1. Department of Geography; University of Zurich; Zurich Switzerland
2. Oeschger Centre for Climate Change Research and Department of Geography; University of Bern; Bern Switzerland
3. Now at Swedish Meteorological and Hydrological Institute; Norrköping Sweden
4. Department of Geosciences; University of Fribourg; Fribourg Switzerland
5. Department of Earth Sciences; Uppsala University; Uppsala Sweden