WP4 will develop and apply new observational constraints for process-parameterizations developed in WP1. We will develop a set of top-down metrics to assess the magnitude and spatio-temporal patterns of simulated fluxes based on a combination of remote-sensing data and bottom-up products integrating in situ measurements. WP4 will further develop dedicated bottom-up metrics to assess process-level responses to global change of particular processes (e.g. the CO2 response of terrestrial C storage). These metrics will be made available to the consortium to test improvements made during CRESCENDO. Suitable, new top-down and process-oriented diagnostics and performance metrics will be integrated into ESMValTool.