As a consequence of rising temperatures, spring and summer development of vegetation is occurring significantly earlier nowadays than several decades ago. Therefore, plants are excellent indicators for the effects of the global rise in temperature. The meteorological service MeteoSwiss is collecting a variety of data to illustrate these changes.
Phenology is the study of cyclic growth and development phenomena occurring over the course of a year in relation to flora and fauna. In the case of plant phenology, the onset dates of the so-called pheno phases such as new leaf formation, flowering, ripening of fruit, leaf colour change and fall are observed and recorded.
Did vegetation start to grow especially early in a particular year due to temperatures being much higher than average? The observations of the phenological observation network form the basis of the climatological evaluation of current vegetation patterns. Current analyses can be found in the monthly and annual retrospective reports.
Monthly and annual reports (German, French, Italian)
The spring index shows the point of time of vegetation development in spring compared to the long-time average from 1991-2020. The annually determined index summarises the phenological spring phases, from the blooming of the hazel bush to the new leaf formation of the beech tree.
Aside from the observation network, two long-term and hence very valuable phenological series of observations exist in Switzerland, which have been used to observe two types of plants since 1808 and 1894 at the same location: a horse chestnut tree in Geneva and the blossoms of a particular cherry tree in Liestal.
Just as with climate, in phenology the timing of vegetation development can be described by a long-term average. A 30-year average is called a norm value. A comparison of the annual phenological data with the norm value shows whether a year has an early or late vegetation development. The same 30-year periods are used in phenology as in climatology: 1961-1990 and 1991-2020. The 1961-1990 norm period is used for classification in the long-term climate development and that of 1991-2020 for comparison with the present climate.
For all phenological phases, annual mean values of the onset date from 1956 and the 1961-1990 and 1991-2020 norm values calculated from them are provided in tabular form. They are calculated as mean values for the whole of Switzerland and for different altitudinal zones. For the altitudinal zones, only phenological phases with sufficient observations over the entire data series since 1956 were selected.