We face many big questions in Earth System Science, concerning regional and global changes, past and future. Alongside theoretical, laboratory and observational analyses, we rely heavily on a wide range of computational models to address these questions. The “GCM” family of models can be regarded as “complex”, in most faithfully representing one or more components of the Earth System, but these models are expensive to use and demand a high degree of patience in the user! Alternatively, Earth System Models of Intermediate Complexity (EMICs) more efficiently and completely simulate Earth System behaviour, but such models demand a high degree of imagination in both design and use. One such EMIC is GENIE. A brief history of GENIE development is followed by examples of recent research highlights (warm Eocene climates; Quaternary glacial cycles; next-millennium climate scenarios), and an outline of the GENIE experiments to be undertaken during a sabbatical visit to RSES (addressing “The Southern Ocean in a dynamic climate system”).