Journal Article

Enhanced light absorption by mixed source black and brown carbon particles in UK winter

Prévôt, André S. H., Herndon, Scott C., Dubey, Manvendra K., Worsnop, Douglas R., Liu, Dantong, Onasch, Timothy B., Mohr, Claudia, Xu, Lu, Massoli, Paola, Liu, Shang, Jayne, John T., Williams, Leah R., Fortner, Edward C., Mazzoleni, Claudio, China, Swarup, Sharma, Noopur, Allan, James D., Ng, Nga L., Gorkowski, Kyle, Chhabra, Puneet S., Fleming, Zoë L., Szidat, Sönke, Aiken, Allison C., Cappa, Christopher D., Brooks, William A., Lee, James D., Zotter, Peter

2015

Overview

Black carbon (BC) and light-absorbing organic carbon (brown carbon, BrC) play key roles in warming the atmosphere, but the magnitude of their effects remains highly uncertain. Theoretical modelling and laboratory experiments demonstrate that coatings on BC can enhance BC’s light absorption, therefore many climate models simply assume enhanced BC absorption by a factor of ∼1.5. However, recent field observations show negligible absorption enhancement, implying models may overestimate BC’s warming. Here we report direct evidence of substantial field-measured BC absorption enhancement, with the magnitude strongly depending on BC coating amount. Increases in BC coating result from a combination of changing sources and photochemical aging processes. When the influence of BrC is accounted for, observationally constrained model calculations of the BC absorption enhancement can be reconciled with the observations. We conclude that the influence of coatings on BC absorption should be treated as a source and regionally specific parameter in climate models. Uncertainties in the absorptive properties of black and brown carbon particles limit our understanding of their warming potential. Following an extensive field campaign, Liu et al . report that the magnitude of warming is dependent on particle coatings, which vary due to source and photochemical aging.

• Publisher: Nature Publishing Group UK,Nature Publishing Group,Nature Pub. Group
• Subject: 704/106/35 / 704/106/694/2739 / Absorption / Aging / Atmospheric models / Black carbon / Carbon / Climate models / Coatings / Electromagnetic absorption / ENVIRONMENTAL SCIENCES / Humanities and Social Sciences / multidisciplinary / Organic carbon / Photochemicals / Science / Science (multidisciplinary)