Experts make dire prediction about sea levels

In the future, there could be major flooding along every coast. So says a new study that warns the world's seas are rising.

Ever-warming oceans that are melting polar ice could raise sea levels 15 feet in the next 50 to 100 years, NASA's former climate chief now says. That's five times higher than previous predictions.

"This is the biggest threat the planet faces," said James Hansen, the co-author of the new journal article raising that alarm scenario.

"If we get sea level rise of several meters, all coastal cities become dysfunctional," he said. "The implications of this are just incalculable."

If ocean levels rise just 10 feet, areas like Miami, Boston, Seattle and New York City would face flooding.

The melting ice would cool ocean surfaces at the poles even more. While the overall climate continues to warm. The temperature difference would fuel even more volatile weather.

"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," said Hansen.

Nearly a decade ago, Hansen told "60 Minutes" we had 10 years to get global warming under control, or we would reach a "tipping point."

"It will be a situation that is out of our control," he said. "We're essentially at the edge of that. That's why this year is a critical year."

Critical because of a United Nations meeting in Paris that is designed to reach legally binding agreements on carbons emissions, those greenhouse gases that create global warming.