UK deaths from extreme heat could soar under 2°C global warming

Temperature-related mortality, defined as when death is directly linked to climate temperature, could soar by up to 42 per cent in England and Wales during the hottest days of the year.

This means an increase from present-day levels of around 117 deaths per day, averaged over the 10 hottest days of the year, to around 166 deaths per day.

The current level of global warming – which is around 1.21°C – actually sees a slight decrease in temperature-related mortality in winter and a minimal net effect in summer for an overall slight decrease in temperature-related mortality.

The paper finds that the rate of increase particularly speeds up at 2°C of warming, with a much higher risk appearing beyond 2.5°C. The researchers say that 3°C warming could lead to a 75 per cent increase in mortality risk during heatwaves.

When plotted on a graph, the relationship between temperature and mortality is roughly u-shaped, meaning that at extremely high temperatures, which the population is not used to, the mortality risk increases sharply for each degree rise of daily mean temperature.

The rate in winter will continue to decrease, although this doesn’t take side effects of extreme weather – such as storms – into account.

UCL’s Dr Katty Huang, lead author on the paper, said: “The increase in mortality risk under current warming levels is mainly notable during heatwaves, but with further warming, we would see risk rise on average summer days in addition to escalating risks during heatwaves.

“What this means is that we shouldn’t expect past trends of impact per degree of warming to apply in the future. One degree of global warming beyond 2°C would have a much more severe impact on health in England and Wales than one degree warming from pre-industrial levels, with implications for how the NHS can cope.”

In England and Wales, temperature is associated with around 9 per cent of total population mortality, meaning that 9 per cent of all deaths during 2021 could be associated with the temperature. Most of those deaths are related to the side effects of cold weather.

In order to isolate the effects of global warming on mortality risk, the researchers looked at the potential impact for the current population, without taking into account future changes such as average age and health conditions.

Project lead Professor Andrew Charlton-Perez (University of Reading) said: “As the Intergovernmental Panel on Climate Change impacts report recently showed, it is increasingly common to examine how different levels of mean global warming raise the risk of significant harm to people and society. Our study shows that because death rates will go up significantly if countries experience very high temperatures, limiting the average global rise in temperatures is likely to have substantial benefits for the overall health of the population.”

Another study from last year found that more than a third of all deaths in which heat played a role in the period spanning 1991- 2018 were attributable to human-induced global warming.