A numerical model that simulates the coupled dynamics of the atmosphere and ocean for climate studies.A coupled general circulation model (CGCM) is a computer simulation that represents the atmosphere and ocean as interacting fluid systems, along with land and ice components, to study climate. Unlike simpler models, it solves the fundamental equations of fluid motion and thermodynamics on a global grid, allowing it to simulate large-scale circulation patterns, ocean currents, and their mutual influences. These models are the primary tools for projecting future climate change and understanding past climate variability.
The first coupled atmosphere-ocean general circulation models emerged in the late 1960s and 1970s, with pioneering work by Syukuro Manabe and Kirk Bryan at NOAA's Geophysical Fluid Dynamics Laboratory. These early models were coarse and simplified, but they laid the foundation for modern climate projections.
The model divides the atmosphere and ocean into three-dimensional grids and computes how temperature, pressure, wind, and currents evolve over time steps. The atmosphere and ocean exchange heat, moisture, and momentum at their interface—for example, winds drive ocean currents, while ocean temperatures influence atmospheric pressure and precipitation. The model runs for simulated decades or centuries, producing a virtual climate that can be compared to observations and used for experiments.
CGCMs underpin the Intergovernmental Panel on Climate Change (IPCC) reports, providing projections of temperature rise, sea-level change, and extreme weather under different greenhouse gas emission scenarios.
Modern CGCMs run on supercomputers that can perform quadrillions of calculations per second, yet they still approximate clouds and small-scale turbulence rather than simulating them directly.



















