A series of climate simulations using an atmospheric general circulation model shows that maintaining ocean heat transport at close to present-day values, but with otherwise glacial boundary conditions, leads to an enhanced cooling, particularly in the tropics. This is in agreement with recent geochemical evidence from fossil corals, ground waters, and ice. Near-modern ocean heat transport may have been sustained in all ocean basins during the Last Glacial Maximum in order to balance the formation and export of Glacial North Atlantic Intermediate Water.