Record-breaking hot spells in May and June have been linked to more than 2,700 deaths across England and Wales, according to a new analysis by scientists from Imperial College London, the Met Office, and the London School of Hygiene and Tropical Medicine. The research directly attributes a significant proportion of these fatalities to human-driven climate change, which intensified the heat.
How the study calculated the death toll
The team examined two specific heatwave periods: nine days in May when temperatures reached 35.1°C, and 11 days in June when they exceeded 37°C. Using detailed weather records and health statistics, they compared the actual mortality figures with a modelled scenario of a climate not warmed by human activity. Their calculations suggest that around 550 deaths occurred during the May heatwave, while approximately 2,200 deaths were linked to the June event.
The researchers found that warming caused by human activity accounted for 59% of the deaths in May and 38% in June. They warn that normal summer daytime temperatures are now regularly up to 4°C higher than in the past, making such heatwaves more dangerous.
Health impacts of extreme heat
Dr Mark McCarthy from the Met Office described the two heatwaves as 'exceptional'. He noted that heatwave thresholds are rarely met in May, but this year daytime temperatures were widely 15°C above the average for the month in England and Wales, while night-time temperature records were also set. The June heatwave, which saw red warnings for extreme heat issued on consecutive days, was notable for its humidity as well as heat.
“They were extreme heatwaves for the UK, and for all parts of western Europe, and they're particularly exceptional for the timing and how early in the year they occurred. This combination of extreme daytime heat, high humidity and hot nights all act to really contribute and increase the impact these heatwaves have on our infrastructure, on transport, agriculture and particularly on our health and wellbeing,” he said.
Call for greater preparedness
Dr Clair Barnes from Imperial College London said: “Every time we have a heatwave, our news is filled with reporters at swimming pools, images of people eating ice cream and sunbathers on beaches. We all love the sun, but people need to be aware that we are now seeing dangerous climate-change-fuelled heat that is claiming lives, disrupting schools and hospitals and shutting down transport and infrastructure.”
Government advisers have warned that the UK remains unprepared for these shifts, suggesting most homes could overheat by mid-century. They are calling for official limits on workplace temperatures and better cooling systems in hospitals and schools.
Professor Lea Berrang Ford from the UK Health Security Agency (UKHSA) said the modelled estimates offered a crucial insight into the potential health consequences of prolonged hot weather. “While they are not a measure of observed mortality, they help illustrate the scale of risk associated with extreme heat and the growing threat climate change poses to our wellbeing,” she said.
