One of the most significant contributions to date made by GAIM is the development of techniques and tools for model intercomparison. Whereas individual scientists or modelling groups can and do develop numerical models of various aspects of the Earth System, the value of the results of isolated models is greatly enhanced by comparison with other models. The discrepancies in model results between different approaches to the same problem provide critical insights into model shortcomings, and pave the way for model refinement and improvement. Below are GAIM's major sub-system level model intercomparison projects. These will be continued and finalized in the next few years, and the tools developed through these activities will be applied to the interpretation and assessment of the broader Earth System models (EMIC, C4MIP, CCMLP). As these major GAIM intercomparison activities come to fruition, we will begin to couple the models loosely at first, and then more interactively between 2003 and 2006.