Guest commentary by Mauri Pelto
For global temperature time series we have GISTEMP, NCDC and HadCRUT. Each has worked hard to assimilate global temperature data into reliable and accurate indices of global temperature. The equivalent for alpine glaciers is the World Glacier Monitoring Service’s (WGMS) record of mass balance and terminus behavior. Beginning in 1986, WGMS began to maintain and publish the collection of information on ongoing glacier changes that had begun in 1960 with the Permanent Service on Fluctuations of glaciers. This program in the last 10 years has striven to acquire, publish and verify glacier terminus and mass balance measurement data from alpine glaciers the world over on a timely basis. Spearheaded by Wlfried Haeberli with assistance from Isabelle Roer, Michael Zemp, Martin Hoelzle, at the University of Zurich, their efforts have resulted in the recent publication, “Global Glacier Changes: facts and figures” published jointly with UNEP. This publication summarizes the information collected and submitted by the national correspondents of WGMS portraying the global response of glaciers to climate change, as well as the regional response.
The health of an alpine glacier is typically determined by monitoring the behavior of the terminus and/or its mass balance. Glacier mass balance is the difference between accumulation and ablation (melting and sublimation) and can be altered by climate change caused variations in temperature and snowfall. A glacier with a sustained negative balance is out of equilibrium and will retreat. A glacier with sustained positive balance is out of equilibrium, and will advance to reestablish equilibrium. Glacier advance increases the area of a glacier at lower elevations where ablation is highest, offsetting the increase in accumulation. Glacier retreat results in the loss of the low-elevation region of the glacier. Since higher elevations are cooler, the disappearance of the lowest portion of the glacier reduces total ablation, increasing mass balance and potentially reestablishing equilibrium. If a glacier lacks a consistent accumulation it is in disequilibrium (non-steady state) with climate and will retreat away without a climate change toward cooler wetter conditions (Pelto, 2006; Paul
et al., 2007).
In terms of mass balance two charts indicate the mean annual balance of the WGMS reporting glaciers and the mean cumulative balance of reporting glaciers with more than 30-years of record and of all reporting glaciers. The trends demonstrates why alpine glaciers are currently retreating, mass balances have been significantly and consistently negative. Mass balance is reported in water equivalent thickness changes. A loss of 0.9 m of water equivalent is the same as the loss of 1.0 m of glacier thickness, since ice is less dense than water. The cumulative loss of the last 30 years is the equivalent of cutting a thick slice off of the average glacier. The trend is remarkably consistent from region to region. The figure on the right is the annual glacier mass balance index from the WGMS (if this was business it would be bankrupt by now). The cumulative mass balance index, based on 30 glaciers with 30 years of record and for all glaciers is not appreciably different (the dashed line for subset of 30 reference glaciers, is because not all 30 glaciers have submitted final data for the last few years):
Nor is the graph much different for North America Glaciers individually or collectively. The next figure shows the cumulative annual balance of North American Glaciers reporting to the WGMS with at least 15 years of recor:
The second parameter reported by WGMS is terminus behavior. The values are generally for glaciers examined annually (many additional glaciers are examined periodically). The population has an over-emphasis on glaciers from the European Alps, but the overall global and regional records are very similar, with the exception of New Zealand. The number of advancing versus retreating glaciers in the diagram below from the WGMS shows a 2005 minimum in the percentage of advancing glaciers in Europe, Asia and North America and Europe. In Asia and Alaska, there have been extensive terminus surveys illustrating long term retreat using satellite image and aerial photographic comparison over longer time spans. Those results indicate that 95% of the glaciers are retreating, but are not fully reflected in the annual terminus retreat data base of the WGMS. In 2005 there were 442 glaciers examined, 26 advancing, 18 stationary and 398 retreating – implying that “only” 90% are retreating. In 2005, for the first time ever, no observed Swiss glaciers advanced. Of the 26 advancing glaciers, 15 were in New Zealand. Overall there has been a substantial volume loss of 11% of New Zealand glaciers from 1975-2005 Salinger et al. ,but the number of advancing glacier is still significant.
