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Snow (Europe) -- Summary
What does the future hold for the ski industry of Europe?  A news item in the 3 Dec 2003 Independent.co.uk begins with the claim that "many of Europe's most popular skiing resorts face extinction because global warming is making snowfall increasingly unreliable, the United Nations said yesterday."  Is this assessment correct?  Some studies we have recently reviewed in CO2 Science Magazine provide an important perspective on the issue.

Laternser and Schneebeli (2003) note that a succession of exceptionally warm and dry winters in the Alps in the late 1980s led to widespread discussions about the consequences of snow shortage and the reasons behind it; and they report 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."  Stimulated by this proclamation -- and after acquiring an additional decade of pertinent data that included a large number of long-term snow series from the Swiss Alps and adjacent forelands -- they evaluated historical trends of average snow depth, duration of snow cover, and the number of snowfall days and heavy snowfall events in a reevaluation of the IPCC's strident contention.  So what did they find?

High altitudes showed only slight changes in snow parameters over the study period, but at mid and low altitudes, in the words of Laternser and Schneebeli, "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, according to them, "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' study also revealed little net change.  "There is," as they describe it, "virtually no long-term trend visible," which finding is in harmony with the conclusion of Schneebeli et al. (1998) that "no trend can be found for heavy snowfalls causing direct-action avalanches."  Hence, they conclude 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," just as problems associated with light snowfalls remained essentially unchanged.

Laternser and Schneebeli's findings clearly demonstrate that the IPCC was both too hasty and too adamant in its 1990 pronouncements on what was happening snow-wise in the Alps and why.  In fact, even after acquiring an additional decade of data, they conclude it will yet take "forthcoming years and decades" 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."

In a similar study, Falarz (2002) analyzed seasonal snow cover duration and maximum snow depth data for Cracow and Zakopane in southern Poland for the period 1895/96-1998/99; and, once again, the story was pretty much the same: "no statistically significant trends" for either of the parameters studied.  Falarz thus concluded that "the global warming found in the 20th century (IPCC, 1996) and the increasing tendency of air temperature in Europe in particular in winter (Schonwiese and Rapp, 1997), as well as the 'local' trends of the same features (Trepinska and Kowanetz, 1997; Wibig, 2000; e.g. the increase of mean air temperature in Cracow of 1.7C/100 yr in January), seem to have no clear reflection in snow cover conditions in southern Poland in the 20th century."

In a much broader-based study, Ye and Ellison (2003) report using data from "the Historical Soviet Daily Snow Depth CD version II, compiled and quality-controlled by the National Snow and Ice Data Center" to determine the first and last dates of continuous snow cover over northern Eurasia from approximately 43 to 73N, as well as the lengths of the spring and fall transitional snowfall seasons, when the ground is less than fully covered by snow.  From this exercise, they determined that (1) "the length of continuous snow cover has increased about 4 days/decade over northern European Russia," and (2) "the transitional snowfall season has increased in both spring and fall."  Hence, there was an increase in the lengths of all three snow-cover seasons: the continuous snow-cover season and the fall and spring transitional snow-cover seasons.

In light of these several findings, it would appear that skiers in Europe are not about to run out of snow anytime soon if ever!

References
Falarz, M.  2002.  Long-term variability in reconstructed and observed snow cover over the last 100 winter seasons in Cracow and Zakopane (southern Poland).  Climate Research 19: 247-256.

IPCC.  1990.  Scientific Assessment of Climate Change.  First Assessment Report of Working Group I., Intergovernmental Panel on Climate Change.  WMO/UNEP, Geneva, Switzerland.

IPCC.  1996.  Climate Change 1995: The Science of Climate Change.  Cambridge University Press, Cambridge, UK.

Laternser, M. and Schneebeli, M.  2003.  Long-term snow climate trends of the Swiss Alps (1931-99).  International Journal of Climatology 23: 733-750.

Schneebeli, M., Laternser, M. Fohn, P. and Ammann, W.  1998.  Wechselwirkungen zwischen Klima, Lawinen und technischen Massnahmen.  Vdf-Hochschulverlag, Zurich, Switzerland.

Schonwiese C.D. and Rapp, J.  1997.  Climate Trend Atlas of Europe Based on Observations 1891-1990.  Kluwer Academic Publishers, Dordrecht, The Netherlands.

Trepinska, J. and Kowanetz, L.  1997.  Many years' course of mean monthly values of air temperature in Cracow, 1792-1995.  In: Trepinska, J., Ed. Climate Fluctuations in Cracow (1792-1995).  Institute of Geography, Jagiellonien University, Cracow, Poland, pp. 99-130.

Wibig, J.  2000.  Temporal variability of the frequency of extreme temperature occurrence in Poland on the example of Zakopane and Lodz.  In: Obrebska-Starkel, B., Ed.  Images of Weather and Climate.  Prace Geograficzne of the Institute of Geography, Jagiellonien University, Cracow, Poland, pp. 215-222.

Ye, H. and Ellison, M.  2003.  Changes in transitional snowfall season length in northern Eurasia.  Geophysical Research Letters 30: 10.1029/2003GL016873.