SOURCE: Pacific Standard and New York Times
DATE: January 25, 2019
SNIP: This week, researchers warned that Greenland’s ice sheet has reached a tipping point. Looking at more than a decade’s worth of ice loss, an international team of scientists found that the rate of Greenland’s ice loss in early 2013 was four times higher than in 2003.
[I]n this new study, Michael Bevis, a professor at Ohio State University, and his colleagues were surprised to see that most of the ice loss occurred in the southwest corner of Greenland, a region with very few glaciers. In other words, most of the ice loss was in the form of meltwater runoff, draining from land-based ice sheets into the sea.
What Bevis and his colleagues found was that the melting was being controlled by something called the North Atlantic Oscillation—an irregular fluctuation in atmospheric pressure over the Atlantic Ocean that influences the weather on several continents.
“Global warming brought summertime temperatures just shy of the critical temperature at which massive melting would occur, and the NAO pushed it over this critical threshold,” he says. It means that the ice sheet is now sensitive to small fluctuations in summer temperatures, and if global temperatures continue to rise as predicted, soon Greenland’s summers will be warm enough to cause massive melting regardless of the NAO’s phase.
The new research dovetails with other recent papers on the accelerating melting. Last month a team of researchers published a paper in Nature that used satellite observations, analysis of ice cores and models to show that losses from the Greenland ice sheet have reached their fastest rate in at least 350 years.
Earlier this month, researchers reported in the journal Science that the oceans are warming about 40 percent faster than the United Nations’ climate panel predicted just a few years ago. Last year, a climate scientist told the Guardian that the Antarctic ice sheet is now melting at a “surprising” and accelerating rate. Bevis agreed that recent years have produced a “whole series of papers saying that the impacts of global warming have been underestimated and they are happening faster than expected.”
While melting ice sheets and sea-level rise get lots of attention, Michael Mann, a climate scientist at Penn State University, points out that climate change is also already having dramatic effects on extreme summertime weather events. Mann writes in an email, “the climate models have likely underestimated the impact that climate change is already having on extreme weather events like the devastating events that unfolded in [the summer of] 2018 and they are likely underestimating the future increases in these events.”
[I]t’s becoming ever more clear that, without immediate and drastic action, the worst-case climate scenario will become the rule rather than the exception.