CGCM1 GCM Model Information

Background Information

The first version of the Canadian Global Coupled Model, CGCM1, and its control climate are described by Flato et al. (1999). The atmospheric component of the model is essentially GCMII described by McFarlane et al. (1992). It is a spectral model with triangular truncation at wave number 32 (yielding a surface grid resolution of roughly 3.7ºx3.7º) and 10 vertical levels. The ocean component is based on the GFDL MOM1.1 code and has a resolution of approximately 1.8ºx1.8º and 29 vertical levels. The model uses heat and water flux adjustments obtained from uncoupled ocean and atmosphere model runs (of 10 years and 4000 years duration respectively), followed by an `adaption' procedure in which the flux adjustment fields are modified by a 14 year integration of the coupled model. A multi-century control simulation with the coupled model has been performed using the present-day CO2 concentration to evaluate the stability of the coupled model's climate, and to compare the modelled climate and its variability to that observed.

An ensemble of four transient climate change simulations has been performed and is described in Boer et al. (1999a; b). Three of these simulations use an effective greenhouse gas forcing change corresponding to that observed from 1850 to the present, and a forcing change corresponding to an increase of CO2 at a rate of 1% per year (compounded) thereafter until year 2100. The direct forcing effect of sulphate aerosols is also included by increasing the surface albedo (as in Reader and Boer, 1999) based on loadings from the sulphur cycle model of Langner and Rodhe (1991). The fourth simulation considers the effect of greenhouse gas forcing only. The change in climate predicted by a model clearly depends directly on this specification of greenhouse gas (and aerosol) forcing, and of course these are not well known. The prescription described above is similar to the IPCC "business as usual" scenario, and using a standard scenario allows the results of this model to be compared to those of other modelling groups around the world. Some initial results from these simulations are presented below.

Global-Mean Temperature, Precipitation and CO2 Changes (w.r.t. 1961 - 1990) for the CGCM1 integrations

Notes

The climate sensitivity of CGCM1 is about 3.5ºC.

References and Other Reading

Flato, G.M.; Boer, G.J.; Lee, W.G.; McFarlane, N.A.; Ramsden, D.; Reader, M.C.; Weaver, A.J., 1999a: The Canadian Centre for Climate Modelling and Analysis Global Coupled Model and its Climate, in press Climate Dynamics.

Boer, G.J.; Flato, G.M.; Reader, M.C.; Ramsden, D., "Transient climate change simulation with historical and projected greenhouse gas and aerosol forcing", 1999b, in press Climate Dynamics.

Flato, G.M., Boer, G.J., Lee, W.G., McFarlane, N.A., Ramsden, D., Reader, M.C., Weaver, A.J., The Canadian Centre for Climate Modelling and Analysis Global Coupled Model and its Climate,1999, in press Climate Dynamics.

Reader, M.C. and Boer, G.J. 1998 The modification of greenhouse gas warming by the direct effect of sulphate aerosols, Climate Dynamics, 14, 593-607.

Further Details

The First Generation Coupled Global Climate Model