Working Group I: The Scientific Basis


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8.5 Coupled Climate Models - Means 8.5.1 Atmospheric Component

8.5.1.1 Development since the SAR

The model evaluation chapter of the IPCC Second Assessment Report (Gates et al., 1996) found that “large-scale features of the current climate are well simulated on average by current coupled models.” However, two major points of concern were noted. Firstly, the SAR found that simulation of clouds and related processes “remains a major source of uncertainty in atmospheric models”. As discussed in Chapter 7, these processes continue to account for most of the uncertainty in predicting human-induced climate change. Secondly, the SAR noted an unsatisfactory situation involving flux adjustments (Section 8.4.2): they “are relatively large in the models that use them, but their absence affects the realism of the control climate and the associated feedback processes”. Improvements in coupled climate models since the SAR have addressed both points of concern. For the atmospheric (as well as the oceanic) component, these improvements have included higher horizontal resolution (which means less numerical diffusion and better representation of topography), and advances in parametrizations. In addition, the advent of the Coupled Model Intercomparison Program (CMIP; see Meehl et al., 2000a) since the SAR has provided an additional database for evaluating AOGCMs. Some basic details of models evaluated in this chapter and used elsewhere in this report are presented in Table 8.1.

Table 8.1: Model control runs: a consolidated list of coupled AOGCMs that are assessed in Chapter 8 and used in other Chapters. The naming convention for the models is as agreed by all modelling groups involved. Under the heading CMIP: 1,2 indicate that the model control run is included in the Coupled Model Intercomparison Phase 1 and 2 (CMIP1 and 2) databases, respectively.
  MODEL NAME CENTRE REFERENCE CMIP Ch 9 Ch 11 Ch 12 ATMOSPHERIC RESOLUTION OCEAN RESOLUTION LAND SURFACE SEA ICE FLUX ADJUST
1 ARPEGE/OPA1 CERFACS Guilyardi and Madec, 1997 1 ---     T21 (5.6 x 5.6) L30 2.0 x 2.0 L31* C (d) -
2 ARPEGE/OPA2 CERFACS Barthelet et al., 1998a,b 2 C--     T31 (3.9 x 3.9) L19 2.0 x 2.0 L31* C T -
3 BMRCa BMRC Power et al., 1993 1 C--     R21 (3.2 x 5.6) L9 3.2 x 5.6 L12 M,B T -
4 BMRCb BMRC Power et al., 1998 2 ---     R21 (3.2 x 5.6) L17 3.2 x 5.6 L12* M,B T H,W
5 CCSR/NIES CCSR/NIES Emori et al., 1999 1,2 C-D     T21 (5.6 x 5.6) L20 2.8 x 2.8 L17 M,BB T H,W
6 CGCM1 CCCma Boer et al., 2000;
Flato et al., 2000		 1,2 C-D * * T32 (3.8 x 3.8) L10 1.8 x 1.8 L29 M,BB T H,W
7 CGCM2 CCCma Flato and Boer, 2001 - -S- * * T32 (3.8 x 3.8) L10 1.8 x 1.8 L29 M,BB T,R H,W
8 COLA1 COLA

