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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2017-987
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
01 Nov 2017
Review status
This discussion paper is a preprint. A revision of this manuscript was accepted for the journal Atmospheric Chemistry and Physics (ACP) and is expected to appear here in due course.
Quantification of sulfur deposition changes under sulfate geoengineering conditions
Daniele Visioni1,2, Giovanni Pitari1, Paolo Tuccella1,2, and Gabriele Curci1,2 1Department of Physical and Chemical Sciences, Universitá dell’Aquila, 67100 L’Aquila, Italy
2CETEMPS, Universitá dell’Aquila, 67100 L’Aquila, Italy
Abstract. Sustained injection of sulfur dioxide (SO2) in the tropical lower stratosphere has been proposed as a climate engineering technique with the purpose of temporarily mitigating the surface warming predicted for the coming decades. Among several possible environmental side effects, the increase of sulfur deposition at the ground surface still needs to be thoroughly investigated. In this study we present results from a composition-climate coupled model (ULAQ-CCM) and a chemistry-transport model (GEOS-Chem), assuming a sustained lower stratospheric equatorial injection of 8 Tg-SO2/yr. Total S-deposition is found to globally increase by 5.2 % when sulfate geoengineering is deployed, with a clear interhemispheric asymmetry (3.8 % and 10.3 % in NH and SH, respectively). The latter is mostly due to the combination of a quasi-homogeneous tropospheric influx of sulfate from the stratosphere, and the highly inhomogeneous amount of anthropogenic sulfur emissions in the boundary layer (mostly located in the Northern Hemisphere). The two models show good consistency in their sulfur species behavior under background and geoengineering conditions, not only for global and hemispheric budgets but also for regional S-deposition values (except over Arctic and Africa). The consistency between models is not limited to time averaged values, but it extends to monthly and inter-annual deposition changes. The latter is driven essentially by the variability of stratospheric large-scale transport associated to the quasi-biennial oscillation (QBO). According to model-mean values, geoengineering S-deposition percent changes on polar regions range between 7.7 ± 0.7 % over Antarctica and 8.5 ± 1.3 % over the Arctic, where the uncertainty reflects the model-averaged interannual variability. Similar S-deposition changes are found over quasi-clean continental regions of the Southern Hemisphere, and smaller values are calculated over polluted continental regions of the Northern Hemisphere (2 ÷ 4 %). The largest difference between the two models is found over Africa and the Arctic (11 % and 2 %, respectively, for GEOS-Chem, against 2 % and 15 %, respectively, for ULAQ-CCM).

Citation: Visioni, D., Pitari, G., Tuccella, P., and Curci, G.: Quantification of sulfur deposition changes under sulfate geoengineering conditions, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-987, in review, 2017.
Daniele Visioni et al.
Daniele Visioni et al.

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Short summary
Sulfate geoengineering is a proposed technique that would mimic explosive volcanic eruptions by injecting sulfur dioxide (SO2) in the stratosphere in order to counteract global warming produce by greenhouse gases by reflecting part of the incoming solar radiation. In this study we simulate using two models how the aerosols would react to dynamical changes in the stratosphere and how this would affect the deposition of sulfate at the surface.
Sulfate geoengineering is a proposed technique that would mimic explosive volcanic eruptions by...
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