Heat is a specific issue in terms of climate change due to the negative effects on morbidity/mortality and on human health in general. Measures and recommendations against heat and its effects should reach affected people, helpers and decision makers and should, therefore, be communicated in an appropriate and easily understandable way.

Since the heat waves of summer 2003, countries and cities in Europe have started to develop emergency plans, including early warning systems3. With accurate and early weather forecasts, thorough knowledge of the effects of heat, and education and advice for citizens and targeted measures for vulnerable populations, as well as appropriate landscape and urban planning measures, the number of avoidable deaths should be reduced in future heat waves4,5.
The negative health consequences of heat waves have been both demonstrated and documented within mortality data for numerous countries, and have thus far been well studied by the international scientific community. During the well-known heat wave Atmosphere 2022, 13, 226. https://doi.org/10.3390/atmos13020226 https:// www.mdpi.com/journal/atmosphere Atmosphere 2022, 13, 226 2 of 6 in the summer of 2003, which hit large parts of Western and Central Europe in early August, around 7600 additional deaths were recorded in Germany6 and over 70,000 for Europe7-9. Not
only in the mortality data, but also in other data linked to health systems (i.e. hospital admissions and emergency room visits), the negative influence of heat waves is unambiguously palpable.
The following facts are known:
- Causes of death were heart stroke, cardiovascular disease, renal disease, and respiratory and metabolic disorders due to heat stress.
- The age group over 70 was most affected, especially in the case of women.
- People with chronic diseases were more at risk than others as a result of exacerbating inherent symptoms and vulnerabilities.
- Vulnerable, low-income populations(and their inherently associated living standards/conditions) were the most affected by the additional mortality rates. The extreme heat was higher in cities than elsewhere. Although
it is noted that increases in temperatures in peri-urban and rural areas were also witnessed, thus raising the need to apply caution in Urban Heat Island (UHI) comparative calculation methodologies as well.
The effects of heat on people’s health depend on three influencing factors: the duration, frequency and intensity to which people are exposed. For healthy people, slightly increased demands on thermoregulation, which are met by appropriate activity, behaviour, and sufficient fluid intake, reduce the threat and/or challenge presented to the biometeorological system. Heat puts strain on the cardiovascular system, and the body is exposed to higher stress in order to keep the core body temperature constant. For people with pre-existing health implications and problems, this additional stress can exacerbate numerous existing susceptibilities, which is why heat has also been shown to have a significant influence on other diseases, including respiratory diseases. If thermoregulation is restricted, disturbances of the water and electrolyte balance can occur, which can lead to life-threatening impairments of the cardiovascular system.
References
- Research Centre Human Biometeorology, Deutscher Wetterdienst, Stefan-Meier-Str. 4, 79104 Freiburg, Germany; [email protected]
- Institute of Earth and Environmental Sciences, Albert-Ludwigs-University Freiburg, 79085 Freiburg, Germany
- Matzarakis, A.; Laschewski, G.; Muthers, S. The Heat Health Warning System in Germany—Application and Warnings for 2005 to 2019. Atmosphere 2020, 11, 170. [CrossRef]
- Matzarakis, A. Hitzeereignisse: Charakteristika, Gesundheitsrelevanz und Anpassungsmöglichkeiten. Geographische Rundschau 2021, 2021, 8–13.
- Mücke, H.; Matzarakis, A. Klimawandel und Gesundheit. In Handbuch für Umweltmedizin. Ecomed, LandsbergamLech; Wichmann, E., Fromme, H., Eds.; Ecomed: Landsberg, Germany, 2017; pp. 1–38.
- An der Heiden, M.; Muthers, S.; Niemann, H.; Buchholz, U.; Grabenhenrich, L.; Matzarakis, A. Schatzung hitzebedingter Todesfalle in Deutschland zwischen 2001 und 2015. Bundesgesundheitsblatt Gesundh. Gesundh. 2019, 62, 571–579. [CrossRef] [PubMed]
- Robine, J.-M.; Cheung, S.L.; Le Roy, S.; Van Oyen, H.; Herrmann, F.R. Report on Excess Mortality in Europe during Summer 2003; EU Community Action Programme for Public Health, Grant Agreement: Brussels, Belgium, 2007; p. 28.
- Robine, J.M.; Cheung, S.L.; Le Roy, S.; Van Oyen, H.; Griffiths, C.; Michel, J.-P.; Herrmann, F.R. Death toll exceeded 70,000 in Europe during the summer of 2003. Comptes Rendus Biol. 2008, 331, 171–178. [CrossRef] [PubMed]
- Mücke, H.-G.; Matzarakis, A. Klimawandel und Gesundheit: Tipps für Sommerliche Hitze und Hitzewellen; Deutscher Wetterdienst: Offenbach, Germany, 2019. Available online: https://www.umweltbundesamt.de/publikationen/klimawandel-gesundheit-tipps- fuer-sommerliche-hitze (accessed on 10 January 2022)