Convection-permitting regional climate simulations to support the national climate scenarios for Belgium

National climate scenarios play a key role in translating global and regional climate projections into actionable information for impact assessment and policy-making. Within the framework of the CORDEX.be II project, a new generation of climate scenarios for Belgium is currently being developed, based on convection-permitting regional climate model simulations at kilometer scale. The ensemble combines three models - ALARO, MAR, and COSMO-CLM - and covers a reference period as well as two future 20-year time slices corresponding to global warming levels of +2°C and +3°C.

Particular attention is given to the representation of climate extremes, such as heatwaves and intense precipitation, through the careful selection of boundary conditions from CMIP6 global climate models that demonstrate strong performance in simulating these phenomena. The credibility of the regional simulations is assessed through their ability to reproduce key features of the present-day climate. Moreover, the climate-change signals are considered against the range of the coarser-scale EURO-CORDEX projections over Belgium. 

A central component of this work is the close collaboration with stakeholders throughout the development process. End users from multiple sectors are actively involved in the scenario choice and the co-design of climate indicators, ensuring their relevance for practical applications, and shaping the format and usability of the final products. The climate indicators and bias-corrected time series will provide a robust basis for assessing climate impacts across sectors, including agriculture, health, and water management, and for supporting adaptation planning to future climate extremes in Belgium. The climate indicators will be provided to the stakeholders as well as through an online portal.