Laternser, M. and Schneebeli, M. 2003. Long-term snow climate trends of the Swiss Alps (1931-99). International Journal of Climatology 23: 733-750.
The authors report that a succession of exceptionally warm and dry winters in the Alps (1987-88 to 1989-90) led to widespread discussions about the consequences of snow shortage and the reasons for it; and they say that the IPCC (1990) "argued that the first clear signs of man-made climate change towards a warmer atmosphere were now visible in the Alpine region." Consequently, after acquiring an additional decade of data on the topic, they decided to reevaluate the IPCC's strident contention.
What was done
The authors selected a large number of consistent long-term snow series from across the Swiss Alps, including the adjacent forelands, after which they evaluated trends of average snow depth, duration of snow cover, and the number of snowfall days and heavy snowfall events.
What was learned
High altitudes showed only slight changes in snow parameters over the period of study, but at mid and low altitudes, in the words of the authors, "the mean snow depth, the duration of continuous snow cover and the number of snowfall days in the Swiss Alps all show very similar trends during the observation period 1931-99: a gradual increase until the early 1980s followed by a statistically significant decrease towards the end of the century," although even the most extreme decrease observed during the 1990s "still remains within the bounds of natural variability." In addition, they note that "a literature review confirms that, throughout the temperate and subpolar Northern Hemisphere, a similar general pattern of temporal snow variations occurred during the 20th century."
With respect to heavy snowfall events, the Swiss scientists report "there is virtually no long-term trend visible," which tends to confirm the conclusion of Schneebeli et al. (1998) that "no trend can be found for heavy snowfalls causing direct-action avalanches." Consequently, they say that "in mountain regions, problems encountered with heavy snowfalls, such as disastrous avalanches, blocked mountain roads or ski-field closures, remained on a similar level throughout the observation period."
What it means
The authors findings clearly suggest that the IPCC (1990) was both too hasty and too adamant in its pronouncements on the subject of changing snow characteristics. Even after acquiring an additional decade of data, Laternser and Schneebeli say it will yet take "forthcoming years and decades [our italics]" to "reveal as to whether we will veer toward an excessively warm greenhouse climate with increasingly less snow or the usual climate variability will proceed as it has done for hundreds of years with more or less pronounced anomalies." We agree. There is as yet no compelling reason to believe what the climate models and their political promoters are saying about the nature of earth's future climate, much less its current climate.
IPCC. 1990. Scientific Assessment of Climate Change. First Assessment Report of Working Group I., Intergovernmental Panel on Climate Change. WMO/UNEP, Geneva, Switzerland.
Schneebeli, M., Laternser, M. Fohn, P. and Ammann, W. 1998. Wechselwirkungen zwischen Klima, Lawinen und technischen Massnahmen. Vdf-Hochschulverlag, Zurich, Switzerland.
Reviewed 28 April 2004