Daily Climate: Yes, the seas are rising. But by just how much? A concrete answer sure could help coastal cities plan for the future. Problem is, nobody really knows, and a credible number isn’t going to appear anytime soon. But that doesn’t mean public officials should wait for one, warned Michael Oppenheimer, director of Princeton University’s Program in Science, Technology and Environmental Policy. Seas have been rising about 4 millimeters a year, with the Intergovernmental Panel on Climate Change estimating…