That glaciers are shrinking in terms of volume (mass balance) and length (terminus behavior) is not news. What is news is the development of a robust global index of glacier behavior. As a submitter of data to WGMS, I can report that the scrutiny and level of detail requested of the submitted of data is increasing. The degree of participation by glaciologic programs is also increasing. Both are important and will lead to an even better glacier index in the future, with more even representation from around the globe.
I am not a professional climatologist. I speak as a physiologist. It is inconceivable that nearly 8 billion large mammals, many of whom are driving automobiles which, while in motion, are producing CO2 at a rate 2000 times that of the driver do not have a profound effect on the health of planet earth. I believe that the Age of Technology will be the final Age for civilization as we know it. I agree with Martin Rees, President of the Royal Society, that the 21st will be Our Final Century and I do not believe there is anything that we can do about it.
Gavin,
Just a ‘heads up’…Isn’t the study called “Global Glacier Changes: facts and figures”, not “Global Glacier Changes: fact and fiction”?
[Response: Indeed! – gavin]
Thanks for this Dr. Pelto, great post.
> final age for civilization as we know it
Each age so far ended civilization, as they knew it. None were scientific cultures. Parts of ours are scientific. Some will grow from that. Our job’s not to allow waste and ruin of what we control.
Too bad about the glaciers; glad people are doing the science while the ice is available and leaving an archive for those who may use it.
Unfortuantely, all the people at Wattsupwithmehead? and other beautiful places on the web, will see is this:
“As a submitter of data to WGMS, I can report that the scrutiny and level of detail requested of the submitted of data is increasing.”
and their response will be thus:
“See! The data is incomplete! It’s flawed! It’s not good enough! You said so RIGHT THERE! You must be filling in data! You’re not including every single glacier on the planet, and you left of the 5,000 growing glaciers Uncle Joe documented using Google Earth!”
Hovey Rollin, reCaptcha, 2009
Thanks Mauri, great material.
Might you add some expert comments about the reasons why New Zealand seems to be somewhat of an exception? It would be nice to have a few more words on that in this thread.
The glaciers appear to be impressive integrators of climate trends. Any explanations for what looks like an acceleration of the rate of loss since the beginning of the new century?
Mauri, can you comment on how this set of data is characterized to decide how long a time span is needed to say there is a trend, statistically? I know each set of data has to be looked at, and not to assume it’s the same as other charts that look the same.
Something like Atmoz and Stoat did would help. Their work is mentioned more often these days by the denial crowd, oddly:
http://www.google.com/search?q=atmoz+stoat+“five+year+trend”
Not a glacier expert! but resident in NZ. Unless I am very much mistaken the advancing glaciers are all on the western side of the Southern Alps facing the prevalent wind. I would suggest that the warming Tasman sea is resulting in higher snowfall in neve regions which is outpacing warming in deeply shaded terminus areas. However, precipitation would have to increase at very high rates to keep pace with warming so this trend will reverse. The ice loss and retreat in the eastern glaciers is spectacular.
For those interested in the NZ glaciers, I blogged the latest figures (2.5km3 volume loss April 2007-March 2008) here. Also includes link to download recent NIWA article on our ice.
Short summary: NZ’s glaciers are in the Southern Alps – the spine of the South Island. The west of the divide receives massive rainfall from the prevailing westerlies, the east is much drier. West Coast glaciers are short, and have rapid responses to changes in precipitation in their nevées, those on the east are in longer valleys, and have much longer response times. The eastern glaciers are all (IIRC) in decline, with proglacial lakes ensuring continuing retreat, but the West Coast glaciers have cycles of retreat and advance, depending on changes in precipitation.
