Detectable Increases in Sequential Flood-Heatwave Events Across China During 1961-2018

Traditional univariate analysis on weather and climate extremes failed to consider temporally compounding events and the resulting cascading impacts. A case in point is a sequence of flood and heatwave within a week, which slows recovery and amplifies damages. We show that across China, floods and heatwaves seldom occurred serially within seven days in the past, but after 2000 the probability is five-to-ten times higher in southern, northwestern and northeastern sectors. It is the significant increase in heatwaves that alters the clustering of independent extremes, and facilitates the emergence of sequential extremes. Typhoon-participating sequential extremes have also increased significantly in frequency in both inland and coastal areas, with the fastest rate at around 200% decade(-1) registered within the 30-35 degrees N latitudinal band. The observed increases in sequential flood-heatwave events are discernibly stronger and more widespread than what would be expected from pure random variability, implying a detectable role of anthropogenic forcings.