Atmos. Chem. Phys. Discuss., 12, 22355-22413, 2012
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Radiative forcing of the direct aerosol effect from AeroCom Phase II simulations
G. Myhre1, B. H. Samset1, M. Schulz2, Y. Balkanski3, S. Bauer4, T. K. Berntsen1, H. Bian5, N. Bellouin6, M. Chin7, T. Diehl7,8, R. C. Easter9, J. Feichter10, S. J. Ghan9, D. Hauglustaine3, T. Iversen2,11, S. Kinne10, A. Kirkevåg2, J.-F. Lamarque12, G. Lin13, X. Liu9, G. Luo14, X. Ma14, J. E. Penner13, P. J. Rasch9, Ø. Seland2, R. B. Skeie1, P. Stier15, T. Takemura16, K. Tsigaridis4, Z. Wang17, L. Xu13,18, H. Yu5, F. Yu14, J.-H. Yoon9, K. Zhang9, H. Zhang19, and C. Zhou13
1Center for International Climate and Environmental Research – Oslo (CICERO), Oslo, Norway
2Norwegian Meteorological Institute, Oslo, Norway
3Laboratoire des Sciences du Climat et de l'Environnement, CEA-CNRS-UVSQ, Gif-sur-Yvette, France
4NASA Goddard Institute for Space Studies and Columbia Earth Institute, New York, NY, USA
5Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD, USA
6Met Office Hadley Centre, Exeter, UK
7NASA Goddard Space Flight Center, Greenbelt, MD, USA
8Universities Space Research Association, Columbia, MD, USA
9Pacific Northwest National Laboratory, Richland, WA, USA
10Max Planck Institute for Meteorology, Hamburg, Germany
11Department of Geosciences, University of Oslo, Norway
12NCAR Earth System Laboratory, National Center for Atmospheric Research, Boulder, CO, USA
13Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, Michigan, USA
14Atmospheric Sciences Research Center, State University of New York at Albany, New York, USA
15University of Oxford, Oxford, UK
16Research Institute for Applied Mechanics, Kyushu University, Japan
17Chinese Academy of Meteorological Sciences, Beijing 100081, China
18Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, USA
19Laboratory for Climate Studies, National Climate Center, China Meteorological Administration, Beijing 100081, China

Abstract. We report on the AeroCom Phase II direct aerosol effect (DAE) experiment where 15 detailed global aerosol models have been used to simulate the changes in the aerosol distribution over the industrial era. All 15 models have estimated the radiative forcing (RF) of the anthropogenic DAE, and have taken into account anthropogenic sulphate, black carbon (BC) and organic aerosols (OA) from fossil fuel, biofuel, and biomass burning emissions. In addition several models have simulated the DAE of anthropogenic nitrate and anthropogenic influenced secondary organic aerosols (SOA). The model simulated all-sky RF of the DAE from total anthropogenic aerosols has a range from −0.58 to −0.02 W m−2, with a mean of −0.30 W m−2 for the 15 models. Several models did not include nitrate or SOA and modifying the estimate by accounting for this with information from the other AeroCom models reduces the range and slightly strengthens the mean. Modifying the model estimates for missing aerosol components and for the time period 1750 to 2010 results in a mean RF for the DAE of −0.39 W m−2. Compared to AeroCom Phase I (Schulz et al., 2006) we find very similar spreads in both total DAE and aerosol component RF. However, the RF of the total DAE is stronger negative and RF from BC from fossil fuel and biofuel emissions are stronger positive in the present study than in the previous AeroCom study. We find a tendency for models having a strong (positive) BC RF to also have strong (negative) sulphate or OA RF. This relationship leads to smaller uncertainty in the total RF of the DAE compared to the RF of the sum of the individual aerosol components. The spread in results for the individual aerosol components is substantial, and can be divided into diversities in burden, mass extinction coefficient (MEC), and normalized RF with respect to AOD. We find that these three factors give similar contributions to the spread in results.

Citation: Myhre, G., Samset, B. H., Schulz, M., Balkanski, Y., Bauer, S., Berntsen, T. K., Bian, H., Bellouin, N., Chin, M., Diehl, T., Easter, R. C., Feichter, J., Ghan, S. J., Hauglustaine, D., Iversen, T., Kinne, S., Kirkevåg, A., Lamarque, J.-F., Lin, G., Liu, X., Luo, G., Ma, X., Penner, J. E., Rasch, P. J., Seland, Ø., Skeie, R. B., Stier, P., Takemura, T., Tsigaridis, K., Wang, Z., Xu, L., Yu, H., Yu, F., Yoon, J.-H., Zhang, K., Zhang, H., and Zhou, C.: Radiative forcing of the direct aerosol effect from AeroCom Phase II simulations, Atmos. Chem. Phys. Discuss., 12, 22355-22413, doi:10.5194/acpd-12-22355-2012, 2012.
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