Start with the number, because it is hard to know what else to do with it: 451,000. That is the estimate, from researchers at the University of Chicago’s Climate Impact Lab, of the additional heat-related deaths this year’s super El Niño will cause worldwide between now and February 2027. It is a projection, not a promise. But projections this size are worth understanding, and the interesting part of this one is not the total. It is the address list.
The mechanism, quickly. An El Niño starts in the tropical Pacific, where sea-surface temperatures in the central Pacific are already running about 5.4 degrees Fahrenheit (3 degrees Celsius) above average, per Gizmodo’s account of the lab’s report — beyond anything recorded during any previous El Niño, and still strengthening, according to Euronews. Warm water dumps heat into the atmosphere; global temperatures rise — the lab projects 2.1 degrees Fahrenheit (1.2 degrees Celsius) above normal for the coming months, with a 44% increase in extremely hot days — and rainfall gets relocated around the map. Nobody can switch it off. The only question is who is standing in front of it.
To turn weather into deaths, Michael Greenstone and his colleagues Tamma Carleton, Genevieve Maricle and Emily Grover-Kopec took the European Centre for Medium-Range Weather Forecasts’ seasonal forecast and fed it through peer-reviewed research on how temperature changes death rates in 24,378 regions, adjusting for local climate, local risk and local ability to cope. The death figures are measured against the 1996–2025 average for the same months.
The map that comes out of that machine is dominated by the Sahel, the dry belt between the Sahara and the southern savannas: about 3.05 million square kilometers from the Atlantic to the Red Sea, cutting through Mauritania, Mali, Niger, Chad, Nigeria, Sudan, Senegal and Eritrea. Four of those countries take the worst of the heat from September through February, with 66,800 projected additional deaths between them. Nearly half — 31,400 — fall on Nigeria, the most populous of the group at 237.5 million people, making it the projected world leader in El Niño fatalities. Greenstone’s interview with The Conversation puts Sudan next at 17,500, then Niger at 10,000 and Chad at 8,000; the write-up Gizmodo cites has Sudan at 17,600 and places Indonesia second globally with 19,300. The United States makes the top 20, with 3,500 projected deaths. And if El Niño lingers into June or July 2027, all of these numbers go up.
Why Nigeria and not, say, Phoenix? Because the same temperature kills different numbers of people depending on the wiring. The lab’s research generally finds more heat deaths in poor regions than in wealthy ones at similar temperatures. More than 60% of Nigerians were estimated to live below the national poverty line in 2025, and even homes with electricity suffer power cuts. Sudan is at war; businesses and power supplies have been damaged, and an estimated 57% of people were living in extreme poverty in 2025. In Niger 41% lived below the national poverty line in 2021, and in Chad 44.8% did in 2022; as of 2024, only 21% of Nigeriens and 13% of Chadians had electricity at all. Most households, in other words, cannot run a fan, let alone an air conditioner.
The lab has a statistic for how large that gap is. During spells of high heat, the extra electricity used per person in low-income countries would be enough to run one LED light bulb for four months. Not an air conditioner. A light bulb. Eighteen countries sit in this trap of extreme heat plus no means of cooling, most of them in northern sub-Saharan Africa, including Niger, Mali, Burkina Faso and Chad. As the world warms, wealthier countries will simply buy more air conditioning; hotter, poorer countries do not have that option.
The report’s second message is that the deaths are not all locked in. The lab maintains what it calls an Adaptation Inventory — a searchable map of climate adaptation measures that actually work — and its winners for the next six months are unglamorous: early-warning systems paired with heat action plans; targeted health outreach to older people, small children and the chronically ill; government-run cooling centers and hydration stations in high-risk areas; protections for outdoor workers during the most dangerous hours; and hospitals in the Sahel hiring staff and laying in supplies now, ahead of the projected heat spikes. “With these timelines in mind, there is time to reduce the numbers of lives lost by tens of thousands with targeted action,” the report says, claiming to give decision-makers “the clarity and specificity to act before, not after, the deaths occur.”
Governments are at least twitching. Outgoing UN Secretary-General António Guterres said in early September that “El Niño is being supersized before our eyes,” and the World Meteorological Organization has mounted what Euronews describes as an unprecedented mobilization. India has already seen below-normal monsoon rainfall, southern Africa faces increased drought risk, and California Governor Gavin Newsom has preemptively declared a state of emergency for potential flooding, landslides and winter storms. The UK has pledged up to £15 million (€17 million) for everything from vaccinating livestock before droughts to paying farmers before harvests fail. In Bangkok, meanwhile, nonstop rain since Thursday — almost 300mm (11.8 inches), the governor said — prompted authorities to declare all 50 districts of the Thai capital a disaster zone, according to Al Jazeera.
Zoom out, and the event looks less like weather than like a preview. A typical El Niño adds roughly 0.2°C to global average temperatures; the burning of fossil fuels has already added about 1.3°C to 1.4°C above pre-industrial levels, and a study published in August found El Niños are now 36% stronger than before the industrial era, a trend its researchers tied to human-caused warming. The lab’s report calls this El Niño a “postcard from the future” — temperatures that could become increasingly common without adaptation investment. Davide Faranda, research director at France’s CNRS and an IPCC lead author, put the long-run version to Euronews: “We cannot eliminate El Niño through climate mitigation, but we can reduce the extent to which climate change makes its consequences more severe.” The Pacific will run its cycle no matter what anyone does. The 451,000, on the other hand, is to some degree still a policy choice — which is the optimistic reading, and also the indictment.