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MISU Guest Seminar | Ulrike Lohmann

Aerosol and clouds in a changing climate: from the Arctic to global results

by Ulrike Lohmann
Professor at ETH Zurich, Switzerland
Ulrike Lohmann has been appointed an Honorary doctorate at Stockholm University. She will have a seminar on Aerosol and clouds in a changing climate: from the Arctic to global results.

Time: 27 September 2018, 11h15–12h15
Venue: Rossbysalen C609, Arrhenius Laboratory, 6th floor

Future sea ice retreat in the Arctic in summer and autumn is expected to affect both natural and anthropogenic aerosol emissions: sea ice acts as a barrier between the ocean and the atmosphere, and reducing it increases dimethyl sulfide and sea salt emissions. Additionally, a decrease in the area and thickness of sea ice could lead to enhanced Arctic ship traffic, for example due to shorter routes of cargo ships.

Changes in the emissions of aerosol particles can then influence cloud properties, precipitation, surface albedo, and radiation. Next to changes in aerosol emissions, clouds will also be affected by increases in Arctic temperatures and humidities. We found that future Arctic ship emissions related to transport and oil and gas extraction only have an impact on clouds and radiation when their emissions are increased by a factor of 10.

We also assess changes in cloud fields in response to a warming climate using the standard 2-moment cloud microphysics scheme of ECHAM6-HAM2 as well as the new single-ice-category scheme from Dietlicher et al. (2018). While the equilibrium climate sensitivity is not that sensitive to changes in mixed-phase clouds when using our standard scheme, it is significantly larger using the new scheme. I will address possible reasons for this in my talk.



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