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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01.09.2016

# New Publications

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Davis, Nicholas A.; et al. (2016): Changes in the width of the tropical belt due to simple radiative forcing changes in the GeoMIP simulations

Davis, Nicholas A.; Seidel, Dian J.; Birner, Thomas; Davis, Sean M.; Tilmes, Simone (2016): Changes in the width of the tropical belt due to simple radiative forcing changes in the GeoMIP simulations. In Atmos. Chem. Phys. 16 (15), pp. 10083–10095. DOI 10.5194/acp-16-10083-2016.

"To shed light on robust processes associated with tropical expansion, here we examine how the tropical belt width, as measured by the Hadley cell edges, responds to simplified forcings in the Geoengineering Model Intercomparison Project (GeoMIP). The tropical belt expands in response to a quadrupling of atmospheric carbon dioxide concentrations and contracts in response to a reduction in the solar constant, with a range of a factor of 3 in the response among nine models."

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07.03.2016

# New Publications

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Ferraro, Angus J.; Griffiths, Hannah G. (2016): Quantifying the temperature-independent effect of stratospheric aerosol geoengineering on global-mean precipitation in a multi-model ensemble

"We demonstrate here that stratospheric sulphate aerosol itself also acts to reduce global-mean precipitation independent of its effects on temperature. The temperature-independent effect of stratospheric aerosol geoenginering on global-mean precipitation is calculated by removing temperature-dependent effects from climate model simulations of the Geoengineering Model Intercomparison Project (GeoMIP)."

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19.02.2016

# New Publications

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Kravitz, Ben; et al. (2016): New Paths in Geoengineering

Kravitz, Ben; Robock, Alan; Tilmes, Simone (2016): New Paths in Geoengineering. In Eos 97. DOI 10.1029/2016EO045915.

Meeting report: "National Center for Atmospheric Research Fifth Annual Geoengineering Model Intercomparison Workshop and Early Career Summer School; Boulder, Colorado, 20–24 July 2015"

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28.10.2015

# New Publications

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Kravitz, B.; et al. (2015): The Geoengineering Model Intercomparison Project Phase 6 (GeoMIP6). Simulation design and preliminary results

Kravitz, B.; Robock, A.; Tilmes, S.; Boucher, O.; English, J. M.; Irvine, P. J. et al. (2015): The Geoengineering Model Intercomparison Project Phase 6 (GeoMIP6). Simulation design and preliminary results. In Geosci. Model Dev. 8 (10), pp. 3379–3392. DOI: 10.5194/gmd-8-3379-2015 

"We present a suite of new climate model experiment designs for the Geoengineering Model Intercomparison Project (GeoMIP). This set of experiments, named GeoMIP6 (to be consistent with the Coupled Model Intercomparison Project Phase 6), builds on the previous GeoMIP project simulations, and has been expanded to address several further important topics, including key uncertainties in extreme events, the use of geoengineering as part of a portfolio of responses to climate change, and the relatively new idea of cirrus cloud thinning to allow more longwave radiation to escape to space."

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28.10.2015

# New Publications

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Gabriel, C. J.; Robock, Alan (2015): Stratospheric geoengineering impacts on El Niño/Southern Oscillation

Gabriel, C. J.; Robock, Alan (2015): Stratospheric geoengineering impacts on El Niño/Southern Oscillation. In Atmos. Chem. Phys. 15 (20), pp. 11949–11966. DOI: 10.5194/acp-15-11949-2015 

"To examine the impact of proposed stratospheric geoengineering schemes on the amplitude and frequency of El Niño/Southern Oscillation (ENSO) variations we examine climate model simulations from the Geoengineering Model Intercomparison Project (GeoMIP) G1–G4 experiments. Here we compare tropical Pacific behavior under anthropogenic global warming (AGW) using several scenarios: an instantaneous quadrupling of the atmosphere's CO2 concentration, a 1 % annual increase in CO2 concentration, and the representative concentration pathway resulting in 4.5 W m−2 radiative forcing at the end of the 21st century, the Representative Concentration Pathway 4.5 scenario, with that under G1–G4 and under historical model simulations."

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21.10.2015

# New Publications

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Bürger, Gerd; Cubasch, Ulrich (2015): The detectability of climate engineering

Bürger, Gerd; Cubasch, Ulrich (2015): The detectability of climate engineering. In J. Geophys. Res. Atmos., pp. n/a-n/a. DOI: 10.1002/2015JD023954 

"We assess the detection and attribution (D&A) of climate engineering (CE) as a function of their duration after initiation. We employ “surrogate” climates where observations are mimicked by simulations. Unlike classical, stationary D&A, the null hypothesis for this analysis is the non-stationary gradual warming caused by continued greenhouse gas (GHG) forcing, which creates a number of theoretical and technical complications."

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18.08.2015

# New Publications

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MacMartin, Douglas G.; et al. (2015): On solar geoengineering and climate uncertainty

MacMartin, Douglas G.; Kravitz, Ben; Rasch, Philip J. (2015): On solar geoengineering and climate uncertainty. In Geophys. Res. Lett., pp. n/a. DOI 10.1002/2015GL065391.

"We explore the effects of geoengineering on one source of climate system uncertainty by evaluating the inter-model-spread across 12 climate models participating in the Geoengineering Model Intercomparison project (GeoMIP). The model-spread in simulations of climate change and the model-spread in the response to solar geoengineering are not additive but rather partially cancel."

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