Over the next two thousand years, each degree of global warming may lead to sea levels rising by more than 2 meters (6.6 feet), a new study by a group of international researchers said.
According to the research, published in the Proceedings of the National Academy of Sciences, on Monday, melting of mountain glaciers in Greenland and Antarctica will surpass thermal expansion of the ocean as the most dominant contributor to sea levels rising within the next two millennia. Antarctic ice-loss, which currently contributes less than 10 percent to global sea-level rise, will be responsible for half of the increase in the future.
“Global mean sea level has been steadily rising over the last century, is projected to increase by the end of this century, and will continue to rise beyond the year 2100 unless the current global mean temperature trend is reversed,” researchers said in the study.
Burning fossil fuels emit carbon dioxide, or CO2, which stays in the atmosphere for a long period of time, and so does the warming it causes. Thanks to their enormous mass, the oceans and ice sheets respond to this heat very slowly -- the reason why observed sea-level rise is now measured in millimeters each year.
However, according to Anders Levermann of the Potsdam Institute for Climate Impact Research, the lead author of the study, once the oceans and ice sheets are heated out of balance, the melting will not stop.
The study uses early Earth’s climate history and computer simulations of major contributors to global sea-level rise. The researchers also used data from sediments from the bottom of the sea and ancient raised shorelines found on various coastlines around the world.
In the worst case scenario explained in the study, if the global temperature were to rise by 4 degrees Celsius (7.2 degrees Fahrenheit) from pre-industrial times, sea levels will rise by about 9 meters over the next two thousand years, with the Antarctic ice sheet alone contributing more than half, or about 4.8 meters, of the rise.
In addition, Greenland will add another 2.1 meters to the total sea-level rise, while the thermal expansion of the water in the world's oceans will contribute about 1.7 meters. The contribution from mountain glaciers, on the other hand, will decline to about 45 centimeters.
“We need to adapt,” Levermann said in a statement on Monday. “Sea-level rise might be slow on time scales on which we elect governments, but it is inevitable and therefore highly relevant for almost everything we build along our coastlines, for many generations to come.”