A computer program that is used by atmospheric scientists to study and predict world-wide trends in weather patterns and the forces and physical laws that affect climate. The formulae are complicated and require skilled mathematicians, atmospheric scientists, and powerful computers for execution. Five regimes that influence climate are often taken into consideration: atmosphere, hydrosphere, biosphere, cryosphere, and pedosphere. Atmospheric and environmental physical laws as well as principles of thermodynamics and hydrodynamics are all used as part of the extensive mathematical parameters for the program. The results of these models are used as reference for other models, policy decisions, and by meteorologists. [Climate Change; v23: pp. 337-377: 1993.] [Climate Change; v21: pp. 345-346: 1992.]