Sea levels could rise twice what was previously anticipated during the 21st century, according to a new study that factors in emerging research about the unstable Antarctic Ice Sheet.
The study, published in the open access journal Earth’s Future, addresses newly prominent worries, like the disintegration of floating ice shelves and widespread ice-cliff failure, which could lead to the sudden collapse of parts of the East Antarctic Ice Sheet. If the ice sheet were to collapse and melt completely, which had previously seemed highly unlikely, it would cause sea levels worldwide to rise almost 200 feet.
The study goes on to lay out new projections for sea levels city by city around the world, which could be far more dire than originally predicted.
The U.N. Intergovernmental Panel on Climate Change (IPCC) projects a median sea level rise of two feet and five inches by 2100 under a high emissions scenario. By contrast, the new Earth’s Future study, as reported by Mashable, offers a median sea level rise projection of four feet and nine inches during the 21st century if greenhouse gas emissions continue on their current high trajectory.
National Geographic explains that the ice covering East Antarctica, which is more than 12,000 feet thick in many places, has long been considered more stable and permanent than the West Antarctic Ice Sheet, and was therefore less susceptible to global warming. However, in addition to the study in Earth’s Future, a team of researchers from the University of Texas at Austin and the University of South Florida published a paper in the journal Nature on Thursday, which found that the East Antarctic Ice Sheet may not be as stable as it seems.
The Earth’s Future study highlights that there are still ways to cut greenhouse gas emissions over the next several years to significantly reduce the possibility of a sea level rise calamity after 2050. If temperature targets that were set out in the Paris Climate Agreement are met, triggering a rapid Antarctic meltdown is less likely, the Earth’s Future study found.
Without protective measures, the study predicts, land currently home to 153 million people would be submerged—or at least half the population of the U.S., as Mashable points out.