Mont Blanc, the highest peak in Western Europe, was measured in mid-September at 4,807.81 m, almost a meter less compared to the measurement made in 2017, according to a team of surveyors. experts, who warns, however, against any “hasty conclusion” related to climate change.
This new measurement finally corresponds to “the altitude that we found in our books (of geography) at school” and which has been learned by heart by generations of French schoolchildren, joked two of the members of the team. , Jean des Garets and Denis Borel, during a press point in Saint-Gervais-Les-Bains (Haute Savoie), at the foot of the white giant. A measure which itself dates back to the end of the 19th century.
The mission, led by the departmental chamber of surveyors of Haute Savoie, carried out in mid-September the ascent of the roof of Europe, to carry out surveys for three days, as it does every two years. for twenty years.
The 2021 expedition benefited from very favorable meteorological conditions, which allowed it to stay three hours at the top and to “raise in every nook and cranny” the summit cap. What “to reach a level of precision never achieved until then”, welcomed the surveyors.
However, we must “remain humble in front of this measure (…) We must not draw a hasty conclusion on measures which have been carried out only since the years 2001 with the precision that we show you today”, insisted Mr. Borel.
“We measure, we observe (…). We are there as sentinels of the environment”, he added. It is now up to “climatologists, glaciologists and other scientists to use all the data collected and put forward all the hypotheses to explain this phenomenon”.
The alpine arc is particularly affected by global warming. One of its most iconic glaciers, the Mer de Glace in the Mont-Blanc massif, has retreated about 2 kilometers since 1850, losing 120 meters in thickness over the past century.
Higher in summer than in winter
The objective of the regular measurements of Mont Blanc is to “model the ice sheet” and “to constitute and nourish a bank of precise and reliable data. These could be exploited by the experts and especially transmitted to the future generations”, have explained the surveyors.
The last measurement made public in 2017 reported an altitude of 4,808.72 m, itself down compared to those of previous years. The highest altitude was recorded in 2007 (4 810.90 m).
The figures attest to a decrease in the altitude of the summit by an “average” of 13 cm per year since 2001, noted the surveyors.
In reality, the numbers vary from time to time as the summit is “covered with a layer of ‘eternal snow’ which functions like a huge snowdrift and varies with altitude winds and precipitation.”
“Thus, since the dawn of time, the altitude of Mont Blanc oscillates continuously”. The “rocky” summit rises for its part “at 4,792 m”, underline the surveyors.
The measurement carried out in 2019 had however been kept “secret” because “exceptionally low” (4,806.03 m). Decision was taken at the time “to wait for the measure of 2021 for more educational and scientific explanations”.
It was a “measure a little out of time because it is true that there was not an enormous level of snow cover during this summer and that it is not at all significant compared to the previous years “, explained Mr. Borel.
The altitude of the summit also varies according to the seasons, Mont Blanc being a “dune complex” where the wind, more violent in winter, smooths the snow more than in summer. The summit is therefore higher at the end of the beautiful season than in the spring.