One of the more robust projections for our part of the world is for an intensification of the westerlies during warming. More precipitation, more ice in the West – at least while rain still falls as snow. However NIWA’s RCM suggests that the Alps could be the fastest warming regions of NZ, so that might change sooner than we expect…
Based on GISP2/Ice record (and my understanding of how H2O2 melts along with H2O). Draw a line across all the highest values, and a line across the lowest values. This will create a band representing the extent of freeze-melt cycles.
The most recent times has seen the largest melting since about 150 years ago. There’s a tightening of the freeze-melt band about 150 years ago. Potentially representing a period of high freeze during one of the “little ice age” periods. The band tightens (“bottle necks”) around 250 years ago again , and then again at ~ 400 years ago (again probably representing the coldest periods of the little ice age). The H2O2 concentrations overall have been going up since the end of the YD cooling.
Thanks as always!
“…if this was business it would be bankrupt by now.”
Wow. I wish it were a Business! You know, Big Oil, Gas, Coals!
Keep up the evidence flow, Friends! We’ll keep blogging, chatting with people who don’t like riding Buses or Light Rail Trains, who still drive non-Hybrid SUVs’, and generally driving the facts o’ life home to our more childish compatriots!
P.S.: You often forget to inculde the key to many of your charts and graphs; and though we Real Climate fans are not, I assume, dummies – and can thus figure them out anyway; to some it may not have been so obvious as to how to correctly read that Graph about the retreating and advancing Glaciers. They could also be larger; though I was able to use my screen enlarging feature to read the finer print/scales/etc..
An additional response, inspired by Pysiologist Dr. John A. Davisons’ bleak forecast in Item #1.
I too, am not a Professional Climatologist; but a disabled ‘lay-polymath’ with a lot of time on my hands, a knack for writing, a good and rather broad knowledge of all the sciences in general (I began reading Scietific American in 1976, at Age 11; and I remember Jim Hansens’ alarming reports, well!), and a much less bleak – even hopeful – point of view; as I think that I can Help – if I can assemble the right Audience, and get them to listen.
To this end, I’m working on some Essays entitled ‘Petri Dish Earth’, ‘Bringing Heaven Down To Earth’, and The Great Patriotic War on Industrializing The Moon, and Extracting Resources from throughout The Solar System’.
Get the Idea? We are a Colonial Organism – and SMART Colonial Organisms send out Tubules (sp) in search of new sources of Food AND places to poop!
OURS should go STRAIGHT UP!
There are many Points that I’ve never seen anyone make before in my essays – especially in terms of how I stress that the ecomonies of scale, and the TRUE Multi-Quadrillion Dollar cost of NOT doing anything about Sea Level Rise, etc., make doing this a Really Good Idea! With help, I can cause our ‘Dear Leaders’ to undergo a Major Paradygm Shift!
I hope that, when I’m done with them, you’ll all read them; I’ll let you know when and how, as I intend to post them everywhere – as well as to send them to my Friends at the We Campaign, etc..
James Staples, N.B.W.T.M.S.T. (Not Been Watching Too Much Star Trek!)
I concur with #9 and #10 in the 1990’s a similar pattern was apparent in Norway, with the more martitime glaciers experiencing positive balances due to increased winter precipitation overcoming increased temperatures and ablation, note Alfotbreen and Nigardsbreen. Glaciers that were more continental like Grasubreen and Hellstugubreen continued a negative balance pattern. In NZ the eastern draining glaciers are the larger glaciers and their volume losses greater overall. Regarding #7 given that the trend is spatially consistent and annual precipitation changes are not spatially consistent, it must be temperature changes that are driving the negative balances. Of the 11 glacier I measure and report to WGMS the two changes are: 1)A reduction in the winter snowpack/precipitation ratio. We are seeing more winter rain/melt events. 2) Increased summer ablation. #8 Great question Hank I will get back to this more later.
James Staples,
Good show. Let me know when your essays appear. You can find mine at my weblog – jadavison.wordpress.com where everyone is always welcome. Incidentally, I hate being right.
