Injecting solid particles into the stratosphere could mitigate global warming but currently entails great uncertainties

Stratospheric aerosol injection could mitigate harmful effects of global warming, but could have undesirable side effects, such as warming the stratosphere and depleting the ozone layer. We explore the potential benefits of solid alumina and calcite particles as alternatives to sulfate aerosols by using an experimentally informed aerosol-chemistry-climate model. Compared to sulfur dioxide, injection of solids reduces stratospheric warming by up to 70% and diffuse radiation by up to 40%, highlighting their potential benefits. Achieving −1 W m⁻² of radiative forcing would likely result in very small ozone changes, but sizable uncertainties remain. These arise from poorly understood heterogeneous chemical and microphysical processes, which, under less likely assumptions, could lead to larger global ozone column changes between −14% and +4%. Our work provides recommendations for improving the understanding of stratospheric aerosol injection using materials other than sulfur dioxide, and underscores the need for kinetic laboratory studies.