The Sensitivity of Polar Ozone Depletion to Proposed Geoengineering Schemes

Tilmes, Simone; Müller, Rolf; Salawitch, R. J.

doi:10.1126/science.1153966

Cited by 254 publications

(256 citation statements)

References 14 publications

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“…The described reduction in meridional transport of sulfate may also be true for ozone and the stratospheric ozone concentration could be reduced in the extratropics. This reduction would add to the proposed reduction of ozone due to chemical reactions (Tilmes et al, 2008). Pitari et al (2016) discuss the impact of volcanic aerosol on stratospheric dynamical processes and calculate a reduction of approximately 10 % of the extratropical mass flux of NO 2 and CH 4 after the eruption of Mt.…”

Section: Discussionmentioning

confidence: 99%

Changing transport processes in the stratosphere by radiative heating of sulfate aerosols

2017

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Abstract. The injection of sulfur dioxide (SO 2 ) into the stratosphere to form an artificial stratospheric aerosol layer is discussed as an option for solar radiation management. Sulfate aerosol scatters solar radiation and absorbs infrared radiation, which warms the stratospheric sulfur layer. Simulations with the general circulation model ECHAM5-HAM, including aerosol microphysics, show consequences of this warming, including changes of the quasi-biennial oscillation (QBO) in the tropics. The QBO slows down after an injection of 4 Tg(S) yr −1 and completely shuts down after an injection of 8 Tg(S) yr −1 . Transport of species in the tropics and subtropics depends on the phase of the QBO. Consequently, the heated aerosol layer not only impacts the oscillation of the QBO but also the meridional transport of the sulfate aerosols. The stronger the injection, the stronger the heating and the simulated impact on the QBO and equatorial wind systems. With increasing injection rate the velocity of the equatorial jet streams increases, and the less sulfate is transported out of the tropics. This reduces the global distribution of sulfate and decreases the radiative forcing efficiency of the aerosol layer by 10 to 14 % compared to simulations with low vertical resolution and without generated QBO. Increasing the height of the injection increases the radiative forcing only for injection rates below 10 Tg(S) yr −1 (8-18 %), a much smaller value than the 50 % calculated previously. Stronger injection rates at higher levels even result in smaller forcing than the injections at lower levels.

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Section: Discussionmentioning

confidence: 99%

Changing transport processes in the stratosphere by radiative heating of sulfate aerosols

2017

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“…Both mechanisms have been the focus of many recent studies [Rasch et al, 2008;Wang et al, 2011], and several complications have been identified. Examples are changes to the local and regional hydrological cycles [Ricke et al, 2010], as well as stratospheric ozone depletion in the case of stratospheric sulphur injection [Tilmes et al, 2008]. Here we address a climate engineering mechanism that has so far not been tested: the perturbation of cirrus clouds to reduce their lifetime and optical thickness, thereby cooling Earth's climate.…”

Section: Introductionmentioning

confidence: 99%

Cirrus Cloud Seeding has Potential to Cool climate

Storelvmo

Kristjansson

Muri

et al. 2013

Geophys. Res. Lett.

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[1] Cirrus clouds, thin ice clouds in the upper troposphere, have a net warming effect on Earth's climate. Consequently, a reduction in cirrus cloud amount or optical thickness would cool the climate. Recent research indicates that by seeding cirrus clouds with particles that promote ice nucleation, their lifetimes and coverage could be reduced. We have tested this hypothesis in a global climate model with a state-of-the-art representation of cirrus clouds and find that cirrus cloud seeding has the potential to cancel the entire warming caused by human activity from pre-industrial times to present day. However, the desired effect is only obtained for seeding particle concentrations that lie within an optimal range. With lower than optimal particle concentrations, a seeding exercise would have no effect. Moreover, a higher than optimal concentration results in an over-seeding that could have the deleterious effect of prolonging cirrus lifetime and contributing to global warming. Citation: Storelvmo T., J.

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“…Some commentators have suggested replacing the declining blanket of cooling sulphate aerosols in the Arctic troposphere with a deliberate injection of sulphate (or other cooling aerosol) into the Arctic stratosphere (Caldeira and Wood 2008). The amount of sulphate required would be much less (as the aerosol has a much longer lifetime in the stratosphere), but the side-effects include ozone depletion (Tilmes et al 2008). Also, returning annual mean Arctic temperatures towards e.g.…”

Section: Discussion: Risks and Responsesmentioning

confidence: 99%

Arctic Climate Tipping Points

Lenton

2012

AMBIO

142

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There is widespread concern that anthropogenic global warming will trigger Arctic climate tipping points. The Arctic has a long history of natural, abrupt climate changes, which together with current observations and model projections, can help us to identify which parts of the Arctic climate system might pass future tipping points. Here the climate tipping points are defined, noting that not all of them involve bifurcations leading to irreversible change. Past abrupt climate changes in the Arctic are briefly reviewed. Then, the current behaviour of a range of Arctic systems is summarised. Looking ahead, a range of potential tipping phenomena are described. This leads to a revised and expanded list of potential Arctic climate tipping elements, whose likelihood is assessed, in terms of how much warming will be required to tip them. Finally, the available responses are considered, especially the prospects for avoiding Arctic climate tipping points.

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The Sensitivity of Polar Ozone Depletion to Proposed Geoengineering Schemes

Cited by 254 publications

References 14 publications

Changing transport processes in the stratosphere by radiative heating of sulfate aerosols

Changing transport processes in the stratosphere by radiative heating of sulfate aerosols

Cirrus Cloud Seeding has Potential to Cool climate

Arctic Climate Tipping Points

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