ACP Atmospheric Chemistry and Physics ACP Atmos. Chem. Phys. 1680-7324 Copernicus Publications Göttingen, Germany 10.5194/acp-13-2423-2013 Black carbon vertical profiles strongly affect its radiative forcing uncertainty Samset B. H. https://orcid.org/0000-0001-8013-1833 1 Myhre G. https://orcid.org/0000-0002-4309-476X 1 Schulz M. https://orcid.org/0000-0003-4493-4158 2 Balkanski Y. https://orcid.org/0000-0001-8241-2858 3 Bauer S. 4 Berntsen T. K. 1 Bian H. 5 Bellouin N. https://orcid.org/0000-0003-2109-9559 6 Diehl T. 7 8 Easter R. C. https://orcid.org/0000-0002-8602-1464 9 Ghan S. J. 9 Iversen T. https://orcid.org/0000-0001-6875-2979 2 11 16 Kinne S. 10 Kirkevåg A. https://orcid.org/0000-0002-3691-554X 2 Lamarque J.-F. https://orcid.org/0000-0002-4225-5074 12 Lin G. 13 Liu X. 9 Penner J. E. https://orcid.org/0000-0001-5577-452X 13 Seland Ø. 2 Skeie R. B. https://orcid.org/0000-0003-1246-4446 1 Stier P. https://orcid.org/0000-0002-1191-0128 14 Takemura T. https://orcid.org/0000-0002-2859-6067 15 Tsigaridis K. https://orcid.org/0000-0001-5328-819X 4 Zhang K. https://orcid.org/0000-0003-0457-6368 9 10 Center for International Climate and Environmental Research – Oslo (CICERO), Oslo, Norway Norwegian Meteorological Institute, Oslo, Norway Laboratoire des Sciences du Climat et de l'Environnement, CEA-CNRS-UVSQ, Gif-sur-Yvette, France NASA Goddard Institute for Space Studies and Columbia Earth Institute, New York, NY, USA Joint Center for Earth Systems Technology, University of Maryland Baltimore County, MD, USA Met Office Hadley Centre, Exeter, UK NASA Goddard Space Flight Center, Greenbelt, MD, USA Universities Space Research Association, Columbia, MD, USA Pacific Northwest National Laboratory, Richland, WA, USA Max Planck Institute for Meteorology, Hamburg, Germany Department of Geosciences, University of Oslo, Oslo, USA NCAR Earth System Laboratory, National Center for Atmospheric Research, Boulder, CO, USA Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, Michigan, USA Department of Physics, University of Oxford, Oxford, UK Research Institute for Applied Mechanics, Kyushu University, Fukuoka, Japan ECMWF, Shinfield Park, RG2 9AX, Reading, UK 01 03 2013 13 5 2423 2434 Copyright: © 2013 B. H. Samset et al. 2013 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://acp.copernicus.org/articles/13/2423/2013/acp-13-2423-2013.html The full text article is available as a PDF file from https://acp.copernicus.org/articles/13/2423/2013/acp-13-2423-2013.pdf

The impact of black carbon (BC) aerosols on the global radiation balance is not well constrained. Here twelve global aerosol models are used to show that at least 20% of the present uncertainty in modeled BC direct radiative forcing (RF) is due to diversity in the simulated vertical profile of BC mass. Results are from phases 1 and 2 of the global aerosol model intercomparison project (AeroCom). Additionally, a significant fraction of the variability is shown to come from high altitudes, as, globally, more than 40% of the total BC RF is exerted above 5 km. BC emission regions and areas with transported BC are found to have differing characteristics. These insights into the importance of the vertical profile of BC lead us to suggest that observational studies are needed to better characterize the global distribution of BC, including in the upper troposphere.

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