2010-10-06 21:08:55Basic Rebuttal 53: Greenland ice sheet won't collapse
gpwayne
Graham Wayne
graham@gpwayne...
81.132.179.253

Skeptical Logic Can't Save Greenland Ice - for that you need to stop climate change

Basic Rebuttal 53: Greenland ice sheet cannot entirely melt

Climate change skeptics like Marc Morano employ gross exaggeration to dismiss or diminish the potential disruption that climate change is likely to bring about. In the Inhofe EWP press blog, Morano made much of this statement:

“...evidence that suggests the frozen shield covering the immense island survived the Earth’s last period of global warming”

Irrespective of what it means to claim the ice sheet ‘survived’ (a rather unqualified claim since survival could be taken to mean that 99% or 1% of the ice was left), it is generally recognised that a complete melt-down of the Greenland ice sheet is far less likely than partial melting. The time-scales over which such a dramatic and complete failure could occur must also be reckoned in centuries rather than decades. Given how much uncertainty surrounds even the accurate measurement of negative mass balance (how much the ice is reducing per year), projections on the century scale are too speculative to be helpful when considering the current problem, which is sea level rise.

Sea level rise will depend on how much water is currently held in the Greenland ice sheet, because the sheer volume of water is so immense that even a small loss of ice will produce considerable rises in sea level – and concerns about loss of mass from ice sheets focuses on sea level rise because this is one of the most serious threats climate change may invoke.

So let’s consider the ice sheets, individually and collectively. Estimates suggest that if the Greenland ice sheet was to melt away to nothing, sea levels would rise around 7 metres. To put that a different way, a loss of just one percent of the ice cap would result in a sea level rise of 7cm.  Consider this in context: if the West Antarctic Ice Sheet (WAIS) were to melt, this would add around 6 metres to sea levels. If the East Antarctic Ice Sheet (EAIS) were to melt, seas would rise by around 70 metres. So a mere 1% loss of ice from these three sources would produce a likely increase in sea levels of around 83cm - from these ice formations alone.

It is important when considering the impact of ice sheet mass balance to bear in mind that a global phenomenon like climate change will produce negative mass balance at both poles, and the shrinking glaciers will also contribute to sea level increases.

While the complete disappearance of Greenland’s ice sheet is hard to predict and the probability lower than a partial collapse, it is clear that even a relatively small loss of ice through melting will produce considerable, and very disruptive, increases in sea levels.

2010-10-07 00:06:04
doug_bostrom

dbostrom@clearwire...
184.77.83.151

Nice explanation!

Perhaps it's worth addressing the term "collapse?" 

The word "collapse" seems a liability in discussing this (realizing of course that you did not introduce it, Graham). Perhaps it was first employed to describe what happens when the ice sheet loses peripheral support, but probably for most people "collapse" conveys dramatic kinetics, not slumping, thus is a tool for skeptics to use while shrilling about "alarmists." Confusion over collapse leads neatly into silly talk about timelines, how long it'll take for the last martini's worth of ice to melt.

 

2010-10-07 00:23:19Collapse...
gpwayne
Graham Wayne
graham@gpwayne...
81.132.179.253

Hi Doug - I agree. I read up some of Robert's work and links, including Bamber and Riva 2010 and I wondered at what they defined as a 'collapse'. I'm happy to use a rather less catastrophic term if we can agree something suitable, bearing in mind this is the terminology used by the scientists themselves.

(I was going to use 'melt-down' but decided the irony would be lost on most deniers)

2010-10-07 00:41:58
doug_bostrom

dbostrom@clearwire...
184.77.83.151

Having mentioned it, I now don't know what to suggest, Graham.

It's sort of a case of "horse out of the barn" in that the title of the piece pretty much requires "collapse." Dealing with the term requires a loop into semantics; a quick search of literature reveals "collapse" as being universally employed by the research community, associated w/such things "rapid deglaciation." Nobody bothers to define the term in papers, suggesting it's implicitly understood.

Maybe not actually possible to address it without distracting from the thrust of the piece. As well, roping in a new term for rhetorical purpose is arguably a loss of fidelity in talking about the science.

A collision of construal, I guess.  

