An ensemble system of regional reanalyses will be developed and run for the climatological time scale. Theinformation content of the datasets and their uncertainties will be assessed in several ways and statisticsanalysed.The project will provide long-term datasets of Essential Climate Variables (ECVs) on the European regionalscale in order to support adaptation action and policy development. The datasets will contribute to Climateservices for Copernicus, climate monitoring and research.Regional reanalyses will be made in Ensemble mode and there will also be individual reanalyses with differentmodels and methods. Observational data rescue (digitizing data in archives not currently available for use) willcontinue from EURO4M and enhanced gridded datasets will be developed and used for validation. Theensembles together with gridded datasets will form the basis for estimation of uncertainties of the constituentmembers. Large datasets will be built up and open and user-friendly access methods will be established togetherwith the work in other topics of the SPACE call.This project builds on the experiences and developments in EURO4M but now the reanalyses will coverclimate analysis time scales (30 to 50 years) and pioneer ensemble techniques for regional scale and highresolutionreanalysis. It will build on and extend the global reanalyses (topic -01 ERA-20C, ERA-CLIM2 and ERA-Interim).Further downscaled high-resolution reanalyses will also be performed where more near surface ECVobservations can be utilized. Indicator information (including uncertainties) will be applied to the reanalyses andthere will be extensive validation against remote sensing and hydrological data. They will add to the validationeffort, respond to user requirements, and demonstrate how the reanalysis information is best utilized forunderstanding past climates and climate change.