Nonlinear increase of compound drought-heatwave events since the early 2000s

Compound drought–heatwave events (CDHEs) have significantly increased
since the early 2000s, posing elevated risks to socio-ecosystems. However,
the physical characteristics of drought- and heatwave-leading CDHEs and
their relative contributions to the overall increase remain unexplored.
Using a multi-hazard pair generation algorithm with daily reanalysis data,
we show that this increase is primarily driven by heatwave-leading CDHEs,
with the slope of increase in affected land area rising nearly eightfold,
from 1.6% to 13.1% per °C since the early 2000s. This pattern is evident
at the global scale but also shows considerable regional variation. We
find that the nonlinear amplification of land–atmosphere coupling since
the late 1990s has not only induced the emergence of a statistically
significant positive sensitivity but has also resulted in a marked
increase in sensitivity in high occurrence regions. These findings
highlight the importance of considering the regional risks associated with
heatwave-leading CDHEs when adapting to climate change.