Global Climate Models or General Circulation Models (GCMs) are  computer  codes used to solve a set of mathematical equations describing the laws of physics relevant to the atmospheric and oceanic circulation, the distribution of heat and the interaction between electromagnetic radiation and atmospheric gases and aeresols . Climate models represent an implementation of  our theoretical knowledge of the climate system, describing interconnections between processes. They consist of different modules describing the atmosphere, oceans, sea-ice/snow and the land surface, and represent the world in terms of boxes stacked next to and on top of each other. The values for temperature, motion and mass are solved in each of these boxes, based on well known physical la