There’s a new lead in the hunt to explain the global warming hiatus. The mystery is why average global surface air temperatures have remained essentially steady since 2000, even as greenhouse gases have continued to accumulate in the atmosphere. Many scientists believe the answer lies in the Pacific, which is sending massive slugs of cold water to the surface, helping cool the planet. But a new investigation, published online today in Science, presents sea temperature data implying that most of the missing heat has been stored deep in the Atlantic. The work draws on tens of millions of ocean temperature and salinity measurements taken globally by buoys, floats, and ships since 1970. Covering 24 depths from the sea surface down to 1500 meters, the data suggest that over the last decade or so the Atlantic has been absorbing heat (red in the graphic above) that would have otherwise warmed the surface. Over the past 14 years, the authors write, water below 300 meters in the North and South Atlantic oceans has stored more energy than the rest of the global oceans combined. “We found the missing heat,” says one of the authors, oceanographer Xianyao Chen of the Ocean University of China in Qingdao. He and co-author Ka-Kit Tung of the University of Washington, Seattle, postulate that the mechanism is the “conveyor belt” current that moves salty tropical water to the North Atlantic, where it sinks, carrying heat with it.