A 20-Year-Old Climate Mystery Has Finally Been Explained
Penn State professor Michael Mann thought he’d discovered an ocean temperature phenomenon. Now he’s sure—that it doesn’t exist.
Scientists giveth and scientists taketh away.
Michael Mann, distinguished professor of atmospheric science at Pennsylvania State University, came up with a novel term 20 years ago to describe something he and his colleagues had found in their research. About every half-century, wind and waves conspired to warm up or cool down part of the North Atlantic, with probable large-scale effects on weather. Drawing on the same Earth simulations on which most climate research was then based, they concluded that the back-and-forth swing must be a feature intrinsic to the natural system itself. Mann dubbed it the “Atlantic Multidecadal Oscillation,” or AMO.