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IPCC Fourth Assessment Report: Climate Change 2007 |
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Climate Change 2007: Working Group I: The Physical Science Basis 8.2 Advances in Modelling Many modelling advances have occurred since the TAR. Space does not permit a comprehensive discussion of all major changes made over the past several years to the 23 AOGCMs used widely in this report (see Table 8.1). Model improvements can, however, be grouped into three categories. First, the dynamical cores (advection, etc.) have been improved, and the horizontal and vertical resolutions of many models have been increased. Second, more processes have been incorporated into the models, in particular in the modelling of aerosols, and of land surface and sea ice processes. Third, the parametrizations of physical processes have been improved. For example, as discussed further in Section 8.2.7, most of the models no longer use flux adjustments (Manabe and Stouffer, 1988; Sausen et al., 1988) to reduce climate drift. These various improvements, developed across the broader modelling community, are well represented in the climate models used in this report. Table 8.1. Selected model features. Salient features of the AOGCMs participating in the MMD at PCMDI are listed by IPCC identification (ID) along with the calendar year (‘vintage’) of the first publication of results from each model. Also listed are the respective sponsoring institutions, the pressure at the top of the atmospheric model, the horizontal and vertical resolution of the model atmosphere and ocean models, as well as the oceanic vertical coordinate type (Z: see Griffies (2004) for definitions) and upper boundary condition (BC: free surface or rigid lid). Also listed are the characteristics of sea ice dynamics/structure (e.g., rheology vs ‘free drift’ assumption and inclusion of ice leads), and whether adjustments of surface momentum, heat or freshwater fluxes are applied in coupling the atmosphere, ocean and sea ice components. Land features such as the representation of soil moisture (single-layer ‘bucket’ vs multi-layered scheme) and the presence of a vegetation canopy or a river routing scheme also are noted. Relevant references describing details of these aspects of the models are cited. Model ID, Vintage | Sponsor(s), Country | Atmosphere Top Resolutiona References | Ocean Resolutionb Z Coord., Top BC References | Sea Ice Dynamics, Leads References | Coupling Flux Adjustments References | Land Soil, Plants, Routing References |
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| 1: BCC-CM1, 2005 | Beijing Climate Center, China | top = 25 hPa T63 (1.9° x 1.9°) L16 Dong et al., 2000; CSMD, 2005; Xu et al., 2005 | 1.9° x 1.9° L30 depth, free surface Jin et al., 1999 | no rheology or leads Xu et al., 2005 | heat, momentum Yu and Zhang, 2000; CSMD, 2005 | layers, canopy, routing CSMD, 2005 | | 2: BCCR-BCM2.0, 2005 | Bjerknes Centre for Climate Research, Norway | top = 10 hPa T63 (1.9° x 1.9°) L31 Déqué et al., 1994 | 0.5°–1.5° x 1.5° L35 density, free surface Bleck et al., 1992 | rheology, leads Hibler, 1979; Harder, 1996 | no adjustments Furevik et al., 2003 | Layers, canopy, routing Mahfouf et al., 1995; Douville et al., 1995; Oki and Sud, 1998 | | 3: CCSM3, 2005 | National Center for Atmospheric Research, USA | top = 2.2 hPa T85 (1.4° x 1.4°) L26 Collins et al., 2004 | 0.3°–1° x 1° L40 depth, free surface Smith and Gent, 2002 | rheology, leads Briegleb et al., 2004 | no adjustments Collins et al., 2006 | layers, canopy, routing Oleson et al., 2004; Branstetter, 2001 | | 4: CGCM3.1(T47), 2005 | Canadian Centre for Climate Modelling and Analysis, Canada | top = 1 hPa T47 (~2.8° x 2.8°) L31 McFarlane et al., 1992; Flato, 2005 | 1.9° x 1.9° L29 depth, rigid lid Pacanowski et al., 1993 | rheology, leads Hibler, 1979; Flato and Hibler, 1992 | heat, freshwater Flato, 2005 | layers, canopy, routing Verseghy et al., 1993 | | 5: CGCM3.1(T63), 2005 | top = 1 hPa T63 (~1.9° x 1.9°) L31 McFarlane et al., 1992; Flato 2005 | 0.9° x 1.4° L29 depth, rigid lid Flato and