A “formidable human adventure” which generally requires “great physical preparation”. Equipped with thick down jackets and bags weighing up to 7 kg, they climb the highest peak in Europe every two years to measure it. This year, 27 volunteers, including mountain guides and surveyors, embarked on the adventure. From this four-day expedition, they brought back a new rating unveiled this Wednesday: today, Mont-Blanc measures precisely 4,807.81 meters.
20 minutes spoke with Jean des Garets of the order of surveyors and in charge of this mission.
What lessons can be drawn from this new measure?
In 2001, the summit of Mont-Blanc measured 4,810.40 meters, today it stands at 4,807.81 meters. In 2017, he was at 4,808.72 meters. If we exclude the year 2019, exceptionally low and on which we had not communicated, we observe a drop in the summit of Mont-Blanc of the order of 10 centimeters on average per year for 20 years. Or an overall decrease of 2 meters. This decrease is noticeable, but we must keep in mind that 20 years is a very short period on the scale of our history. It doesn’t allow us to draw conclusions, just sketch a trend.
Why was the measurement recorded in 2019 exceptionally low? And why not take it into account?
The measurement made that year [4.806,03 mètres] out of the curve from a mathematical point of view. We did not communicate on it because we waited to see if this impressive drop was confirmed over time. This is not the case since since then the summit has regained 1.80 meters. In general, Mont-Blanc regains altitude during the summer. You have precipitation, basically snow that accumulates and turns to ice. When the glacier collapses, it raises the altitude. In 2019, we did not know if this exceptional drop was due to a severe climate crisis or if it was anecdotal. Today, it seems anecdotal.
The year 2019 was particularly hot, we can imagine that the recorded measurement, abnormally low, was linked to a severe lack of precipitation during the summer …
Surely it was. What is most intriguing, however, and perhaps most alarming, is that we had particularly terrible weather in 2021 all summer. And, we have these measures [inférieures à celles de 2017]. One would have expected that the summit of Mont-Blanc would be higher due to the precipitation.
Can we link this downward trend over the past 20 years to global warming?
Our job is not to interpret the results because we are not climatologists or glaciologists and therefore not competent to do so. But, if we look for an explanation, we can see one thing with certainty: the sea of ice rises 30 meters per year. If the glacier goes up, it is normal for the summit to decrease. Today, we observe that the summit tends to decrease but we cannot correlate it with global warming because the observation period is still too short.