The Atlantic’s Meridional Overturning Circulation (AMOC) is weak when the northern summer insolation is strong and vice-versa in the 23-kyr precessional frequency band. The mechanism behind this response is unknown and does not conform in any obvious way to Milankovitch theory. The link between the AMOC and precession is attributed here to the trade winds that blow out from Africa across the Atlantic. The trade winds, like the AMOC itself, are weak when the northern summer insolation is strong. The trade winds are shown here to have a direct impact on the AMOC’s return flow. A return flow altered this way should warm and cool the Earth in a way that has not been previously considered.