“When you look at the historical record, there’s no trend saying the flooding is going down,” said Dr. Sweet, the NOAA expert. “The trends are all very clear. They’re going up, and they’re going up in many of these areas in an accelerating fashion.”
Late last year, in Paris, nations reached a landmark global agreement to cut emissions. It is fragile, and might not survive if Donald J. Trump is elected president in November; he has pledged to scrap it.
But the air is already so full of greenhouse gases that most land ice on the planet has started to melt. So even if the deal survives, it will, at best, slow the rise of the sea and perhaps limit the ultimate increase. Many climate scientists, including Dr. Dutton, believe a rise of at least 15 or 20 feet has already become inevitable, over an unknown period.