23.04.2018

# New Publications

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Kravitz, Ben; et al. (2018): The climate effects of increasing ocean albedo. An idealized representation of solar geoengineering

Kravitz, Ben; Rasch, Philip J.; Wang, Hailong; Robock, Alan; Gabriel, Corey; Boucher, Olivier et al. (2018): The climate effects of increasing ocean albedo. An idealized representation of solar geoengineering. In Atmos. Chem. Phys. Discuss., pp. 1–29. DOI: 10.5194/acp-2018-340.

"Marine cloud brightening has been proposed as a means of geoengineering/climate intervention, or deliberately altering the climate system to offset anthropogenic climate change. As an idealized representation of marine cloud brightening, this paper discusses experiment G1ocean-albedo of the Geoengineering Model Intercomparison Project (GeoMIP), involving an abrupt quadrupling of the CO2 concentration and an instantaneous increase in ocean albedo to maintain approximate net top-of-atmosphere radiative flux balance. Eleven Earth System Models are relatively consistent in their temperature, radiative flux, and hydrological cycle responses to this experiment."

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16.04.2018

# New Publications

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Russotto, Rick D.; Ackerman, Thomas P. (2018): Changes in clouds and thermodynamics under solar geoengineering and implications for required solar reduction

Russotto, Rick D.; Ackerman, Thomas P. (2018): Changes in clouds and thermodynamics under solar geoengineering and implications for required solar reduction. In Atmos. Chem. Phys. Discuss., pp. 1–32. DOI: 10.5194/acp-2018-345.

"The amount of solar constant reduction required to offset the global warming from an increase in atmospheric CO2 concentration is an interesting question with implications for assessing the feasibility of solar geoengineering scenarios and for improving our theoretical understanding of Earth's climate response to greenhouse gas and solar forcings. This study investigates this question by analyzing the results of 11 coupled atmosphere-ocean global climate models running Experiment G1 of the Geoengineering Model Intercomparison Project, in which CO2 concentrations are abruptly quadrupled and the solar constant is simultaneously reduced by an amount tuned to maintain top of atmosphere energy balance and preindustrial global mean temperature."

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16.03.2018

# New Publications

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Ji, Duoying; et al. (2018): Extreme temperature and precipitation response to solar dimming and stratospheric aerosol geoengineering

Ji, Duoying; Fang, Songsong; Curry, Charles L.; Kashimura, Hiroki; Watanabe, Shingo; Cole, Jason N. S. et al. (2018): Extreme temperature and precipitation response to solar dimming and stratospheric aerosol geoengineering. In Atmos. Chem. Phys. Discuss., pp. 1–36. DOI: 10.5194/acp-2018-131.

"We examine extreme temperature and precipitation under two potential geoengineering methods forming part of the Geoengineering Model Intercomparison Project (GeoMIP). The solar dimming experiment G1 is designed to completely offset the global mean radiative forcing due to a CO2-quadrupling experiment (abrupt 4 × CO2), while in GeoMIP experiment G4, the radiative forcing due to the representative concentration pathway 4.5 (RCP4.5) scenario is partly offset by a simulated layer of aerosols in the stratosphere. Both G1 and G4 geoengineering simulations lead to lower maximum temperatures at higher latitudes, and on land primarily through feedback effects involving high latitude processes such as snow cover, sea ice and soil moisture."

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27.12.2017

# New Publications

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Kravitz, Ben; Robock, Alan (2017): Vetting New Models of Climate Responses to Geoengineering

Kravitz, Ben; Robock, Alan (2017): Vetting New Models of Climate Responses to Geoengineering. In Eos. DOI: 10.1029/2017EO089383.

"The Seventh Meeting of the Geoengineering Model Intercomparison Project; Newry, Maine, 26 July 2017"

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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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17.07.2017

# 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)

" Sulfate geoengineering, 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."

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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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11.05.2017

# New Publications

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Hong, Yu; et al. (2017): Impact of the GeoMIP G1 sunshade geoengineering experiment on the Atlantic meridional overturning circulation

Hong, Yu; Moore, John C.; Jevrejeva, Svetlana; Ji, Duoying; Phipps, Steven J.; Lenton, Andrew et al. (2017): Impact of the GeoMIP G1 sunshade geoengineering experiment on the Atlantic meridional overturning circulation. In: Environ. Res. Lett. 12 (3). DOI: 10.1088/1748-9326/aa5fb8

"We analyze the multi-earth system model responses of ocean temperatures and the Atlantic Meridional Overturning Circulation (AMOC) under an idealized solar radiation management scenario (G1) from the Geoengineering Model Intercomparison Project. All models simulate warming of the northern North Atlantic relative to no geoengineering, despite geoengineering substantially offsetting the increases in mean global ocean temperatures. Increases in the temperature of the North Atlantic Ocean at the surface (~0.25 K) and at a depth of 500 m (~0.10 K) are mainly due to a 10 Wm−2 reduction of total heat flux from ocean to atmosphere."

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16.01.2017

# New Publications

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Gabriel, Corey J.; et al. (2017): The G4Foam Experiment. Global climate impacts of regional ocean albedo modification

Gabriel, Corey J.; Robock, Alan; Xia, Lili; Zambri, Brian; Kravitz, Ben (2017): The G4Foam Experiment. Global climate impacts of regional ocean albedo modification. In: Atmos. Chem. Phys. 17 (1), S. 595–613. DOI: 10.5194/acp-17-595-2017.

"Here we present the results of climate model simulations of a unique Geoengineering Model Intercomparison Project Testbed experiment to investigate the benefits and risks of a scheme that would brighten certain oceanic regions. The National Center for Atmospheric Research CESM CAM4-Chem global climate model was modified to simulate a scheme in which the albedo of the ocean surface is increased over the subtropical ocean gyres in the Southern Hemisphere."

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16.01.2017

# New Publications

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Kravitz, Ben; et al. (2017): Understanding How Climate Engineering Can Offset Climate Change. Sixth Meeting of the Geoengineering Model Intercomparison Project; Oslo, Norway, 21–22 June 2016

Kravitz, Ben; Robock, Alan; Kristjánsson, Jón (2017): Understanding How Climate Engineering Can Offset Climate Change. Sixth Meeting of the Geoengineering Model Intercomparison Project; Oslo, Norway, 21–22 June 2016. In: Eos. DOI: 10.1029/2016EO005279.

"Participants at a meeting in Oslo, Norway, presented new developments in modeling and simulating climate engineering approaches, including stratospheric aerosols, marine cloud brightening, cirrus thinning, and land and ocean brightening."

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