Scientists Find Greenland Ice Sheet's Point of No Return

Greenland's ice sheet, one of only two permanent ice sheets on Earth, loses a reported 33 million tons of ice every hour, or almost 290 billion tons per year. Hovering at around 650,000 square miles, it has not yet reached an irreversible tipping point, where its collapse—and a possible 23 feet of sea level rise that could result—is inevitable, a new study claims, per Phys.org. But it finds we're edging dangerously close to that point. Researchers say the Greenland ice sheet will hit its tipping point when the planet warms another 3.5 degrees Fahrenheit above pre-industrial levels, per Live Science. Under the worst warming estimates, that scenario could happen within the next 75 years.

Their analysis of this tipping point involved using a climate model to simulate snow buildup and loss over time under different warming conditions. Under one scenario, researchers found collapse would occur a relatively short time (between eight and 40,000 years) after 253.5 billion tons of ice was lost in one year—as is apparently now happening. This represents "a 60% decrease from the ice sheet's pre-industrial equilibrium," per Live Science. However, this outcome was tied to global temperatures rising 6.12 degrees F (3.4 degrees Celsius) above pre-industrial levels, according to the study published last month in the Cryosphere. Though we are currently baking at around 2.65 degrees F above pre-industrial levels, the more dire estimates indicate we will hit 6.12 degrees by 2100.

Not all hope is lost as recent research indicates the ice sheet could rebound if global warming lingers around 3.6 degrees above pre-industrial times, as outlined under the Paris climate agreement. However, our estimates aren't always correct. A study based on satellite imagery, published Jan. 17 in Nature, found Greenland's ice sheet has shed about one-fifth more ice mass in the past 40 years than previously estimated, with most of the loss coming from below sea level. "The loss likely accelerated the movement of ice flowing down from higher elevations, which in turn added to sea level rise," according to NASA's Jet Propulsion Laboratory. (More ice sheet stories.)