Friday, April 20, 2012

Good science on Himalayan glaciers


In the aftermath of Glaciergate, this week's issue of the journal Science includes a sober and informative review article by a large team of researchers lead by Tobias Bolch of the University of Zurich on the state and fate of Himalayan glaciers. Unfortunately, the paper is pay-walled. I think this is a another  nice example of an article that should be unlocked to show that technical and objective, and at the same time accessible and also quite relevant, information in climate research is still possible. 


The article contains a wealth of information about the evolution of Himalayan glaciers since the mid 19th century and estimations of their possible fate in the future. I will only highlight the points that called my attention, although probably there are many others that may be more important for glaciologist. The article makes quite clear that not all Himalayan glaciers behave in a similar manner: the Karakoram seems to be somewhat special and decoupled from the general evolution of the rest of Himalayan glaciers. A bit surprising is that the Karakoram glaciers are currently gaining mass, whereas for the rest of glaciers the mass balance is negative. This underlines the complex response of glaciers to climate forcing. It is well known that the mass balance of some glaciers are more strongly driven by precipitation than by temperature. During the Little Ice Age , for instance, some Norwegian glaciers gained mass, whereas other glaciers from surrounding regions lost mass, probably reflecting a shift in the weather patterns that brought moisture to those glaciers.

With a longer term perspective, most Himalayan glaciers have been loosing mass since the mid 19th century, but there are exceptions to this general tendency. Again, the Karakoram arises as a special region. The glaciers here apparently show a quite heterogeneous behaviour but in general they have been quite stable or slightly increasing also on this long time scales. Another exception for all Himalayan glaciers is that this long-term tendency towards mass loss was interrupted during 1920-1940 where ' about half other records show stationary or advancing tongues'. I was quite surprised to read this sentence here, since as it is well know, those 3 decades were characterized by strongly rising global mean temperature that culminated around 1940. Maybe the in-situ temperature evolution during 1920-1940 was different from the global mean - I guess that the local records from this region are not very trustworthy also considering its complex topography. Nevertheless, it reminded me that the relationship between global mean temperature and glacier melt and this also to global sea-level, can be far more complex that one may think.

Another interesting result is that the mass loss of the Himalayan glaciers except Karakoram started already in the mid 19th century. The figures provided in the article do not allow to discern a clear acceleration in the mass loss in the recent decades. There are some hints that the mass loss is now a bit higher than at the turn of the 20th century, but it does not look very dramatic. The renowned expert in world glaciers, Johannes Oerlemans, who also authored a reconstruction of the Northern Hemisphere mean temperature based on historical glacier records, has indicated in several talks I have witnessed that glacier retreat started before anthropogenic greenhouse gas forcing could have been important. 
 
Now to the sentence you all are probably awaiting :
The statement that most H-K [ Himalaya-Karakoram ] glaciers will likely disappear by 2035 is wrong (8), as shown by simple but physically robust modeling (50). More realistic projections (5), relying on degree-day modeling but reporting the H-K glaciers only as part of High Mountain Asia, are consistent with the simpler model in suggesting moderate mass loss over the 21st century

Yes, the IPCC TAR AR4 was wrong regarding the Himalayan glaciers and apparently it was easy to show that it was wrong. All in all, in my view this was an important error in the Third Fourth IPCC Report. Theoretically, the governments of the countries surrounding the Himalayas would have been severely affected by a disappearance of Himalayan glaciers as soon as 2035, so that they should have immediately started to design a contingency plans. Well, nobody did anything of that sort, probably because they actually did not believe those IPCC projections anyway. This error in the Third Fourth IPCC report tells more about the real influence (credibility among policy makers?) of the IPCC than about the science itself.

This being said, the paper continues:
Nevertheless, all models project mass losses in coming decades that are substantial for most parts of the Himalayas, but consistently fall well short of complete region- wide glacier disappearance even by 2100

This result sounds logical. With increasing temperatures, glaciers in general will tend to shrink. However, given the demonstrated complex behaviour of these glaciers, I would have liked to see a glacier simulation over the 20th century, preferably driven by a regional climate model, that could explain why the Karakoram glaciers are special. 

12 comments:

ghost said...

My problem with your post is: the AR4 IPCC report contains the Karakorum glaciers. It writes:

...several high glaciers in the central Karakoram are reported to have advanced and/or thickened at their tongues (Hewitt, 2005), probably due to enhanced precipitation.

http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch4s4-5-3.html


So, I would say, the AR4 report was quite right about the Karakorum glaciers. The problem was the WG II(?) report that was in error. Of course, one error makes the complete report wrong...

eduardo said...

Ghost,

yes, you are completely right that the error was in the WG2 report. And no, one error does not make the entire report wrong.

But your comment shows that the WG2 error is even more incomprehensible for outsiders. Had the WG2 authors looked into the WG1 report..

