Ocean general circulation models (OGCMs) are a particular kind of general circulation model to descript physical and thermodynamical processes in oceans, they include all of the major influences on the oceanic general circulation. The oceanic general circulation is defined as the horizontal space scale and time scale larger than mesoscale (of order 100 km and 6 months). They depict oceans using a three-dimensional grid that include active thermodynamics and hence are most directly applicable to climate studies, hence they are the most advanced tools currently available for simulating the response of the global ocean system to increasing greenhouse gas concentrations. A hierarchy of OGCMs have been developed that include varying degrees of spatial coverage, resolution, geographical realism, process, etc.