A new study finds that if the Antarctic ice sheets continue to melt at their current rate, more than 20 million Americans will find the land they currently live on under water.

The findings provide a new way to compare emissions scenarios or policies, and "suggest that the long-term viability of hundreds of coastal municipalities and land currently inhabited by tens of millions of persons hang in the balance."

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Paleontological records indicate that global mean sea level is highly sensitive to rises in temperature, and that ice sheets are the most important contributors to large-magnitude sea-level change. As a result, sustained temperature increases are expected to translate to long-term sea-level rise.

Led by Benjamin Strauss of Princeton., N.J.-based Climate Central, an independent organization that researches climate change, the report found that more than 40% of the population living in potentially affected areas reside in the state of Florida. The next three most affected states are California, Louisiana, and New York, which demonstrates the wide geographic distribution of the at-risk areas. The areas in danger include at least 21 cities exceeding a population of 100,000.

According to the report,  more than half of the towns and cities in  the danger area could avoid becoming mostly submerged if carbon emissions are cut aggressively. However, it also said that contemporary carbon emissions, "even if stopped abruptly, will sustain or nearly sustain near-term temperature increases for millennia." This is due the slow exchange of heat between the ocean and the atmosphere.

The authors of the report say that with aggressive carbon cuts, more than half of the towns and cities potentially affected would be spared if the West Antarctic Ice Sheet remains stable.

"Although past anthropogenic emissions already have caused sea-level commitment that will force coastal cities to adapt," the report said, "future emissions will determine which areas we can continue to occupy or may have to abandon."

The research was published in the Proceedings of the National Academy of Sciences.

TagsRising Sea Levels Could Displace 20 Million Americans by 2100, Antarctic ice sheets, global warming, sea level rise, Benjamin Strauss, Climate Central, emissions, Carbon emissions