GISS Seminar, 2022-10-05: Ewa Bednarz

GISS Lunch Seminar, 2022-10-05

Speaker: Ewa Bednarz (Cornell)
Title: Impacts of geoengineering using stratospheric aerosol injection on the stratospheric and tropospheric climate

Abstract:
The injection of stratospheric aerosol precursor into the lower stratosphere (SAI) has been proposed to mitigate some of the negative impacts of rising greenhouse gas levels. Despite offsetting global mean surface temperature, various studies demonstrated that SAI could influence the recovery of stratospheric ozone and have important impacts on stratospheric and tropospheric circulation, thereby potentially playing an important role in modulating regional and seasonal climate variability. However, so far most of the assessments of such an approach have come from climate model simulations in which SO2 is injected only in the equatorial region and/or under a single emission and SAI scenario. Here I address this using the CESM2-WACCM6 model, a comprehensive Earth System Model with prognostic aerosol microphysics and interactive stratospheric chemistry. Using experiments with varying SAI location or magnitude, I discuss the dependence of the stratospheric and tropospheric response on the latitude of injection and the degree of global mean cooling. I also demonstrate some complications arising from using simplified experiments that reduce the solar constant as analogues for climate impacts from SAI. Overall, the results contribute to an increased understanding of the underlying physical processes and aim to reduce some of the sources of uncertainty in model projections of climate impacts from SAI.