Climate Impact Lab attributes 450,000 deaths to El Nino heat through February

The 450,000 is two numbers stacked. Of them, 240,000 fall inside the six-month forecast window running from September to February ^[3]. The rest, around 210,000, is attribution applied to weather that has already happened, covering the months since the current El Nino began in June ^[5][4]. The retrospective share does not depend on a forecast being right. The forecast share does, and Christopher Callahan at Indiana University Bloomington says the 240,000 rests on it ^[26]. Emily Grover-Kopec says the European Centre for Medium-Range Weather Forecasts outlook her team used sits in the middle of other forecasts, making it a moderate view of the heat ahead ^[27].

Underneath both halves is the observed relationship between temperature and excess deaths, which is U-shaped: mortality climbs in extreme cold and again in extreme heat ^[6]. Its exact shape is local, depending on whether people and infrastructure are adapted to heat extremes and whether households can afford air conditioning ^[6]. The 2022 study the report builds on fitted that curve region by region, using historical data going back decades where it exists and extrapolating from similar regions where it does not ^[7].

Africa takes the largest share, with more than 30,000 extra deaths estimated in Nigeria alone over the next six months ^[9]. Indonesia is put at 19,000, India at 16,000 and Brazil at 13,000 across the same window ^[10]. Those four countries come to about 78,000, roughly a third of the 240,000 ^[11].

"We're hoping this information is actionable, that decisions can be made to move resources ahead of time," said Grover-Kopec, who is at the Rhodium Group ^[17]. On the wave she expects after February she said: "I fully expect these numbers to get bigger, unfortunately" ^[15].

"I do find these results plausible," said Callahan ^[22]. He said El Nino will bring very high temperatures to much of the world, and that the relationship between heat and mortality is consistent and reliable across the world ^[23]. He recently used a similar approach to put the death toll of Europe's June heatwave at 20,000 ^[24]. Reported excess deaths attributable to heat in Europe stand at 35,000 so far, over a longer period of the summer ^[25], so the two figures do not test each other directly ^[31].

Raquel Nunes at the University of Warwick said the value of the report is not in the total. "The most important message is not the absolute number itself, but what can still be done to reduce preventable harm," she said ^[29], adding that the report "is best viewed as a call to strengthen anticipatory governance, preparedness and targeted adaptation measures, particularly for at-risk and vulnerable populations" ^[30].