The role of the SO2 radiative effect in sustaining the volcanic winter and soothing the Toba impact on climate.

Sergey Osipov, Georgiy L. Stenchikov, Kostas Tsigaridis, Allegra N. LeGrande, Susanne E. Bauer

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15 Scopus citations

Abstract

Volcanic eruptions are an important climate driver. The impact of Pinatubo-sized eruptions has been observed and is well constrained. The magnitude and duration of volcanic winter effects after super-eruptions such as Toba remain disputed due to disagreement between the strong cooling predicted by models, and much milder climate perturbations according to the paleo data. Here we present a re-evaluated climate impact of a Toba-sized super-eruption based on up-to-date GISS ModelE simulations. In this study, we account for all known primary mechanisms that govern the evolution of the volcanic plume and their nonlinear interactions. The SO2 radiative effects are evaluated for the first time in coupled climate simulations with the interactive atmospheric chemistry module. We found that SO2 effects on photochemistry, dynamics, and radiative forcing are especially prominent. Due to strong absorption in ultraviolet, SO2 feedback on photochemistry partially offsets the limiting effect associated with aerosol microphysical processes. SO2 greenhouse warming soothes the radiative cooling exerted by sulfate aerosols. SO2 absorption in the shortwave and longwave causes radiative heating and lofting of the volcanic plume, and boosts the efficiency of SO2 impact on photochemistry. Our analysis shows that SO2 lifetime and magnitude of effects scale up and increase with the amount of emitted material. For a Pinatubo-sized eruption, SO2 feedbacks on chemistry and dynamics are relevant only during the initial stage of the volcanic plume evolution, while local SO2 concentrations are high. For a Toba-sized eruption, SO2 effects are as important as sulfate aerosols, and produce a less extreme volcanic winter.
Original languageEnglish (US)
JournalJournal of Geophysical Research: Atmospheres
Volume125
Issue number2
DOIs
StatePublished - Jan 21 2020

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: The research reported in this publication was supported by funding from King Abdullah University of Science and Technology (KAUST). We thank the KAUST Supercomputing Laboratory for providing computer resources. We thank Karen Cady-Pereira,Eli Mlawer and Mike Iacono from Atmospheric and Environmental Research (AER) for their help in adding SO2 radiative effects into the RRTM, RRTMG standalone models and RRTMG radiation modules for the Weather Research and Forecasting (WRF) model.The ERA-Interim data were obtained from the ECMWF Data Server with 0.75 by 0.75 degree horizontal and 6 hours temporal resolution. The modeling framework and other data necessary to reproduce the simulations are publicly available through KAUST Repository at http://hdl.handle.net/10754/655974 KT and SEB acknowledge support from NASA ACMAP (Atmospheric Composition Modeling and Analysis Program) contract NNX15AE36G. ANL and SEB thank NASAGISS for institutional support.

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