Coupling Astrodynamics and Climate Modeling for a Distributed Planetary Sunshade System: Impacts of Non-Uniform Radiative Forcing

This work investigates the astrodynamics and climate impacts of non-uniform radiative forcing associated with a Planetary Sunshade System, a space-based solar geoengineering concept based on a distributed swarm of Solar-Sail Satellites (SSSs) partially or fully assembled in the vicinity of the L1 point of the Sun–Earth/Moon Center of Mass system. Previous climate-modeling studies, including the GeoMIP experiments G1, G1ext, G2 and G6Solar, have focused on instantaneous or gradual uniform variations of the solar constant, without addressing the spatially and temporally varying radiative forcing arising from differential shading produced by a realistic space-based system. The proposed framework enables the generation of latitude-and season- dependent shading patterns and provides a consistent methodology to compute both the natural insolation field and the sunshade modified insolation. The resulting non-uniform radiation pattern is implemented within the EC-Earth3 General Circulation Model, considering a fully coupled atmosphere–ocean configuration. Time-dependent variations associated with the elliptic motion of the primaries are also included. The study integrates an astrodynamical framework describing the orbital architecture and deployment requirements of the SSSs swarm, enabling the translation of orbital configurations into physically consistent radiative forcing input fields used by the climate model. Dedicated long-term simulations are conducted under selected IPCC emission pathway scenarios to evaluate both transient climate responses and quasi-equilibrium states. The results highlight the coupling between orbital design choices and climate outcomes, analysing the response of key climate variables such as global and regional surface temperature patterns and large-scale atmospheric circulation. For the first time, this framework consistently combines the astrodynamics of a distributed SSSs Planetary Sunshade System with a fully coupled Earth System Model, enabling the assessment of climate feedbacks arising from realistic, non-uniform radiative forcing patterns. These results contribute to strengthening the physical understanding and feasibility assessment of space-based solar geoengineering concepts and provide a first step toward an implementation-oriented roadmap. The proposed framework addresses UN Sustainable Development Goal 13 (Climate Action) by exploring the potential role of space-based Solar Radiation Management as a complementary strategy to mitigation and decarbonization efforts, supporting long-term climate stabilization and resilience in a rapidly warming Earth system.