The snow season is on average about 37 days shorter in Switzerland since 1970 according to research (check out this link and this [link](http://link.springer.com/article/10.1007/s10584-016 -1806-y)) of the SLF. That's more than a month without snow in the mountains. That's more than a month with no skiing or snowboarding. Now that is significant. The data from 11 weather stations has been used in the period between 1970 and 2015 for this research. The weather stations were situated between 1100 and 2540 meters. The most well-known weather station is the one on the Weissfluhjoch high above Davos.
It is the first time that such a study has been carried out for the higher parts of the mountains. According to the researchers the season starts on average 12 days later and ends an average of 25 days earlier. In addition, the maximum snow cover is on average 25% less thick and it's reached 28 days earlier than in the early years of measurement.
For those who have followed the past winters in the Alps, this shouldn't be too much of a surprise. It was mainly green in the Alps during Christmas of 2014 and 2015, while the record for the highest temperature was broken over and over again. The researchers connect this with the climate change and the rising temperatures on earth.
Yet some things in this research are striking:
The NAO (North Atlantic Oscillation) appears to play an important role in how the winters develop in the Alps. Cold and snowy winters are usually associated with a negative NAO, while warmer and often drier winters are linked to a positive NAO. Below you can see a graph with the evolution of the NAO since 1860. What is striking is the strong negative NAO between 1950 and 1972. Years where more snow came down than normal.
The NAO been mostly positive since the start of the measurements, which also (partly) explains the differences between the beginning of measurements in 1970 and the current measurements. [A look at the data per measuring station seems to confirm this](https://www.researchgate.net/figure/308480847\_fig3\_7-year-simple-moving-average-of-the-days-with-snowpack-DSP-1-20 -50-and-100-cm-or) (partly). Unfortunately I don't have access to the complete results.
Climate change or not, the researchers point us on a worrying trend where the snow cover is thinner than normal and it's gone faster than normal. Let us hope that the NAO will be negative again quickly.