What Himalayan glaciers really do: melting – for last 40 years

Do you remember that flawed Himalayan glacier melting prediction? Here’s what is truly going on in the world’s highest mountain range – and yes, these figures are science-derived.Climate change causes Himalayan glacier melting
The Nepalese laws of physics are quite identical to those in the Swiss Alps, the Russian tundra or on the Antarctic Peninsula. So it should come as no surprise that in Nepal too warming causes some of the ice to melt.

Whether Himalayan glaciers will disappear however depends – beside of course the magnitude of atmospheric warming – on the glaciers’ altitude and on local humidity: the glaciers that are already situated in humid climates prove to be more vulnerable.

Where in the Himalayas were we?

If you want to know about greenhouse gases and climatology the IPCC’s first climate report of 2007 is a must-read, the one by Working Group 1, the senior climatologists of all the world’s leading research institutions.

It is a nearly complete summary of where peer-reviewed climate science brought us, up to a couple of years before the report’s release. That means some of the findings could do with an update [which will come over the course of 2013 and 2014], but it doesn’t mean anything is wrong. In fact, the authors have done a great job in expressing the margins of uncertainty, as for instance with the Earth’s CO2 climate sensitivity.

If you want to know about the social consequences of the physical process of climate change, the IPCC’s second climate report of 2007 was intended for you. It was created by Working Group 2, and these people had a few slippery moments.

‘All Himalayan glaciers gone by 2035’

Although mistakes of WG2 have (by definition) nothing to do with atmospheric science and will never touch the foundation of our knowledge of climate change, they do risk to create a false impression of local climate impacts and, in the case of Himalayan glaciers, ‘water source to over a billion people,’ one with large social relevance.

The biggest flaw of WG2 was citing a non-peer-reviewed and in fact non-scientific source, a 1999 media interview with Indian glaciologist Syed Hasnain to be precise.*

It contained the statement that climate change may cause all [some 15,000 that is(!)] glaciers in the Himalaya to disappear before the year 2035 – somehow an extrapolation of Mr Hasnain’s fieldwork findings, but otherwise plain wrong – or “poorly substantiated estimates of rate of recession and date for the disappearance of Himalayan glaciers. In drafting the paragraph in question, the clear and well-established standards of evidence, required by the IPCC procedures, were not applied properly,” as the UN body describes its own mistake. ‘The procedures will have to be strengthened’ for the new report, the IPCC acknowledges.

[*) The source is not -directly- as is often suggested, a WWF report. This WWF report does quote the same flawed glacier prediction though.]

Setting the record straight

There is a lot of evidence that the effects of climate change in the Himalayas can already be felt, not least because local communities can witness convincing indications, like rock avalanches that are caused by the upslope movement of the permafrost zone, or, as portrayed in BBC’s Human Planet, the onset of spring melting over frozen river passages.

This however does not tell us much about glaciers’ responses. But GPS measurements do. Japanese scientists, from Nagoya University, have equipped three large glaciers in Nepal with the required equipment to measure the speed of the movement and modeled the ice dynamics to get to a three dimensional picture, including melting processes.

Declining trend in all Nepalese regions

They conclude that all three glaciers have been on a declining trend for 4 decades, which morene measurements can easily show, and that for two of them this decline has sped up since the year 2000 [respectively from 0.68 meters per year between 1970 and 1990 to 0.80 m/y from 2000-2010 – and from 0.72 m/y to 0.81 m/y].

These glaciers, Yala in central Nepal and AX010 in eastern Nepal, lie at relatively low altitude and in relatively humid valleys. These are factors that could lead the glaciers to completely disappear, the researchers write in their publication in PNAS, which was released today [and btw edited by James Hansen, of NASA GISS].

Climate feedback mechanisms

The Rikha Samba glacier, in the dryer west of Nepal, offsets 16 percent of the melting trend because climate change leads to an increase of snowfall there. The glacier had been retreating with 0.57 meters per year over 1970-1990. Over the past decade the Rikha Samba glacier has slowed down to a annual retreat of 0.48 meters.

We should not be counting ourselves too blessed with this climate feedback, negative to melting. Firstly because this study shows it may be confined to the arid mountain areas only; secondly because, in case of the studied glacier, the snowfall increase does not translate to larger glaciers, but merely a somewhat lower rate of melting.

But that’s just one theoretical climate feedback – indeed one of many, most of which seem positive feedbacks. The Earth’s general circulation tells us we can’t all have more precipitation. Just as parts of the Himalayas may see an increase in snowfall, climate change may lead to prolongued droughts in Tibet. When in summertime the massive dust storms from the Tibetan Plateau reach the Himalayan glaciers through albedo they’ll be faced with another feedback – one promoting ice melt.

© Rolf Schuttenhelm | www.bitsofscience.org

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