Global warming caused 60 per cent of heat-related deaths in Switzerland in 2022

Climate change intensifies heat, leading to a significant rise in the heat-related burden on health. Around 60 per cent of the more than 600 heat-related deaths in Switzerland in the summer of 2022 can be attributed to human-induced global warming. This is shown by a study led by the University of Bern.

Read the original media release here. (in German)

The figures for the hot summer of 2022 are striking: in Geneva, for example, temperatures exceeded 30 degrees on 41 days, in Sion on as many as 49 days and in Lugano on 38. In recent times, Switzerland has only experienced a more pronounced heatwave in the legendary summer of 2003. The high temperatures had serious consequences for health. Between June and August 2022, 623 people died as a result of the heat – 3.5 per cent of all deaths in that period. This is the conclusion of a study led by the University of Bern and just published in the journal “Environmental Research Letters”. According to the publication, there were three times as many heat-related deaths in the summer of 2022 as the average for the years 2009 to 2017.

Global warming caused more than 370 additional deaths #

The study not only documents the excess mortality attributable to heat; as one of the first studies worldwide, it also quantifies the share of global warming in heat-related deaths: around 60 per cent. “Without human-induced climate change, more than 370 people in Switzerland would not have died from the effects of heat in the summer of 2022,” says Dr Ana Vicedo-Cabrera, first author of the study from the Institute of Social and Preventive Medicine (ISPM) and the Oeschger Centre for Climate Change Research (OCCR) at the University of Bern. Researchers from ETH Zurich, the Swiss Tropical and Public Health Institute in Basel (Swiss TPH) and the University of Basel were also involved in the study.

Studies that calculate the contribution of climate change to the observed effects of heat are rare. In 2021, an international study coordinated by the University of Bern and the London School of Hygiene & Tropical Medicine attracted great international attention: for 732 cities in 43 countries worldwide, it showed for the first time the actual contribution of human-induced climate change to heat-related deaths between 1991 and 2018. Apart from the Swiss study, there is not a single study on the hot summer of 2022, which affected the whole of Europe. For its calculations, the team led by epidemiologist Ana Vicedo-Cabrera relied on so-called attribution studies. These use established statistical methods and climate simulations to estimate the share of human-induced climate change in the observed burden on health.

Urban populations suffer particularly from the heat #

The study on heat-related deaths reaches different results depending on the region: the urban cantons of Geneva, Vaud, Basel-Stadt and Zurich were particularly affected. Not all cantons and cities are equally prepared to deal with heat. In Basel and Zurich, for example, there is no systematic and comprehensive public health strategy to combat heat. In western Switzerland and Ticino, by contrast, heat action plans were drawn up following the hot summer of 2003. They include awareness campaigns and behavioural recommendations, among other things. “Last summer, these heat action plans prevented an even higher heat-related mortality rate, for example in the cantons of Geneva and Vaud, where temperatures were particularly high,” explains Ana Vicedo-Cabrera.

The epidemiologist also recommends that the authorities optimise existing action plans for protection against heat. As her study states: “At current rates of warming, a hot summer like 2022 will become an average summer within the coming decades. Without effective adaptation strategies, the continued ageing of the population and the (re-)emergence of infectious diseases could lead to even greater health impacts.” The study authors also call for stronger climate protection and advocate “ambitious mitigation strategies.”

Women are more affected – especially older women #

The study, entitled “The footprint of human-induced climate change on heat-related deaths in the summer of 2022 in Switzerland”, analysed the effects of the hot summer not only in terms of regional differences, but also by age and sex. It showed that almost 90 per cent of heat-related deaths involved people over the age of 65. The number of deaths was generally higher among women than among men. Of all subgroups, older women had the highest mortality rate.

According to Ana Vicedo-Cabrera, it has not yet been scientifically established why older women are particularly sensitive to heat. Hypotheses include physiological causes, for example related to the menopause. Another factor could be that older women usually lead a more active lifestyle than men and are therefore more exposed to high temperatures.