Gordon, H orcid.org/0000-0002-1822-3224, Sengupta, K, Rap, A orcid.org/0000-0002-2319-6769 et al. (78 more authors) (2016) Reduced anthropogenic aerosol radiative forcing caused by biogenic new particle formation. Proceedings of the National Academy of Sciences, 113 (43). pp. 12053-12058. ISSN 0027-8424
Abstract
The magnitude of aerosol radiative forcing caused by anthropogenic emissions depends on the baseline state of the atmosphere under pristine preindustrial conditions. Measurements show that particle formation in atmospheric conditions can occur solely from biogenic vapors. Here, we evaluate the potential effect of this source of particles on preindustrial cloud condensation nuclei (CCN) concentrations and aerosol-cloud radiative forcing over the industrial period. Model simulations show that the pure biogenic particle formation mechanism has a much larger relative effect on CCN concentrations in the preindustrial atmosphere than in the present atmosphere because of the lower aerosol concentrations. Consequently, preindustrial cloud albedo is increased more than under present day conditions, and therefore the cooling forcing of anthropogenic aerosols is reduced. The mechanism increases CCN concentrations by 20-100% over a large fraction of the preindustrial lower atmosphere, and the magnitude of annual global mean radiative forcing caused by changes of cloud albedo since 1750 is reduced by 0.22 W m-2 (27%) to -0.60 W m-2. Model uncertainties, relatively slow formation rates, and limited available ambient measurements make it difficult to establish the significance of a mechanism that has its dominant effect under preindustrial conditions. Our simulations predict more particle formation in the Amazon than is observed. However, the first observation of pure organic nucleation has now been reported for the free troposphere. Given the potentially significant effect on anthropogenic forcing, effort should be made to better understand such naturally driven aerosol processes.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | This is an author produced version of a paper published in Proceedings of the National Academy of Sciences. Uploaded in accordance with the publisher's self-archiving policy. In order to comply with the publisher requirements the University does not require the author to sign a non-exclusive licence for this paper. |
Keywords: | aerosol; biogenic; forcing; climate |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Inst for Climate & Atmos Science (ICAS) (Leeds) |
Funding Information: | Funder Grant number EU - European Union 603445 EU - European Union 316662 |
Depositing User: | Symplectic Publications |
Date Deposited: | 11 Nov 2016 14:32 |
Last Modified: | 02 Jul 2019 15:37 |
Published Version: | https://doi.org/10.1073/pnas.1602360113 |
Status: | Published |
Publisher: | National Academy of Sciences |
Identification Number: | 10.1073/pnas.1602360113 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:107267 |