With climate change, the risk of avalanches is rising in altitude

The observation seems to go without saying: low and medium mountain areas experience less avalanches due to global warming and, of course, to a lesser amount of snow. But, explain the authors of a study published on October 25 in the American scientific journal PNAS, if the “Mountain areas are particularly affected by global warming, the impacts on avalanches are still little known”.

Hence the work carried out jointly by researchers from the National Research Institute for Agriculture, Food and the Environment (Inrae), Météo France, CNRS, and the universities of Geneva, Grenoble and Haute-Alsace who studied avalanche evolution in the Vosges mountains over nearly two and a half centuries. The result of their research is enlightening: avalanches go up in altitude, their season shortens and their number, in this mountainous massif, has been greatly reduced.

Insufficient snowpack

The interest of these unpublished data lies in the lessons that they provide for all mountainous areas. Over the period studied, with the temperature increase of 1.5 ° C between the middle of the XIXe and the beginning of the XXe century, at the end of what scientists call the “little ice age”, it was noted a reduction by seven in the number of avalanches in the Vosges mountains, which culminates at 1,424 meters. “We studied a sample of around 700 avalanches, or a small part of the approximately 14,000 that would have been triggered during this period, by working by corridor [200 couloirs d’avalanches ont été étudiés]. From 0.74 avalanche per corridor and per year during the years 1770 to 1864, we went to 0.09 between 1910 and 2013, that is to say an avalanche every ten years or so ”, explains Florie Giacona, historian by training, who works on natural risks in the mountains at INRAE. This meticulous work and the collection of the necessary data would not have been possible without the collaboration between historians (with the study of written archives and iconographic documents), climatologists and specialists in statistical modeling.

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This reduced number does not mean that there would be less risk of avalanches in the mountains. “This does not mean that there cannot still be avalanches at lower altitudes, but below 800 meters, over the last decades, there is hardly any more activity. avalancheuse ‘, specifies Florie Giacona. Explanation: the snowpack is no longer large enough to trigger an avalanche.

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With climate change, the risk of avalanches is rising in altitude