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Sustained greenhouse gas emissions could cause global sea levels to rise by nearly 16 inches this century as the ice sheets in Antarctica and Greenland continue to melt, a major international study concluded Thursday.
The gigantic ice caps contain enough frozen water to raise the oceans to 65 meters, and researchers are increasingly concerned that their melt rates are following the UN worst-case scenario for rising sea levels.
Experts from more than three dozen research institutions used ocean temperature and salinity data to make multiple computer models that simulated possible ice loss from glaciers in Greenland and Antarctica.
They tracked two climate scenarios: one where humanity continues to pollute at current levels, and one where carbon emissions are drastically reduced by 2100.
They found that, in the high emissions scenario, the loss of ice in Antarctica would cause the sea level to rise 30 cm by the end of the century, with Greenland contributing an additional 9 cm.
Such an increase would have a devastating impact around the world, increasing the destructive power of storm surges and exposing coastal regions that are home to hundreds of millions of people to repeated and severe flooding.
Even in the lowest emissions scenario, the Greenland layer would raise the oceans by around 3 cm by 2100, beyond what is already destined to melt due to the additional 1C of warming that humans have caused in the industrial age.
“It’s not so surprising that if we heat the planet more, more ice will be lost,” said Anders Levermann, an expert on climate and ice sheets at the Potsdam Institute for Climate Impact Research.
“If we emit more carbon into the atmosphere, we will have more ice loss in Greenland and Antarctica,” he told AFP.
“We have in our hands how fast we let sea level rise and how much we let it rise eventually.”
Beating predictions
Until the early 21st century, the West Antarctic and Greenland ice sheets generally accumulated as much mass as they shed. The runoff, in other words, was offset by fresh snowfall.
But over the past two decades, the increasing pace of global warming has upset this balance.
Last year, Greenland lost a record 532 billion tons of ice, the equivalent of six Olympic pools of cool, cool water that flow into the Atlantic every second. This runoff accounted for 40 percent of sea level rise in 2019.
The UN’s Intergovernmental Panel on Climate Change (IPCC) in a special report on Earth’s icy spaces predicted last year that the melting of Greenland could contribute 8 to 27 cm to ocean levels by 2100.
He estimated that Antarctica could add 3-28 cm above that.
A study published earlier this month in Nature Climate Change said that the mass already lost to melting ice and melting ice between 2007 and 2017 lines up with the most extreme IPCC forecasts for the two leaves.
They also predicted a maximum sea level rise of 40 cm by the year 2100.
The authors of Thursday’s research, published in a special issue of The Cryosphere Journal, said it highlighted the role emissions will play this century in the world’s seas.
“One of the biggest uncertainties when it comes to how much sea level will rise is how much the ice sheets will contribute,” said project leader Sophie Nowicki of the University at Buffalo.
“And the contribution of the ice sheets really depends on what the climate will do.”
Levermann said the uncertainty in the projections “cannot be a reason to wait and see” in terms of emissions cuts.
“We already know something will happen. We just don’t know how bad it will get.”
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