Heat wave On the Alps
Climate varies naturally of course, but the current rate of global warming is unprecedented and cannot be explained by natural causes (solar activity, volcanic eruptions etc). Consequently scientists across the world attribute the current warming, with a 95% degree of certainty, to human activity (5th IPCC report, 2014).
Rise in temperatures
Warming has increased at a fast rate since the 1980's. In the past 30 years temperatures have jumped up 1°C in the French Northern Alps, which is enormous. In all, temperature have risen by 2° in the French Northern Alps compared to pre-industrual times, while global average temperatures have gone up 0.89°.
Changes recorded in winter
- Milder temperatures and reduced cold snaps
Halving of the number of days with frost in Chambery, for example
- Reduced snowfall
Halving of snowfall at 1,000m in Chamonix over 40 years
In Savoie 15 to 25% reduction in snow depth at 1,500m
The Alps are losing 6 days of snowfall per decade
One and a half months less snowfall is predicted for 2050
- Significant increase in summer temperatures
- Increase in periods of drought
- Risk of flooding and landslides in spring and at the end of the autumn
- Raising of the 0 degree isotherm by 300m
15 to 20% increase in days of thaw in high altitude
Rockfalls due to raised height of the permafrost
Access to high mountains dangerous or restricted (Mont-Blanc, Ecrins)
Glaciers, guardians of the climate
Mer de Glace has retreated 2.3 km since the middle of the 19th century and the Argentiere Glacier 1.7 km. In just 30 years the Les Bossons Glacier has retreated 1 km, right before our helpless and sad eyes. Specialists tell us that Mer de Glace will retreat by another 1 km over the next 30 years. Each year 15 to 20 extra steps need to be added into the cliff to reach the Mer de Glace from Montenvers. The loss of depth of the glaciers is also huge: 100m from the Mer de Glace and 90m from the Argentiere Glacier, at 1,800m of altitude. The stock of fresh water for Europe is melting away under the Alpine sun.
The danger posed by the appearance of inter-glacial lakes and water pockets, with the devastating risk of bursting and flooding, is real and has already been seen at Tete Rousse. In 2010 a water pocket of 65,000m3 was discovered and it had to be drained off as a matter of urgency in 2010, 2011 and also 2012.
Cold glaciers, above 3,500m of altitude, are also warming at an alarming rate. The internal temperature of the ice has increased by 2° since 1994, on the Dome de Gouter, at 50m of depth. These glaciers are often hanging glaciers. The rise in temperature brings with it a huge risk: if the water succeeds in flowing between the ice and the mountain which support the glacier, huge slabs of such glacier could slide and fall, with cataclysmic consequences on the valleys below.
Using a moderate warming model (+3°), all glaciers below 3,700m could disappear before the end of the century.