Schneider et al., 1997;
Schneider and Zhu, 1998

 1 ---     R15 (4.5 x 7.5) L9 1.5 x 1.5 L20* C T -
9 COLA2 COLA Dewitt and Schneider, 1999 1 ---     T30 (4 x 4) L18 3.0 x 3.0 L20* C T -
10 CSIRO Mk2 CSIRO Gordon and O’Farrell, 1997 1,2 C-D     R21 (3.2 x 5.6) L9 3.2 x 5.6 L21 C T,R H,W,M
11 CSM 1.0 NCAR Boville and Gent, 1998 1,2 C--     T42 (2.8 x 2.8) L18 2.0 x 2.4 L45* C T,R -
12 CSM 1.3 NCAR Boville et al., 2001 - -SD     T42 (2.8 x 2.8) L18 2.0 x 2.4 L45* C T,R -
13 ECHAM1/LSG DKRZ Cubasch et al., 1992;
von Storch, 1994;
von Storch et al., 1997 		1 ---   * T21 (5.6 x 5.6) L19 4.0 x 4.0 L11 C T H,W,M
14 ECHAM3/LSG DKRZ Cubasch et al 1997;
Voss et al., 1998 		1,2 C-D   * T21 (5.6 x 5.6) L19 4.0 x 4.0 L11 C T H,W,M
15 ECHAM4/OPYC3 DKRZ Roeckner et al., 1996 1 C-D * * T42 (2.8 x 2.8) L19 2.8 x 2.8 L11* C T,R H,W(*)
16 GFDL_R15_a GFDL Manabe et al., 1991;
Manabe and Stouffer1996 		1,2 C-D   * R15 (4.5 x 7.5) L9 4.5 x 3.7 L12 B T,F H,W
17 GFDL_R15_b GFDL Dixon and Lanzante, 1999 - C-- *   R15 (4.5 x 7.5) L9 4.5 x 3.7 L12 B T,F H,W
18 GFDL_R30_c GFDL Knutson et al., 1999 - CS- * * R30 (2.25 x 3.75) L14 1.875 x 2.25 L18 B T,F H,W
19 GISS1 GISS Miller and Jiang, 1996 1 ---     4.0 x 5.0 L9 4.0 x 5.0 L16 C T -
20 GISS2 GISS Russell et al., 1995 1,2 C--     4.0 x 5.0 L9 4.0 x 5.0 L13 C T -
21 GOALS IAP/LASG Wu et al., 1997;
Zhang et al., 2000 		1,2 C--     R15 (4.5 x 7.5) L9 4.0 x 5.0 L20 C T H,W,M
22 HadCM2 UKMO Johns 1996;
Johns et al., 1997 		1,2 C-D   * 2.5 x 3.75 L19 2.5 x 3.75 L20 C T,F H,W
23 HadCM3 UKMO Gordon et al., 2000 2 CSD   * 2.5 x 3.75 L19 1.25 x 1.25 L20 C T,F -
24 IPSL-CM1 IPSL/LMD Braconnot et al., 2000 1 ---     5.6 x 3.8 L15 2.0 x 2.0 L31* C (d) -
25 IPSL-CM2 IPSL/LMD Laurent et al., 1998; 2 C--     5.6 x 3.8 L15 2.0 x 2.0 L31* C T -
26 MRI1a MRI Tokioka et al., 1996 1,(2)a C--     4.0 x 5.0 L15 2.0 x 2.5 L21(23)a* M,B T,F H,W
27 MRI2 MRI Yukimoto et al., 2000 - CS- *   T42(2.8 x 2.8) L30 2.0 x 2.5 L23* C T,F H,W,M
28 NCAR1 NCAR Meehl and Washington, 1995;
Washington and Meehl, 1996 		1,2 ---     R15 (4.5 x 7.5) L9 1.0 x 1.0 L20 B T,R -
29 NRL NRL Hogan and Li, 1997;
Li and Hogan, 1999 		1,2 ---     T47 (2.5 x 2.5) L18 1.0 x 2.0 L25* BB T(p) H,W(*)
30 DOE PCM NCAR Washington et al., 2000 2 CSD     T42 (2.8 x 2.8) L18 0.67 x 0.67 L32 C T,R -
31 CCSR/NIES2 CCSR/NIES Nozawa et al., 2000 - CS-     T21 (5.6 x 5.6) L20 2.8 x 3.8 L17 M,BB T H,W
                         
I1 BERN2D PIUB Stocker et al., 1992;
Schmittner & Stocker, 1999 		- --- *   10* x ZA L1 10* x ZA L15 - T -
I2 UVIC UVIC Fanning and Weaver, 1996;
Weaver et al., 1998 		- --- *   1.8 x 3.6 L1 1.8 x 3.6 L19 - T,R -
I3 CLIMBER PIK Petoukhov et al., 2000 - --- *   10 x 51 L2 10 x ZA L11 C T,F -

a Model MRI1 exists in two versions. At the time of writing, more complete assessment data was available for the earlier version, whose control run is in the CMIP1 database. This model is used in Chapter 8. The model used in Chapter 9 has two extra ocean levels and a modified ocean mixing scheme. Its control run is in the CMIP2 database. The equilibrium climate sensitivities and Transient Climate Responses (Chapter 9, Table 9.1) of the two models are the same.

CMIP: 1,2 indicate that the model control run is included in the CMIP1 and CMIP2 databases, respectively.
Ch 9: C indicates that a run or runs with the CMIP2 1% p.a. CO2 increase scenario is used in Chapter 9 (irrespective of whether the data is included in the CMIP database). S indicates that SRES scenario runs (including at least A2 and B2) are used in Chapter 9. D indicates that model output is lodged at the IPCC Data Distribution Centre.
Ch 11, Ch 12: An asterisk indicates that the model has been used to make sea level projections (Chapter 11) or in detection/attribution studies (Chapter 12).
Atmospheric resolution: Horizontal and vertical resolution. The former is expressed either as degrees latitude x longitude or as a spectral trunca-tion with a rough translation to degrees latitude xlongitude. An asterisk indicates enhanced meridional resolution in midlatitudes. ZA indicates a zonally averaged model (360° zonal resolution). Vertical resolution is expressed as “Lmm”, where mm is the number of vertical levels.
Ocean resolution: Horizontal and vertical resolution. The former is expressed as degrees latitude xlongitude, while the latter is expressed as “Lmm”, where mm is the number of vertical levels. An asterisk indicates enhanced horizontal resolution near the Equator. ZA indicates a zonally averaged model for each ocean basin. The following classification of ocean horizontal resolution is used throughout Chapters 7 to 9: Coarse: >2°, Medium: 2/3° to 2°, Eddy-permitting: 1/6° to 2/3°, Eddy-resolving: <1/6°.
Land surface scheme: B = standard bucket hydrology scheme; BB = modified bucket scheme with spatially varying soil moisture capacity and/or a surface resistance; M = multi-layer temperature scheme; C = a complex land surface scheme usually including multi-soil layers for temperature and soil moisture, and an explicit representation of canopy processes.
Sea ice model: T = thermodynamic ice model only; F = ‘free drift’ dynamics; R = ice rheology included; (d) = ice extent/thickness determined diagnostically from ocean surface temperature; (p) = ice extent prescribed.
Flux adjustment: H = heat flux; W = fresh water flux; M = momentum flux. An asterisk indicates annual mean flux adjustment only.

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