20.01.2020

# New Publications

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Krishnamohan, K. S.; et al. (2020): The Climatic Effects of Hygroscopic Growth of Sulfate Aerosols in the Stratosphere

Krishnamohan, K. S.; Bala, Govindasamy; Cao, Long; Duan, Lei; Caldeira, Ken (2020): The Climatic Effects of Hygroscopic Growth of Sulfate Aerosols in the Stratosphere. In Earth's Future. DOI: 10.1029/2019EF001326.

"We show that stratospheric sulfate aerosols, for a given mass of sulfates, cause more cooling when prescribed at the lower levels of the stratosphere because of hygroscopic growth. The larger relative humidity in the lower stratosphere causes an increase in the aerosol size through hygroscopic growth which leads to a larger scattering efficiency."

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23.12.2019

# Media

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MIT Technology Review: The US government has approved funds for geoengineering research

"The program includes assessments of “solar climate interventions,” including “proposals to inject material [into the stratosphere] to affect climate.”"

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16.12.2019

# New Publications

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Park, Chang‐Eui; et al. (2019): Inequal Responses of Drylands to Radiative Forcing Geoengineering Methods

Park, Chang‐Eui, Su‐Jong Jeong, Yuanchao Fan, Jerry Tjiputra, Helene Muri, and Chunmiao Zheng (2019): Inequal Responses of Drylands to Radiative Forcing Geoengineering Methods. Geophysical Research Letters, December. https://doi.org/10.1029/2019gl084210.

‌"We show noticeable inequality in the responses of drylands when three radiative forcing geoengineering (RFG) methodologies—cirrus cloud thinning (CCT), marine sky brightening (MSB), and stratospheric aerosol injection (SAI)—individually reduce the radiative forcing of the representative concentration pathway 8.5 scenario using a set of the Norwegian Earth system model (NorESM1‐ME) experiments."

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16.12.2019

# New Publications

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Krishnamohan, Krishna-Pillai Sukumara-Pillai; et al. (2019): Climate System Response to Stratospheric Sulfate Aerosols: Sensitivity to Altitude of Aerosol Layer

Krishnamohan, Krishna-Pillai Sukumara-Pillai, Govindasamy Bala, Long Cao, Lei Duan, and Ken Caldeira (2019): Climate System Response to Stratospheric Sulfate Aerosols: Sensitivity to Altitude of Aerosol Layer. Earth System Dynamics 10 (4): 885–900. https://doi.org/https://doi.org/10.5194/esd-10-885-2019.

‌"In this study, we isolate and assess the sensitivity of stratospheric aerosol radiative forcing and the resulting climate change to the altitude of the aerosol layer. We study this by prescribing a specified amount of sulfate aerosols, of a size typical of what is produced by volcanoes, distributed uniformly at different levels in the stratosphere. We find that stratospheric sulfate aerosols are more effective in cooling climate when they reside higher in the stratosphere."

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13.12.2019

# New Publications

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Klaus, Geraldine; et al. (2019): Psychological factors influencing laypersons’ acceptance of climate engineering, climate change mitigation and business as usual scenarios

Klaus, Geraldine; Ernst, Andreas; Oswald, Lisa (2019): Psychological factors influencing laypersons’ acceptance of climate engineering, climate change mitigation and business as usual scenarios. In Technology in Society, p. 101222. DOI: 10.1016/j.techsoc.2019.101222.

"In July 2017, we assessed public reactions from the German population in a representative online survey. Participants were given a brief text informing them about climate change and one of four different scenarios in a between-subject design (N = 678). Two of the scenarios described the use of climate engineering technologies - stratospheric aerosol injection (SAI) and bio-energy with carbon capture and storage (BECCS) - one of them covered conventional mitigation strategies and the fourth group was given an outline of the business-as-usual (BAU) approach."

