The climate drivers behind southwest India’s intensifying heat waves
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The periodic warming and cooling of ocean surface temperatures, a phenomenon known as the El Niño-Southern Oscillation (ENSO), contributes to intense heat waves in southwest India (SWI), a new study shows. ENSO involves sea surface temperature and atmospheric pressure changes over the tropical eastern Pacific ocean. Other major climatic modes have also contributed to the heat waves in the region.
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The study comes in the context of more frequent and intense heat waves in South Asia and elsewhere. There have been 223 heat wave events over the Indian subcontinent in the past few decades (1978-1999), causing approximately 5,500 deaths, the authors noted. India experienced about 24 days of heat waves in different parts of the country in 2024, its longest spell, as the head of India Meteorological Department (IMD), Mrutyunjay Mohapatra, noted in a recent interview. The country reeled under a third straight year of heat waves. Ironically, milder forms of heat waves claimed more lives during 2008-2019, another study showed.
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"Through regression methods, climate perturbation and causality analysis using reliable climate data sets, the authors bring out the relative roles of Indian, Pacific and Atlantic oceans in producing heat wave conditions over this region during peak summer months," summarised Vijayakumar P, assistant professor at the Department of Environmental Sciences, University of Kerala, who was not associated with this study.
"The study suggests that global warming-driven heat wave events are likely to increase in the ecosystem-rich southwest Indian region in the coming years," Vijayakumar told Mongabay India.
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