Marine cloud brightening (MCB) is a suggested climate engineering approach to counteract some consequences of global warming on regional and global scales by increasing the amount of shortwave radiation reflected by shallow marine clouds through the seeding of sea salt aerosol particles. However, assessing the potentials, as well as the risks of MCB requires a multiscale perspective, covering not only the intended and unintended large-scale impacts, but also critical small-scale aspects, e.g., the seeded aerosol size distribution or changes in cloud turbulence, which are usually neglected or only crudely parameterized in large-scale assessments. Therefore, a highly detailed representation of aerosol and cloud microphysics is necessary to reduce these uncertainties. In this talk, we will summarize our recent Lagrangian cloud modeling (LCM) studies that allowed us to assess (a) the implications of the seeded aerosol size distribution on the efficacy of MCB, highlighting unintended consequences of adding either too large or too many aerosol particles, (b) implications for radiative transfer calculations, and (c) first results on the impacts of chemical components in the seeded aerosol. Understanding these small-scale aspects is essential for science-based decision-making on MCB and hence its potential realization in the future.

The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)