The predictions for flooding from climate change just keep getting worse, and now NASA’s former climate chief says the level could be five times what has been predicted int he past.

James Hansen, who co-authored a new journal article that makes alarming claims on the effects of Global Warming, said that melting polar ice could raise sea levels 15 feet in the next 50 to 100 years, according to a CBS News report.

Hansen called it the “biggest threat the planet faces,” according to the report, and that the findings would indicate severe sea level rises that would jeopardize many cities. With a rise of just 10 feet, cities like New York City, Seattle, Boston, and Miami would be drowning.

In addition, we can expect more violent weather as the melting ice cools the poles while the climate overall continues to warm, he argued. The atmosphere getting warmer will result in more water vapor which will drive more thunderstorms and stronger hurricanes and tornadoes.

Hansen said in an interview with “60 Minutes” a decade ago that the Earth had reached a “tipping point,” and leaders would need to get things under control in the next 10 years. Now that that 10 years has passed, Hansen argued that the Earth is at the edge of being out of control, and that this year will be a “critical year.” The stated goal is to keep warming temperatures from rising above an average of 2 percent Celsius worldwide over the next century, a goal that many scientists say is a tall order, but a necessary one.

The United Nations is scheduled to meet in Paris at the end of this year in the hopes that real, practical, and legally binding agreements on carbon emissions can be put into place to stem the warming of the Earth. However, the effort faces an uphill battle, with Global Warming skeptics abounding and many countries feeling like it’s a problem that is many years down the road, or that they are not a big polluter and therefore only the bigger countries should deal with it.