The Compagnie des guides de haute montagne de Chamonix is celebrating its 200th anniversary this year. Its members, who are going to Paris on Thursday, September 9, will not be able to climb the Eiffel Tower as initially planned. But some of their representatives will go to the National Assembly on Friday to discuss global warming. They have compiled their observations in a 60-page booklet, which they will provide to MPs. Because these professionals are the direct witnesses of these changes.
Guides have seen landscapes change for decades. Around Mont-Blanc, the retreat of the glaciers has accelerated since the 1990s. The high mountains have become grayer, more rocky. Partly more dangerous too: with increasing average temperatures, ice no longer plays its role of cement as much, explain these guides. The walls are more fragile, which favors rock collapses, especially in summer.
The vegetation is also starting to change. Work carried out with the Center for Research on Altitude Ecosystems has shown that for the past ten years, trees, especially ash and birch trees, have been budding a week earlier in the spring, as the snow melts earlier. The forests grow a little higher, because the trees seek to recover freshness. And in the mountain ranges, the number of plant species has doubled in the space of 150 years.
The snow cover has also evolved with global warming, the guides note. Winter 2021 was a bit exceptional, it snowed a lot. But overall, in villages located less than 2,500 meters above sea level, we have lost five weeks of snowfall compared to the 1970s. Ski resorts continue to lose one day of snow per year. Projections show that the majority of them will no longer be able to function in 2100, that is to say in 80 years. The image of Jean-Claude Dusse on his chairlift will soon no longer speak to many people. By 2100, the Alps could also lose 85 to 95% of their ice surface.
In 30 years, the snow will therefore hold a month less in the resorts, they will have to diversify their activities. But these changes will be felt especially in the summer. In 2050, in mid-mountain in the Mont-Blanc sector, there should be 20 to 30 heatwave days per year, compared to five to ten days today. But there will always be snow above 4000 meters, so the summit of Mont-Blanc will remain white.