2. Model Hierarchy and Simplified Climate Models

There is no best climate model! Different models have different advantages which may be due to their complexity or the form of their implemented parameterisations. Table 2.1 gives an (incomplete) overview of the hierarchy of models used for climate simulations. They are ordered according to their spatial dimensions. Only model types are listed but each type may be formulated in different ways. For instance different resolutions are used, different grid structures, parameters and parameterisations are chosen in a different way, etc. There are, for example, more than a dozen different ocean circulation models, all of which basically solve the same conservation equations. For model development and progress the various Modelling Intercomparison Projects provide important insight: AMIP (Atmospheric Modelling Intercomparison Project), OMIP (Ocean …), OCMIP (Ocean Carbon-cycle …), CMIP (Coupled …), PMIP (Paleo …), C⁴MIP (Coupled Climate-Carbon Cycle Modelling Intercomparison Project), etc.