The temperature in the lower atmosphere decreases with increasing altitude and falls below 0 °C at a certain point. This altitude is referred to as the zero degree limit. The zero degree line influences, among other things, the development of vegetation, the snow line and the water cycle, thereby decisively shaping the habitats of humans, animals and plants.

The near-ground zero degree line is derived from ground measuring stations. Some measurement series from MeteoSwiss ground measuring stations have daily temperature data dating back to 1864. This enables precise statements to be made about how the near-surface zero degree line has developed since the start of systematic recording.

Historical development of the zero degree line in Switzerland in the context of climate change

Similar to the near-surface temperature, the height of the zero degree line over Switzerland is also rising sharply as a result of man-made climate change. Since records began in 1864, the near-surface zero degree line on the northern side of the Alps has risen by 200 to 700 m and the rise has accelerated significantly in some cases since 1970. Between 1871 and 1900, the zero degree line in winter was still at the altitude of the large cities of Zurich or Geneva (approx. 400 m above sea level), whereas today (as of 2024) it is at the altitude of Einsiedeln (approx. 900 m above sea level). Another example that illustrates the rise: today, the average zero degree limit in March is almost as high as it used to be in April.

The zero degree line on the southern side of the Alps is a few hundred meters higher than on the northern side of the Alps, especially in winter, and the observed rise is somewhat smaller than in the north in most months.

Future and climate scenarios

MeteoSwiss has calculated various climate scenarios for the future, which attempt to provide an estimate of the future state of the climate. They are based on estimates of different developments of greenhouse gases in the atmosphere up to the end of the century.

As mentioned above, the zero degree limit will continue to rise in the coming decades. As a consequence, the area in which the conditions for snowfall are present is shrinking noticeably. According to the simulations, the zero degree line in winter could climb from just under 900 meters today to just under 1500 meters above sea level by the middle of the 21st century. Strong climate protection could prevent some of the further rise in temperatures in Switzerland and also slow down the rise in the zero degree line.

Information on the map

The map shows the development of the zero degree limit in the period from the end of the 19th century to the end of the 21st century. The values shown correspond to an average over 30 years for the winter months (December to February) or summer months (June to August) over the whole of Switzerland.

Several pieces of information are displayed on the map:

The values of the zero degree limit for the past for winter and summer. These values were derived from ground-level weather stations.

For the future, the values of two different climate scenarios are presented: one variant "with climate protection", in which climate protection measures are taken, and one "without climate protection", in which no climate protection measures are taken. For each climate scenario and for each season, the lowest value among the simulations, the highest value, as well as the uncertainty are represented.

In addition, a comparison between the two scenarios is presented for the future: the mean zero degree limits of both scenarios are shown on the same map. This makes it possible to become more aware of the positive effects of climate protection measures.

Some important notes: The values shown are to be understood as approximations of the zero degree limit. They give a general and rough idea of the course of the zero degree line over a period of approx. 200 years. Small-scale effects such as cold air lakes are not resolved, which is why the values must not be used with pinpoint accuracy. In addition, the averaged values for the whole of Switzerland are used for the visualization and regional differences (e.g. northern Switzerland or southern Switzerland) are not taken into account.