One of the claims put forth by climate change alarmists is that Earth's glaciers are rapidly melting. This supposedly causes all sorts of problems, from rising sea levels to failing water supplies. A recent report in the journal Nature uses NASA's Gravity Recovery and Climate Experiment (GRACE) satellite to measure the loss of glacial ice around the globe. Analysis of the satellite data on Earth's changing gravity field delivers some unexpected results and the results have surprising implications for both the global contribution of glaciers to sea level and the changes occurring in the mountain regions of Asia.
The story of melting glaciers has been told ad nauseam by climate catastrophists and the scientifically gullible news media for years. This blog has reported on the purported “rapid melting” of the Himalayan glaciers several times before (see “Himalayan Glaciers Not Melting
” and “Himalayan Glacier Disappearance Overstated
”). It is true that glaciers melt, they are the primary source of water in a number of regions around the world.
As I have often stated, this is an interglacial period, ice is supposed to melt. Otherwise there would still be a mile of ice on top of New York City. But despite evidence to the contrary, warmists continue to claim that glaciers are disappearing at an alarming rate. According to an accompanying News & Views article
appearing in the same issue by Jonathan Bamber, from the Bristol Glaciology Centre:
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Glaciers and ice caps are pivotal features of both water resources and tourism. They are also a significant contributor to sea-level rise. About 1.4 billion people are dependent on the rivers that flow from the Tibetan plateau and Himalayas1. Yet significant controversy and uncertainty surround the recent past and future behaviour of glaciers in this region. This is not so surprising when one considers the problem in hand. There are more than 160,000 glaciers and ice caps worldwide. Fewer than 120 (0.075%) have had their mass balance (the sum of the annual mass gains and losses of the glacier or ice cap) directly measured, and for only 37 of these are there records extending beyond 30 years. Extrapolating this tiny sample of observations to all glaciers and ice caps is a challenging task that inevitably leads to large uncertainties.
It is certainly no exaggeration that previous estimates of glacial melting have been fraught with error, sparking contentious debate among glaciologists. “Discussion of the demise of the Himalayan glaciers has been mired in controversy, partly because of basic errors, but also because of the dearth of reliable data on past trends,” Bamber explains. Indeed, estimates for the Himalayan glaciers, based on a few easy to access sites, was roundly criticized by experts world wide. Now comes a “surprising” new set of estimates, based on satellite measurements of glacier ice mass.
Most previous global mass balance estimates for Glaciers and ice caps (GICs) rely on extrapolation of sparse mass balance measurements, which represent only a small fraction of the GIC area. Based on a global, simultaneous inversion of monthly GRACE-derived satellite gravity fields, Thomas Jacob et al, calculated the mass change over all ice-covered regions greater in area than 100 km2. In “Recent contributions of glaciers and ice caps to sea level rise
,” the authors describe their work:
Here we present a GRACE solution that details individual mass balance results for every region of Earth with large ice-covered areas. The main focus of this paper is on GICs, excluding Antarctic and Greenland PGICs. For completeness, however, we also include results for the Antarctic and Greenland ice sheets with their PGICs. GRACE does not have the resolution to separate the Greenland and Antarctic ice sheets from their PGICs. All results are computed for the same 8-yr time period (2003–2010).
Here the term PGICs means peripheral GICs—in other words, surrounding non-glacial ice such as floating sea ice. To determine losses of individual GIC regions, they covered each region with one or more ‘mascons’ (small, arbitrarily defined regions of Earth). The mass of each mascon was then estimated using the GRACE data. They were particlulary interested in measuring the glaciers of the Himalaya, refered to here as High Mountain Asia (HMA). The mascons are shown in the figure below.
Mascons for the ice-covered regions used in the study
“Our results for HMA disagree significantly with previous studies,” the article plainly states. Even though previous GRACE based studies showed significant mass loss, the authors state that those measurements were in error—the outcome of “leakage” of readings from surrounding plains that was included by the Gaussian smoothing functions used. The excessive readings from the plains have been attributed to groundwater movement, not ice loss. They also dismiss any contribution from broad-scale tectonic uplift. In short, they found minimal ice loss from the glaciers of the Himalaya.
According to the report: “The GIC rate for 2003–2010 is about 30 per cent smaller than the previous mass balance estimate that most closely matches our study period. The high mountains of Asia, in particular, show a mass loss of only 4 ± 20 Gt yr−1 for 2003–2010, compared with 47–55 Gt yr−1 in previously published estimates.” Bamber summarizes the article's findings this way:
First, the contribution of GICs (excluding the Antarctica and Greenland peripheral GICs) to sea-level rise was less than half the value of the most recent, comprehensive estimate obtained from extrapolation of in situ measurements for 2001–05 (0.41 ± 0.08 compared with 1.1 mm yr−1). Second, losses for the High Mountain Asia region — comprising the Himalayas, Karakoram, Tianshan, Pamirs and Tibet — were insignificant. Here, the mass-loss rate was just 4 ± 20 gigatonnes per year (corresponding to 0.01 mm yr−1 of sea-level rise), compared with previous estimates that were well over ten times larger. By a careful analysis, the authors discounted a possible tectonic origin for the huge discrepancy, and it seems that this region is more stable than previously believed.
The facts are in and the latest measurements clearly state that the Himalayan Glaciers are not melting at an abnormal rate. In fact, another new study, this time in Nature Geoscience, reports that annual groundwater fluxes for Nepal are larger in volume than the contribution from ice- and snowmelt. In “Impact of transient groundwater storage on the discharge of Himalayan rivers,” Christoff Andermann et al. report that a significant portion—perhaps as high as 50 percent—of the water discharged from the high mountains of Asia does not come from melting glaciers.
Runoff from the Himalaya is not all from glacier meltwater
Scientists have done what they are supposed to do: conduct new experiments, make new measurements and devise better answers. Using the latest technology to broaden their observations new data shows the old estimates of sea-level rise due to glacial melting are off by 50%. The bungled estimates for melting in the Himalaya are exposed as total fabrications. Science works, but there is no easy defense against lazy or biased scientists who produce “facts” that support a political agenda. That is why it is best to remain skeptical of claims of impending disaster backed by weak minded consensus arguments.
Hopefully this new evidence will put and end to the exaggerated claims of glacial melting from those who want to prove that the world around us is afflicted by the evil works of man. The alarmists' previous estimates were “well over ten times larger” for some areas according to these experts. It would appear that, when it comes to climate science, if you are going to tell a lie, you should tell a big lie. That ensures you make the evening news. Do not, however, look to the news media for a correction—disasters sell, good news does not.
Be safe, enjoy the interglacial and stay skeptical.