Reality Check

EPA

Following the heatwave in August 2003, statisticians linked 2,091 deaths to the unusually high temperatures.

Heat isn't a cause that appears on anyone's death certificate. So how do we measure the death-toll of a heatwave?

Excess mortality figures are arrived at by comparing the death rate in a given period to the average for that period in previous years.

We don't know that heat was a factor in all of those deaths - just that there were that many more deaths than the average for the same period over the previous five years.

Death rates in summer tend to be relatively stable so this was an unusual spike.

Researchers used this 2,091 figure as a baseline when calculating how many more people could die in heatwaves by 2050. They estimated there would be an increase of about 250%, giving the 7,000 figure.

The Office for National Statistics doesn't regularly look at how many deaths are linked to hot weather, but it does regularly publish excess winter mortality data. More people die in winter than in summer because of cold weather and higher rates of infectious illnesses such as flu. In the winter of 2016-17, there were 34,300 excess deaths compared with the death rate in the summer.