Earth system models of intermediate complexity: closing the gap in the spectrum of climate system models

We propose a new perspective on the hierarchy of climate models which goes beyond the "classical" climate modeling pyramid that is restricted mainly to atmospheric processes. Most notably, we introduce a new indicator, called "integration", which characterizes the number of interacting components of the climate system being explicitly described in the model. The location of several model types, from conceptual to comprehensive, is presented in a new spectrum of climate system models. In particular, the location of Earth system Models of Intermediate Complexity (EMICs) in this spectrum is discussed in some detail and examples are given, which indicate that there is currently a broad range of EMICs in use.