Greenhouse warming will make the sensitivity of the Indian summer monsoon to the El Niño‒Southern Oscillation almost 40% greater by the end of this century compared to the period from 1963 to 2023, according to research published in Nature Communications.
The inverse relationship between the El Niño‒Southern Oscillation (ENSO) and the Indian summer monsoon had appeared to weaken since the early 1980s. Researchers found that this historical weakening was driven by two unusual events in 1983 and 1997. Greenhouse warming actually strengthened the link between 1902 and 2023 and is projected to continue strengthening it, though confidence in the projection remains relatively low.
Monsoon mechanics
Researchers attributed variations in climate model projections of ENSO–monsoon links to differences in ENSO-induced Walker circulation anomalies, which operate primarily through zonal wind feedback processes. Using multiple observational datasets to constrain these atmospheric dynamics, the study detailed how the link intensifies over time.
Even if the degree of El Niño-induced sea surface warming stays unchanged, tropical precipitation becomes more responsive to ocean warming. This response shifts Walker circulation anomalies further eastward and increases air subsidence over the Indian subcontinent, which reduces monsoon precipitation. The shifts increase risks for food security and intensify hydrological extremes in India.
Yutong Zhao, Tao Wang, Chaoyi Xu, and Tandong Yao conducted the research at the Chinese Academy of Sciences and Peking University. The study received support from the National Natural Science Foundation of China under grant numbers 42425106 and 42401139, along with the Second Tibetan Plateau Scientific Expedition and Research Programme under grant number 2024QZKK0301.
