Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 17, 3879-3889, 2017
http://www.atmos-chem-phys.net/17/3879/2017/
doi:10.5194/acp-17-3879-2017
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Review article
21 Mar 2017
Sulfate geoengineering: a review of the factors controlling the needed injection of sulfur dioxide
Daniele Visioni1,2, Giovanni Pitari1, and Valentina Aquila3,4 1Department of Physical and Chemical Sciences, Università dell'Aquila, 67100 L'Aquila, Italy
2CETEMPS, Università dell'Aquila, 67100 L'Aquila, Italy
3GESTAR/Johns Hopkins University, Department of Earth and Planetary Science, 3400 N Charles Street, Baltimore, MD 21218, USA
4NASA Goddard Space Flight Center, Code 614, Greenbelt, MD 20771, USA
Abstract. Sulfate geoengineering has been proposed as an affordable and climate-effective means to temporarily offset the warming produced by the increase of well-mixed greenhouse gases (WMGHGs). This technique would likely have to be applied while and after global intergovernmental measures on emissions of WMGHGs are implemented in order to achieve surface temperature stabilization. The direct radiative effects of sulfur injection in the tropical lower stratosphere can be summarized as increasing shortwave scattering with consequent tropospheric cooling and increasing longwave absorption with stratospheric warming. Indirect radiative effects are related to induced changes in the ozone distribution; stratospheric water vapor abundance,;formation and size of upper-tropospheric cirrus ice particles; and lifetime of long-lived species, namely CH4 in connection with OH changes through several photochemical mechanisms. Direct and indirect effects of sulfate geoengineering both concur to determine the atmospheric response. A review of previous studies on these effects is presented here, with an outline of the important factors that control the amount of sulfur dioxide to be injected in an eventual realization of the experiment. However, we need to take into account that atmospheric models used for these studies have shown a wide range of climate sensitivity and differences in the response to stratospheric volcanic aerosols. In addition, large uncertainties exist in the estimate of some of these aerosol effects.

Citation: Visioni, D., Pitari, G., and Aquila, V.: Sulfate geoengineering: a review of the factors controlling the needed injection of sulfur dioxide, Atmos. Chem. Phys., 17, 3879-3889, doi:10.5194/acp-17-3879-2017, 2017.
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Short summary
This review paper summarizes the state-of-the-art knowledge of the direct and indirect side effects of sulfate geoengineering, that is, the injection of sulfur dioxide into the stratosphere in order to offset the warming caused by the anthropic increase in greenhouse gasses. An overview of the various effects and their uncertainties, using results from published scientific articles, may help fine-tune the best amount of sulfate to be injected in an eventual realization of the experiment.
This review paper summarizes the state-of-the-art knowledge of the direct and indirect side...
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