Heat forecast at Swiss SBB locations

Based on the CH2018 climate scenarios for Switzerland [CH2018 (2018)], we created a nationwide gridded dataset with a resolution of 250 m using geostatistical interpolation [Remund, J. et al. (2020)], which was used in this analysis. The current climate indicators at SBB locations were compared with future values to calculate trends and assess their magnitude. Various climate scenarios and time horizons were considered:

Climate Scenarios:

• A moderate climate scenario, where greenhouse gas emissions are curbed in the coming years, but atmospheric concentrations continue to rise.
• A high climate scenario, in which no climate protection measures are implemented.
• Current climate conditions ("Climate 2010").
• Climate simulation for 2048 – 2073 ("Climate 2060").
• Climate simulation for 2073 – 2098 ("Climate 2085").

Time Horizons:

The focus was placed on various temperature parameters, as they show the clearest future trends and have a direct impact on the operation and maintenance of SBB’s infrastructure. In addition to mean, minimum, and maximum temperatures, we also analyzed climate indices that further highlight the difference between today's and future climate conditions:

• The number of hot days per year, i.e., the number of days per year when the air temperature at a given location exceeds 30°C.
• The number of frost days per year, i.e., the number of days per year when the air temperature at a given location falls below freezing (0°C).

The results show that, regardless of the climate scenario, an increase in hot days is expected at all SBB facility and station locations without exception.

Distribution of the analyzed SBB stations (brown dots) across the five natural regions of Switzerland

The increase in annual mean temperature will be most pronounced in the northern pre-Alpine and inner-Alpine valleys of Switzerland (Rhone Valley, Rhine Valley, Seeztal/Walensee, Linth Valley, and Reuss Valley). Depending on the climate scenario considered, SBB locations in Ticino — particularly in the Locarno region and southern Ticino — are also expected to experience significant warming.

The absolute number of hot days per year will be highest at the SBB locations in the Rhone Valley, the Locarno and southern Ticino regions, and the Geneva area.

Under the moderate climate scenario, the number of hot days at some SBB locations is expected to double by 2060 and triple by 2085 compared to today’s climate. In contrast, under the high climate scenario, a tripling of hot days is already expected by 2060, with a fivefold increase by 2085. Given these projections, early integration of these scenarios into the planning of future stations and infrastructure is a high priority for SBB.

The rising temperatures also bring some benefits for infrastructure maintenance: By the end of the 21st century, the number of frost days per year will decrease significantly at all SBB locations. This will, for example, increase the number of days per year when infrastructure work can be carried out and reduce the need for winter maintenance.

The CH2018 climate scenarios are currently being updated. The upcoming CH2025 scenarios will provide new climate projections for Switzerland, offering additional opportunities for similar analyses using the latest scientific data.

References:

• CH2018 (2018), CH2018 – Climate Scenarios for Switzerland, Technical Report, National Centre for Climate Servic : es, Zurich, 271 pp. ISBN: 978-3-9525031-4-0
• Remund, J., 2020. Downscaling CH2018. Berechnung von Meteo- und Trockenheitsindizes für die Waldforschung. Methoden und Resultate – Version 2. Meteotest, 25 S.