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09.12.2019

# New Publications

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Simpson, I.R.; et al. (2019): The Regional Hydroclimate Response to Stratospheric Sulfate Geoengineering and the Role of Stratospheric Heating

Simpson, I. R.; Tilmes, S.; Richter, J. H.; Kravitz, B.; MacMartin, D. G.; Mills, M. J. et al. (2019): The Regional Hydroclimate Response to Stratospheric Sulfate Geoengineering and the Role of Stratospheric Heating. In Journal of Geophysical Research: Atmospheres 124. DOI: 10.1029/2019JD031093.

"Here, a 20‐member ensemble of simulations with the Community Earth System Model with the Whole Atmosphere Community Climate Model as its atmospheric component is used to investigate the projected hydroclimate changes that occur when greenhouse gas‐driven warming, under a high emissions scenario, is offset with stratospheric aerosol geoengineering."

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05.12.2019

# New Publications

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Jiang, J.; et al. (2019): Stratospheric Sulfate Aerosol Geoengineering Could Alter the High Latitude Seasonal Cycle

Jiang, Jiu, Long Cao, Douglas G. MacMartin, Isla R. Simpson, Ben Kravitz, Wei Cheng, Daniele Visioni, Simone Tilmes, Jadwiga H. Richter, and Michael J. Mills (2019): Stratospheric Sulfate Aerosol Geoengineering Could Alter the High Latitude Seasonal Cycle. Geophysical Research Letters, December. https://doi.org/10.1029/2019gl085758.

"Here we use the Stratospheric Aerosol Geoengineering Large Ensemble (GLENS) simulations to explore the effects of SAG on the seasonal cycle of climate change. Simulations show that relative to the present‐day climate, SAG diminishes the amplitude of the seasonal cycle of temperature at many high‐latitude locations, with warmer winters and cooler summers."

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05.12.2019

# New Publications

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Tilmes, S., et al. (2019): Reaching 1.5°C and 2.0°C Global Surface Temperature Targets Using Stratospheric Aerosol Geoengineering

Tilmes, Simone, Douglass E. MacMartin, Jan T. M. Lenaerts, Leo van Kampenhout, Laura Muntjewerf, Lili Xia, Cheryl S. Harrison, et al (2019): Reaching 1.5°C and 2.0°C Global Surface Temperature Targets Using Stratospheric Aerosol Geoengineering. Earth System Dynamics, December 2019. https://doi.org/10.5194/esd-2019-76.

‌"We propose new testbed model experiments for the Geoengineering Model Intercomparison Project (GeoMIP) that are designed to limit global warming to 1.5°C or 2.0°C above 1850–1900 conditions using stratospheric aerosol geoengineering (SAG). "

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11.11.2019

# New Publications

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Schroeder, C.; et al (2019): “Stratospheric Aerosol Injection as a Deep Reinforcement Learning Problem

Schroeder, Christian, and Thomas Hornigold. 2019. “Stratospheric Aerosol Injection as a Deep Reinforcement Learning Problem.” ArXiv.Org. 2019. https://arxiv.org/abs/1905.07366v1.

‌"We suggest treating SAI as a high-dimensional control problem, with policies trained according to a context-sensitive reward function within the Deep Reinforcement Learning (DRL) paradigm. In order to facilitate training in simulation, we suggest to emulate HadCM3, a widely used General Circulation Model, using deep learning techniques. We believe this is the first application of DRL to the climate sciences."

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08.11.2019

# New Publications

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Gryspeerdt, Edward; et al. (2019): The impact of ship emission controls recorded by cloud properties

Gryspeerdt, Edward; Smith, Tristan; O'Keeffe, Eoin; Christensen, Matthew; Goldsworth, Fraser (2019): The impact of ship emission controls recorded by cloud properties. In Geophys. Res. Lett. DOI: 10.1029/2019GL084700.

"This work uses over 17,000 shiptracks during the implementation of fuel sulfur content regulations to demonstrate the central role of sulfate aerosol in ship exhaust for modifying clouds. By connecting individual shiptracks to transponder data, it is shown that almost half of shiptracks are likely undetected, masking a significant contribution to the climate impact of shipping. A pathway to retrieving ship sulfate emissions is demonstrated, showing how cloud observations could be used to monitor air pollution."

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