Rising flood risks in semiarid South Asia driven by changing intraseasonal oscillations under global warming.
Where this comes from
- Record sourced from PubMed, PMID 41931612.
- Also identified by DOI 10.1126/sciadv.aea0082 and PMC identifier 13048259.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Northwestern South Asia, encompassing the historically semiarid 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 mid-latitude 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.