07.09.2020

# New Publications

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Kravitz, Ben; et al. (2020): Comparing different generations of idealized solar geoengineering simulations in the Geoengineering Model Intercomparison Project (GeoMIP)

Kravitz, Ben; MacMartin, Douglas G.; Visioni, Daniele; Boucher, Olivier; Cole, Jason N. S.; Haywood, Jim et al. (2020): Comparing different generations of idealized solar geoengineering simulations in the Geoengineering Model Intercomparison Project (GeoMIP). In Atmospheric Chemistry and Physics (under review). DOI: 10.5194/acp-2020-732.

"Two generations of models in the Geoengineering Model Intercomparison Project (GeoMIP) have now simulated offsetting a quadrupling of the CO2 concentration with solar reduction. This simulation is artificial and designed to elicit large responses in the models. Here we show that energetics, temperature, and hydrological cycle changes in this experiment are statistically indistinguishable between the two ensembles."

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24.08.2020

# New Publications

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Jones, Andy; et al. (2020): North Atlantic Oscillation response in GeoMIP experiments G6solar and G6sulfur: why detailed modelling is needed for understanding regional implications of solar radiation management

Jones, Andy; Haywood, Jim M.; Jones, Anthony C.; Tilmes, Simone; Kravitz, Ben; Robock, Alan (2020): North Atlantic Oscillation response in GeoMIP experiments G6solar and G6sulfur: why detailed modelling is needed for understanding regional implications of solar radiation management. In Atmospheric Chemistry and Physics. DOI: 10.5194/acp-2020-802. (in review)

"Proposed SRM schemes aim to increase planetary albedo to reflect more sunlight back to space and induce a cooling that acts to partially offset global warming. Under the auspices of the Geoengineering Model Intercomparion Project, we have performed model experiments whereby global temperature under the high forcing SSP5–8.5 scenario is reduced to follow that of the medium forcing SSP2–4.5 scenario."

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01.07.2020

# Media

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Harvard SGRP Blog: Ten Years of GeoMIP (Ben Kravitz)

"On this tenth anniversary, I thought it would be interesting to look back at that original GeoMIP paper and see how my thinking has evolved over the past decade."

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18.05.2020

# New Publications

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Chen, Yating; et al. 2020: “Mitigation of Arctic Permafrost Carbon Loss through Stratospheric Aerosol Geoengineering.”

Chen, Yating, Aobo Liu, and John C. Moore. 2020: “Mitigation of Arctic Permafrost Carbon Loss through Stratospheric Aerosol Geoengineering.” Nature Communications 11 (1). https://doi.org/10.1038/s41467-020-16357-8.

‌"Increasing Earth’s albedo by the injection of sulfate aerosols into the stratosphere has been proposed as a way of offsetting some of the adverse effects of climate change. We examine this hypothesis in respect of permafrost carbon-climate feedbacks using the PInc-PanTher process model driven by seven earth system models running the Geoengineering Model Intercomparison Project (GeoMIP) G4 stratospheric aerosol injection scheme to reduce radiative forcing under the Representative Concentration Pathway (RCP) 4.5 scenario."

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04.07.2018

# New Publications

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Wang, Qin; et al. (2018): A statistical examination of the effects of stratospheric sulfate geoengineering on tropical storm genesis.

Wang, Qin; Moore, John C.; Ji, Duoying (2018): A statistical examination of the effects of stratospheric sulfate geoengineering on tropical storm genesis. In: Atmos. Chem. Phys 18 (13), S. 9173–9188. DOI: 10.5194/acp-18-9173-2018.

"The thermodynamics of the ocean and atmosphere partly determine variability in tropical cyclone (TC) numberand intensity and are readily accessible from climate model output, but an accurate description of TC variability requiresmuch higher spatial and temporal resolution than the models used in the GeoMIP (Geoengineering Model Intercomparison Project) experiments provide. The genesis potential index (GPI) and ventilation index (VI) are combinations of dynamic and thermodynamic variables that provide proxiesfor TC activity under different climate states. Here we use five CMIP5 models that have run the RCP4.5 experiment and the GeoMIP stratospheric aerosol injection (SAI) G4 experiment to calculate the two TC indices over the 2020 to 2069 period across the six ocean basins that generate TCs."

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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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