I will be interested in other responses to the significance of the trends. I note three patterns that argue for the significance of the trends
1) The similarity from glacier to glacier in North America or the Alps for example. 2)The consistency of the negative trendlines as Atmoz would say it does not matter whether it is a 5, 10 or 15 year trendline you apply to the global mass balance time series, they are all negative for the 1980-2005 period. 3) That every one of the last 17 years has had a negative balance. We are not comparing the mass balance to some average for a period, this is a physical determination of glacier volume loss each year. We cannot have every year be negative in global glacier balances can we? The trend is steeper with the worst years being 2003 and 2005. The latter maybe what 1998 was for atmospheric temperatures, a hard year to surpass in a negative sense and has in the short run probably exaggerated the trend. Now that is a glaciologists answer, what about a statisticians?
Re: #17 (Mauri Pelto)
To evaluate statistical significance I need numbers, not graphs. I did find quite a bit of data in Glacier Mass Balance and Regime: Data of Measurements and Analysis (Mark Dyurgerov), as well as a supplement to those data which go to 2003 in many areas and 2004 for a few. Alas, that excludes 2005 which you describe as being most interesting.
I’ll almost certainly post about it when I’ve had time to digest the data.
In the meantime I can tell you this: the very first graph in this post shows negative mass balance for the last 17 years. That’s no accident.
Are these significant amounts?
Does the reduction add up to a 0.1% decline? Is it less than 0.1%? Or is there a relative total mass balance unit to compare to so we have some perspective?
IIRC, in southwestern Colorado a roughly one month advancement of seasonal melt dates for mountain snowfields has ben attributed to increased deposition of aeolian dust. So at least in this case, land use changes in the high desert areas upwind may contribute significantly to early snowmelt. In this cae, the region contains no glaciers, and so it wouldn’t contribute to these datasets.
Conversely, in the front range of Colorado, mass balance on the neoglacial ice bodies has supposedly been attributed to an increase in summer cloudcover, which itself has been attributed to anthropogenic aerosols (smog) from the nearby population areas.
Of course I am not a climatologist, or glaciologist, so it is possible these anecdotal reports have been discredited without me being aware of it. I just wanted to make a point, that aside from temperature, and precipitaion, glacier mass balance may be affected by dust/soot deposition, as well as melt season cloud cover changes.
Interesting data, but the question “Has it hapened before” comes to mind, especially in light of this article http://news.bbc.co.uk/1/hi/sci/tech/7580294.stm
“The Roman coins found on the Schnidejoch are being seen as proof that the Romans used this route to cross the Alps from Italy to their territories in northern Europe. Interestingly, one of the Earth’s chillier periods coincides with the decline of the Roman empire”
This article is very interesting too.
http://archiv.ethlife.ethz.ch/e/articles/sciencelife/gruenealpen.html
“”Between 1900 and 2300 years ago the lower tips of the glaciers lay at least 300 metres higher than today. ”
http://archiv.ethlife.ethz.ch/images/al04_126-l.jpg
It would be useful, if the diagrams in this article could be opened out into seperate windows, the one with the red/blue bar charts next to the text starting “The second parameter reported by WGMS is terminus behavior” has completely illegible wording.
Thanks for the info on NZ Gareth. I note that Salinger also advises that the total ice volume for NZ in 2005 was about 48km3, so with rates like minus 2.5km3 per year we haven’t too long to go before there’s very little ice mass remaining below the snow line. Better take the grandkids for a trip before its gone eh!
Tamino I would welcome your perspective on this. Let me direct your attention to some particular data later today or tomorrow. In terms of significance it depends on the mean thickness of the glacier involved. Most of the glaciers observed are smaller temperate alpine glaciers with mean thicknesses of between 50 and 100 m. The collective loss for the ten glaciers I report from the North Cascades of 12 m of mass balance loss and an average starting thickness in 1984 of 50 m, it is a approximately a 25% loss in volume in 25 years. For the reported mean loss of the global glacier set of 12 m since 1980, this represents a volume loss of no less than 12%, but more likely 15-20%. The volume loss can be assessed by remapping of glacier surface elevation without the annual mass balance signal, and has been done in the Swiss Alps Paul et. al (2003, 2004, 2007) North Cascades (Pelto, 2006) and other settings and has supported the WGMS values of volume loss from cumulative mass balance.
