For millennia, the Atlantic Meridional Overturning Circulation has served as one of Earth's great thermal engines, carrying warmth northward and returning cold water south in a loop that quietly governs the climate of entire continents. Now scientists observe that engine slowing — marked by a persistent cold spot between Spain and Greenland that deepens even as the rest of the world warms. The anomaly is not noise in the data; it is a signal, and what it points toward is a system under stress. History reminds us that when Atlantic currents have shifted before, they did not drift — they lurched