Trends in indices for extremes in daily temperature and precipitation in central and western Europe, 1901-99

We analyse 20th century trends in six indices for precipitation extremes and four indices for temperature extremes, calculated from daily observational data for European stations. The indices chosen reflect rather moderate extremes. Most of the ∼80 stations used are situated in central and western Europe; therefore, results mainly refer to this region. Trends are calculated over 1901–99, 1921–99, 1901–50 and 1946–99. Two different trend estimators are used, and significance is assessed with a bootstrap technique. We find that: Significant increasing precipitation trends over the 20th century dominate in winter for both average precipitation intensity and moderately strong events. Simultaneously, the length of dry spells generally increased insignificantly. There are few significant trends of any sign for precipitation indices in summer, but there are insignificant drying trends over Scandinavia and wetting trends over central and western Europe for 1921–99. The length of dry spells in summer generally increased insignificantly. Both the warm and cold tails of the temperature distribution in winter warmed over the entire 20th century. Notably low values in the cold tail for daily Tmax and Tmin occurred in the early 1940s, leading to strong but insignificant negative trends for 1901–50, whereas little change occurred before 1940. Warming of winters during 1946–99 occurred in both the warm and cold tails for both Tmax and Tmin, with the largest warming in the cold tail for Tmin. The warm tail of daily Tmin (and to a smaller extent Tmax) in summer warmed significantly during the past century. There is more evidence for summer warming in the first half of the century compared with the second half. During 1946–99, the warm tail of daily Tmax in summer was generally warming while the cold tail was cooling (both insignificantly). More digitized daily observational data from various European sub-regions are needed to permit a spatially more extensive analysis of changes in climate extremes over the last century. Copyright © 2005 Royal Meteorological Society