Anthropogenic Aerosol Forcing for CMIP7

We present the historical anthropogenic aerosol dataset SPv2.1, produced using the Simple Plumes (SP) aerosol module (Stevens et al., 2017), for use in the Coupled Model Intercomparison Project Phase 7 (CMIP7). The dataset covers the period from 1850 to 2023 inclusive and provides updated and extended estimates of anthropogenic aerosol optical properties and their effects on clouds by incorporating the latest emission inventory and extending the temporal coverage beyond earlier versions. The SP module induces anthropogenic aerosol effects in a simplified but physically plausible way, linking emissions from major industrial and urban regions to global model grids using nine predefined plumes around the world. Present-day monthly plume profiles of anthropogenic aerosol extinction are scaled with historical time series of SO₂ and NH₃ emissions to reproduce monthly changing spatial patterns of anthropogenic aerosol forcing. Compared to the earlier CMIP6 dataset, SPv2.1 shows moderate differences. The most pronounced differences occur over Africa between approximately 1940 and 1990, where SPv2.1 exhibits higher aerosol optical depth and increased cloud droplet number concentrations. These differences arise from updates in the underlying emission inventory. Additionally, SPv2.1 extends the historical period by nine years relative to CMIP6, which ended in 2014, thereby providing a more recent representation of present-day anthropogenic aerosol forcing. The SPv2.1 dataset supports a wide range of applications related to anthropogenic aerosol effects on radiation, clouds, and atmospheric composition across multiple models and modeling centers. It is publicly available for use in CMIP7 and other applications (Fiedler and Azoulay, 2025). Ongoing work now extends the SPv2.1 dataset to future anthropogenic aerosol scenarios from ScenarioMIP for CMIP7. The SPv2.1 scenarios will be derived from seven future emission pathways, spanning from high to very low anthropogenic emissions of SO₂ and NH₃ until 2125. In addition, climate model simulations with ICON-XPP are being performed to assess the aerosol radiative forcing for both the historical period and future scenarios.