November 2017

09.11.2017

# Media

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McClatchy: We can brighten clouds to reflect heat and reduce global warming. But should we?

"“We think SRN could buy time for other (carbon-reduction) measures to be put in place,” said Philip J. Rasch, chief climate scientist for the Pacific Northwest National Laboratory in Richland, Washington."

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09.11.2017

# Political Papers

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Various scientists: A Letter Regarding U.S. House Hearing on Geoengineering Research

"The Forum for Climate Engineering Assessment drafted and organized the following letter regarding a November 8, 2017 U.S House of Representatives Subcommittee on Environment and Subcommittee on Energy Hearing – Geoengineering: Innovation, Research, and Technology. The letter is signed by 24 prominent voices and thinkers from the geoengineering research, climate policy and the climate advocacy communities."

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09.11.2017

# Media

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MIT Technology Review: Why This Geoengineering Pioneer’s Worst Nightmare Is a Trump Tweet

"Harvard professor David Keith worries that politicians opposed to emissions cuts will “recklessly” promote altering the atmosphere instead."

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08.11.2017

# New Publications

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Mills, Michael J.; et al. (2017): Radiative and chemical response to interactive stratospheric sulfate aerosols in fully coupled CESM1(WACCM)

Mills, Michael J.; Richter, Jadwiga H.; Tilmes, Simone; Kravitz, Ben; MacMartin, Douglas G.; Glanville, Anne A. et al. (2017): Radiative and chemical response to interactive stratospheric sulfate aerosols in fully coupled CESM1(WACCM). In J. Geophys. Res. Atmos. DOI: 10.1002/2017JD027006.

"We present new insights into the evolution and interactions of stratospheric aerosol using an updated version of the Whole Atmosphere Community Climate Model (WACCM). Improved horizontal resolution, dynamics, and chemistry now produce an internally generated quasi-biennial oscillation, and significant improvements to stratospheric temperatures and ozone compared to observations. We present a validation of WACCM column ozone and climate calculations against observations. "

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08.11.2017

# New Publications

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Tilmes, Simone; et al. (2017): Sensitivity of aerosol distribution and climate response to stratospheric SO2 injection locations

Tilmes, Simone; Richter, Jadwiga H.; Mills, Michael J.; Kravitz, Ben; MacMartin, Douglas G.; Vitt, Francis et al. (2017): Sensitivity of aerosol distribution and climate response to stratospheric SO2 injection locations. In J. Geophys. Res. Atmos. DOI: 10.1002/2017JD026888.

"Here, we use CESM1(WACCM) to explore the impact of continuous single grid point SO2 injections at 7 different latitudes and 2 altitudes in the stratosphere on aerosol distribution and climate. For each of the 14 locations, 3 different constant SO2 emission rates were tested to identify linearity in aerosol burden, aerosol optical depth, and climate effects. We found that injections at 15° N and 15° S and at 25 km altitude have equal or greater effect on radiation and surface temperature than injections at the equator."

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08.11.2017

# New Publications

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Richter, Jadwiga H.; et al. (2017): Stratospheric Dynamical Response and Ozone Feedbacks in the Presence of SO2 Injections

Richter, Jadwiga H.; Tilmes, Simone; Mills, Michael J.; Tribbia, Joseph J.; Kravitz, Ben; MacMartin, Douglas G. et al. (2017): Stratospheric Dynamical Response and Ozone Feedbacks in the Presence of SO2 Injections. In J. Geophys. Res. Atmos. DOI: 10.1002/2017JD026912.

"We explore here the stratospheric dynamical response to sulfur dioxide injections ∼ 5 km above the tropopause at multiple latitudes (equator, 15° S, 15° N, 30° S and 30° N) using a fully coupled Earth system model, Community Earth System Model, version 1, with the Whole Atmosphere Community Climate Model as its atmospheric component (CESM1(WACCM)). We find that in all simulations, the tropical lower stratosphere warms primarily between 30° S and 30° N, regardless of injection latitude."

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08.11.2017

# New Publications

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Kravitz, Ben; et al. (2017): First simulations of designing stratospheric sulfate aerosol geoengineering to meet multiple simultaneous climate objective

Kravitz, Ben; MacMartin, Douglas G.; Mills, Michael J.; Richter, Jadwiga H.; Tilmes, Simone; Lamarque, Jean-Francois et al. (2017): First simulations of designing stratospheric sulfate aerosol geoengineering to meet multiple simultaneous climate objectives. In J. Geophys. Res. Atmos. DOI: 10.1002/2017JD026874.

"We describe the first simulations of stratospheric sulfate aerosol geoengineering using multiple injection locations to meet multiple simultaneous surface temperature objectives. Simulations were performed using CESM1(WACCM), a coupled atmosphere-ocean general circulation model with fully interactive stratospheric chemistry, dynamics (including an internally generated quasi-biennial oscillation), and a sophisticated treatment of sulfate aerosol formation, microphysical growth, and deposition."

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08.11.2017

# New Publications

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MacMartin, Douglas G.; et al. (2017): The climate response to stratospheric aerosol geoengineering can be tailored using multiple injection locations

MacMartin, Douglas G.; Kravitz, Ben; Tilmes, Simone; Richter, Jadwiga H.; Mills, Michael J.; Lamarque, Jean-Francois et al. (2017): The climate response to stratospheric aerosol geoengineering can be tailored using multiple injection locations. In J. Geophys. Res. Atmos. DOI: 10.1002/2017JD026868.

"By injecting different amounts of SO2 at multiple different latitudes, the spatial pattern of aerosol optical depth (AOD) can be partially controlled. This leads to the ability to influence the climate response to geoengineering with stratospheric aerosols, providing the potential for design. We use simulations from the fully-coupled whole-atmosphere chemistry-climate model CESM1(WACCM) to demonstrate that by appropriately combining injection at just four different locations, 30° S, 15° S, 15° N, and 30° N, then three spatial degrees of freedom of AOD can be achieved: an approximately spatially-uniform AOD distribution, the relative difference in AOD between Northern and Southern hemispheres, and the relative AOD in high versus low latitudes."

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08.11.2017

# New Publications

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Ahlm, Lars; et al. (2017): Marine cloud brightening – as effective without clouds

Ahlm, Lars; Jones, Andy; Stjern, Camilla W.; Muri, Helene; Kravitz, Ben; Kristjánsson, Jón Egill (2017): Marine cloud brightening – as effective without clouds. In Atmos. Chem. Phys 17 (21), pp. 13071–13087. DOI: 10.5194/acp-17-13071-2017.

"Here we present results from coordinated simulations with three Earth system models (ESMs) participating in the Geoengineering Model Intercomparison Project (GeoMIP) G4sea-salt experiment. Injection rates of accumulation-mode sea spray aerosol particles over ocean between 30° N and 30° S are set in each model to generate a global-mean effective radiative forcing (ERF) of −2.0 W m−2 at the top of the atmosphere. We find that the injection increases the cloud droplet number concentration in lower layers, reduces the cloud-top effective droplet radius, and increases the cloud optical depth over the injection area."

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07.11.2017

# Media

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E&E News: Amid federal climate upheaval, geoengineering options explored

"As the Trump administration looks to withdraw from the international Paris climate agreement and U.S. EPA initiates repealing the Clean Power Plan, a panel of lawmakers plans to explore innovative technologies for reducing the impacts of global warming."

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