Fewer and fewer snow days in the Alps

A study conducted by Padua University and by the National Research Council in Bologna, published in the scientific journal Nature Climate Change, shows that in the last twenty years the average number of days of snow on the Alps is 36 days lower than in the previous 600 years. From 1400 to the start of the 20th century, the number of days in the year when the Alps have snow-covered has been more or less constant, before gradually decreasing in the last century.

This is the first study of its kind to investigate so far back in time. The data on snowpack duration on the Alps go back a few decades at most. To go further back in time, researchers used tree rings in the trunks of juniper, a common high-altitude and enduring shrub. While buried by the snow, juniper does not grow and this makes it possible to estimate the duration of the snowpack year by year. The research group analysed the tree rings of a series of live and dead juniper shrubs in the Val Ventina, in the province of Sondrio. By comparing the information obtained with the available meteorological data, scientists managed to estimate the changes in the duration of the snowpack from the 15th century onwards.

Observation of the juniper rings also confirmed that in the winter between 1916 and 1917, the snowpack lasted for the longest period in the 20th century. There were 67 more snow days than the century average, which was 251 days per year. This happened during the First World War and these atypical weather conditions, which led to a particularly freezing winter, that thousands of soldiers died on the front between Italy and the Austro-Hungarian Empire.

«It has allowed us to understand that what we have experienced in recent years is something that has never happened before», concluded Marco Carrer from Padua University, the lead author of the study. Though the number of days with snow cover varies from year to year, in line with rainfall, the trend of the average values in the long term shows a correlation with the trend of average temperatures. This suggests that the reduction in snow days is linked to global warming caused by human activities.

On the Alps and the Apennines, snow has been rare due to weather conditions very similar to those of last winter, when temperatures were exceptionally mild and rainfall was low. As shown by the study by Padua University and the NRC, the lack of snow is more serious and frequent today than in the past, and at very low levels affects winter tourism, one of the sectors of the economy most sensitive to climate change. In the upcoming decades, many climate studies and models say that conditions will worsen: the increase in temperatures will shorten the skiing season and shift snowfall to higher altitudes.

This situation brings the future of skiing as a sport accessible to many people, into question. With global warming caused by greenhouse gas emissions, it is likely that global temperatures, including those in the European mountains, will continue to increase, making it more and more difficult and expensive to cover slopes with snow. One of the aspects of artificial snow that often goes overlooked is the consumption of water and electricity. One cubic metre of water can produce 2.5 cubic metres of snow on average. To cover one hectare – i.e. a stretch 1 km long and 10 metres wide – with at least 30 centimetres of snow, around one thousand cubic metres of water are needed, nearly half of the water contained in an Olympic swimming pool.