Radiative absorption enhancements due to the mixing state of atmospheric black carbon

Christopher D. Cappa, Timothy B. Onasch, Paola Massoli, Douglas R. Worsnop, Timothy S. Bates, Eben S. Cross, Paul Davidovits, Jani Hakala, Katherine L. Hayden, B. Tom Jobson, Katheryn R. Kolesar, Daniel A. Lack, Brian M. Lerner, Shao Meng Li, Daniel Mellon, Ibraheem Nuaaman, Jason S. Olfert, Tuukka Petäjä, Patricia K. Quinn, Chen SongR. Subramanian, Eric J. Williams, Rahul A. Zaveri

Research output: Contribution to journalArticleScientificpeer-review

550 Citations (Scopus)


Atmospheric black carbon (BC) warms Earth's climate, and its reduction has been targeted for near-term climate change mitigation. Models that include forcing by BC assume internal mixing with non-BC aerosol components that enhance BC absorption, often by a factor of ∼2; such model estimates have yet to be clearly validated through atmospheric observations. Here, direct in situ measurements of BC absorption enhancements (Eabs) and mixing state are reported for two California regions. The observed Eabs is small - 6% on average at 532 nm - and increases weakly with photochemical aging. The Eabs is less than predicted from observationally constrained theoretical calculations, suggesting that many climate models may overestimate warming by BC. These ambient observations stand in contrast to laboratory measurements that show substantial Eabs for BC are possible.

Original languageEnglish
Pages (from-to)1078-1081
Issue number6098
Publication statusPublished - 31 Aug 2012
MoE publication typeA1 Journal article-refereed


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