A series of general circulation model simulations are used to quantify the relative contributions of land surface and ocean variability to variability in precipitation. The simulations show that land surface processes contribute significantly to the variance of annual precipitation over continents. In contrast, ocean processes acting alone have a much smaller effect, particularly in midlatitudes. The precipitation variability reflects local evaporation variability and associated hydrological persistence, and it responds most strongly to the land surface during summer, when noise convection dominates.