National climate scenarios are an important basis for the public and private sectors to plan and design adaptation and mitigation measures. Regional or local assessments of future climate change are therefore an important climate service.
The "Climate CH2025" project is based on the Federal Council's mandate to the Federal Office of Meteorology and Climatology MeteoSwiss to provide regularly updated climate scenarios as part of the federal government's adaptation strategy. The climate scenarios are developed together with the main partner ETH Zurich and other institutions under the umbrella of the National Centre for Climate Services (NCCS).
The results of Climate CH2025 were published on 4 November 2025. The results and further information on Climate CH2025 can be found on our website:
Motivation
Since the CH2018 scenarios were published in 2018, both the science and the needs of users have evolved. New science, as documented in the IPCC report (AR6), has been published, and new high-resolution and convection-permitting climate models have been developed. Thanks to the continuous involvement of users in the design of the scenarios, MeteoSwiss and ETH were able to gain a detailed picture of the requirements for future climate and climate change information.
Aims of Climate CH2025
The Climate CH2025 project, launched in March 2023, addresses identified gaps in existing climate scenarios and additional requirements. Like previous generations of climate scenarios, the project was a collaboration between MeteoSwiss, ETH Zurich, and other partners from science and government.
Two main scientific issues were in focus:
- How can observations and model-based climate scenarios be better integrated to provide consistent and temporally comprehensive information to users in a way that meets their needs?
- What is the expected future development of climate extremes in Switzerland and what are the underlying processes?
The previous CH2018 climate scenarios already showed clear climate trends: more extreme heat, more frequent heavy precipitation, drier summers and winters with less snow. While the qualitative statements have not changed, the quantitative assessments have been updated.
Over Western and Central Europe, the temperature has risen more sharply since 1980 than projected in the regional climate models that form the basis for CH2018. There are two main explanations for this: On the one hand, air quality - worldwide, but also in Europe - has improved significantly since the 1980s, meaning that the concentration of aerosols in the air has decreased. As a result, less sunlight is scattered back, causing the atmosphere to heat up more (brightening effect). This was not directly taken into account in previous models (e.g. Wild, 2012). On the other hand, natural fluctuations in the climate may play a significant role.
In the Climate CH2025 scenarios, observations and models are now better integrated and the modelled temperature trend has been adjusted to reflect actual developments. As a result, the Climate CH2025 scenarios show higher warming than previous projections. In a 3-degree world, this corresponds to approximately 10 to 15 percent more warming than in CH2018.
Climate CH2025 is based on CH2018 and expands on it with longer measurement series, improved process understanding and information from new, high-resolution climate simulations that allow for convection. The current MeteoSwiss reference period 1991–2020 was also used. In addition, detailed information on heavy precipitation and heat in urban areas, among other things, was compiled. With the introduction of global warming levels, it is now possible to link political climate targets directly to climatic impacts.
References:
Schumacher, D.L., Singh, J., Hauser, M. et al. Exacerbated summer European warming not captured by climate models neglecting long-term aerosol changes. Commun Earth Environ 5, 182 (2024). https://doi.org/10.1038/s43247-024-01332-8
Wild, M. (2012). Enlightening global dimming and brightening. Bulletin of the American Meteorological Society, 93(1), 27-37.