Published in peer-reviewed journal Nature this past week, a new study has found that the melt rate from the Himalayas, along with other high-elevation Asian mountains, is significantly lower than figures other studies have proposed.
Co-authored by Thomas Jacob, John Wahr, W. Tad Pfeffer, and Sean Swenson, the study relied on gravitational satellite monitoring, a deviation from more traditional ground studies done by scientists. The study’s findings are an even more prominent deviation, suggesting that from 2003 to 2010, the Himalayan ice melt was 4 billion tons a year, as opposed to the 50 billion tons a year that some scientists originally estimated.
That’s the good news. The bad news? The study confirmed old evidence that Antarctica and Greenland are melting at a rate of approximately 385 billion tons a year, making them the major players in the battle with ice melt.
“It’s Greenland and Antarctica that pose by far the greatest threat to rising sea levels in the future,” said Wahr in an interview with MSNBC. “That’s, basically, where all the ice is.”
And unfortunately, there’s more bad news. The discrepancies between previous and recent data support the stance of nonbelievers who claim that studies on glacial melting and global warming rates have been conflicting and spotty.
Yet the study’s authors account for the difference.
“Most previous global mass balance estimates for GICs [glaciers and ice caps] rely on extrapolation of sparse mass balance measurements representing only a small fraction of the GIC area,” reads the abstract, “leaving their overall contribution to sea level rise unclear.”
The authors go on to warn about extrapolation in their own study, noting that inconsistency and changing factors in the region make data from the time period examined obsolete when predicting future melt rates.
However, while the study may not indicate future trends, it may change how future trends are calculated. The study’s technique relied on a satellite, christened GRACE, that “[mapped] out the Earth’s gravity field, all over the globe, every month,” according to Wahr.
The method’s basic mechanism is surprisingly simple. As Wahr explains, “One way to think of this is that as GRACE passes over Alaska, say, it feels the gravitational pull of all the Alaskan glaciers. When it passes over Alaska later on, it also feels the pull of all those glaciers, but now that pull is smaller because there is less mass in those glaciers to do the pulling. So you end up learning about the change in the cumulative mass of all those glaciers. You don’t miss any of the glaciers; you see the combined effects of all of them.”
Those “combined effects,” he added, are one of the drawbacks to the method, though. The satellite makes scientists unable to isolate the effects of an individual glacier.
Yet the study’s overall impact is not getting bogged down by the details. Scientists and concerned members of the public alike stress that while melt rate figures are more optimistic than originally presumed, they still pose a global problem, requiring global effort and global cooperation.
Photo Credit: wikimediafoundation.org/wiki/File:Himalayas-Lhasa11.JPG