13.10.2017

# New Publications

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Zhang, Zhihua; et al. (2017): Impacts of stratospheric aerosol geoengineering strategy on Caribbean coral reefs

Zhang, Zhihua; Jones, Andy; Crabbe, M. James C. (2017): Impacts of stratospheric aerosol geoengineering strategy on Caribbean coral reefs. In Int J of Cl Chan Strat and Man, p. 36. DOI: 10.1108/IJCCSM-05-2017-0104.

" In this study, we model impacts of stratospheric aerosol geoengineering on coral reefs. We will use the HadGEM2-ES climate model to model and evaluate impacts of stratospheric aerosol geoengineering on coral reefs."

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10.10.2017

# New Publications

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Xia, Lili; et al. (2017): Impacts of stratospheric sulfate geoengineering on tropospheric ozone

Xia, Lili; Nowack, Peer J.; Tilmes, Simone; Robock, Alan (2017): Impacts of stratospheric sulfate geoengineering on tropospheric ozone. In Atmos. Chem. Phys 17 (19), pp. 11913–11928. DOI: 10.5194/acp-17-11913-2017.

"Here, we examine the potential effects of stratospheric sulfate aerosols and solar insolation reduction on tropospheric ozone and ozone at Earth's surface. Ozone is a key air pollutant, which can produce respiratory diseases and crop damage. Using a version of the Community Earth System Model from the National Center for Atmospheric Research that includes comprehensive tropospheric and stratospheric chemistry, we model both stratospheric sulfur injection and solar irradiance reduction schemes, with the aim of achieving equal levels of surface cooling relative to the Representative Concentration Pathway 6.0 scenario."

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22.09.2017

# New Publications

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Visioni, Daniele; et al. (2017): Sulfate geoengineering impact on methane transport and lifetime. Results from the Geoengineering Model Intercomparison Project (GeoMIP)

Visioni, Daniele; Pitari, Giovanni; Aquila, Valentina; Tilmes, Simone; Cionni, Irene; Di Genova, Glauco; Mancini, Eva (2017): Sulfate geoengineering impact on methane transport and lifetime. Results from the Geoengineering Model Intercomparison Project (GeoMIP). In Atmos. Chem. Phys 17 (18), pp. 11209–11226. DOI: 10.5194/acp-17-11209-2017.

"Sulfate geoengineering (SG), made by sustained injection of SO2 in the tropical lower stratosphere, may impact the CH4 abundance through several photochemical mechanisms affecting tropospheric OH and hence the methane lifetime. (a) The reflection of incoming solar radiation increases the planetary albedo and cools the surface, with a tropospheric H2O decrease. (b) The tropospheric UV budget is upset by the additional aerosol scattering and stratospheric ozone changes: the net effect is meridionally not uniform, with a net decrease in the tropics, thus producing less tropospheric O(1D). (c) The extratropical downwelling motion from the lower stratosphere tends to increase the sulfate aerosol surface area density available for heterogeneous chemical reactions in the mid-to-upper troposphere, thus reducing the amount of NOx and O3 production. (d) The tropical lower stratosphere is warmed by solar and planetary radiation absorption by the aerosols."

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04.08.2017

# New Publications

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Kleinschmitt, Christoph; et al. (2017): Sensitivity of the radiative forcing by stratospheric sulfur geoengineering to the amount and strategy of the SO2 injection studied with the LMDZ-S3A model

Kleinschmitt, Christoph; Boucher, Olivier; Platt, Ulrich (2017): Sensitivity of the radiative forcing by stratospheric sulfur geoengineering to the amount and strategy of the SO2 injection studied with the LMDZ-S3A model. In Atmos. Chem. Phys. Discuss., pp. 1–34. DOI: 10.5194/acp-2017-722.

"In this study we use the atmospheric general circulation model LMDZ with the sectional aerosol module S3A to determine how the forcing efficiency depends on the injected amount, the injection height and the spatio-temporal pattern of injection. We find that the forcing efficiency may decrease more drastically for larger SO2 injections than previously estimated. As a result, the net instantaneous radiative forcing does not exceed −2 W m−2 for continuous equatorial injections and it decreases (in absolute value) for the largest injection rates simulated (50 Tg S yr−1)."

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25.07.2017

# New Publications

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Cao, Long; et al. (2017): Simultaneous stabilization of global temperature and precipitation through cocktail geoengineering

Cao, Long; Duan, Lei; Bala, Govindasamy; Caldeira, Ken (2017): Simultaneous stabilization of global temperature and precipitation through cocktail geoengineering. In Geophys. Res. Lett. 37 (D6), p. 117. DOI: 10.1002/2017GL074281.

