EARTH SCIENCE SERVICES > MODELS > COUPLED CLIMATE MODELS
Coupled atmosphere-ocean general circulation models (AOGCMs) are the most
complex models in use, consisting of an Atmosphere general circulation model
(AGCM) coupled to an Ocean general circulation models (OGCM). With the addition
of other components (such as a sea ice model or a model for evapotranspiration
over land), the AOGCM becomes the basis for a full climate model.
Some recent models include the biosphere, carbon cycle and atmospheric
chemistry as well. AOGCMs can be used for the prediction and rate of change of
future climate. They are also used to study the variability and physical
processes of the coupled climate system. Global climate models typically have a
resolution of a few hundred kilometres. Climate projections from the Hadley
Centre make use of the HadCM2 AOGCM, developed in 1994, and its successor
HadCM3 AOGCM, developed in 1998. Greenhouse-gas experiments with AOGCMs have
usually been driven by specifying atmospheric concentrations of the gases, but
if a carbon cycle model is included, the AOGCM can predict changes in carbon
dioxide concentration, given the emissions of carbon dioxide into the
atmosphere. Similarly, an AOGCM coupled to an atmospheric chemistry model is
able to predict the changes in concentration of other atmospheric constituents
in response to climate change and to the changing emissions of various gases.
Further information is available on: some aspects of ocean simulation in HadCM3
(thermohaline circulation, ventilation, vertical mixing), decadal variability
in the ocean of HadCM3.
Recently a global coupled climate model with an eddy-permitting ocean
resolution has been developed at the Hadley Centre, in order to better
represent important oceanic processes.