WASHINGTON (CBSDC) — NASA’s former climate chief is warning that coastal cities could “become dysfunctional” if sea levels rise.

James Hansen told CBS News that melting polar ice caps could raise sea levels 15 feet in the next 50 to 100 years, which is five times higher than previous predictions.

“This is the biggest threat the planet faces,” Hansen said. “If we get sea level rise of several meters, all coastal cities become dysfunctional. The implications of this are just incalculable.”

Major American cities that could be affected are New York City, Boston, Miami and Seattle.

Hansen warns weather could become more volatile as the ocean surfaces at the poles cool while the overall climate warms.

“As the atmosphere gets warmer and there’s more water vapor, that’s going to drive stronger thunderstorms, stronger hurricanes, stronger tornadoes, because they all get their energy from the water vapor, Hansen explained to CBS News.

Ten years ago on “60 Minutes,” Hansen said we would reach a “tipping point” if global warming worsened. Now he says we are “at the edge” of that tipping point.

“It will be a situation that is out of our control,” he told CBS News. “We’re essentially at the edge of that. That’s why this year is a critical year.”