Stratospheric dynamics and midlatitude jets under geoengineering with space mirrors and sulfate and titania aerosols

A J Ferraro,E J Highwood,A J Charlton‐Perez

doi:10.1002/2014jd022734

A J Ferraro, E J Highwood + Show 1 more

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https://doi.org/10.1002/2014jd022734

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Abstract

AbstractThe impact on the dynamics of the stratosphere of three approaches to geoengineering by solar radiation management is investigated using idealized simulations of a global climate model. The approaches are geoengineering with sulfate aerosols, titania aerosols, and reduction in total solar irradiance (representing mirrors placed in space). If it were possible to use stratospheric aerosols to counterbalance the surface warming produced by a quadrupling of atmospheric carbon dioxide concentrations, tropical lower stratospheric radiative heating would drive a thermal wind response which would intensify the stratospheric polar vortices. In the Northern Hemisphere this intensification results in strong dynamical cooling of the polar stratosphere. Northern Hemisphere stratospheric sudden warming events become rare (one and two in 65 years for sulfate and titania, respectively). The intensification of the polar vortices results in a poleward shift of the tropospheric midlatitude jets in winter. The aerosol radiative heating enhances the tropical upwelling in the lower stratosphere, influencing the strength of the Brewer‐Dobson circulation. In contrast, solar dimming does not produce heating of the tropical lower stratosphere, and so there is little intensification of the polar vortex and no enhanced tropical upwelling. The dynamical response to titania aerosol is qualitatively similar to the response to sulfate.

Highlights

IntroductionThe prospect of intentional manipulation of the Earth’s climate, termed geoengineering (or climate engineering), has received some interest in recent years as human emissions of greenhouse gases have continued unabated and climate model projections suggest that global mean surface warming will continue into the 21st century under most emissions scenarios [Knutti and Sedlácek, 2012]
The prospect of intentional manipulation of the Earth’s climate, termed geoengineering, has received some interest in recent years as human emissions of greenhouse gases have continued unabated and climate model projections suggest that global mean surface warming will continue into the 21st century under most emissions scenarios [Knutti and Sedlácek, 2012]
This study presents climate model simulations of the impact on the stratospheric dynamics of different solar radiation management geoengineering techniques

Summary

Introduction

The prospect of intentional manipulation of the Earth’s climate, termed geoengineering (or climate engineering), has received some interest in recent years as human emissions of greenhouse gases have continued unabated and climate model projections suggest that global mean surface warming will continue into the 21st century under most emissions scenarios [Knutti and Sedlácek, 2012]. One approach to geoengineering is to reduce the amount of solar radiation absorbed by the Earth system, an approach called solar radiation management (SRM). This could theoretically be achieved by, for example, placing reflectors at a Lagrange point between the Earth and the Sun [Angel, 2006] or adding aerosols to the stratosphere [Rasch et al, 2008]. SRM approaches have received considerable interest because of the potentially large and rapid surface cooling achievable [Lenton and Vaughan, 2009]. SRM poses potential risks [Robock et al, 2009]. It is important to quantify the climate response to SRM in order to appropriately characterize these risks

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