Even the modest temperature increases agreed upon under an international plan to limit climate change could cause ice caps to melt enough in this century to make them "irreversible", experts warned on Monday.
The 2015 Paris Accord limits nations to raising the temperature "well below" two degrees Celsius (3.6 degrees Fahrenheit) above pre-industrial levels and less than 1.5 C if possible.
This goal of reaching 1.5-2C warmer by 2100 is the best scenario for scientists based on our consumption of natural resources and the burning of fossil fuels, and will require radical and global changes in lifestyle.
For comparison purposes, today's business approach – if we continue to emit greenhouse gases at the current rate – will see the Earth's heat up to 4 ° C.
Scientists have known for decades that Greenland and Antarctica ice sheets are shrinking, but it was assumed that they would survive a relatively unchanged temperature rise of 1.5 to 2 degrees Celsius.
However, according to a new analysis published in the journal Nature Climate Change, even modest global warming could cause irreversible damage to polar ice, contributing to catastrophic increases in sea level.
"We say that 1.5-2C is close to the limit for which more dramatic effects can be expected from the ice sheets," Frank Pattyn, head of the geosciences department at the Free University of Brussels and lead author of the study, told AFP.
His team analyzed data on annual increases in temperature, ice sheet coverage, and known levels of foundry, and found that both Greenland and Antarctica ice sheets would reach a "tipping point" around 2C.
"The existence of an inflection point implies that changes in the ice sheet are potentially irreversible – returning to a pre-industrial climate may not stabilize the ice sheet once the inflection point has been exceeded," said Pattyn.
"Inflection point in this century"
The ice contained in Greenland and Antarctica contains enough frozen water to raise sea levels by several meters.
Only the Greenland ice sheet contributed 0.7 millimeters to the increase in global sea level every year since the mid-1990s.
And the poles are heating up faster than anywhere else on Earth, with Greenland alone 5C warmer in winter and 2C in summer since then.
Although scientists predict that it would take hundreds of years to melt even with massive global temperature rises, Monday's study provides more reason to worry about humanity's only realistic plan to avoid uncontrolled warming.
Many models in the 1.5-2C scenario allow the limit to be breached in the short term, potentially warming the planet several degrees above, before using carbon capture and other technologies to align temperatures by 2100.
The study warned against this approach, however, saying that a feedback loop triggered by higher temperatures "would lead to self-sustained melting of the entire ice sheet," even if those increases were later offset.
For Greenland, the team said with 95 percent certainty that the biggest decline of the ice sheet would occur at 1.8 ° C of heating.
"For both Greenland and Antarctica, there are turning points for levels of warming that could be reached before the end of this century," said Pattyn.