资源环境科技发展态势分析平台

When multiple extremes occur in rapid sequence, their impacts cascade to cause disproportionate damages. However, the prevalence of univariate definitions and inability to identify low-likelihood events in short observations/simulations leave the knowledge on sequential extremes sparse. Leveraging two initial-condition large ensembles, we project future changes in historically-unprecedented sequential flood-hot extremes in China. Results show that despite dozens of 1 in 50-year floods and hot extremes in more than 2000 years of historical simulations, their sequenced occurrence within a week has no historical precedent. This out-of-ordinary configuration is projected to be increasingly possible across China, with earlier emergence and larger frequency increases expected in Southwest and Southeast China. The direction, spatial extent and magnitude of projected changes in unprecedented sequential extremes cannot be explained by internal variability alone, though it has the potential to modulate human-caused changes in emergence timing and magnitude.