Global seas could rise nearly twice as much as previous, widely accepted estimates, according to a study published on Thursday saying low-lying cities face possible disaster by the end of the century.
Sea levels could surge more than three feet (0.9 meter) by 2100 from melting Antarctic ice alone, on top of a three-foot rise already predicted, said the study by two American researchers that appeared in the science journal Nature.
That same Antarctic ice melt could add nearly 50 feet (15 meters) of sea-level rise by the year 2500, it said.
The earlier, commonly accepted prediction was made by the United Nations Intergovernmental Panel on Climate Change in 2013 estimating global sea levels rising more than three feet by 2100.
Children swim along the coast of the Indian Ocean near Mogadishu.
"This could spell disaster for many low-lying cities," said co-author Robert DeConto, professor of geosciences at the University of Massachusetts at Amherst, in a statement.
Boston, for example, could see about five feet of sea level (more than 1.5 meters) at the end of the century, he said.
Other low-lying cities often cited as being in jeopardy of rising sea levels include London, New York, Shanghai, Hong Kong, Sydney, Australia and Venice, Italy.
The findings should sound an alarm bell for more greenhouse gas emission cuts, said co-author David Pollard, a senior scientist at Pennsylvania State University's Earth and Environmental Systems Institute.
While the findings are "worst-case" possibilities, they "should be considered seriously," he said.