Data and code from: Rising flood risks in semi-arid South Asia driven by changing intraseasonal oscillations under global warming

Northwestern South Asia, encompassing the historically semi-arid regions
of Pakistan and northwest India, has seen increased persistent heavy
rainfall and catastrophic flooding in recent decades. While most studies
emphasize seasonal mean changes, the role of subseasonal dynamics remains
unclear. Here, we present observational evidence that the
northward-propagating monsoon intraseasonal oscillation (ISO) has
strengthened and penetrated farther inland, with its convective anomalies
amplifying rainfall extremes. Simultaneously, the
southeastward-propagating midlatitude ISO along the westerly jet has
slowed, prolonging anomalous circulations that sustain rainfall episodes.
Together, these ISOs account for ~44% of the observed increase in flood
frequency, a contribution comparable to that from mean-state changes
(~40%). CMIP6 projections suggest that these ISO–driven processes will
further intensify flood risks, posing escalating threats to this
climate-sensitive region under continued global warming. Our findings
reveal a fundamental yet overlooked mechanism linking subseasonal
variability to emerging hydroclimatic extremes in a warmer world.