These words, sung by King George III in the musical “Hamilton,” are in reference to the newly freed United States. However, they would not be out of place in a description of a chilling new study done on the West Antarctic ice sheet.
The study, published in the magazine Nature on March 31, suggests that, in a worst case scenario, Antarctic melting alone could raise global sea levels by around 64 to 114 centimeters (25 to 44 inches) by 2100. Combine that amount with the expansion of warming sea water and melting of other glaciers and sea levels could rise 1.5 to 2.1 meters by the century’s end. That is nearly double previous predictions, including the one made by the United Nations’ Intergovernmental Panel on Climate Change, which was also a worst case scenario.
The West Antarctic ice sheet, a remnant from the last ice age that is larger than Mexico, would experience the majority of that melting.
“We are not saying this is definitely going to happen,” David Pollard, a co-author of the paper from Pennsylvania State University, told the New York Times. “But I think we are pointing out that there’s a danger, and it should receive a lot more attention.”
Such a rise would put the world’s coastlines and many of its larger cities underwater. New York City, Miami, London, Venice, Shanghai, Hong Kong and many others would be in danger.
“Can we build walls and levees and dikes fast enough to keep up with that? One concern would be that at that point you’re sort of looking at managed retreat essentially, rather than geoengineering in a lot of places,” Robert DeConto, a co-author of the study from the University of Massachusetts Amherst, told CNN.
These predictions are based on improvements of an existing computerized model of Antarctica. The scientists used data from two previous warm periods, one 125,000 years ago and the other three million years ago, to fine-tune the program. These warm eras shrank many of Earth’s ice sheets and led to sea level rising 20 to 30 feet higher than today’s levels. The improvements capture a number of new factors that scientists believe could endanger the ice sheets stability.
With the information gleaned from these previous climate periods in the model, scientists were able to reproduce past changes in sea level for the first time. Reproducing those previous periods gives the scientists more confidence in their results.
Even so, the model is not a definitive predictor.
“You could think of all sorts of ways that we might duck this one,” Richard B. Alley, a glaciologist at Pennsylvania State University, told the New York Times. “I’m hopeful that will happen. But given what we know, I don’t think we can tell people that we’re confident of that.”
The model is based on a business as usual approach to greenhouse gas emissions. It predicts that Antarctic melting would accelerate around 2050, when rising temperatures would cause part of the ice sheet to disintegrate. Once the ice sheet breaks apart, the melting speed would continue to increase, reaching a pace of a foot a decade in the middle of the 22nd century.
With many of the world’s major cities below sea level in this scenario, many people may find themselves without a place to live.
“I haven’t seen anyone mention the long, slowly unfolding refugee crisis that will only get worse as hundreds of millions [of people] are displaced worldwide,” said Maureen Raymo, a marine geologist at Columbia University’s Lamont-Doherty Earth Observatory.
While the warnings are dire, there is some hope. The model represents a worst case scenario of no reduction in carbon emissions. It does not take into account future policy decisions that could curb future emissions and slow down the ice sheet’s melting.
“This study is suggesting the worst-case scenario might be worse than we were thinking a few years ago, but it still highlights that policy is going to play a really big role in which future path we go down in terms of sea level rise. The horse isn’t completely out of the barn yet,” DeConto said.
Still, even if countries were to implement emission curbing policies, battling the West Antarctic ice sheet melting would be an uphill climb.
“Even if their dire predictions are cut in, let’s say, half, we are still going to have serious problems in coastal cities,” said chief of NASA’s Ocean Ecology Laboratory Carlos Del Castillo of the research. “Sea level rise is not getting the attention it deserves. It has clear and serious implications to our way of life.”
