Their study, published in the journal Nature, is based on the simulations of the changes in the Greenland ice sheet from the beginning of the Holocene epoch, some 12,000 years ago, and extending forward 80 years to 2100.
Results show that although the current rate of ice loss in Greenland is comparable to the highest rates during the Holocene, the researchers believe future rates are likely to exceed them.
Describing their findings as “yet another wake-up call”, they say the study highlights the “extreme and unusual” projected Greenland ice sheet losses for the 21st century.
We've altered our planet so much that the rates of ice sheet melt this century are on pace to be greater than anything we've seen under natural variability of the ice sheet over the past 12,000 years
Lead author Jason Briner, a professor of geology at the University at Buffalo College of Arts and Sciences, said: “Basically, we’ve altered our planet so much that the rates of ice sheet melt this century are on pace to be greater than anything we’ve seen under natural variability of the ice sheet over the past 12,000 years.
“We’ll blow that out of the water if we don’t make severe reductions to greenhouse gas emissions.”
The melting of Greenland’s ice sheet is currently causing sea levels to rise by about 0.7 millimetres per year, but models predict it could reach somewhere between 2-7 millimetres per year by 2100.
A rise in sea levels would see many cities around the world exposed to coastal flooding.
In their simulations, the researchers found that the largest ice mass losses in the past, between 10,000 and 7,000 years ago, were at rates of around 6,000 billion tonnes per century.
This is similar to the estimated rates of the first two decades of this century (2000–2018) of around 6,100 billion tonnes per century, the researchers said.
However, projected mass losses for the rest of this century are expected to exceed those maximum rates, they added.
In the scenario with the lowest greenhouse gas emissions (RCP2.6), the predicted mass loss is around 8,800 billion tonnes per century, which increases to around 35,900 billion tonnes in the scenario with the highest emissions (RCP8.5).
The amount of ice loss this century could reverse 4,000 years of cumulative ice growth, the researchers said.
But according to Prof Briner, it is still possible for countries around the world to make a difference by cutting emissions.
He said: “If the world goes on a massive energy diet, in line with a scenario that the Intergovernmental Panel on Climate Change calls RCP2.6, our model predicts that the Greenland ice sheet’s rate of mass loss this century will be only slightly higher than anything experienced in the past 12,000 years.
“But more worrisome is that under a high-emissions RCP8.5 scenario – the one the Greenland ice sheet is now following – the rate of mass loss could be about four times the highest values experienced under natural climate variability over the past 12,000 years.”
