Addressing uncertainties of SAI of solid particles

SAI by means of sulfuric acid aerosols could lead to adverse side effects such as impacts on the ozone layer and stratospheric heating, and sizable effects on the large-scale atmospheric circulation. Recent studies have suggested that injection of solid particles such as alumina, calcite or diamond instead of SO2 could reduce some of these adverse side effects. However, the expected improvements are subject to large uncertainties, which include processes such as solid particle dispersion and agglomeration in the turbulent aircraft-wake as well as heterogeneous chemistry. We constrain some of these uncertainties by experimental work on heterogeneous chemistry and solid particle coagulation of calcite particles. Subsequently, we use a global aerosol-chemistry-climate model that interactively couples microphysical and chemical processes of solid particles as well as sulfuric acid aerosols with model radiation and transport. We show that reduced stratospheric warming can substantially decrease impacts on global and regional climate while impacts on ozone from uptake of HCl and HNO3 on calcite are likely small. However, coagulation effects could substantially decrease the backscattering efficiency of the solid particles. This work presents a path forward for climate intervention research and provides recommendations on how to improve our understanding of SAI with alternative materials.