A coupled ocean-atmosphere general circulation model is used to simulate the climates of today and the last glacial maximum (LGM). The model, which does not require artificial flux adjustments, produces a pattern of cooling at the LGM that is broadly consistent with the findings from simpler models and palaeoclimatic data. However, changes to the ocean circulation produce anomalously warm LGM surface conditions over parts of the North Atlantic, seemingly at odds with palaeoceanographic data. The thermohaline circulation is intensified for several centuries, as is the northward heat transport in the Atlantic equatorward of 55¿N, but this may be a transient result. Mechanisms that lead to this response are discussed. ¿ 2001 American Geophysical Union