By Agence France-Presse
Even modest temperature rises agreed under international plans to limit climate disasters could see ice caps melting enough this century because their loss became "irreversible", experts warned Monday.
The 2015 Paris Agreement limits countries to rising temperatures "far below" two degrees Celsius (3.6 degrees Fahrenheit) above pre-industrial levels and less than 1.5C if at all possible.
The average gain of 1.5-2C hotter in 2100 is the best scenario for scientists based on consumption of natural resources and burning fossil fuels, and will require radical changes in global lifestyles to be achieved.
In comparison, the business as usual human approach – if we continue to emit greenhouse gases at the current pace – will see as much as 4C of geothermal heat.
Scientists have known for decades that the Greenland and Antarctic ice sheets are shrinking, but it is assumed that they will survive with a relatively intact 1.5-2C temperature rise.
However, according to a new analysis published in the journal Nature Climate Change, even simple global warming can cause irreversible damage to polar ice, which contributes to a catastrophic increase in sea level.
"We say that 1.5-2C is nearing the limits of a more dramatic effect might be expected from the ice sheet," Frank Pattyn, head of the geoscience department, Brussels Free University and leading study author, told AFP.
His team processed data on annual temperature rises, ice sheets and known melting rates and found that Greenland and Antarctic ice sheets would reach a "tipping point" around 2C.
"The existence of tipping points implies that changes in ice sheets are potentially irreversible – returning to pre-industrial climates may not stabilize the ice sheet after the critical point has been crossed," Pattyn said.
'Tipping point of the century'
Ice found in Greenland and Antarctica contains enough frozen water to lift the global sea level several meters.
The Greenland ice sheet itself has contributed 0.7 millimeters to global sea level every year since the mid-1990s.
And the poles heat up faster than anywhere else on Earth, with Greenland alone 5C is warmer in winter and 2C in summer since then.
Even though scientists estimate it will take hundreds of years for them to melt even with the huge increase in global temperatures, Monday's study provides further concern about real human plans just to avoid uncontrolled warming.
Many models of the 1.5-2C scenario allow the threshold to be breached in the short term, potentially heating the planet a few degrees higher, before using carbon capture and other technologies to bring the temperature back to line in 2100.
The study warns against this approach, however, saying that feedback loops triggered by higher temperatures will "cause the entire ice sheet to melt independently" even if the increase is then offset.
For Greenland, the team said with 95 percent certainty that the decline in the main ice sheet would occur at a 1.8C heating value.
"For Greenland and Antarctica, the tipping point is known to be the level of warming that can be achieved before the end of the century," Pattyn said.