The utility of Earth system Models of Intermediate Complexity

Intermediate-complexity models are models which describe the dynamics of the atmosphere and/or ocean in less detail than conventional General Circulation Models (GCMs). At the same time, they go beyond the approach taken by atmospheric Energy Balance Models (EBMs) or ocean box models by using sophisticated parameterizations of the unresolved flow or by explicitly resolving the equations of geophysical fluid dynamics albeit at coarse spatial resolution. Being computationally fast, intermediate-complexity models have the capability to treat slow climate variations. Hence, they often include components of the climate system that are associated with long-term feedbacks like ice sheets, vegetation and biogeochemical cycles. Here again they differ from conventional GCM-type models that feature only atmosphere and ocean/sea-ice components. Many different approaches exist in building such a reduced model, resulting in a ‘spectrum of Earth system Models of Intermediate Complexity closing the gap between EBMs and GCMs’