In the face of the very likely increase of more frequent, longer lasting and more intense heat waves in Europe (IPCC 2013), heat waves and the resulting heat impacts have become a more relevant topic in the last years. The heat wave in 2003 with temperatures around 40°C even in Germany dramatically showed the health impact heat waves can have: approximately 70,0000 people were killed across Europe in consequence of the heat (Robine et al. 2008). Due to the urban heat island in particular the population in urban agglomerations is exposed to high temperatures and at risk of negative health impacts. Prevention and adaptation measures to avoid heat health impacts are thus relevant in urban adaptation strategies to climate change.
To develop appropriate adaptation measures, it is important to consider how urban citizens experience heat and how they cope with the heat in their everyday life. For this reason, researchers of the KIT investigated the subjective heat stress in the city of Karlsruhe within the Helmholtz Climate Initiative REKLIM. In contrast to biometeorological indices that combine measurements of temperature and humidity to measures of physiological heat stress, “subjective heat stress” refers to the individual and self-reported assessment of respondents to what extent they experience high summer temperature as stress. The questionnaire survey was carried out together with the South German Climate Office and the municipal senior citizens’ office of the City of Karlsruhe in summer 2013 immediately after a heat wave with temperatures above 35°C. In total, 428 respondents aged 17-94 living or working in Karlsruhe participated in the survey. The results of the studies have been published in the journal Natural Hazards and Earth System Sciences.
All in all, the study participants on average experienced rather high subjective heat stress in the preceeding heat wave. The subjective heat stress varied for different contexts in daily life. Heat was experienced to a lower degree as stress at home than while being at work (Fig 1). At work, individuals not only have to sustain heat physically, but have to meet the performance requirements of professional working life even when they suffer from concentration problems, weakness and tiredness due to sleep disorders from the heat. Next to excessive sweating, these health impairments were mostly mentioned by the respondents (Fig 2).
The respondents implemented a large variety of measures cope with the heat and to lower their heat stress (Fig 3). They often used simple behavior measures (drinking plenty fluids, wearing lighter clothers) and available structural measures to keep the indoor temperature at a tolerable level such as airing and shading. Measures that change daily routines themselves and that thus require certain flexibility, such as shifting activities or work to other times of the day, were less often applied.
In an analysis of the 323 participants with residence in Karlsruhe the determinants for subjective heat stress were investigated. Two factors evolved as major factors for subjective heat stress in general, at home and at work: the health impairments from the heat and the feeling of being helplessly exposed to the heat. For subjective heat stress at home additionally factors of the residential building and the urban environment are relevant: a lower thermal loading of the residential district, living in an apartment in the ground floor or the lower floors, heat protection elements such as window shutters or blinds for roof windows), a energetic building standard, and additional recreational elements outside that are directly accessible from home (garden, terrasse, backyard) lower the subjective heat stress.
For adaptation to climate change the results underline that structural measures such as heat protection and energetic refurbishent of residential buildings are measures that are already now effective in reducing subjective heat stress. In addition the measures implemented to cope with the heat show that coping with heat is performed by the respondents within the constraints and structures of their daily life. Finally the high subjective heat stress at work underpins that developing adaptation strategies for future heat waves is not only a topic for the domain of private and family life at home in residential buildings, but also for the domain of working life.
Publications
Kunz-Plapp, T., J. Hackenbruch, J.W. Schipper, 2016: Factors of subjective heat stress of urban citizens in contexts of everyday life, Natural Hazards and Earth Systems Sciences, 16, 977-994, doi:10.5194/nhess-16-977-2016.
IPCC Intergovernmental Panel on Climate Change: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., Qin, D., Plattner, G.-K., Tignor, M., Allen, S.K., Boschung, J., Nauels, A., Xia, Y., Bex, V., and Midgley, P.M. (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 1535 pp, doi:10.1017/CBO9781107415324, 2013.
Robine, J.-M., Cheung, S. L. K., Le Roya, S., van Oyen, H., Griffiths, C., Michel, J.-P. and Herrmann, F. R.: Death toll exceeded 70,000 in Europe during the summer of 2003, C. R. Biologies 331, 331, 171–178, doi:10.1016/j.crvi.2007.12.001, 2008.
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