A heatwave in 2022 may have caused more than 70,000 deaths across Europe, a study has found.
The Barcelona Institute for Global Health (ISGlobal) research revised earlier estimates of mortality associated with the record temperatures upwards from 62,862.
In the previous report, based on weekly temperature and mortality data in 823 regions in 35 European countries, the authors acknowledged that the use of weekly data would be expected to underestimate heat-related mortality.
The new study, published in The Lancet Regional Health – Europe, aimed to correct the errors from the use of aggregated data, such as weekly and monthly temperatures.
Akshay Deoras, a research scientist at the National Centre for Atmospheric Science and the Department of Meteorology at the University of Reading, told The National heatwaves can have various effects on people’s health.
High humidity can make someone feel hotter, while also making it harder for them to cool down. But heat exhaustion tends to be the main problem.
"We underestimate the impact of heat exhaustion because we may have some headache or dizziness but these things worsen quite rapidly and by the time you reach the hospital, it could be quite late. That’s one thing," he said.
"In addition to that, what really happened was many people were just caught unaware because the temperatures were extraordinary."
Data released in January found that 2022 was the hottest on record around the world, including large parts of Europe and the Middle East, the EU's Earth Observation Programme said.
It said the world’s warmest month was recorded in October, with an average surface air temperature across the planet of 15.3°C for the month.
This is 0.4°C warmer than the previous global record for October set in 2019 and 1.7°C warmer than the pre-industrial average, between 1850-1900.
The extraordinary temperatures were partly due to El Nino as it continued to develop in the equatorial Pacific.
In the new study, researchers aggregated daily temperatures and mortality records from 147 regions in 16 European countries. They then analysed and compared the estimates of heat- and cold-related mortality using daily, weekly, bi-weekly and monthly calculations.
The researchers found the models underestimated the effects of heat and cold as compared to the daily model.
For the period 1998-2004, the daily model estimated an annual cold and heat-related mortality rate of 290,104 and 39,434 premature deaths, while the weekly model underestimated these numbers by 8.56 per cent and 21.56 per cent.
Baitings Reservoir in England during the 2022 heatwave, and after heavy rainfall in 2023
The team used this framework to revise the rate attributed to the record temperatures experienced in 2022 in their earlier study.
According to the calculations made using the new methodological approach, that study underestimated the heat-related mortality by 10.28 per cent, which would mean that the actual number in 2022, estimated using the daily data model, was 70,066 deaths, and not 62,862 deaths as originally estimated.
“In general, we do not find models based on monthly aggregated data useful for estimating the short-term effects of ambient temperatures,” said Joan Ballester Claramunt, the ISGlobal researcher who leads the European Research Council’s EARLY-ADAPT project.
“However, models based on weekly data do offer sufficient precision in mortality estimates to be useful in real-time practice in epidemiological surveillance and to inform public policies such as, for example, the activation of emergency plans for reducing the impact of heatwaves and cold spells.”
Ms Claramunt said when daily data is not available, the use of weekly data, which are easily accessible for Europe in real-time, is a solution that can offer “a good approximation of the estimates obtained using the daily data model”.