Waffling with the best of 'em, that's me!

2010-10-07 03:50:47Collapse is worth keeping
Robert Way

robert_way19@hotmail...
134.153.163.105
Hey all,
I think that collapse might be worth keeping but should be addressed in the context of a partial collapse. The copenhagen diagnosis gives this assessment

"The largest unknown in the projections of sea level rise over the next century is the potential for rapid dynamic collapse of ice sheets. The most significant factor in accelerated ice discharge in both Greenland and Antarctica over the last decade has been the un-grounding of glacier fronts from their bed, mostly due to submarine ice melting. Changes to basal lubrication by melt water, including surface melt draining through moulins (vertical conduits) to the bottom of the ice sheet, may also affect the ice sheet dynamics in ways that are not fully understood. The major dynamic ice sheet uncertainties are largely one-sided: they can lead to a faster rate of sea-level rise, but are unlikely to significantly slow the rate of rise."

Graham I have two presentations that I did for classes in the past that I think you might find interesting since you have already indicated an inclination towards glaciology. They refer to the potential collapse of the WAIS and to the overall mass balance of the AIS. A lot of the stuff there is undoubtedly of interest when discussing the GIS too... so if you're at all interested you can email me at rway019@gmail.com and I could forward you them.

in terms of the actual collapse of the greenland ice sheet in itself...

During the last interglacial the greenland ice sheet contributed likely 3 m to SLR. Debate still exists as to how warmer it was then. Overpeck et al 2006.

I think Gregory et al (2004) claim that Greenland will be gone in the next 1000 years based on a model that ignores ice dynamics.

Stone et al (2010) state this
"Collapse of the ice-sheet was found to occur between 400 and 560 ppmv, a threshold substantially lower than previously modelled using the standard EISMINT-3 setup. This work highlights the need to assess carefully boundary conditions and forcings required by ice-sheet models and the implications that these can have on predictions of ice-sheet geometry under past and future climate scenarios."

If you talk at all about Greenland losing ice mass now cite Michiel Van den Broeke et al (I just realized this paper is a mix of SMB/radar interferometry and Grace, making it very optimal cause it uses each approach and then validates the results)
2010-10-07 21:22:06Stone et al
gpwayne
Graham Wayne
graham@gpwayne...
81.132.179.253
Hi Robert. I read the Stone excerpt "Collapse of the ice-sheet was found to occur between 400 and 560 ppmv..." and this was what made me wonder how they define collapse, and over what period it occurred (no subscription, so I can't read the paper itself). Do they refer to a self-sustaining process, a complete meltdown in X years, and so on. If you could illuminate this point I'd be grateful.
2010-10-07 21:32:53
Riccardo

riccardoreitano@tiscali...
192.84.150.209

"Careful With That Axe Eugene"

I mean, careful with the use of the word "collapse". As gpwayne said, definitions matter and should always be clear.

2010-10-08 06:33:35
Shirley_Rocks
Shirley Pulawski
missfabulous@verizon...
128.205.183.188
Funny thing is before I read any of the comments, I was really troubled by the use of the word collapse as well. If it's a term used out there in the denialosphere, then it might be wise to use, but perhaps just once, followed by a brief clarification. I think I like terms like "massive reduction" or "severe decrease" more for the general public. I like that you've worked the term "mass balance" in because, while technical, I think in context, it's something people can understand.
2010-10-08 18:14:53Revision
gpwayne
Graham Wayne
graham@gpwayne...
81.132.179.253
After reading Stone et. al (thanks Robert) I have come to the conclusion that the term collapse is simply too dramatic, hyperbolic out of context, and too hard to qualify to prevent abuse and misrepresentation by sceptics. I've made changes in the text accordingly (and marked them in blue so you can find what I've done easily). I think this is the best solution to the terminology problem.
2010-10-08 23:24:13comment
Robert Way

robert_way19@hotmail...
142.162.16.193
I still think you should keep collapse in the title because that is the skeptic argument that is often used. I know that melt-down or melt is probably the appropriate word but i'm trying to think of a word that would encompass what the actually theoreticized mechanism is. Which is an inland propagation of ice flux accelerations in basins below sea level on the west coast. Either way I think its good the way it is, more just bugging me that I can't think of the word myself
2010-10-09 04:44:30
doug_bostrom

dbostrom@clearwire...
184.77.83.151

Perhaps the "collapse" semantic /rhetorical problem could be cleared up by spending a few words in the rebuttal explaining that "collapse" is an accepted technical term, universally employed by the research community in academic publications discussing sudden, broad negative changes in the ice mass balance of a particular ice sheet or glacial feature.

