Climate models use quantitative methods to simulate the interactions of the atmosphere, oceans, land surface, and ice. They are used for a variety of purposes from study of the dynamics of the climate system to projections of future climate.
All climate models take account of incoming energy as “short wave” electromagnetic radiation from the sun (mostly visible light and short-wave infrared), as well as outgoing energy from the earth (long wave infrared radiation) . Any imbalance results in an eventual change in the average temperature of the earth.
The most talked-about models of recent years have been those relating temperature to emissions of carbon dioxide (see greenhouse gas). These models project an upward trend in the surface temperature record, as well as a more rapid increase in temperature at higher altitudes.
Models can range from very simple to quite complex:
- A simple radiant heat transfer model treats the Earth as one single point and averages all the outgoing energy
- This can be expanded vertically or horizontally. If expanded vertically, the model becomes a radiative-convective model.
- Finally, fully coupled global climate models combine separate models for the atmosphere, the ocean, the sea ice, and perhaps other components of the climate. These complex models solve the full equations for mass and energy transfers and exchanges of radiant energy on thousands of discrete points that represent the geography of Earth.