In reality, the IPCC authors are writing under quite a strong time pressure, so I can perfectly imagine that WG2 and WG1 did not communicate at all. Hopefully, this will change in the next reports, although another time frame would be more beneficial, in which for instance the publications of the partial reports WGx is staggered in time

Mathis Hampel said...

http://www.thetopograph.blogspot.co.uk/2012/02/contested-knowledge-in-contested_27.html

Martin Mahony offers an interesting perspective on Indian glaciology, IPCC and 'himalaya-gate'.

MostlyHarmless said...

"With a longer term perspective, most Himalayan glaciers have been loosing mass since the mid 19th century, but there are exceptions to this general tendency."

No one knows that. Currently just over 400 of the 160,000 glaciers worldwide are being monitored in sufficient detail to even estimate mass balance, let alone calculate a fairly accurate figure. That monitored proportion is about 0.25% of the total.

Researchers are not, in general, interested in glaciers that are static or gaining mass, they don't make headlines. Studying only retreating glaciers, and extrapolating to the local population is akin to studying patients in hospital, and extrapolating those results to the local population.

ghost said:

"...several high glaciers in the central Karakoram are reported to have advanced and/or thickened at their tongues (Hewitt, 2005), probably due to enhanced precipitation."

I've read a fair number of papers and publications on glaciers, and that's the first time I've seen quoted that some accumulate mass at the tongue (the lower end). It defies logic and reason.

Günter Heß said...

For me the most disturbing thing is not the error itself, but how it gets circulated even by scientists without checking.
This means we cannot and should not trust those reports.
Especially it shows that the summary for policy makers cannot be trusted.

Best regards
Günter Heß

Reiner Grundmann said...

Eduardo #2

referring to the authoritative WP1 is an interesting move but begs the question. It would solve the problem if WP1 had established some kind of reliable knowledge source which is an input for WP2. But in reality the structure and process of the IPCC is not designed in such a way. There is no linear throughput but three different assessment processes with different focus.

Werner Krauss said...

Dear Günther Heß,

I had to think about your statement "This means we cannnot and should not trust those reports". As you might remember, each time someone uses "We" out of nothing, my alarm bells ring.

I am sure, that YOU as an educated person normally don't trust reports or assessments without checking facts, comparing to other studies, putting it into context, asking critical questions etc. That's what everybody politician does, for example - every interested reader except those imaginary "we" (of which you, I bet, are not really part of).

"Trust" in the sense of "blind trust" is not something you can invest in a report like this one. You know that for sure, as everybody else should. It's only the best study of this size you can get about global climate, and considering the circumstances of its production, there are amazingly few errors of this size in it.

"We cannot trust" is a populist argument which is not based on any realistic assumption; it just pretends there were one in stating that "science speaks truth" - which is good for Hollywood fairy tale movies, but not a good guideline for real life. The IPCC is not the holy scripture, it's a fallible product of 21st century science.

As Eduardo's contribution shows, science about glaciers goes on, and the error will become history. That's how it goes. The process how to deal with (unavoidable) errors in public is another contested question, of course.

There should be better arguments in case you want to challenge the overall direction of the IPCC (which, of course, exists - but it is also in permanent change, as the new SREX shows).

hvw said...

MostlyHarmless,

"Researchers are not, in general, interested in glaciers that are static or gaining mass, they don't make headlines."

In case you feel that maybe your idea about researchers' motivations could use some calibration, I recommend you look into the vita of Ken Hewitt; you quote a reference to him below. When you are familiar with the track of choices of research subjects of this great geographer, you will stay away from such gunshot offenses at whole professions. I promise.

Doing that you will easily pick up enough glaciology 101 to understand how glaciers can get thicker in the ablation zone. In the reference mentioned there is even a photograph showing marks of lateral moraines that document just that happening.

Werner Krauss said...

@hvw and others:

Interesting to see how "the scientist" or "science" shifts shape and role throughout this thread, depending on context and argument.

eduardo said...

@6
Reiner,

yes, I agree with you. I fin the present structure and size of the IPCC reports not quite optimal. Other structures, e.g. time lags between WGs, would certainly contribute to avoid such errors. It would also allow that e.g. WG1 authors can review drafts of WG2 before their are published, which is not nor quite possible

Anonymous said...

@ Eduardo

What about the time lags scheduled here (http://ipcc.ch/activities/key_dates_AR5_schedulepdf.pdf) for AR5?

Andreas

eduardo said...

Andreas,

in my opinion a few months lag is not really significant. For instance, the new climate long term projections comprise 20 or so models , 3 scenarios. This is a huge data set that requires certainly much longer than 3 months to be analysed in terms of the climate change impacts. In my view, a reasonable lag would be 2 years. I think the quality of the report would gain