FORCeS has reached its overarching goals as it has contributed to understanding and reducing the uncertainty in estimates of aerosol-cloud-climate interactions. FORCeS provided new knowledge on the behavior of key aerosol components (organic compounds, nitrate, light-absorbing components) and processes (ultrafine aerosol dynamics, interactions with clouds), as well as cloud processes (interaction with aerosol particles, microphysics cloud droplets and precipitation formation as well as ice formation in the atmosphere). FORCeS used this improved understanding to evaluate and develop leading Earth System Models (ESMs), which form the methodological basis for future projections e.g. discussed by the IPCC. To evaluate and constrain the model predictions, FORCeS collected observational data over various scales and developed robust theories for interpreting the observations. To fill key gaps in observational constraints, novel laboratory experiments and field campaigns (in e.g. the Arctic, boreal, and central European environments) were completed successfully, and detailed models were used to develop new process-based metrics and constraints for ESM evaluation. Historical aerosol loadings and sophisticated statistical methods were used together with present-day observations to highlight the most important revisions needed in the ESMs, and to derive constraints on Earth’s climate sensitivity. Novel approaches and tools for evaluating ESMs were developed and used to pinpoint important areas for future model development. The research output from FORCeS in the form of publications and conference presentations has been substantial, and targeted efforts were made in the final period to ensure efficient dissemination and communication of the project results to the relevant audiences, in the form of e.g. conference presentations, workshops, policy briefs and news articles on the FORCeS website. In summary, FORCeS reached its objectives and made targeted efforts to ensure effective dissemination and legacy of the project outcomes.
