Rising seas could affect three times more people by 2050 than previously thought, according to new research, threatening to all but erase some of the world’s great coastal cities. The authors of a paper published Tuesday developed a more accurate way of calculating land elevation based on satellite readings, a standard way of estimating the effects of sea level rise over large areas, and found that the previous numbers were far too optimistic. The new research shows that some 150 million people are now living on land that will be below the high-tide line by midcentury. Southern Vietnam could all but disappear. The first map shows earlier expectations of submerged land by 2050. But the new outlook, the second map, indicates that the bottom part of the country will be underwater at high tide. More than 20 million people in Vietnam, almost one-quarter of the population, live on land […]