General Circulation Models (GCMs) are a class of computer-driven models for weather forecasting, understanding climate and projecting climate change, where they are commonly called Global Climate Models.
A global climate model or general circulation model aims to describe climate behavior by integrating a variety of fluid-dynamical, chemical, or even biological equations that are either derived directly from physical laws (e.g.
Newton's law) or constructed by more empirical means.
There are both atmospheric GCMs (AGCMs) and ocean GCMs (OGCMs).
An AGCM and an OGCM can be coupled together to form an atmosphere-ocean coupled general circulation model (AOGCM).
With the addition of other components (such as a sea ice model or a land model), the AOGCM becomes the basis for a full climate model.
Within this structure, different variations can exist, and their varying response to climate change may be studied.
A recent trend in GCMs is to extend them to become Earth system models, that include such things as submodels for atmospheric chemistry or a carbon cycle model to better predict changes in carbon dioxide concentrations resulting from changes in emissions.
In addition this approach allows feedback between these systems to be taken into account.
For example, Chemistry-Climate models allow the possible effects of climate change on the recovery of the ozone hole to be studied.