Re #21. Wouldn’t Romans have preferred to keep the Northerners out? It wasn’t until Marcus Aurelius that some semblence of peace was established. The Roman civilization declined because of political outfalls: Eastern & Western empires etc. well into the 300-400 A.D.
Re: #23 (Mauri Pelto)
I look forward to new data (I always do!). No big hurry; it’s super-bowl-sunday so I’m not doing much else today.
The graphics could be improved. However, that would defeat part of the purpose, which is to get you to go to the source of the primary graphics, the “Global Glacier Changes: facts and figures” report. The paper by Kaser et. a., (2006) provides another detailed statistical look at the the trends both regional and global of glacier mass balance. Notice that the largest mass balance losses in this paper are for ranges with larger glaciers Alaska and Patagonia. http://www.trentu.ca/academic/geography/glaciology/2006GL027511.pdf
Nigel,
I took two trips to the NZ glaciers (both sides of the divide) last summer. There’s a pic of the Tasman glacier lake at the bottom of this post from last April, plus a news report about the fate of the glacier.
They’re well worth a visit now, whatever their eventual fate…
“I am not a professional climatologist. I speak as a physiologist.It is inconceivable that….”
I sense that you are probably an urban dweller and assume you have never lived outside a city.
Men who live in cities think that all life is in cities. The act of turning a switch changes the environment in your house and by extension in your mind, the city.
I would ask you to spend a year at sea in a boat, out of sight of land, to regain your perspective.
You say “It is inconceivable that..”
There are many things which are inconceivable to my hamster but which are natural. He has yet to ride along a river and down a waterfall. Natural things but inconceivable to him. I will not mention the washing machine.
I think the debate would benefit from logic rather that emotive statements such as “It is inconceivable that..” which really mean “I do not understand how..”.
Nic Londsdale
I take it you regard it as perfectly “natural” that there might be a monoculture of nearly 8 billion large mammals whose entire culture has depended on the production of several poisonous gases? That is a question. Of course you don’t have to answer.
I have never lived in large cities and I have spent many hours close to nature both outdoors and in the laboratory studying my fellow creatures. I have no idea what you have been doing with your life and wouldn’t dream of presuming anything about you as you have about me. Thank you for reprinting my comment.
Nic,
I’ve lived in very isolated conditions in the Canadian arctic and spent time in the West Australian desert – both of which are bloody empty as land goes.
Is that enough perspective for me to say that your arrogant dismissal of city-dwellers is some hot-air that this debate would be better off without? Because it’s inconceivable to me too that we could have changed the earth this much without that affecting the health of planet earth. Just how much of the world we’ve messed with – it’s hard to look down at any part of Europe or the continental USA from a jet and *not* see evidence of man.
re Bill DeMott 31 January 2009 at 2:10 PM on the accelerating shape of the loss curve.
It’s simple math; if the input to an integrator is a step change, the output is a linear ramp, whose slope is proportional to the size of the step. If the input is a ramp (global temperatures, increasing over time), the output is a ramp which increases slope with time. However, to me it looks like the negative slope is actually becoming less steep after ~2002 (positive second derivative). Eyeballing curves can be misleading – I’d like the raw data to look at to be sure. This may be correlated with the short term trend to slowing of global warming in the last few years. It will be interesting to see what happens as the ENSO flips in the coming years.
