Existing numerical models used for climate prediction have horizontal resolutions (that is, grid spacings) of several hundred kilometers. Regional numerical models of areas such as the Southern Ocean use a model grid with a horizontal resolution of 100 km or more. Both of these resolutions are far too coarse to correctly represent either the major ocean currents (the Gulf Stream is typically 50 km wide) or the oceanic eddy field (eddies of 100–200 km diameter). The models do not properly reproduce detailed field observations, and they are probably adequate for climate prediction only if suitable parameterizations of the eddy field are included. Although the computer costs are high, models that can resolve these features should be substantially more realistic, predict climate change better, and provide better insight into the physics controlling the ocean.