The climate of the European Alps: Shift of very high resolution Koppen-Geiger climate zones 1800-2100

Although the European Alps are one of the most investigated regions worldwide, maps depicting climate change by means of climate classification are still not-existent. To contribute to this topic, a time series of very high resolution (30 arc-seconds) maps of the well-known Koppen-Geiger climate classification is presented. The maps cover the greater Alpine region located within the geographical domain of 4 to 19 degrees longitude and 43 to 49 degrees latitude. Gridded monthly data were selected to compile climate maps within this region. Observations for the period 1800-2010 were taken from the historical instrumental climatological surface time series of the greater Alpine region, HISTALP. Projected climate data for the period 2011-2100 were taken, as an example, from the Rossby Centre regional atmospheric model RCA4. Temperature fields were spatially disaggregated by applying the observed seasonal cycle of the environmental lapse rate. The main results of this study are, therefore, 366 observed and predicted (two scenarios) very high resolution Koppen-Geiger climate maps of the greater Alpine region covering the period 1800-2100. Digital data, as well as animated maps, showing the shift of the climate zones are provided on the following website http://koeppen-geiger.vu-wien.ac.at. Furthermore, the relationship between the Koppen-Geiger climate classification and the altitudinal belts of the Alps is demonstrated by calculating the boundaries of the climate zones, i.e. the deciduous forest line, the mixed forest line, the forest and tree line (timber line) and the snow line. The mean altitude of the potential timber line in the greater Alpine region, for example, was calculated to be 1730m by the end of the 19th century, 1880m by the end of the 20th century and to lie between 2120 and 2820 m by the end of the 21st century. The latter altitudes were projected for the greenhouse gas scenarios RCP 2.6 (best case) and RCP 8.5 (worst case). The altitude of the timber line (and the other boundaries of the altitudinal belts) is generally higher in the Western Alps, showing a clear west-east slope.