19.10.2020

# New Publications

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Wolf, Martin J.; et al. (2020): A biogenic secondary organic aerosol source of cirrus ice nucleating particles

Wolf, Martin J.; Zhang, Yue; Zawadowicz, Maria A.; Goodell, Megan; Froyd, Karl; Freney, Evelyn et al. (2020): A biogenic secondary organic aerosol source of cirrus ice nucleating particles. In Nat Comms 11 (1), p. 4834. DOI: 10.1038/s41467-020-18424-6.

"Atmospheric ice nucleating particles (INPs) influence global climate by altering cloud formation, lifetime, and precipitation efficiency. The role of secondary organic aerosol (SOA) material as a source of INPs in the ambient atmosphere has not been well defined. Here, we demonstrate the potential for biogenic SOA to activate as depositional INPs in the upper troposphere by combining field measurements with laboratory experiments."

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30.04.2020

# New Publications

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Duan, Lei; et al. 2020: “A Model‐Based Investigation of Terrestrial Plant Carbon Uptake Response to Four Radiation Modification Approaches.”

Duan, Lei, Long Cao, Govindasamy Bala, and Ken Caldeira. 2020: “A Model‐Based Investigation of Terrestrial Plant Carbon Uptake Response to Four Radiation Modification Approaches.” Journal of Geophysical Research: Atmospheres 125 (9). https://doi.org/10.1029/2019jd031883.

"Using the National Center for Atmospheric Research Community Earth System Model, we performed simulations that represent four idealized radiation modification options: solar constant reduction, sulfate aerosol increase (SAI), marine cloud brightening, and cirrus cloud thinning (CCT)."

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05.02.2020

# New Publications

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Gasparini, Blaž; et al. (2020): To what extent can cirrus cloud seeding counteract global warming?

Gasparini, Blaž; McGraw, Zachary; Storelvmo, Trude; Lohmann, Ulrike (2020): To what extent can cirrus cloud seeding counteract global warming? In Environ. Res. Lett. DOI: 10.1088/1748-9326/ab71a3.

"Previous studies that analyzed modifications of cirrus clouds by seeding of ice nucleating particles showed large uncertainties in both cloud and surface climate responses, ranging from no effect or even a small warming to a globally averaged cooling of about 2.5°C. We use two general circulation models that showed very different responses in previous studies, ECHAM6-HAM and CESM-CAM5, to determine which radiative and climatic responses to cirrus cloud seeding in a 1.5 x CO2 world are common and which are not."

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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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29.07.2019

# New Publications

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Gruber, S.; et al. (2019): A Process Study on Thinning of Arctic Winter Cirrus Clouds With High‐Resolution ICON‐ART Simulations

Gruber, S.; Blahak, U.; Haenel, F.; Kottmeier, C.; Leisner, T.; Muskatel, H. et al. (2019): A Process Study on Thinning of Arctic Winter Cirrus Clouds With High‐Resolution ICON‐ART Simulations. In: J. Geophys. Res. Atmos. 498 (21), S. 339. DOI: 10.1029/2018JD029815.

"In this study, cloud‐resolving simulations of a case study for a limited area of the hibernal Arctic were performed with the atmospheric modeling system ICON‐ART (ICOsahedral Nonhydrostatic‐Aerosol and Reactive Trace gases). A thorough comparison with data both from satellite as well as aircraft measurement is presented to validate the simulations. In addition, the model is applied to clarify the microphysical processes occurring when introducing artificial aerosol particles into the upper troposphere with the aim of modifying cirrus clouds in the framework of climate engineering."

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30.06.2019

# New Publications

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Bock, L.; et al. (2019): Contrail cirrus radiative forcing for future air traffic

Bock, L.; Burkhardt, U. (2019): Contrail cirrus radiative forcing for future air traffic. In: Atmos. Chem. Phys 19 (12), S. 8163–8174. DOI: 10.5194/acp-19-8163-2019.

"The climate impact of air traffic is to a large degree caused by changes in cirrus cloudiness resulting from the formation of contrails. Contrail cirrus radiative forcing is expected to increase significantly over time due to the large projected increases in air traffic. We use ECHAM5-CCMod, an atmospheric climate model with an online contrail cirrus parameterization including a microphysical two-moment scheme, to investigate the climate impact of contrail cirrus for the year 2050."

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30.09.2018

# Media

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livemint: Opinion | The risk of planetary geoengineering

"In 1991, when Mount Pinatubo in the Philippines erupted, it spewed over 20 million tonnes of sulphur into the upper atmosphere. Shortly thereafter we began to witness a strange phenomenon. The sulphates in the stratosphere were acting as a sort of a sun visor, shielding the earth from the sun’s rays and reducing global temperatures by nearly half a degree Celsius by the end of the year."

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25.07.2017

# New Publications

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Cao, Long; et al. (2017): Simultaneous stabilization of global temperature and precipitation through cocktail geoengineering

Cao, Long; Duan, Lei; Bala, Govindasamy; Caldeira, Ken (2017): Simultaneous stabilization of global temperature and precipitation through cocktail geoengineering. In Geophys. Res. Lett. 37 (D6), p. 117. DOI: 10.1002/2017GL074281.

"Here we investigate the possibility of stabilizing both global mean temperature and precipitation simultaneously by combining two geoengineering approaches: stratospheric sulfate aerosol increase (SAI) that deflects sunlight to space and cirrus cloud thinning (CCT) that enables more longwave radiation to escape to space."

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24.07.2017

# Media

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Newsweek: Climate Change and Geoengineering: Artificially Cooling Planet Earth by Thinning Cirrus Clouds

"Over recent decades, scientists from across the globe have been discussing the potential of geoengineering—the deliberate manipulation of the environment that could, in theory, cool the planet and help stabilize the climate."

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24.07.2017

# Media

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Live Science: Cool the Planet? Geoengineering Is Easier Said Than Done

""If cirrus clouds behave like a blanket around the Earth, you're trying to get rid of that blanket," Lohmann, a professor of experimental atmospheric physics at ETH Zurich, told Live Science."

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