A U.S. researcher says projected sea-level rise over the next century has been underestimated because current models fail to consider several critical feedbacks that might accelerate rising seas in the coming decades. While the 2007 report of the Intergovernmental Panel on Climate Change predicted that global sea levels could rise 0.2 to 0.5 meters by 2100, current projections suggest that seas could rise a meter or more. One of the factors ignored by earlier models, says University of Colorado geologist Bill Hay, is the influx of warm, briny ocean water into the Arctic that occurs when melting fresh water is released, a phenomenon he says acts as a sort of “heat pump” in the Arctic, adding more ice-free waters, which then absorb more solar energy. According to Hay, who will present his findings at the annual meeting of The Geological Society of America, another factor that was ignored is the potential melting of large ice sheets in Greenland and western Antarctica. A third feedback, he said, is the vast amounts of groundwater being removed to address humankind’s surging water needs, much of which ultimately ends up in the oceans.