Characterising the long-term effects of stratospheric aerosol injection geoengineering on the stratospheric ozone layer with mid-infrared limb emission sounding instruments

Abstract. Stratospheric aerosol injection (SAI) has been proposed as a potential method to counteract anthropogenic greenhouse gas–driven global warming but it may perturb the stratospheric ozone layer. Here, we use existing SAI scenario simulations as pseudo-reality (PR) input to assess how a future mid-infrared limb-emission sounding observing system would characterise its modelled ozone response. Our PR scenarios were generated using CESM2(WACCM6) simulations following the SSP5-34-OS overshoot pathway, with and without SAI. Pseudo-observations (PO) of a future instrument, modelled around the satellite mission concept CAIRT (the Changing-Atmosphere Infra-Red Tomography explorer), were generated using mission performance simulators, providing full error propagation and spatial smoothing characteristics. Our results demonstrate that a CAIRT-like mission can monitor and quantitatively characterise global, regional and seasonal ozone impacts associated with this SAI scenario. The parent PR fields used here contain a modelled SAI-induced ozone response, including: a) a pronounced additional depletion of total column ozone in the southern hemispheric high latitudes, with austral springtime reductions exceeding 20 DU between 2033–2062, consistent with enhanced heterogeneous halogen activation on sulphate aerosols, b) a delay in Antarctic ozone recovery, and c) a moderate ozone increase in winter and spring at northern hemispheric mid and high latitudes, associated with altered transport and weakened subtropical jets. All these different decadal impacts of SAI interventions are observable with CAIRT PO and are fully distinguishable from a baseline non-SAI scenario. These findings highlight the importance of advanced satellite observations, which are not available nowadays, to monitor and evaluate these impacts.