The report combines seasonal temperature forecasts with localized mortality models for more than 24,000 regions, comparing expected deaths under El Niño‑driven heat with a baseline of temperatures observed over the past three decades.
Researchers estimate that global land temperatures during the event could be about 1.2 °C (2.1 °F) higher than normal, producing roughly 44% more extremely hot days than in a typical year.
The Sahel region of Africa is projected to suffer the highest toll, with an estimated 66,800 extra deaths, while South and Southeast Asia and parts of Latin America also face steep increases: the study forecasts 19,400 additional deaths across the Philippines, Vietnam, Thailand and Cambodia, 19,300 in Indonesia, 15,800 in India, and 13,300 in Brazil.
Co‑founder of the Climate Impact Lab and study co‑author Michael Greenstone said the danger is greatest in already hot, relatively poor areas, noting that “if you’re already in a hot place, the extra couple of degrees are going to be much more dangerous.” He added that wealthier regions tend to have better access to air‑conditioning, reliable water supplies and functional health systems, which can mitigate mortality.
Greenstone warned that the heat risk will likely persist beyond the expected end of El Niño in February, with fallout potentially felt into the following summer, underscoring the event as a preview of conditions climate change could make common in two decades.
The report recommends a suite of preventive actions, including heat‑warning systems, cooling centres, hydration stations, protections for outdoor workers, expanded hospital capacity and targeted outreach to the elderly and other vulnerable groups. It also calls for anticipatory financing so governments can mobilize resources before peak heat periods.
Abhiyant Tiwari, a heat expert at NRDC India who was not involved in the study, said the projections should serve as a call to action rather than alarm, emphasizing that “the real measure of our preparedness is not how many heat warnings we issue, but how effectively we protect people and reduce preventable deaths.”
The study places the current El Niño in the broader context of a warming planet, noting that the temperature spikes it generates mirror conditions that could become routine as global warming progresses, highlighting the urgency for climate‑resilient public‑health planning.