THEGREENGROK    Planetary Watch

Remember Those Himalayan Glaciers?

by Bill Chameides | September 1st, 2011
posted by Erica Rowell (Editor)

Permalink | Comments Off on Remember Those Himalayan Glaciers?

 


AX010 is a glaicer located in Nepal in a humid, low-altitude region of the Himalayas. Data show it has been receding for decades. (Cryosphere Research Laboratory, Nagoya University)

Yes, those glaciers in the Himalayas are still there. But are they coming or going?

Late in 2009 and early 2010, the fate of these glaciers, the largest mass of ice outside of the Antarctic and Greenland, was big news. The latest report of the Intergovernmental Panel on Climate Change (IPCC) stated that:

“Glaciers in the Himalaya are receding faster than in any other part of the world … and, if the present rate continues, the likelihood of them disappearing by the year 2035 and perhaps sooner is very high if the Earth keeps warming at the current rate.”

Putting the IPCC’s Mistakes on These Glaciers Into Perspective

Glaciologists tell us there is no way for a glacier of that size to melt away in a few decades and when the mistake was pointed out and an IPCC official initially dismissed the criticism as “voodoo science,” the whole affair became part of a larger tableau painted by deniers of global warming that much of climate science was … well, bunk.

As it turns out, the IPCC did make a blunder [pdf], but not one nearly as serious as had been made out. The reference to glaciers disappearing in the next few decades was not the IPCC’s consensus finding. By my own count, the assessment discusses the fate of these glaciers in three other places in the four-volume, 3,000-plus page report, all in a much more nuanced, more accurate, and less alarmist context. Here’s an example from the report’s summary for policy makers: “Glacier melt in the Himalayas is projected to increase flooding, and rock avalanches from destabilised slopes, and to affect water resources within the next two to three decades. This will be followed by decreased river flows as the glaciers recede.” (You can read more details about this in this earlier post.)

So, OK, a tempest in a teapot? Maybe. Water under the bridge? Hopefully. But what is going on with the Himalayan glaciers? Are they shrinking, or what? What is their long-term fate?

A paper appearing last week in the Proceedings of the National Academy of Sciences by Koji Fujita and Takayuki Nuimura of Nagoya University in Japan attempts to answer these questions. The authors report on data gathered from 2008 to 2010 using global positioning systems from three so-called “benchmark glaciers” in the Himalayas. These data, combined with survey data collected from the 1970s through the ‘90s for the same glaciers, made it possible for them to assess what has been happening of late and how that compares to what was happening in the later part of the 20th century.

AX010 in 1978 (Cryosphere Research Laboratory, Nagoya University)

AX010 in 1989 (Cryosphere Research Laboratory, Nagoya University)

AX010 in 1989 (Cryosphere Research Laboratory, Nagoya University)

AX010 in 2004 (Cryosphere Research Laboratory, Nagoya University)

AX010 in 2008 (Cryosphere Research Laboratory, Nagoya University)

The Glaciers Are Receding … Heterogeneously

The authors found that all three glaciers are currently receding — they call it “wastage.” But as indicated in the title of their paper — “Spatially Heterogeneous Wastage of Himalayan Glaciers” — the receding was “heterogeneous.”

The benchmark Nepalese glaciers studied fall into two broad categories related to elevation and humidity: the Rikha Samba is located at a higher elevation in an arid region; the other two, Yala and AX010, are located at lower elevations in a more humid location. The authors point out that glaciers located in humid locations tend to be more sensitive to rising temperatures than those in arid areas because they “can exist at lower altitudes due to the large amount of snow accumulation, making them more sensitive to warming via changes in the fraction of precipitation occurring as rainfall (which affects accumulation).”

And in keeping with that notion, the humid glaciers are behaving differently from the arid one. Over the past decade, the wastage of both humid glaciers has accelerated (compared to the previous two decades) while the wastage rate of the arid glacier has slowed.

The ‘Equilibrium Line’ Portends Good and Bad

Fujita et al were also able to make projections about the long-term fate of the three glaciers based on the position of each glacier’s equilibrium line: the altitude where accumulation equals melting. Above this altitude, snow accumulation dominates and the glacier accumulates mass. Below it, melting dominates and the glacier loses mass. So for example when a glacier’s elevation falls below the equilibrium-line altitude, it loses its ability to add mass and “is destined to disappear over time.” The authors’ calculations suggest that the altitude of the humid glaciers is falling and approaching a point when the entire glacier will be below its equilibrium-line altitude. When that happens, these glaciers’ fate will be sealed.

However, not so for the arid glacier. The authors predict that it will continue to shrink for a time but “will approach an alternative equilibrium and will be maintained.”

But before the friends of the arid Himalayan glaciers break out the champagne and celebrate, it should be noted that there is a pretty significant caveat to this conclusion — the conclusion applies “if the present climate persists.” A pretty big if, as there are lots of climate model predictions that project very different (i.e., warmer) conditions in the coming decades.

IPCC Critique

Fujita et al come down hard on the IPCC and those who have predicted doom for the Himalayan glaciers:

“The disappearance of Himalayan glaciers was not only overstated in the Intergovernmental Panel on Climate Change report, but also asserted in a study based on analyses of a Himalayan ice core. Disappearance may be the fate of some glaciers located at lower altitudes, as indicated by the present results; however, the heterogeneous distribution of the [equilibrium line altitude] ELA trend suggests that it is
unwarranted to draw conclusions regarding the fate of all Himalayan glaciers based on a small number of examples, especially when the benchmark glaciers are chosen in part for their small size, small elevation range, and simple geometry.”

I can’t argue with that logic and these are important points to bear in mind as we go forward. I simply note that it is equally unwarranted to draw conclusions regarding the fate of the Himalayas based on assumptions that the present climate will “persist.”

Further Reading

More Photos

Nagoya University’s Cryosphere Research Laboratory site

filed under: climate change, faculty, global warming, Planetary Watch
and: , , , , , , , , , , , , , ,

comments disabled after 30 Days

©2015 Nicholas School of the Environment at Duke University | Box 90328 | Durham, NC 27708
how to contact us > | login to the site > | site disclaimers >

footer nav stuff