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Coastal flooding is about to get dramatically more frequent around the world as sea levels rise from global warming, researchers said Thursday. Phys.Org reports, "A 10-to-20 centimeter (four-to-eight inch) jump in the global ocean watermark by 2050 -- a conservative forecast -- would double flood risk in high-latitude regions, they reports in the journal Scientific Reports." From the report: Major cities along the North American seaboard such as Vancouver, Seattle, San Francisco and Los Angeles, along with the European Atlantic coast, would be highly exposed, they found. But it would only take half as big a jump in ocean levels to double the number of serious flooding incidents in the tropics, including along highly populated river deltas in Asia and Africa. Even at the low end of this sea rise spectrum, Mumbai, Kochi and Abidjan and many other cities would be significantly affected. To make up for the lack of observational data, Vitousek and his colleagues used computer modeling and a statistical method called extreme value theory. "We asked the question: with waves factored in, how much sea level rise will it take to double the frequency of flooding?" Sea levels are currently rising by three to four millimeters (0.10 to 0.15 inches) a year, but the pace has picked up by about 30 percent over the last decade. It could accelerate even more as continent-sized ice blocs near the poles continue to shed mass, especially in Antarctica, which Vitousek described as the sea level "wild card." If oceans go up 25 centimeters by mid-century, "flood levels that occur every 50 years in the tropics would be happening every year or more," he said.