Earth system models simulate all relevant aspects of the earth system. It includes physical, chemical and biological processes. With the ESM, we reach far beyond the global climate models (GCM), which simply represented the physical atmospheric and oceanic processes.
In fact, the climate system is driven by more than the physical processes traditionally modeled, such as wind, clouds, earth surfaces, oceans and ice. The concentration of greenhouse gases and aerosols is not only affected by man-made emissions. They are also involved in physical reactions and mutually affect the Earth's biological components, and are strongly associated with the climate system.