Boer, 2001; Kim et al., 2002 | rheology, leads Hibler, 1979; Flato and Hibler, 1992 | heat, freshwater Flato, 2005 | layers, canopy, routing Verseghy et al., 1993 | | 6: CNRM-CM3, 2004 | Météo-France/Centre National de Recherches Météorologiques, France | top = 0.05 hPa T63 (~1.9° x 1.9°) L45 Déqué et al., 1994 | 0.5°–2° x 2° L31 depth, rigid lid Madec et al., 1998 | rheology, leads Hunke-Dukowicz, 1997; Salas-Mélia, 2002 | no adjustments Terray et al., 1998 | layers, canopy,routing Mahfouf et al., 1995; Douville et al., 1995; Oki and Sud, 1998 | | 7: CSIRO-MK3.0, 2001 | Commonwealth Scientific and Industrial Research Organisation (CSIRO) Atmospheric Research, Australia | top = 4.5 hPa T63 (~1.9° x 1.9°) L18 Gordon et al., 2002 | 0.8° x 1.9° L31 depth, rigid lid Gordon et al., 2002 | rheology, leads O’Farrell, 1998 | no adjustments Gordon et al., 2002 | layers, canopy Gordon et al., 2002 | | 8: ECHAM5/MPI-OM, 2005 | Max Planck Institute for Meteorology, Germany | top = 10 hPa T63 (~1.9° x 1.9°) L31 Roeckner et al., 2003 | 1.5° x 1.5° L40 depth, free surface Marsland et al., 2003 | rheology, leads Hibler, 1979; Semtner, 1976 | no adjustments Jungclaus et al., 2005 | bucket, canopy, routing Hagemann, 2002; Hagemann and Dümenil-Gates, 2001 | | 9: ECHO-G, 1999 | Meteorological Institute of the University of Bonn, Meteorological Research Institute of the Korea Meteorological Administration (KMA), and Model and Data Group, Germany/Korea | top = 10 hPa T30 (~3.9° x 3.9°) L19 Roeckner et al., 1996 | 0.5°–2.8° x 2.8° L20 depth, free surface Wolff et al., 1997 | rheology, leads Wolff et al., 1997 | heat, freshwater Min et al., 2005 | bucket, canopy, routing Roeckner et al., 1996; Dümenil and Todini, 1992 | Model ID, Vintage | Sponsor(s), Country | Atmosphere Top Resolutiona References | Ocean Resolutionb Z Coord., Top BC References | Sea Ice Dynamics, Leads References | Coupling Flux Adjustments References | Land Soil, Plants, Routing References |
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| 10: FGOALS-g1.0, 2004 | National Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG)/Institute of Atmospheric Physics, China | top = 2.2 hPa T42 (~2.8° x 2.8°) L26 Wang et al., 2004 | 1.0° x 1.0° L16 eta, free surface Jin et al., 1999; Liu et al., 2004 | rheology, leads Briegleb et al., 2004 | no adjustments Yu et al., 2002, 2004 | layers, canopy, routing Bonan et al., 2002 | | 11: GFDL-CM2.0, 2005 | U.S. Department of Commerce/National Oceanic and Atmospheric Administration (NOAA)/Geophysical Fluid Dynamics Laboratory (GFDL), USA | top = 3 hPa 2.0° x 2.5° L24 GFDL GAMDT, 2004 | 0.3°–1.0° x 1.0° depth, free surface Gnanadesikan et al., 2004 | rheology, leads Winton, 2000; Delworth et al., 2006 | no adjustments Delworth et al., 2006 | bucket, canopy, routing Milly and Shmakin, 2002; GFDL GAMDT, 2004 | | 12: GFDL-CM2.1, 2005 | top = 3 hPa 2.0° x 2.5° L24 GFDL GAMDT, 2004 with semi-Lagrangian transports | 0.3°–1.0° x 1.0° depth, free surface Gnanadesikan et al., 2004 | rheology, leads Winton, 2000; Delworth et al., 2006 | no adjustments Delworth et al., 2006 | bucket, canopy, routing Milly and Shmakin, 2002; GFDL GAMDT, 2004 | | 13: GISS-AOM, 2004 | National Aeronautics and Space Administration (NASA)/Goddard Institute for Space Studies (GISS), USA | top = 10 hPa 3° x 4° L12 Russell et al., 1995; Russell, 2005 | 3° x 4° L16 mass/area, free surface Russell et al., 1995; Russell, 2005 | rheology, leads Flato and Hibler, 1992; Russell, 2005 | no adjustments Russell, 2005 | layers, canopy, routing Abramopoulos et al., 1988; Miller et al., 1994 | | 14: GISS-EH, 2004 | top = 0.1 hPa 4° x 5° L20 Schmidt et al., 2006 | 2° x 2° L16 density, free surface Bleck, 2002 | rheology, leads Liu et al., 2003; Schmidt et al., 2004 | no adjustments Schmidt et al., 2006 | layers, canopy, routing Friend and Kiang, 2005 | | 15: GISS-ER, 2004 | NASA/GISS, USA | top = 0.1 hPa 4° x 5° L20 Schmidt et al., 2006 | 4° x 5° L13 mass/area, free surface Russell et al., 1995 | rheology, leads Liu et al., 2003; Schmidt et al., 2004 | no adjustments Schmidt et al., 2006 | layers, canopy, routing Friend and Kiang, 