A powerful Super El Niño could lead to up to 451,000 additional heat-related deaths worldwide between June this year and the end of February 2027, compared with an average year, according to a report released on Wednesday by Climate Impact Lab (CIL).
The global research collaboration said record global heat associated with the current El Niño could increase the number of extremely hot days by 44 per cent. The report, titled “451,000 Lives at Risk: Where Action Can Save Lives During a Super El Niño”, described the current event as “a postcard from the future”.
Researchers examined the relationship between temperature and excess mortality across 24,378 regions, taking account of local climates and population vulnerability. They combined those findings with temperature forecasts to estimate excess deaths caused by El Niño-related heat, using average temperatures from 1996 to 2025 as a benchmark.
The study’s methodology is due to be published in a peer-reviewed journal.
Climate Impact Lab recommended that emergency heat-response measures be prioritised in high-risk areas over the coming months. Its Adaptation Inventory includes heatwave warnings, increased staffing at health facilities during the hottest periods, cooling centres for people seeking shelter and protections for outdoor workers.
“This report gives decision-makers a precise view of where emergency action over the next few months can save thousands of lives,” said Michael Greenstone, an economist at the University of Chicago and co-founder of CIL.
El Niño is a natural climate cycle marked by sea-surface temperatures in the central and eastern equatorial Pacific rising by at least 0.5 degrees Celsius above normal. Scientists and meteorologists classify an El Niño as “super” when sea-surface temperatures remain 2 degrees Celsius or more above normal for several months.
The current El Niño reached 2.7 degrees Celsius last month and could rise to as much as 4 degrees Celsius when it peaks between November and December, according to some forecasts.
Akshay Deoras, a senior researcher at the National Centre for Atmospheric Science and the Department of Meteorology at the University of Reading, said the development of El Niño depends heavily on how the atmosphere and ocean behave.
“At the beginning of the year, winds generally blow towards Indonesia and accumulate warm water there,” Deoras told Al Jazeera. “But sometimes the winds weaken or the wind pattern reverses. Strong winds then blow from Indonesia, transporting a huge amount of warm water from one place to another.”
That warm water moves towards the eastern equatorial Pacific, creating El Niño conditions. Deoras said strong winds from Indonesia during the spring helped transport large volumes of warm water, resulting in a Super El Niño this year.
Adam Scaife, head of long-range forecasting at the UK Met Office, said scientists were still assessing whether the impact of this year’s El Niño would be proportional to its intensity.
“We are already seeing the expected impacts around the world,” Scaife said.
The UK Met Office said historical evidence shows El Niño can significantly alter global rainfall patterns. Areas that typically receive less rainfall during El Niño include parts of central and northern South America, the western Pacific and regions influenced by the Indian summer monsoon.
Drought risks could increase in South Africa and other regions, while tropical cyclone activity in the Atlantic Ocean tends to decline during El Niño. The UK Met Office said no hurricane had yet been observed this year.
Disruptions to rainfall could have serious consequences for global food supplies by damaging agriculture and altering natural food production and harvest seasons.
Deoras said El Niño “pours a huge amount of heat into the atmosphere”, strengthening extreme rainfall and weather events. A Super El Niño increases not only the frequency of such events but also their intensity and severity, he said.
“It is generally expected that there will be more extreme weather events worldwide over the coming months and, unfortunately, many people could die as a result,” Deoras said.
Friederike Otto, a professor of climate science at Imperial College London, said climate change has made El Niño’s global effects more severe.
“Global temperatures may rise further in the coming months because of El Niño, and the impacts of extreme weather may emerge,” Otto said. “Climate change will intensify these effects because the additional heat accumulating due to fossil-fuel emissions is pushing global temperatures higher.”
Otto said El Niño is a natural phenomenon that comes and goes, unlike climate change. “Unless faster action is taken globally to move away from fossil fuels, the climate change situation will only get worse,” she said.
Climate Impact Lab said countries in the Global South would bear the greatest burden of excess heat. Nigeria is projected to record the highest number of additional heat-related deaths, at 31,400, followed by Indonesia with 19,300 and Sudan with 17,600.
The African Sahel region, including Nigeria, Sudan, Niger and Chad, could record 66,800 additional heat-related deaths. The Philippines, Vietnam, Thailand and Cambodia could collectively see 19,400 additional deaths, researchers said.
The death toll could rise if El Niño persists into next year, particularly during the summer months in key Northern Hemisphere regions including India and Pakistan.
Tom Burke, co-founder and director of climate-change think tank E3G, said the Global South would be disproportionately affected because countries with weaker institutions may struggle to manage the additional pressure caused by El Niño.
“The poorer a country is, generally the weaker its institutions are,” Burke told Al Jazeera. Countries in the Global North, by contrast, have institutions such as fire services and health systems to manage such pressures, he said.
Deoras cautioned against assuming that El Niño’s impacts would be greater only in the Southern Hemisphere. “We have not seen this kind of El Niño in the past,” he said, adding that unexpected conditions and extreme weather could also affect the Northern Hemisphere.
Burke said the projected figure of 451,000 deaths may be conservative because it accounts only for heat-related fatalities. Fires and floods linked to El Niño could increase deaths, he said, while conflicts such as the US-Israel and Iran wars could affect food inflation and contribute to deaths that are difficult to capture statistically.
Deoras described the report’s figures as estimates and said he was sceptical about their regional distribution. He cited the projection of more than 15,000 excess deaths in India by February 2027, saying it did not appear highly credible because India would not be in the summer season when deadly dry heatwaves strike.
Deoras said there was nevertheless a strong possibility that, over the next 12 months, the impacts would be visible in deaths as well as damage to property, infrastructure and economies.