Impacts of Ultraviolet Flux from Stratospheric Aerosol Intervention on Agricultural Production

Sulfate aerosols formed after stratospheric aerosol intervention (SAI) or major volcanic eruptions would reduce stratospheric ozone due to anthropogenic halogens. The amount of ozone depletion would depend on the surface area provided by the extra sulfate aerosols and the timing of the injection. As ozone depleting substances gradually decrease in the stratosphere, later sulfate injections will have less impacts on ozone. Under SAI, surface ultraviolet (UV) radiation would change as a result of the balance between more UV transmission due to stratospheric ozone depletion and more UV scattering from the injected aerosol. Regional surface UV changes would be more complicated, as they depend on stratospheric ozone depletion, aerosol scattering, cloud coverage changes, latitude, altitude, and seasonal variations. Plants may adapt to higher UV-B concentrations by producing plant pigmentation compounds to reduce the penetration of UV-B, but there might be some negative impacts on their growth. At present, there are only a few studies on the effects of SAI on surface UV-B irradiance, and no studies on how agriculture would respond to different levels of UV-B under SAI. Here we review the impacts of UV-B on agriculture from existing literature, field and lab experiments. Based on that, we build a UV damage function and implement that into the Community Land Model version 5 crop (CLM5crop). We will then use the Tropospheric Ultraviolet and Visible radiation model applied to output from SAI climate model simulations to estimate the impacts of stratospheric ozone depletion on UV radiation reaching Earth's surface and use CLM5crop to understand the UV impacts on the major grain crops.