The deadly toll of Europe's heatwaves: At least 70,000 people died across the continent because of hot weather in summer 2022 - including 3,855 in Britain

Sweltering heatwaves in the summer of 2022 caused the deaths of at least 70,000 people, scientists say. 

That's more than 10 per cent higher than previous estimates suggested. 

Scientists from the Barcelona Institute for Global Health have increased the death toll estimate for 2022's heatwave from 62,862 to 70,066.

With heat-related deaths in the UK having been estimated at 3,496, a 10.28 per cent increase would put the true figure as high as 3,855 deaths over the summer. 

The data also shows that the summer of 2022 was exceptionally deadly, with deaths almost doubling the number estimated each year between 1998 and 2004.

To calculate the excess deaths caused by heat, the researchers applied an epidemiological model to temperature and mortality data.

By comparing increases in the number of deaths with the intensity of the heat, scientists were able to arrive at reasonably accurate figures for the number of excess deaths caused by spikes in temperature.

A previous study of weekly temperature data found that an abnormally hot month from mid-July to mid-August was responsible for 38,881 deaths in Europe. 

In just a week between 18 and 24 July, when temperatures were at their hottest, the scientists estimated that there were 11,637 heat-related deaths.

However, this new research shows that aggregated data such as weekly figures can underestimate the number of deaths caused by heat. 

Lead researcher Joan Ballester Claramunt says that the larger the time over which data is aggregated, the more the results underestimate total deaths. 

'In general,' says Mr Claramunt, 'we do not find models based on monthly aggregated data useful for estimating the short-term effects of ambient temperatures.'

Between 1998 and 2004, models using weekly temperature data underestimated the number of deaths caused by heat each year by 21.56 per cent. 

Likewise, when the researchers compared estimates for Spain produced with either weekly or daily data, they found that heat-related deaths in 2022 were underestimated by six per cent. 

However, Mr Claramunt points out that the difference between estimates tends to be lower when the spikes in heat are at their most extreme. 

'It is important to note that the differences were very small during periods of extreme cold and heat, such as the summer of 2003, when the underestimation by the weekly data model was only 4.62%,' Mr Claramunt explains.  

Last summer was the hottest and deadliest ever recorded in the UK as temperatures peaked at over 40°C (104°F) for the first time ever.

The Met Office reported that 2022 was an extreme outlier in a run of 250 years of data as the country was struck by a 'brief but unprecedented heat wave'.

Temperatures up to 102°F (39°C) were recorded as far north as North Yorkshire as records were broken across the country for maximum and daily minimum temperatures.

Worryingly experts noted that, unlike the heatwaves of 2003, the extreme weather of 2022 could not be considered exceptional and was in line with ongoing trends. 

Study author Mr Claramunt said at the time: 'The temperatures recorded in the summer of 2022 cannot be considered exceptional, in the sense that they could have been predicted by following the temperature series of previous years, and that they show that warming has accelerated over the last decade.'

Recent research has found that, while the effects on some extreme weather events are 'overestimated', climate change's link to heat waves was supported by unequivocal evidence. 

Heatwaves are becoming more likely and more intense across the globe with human-caused climate change the most likely reason.

In general, a heatwave that previously had a 1 in 10 chance of occurring is now nearly three times as likely, and peaks at temperatures around 1 degree Celsius higher than it would have been without climate change.