2005 | | 16: INM-CM3.0, 2004 | Institute for Numerical Mathematics, Russia | top = 10 hPa 4° x 5° L21 Alekseev et al., 1998; Galin et al., 2003 | 2° x 2.5° L33 sigma, rigid lid Diansky et al., 2002 | no rheology or leads Diansky et al., 2002 | regional freshwater Diansky and Volodin, 2002; Volodin and Diansky, 2004 | layers, canopy, no routing Alekseev et al., 1998; Volodin and Lykosoff, 1998 | | 17: IPSL-CM4, 2005 | Institut Pierre Simon Laplace, France | top = 4 hPa 2.5° x 3.75° L19 Hourdin et al., 2006 | 2° x 2° L31 depth, free surface Madec et al., 1998 | rheology, leads Fichefet and Morales Maqueda, 1997; Goosse and Fichefet, 1999 | no adjustments Marti et al., 2005 | layers, canopy, routing Krinner et al., 2005 | | 18: MIROC3.2(hires), 2004 | Center for Climate System Research (University of Tokyo), National Institute for Environmental Studies, and Frontier Research Center for Global Change (JAMSTEC), Japan | top = 40 km T106 (~1.1° x 1.1°) L56 K-1 Developers, 2004 | 0.2° x 0.3° L47 sigma/depth, free surface K-1 Developers, 2004 | rheology, leads K-1 Developers, 2004 | no adjustments K-1 Developers, 2004 | layers, canopy, routing K-1 Developers, 2004; Oki and Sud, 1998 | | 19: MIROC3.2(medres), 2004 | top = 30 km T42 (~2.8° x 2.8°) L20 K-1 Developers, 2004 | 0.5°–1.4° x 1.4° L43 sigma/depth, free surface K-1 Developers, 2004 | rheology, leads K-1 Developers, 2004 | no adjustments K-1 Developers, 2004 | layers, canopy, routing K-1 Developers, 2004; Oki and Sud, 1998 | Model ID, Vintage | Sponsor(s), Country | Atmosphere Top Resolutiona References | Ocean Resolutionb Z Coord., Top BC References | Sea Ice Dynamics, Leads References | Coupling Flux Adjustments References | Land Soil, Plants, Routing References |
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| 20: MRI-CGCM2.3.2, 2003 | Meteorological Research Institute, Japan | top = 0.4 hPa T42 (~2.8° x 2.8°) L30 Shibata et al., 1999 | 0.5°–2.0° x 2.5° L23 depth, rigid lid Yukimoto et al., 2001 | free drift, leads Mellor and Kantha, 1989 | heat, freshwater, momentum (12°S–12°N) Yukimoto et al., 2001; Yukimoto and Noda, 2003 | layers, canopy, routing Sellers et al., 1986; Sato et al., 1989 | | 21: PCM, 1998 | National Center for Atmospheric Research, USA | top = 2.2 hPa T42 (~2.8° x 2.8°) L26 Kiehl et al., 1998 | 0.5°–0.7° x 1.1° L40 depth, free surface Maltrud et al., 1998 | rheology, leads Hunke and Dukowicz 1997, 2003; Zhang et al., 1999 | no adjustments Washington et al., 2000 | layers, canopy, no routing Bonan, 1998 | | 22: UKMO-HadCM3, 1997 | Hadley Centre for Climate Prediction and Research/Met Office, UK | top = 5 hPa 2.5° x 3.75° L19 Pope et al., 2000 | 1.25° x 1.25° L20 depth, rigid lid Gordon et al., 2000 | free drift, leads Cattle and Crossley, 1995 | no adjustments Gordon et al., 2000 | layers, canopy, routing Cox et al., 1999 | | 23: UKMO-HadGEM1, 2004 | top = 39.2 km ~1.3° x 1.9° L38 Martin et al., 2004 | 0.3°–1.0° x 1.0° L40 depth, free surface Roberts, 2004 | rheology, leads Hunke and Dukowicz, 1997; Semtner, 1976; Lipscomb, 2001 | no adjustments Johns et al., 2006 | layers, canopy, routing Essery et al., 2001; Oki and Sud, 1998 |
Despite the many improvements, numerous issues remain. Many of the important processes that determine a model’s response to changes in radiative forcing are not resolved by the model’s grid. Instead, sub-grid scale parametrizations are used to parametrize the unresolved processes, such as cloud formation and the mixing due to oceanic eddies. It continues to be the case that multi-model ensemble simulations generally provide more robust information than runs of any single model. Table 8.1 summarises the formulations of each of the AOGCMs used in this report. There is currently no consensus on the optimal way to divide computer resources among finer numerical grids, which allow for better simulations; greater numbers of ensemble members, which allow for better statistical estimates of uncertainty; and inclusion of a more complete set of processes (e.g., carbon feedbacks, atmospheric chemistry interactions). |
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