Swiss climate scenarios – an ongoing journey

Consistent and up-to-date national climate scenarios are an indispensable basis for public and private sectors to plan and design adaptation and mitigation measures. Regional or even local assessments of future climate change are therefore an important climate service. The latest edition of Swiss Climate Scenarios CH2018 was released in 2018 (www.climate-scenarios.ch). Overall, a further increase of mean temperatures is projected, accompanied by four highly impact-relevant facets: more intense and more frequent precipitation extremes, more intense and more frequent hot extremes, drier summers, and snow-scarce winters. Since the release of the CH2018 scenarios, science as well as user needs have evolved. Scientific advances such as those documented in the latest IPCC report (AR6) have been published and new high-resolution convection-permitting climate models have been developed. Thanks to our ongoing user engagement and consultancy, a more detailed landscape of user requirements was established. In the recently launched project Klima CH2025, identified gaps in the existing climate scenarios and additional user requirements will now be addressed. Similar to previous climate scenario generations, the new project is a joint effort involving the Federal Office of Meteorology and Climatology MeteoSwiss, ETH Zurich and further partners from academia and administration. The results of Klima CH2025 will be based on the existing CH2018 scenarios and will extend them with new scientific insights and products. Two main scientific questions will be addressed: 1) How can we better merge observations and model-based climate scenarios in order to provide consistent and temporally seamless information to serve user needs?; 2) What is the projected evolution of impact-relevant climate extremes in Switzerland and what are their underlying processes? Guided by these two questions, we will develop a range of new products, engage with stakeholders, plan active communication and dissemination. In this presentation, the general approach of Klima CH2025 as well as first results will be presented.