While preparing a “There I was” illustrated talk about our recent ascent of Kilimanjaro, I re-read the RealClimate article on Tropical Glacier Retreat.
https://www.realclimate.org/index.php/archives/2005/05/tropical-glacier-retreat/
Considering several comments in this thread regarding possible complete disappearance of glaciers in several regions, it was thought provoking for me to contemplate this statement near the end of the aforementioned article (I’m paraphrasing): It will be the height of irony if it turns out that the IPCC models are right, [East Africa is one region where IPCC models predict precip. increases for the coming century], but that Kaser et al are also right, that Kilimanjaro glaciers begin to advance again AND that proves to help confirm the validity of global warming forecasts.” In other words, as most readers of RealClimate suspect, the atmosphere is so complex that regarding glacier budget, changes such as redistribution of the timing of precipitation, as well as the nivometric coefficient at a place (percentage of water equivalent as snow compared to total water-equivalent precip.), SSTs and resultant evaporation increases, the seasonal cloudcover, the season albedo, the number of hours during the ablation season with temps. above freezing (to allow melting rather than much less efficient sublimation) and a zillion other factors….. may operate in cybernetic loops that actually result in glacier growth in some unexpected places (such as even Kilimanjaro). As a mountaineering guide, I personally would be distraught if glaciers on our local volcano, Mount Baker in Washington {Mauri studies one of them regularly, the Easton Glacier}, were to lose more surface area. The alternative to glacier travel is to climb the rock, and climbing volcanic rock is no one’s cup of tea!
Kaser, et al 2004: Modern glacier retreat on Kilimanjaro as evidence of climate change: Observations and facts. Int. J. Climato. 24:329-339
How are tidewater glaciers handled in these data sets? They go through advance and retreat cycles that have little to do with recent climate changes, and skeptics have occasionally misused information about certain advancing tidewater glaciers. At the very least (I guess) they would add some noise to the data set.
#33 The list of 30 glaciers that the WGMS uses does not contain significantly calving glaciers. For two reasons. First it is difficult to measure calving volume. Second most calving glaciers are larger glaciers and measuring mass balance on larger glaciers has historically not been practical. You are correct that calving glaciers can be insensitive to climate changes during portions of their dynamic cycle, this is not a key to choosing glaciers to measure mass balance. They are not chosen just as climatic signals. Take a look at the list of glaciers reporting to wgms in 2006 and 2007 http://www.geo.unizh.ch/wgms/mbb/mbb10/sum07.html
The only glaciers that have a calving history of the nearly 100 reporting are the Taku Glacier, Konsvegen and Hansbreen. #32 In the short term precipitation has led to higher mass balances in specific regions and even for specific glacier in a region. Note the increase in precipitation that led to higher mass balances for maritime glaciers in Norway prior to 2000. However, precipitation trends tend to not endure, and it is long term temperature trends that have led to the remarkably synchronous advance and retreat of global alpine glaciers over the last 1000 years. Warmer temperatures lead to higher ablation every year, increased precipitation is not consistent every year.
In the North Cascades increased precipitation over the last 15 years still has not overcome the increased ablation and increased ratio of winter season rain and melt events to prevent large negative glacier balances. That has led to the loss of two glaciers that once reported data to WGMS. http://www.nichols.edu/departments/Glacier/diseqilibrium.html
I think we still need the facts and figures on the total mass balance of these glaciers.
It seems to be declining but we still don’t know if it 0.1% or 75.0%.
I don’t know how this report can be produced without containing the total mass balance figures. Are we only concerned about the net change – as long as it is negative?
#35 Mass balance is a measure of the volume change for the glacier for a single year, we could compare that to the overall volume, but that is neither crucial or practical. When sea level rise is reported it is not reported as a percentage change versus the mean depth. When the level of the Great Lakes changes it is not reported as a volume change, but as a lake level change. We report temperature change anomalies, not temperature change as a percent of the mean temperature. The surface mass balance can be determined with more accuracy than the volume of the glacier can. Unlike lakes or oceans we seldom have a good three dimensional map of ice sheet thickness that can be used to accurately assess glacier volume. It can be done, but the costs are huge. So if we switch to a percent of total volume loss for a glacier for each year we are switching to a less reliable number. For the purposes of assessing glacier response to annual climate, surface mass balance provides a means to compare glacier to glacier, just as share prices do for company. When we see share prices we are not told how many share exist etc. What do think Hank Roberts?
