16.11.2017

# New Publications

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Jones, Anthony C.; et al. (2017): Impacts of hemispheric solar geoengineering on tropical cyclone frequency

Jones, Anthony C.; Haywood, James M.; Dunstone, Nick; Emanuel, Kerry; Hawcroft, Matthew K.; Hodges, Kevin I.; Jones, Andy (2017): Impacts of hemispheric solar geoengineering on tropical cyclone frequency. In Nat Comms 8 (1), p. 1382. DOI: 10.1038/s41467-017-01606-0.

"Observations following major volcanic eruptions indicate that aerosol enhancements confined to a single hemisphere effectively modulate North Atlantic tropical cyclone (TC) activity in the following years. Here we investigate the effects of both single-hemisphere and global SAI scenarios on North Atlantic TC activity using the HadGEM2-ES general circulation model and various TC identification methods."

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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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01.11.2017

# New Publications

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Visioni, Daniele; et al. (2017): Quantification of sulfur deposition changes under sulfate geoengineering conditions

Visioni, Daniele; Pitari, Giovanni; Tuccella, Paolo; Curci, Gabriele (2017): Quantification of sulfur deposition changes under sulfate geoengineering conditions. In Atmos. Chem. Phys. Discuss., pp. 1–42. DOI: 10.5194/acp-2017-987.

"In this study we present results from a composition-climate coupled model (ULAQ-CCM) and a chemistry-transport model (GEOS-Chem), assuming a sustained lower stratospheric equatorial injection of 8 Tg-SO2/yr. Total S-deposition is found to globally increase by 5.2 % when sulfate geoengineering is deployed, with a clear interhemispheric asymmetry (3.8 % and 10.3 % in NH and SH, respectively). The latter is mostly due to the combination of a quasi-homogeneous tropospheric influx of sulfate from the stratosphere, and the highly inhomogeneous amount of anthropogenic sulfur emissions in the boundary layer (mostly located in the Northern Hemisphere)."

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29.10.2017

# Media

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Economist: The climate-change experiment (Video)

"Climate-change experts are researching ways to cool down the planet using geoengineering. How could spraying chemicals into the stratosphere help counteract global warming?"

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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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