Natural Factors, Not CO2, Driving Switzerland’s Surprising Snow (Non)Trends

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Strongly fluctuating snow cover in Switzerland appears to be coupled to ocean cycles

By Dr. Sebastian Lüning and Prof. Fritz Vahrenholt
(German text translated/edited by P Gosselin)

For those who love snow, there are supposedly dark clouds on the horizon. Snow is becoming less and less. Never in the past has snow been as seldom as it is today. In the past it was always there when we needed it. Climate change, however, is putting an end to it. It’s a sad story that everyone has been reading in the newspapers. Of course humans are to blame.

It turns out many of these stories in the press are relatively scant on facts. We’ve reported with a number of hard facts on this topic on a number of occasions, and they don’t exactly fit very well with the alarmist narrative.

Today we are taking a look at Switzerland to see how snow has been doing in the land of the Alps over the past years and what we might expect for the future. In WIREs Climate Change, Martin Beniston provided and overview in 2012 on the Swiss snow trends over the past 90 years (Figure 1).

If you look at the curves for mean snow depth for the 10 stations, we see a great amount of natural variability. Beniston sees a relationship with the North Atlantic Oscillation (NAO), which is an important ocean cycle.

Figure 1: Snow depth curves during the winter months for 10 representative stations at 500 – 2700 m elevation: Zurich, 556 m; St Gallen, 779 m; Chateau d’Oex, 985 m; Engelberg, 1035 m; Scuol, 1298 m; Montana, 1508 m; Davos, 1590 m; Segl-Maria, 1798 m; Arosa, 1840 m; Weissfluhjoch, 2690 m. running five year mean. Source: Beniston 2012.

Now let’s examine the duration of snow cover (Fig. 2). Once again we see enormous natural variability. We do not see a trend to shorter snow seasons, and the curve fluctuates wildly.

Fig. 2: Duration of snow cover (in days) in Switzerland using station data. Source: Beniston 2012.

The WSL Institute for Snow and Avalanche Research describes the Swiss trends at his website as follows:

An analysis of snow depths over many years shows that the annual snowpack is subject to large variations, both from year to year, and as regards location (northern/southern flank of the Alps, western/eastern Switzerland, prealps/Alps).

These huge natural fluctuations are the hallmark of the snowpack in wintertime. For this reason, it is difficult to draw any firm conclusions concerning climate-related changes in the snowpack or avalanche activity. Most of the winters in the 1980s, for example, were accompanied by large, rather than smaller quantities of snow. In contrast, towards the end of the 20th century, many measuring stations recorded minimum snowfall. The winters of the 21st century to date have shown a slight recovery, but snow depths are generally below average.

Clear reduction in the Mitteland and prealps

The described changes are more apparent, the lower the altitude of the observation station. Especially in the Mitteland region, the last 20 years are regarded as having the least snowfall since conventional measurements began about 130 years ago – and, according to historical records, the least for 300 years or more. A more exact analysis shows that the trend towards less snowy winters for most stations below 1300 m is statistically significant.

At stations above 2000 m, there is as yet no indication of a reduction in snow depths attributable to climate change. Further investigations have made it clear, moreover, that the reduced snow depths are primarily a consequence of higher winter temperatures, rather than a reduction in precipitation. An analysis of the seasonal differences shows a slight trend towards small amounts of snow in the early winter at intermediate altitudes, and indications of amplified melting during the spring at all altitudes.”

And because of the strong variability measured in the winter, it is also valid for Christmastime. Balz Rittmeyer and Marc Fehr have closely examined snow statistics for Switzerland and come up with an amazing result, and reported it at their blog at the Tagesanzeiger:

The White Christmas myth
Also this year there wasn’t any snow in the lowlands. Whoever thinks there was snow more often during the Christmas holidays in the past, they should look at these data. Is climate change responsible for fewer white Christmases? No. A look at the statistics shows that on December 24 and 25 there was not more snow in the past. Over the measured dataset is almost 80 years long and there is no detectable trend to see. In fact the longest stretch of Christmas without snow occurred from 1941 to 1949.”

Read the whole article at the blog of the Tagesanzeiger. Also the 2016/17 winter has shown us the unpredictability of Swiss snow cover. The online SRF wrote on 28 April 2017:

Record snow at St. Gallen: Never has there been this much snow, so late
This morning the weather reporter of the City of St. reported a snow depth of 26 centimeters. Since mid April this has never happened. The data go back to 1959. The previous record was 25 centimeters in the year 2001, on April 22. Now the record value has been pushed back almost one week. The second half of spring is defined as the middle of April to the end of May. Up to now there has been a maximum of 25 centimeters, namely in January. Also interesting: For the previous record it was the same. On April 22 there was also more snow than there was in the previous winter.”

St. Gallen is 675 m elevation, and well represents a lower elevation station. So will the trend in the middle of the country mean less snow in the winter?

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May 26, 2017 at 01:56AM