Another group of researchers has weighed in on the continuing scientific scuffle over whether the Himalayan glaciers are melting. A letter to Nature Geoscience reports that the Karakoram glaciers, a part of the greater Himalaya north of the actual Himalaya Range, are actually gaining mass. Outside the ice sheets in Greenland and Antarctica, the Karakoram is the most heavily glaciated part of the world, containing nearly 3% of the planet's total ice area. But because they are so large, difficult to get to and dangerous to travel on, they have not been measured by conventional survey methods. Scientists have instead, been relying on satellite measurements, whose accuracy is now called into question. This impressive new study says that the Karakoram glaciers are not only not shrinking, they are accumulating enough ice each year to cause a slight decrease in ocean sea-level.
“Assessments of the state of health of Hindu-Kush–Karakoram–Himalaya glaciers and their contribution to regional hydrology and global sea-level rise suffer from a severe lack of observations,” state Julie Gardelle, Etienne Berthier and Yves Arnaud at the beginning of their new paper appearing in the May 2012, issue of Nature Geoscience. Climate change orthodoxy says that these glaciers should be melting, but there have been many conflicting reports regarding the state of the glaciers in this remote area of Asia—the so called “Karakoram anomaly.” Direct observations are scant and numerous glacier surges in the region change glacier length and velocity complicating the interpretation of available data. This new painstaking study is a significant accomplishment and greatly advances science's understanding of conditions in the region. Here is the authors' summary of their work:
Here, we calculate the regional mass balance of glaciers in the central Karakoram between 1999 and 2008, based on the difference between two digital elevation models. We find a highly heterogeneous spatial pattern of changes in glacier elevation, which shows that ice thinning and ablation at high rates can occur on debris-covered glacier tongues. The regional mass balance is just positive at +0.11±0.22 m yr-1 water equivalent and in agreement with the observed reduction of river runoff that originates in this area. Our measurements confirm an anomalous mass balance in the Karakoram region and indicate that the contribution of Karakoram glaciers to sea-level rise was −0.01 mm yr-1 for the period from 1999 to 2008, 0.05 mm yr-1 lower than suggested before.
Gardelle et al., observed the geodetic mass balance for a 5,615 km2 ice-covered area in the Karakoram region. They studied the area's spatial variability and estimated the contribution such change would make to sea-level rise. “We measured regional changes in ice elevation by differencing two digital elevation models (DEMs) generated from the February 2000 Shuttle Radar Topographic Mission (SRTM) and from Satellite Pour l’Observation de la Terre (SPOT5) optical stereo imagery acquired in December 2008. Mean elevation changes are then converted into mass balance by assuming a density of 900 kg m-3 both in the accumulation and ablation areas,” the paper explains. The area under study is shown below.
Not that performing the required measurements was a simple matter. Many of the subject glaciers are known or suspected to have surged in the past and the distribution of elevation changes is far from homogeneous. Many of the glaciers show strong thinning and thickening rates of up to 16 m yr−1 in either direction, requiring each glacier to be analyzed individually. They also found that studies using the Gravity Recovery and Climate Experiment (GRACE) project data to infer the change in glacier mass in central Asia led to conflicting results.
In a News & Views article in the same journal issue, Graham Cogley, a geologist at Trent University, hails the work by Gardelle et al. as having “removed the question mark.” Recapping the new results in greater detail, Cogley goes on:
Building on the hard-won but limited field observations, Gardelle and colleagues used remote sensing to measure glacier mass changes in the Karakoram. Specifically, they subtracted an earlier digital elevation model, derived from radar scanning in February 2000, from a later model obtained with a stereoscopic sensor in December 2008. They derive a mass balance near zero over an area of 5,600 km2, about one quarter of the ice-covered area in the entire Karakoram. If the mass balance measured by Gardelle and colleagues is representative for all the Karakoram glaciers, ice loss in this region contributed −0.006 mm yr-1 to sea-level change in the past decade — rather than +0.040 mm yr-1, as implied by a previous estimate obtained by extrapolation. Evidently, extrapolation and analogy have failed in this significant region.
With typical scientific understatement, Cogley has revealed a fact about all previous estimates of glacial melting and projections of corresponding sea-level rise—they are based on guesswork. Oh, it's educated guesswork, but guesswork nonetheless. Undoubtedly there is more melting going on than growth world wide, this is a warm period after all. But those who take limited observations of glacial melting and prophesy an imminent watery grave for the world's coastal cities need to take note. Indeed, to fulfill the worst of the doomsayer's projections would require the collapse of the Greenland and Western Antarctic Ice Sheets—something that has probably not happened since MIS 11 over 400,000 years ago (see “Collapse of polar ice sheets during the stage 11 interglacial”).
Map of glacier elevation changes between February 2000 and December 2008.
Contrary to “consensus” climate change wisdom, this remote mountain region where China, India and Pakistan intersect is not losing its glaciers, it is gaining ice mass. Not only is the Karakorum not contributing to sea-level rise, it is responsible for a slight drop in the world's oceans—for now. Did someone say “settled science?”
This is the most unsettling thing about climate change, and nature itself: the “facts” keep changing. Sometimes this is due to science improving and sometimes it is due to nature itself changing. Those who talk about nature, science and climate change in absolutes, those who pretend to know what the future holds, are trying to fool the rest of us, or they are fools themselves.
Be safe, enjoy the interglacial and stay skeptical.