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Radiative Forcing by Well-Mixed Greenhouse Gases: Estimates from Climate Models in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4)The radiative effects from increased concentrations of well-mixed greenhouse gases (WMGHGs) represent the most significant and best understood anthropogenic forcing of the climate system. The most comprehensive tools for simulating past and future climates influenced by WMGHGs are fully coupled atmosphere-ocean general circulation models (AOGCMs). Because of the importance of WMGHGs as forcing agents it is essential that AOGCMs compute the radiative forcing by these gases as accurately as possible. We present the results of a radiative transfer model intercomparison between the forcings computed by the radiative parameterizations of AOGCMs and by benchmark line-by-line (LBL) codes. The comparison is focused on forcing by CO2, CH4, N2O, CFC-11, CFC-12, and the increased H2O expected in warmer climates. The models included in the intercomparison include several LBL codes and most of the global models submitted to the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). In general, the LBL models are in excellent agreement with each other. However, in many cases, there are substantial discrepancies among the AOGCMs and between the AOGCMs and LBL codes. In some cases this is because the AOGCMs neglect particular absorbers, in particular the near-infrared effects of CH4 and N2O, while in others it is due to the methods for modeling the radiative processes. The biases in the AOGCM forcings are generally largest at the surface level. We quantify these differences and discuss the implications for interpreting variations in forcing and response across the multimodel ensemble of AOGCM simulations assembled for the IPCC AR4.
Document ID
20080015921
Acquisition Source
Langley Research Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Collins, W. D.
(National Center for Atmospheric Research Boulder, CO, United States)
Ramaswamy, V.
(Princeton Univ. Princeton, NJ, United States)
Schwarzkopf, M. D.
(Princeton Univ. Princeton, NJ, United States)
Sun, Y.
(National Climate Center Beijing, China)
Portmann, R. W.
(National Oceanic and Atmospheric Administration Boulder, CO, United States)
Fu, Q.
(Washington Univ. Seattle, WA, United States)
Casanova, S. E. B.
(Reading Univ. United Kingdom)
Dufresne, J.-L.
(Laboratoire de Meteorologie Dynamique Paris, France)
Fillmore, D. W.
(Laboratoire des Sciences du Climar et l'Environment Gif-sur-Yvette, France)
Forster, P. M. D.
(Leeds Univ. United Kingdom)
Galin, V. Y.
(Academy of Sciences (Russia) Moscow, Russian Federation)
Gohar, L. K.
(Reading Univ. United Kingdom)
Ingram, W. J.
(Oxford Univ. Oxford, United Kingdom)
Kratz, D. P.
(NASA Langley Research Center Hampton, VA, United States)
Lefebvre, M.-P.
(Laboratoire de Meteorologie Dynamique Paris, France)
Li, J.
(Victoria Univ. British Columbia, Canada)
Marquet, P.
(Centre National de Recherches Meteorologiques Toulouse, France)
Oinas, V.
(NASA Goddard Inst. for Space Studies New York, NY, United States)
Tsushima, Y.
(Japan Agency for Marine-Earth Science and Technology Japan)
Uchiyama, T.
(Meteorological Research Inst. Tsukuba, Japan)
Zhong, W. Y.
(Imperial Coll. of London London, United Kingdom)
Date Acquired
August 24, 2013
Publication Date
July 28, 2006
Publication Information
Publication: Journal of Geophysical Research
Volume: 111
Subject Category
Earth Resources And Remote Sensing
Funding Number(s)
CONTRACT_GRANT: NER/L/S/2001/0066
CONTRACT_GRANT: 307981
Distribution Limits
Public
Copyright
Other

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