Climate scientists now estimate that El Niño could kill 451,000 people worldwide between June and February 2027.
Michael Greenstone, 56, co-founder of the Climate Impact Lab and a University of Chicago economics professor, released the figure in a new report last week. The projection covers heat-related deaths across a nine-month span that began this summer and runs through early next year. Greenstone, who holds the Milton Friedman Distinguished Service Professor chair, said the research marks a grim breakthrough in connecting temperature forecasts directly to mortality outcomes.
“We have long been able to predict the impacts of temperatures on crops, and now we can predict their impact on the worst outcome—death,” he said in a statement accompanying the report. “The result is that we now can estimate that 451,000 people may die in the coming months due to El Niño.”
The death toll would be 65 times larger than the 6,800 people believed dead or missing from recent flash floods in Nepal. Greenstone stressed that the statistic represents individual human lives rather than an abstract figure.
“This is such a large number that it can be numbing, but it is made up of parents and children, grandparents and neighbors, people going to work, caring for families, and living their lives,” he continued. “This report allows decision-makers to see exactly where emergency actions can be taken now to save tens of thousands of lives in the coming months.”
Developing nations in Africa’s Sahel region face the most severe impacts. Nigeria alone is projected to suffer roughly half of the region’s 66,800 additional deaths through February. Sudan is expected to see 17,500 heat deaths, Niger 10,000, and Chad 8,000 during the same period.
Tamma Carleton, Faculty Head of Research for the Climate Impact Lab and an Assistant Professor at UC Berkeley, warned against relying solely on emergency responses without longer-term planning. She co-authored the report with Greenstone.
“Increasing emergency response and better targeting our efforts can save many lives this year,” Carleton said. “But 20 years from now, once today’s extreme temperatures become the new normal, we don’t want to be in a constant state of emergency.”
Carleton added that immediate investment in preparation tools could reduce future tolls: “We need to mobilize resources now to design, deploy, and evaluate the preparation and planning tools that will save lives in the years ahead.”
The current El Niño follows a record-breaking 2023-2024 event that pushed global temperatures to unprecedented highs. El Niño patterns, first recognized centuries ago by South American fishermen, typically emerge every two to seven years. Scientists say this cycle will be even stronger than the last.
In the United States, California Gov. Gavin Newsom has already declared a state of emergency in anticipation of the weather pattern’s effects. Residents there have been urged to stockpile staples including rice and pasta.
The Climate Impact Lab report arrives as global emergency response systems face mounting pressure from compounding climate disasters. The researchers emphasized that targeted interventions in the highest-risk regions could substantially reduce the projected death count before the nine-month window closes.
