Scientists Warn Record-Hot El Niño Could Kill 451,000 People

A potential Super El Niño could affect far more than outdoor temperatures.

A troubling forecast from the Climate Impact Lab estimates that the extreme weather pattern could contribute to as many as 451,000 additional heat-related deaths by February 2027.

The analysis, prepared by researchers from the University of Chicago, projects 44% more extremely hot days than would typically occur in an average year. Sea surface temperatures have already climbed to 3.07°C—about 5.5°F—matching the record reached during the 2015–16 El Niño. Scientists say the developing event could ultimately become the strongest in roughly 1,000 years.

The potential human cost is severe. Of the more than 400,000 excess deaths predicted between June and February, approximately 239,000 could occur within the next six months, according to the study.

The final toll could rise further if El Niño persists into spring. Researchers warn that unusually high temperatures and heat-related fatalities could continue into the following summer as the event’s effects linger.

The largest share of the projected deaths is expected in the Global South. Nigeria has the highest estimated national total, with roughly 31,000 additional heat-related deaths forecast between September and February compared with a typical year.

Indonesia is projected to record about 19,300 excess deaths, followed by Sudan with an estimated 17,600. Across the arid Sahel region—including Niger, Chad, Nigeria and Sudan—the model forecasts approximately 66,800 heat-related deaths over the next six months.

The Philippines, Vietnam, Thailand and Cambodia could collectively experience another 19,400 heat-related deaths, the projections indicate.

To estimate the impact of extreme heat, the researchers combined temperature forecasts with historical mortality data from more than 24,000 regions around the world.

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The team compared its mortality projections with the same months during an average year, using the period from 1996 through 2025 as the baseline.

The researchers described the current conditions as a warning of what may lie ahead. Without effective adaptation, they said, figures that now appear extraordinary could become increasingly common within just a few decades.

Scientists are calling for immediate preparation in regions facing the greatest risk. Some areas already rely on heat-alert systems, improved forecasting and broader access to cooling technology, but the study notes that those protections are not consistently available worldwide.

“We need to build the evidence base now for what works, and then invest in preparations and planning,” the researchers wrote. They added that protecting communities from a hotter future will require detailed, regularly updated knowledge about which measures save lives across different climates, regions and health systems.

The authors stress that their figures are projections rather than confirmed outcomes. At the same time, public debate over climate-related warnings and the language used to describe future global warming has grown increasingly contentious.

In October, Bill Gates said rising global temperatures “will not lead to humanity’s demise,” a notably less catastrophic assessment than some of his earlier comments about climate change.

Even so, El Niño has already been linked to a range of disruptive conditions, including wildfires in Indonesia, weaker monsoon rainfall in India and drought across parts of Central America.

In Central America, the dry conditions have contributed to crop and livestock losses while reducing water levels in the Panama Canal, where the shortage has helped slow maritime trade.