Preprints
https://doi.org/10.5194/acp-2021-813
https://doi.org/10.5194/acp-2021-813

  11 Oct 2021

11 Oct 2021

Review status: this preprint is currently under review for the journal ACP.

A novel approach to sulfate geoengineering with surface emissions of carbonyl sulfide

Ilaria Quaglia1, Daniele Visioni2, Giovanni Pitari1, and Ben Kravitz3,4 Ilaria Quaglia et al.
  • 1Department of Physical and Chemical Sciences, Universitá dell’Aquila, 67100 L’Aquila, Italy
  • 2Sibley School for Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY 14853, USA
  • 3Department of Earth and Atmospheric Science, Indiana University, Bloomington, IN, USA
  • 4Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, WA, USA

Abstract. Sulfate geoengineering (SG) methods based on lower stratospheric tropical injection of sulfur dioxide (SO2) have been widely discussed in recent years, focusing on the direct and indirect effects they would have on the climate system. Here a potential alternative method is discussed, where sulfur emissions are located at the surface in the form of carbonyl sulfide (COS) gas. A time-dependent chemistry-climate model experiment is designed from year 2021 to 2055, assuming a 40 Tg-S/yr artificial global flux of COS, geographically distributed following the present day anthropogenic COS surface emissions. The budget of COS and sulfur species is discussed, as well as the effects of SG-COS on the stratospheric sulfate aerosol optical depth (Δ τ = 0.080 in years 2046–2055), aerosol effective radius (0.46 μm), surface SOx deposition (+8.7 %) and tropopause radiative forcing (RF) (−2.0 W/m2 for clear sky conditions and −1.5 W/m2 including the cloud adjustment). Indirect effects on ozone, methane and stratospheric water vapor are also considered, along with the COS direct contribution (with an overall gas phase global radiative forcing of +0.23 W/m2). According to our model results, the resulting net RF of this SG-COS experiment is −1.3 W/m2 for the year 2050, and it is comparable to the corresponding RF of −1.7 W/m2 obtained with a sustained injection of 4 Tg-S/yr in the tropical lower stratosphere in the form of SO2 (SG-SO2, able to produce a comparable increase of the sulfate aerosol optical depth). Significant changes of the stratospheric ozone response are found in SG-COS with respect to SG-SO2 (+4.9 DU versus +1.5 DU, globally). According to the model results, the resulting UVB perturbation at the surface accounts to −4.3 % as a global-annual average (versus −2.4 % in the SG-SO2 case), with a springtime Antarctic decrease of −2.7 % (versus a +5.8 % increase in the SG-SO2 experiment). Overall, we find that an increase in COS surface emission may be feasible, and produce a more latitudinally-uniform forcing without the need for the deployment of stratospheric aircrafts.

Ilaria Quaglia et al.

Status: open (until 01 Dec 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Ecosystem impacts of elevated OCS', M.E. Whelan, 14 Oct 2021 reply
  • RC1: 'Comment on acp-2021-813', Anonymous Referee #1, 25 Nov 2021 reply

Ilaria Quaglia et al.

Ilaria Quaglia et al.

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Short summary
Carbonyl sulfide is a gas that mixes very well in the atmosphere, and can reach the stratosphere where it reacts with sunlight and produces aerosol. Here we propose that, by increasing surface fluxes by an order of magnitude, the amount of stratospheric aerosols produced may be enough to partially offset the warming produced by greenhouse gases. We explore what effect this would have on the atmospheric composition.
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