The goal of CRESCENDO is to improve the process realism and simulation quality of European Earth System Models (ESMs) in order to increase the reliability of future climate projections. In particular, the project aims to improve the representation of terrestrial and marine biogeochemical processes, natural aerosols and trace gases in the atmosphere, and their interactions. CRESCENDO brings together seven European ESM groups with three Integrated Assessment Modelling teams, as well as experts in ESM evaluation, feedback analysis, and science communication. KNMI is contributing as a partner of the EC-Earth consortium, and will focus on aerosols, atmospheric chemistry and interactions with the biosphere.