Summer Heat Waves in Western Europe, Their Past Change and Future Projections P. M. Della-Marta 1 and M. Beniston 2 Abstract Summer heat waves and extremely hot temperatures are a serious threat to society, the environment and the economy of Europe. In this chapter we present an overview of selected recent literature which looks specifically at European heat waves and extreme temperature events, their past change and expected future change from 1880 to 2100. Della-Marta et al. (2007b) show that over the period 1880–2005 the length of summer heat waves over western Europe has doubled and the frequency of hot days has almost tripled. These changes are seen in the probability density func- tion (PDF) of western European daily summer maximum temperature (DSMT) as a significant change in the mean (+1.6 ± 0.4°C) and variance (+6 ± 2%). The relatively small change in variance over the last 126 years can explain approximately 40% of the change in hot days. We see a continuation of the observed trends in the future regional projections. Beniston et al. (2007) show that regional surface warming causes the frequency, intensity and duration of heat waves to increase over Europe. By the end of the 21st century, countries in central Europe will experience the same number of hot days as are currently experienced in southern Europe. The intensity of extreme temperatures increases more rapidly than the intensity of more moderate tem- peratures over the continental interior due to increases in temperature variability. 1 Introduction Extreme weather and climate events have a large impact on our society and environment (IPCC 2001). Heat waves are especially devastating for societies that are not used to coping with such extremes. The 1995 Chicago heat wave was 1 Climate Services, Federal Office of Meteorology and Climatology MeteoSwiss, Krähbühlstrasse 58, Postfach 514, CH-8044 Zürich paul.della-marta@meteoswiss.ch 2 Chair for Climate Research, University of Geneva, Site de Battelle/D, 7 Route de Drize, CH-1227 Carouge/Geneva, Switzerland Martin.Beniston@unige.ch S. Brönnimann et al. (eds.), Climate Variability and Extremes During the Past 100 Years. 235 © Springer 2008 Bronnimann_Ch15.indd 235 Bronnimann_Ch15.indd 235 11/1/2007 7:04:24 PM 11/1/2007 7:04:24 PM