In the latest study, a team of scientists discovered that millions of Americans may already live on land that is destined to be reclaimed by the sea.

While some locations are only at risk of flooding, others are doomed to flood in the distant future. However, the process could speed up due to the rise of carbon dioxide emissions and the destabilization of West Antarctica’s ice sheet.

“Future emissions will determine which areas we can continue to occupy or may have to abandon,” note the report’s researchers, led by Benjamin Strauss of Climate Central in Princeton, N.J. The research appeared Monday in the Proceedings of the National Academy of Sciences and was co-authored by Scott Kulp of Climate Central and Anders Levermann of the Potsdam Institute for Climate Impact Research in Germany.

The research states: “Carbon choices determine US cities committed to futures below sea level.” For every one degree Celsius of warming, the scientists estimate that the sea-level will rise about 2.3 meters over the next 2,000 years. However, there is a possibility that it could happen sooner.

Using the link between climate warming and eventual ice melt, the researchers estimate that with current carbon emissions, the world is already destined to see the sea-level rise 1.6 meters – more than five feet. That isn’t taking into consideration the increase of carbon emissions that will exist in the future, which could make the sea-level rise by more than seven feet.

If no action is taken on climate change, the locations of over 26 million Americans could be flooded with more than 1,500 U.S. cities and municipalities overrun with water.

“If we don’t cut emissions,” Strauss said, “we’re talking about losing American land [that’s] home to more people than live in any state, except for California and Texas. Home to more people than the state of Florida and New York.”

The authors of the study also directly acknowledge gaps in the research. This includes cities that have taken steps to deal with extreme flooding scenarios like New Orleans’ 26-foot-high sea wall. Louisiana is also contemplating diversions of the Mississippi River that would not only create new wetlands, but keep pace with the rising seas. This means that as the sea-levels slowly rise, cities might be able to adapt.