"Here we investigate the possibility of stabilizing both global mean temperature and precipitation simultaneously by combining two geoengineering approaches: stratospheric sulfate aerosol increase (SAI) that deflects sunlight to space and cirrus cloud thinning (CCT) that enables more longwave radiation to escape to space."

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22.07.2017

# New Publications

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Niemeier, Ulrike; Tilmes, Simone (2017): Sulfur injections for a cooler planet

Niemeier, Ulrike; Tilmes, Simone (2017): Sulfur injections for a cooler planet. In: Science (New York, N.Y.) 357 (6348), S. 246–248. DOI: 10.1126/science.aan3317.

"One suggested approach is the artificial reduction of sunlight reaching Earth's surface by increasing the reflectivity of Earth's surface or atmosphere."

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23.06.2017

# New Publications

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Wood, Robert; et al. (2017): Could geoengineering research help answer one of the biggest questions in climate science?

Wood, Robert; Ackerman, Thomas; Rasch, Philip; Wanser, Kelly (2017): Could geoengineering research help answer one of the biggest questions in climate science? In: Earth's Future. DOI: 10.1002/2017EF000601.

"Observational studies show influences of aerosol on clouds, but correlations between aerosol and clouds are insufficient to constrain aerosol forcing because of the difficulty in separating aerosol and meteorological impacts. In this commentary, we argue that this current impasse may be overcome with the development of approaches to conduct control experiments whereby aerosol particle perturbations can be introduced into patches of marine low clouds in a systematic manner. Such cloud perturbation experiments constitute a fresh approach to climate science and would provide unprecedented data to untangle the effects of aerosol particles on cloud microphysics and the resulting reflection of solar radiation by clouds."

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14.06.2017

# New Publications

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Lauvset, Siv K.; et al. (2017): Climate engineering and the ocean. Effects on biogeochemistry and primary production

Lauvset, Siv K.; Tjiputra, Jerry; Muri, Helene (2017): Climate engineering and the ocean. Effects on biogeochemistry and primary production. In: Biogeosciences Discuss., S. 1–36. DOI: 10.5194/bg-2017-235

"Here we use an Earth System Model with interactive biogeochemistry to project future ocean biogeochemistry impacts from large-scale deployment of three different radiation management (RM) climate engineering (also known as geoengineering) methods: stratospheric aerosol injection (SAI), marine sky brightening (MSB), and cirrus cloud thinning (CCT). We apply RM such that the change in radiative forcing in the RCP8.5 emission scenario is reduced to the change in radiative forcing in the RCP4.5 scenario. The resulting global mean sea surface temperatures in the RM experiments are comparable to those in RCP4.5, but there are regional differences."

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02.06.2017

# New Publications

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Zhao, Liyun; et al. (2017): Glacier evolution in high-mountain Asia under stratospheric sulfate aerosol injection geoengineering

Zhao, Liyun; Yang, Yi; Cheng, Wei; Ji, Duoying; Moore, John C. (2017): Glacier evolution in high-mountain Asia under stratospheric sulfate aerosol injection geoengineering. In: Atmos. Chem. Phys. 17 (11), S. 6547–6564. DOI: 10.5194/acp-17-6547-2017 

"We examine this hypothesis for the glaciers in high-mountain Asia using a glacier mass balance model driven by climate simulations from the Geoengineering Model Intercomparison Project (GeoMIP). The G3 and G4 schemes specify use of stratospheric sulfate aerosols to reduce the radiative forcing under the Representative Concentration Pathway (RCP) 4.5 scenario for the 50 years between 2020 and 2069, and for a further 20 years after termination of geoengineering. We estimate and compare glacier volume loss for every glacier in the region using a glacier model based on surface mass balance parameterization under climate projections from three Earth system models under G3, five models under G4, and six models under RCP4.5 and RCP8.5."

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20.05.2017

# New Publications

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Xia, Lili; et al. (2017): Impacts of Stratospheric Sulfate Geoengineering on Tropospheric Ozone

Xia, Lili; Nowack, Peer J.; Tilmes, Simone; Robock, Alan (2017): Impacts of Stratospheric Sulfate Geoengineering on Tropospheric Ozone. In: Atmos. Chem. Phys. Discuss., S. 1–38. DOI: 10.5194/acp-2017-434

"Using a version of the Community Earth System Model from the National Center for Atmospheric Research that includes comprehensive tropospheric and stratospheric chemistry, we model both stratospheric sulfur injection and solar irradiance reduction schemes, with the aim of achieving equal levels of surface cooling relative to the Representative Concentration Pathway 6.0 scenario. This allows us to compare the impacts of sulfate aerosol and solar dimming on atmospheric ozone concentrations."

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