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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
07 Oct 2016
Review status
A revision of this discussion paper was accepted for the journal Atmospheric Chemistry and Physics (ACP) and is expected to appear here in due course.
Thermodynamic and dynamic responses of the hydrological cycle to solar dimming
Jane E. Smyth1, Rick D. Russotto2, and Trude Storelvmo1 1Department of Geology & Geophysics, Yale University, New Haven, Connecticut, USA
2Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA
Abstract. The fundamental role of the hydrological cycle in the global climate system motivates thorough evaluation of its responses to climate change and mitigation. The Geoengineering Model Intercomparison Project (GeoMIP) is a global collaboration that aims to assess the climate impacts of solar geoengineering, a proposal to counteract global warming with a reduction of incoming solar radiation. We assess the mechanisms underlying the rainfall response to a simplified simulation of solar dimming in the suite of GeoMIP models and identify robust features. While solar geoengineering restores preindustrial temperatures, the global hydrology is altered. Tropical precipitation changes dominate the response across the model suite. The models indicate a range of possibilities for the hydrological response, and in most cases, both thermodynamic and non-thermodynamic mechanisms drive precipitation minus evaporation changes in the geoengineered simulations relative to the preindustrial. Shifts of the Hadley circulation cells cause greater rainfall anomalies than local changes in relative humidity or the Clausius-Clapeyron scaling of precipitation minus evaporation. The variations among models in the movement of the intertropical convergence zone highlights the need for cautious consideration and continued study before any implementation of solar geoengineering.

Citation: Smyth, J. E., Russotto, R. D., and Storelvmo, T.: Thermodynamic and dynamic responses of the hydrological cycle to solar dimming, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-886, in review, 2016.
Jane E. Smyth et al.
Interactive discussionStatus: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version      Supplement - Supplement
RC1: 'Review of Smyth et al.', Anonymous Referee #1, 19 Oct 2016 Printer-friendly Version 
RC2: 'Nothing new, and poorly diagnosed', Anonymous Referee #2, 30 Oct 2016 Printer-friendly Version Supplement 
AC1: 'AR by Jane E. Smyth on behalf of the Authors (13 Jan. 2017)', Jane Smyth, 13 Jan 2017 Printer-friendly Version Supplement 
Jane E. Smyth et al.
Jane E. Smyth et al.


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Publications Copernicus
Short summary
Geoengineering is a controversial proposal to counteract global warming by reducing the incoming solar radiation. Solar dimming could restore preindustrial temperatures, but global rainfall patterns would be altered. We analyze the global rainfall changes in twelve climate model simulations of solar dimming to better understand the underlying processes. We conclude that tropical precipitation would be substantially altered, primarily due to changes in the large-scale atmospheric circulation.
Geoengineering is a controversial proposal to counteract global warming by reducing the incoming...