Climate change and its impacts on glaciers and permafrost in the Alps

Climate change in the European Alps during the 20th century has been characterized by increases in minimum temperatures of about 2 degrees C, a more modest increase in maximum temperatures, little trend in precipitation data, and a general decrease of sunshine duration through to the mid-1980s. Temperature increase has been most intense in the 1940s, followed by the 1980s. The warming experienced since the early 1980s, while synchronous with the global warming, is of far greater amplitude and reaches close to 1 degrees C for this ensemble average and up to 2 degrees C for individual sites. Such changes caused pronounced effects in the glacial and periglacial belts. Since the middle of the past century-the end of the Little Ice Age-the glacierization of the European Alps has lost about 30 to 40% in surface area and around half its original volume. The estimated total glacier volume in the European Alps was some 130 km(3) for the mid-1970s, but strongly negative mass balances have caused an additional loss of about 10 to 20% of this remaining ice volume since 1980. Periglacial permafrost in the Alps today occupies an area comparable to the glacierized area and must have been affected as well, but its secular evolution is much less well known. Simulations of high-resolution climatologies for double-CO2 situations using regional climate models (RCM) with a 20-km horizontal grid give generally higher winter temperatures, a more marked increase in summer temperatures, indications that temperature increases more at higher elevations than at lower altitudes, and higher/ more intense precipitation in winter, but much dryer conditions in summer. Under such conditions, the Alps would lose major parts of their glacier cover within decades, warming of cold firn areas at high altitudes could become pronounced and lower limits of permafrost occurrence in the Alps could rise by several hundred meters. Pronounced disequilibria could result, in the water cycle, in mass wasting processes, and in sediment flux as well as in growth conditions of vegetation. For those directly involved with such changes, the main challenge would be to adapt to high and accelerating rates of environment evolution. Empirical knowledge would have to be replaced increasingly by improved process understanding, especially concerning runoff formation and slope stability. In view of the uncertainties involved with future projections, highest priority should be given to appropriate monitoring programs.