The enhanced capabilities of mid-infrared limb emission sounding to observe stratospheric aerosol injection geoengineering

Using a model-based pseudo-reality (PR) future scenario and realistic pseudo-observations (POs) representative for a proposed satellite mission concept (CAIRT – the Changing-Atmosphere Infra-Red Tomography explorer), we analyse the capabilities of a high-spectral-resolution limb-emission sounding technique to detect and quantitatively monitor very weak stratospheric aerosol injections (SAI) geoengineering deployments, in terms of the injected sulphur dioxide (SO$_2$) and its evolution into sulphate aerosols (SA). Our results suggest that this technique would detect SO2 injections, at the horizontal and vertical scale, within hours to a few days since the SAI deployment. This concept would quantify the SO$_2$ injected mass, even for injections of the order of magnitude of a few hundreds of tonnes of SO$_2$ per day, characteristic of “near-term” to “mid-term” experiments feasible even unilaterally, or in the context of small-scale outdoor experiments, with presently existing technology and at relatively low cost. In addition, our results suggest that this concept would be able to track the temporal evolution of the subsequently formed SA, as it spreads zonally and then toward higher latitudes through meridional dispersion, and to monitor changes in its vertical distribution over time through processes like self-lofting of the resulting SA plume. ... mehrExisting satellite instruments, e.g. based on limb scattering, solar occultation, nadir observations and space LiDARs, do not have the capability to carry out such strategical observations of SAI. Our results stress the importance of increasing our global observational capabilities with high-spectral-resolution limb-emission satellite instruments, a capability not available at present and not foreseen in the near future.