coupled Model Intercomparison Project Phase 6 (CMIP6) simulations. Notably, an updated optimal fingerprinting approach with estimating equations is utilized, which is improved by more efficient point estimation and more plausible uncertainty evaluation. In general, the findings highlight a primary contribution of human influence to aggravated CHWs in China. The anthropogenic (ANT) signal can be detected and separated from natural (NAT) forcing in the observed increases in both frequency and intensity of CHWs over China and within the four subregions. Among the ANT influence, greenhouse gas (GHG) emission is detected to play a dominant role, despite that the distinguished GHG signal in the three-signal analysis shows greater uncertainty over the subregions.