Effects of black carbon mitigation on Arctic climate

We use the ECHAM-HAMMOZ aerosol-climate model to assess the effects of black carbon (BC) mitigation measures on Arctic climate. To this end we constructed several mitigation scenarios that implement all currently existing legislation and then implement further reductions of BC in a successively incr...

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Bibliographic Details
Published in:Atmospheric Chemistry and Physics
Main Authors: Kuhn, Thomas, Kupiainen, Kaarle, Miinalainen, Tuuli, Kokkola, Harri, Paunu, Ville-Veikko, Laakso, Anton, Tonttila, Juha, Van Dingenen, Rita, Kulovesi, Kati, Karvosenoja, Niko, Lehtonen, Kari E.J.
Format: Article in Journal/Newspaper
Language:English
Published: EGU 2022
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Online Access:http://hdl.handle.net/10138/338549
https://doi.org/10.5194/acp-20-5527-2020
Description
Summary:We use the ECHAM-HAMMOZ aerosol-climate model to assess the effects of black carbon (BC) mitigation measures on Arctic climate. To this end we constructed several mitigation scenarios that implement all currently existing legislation and then implement further reductions of BC in a successively increasing global area, starting from the eight member states of the Arctic Council, expanding to its active observer states, then to all observer states, and finally to the entire globe. These scenarios also account for the reduction of the co-emitted organic carbon (OC) and sulfate (SU). We find that, even though the additional BC emission reductions in the member states of the Arctic Council are small, the resulting reductions in Arctic BC mass burdens can be substantial, especially in the lower troposphere close to the surface. This in turn means that reducing BC emissions only in the Arctic Council member states can reduce BC deposition in the Arctic by about 30 % compared to the current legislation, which is about 60 % of what could be achieved if emissions were reduced globally. Emission reductions further south affect Arctic BC concentrations at higher altitudes and thus only have small additional effects on BC deposition in the Arctic. The direct radiative forcing scales fairly well with the total amount of BC emission reduction, independent of the location of the emission source, with a maximum direct radiative forcing in the Arctic of about −0.4 W m−2 for a global BC emission reduction. On the other hand, the Arctic effective radiative forcing due to the BC emission reductions, which accounts for aerosol–cloud interactions, is small compared to the direct aerosol radiative forcing. This happens because BC- and OC-containing particles can act as cloud condensation nuclei, which affects cloud reflectivity and lifetime and counteracts the direct radiative forcing of BC. Additionally, the effective radiative forcing is accompanied by very large uncertainties that originate from the strong natural variability of ...