Direct human forcing for earth system and climate impact modelling under CMIP7 scenarios

Abstract. Direct human forcings are important input variables for earth system and climate impact models, describing societal influence on changes to climate and related risks. Here, we present a new multisource dataset consistently describing the spatial and temporal dynamics of the two most important direct human forcings: population and economic production. The dataset was created by harmonizing multiple datasets to achieve smooth transition both the historical (1850–2025) and future (2026–2100) time periods, and to cover many resolutions down to 1 km. Projections were produced for the latest Shared Socioeconomic Pathways (v3.2, 2025), applicable to the seven scenarios designed for Coupled Model Intercomparison Project Phase 7 (CMIP7) earth system models, which require population density as one of the inputs. In a further stage of CMIP7, the dataset will be applied to modelling (societal) climate impacts, particularly in the Inter-Sectoral Impact Model Intercomparison Project 4 (ISIMIP4). This requires additional variables such as population split by degree of urbanization, gross domestic product and fixed asset value, and high resolutions of the data. We show that the new data vastly improves upon quality and availability of direct human forcings compared to previous CMIP phases. It enables, for instance, process-based impact simulations across sectors, impact attribution research, risk assessment and socio-hydrology.