That’s what the second author said about a new paper on Greenland’s ice, which arrived just in time for the annual meeting of the signatories of the UN’s 1992 treaty on climate change, this time in Katowice, Poland. Appearing in Nature, Rowan University Geologist Luke Trusel and several coauthors claimed ice-core data from Central-Western Greenland revealed melting in the recent two decades that has been “exceptional over at least the last 350 years.” The paper appeared in the December 6 issue of Nature.
“Our results show a pronounced 250% to 575% increase in melt intensity over the last 20 years” as measured in four ice cores in west-central Greenland. Three of the cores were in the Jakobshavn Glacier, the largest-discharging glacier in the entire Northern Hemisphere. The Ilulissat icefjord, created by the glacier, some 25 miles in length, has historically calved nearly 50 cubic kilometers of ice per year into Disko Bay, near the town of Ilulissat.
They then correlated their ice-core data with a model for ice behavior in all of Greenland. The correlations, while significant, were modest, with the explained variance of the island-wide melting maxing at around 36%. The melt reached its maximum in the very strange summer of 2012, where the amount at the Summit site, near Greenland’s highest elevation, was the largest since the summer of 1889—worth noting because that was well over 100 years ago.
There’s a long-standing quality weather station at Ilulissat, and it certainly shows summer warming of about 2⁰C from its beginning around 1850 to the 1920s.
For a broader comparison, we looked at the summer temperature anomalies for the 5 X 5 degree gridcell that includes Disko Bay and the icefjord. Because it is relatively hospitable and settled, there are a number of stations within the cell so the data is quite reliable. The data we show is from the Climate Research Unit at the University of East Anglia, version HadCRUT4.
There’s very little to see in this temperature record. The authors are well-aware of this and offer a rather unsatisfactory explanation:
The non-linear melt-temperature sensitivity also helps explain why episodes of mid-twentieth-century warmth resulted in less intense and less sustained melting compared to the last two decades, despite being only marginally cooler…Additional factors, such as recent sea-ice losses, as well as regional and teleconnected general circulation changes may also play a part in amplifying the melt response.