It may well be that leakage/migration of the term from academic to popular communications has not accounted for the different implications of the word in the two different arenas, is a significant barrier to understanding.  

2010-10-09 16:38:49The real problem
gpwayne
Graham Wayne
graham@gpwayne...
81.132.131.87

Seems to me the real problem is that - unusually - the term is actually ill-defined in the science, if at all. Our problem stems from the fact we cannot copy the 'textbook' definition of "collapse", which otherwise is quite hard to qualify. I don't know what they mean - is it some melting, melting past some specific point or factor, a temporal measure related to percentage of mass, or what? My take on the word is that it is actually a poor choice because collapse is not usually a description applied to incremental change, more a binary state.

Personally, if we can't determine what exactly science means, and the word in popular usage suggests complete failure (no such thing as a partial collapse of a bridge, for example - it either collapsed or it didn't) I feel it is better to avoid it altogether. When I find I can either add more verbiage to solve a problem, or simply eliminate the problem, I choose the latter, since doing so doesn't impinge on the argument in any way except in a pedantic sense. Perhaps this issue could be better addressed in the intermediate?

2010-10-09 18:10:01
doug_bostrom

dbostrom@clearwire...
184.77.83.151

Yeah, Graham, I rummaged for a definition or some sort of provenance for the term, couldn't find any. I suppose it could be the equivalent of "greenhouse effect," an ineradicable misnomer rooted in tradition.

Sorry I mentioned it! 

2010-10-10 20:33:37Spare thumbs
gpwayne
Graham Wayne
graham@gpwayne...
81.132.131.87
Any spare thumbs around?
2010-10-11 03:49:32
doug_bostrom

dbostrom@clearwire...
184.77.83.151

Oops. Yes!

Parenthetically, Marc Morano's sort of an odd case. He's a clearinghouse for disinformation, but skeptics don't seem to actually like to talk about him.

2010-10-11 05:44:31
Rob Painting
Rob
paintingskeri@vodafone.co...
118.93.197.192
I think "melt" is problematic too. What about "rapid deglaciation" as John Mercer described it?. That's the only thing preventing me from giving a thumbs up. 
2010-10-11 10:51:34
steve.oconnor

steve.oconnor@hotmail...
152.91.63.37

My initial reading of the research behind the "skeptic argument" leads me to conclude the following:

1) greenland ice-sheet didn't melt entirely in last interglacier (120k years ago)

2) greenland ice-sheet melted so much in one of the interglaciers before that (450k or 800k years ago) that the southern part of greenland (at least) was covered in forests

Surely then, the important point to rebut is that the research supports the *opposite* conclusion to what the press release states (that greenland is susceptible to major melting/collapse) seeing how we're driving warming to >1My conditions.

Also, don't forget Kopp's 2009 nature paper that states that sea-rise was >6.6m in last interglacial (and may be as high as 9.4m)

2010-10-11 18:16:18Responses
gpwayne
Graham Wayne
graham@gpwayne...
81.132.131.87

Dappledwater: sorry, but I think 'rapid deglaciation' is pedantic and unsuited to these basic rebuttals. To start with, define 'rapid' - and what is the difference between 'melting' - a term everyone understands - and 'deglaciation'? What you suggest makes this rebuttal more technical, dense, equivocal and requires more text to explain or qualify 'rapid'. I'm trying to keep things simple here, and I don't think your suggestion materially changes (or improves) the rebuttal at all.

Steve: I chose to address the implicit part of the argument, which depends on trying to minimise the issue by implying that only a complete melt-down would be problematic. Clearly, the sheer amount of water locked up as ice is not well understood in the public mind, so I have tried to make it obvious that our problems occur when only a small amount of ice melts (in percentage terms).

