Climate change is intensifying the heat, which is leading to a significant increase in heat-related health problems. Around 60 per cent of the more than 600 heat-related deaths in Switzerland in summer 2022 can be attributed to man-made global warming. This is shown by a study led by the University of Bern.
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The figures for the hot summer of 2022 are impressive: in Geneva, for example, it was over 30 degrees on 41 days, in Sion it was even 49 days and in Lugano 38. Switzerland has only experienced a more pronounced heatwave in recent times in the legendary summer of 2003. The high temperatures had serious consequences for health. Between June and August 2022, 623 people died due to the heat, accounting for 3.5 per cent of all deaths during this period. This is the conclusion of a study led by the University of Bern that has just been published in the journal "Environmental Research Letters". According to the publication, there were three times more heat-related deaths in summer 2022 than the average for the years 2009 to 2017.
Global warming caused more than 370 additional deaths
The study not only provides evidence of excess mortality due to heat, it is also one of the first studies worldwide to quantify the share of global warming in heat-related deaths: it is around 60 per cent. "Without man-made climate change, more than 370 people in Switzerland would not have died in the summer of 2022 as a result of the heat," says Dr Ana Vicedo-Cabrera, lead author of the study from the Institute of Social and Preventive Medicine (ISPM) and the Oeschger Centre for Climate 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, international attention was focussed on a international studycoordinated by the University of Bern and the London School of Hygiene & Tropical Medicine, which showed for the first time the actual contribution of man-made climate change to heat-related deaths between 1991 and 2018 for 732 cities in 43 countries worldwide. Apart from the study from Switzerland, there is not a single study for the heatwave summer of 2022, which affected the whole of Europe. The team led by epidemiologist Ana Vicedo-Cabrera based its calculations on attribution studies. These use established statistical methods and climate simulations to estimate the contribution of man-made climate change to the observed health burden.
Urban population suffers particularly from the heat
The study on heat-related deaths comes to different conclusions depending on the region: The urban cantons of Geneva, Vaud, Basel-Stadt and Zurich were particularly affected. Not all cantons and cities are equally equipped 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, on the other hand, heat action plans have already been drawn up following the heatwave summer of 2003. They include awareness-raising campaigns and behavioural recommendations. "These heat action plans prevented an even higher heat-related mortality rate last summer in the cantons of Geneva and Vaud, for example, where temperatures were particularly high," explains Ana Vicedo-Cabrera.
The epidemiologist also recommends that the authorities optimise existing heat protection plans. This is because, according to her study: "At current warming rates, a hot summer like 2022 will become an average summer in the coming decades. Without effective adaptation strategies, the progressive ageing of the population and the (re)emergence of infectious diseases could lead to even greater health impacts." The authors of the study are also in favour of increased climate protection and advocate "ambitious mitigation strategies".
Women are more affected - especially senior citizens
The study entitled "The impact of human-induced climate change on heat-related deaths in the summer of 2022 in Switzerland" analysed the effects of the summer heatwave not only in terms of regional differences, but also in relation to age and gender. This showed that almost 90 per cent of heat-related deaths affected people over the age of 65. The number of deaths was generally higher among women than among men. Among all subgroups, older women had the highest mortality rate.
According to Ana Vicedo-Cabrera, it is not yet scientifically clear why older women are particularly sensitive to heat. Hypotheses include physiological causes, for example associated with the menopause. The fact that older women usually lead a more active lifestyle than men and are therefore more exposed to high temperatures could also play a role.
Publication details
Dr Ana Maria Vicedo-Cabrera Institute of Social and Preventive Medicine (ISPM) and Oeschger Centre for Climate Research (OCCR), University of Bern. Picture: zvg
Ana M. Vicedo-Cabrera, Evan de Schrijver, Dominik L. Schumacher, Martina S. Ragettli, Erich M. Fischer, Sonia I. Seneviratne: The footprint of human-induced climate change on heat-related deaths in the summer of 2022 in Switzerland. 4 July 2023, Environmental Research Letters.
doi: https://doi.org/10.1088/1748-9326/ace0d0
The Oeschger Centre for Climate Research
The Oeschger Center for Climate Change Research (OCCR) is one of the strategic centers of the University of Bern. It brings together researchers from 14 institutes and four faculties. The OCCR conducts interdisciplinary research at the cutting edge of climate change research. The Oeschger Center was founded in 2007 and bears the name of Hans Oeschger (1927-1998), a pioneer of modern climate research, who worked in Bern.
Institute for Social and Preventive Medicine (ISPM)
Since 1971, for 50 years, the Institute of Social and Preventive Medicine (ISPM) at the University of Bern has been committed to improving the health and well-being of individuals and society. Through high-quality research in the fields of prevention, social medicine, epidemiology, biostatistics and public health and together with numerous national and international partners, the ISPM stands for "Health for All".
In addition to cutting-edge research, the ISPM is dedicated to training the next generation of epidemiologists, public health researchers and physicians. The ISPM is actively involved in university teaching programmes for students of medicine, pharmacology, biomedical engineering and biomedicine.
04.07.2023