Another week, another extravagant claim for climatic doom goes unchallenged. Speaking on the Today programme on Wednesday morning, Dale Vince – the founder of Electrocity and donor to both Don’t Stop Oil and the Labour party – asserted: ‘40,000 people across Europe died from excess heat last summer. That’s part of the climate crisis. People are dying, people are being made homeless, whole countries are flooding.’

Whole countries flooding? It is unclear which countries Vince claims have flooded in their entirety, but a claim by a Pakistan government minster that a third of that country was under water in floods last summer has been thoroughly debunked by UN satellite data, which shows that the area affected by floods at some point last August was around 8 per cent.

It seems odd to pick out the excess deaths during heatwave weeks and to blame them wholly on hot weather

But what about the claim that 40,000 people across Europe died from excess heat in the summer of 2022? This would appear to derive from a report published in January by reinsurance firm Gallagher Re, which made the claim: ‘Preliminary estimates based on Gallagher Re analysis of country-level excess mortality statistics, which determined totals by subtracting from recent decadal averages and Covid-19 spikes, suggested that as many as or more than 40,000 excess deaths may be attributed to the extreme heat across the continent during the summer months.’

I did ask Gallagher Re to explain its methodology, and its chief scientific officer replied: ‘We developed a methodology that looked at country level mortality by week or month and compared to 20 years of pre-Covid excess mortality levels. We then had a separate baseline used for 2020-2021 which was enhanced by Covid-year averages. In each case we subtracted vs the average with the assumption that heat was the primary cause of the increase. The base datasets used were governmental health agencies.’

To assume that, when we have just been through a pandemic, with its massive disruption to healthcare (about which more in a moment), an increase in deaths relative to the five year average is due to the heat, is somewhat questionable.

A more commonly-reported figure for deaths from the European heatwave of 2022 is around 20,000, reported, for example, by Reuters last November. This is arrived at by adding up the totals for ‘excess deaths’ reported by individual countries: such as 3,271 by the ONS, 10,420 by France, 4,655 by Spain, 4,500 by Germany.

But there are several problems with figures for ‘excess deaths’. They are arrived at simply by totting up the deaths in a given period and comparing them with the average number of deaths in recent years.

In the ONS’s case, it compared deaths during five periods of hot weather between June and August with the simple five year average for deaths (excluding 2020). This gave a figure of 3,271 excess deaths.

This figure, however, does not make any adjustment for population growth nor for change in the age profile of the population. Given that the number of over 70s is growing, you would expect more deaths year on year. Moreover, the ONS’s analysis makes no allowance for the fact that deaths were running well above the five year average for much of last year, beginning in April, long before the heatwave.

Several causes for this have been suggested, such as long waiting times for A&E and a hangover of deaths from the pandemic of people who failed to seek medical help during the lockdowns. It thus seems odd to pick out the excess deaths during heatwave weeks and to blame them wholly on hot weather. Interestingly, excess deaths among the under 70s during 2022’s heatwave periods were negative, to the tune of 1,749.

There is a further problem in doing as Dale Vince does and taking deaths from excess heat and attributing them all to the ‘climate crisis’. That asserts that no-one would be dying from the heat were it not for climate change. But of course there have always been heatwaves, even if less intense than last year’s, and they have always caused, or accelerated, deaths.

For a comprehensive analysis of deaths from extreme temperatures, a Monash University study in 2021 concluded that around five million people a year succumb to this cause. Yet more than 90 per cent of them are caused by extreme cold rather than extreme heat. Moreover, deaths from extreme cold are falling at a greater rate (0.51 per cent between 2000 and 2019) than deaths from extreme heat are rising (0.26 per cent over the same period). For the moment at least, climate change could be said to be saving lives from extreme temperatures.