El Niño Projected to Cause 451,000 Additional Heat-Related Deaths Worldwide

Between June 2026 and February 2027, the current El Niño climate pattern is projected to cause 451,000 additional heat-related deaths worldwide, according to a September 23 report from the Climate Impact Lab. The forecast models the human toll of a weather phenomenon that has already pushed global land temperatures significantly above normal. By mapping the expected temperature anomalies, the researchers anticipate the climate event will generate 44 percent more extremely hot days than a typical year.[1][3]

El Niño occurs when ocean-surface temperatures in the equatorial Pacific warm significantly, releasing heat into the atmosphere and altering global air and sea currents. While meteorologists have long tracked how these shifts trigger droughts, wildfires, and floods, the Climate Impact Lab research isolates the direct physiological impact of the resulting temperature spikes. The 451,000 projected fatalities represent deaths caused strictly by excessive heat, arriving on top of the casualties expected from other climate-driven disasters.[1][3]

To generate the forecast, the research consortium—which includes scientists from the University of Chicago and the Rhodium Group—combined seasonal temperature forecasts with localized estimates of how heat affects mortality. The team analyzed the relationship between temperature and additional heat deaths across more than 24,000 regions worldwide. They then applied those historical connections to the specific temperature anomalies expected during the current El Niño cycle.[2][5]

The resulting data reveals a stark geographic divide, with the projected fatalities heavily concentrated in the Global South. In these regions, baseline temperatures are already high, and resources for adaptation—such as widespread air conditioning and reliable water supplies—are often limited. The African Sahel faces the steepest toll, with tens of thousands of additional deaths expected over the next six months as the climate pattern peaks.[1][2]

Within the Sahel, nearly half of those fatalities—31,320—are projected to occur in Nigeria. The surrounding nations are also forecast to suffer heavy losses, with 17,430 additional heat deaths expected in Sudan, 9,900 in Niger, and 7,953 in Chad, according to regional breakdowns. The researchers noted that in places that are already hot and relatively poor, an increase of just a couple of degrees becomes exponentially more dangerous to the human body.[1][2][3]

Southeast Asia represents the second major cluster of projected mortality. Researchers anticipate nearly 40,000 excess deaths across the region, split between Indonesia, which is forecast to see 19,251 deaths, and a group of nations including the Philippines and Vietnam. Elsewhere, India is forecast to see 15,670 additional deaths, while Brazil is expected to record 13,271.[1][3]

The projected global toll '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,' Michael Greenstone, a co-founder of the Climate Impact Lab, said in a statement. Greenstone, an economics professor at the University of Chicago, emphasized that while scientists have long predicted the impacts of temperatures on crops, they can now predict the impact on human survival.[1][2]

To contextualize the scale of the threat, researchers estimate that since the El Niño pattern began in June, excess heat has already caused more than 200,000 deaths. With the climate pattern expected to persist, hundreds of thousands more remain at risk in the coming months as the phenomenon reaches its peak.[5]

The researchers released the findings ahead of formal peer review, stating that the urgency of the forecast required immediate publication. Emily Grover-Kopec, a director at the Rhodium Group who worked on the report, noted the goal is to allow governments and humanitarian organizations to deploy targeted interventions. 'We’re hoping this information is actionable, that decisions can be made to move resources ahead of time,' Grover-Kopec told Smithsonian Magazine.[5]

By pinpointing the exact regions facing the highest mortality risks, the data provides a map for where specific emergency actions can be taken. The researchers emphasized that the projected deaths are not inevitable. Implementing early warning systems, opening cooling centers, establishing hydration stations, and enforcing protections for outdoor workers could prevent tens of thousands of the projected fatalities before the El Niño pattern subsides next spring.[1][3][5]