Measuring Heat’s Deadly Toll

One research team analysed the human cost of the 2022 summer temperatures in Europe, while another provided a clear path to mitigating the effects of urban heat islands

is the continent experiencing the greatest warming, up to 1°C more than the global average

Rising temperatures due to climate change are already killing thousands of people around the world. For example, the European office Eurostat reported a high excess mortality during the summer of 2022, which was the hottest summer ever recorded in Europe, characterised by an intense series of heat waves.

Counting heat-related deaths in Europe

But how many of the deaths in Europe that summer were actually due to heat? To answer this question, Joan Ballester and his team combed through temperature and mortality data for 823 regions in 35 European countries. They used this data to build epidemiological models and predict heat-related mortality for each region and each week of the summer period (30 May to 4 September 2022).

Their first estimate was already a staggering 62,862 premature deaths due to heat in Europe. After correcting their model to use daily rather than weekly temperature data, the number rose to over 70,000 excess deaths. The countries with the highest heat-related mortality rates were Italy, Greece and Spain, with 295, 280 and 237 deaths per million inhabitants, respectively. In some countries such as France, Switzerland, Italy and Spain, temperatures were more than 2ºC above the average values for 1991-2020.

The fact that more than 70,000 people in Europe died of heat stress in 2022 despite active prevention plans in many countries, suggests that the current adaptation strategies are not sufficient

says Hicham Achebak, last author of the study.


70,000 PEOPLE
Died from heat in Europe in 2022
Fighting heat in cities

Cities are particularly vulnerable to rising temperatures. High population densities, heat-absorbing surfaces such as asphalt, and less vegetation lead to a phenomenon known as the urban heat island effect, where urban areas experience higher temperatures than the surrounding countryside. Unfortunately, this trend is expected to worsen in the coming decades.

Under the leadership of Mark Nieuwenhuijsen, director of the Urban Planning, Environment and Health Initiative, an international team conducted a study to assess the health impact of urban heat islands in 93 European cities. They analysed temperature, mortality and tree cover data from these cities for the summer of 2015. They found that cities were on average 1.5ºC warmer than the surrounding rural areas. This increase in urban temperatures contributed to 6,700 premature deaths, accounting for 4% of all summer deaths. Remarkably, the study suggests that a third of these deaths could be prevented by ensuring that trees cover 30% of urban space. However, the researchers emphasise that it is not just a question of increasing the number of trees in the city, but also how they are distributed.

Our aim is to raise awareness among local decision-makers of the benefits of integrating green spaces into every neighbourhood to promote more sustainable, resilient and healthy urban environments

says Nieuwenhuijsen.


Tree cover


Reduction in urban temperatures


Premature heat-related deaths prevented


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