New York Times: Greenland’s ice sheet represents one of global warming’s most disturbing threats. The vast expanses of glaciers – massed, on average, 1.6 miles deep – contain enough water to raise sea levels worldwide by 23 feet. Should they melt or otherwise slip into the ocean, they would flood coastal capitals, submerge tropical islands and generally redraw the world’s atlases. The infusion of fresh water could slow or shut down the ocean’s currents, plunging Europe into bitter winter. Yet for the …