The North Atlantic Oscillation (NAO) is a coherent vacillation in surface temperature and sea-level pressure showing substantial variability over periods up to centuries (Van Loon and Rogers, 1978). It plays a major role in controlling European climate and the North Atlantic ocean, and may play a role in modulating the North Atlantic ecosystems. Hence, it is of great interest to assess how well current coupled models can simulate the variability in the NAO. NAOMIP is a multi-national CMIP sub-project to compare the coupled ocean-atmosphere model simulations of the annual, interannual, and interdecadal variability in the North Atlantic Oscillation from a set of ocean-atmosphere coupled simulations.