 Earth system models of intermediate complexity (EMICs) come in a range of forms but tend to be both comprehensive and highly idealized (Claussen et al. 2002). An EMIC might incorporate not only representations of the atmosphere, ocean, land surface and sea ice, but also representations of some biospheric processes, ice sheets and ocean sediment processes. These representations, however, are often relatively simple or coarse. The atmosphere component of an EMIC, for instance, might be a two-dimensional enhanced version of an EBM known as an energy moisture balance model. The ocean might be simulated explicitly in three dimensions using fluid dynamical equations, but with low spatiotemporal resolution. (See Flato et al. 2013: Table 9.2 and 9.A.2 for examples and further details.) The relative simplicity and coarseness of EMICs makes them computationally efficient, however, which in turn makes it possible to use them to simulate the climate system on millennial time scales.