Climate Forcings, Solar Geoengineering, and Long-term Drought Dynamics over Europe

Europe is experiencing an increasing risk of long-term drought as a result of anthropogenic climate warming, declining snowpack in mountainous regions, and changes in large-scale precipitation regimes. These processes contribute to the intensification of climate extremes and pose growing challenges for water-resource management, ecosystem resilience, and socio-economic stability. While CMIP6 climate projections are widely used to assess future drought risk across Europe, the potential implications of solar geoengineering for the spatio-temporal behaviour of long-term droughts remain unexplored.

This study presents a conceptual, scenario-based framework to examine long-term meteorological drought dynamics over Europe using CESM2 simulations from both CMIP6 shared socioeconomic pathways (SSP2–4.5 and SSP5–8.5) and GeoMIP6 solar geoengineering experiments (G1–G4 and pi-control). Drought conditions are evaluated using SPI-12, and drought characteristics—severity, duration, and intensity—are quantified using run theory to enable consistent comparison across contrasting climate-forcing pathways.

The proposed framework facilitates a structured multi-scenario assessment of drought responses under conventional greenhouse-gas-driven warming and idealized solar-radiation-modification scenarios, while maintaining scientific neutrality regarding the feasibility, deployment, or governance of geoengineering interventions. By jointly examining these pathways, the analysis aims to identify potential shifts in drought persistence, intensification, and large-scale spatial expression, key elements governing the spatio-temporal organization of long-term droughts and compound drought risk.

Overall, this work contributes to a more comprehensive assessment of long-term drought risk in Europe by explicitly linking climate extremes to both traditional climate forcings and hypothetical geoengineering perturbations. The framework is transferable and provides a robust basis for drought risk assessment, supporting adaptation planning and long-term drought governance under deep uncertainty associated with future climate trajectories.

Keywords: Climate extremes; Drought; SPI-12; Solar geoengineering; Europe.