July’s heatwave may have killed thousands of Britons

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LIKE MUCH of Europe, Britain has had a sweltering summer. The mercury rose to a record of 40.3°C (104.5°F) on July 19th, shattering the previous high of 38.7°C set in 2019. On August 9th the Met Office, Britain’s weather service, issued another “extreme heat” warning for the coming days. The country is not designed for hot weather. Just 2% of homes in England have air-conditioning and many homes, particularly flats, overheat because they have poor ventilation and are exposed to the sun. The results could be deadly. In England and Wales excess deaths—the number of people that have died compared with what has historically been expected—for the two weeks ending July 29th are 16% higher than usual, with 3,058 additional deaths registered over that period (see chart). A recent spike in excess deaths has also been reported in other parts of Europe. Is the heatwave responsible?

Previous experience does suggest that high temperatures are a big cause of deaths, because they exacerbate conditions such as respiratory issues or heart disease. The 2003 heatwave in Europe is associated with as many as 70,000 deaths across the continent. In Britain, when temperatures hit 38.7°C on July 25th 2019, deaths increased on the day and immediately afterwards, according to the Office for National Statistics. The so-called “harvesting effect”—people dying sooner than expected—then caused deaths to fall.

But separating cause and effect is difficult. Unless death certificates explicitly mention “heat” there is little way of knowing immediately whether that is the specific cause of death. But it is clear that covid-19—which has caused a large number of excess deaths in recent years—is not the cause. Although the number of deaths involving covid-19 in England and Wales for the past two weeks are twice what they were during the same two weeks of 2021, that only accounts for an additional 800 deaths. (And some of those deaths may also have been hastened by the heat.)

Using statistical modelling to disaggregate hot weather from other factors that lead to death, the Health Security Agency’s annual “heat mortality monitoring” report finds that heatwaves during 2020 and 2021 were associated with 2,095 deaths on average in England. That is twice the number observed between 2016 and 2019, possibly because covid makes people more vulnerable. Nine-in-ten heatwave deaths were among people aged over 65. It will be months before a definitive analysis of this year’s heatwave is available. As the climate warms, heat deaths will become more common unless people and homes adapt. The Climate Change Committee, an independent body scrutinising the British government’s climate policies, thinks that annual hot-weather deaths will increase from around 2,000 now to about 7,000 by the 2050s. ■