Earth's ice sheets tracking worst-case climate scenarios

PARIS, France, September 1 ------ The Greenland and Antarctic ice sheets, which hold enough frozen water to lift oceans 65 meters, are tracking the UN's worst-case scenarios for sea level rise, researchers said Monday, highlighting flaws in current climate change models. Mass loss from 2007 to 2017 due to melt-water and crumbling ice aligned almost perfectly with the Intergovernmental Panel for Climate Change's (IPCC) most extreme forecasts, which see the two ice sheets adding up to 40 centimeters (nearly 16 inches) to global oceans by 2100, they reported in Nature Climate Change.

Such an increase would have a devastating impact worldwide, increasing the destructive power of storm surges and exposing coastal regions home to hundreds of millions of people to repeated and severe flooding. That is nearly three times more than mid-range projections from the IPCC's last major Assessment Report in 2014, which predicts a 70-centimetre rise in sea level from all sources, including mountain glaciers and the expansion of ocean water as it warms.

Despite this clear mismatch between the observed reality of accelerating ice sheet disintegration and the models tracking those trends, a special IPCC report last year on the planet's frozen regions maintained the same end-of-century projections for Greenland, and allowed for only a small increase from Antarctica under the highest greenhouse gas emissions scenario. "We need to come up with a new worst-case scenario for the ice sheets because they are already melting at a rate in line with our current one," lead author Thomas Slater, a researcher at the Centre for Polar Observation and Modelling at the University of Leeds, told AFP.

"Sea level projections are critical in helping governments plan climate policy, mitigation and adaptation strategies," he added. "If we underestimate future sea level rise, then these measures may be inadequate and leave coastal communities vulnerable." Ice sheet losses at the upper end of the IPCC forecasts would by itself expose some 50 million people to annual coastal flooding worldwide by mid-century, according to research published last year.

Source: philstar.com