One reasons why the percentage of mass lost would be significant is that it would help indicate whether summertime flows will decrease only slightly or massively, especially as we project glacier declines into the future.
I think the loss percentages we’re talking about may be somewhere in the range of 5-15% of total mass since the 50’s. I found some details for one–Lemon Creek Glacier in Alaska–and saw, for instance, this:
“In 1957 Lemon Creek Glacier was 6.4 km long and had an area of 12.67 km2 (Figure 2)(Heusser and Marcus, 1964, p. 63). In 1998 the glacier was 5.6 km long and had an area of 11.8 km2”
So it lost about 12% of its length and about 6-7% of its area. Not how thick it is, or how consistent the thickness is along the length, I can’t directly figure the volume lost, but 5-15% seems like a reasonable guess. Certainly a lot more than .1%.
#38, lost 0.8km in length and 0.87km square in surface. Strange ratio when it was 12.67 going to 11.8 km square, so went to look and the image at http://www.nichols.edu/departments/glacier/lemon.html shows why that is.
Regarding ideas in 34 and 35, measuring mass balance has not been practical for large glaciers, and overall mass balances aren’t weighted by the amount of loss (or the sizes of the glaciers). I should probably look into this more before I ask an overly naive question, but I won’t:
Excepting tidewater glaciers, have large and small glaciers differed in their responses?
If many small companies lose a little bit in share price but a few large companies gain in the same proportion, then an index of the stock market could actually be positive, couldn’t it?
#37 Glacier runoff is dependent on ablation rate and glacier area. As glacier area declines the runoff for a given ablation rate declines. Since area is strongly related to volume, volume too is related to runoff. But it would be more important to assess runoff changes from the changing areal extent which can be easily assessed.
http://www.nichols.edu/departments/glacier/glacier.htm
#38 and #39 Lemon Creek Glacier is one of the glaciers I report to the WGMS. From the research camp we used to be able to ski right onto the glacier from the ridgeline. Now that glacier has thinned more than 25 m and it is a steep hike down the ridge to the glacier. This glacier was averaged approx. 150 m in depth in 1957 and the 25 m loss is between 15 and 20% of its volume. Some glaciers thin considerably over much of their area before retreating much, others thin quickly and only near the terminus well retreating rapidly.
#40 You are correct that the total volume change depends on the average mass balance loss times the area of the glacier, not actually its total volume though. Thus, a big area could skew the population. However the conditions that lead to a positive or a negative mass balance of a small glacier tend to lead to the same for a large glacier.
Thanks, Mauri (Dr. Pelto, I presume?). In my method of guessing, I wasn’t accounting for thinning at all.
You say that “the conditions that lead to a positive or a negative mass balance of a small glacier tend to lead to the same for a large glacier;” and it seems from the data compiled by Haeberli et. al, your work, and the work of others that such conditions prevail over most of the planet. Given that, would you be willing to hazard a guess as to the total % change in the mass of glacial ice on Earth over the last 50 years? Or perhaps a guess as to the range (e.g. a loss of 1-10%, a loss of 10-20%, etc.)?
Anthony Watts (of What’s Wrong with That) doesn’t appear interested in glacier photographs because the location of glaciers is not in accordance with his prejudices about where they really should be.
Presumably, he believes the glaciers have been cunningly put where they are as part of the AGW conspiracy!
As remarked upon elsewhere [Open Mind], Watts disinterest in glacier repeat photography (where it is actually useful and is irrefutable evidence of change), is in stark contrast with his interest in photography of surface weather stations where the use of the photographs is distinctly questionable.
Anthony Watts – your motives are showing!
John A. Davison, #29, you should rephrase it. Your post in #1 is argument from personal incredulity.
If you had phrased it as something along the same lines as:
It seems perfectly reasonable to think that 8 billion humans who all …. can have a profound effect on the health of the planet earth”.
