Because crop yields are central to food security and economic resilience, their sensitivity to SAI makes vegetation response one of the most consequential impacts of stratospheric aerosol injection (SAI). SAI alters crop yields primarily through changes in precipitation, diffuse radiation (sunlight scattered by aerosols rather than arriving as a direct beam), temperature, and nutrient availability. Current evidence suggests that SAI would likely have a ~10% or more increase in global crop yields relative to background warming scenarios (Clark et al., 2023; Fan et al., 2021). However, these responses carry significant uncertainty at the local and regional scales.
Uncertainty exists in the magnitude of global crop yield changes, but the localized precipitation changes that may decrease local crop yields matter most. Modeling uncertainty is high for these impacts, making them hard to predict accurately.
Other uncertain impacts include a plausibly large diffuse-light fertilization effect (the possibility that more scattered sunlight lets plants photosynthesize more efficiently). Models show diffuse radiation increasing by 11–50% under SAI (Xia et al., 2016; Yang et al., 2020). How much this mechanism actually enhances crop and vegetation growth remains unclear, since its magnitude and representation vary widely across models. Additionally, models might not fully capture the potential impact of nitrogen limitation on plant production – cooler soils have reduced nitrogen supply which may reduce fertilization benefits. (Duan et al., 2020; Parry et al., 2026). Mechanistically understanding these competing drivers as well as better modeling regional precipitation changes — and how they interact across different SAI strategies, regions, and crop systems — is essential for assessing whether SAI could create new food security risks.
