MeteoSchweiz has analyzed the data from Swiss weather stations in great detail, and series have been homogenized (Begert and Frei, 2018). For several locations precipitation and temperature data are available since 1864. Maps and graphics, as well can be found on the https://www.meteoschweiz.admin.ch/home.html?tab=overview of MeteoSchweiz. Here we discuss two records that are most relevant to the behaviour of glaciers: summer temperature and winter precipitation averaged over Switzerland, relative to the mean of the period 1961-1990. The black lines in the graphs show the result of low-pass (20 yr) filtering.
Summer temperature increased only slightly until around 1980, when a significant warming trend of about 2 °C in 40 years started. The relatively cool conditions in the period 1960-1980 caused advance of some smaller and medium-size glaciers. The temperature records for the other seasons show a rather similar behaviour.
The picture is different when it comes to precipitation. Only in winter was a clear trend toward increased precipitation observed. The period from 1864 to 1900 was apparently quite dry, which could partly explain the glacier retreat in the Alps in the second half of the 19th century.

However, precipitation changes show greater regional differences than temperature changes, which makes the analysis of long-term changes more uncertain.
It is very likely that climate warming will continue. For the RCP2.6 scenario an increase in summer temperature of 0.9 to 2.5 °C is expected for Switzerland in 2060 (relative to the period 1981-2010). For the RCP8.5 scenario this is 2.3 to 4.4 °C. At the same time, winter precipitation might increase (-1 to 16 % for RCP2.6; -3 to 21 % for RCP8.5). However, a larger part of the winter precipitation may fall as rain.

Abbildung: W. Haeberl

References

Begert M and Frei C (2018): Long-term area-mean temperature series for Switzerland—Combining homogenized station data and high resolution grid data. Int. J. Climatol., 38, 2792-2897, https://doi.org/10.1002/joc.5460