The analysis of state-of-the-art regional climate projections indicates a number of robust changes of the climate of the European Alps by the end of this century. Among these are a temperature increase in all seasons and at all elevations and a significant decrease in natural snow cover. Precipitation changes, however, are more subtle and subject to larger uncertainties. While annual precipitation sums are projected to remain rather constant until the end of the century, winter precipitation is projected to increase. Summer precipitation changes will most likely be negative, but increases are possible as well and are covered by the model uncertainty range. Precipitation extremes are expected to intensify in all seasons. The projected changes by the end of the century considerably depend on the greenhouse-gas scenario assumed, with the high-end RCP8.5 scenario being associated with the most prominent changes. Until the middle of the 21st century, however, it is projected that climate change in the Alpine area will only slightly depend on the specific emission scenario. These results indicate that harmful weather events in the Alpine area are likely to intensify in future. This particularly refers to extreme precipitation events, which can trigger flash floods and gravitational mass movements (debris flows, landslides) and lead to substantial damage. Convective precipitation extremes (thunderstorms) are additionally a threat to agriculture, forestry, and infrastructure, since they are often associated with strong wind gusts that cause windbreak in forests and with hail that causes damage in agriculture and infrastructure. Less spectacular but still very relevant is the effect of soil erosion on inclined arable land, caused by heavy precipitation. At the same time rising temperatures lead to longer vegetation periods, increased evapotranspiration, and subsequently to higher risk of droughts in the drier valleys of the Alps. Earlier snowmelt is expected to lead to a seasonal runoff shift in many catchments and the projected strong decrease of the natural snow cover will have an impact on tourism and, last but not least, on the cultural identity of many inhabitants of the Alpine area.
Andreas Gobiet and Sven Kotlarski
Wilfried Haeberli, Johannes Oerlemans, and Michael Zemp
Like many comparable mountain ranges at lower latitudes, the European Alps are increasingly losing their glaciers. Following roughly 10,000 years of limited climate and glacier variability, with a slight trend of increasing glacier sizes to Holocene maximum extents of the Little Ice Age, glaciers in the Alps started to generally retreat after 1850. Long-term observations with a monitoring network of unique density document this development. Strong acceleration of mass losses started to take place after 1980 as related to accelerating atmospheric temperature rise. Model calculations, using simple to high-complexity approaches and relating to individual glaciers as well as to large samples of glaciers, provide robust results concerning scenarios for the future: under the influence of greenhouse-gas forced global warming, glaciers in the Alps will largely disappear within the 21st century. Anticipating and modeling new landscapes and land-forming processes in de-glaciating areas is an emerging research field based on modeled glacier-bed topographies that are likely to become future surface topographies. Such analyses provide a knowledge basis to early planning of sustainable adaptation strategies, for example, concerning opportunities and risks related to the formation of glacial lakes in over-deepened parts of presently still ice-covered glacier beds.