Which is asserting that there is nothing incredulous about the argument, rather than stating that it is impossible it could be wrong.
It isn’t negative
It asks that any counter cannot be “We’re too puny” which you cannot argue against with your original phrasing, since you use the incredulity angle too, but show what it could be AND STILL LOOK THE SAME.
What you put was negative. And not a good argument. And could still be wrong without changing your worldview (you could decide to refuse to believe the counter evidence).
Mauri, Chinese researchers have just announced completion of a \worrisome\ multi-year survey of Tibetan-region glaciers (I assume just the Chinese ones). Do you have access to this and/or can you provide details?
Steve: Good question as always. The most recent report refers to a study at the headwaters of the Yangtze River on the Quinghai-Tibet Plateau remapping the glaciers and comparing glacier extent in 1971 to the present. They noted that glacier area declined from 1247 km2 to 1051 km2. The decline is a 15-20% loss in total glacier area, which is not out of line for this 35 year or so period, with the areal extent changes observed in other ranges. This goes hand in hand with Lonnie Thompson’s report from Naimona’nyi Glacier in Nepal in November indicating that the youngest ice was from 1944, the younger ice layers all having melted. This indicates the lack of a consistent accumulation zone with is a sure forecast for a glacier to not survive.
Thanks, Mauri. Those Xinhua articles are often a little difficult to interpret.
Do these results seem consistent with recent statements by Chinese researchers projecting loss of most of the plateau-region ice by 2050 or so, and do those projections seem otherwise plausible to you?
It is nice we can look for ourselves these days on google earth. The report do not mention specific glaciers. However, if you take a look around the high mountains near the Tunggula Pass-highest railway pass, you will see glaciers arouhd Sab Tangri elevation over 6000 m 35 39 N and 94 15 e. In this area you will see numerous healthy glaciers that are in the 2-5 km in length range. A glacier this long will have significant areas of at least 100 m in thickness. Given mass balance losses noted above of 12 m over the last 30 years. These glaciers will last much longer than 2050 with our current climate. If you look to the highest mountain in the Quinhai Bukadaban there are several glaciers over 15 km in length which will yield even more substantial thicknesses and elevation ranges. To survive a glacier must not have an accumulation zone. A glacier without a persistent accumulation zone will melt away. Such a glacier is receding even in the accumulation zone and I see no sign of that on some of the larger Kunlun Mountain glaciers. So it is not realistic that they will all be gone by 2050. Just as it is not realistic that all Glacier National Park glaciers will be gone by 2030.
Mark #44
I am not a logician. I am a bench scientist who is very concerned about our future. You might be interested in an ongoing conversation I am having with an AGW denier on another forum.
http://theautopsy.wordpress.com/2009/02/09/incredible-ap-finds-way-to-blame-aussie-fires-on-climate-change/#comment-1916
A bit off this exact topic, but here’s a confirmation of something I recall Mauri Pelto telling us a while back — calving, not slip-and-slide at the bottom of the ice, seems to be the cause of the seismic signals:
Step-wise changes in glacier flow speed coincide with calving and glacial earthquakes at Helheim Glacier, Greenland
GRL 35, L24503, doi:10.1029/2008GL036127.
http://www.agu.org/pubs/crossref/2008/2008GL036127.shtml
”
Geodetic observations show several large, sudden increases in flow speed at Helheim Glacier, one of Greenland’s largest outlet glaciers, during summer, 2007. These step-like accelerations, detected along the length of the glacier, coincide with teleseismically detected glacial earthquakes and major iceberg calving events. No coseismic offset in the position of the glacier surface is observed; instead, modest tsunamis associated with the glacial earthquakes implicate glacier calving in the seismogenic process. Our results link changes in glacier velocity directly to calving-front behavior at Greenland’s largest outlet glaciers, on timescales as short as minutes to hours, and clarify the mechanism by which glacial earthquakes occur.”
Received 24 September 2008; accepted 13 November 2008; published 30 December 2008.