2010-10-11 18:34:23
Riccardo

riccardoreitano@tiscali...
192.84.150.209
It's ok. You may add a figure, something like the map in fig. 1 here, just to look prettier.
2010-10-11 18:58:24No subs
gpwayne
Graham Wayne
graham@gpwayne...
81.132.131.87

Hi Riccardo - I don't have a sub so I can't see the figure, but I do wonder if we might have a copyright issue? Anyway, I've followed Khan's work for several years now, and admired it very much, but I'm staying away from Grace right now until the dust settles on Wu's 'adjustments', both in the Antarctic and re the GRiS.

(If you don't think the copyright will be a problem, email the figure to me at graham@gpwayne.com and I'll have a look - always like a graphic to make things a little more 'instant' if you know what I mean).

2010-10-11 20:23:40
Rob Painting
Rob
paintingskeri@vodafone.co...
118.93.192.88

Gpwayne, you're probably right about that phrase, but however you look at it, this:

Basic Rebuttal 53: Greenland ice sheet won’t melt

Doesn't really make much sense, considering it's already melting. 

I realize your rebuttal doesn't actually address the subject of the skeptic claim, which is "collapse", because that just leads to more complexity.

And just a minor alteration - replace "ice cap" with "ice sheet".   

 

  

 

2010-10-11 20:49:44
nealjking

nealjking@gmail...
91.33.105.82
"Greenland ice sheet won't melt"

=>  "Greenland ice sheet won't melt away"

or: 

=>  "Greenland ice sheet won't disappear"

2010-10-11 21:06:42
Riccardo

riccardoreitano@tiscali...
192.84.150.209

Graham

I sent you the paper, check your inbox if ti went through. You're right about quoting GRACE data at the moment. Another map showing similar things would do as well. It was just to have a nice coloured graph. :)

I think that there is no copyright issue if we share papers privately. If it's true, who have access to a journal could eventually upload the pdf somewhere here.

2010-10-11 21:40:51copyright
nealjking

nealjking@gmail...
91.33.105.82

Riccardo,

If Graham publishes the graphic on the web, it's not private. If it's copyrighted, the copyright applies.

It's totally irrelevant how he obtained it.

2010-10-12 00:21:35
Riccardo

riccardoreitano@tiscali...
93.147.82.173

Neal

we all have used a lot of copyrighted graphs in our posts, the "fair use" rule apply (does this rule exist in the US?). I was talking about privately sharing the pdfs of papers that other do not have acces to. It should be like borrowing a book from a friend.

2010-10-12 06:29:53
CBW
Bruce Worden
cbw723@gmail...
24.205.64.214

Wayne, I think the most effective counter to Morano's claim is to define his "last period of global warming" (i.e., I assume he means the last interglacial), and point out where sea level stood then relative to now (several meters higher, IIRC). You could then point out that recent studies show that Greenland ice is melting, and say how much of the current sea level rise is attributable to that melting. Then your points about how little ice needs to melt to have a dramatic impact on sea level will have the proper context and put the current (and likely future) situation into perspective.

 Also, your line:

"Given how much uncertainty surrounds even the accurate measurement of mass balance (whether the ice is gaining, reducing or maintaining equilibrium), projections on the century scale are not helpful when considering the current situation.",

suggests that we don't know what is happening with the mass balance (gaining ice?), when all the studies I've seen strongly indicate a loss of ice, and even the suggestion that the loss is accelerating. I think you don't mean to suggest that -- I think you are defining the term "mass balance" -- but my first (and second) reading left me with the impression that there was uncertainty about what was happening. You could replace "mass balance" with "ice melting" or some such, and drop the parenthetical. This is the basic rebuttal, after all.

Also, while you say that sea level rise is a serious consequence of climate change, nowhere do you say that it is actually occurring, and has been ongoing for some decades. I think, as I suggest above, you should include that information as early as possible, because most people don't understand why the melting of some ice on a remote frozen wasteland is important.

Also, if there is a SkS article on why sea level rise is bad, I'd suggest linking to it. 

2010-10-14 17:01:42Latest changes
gpwayne
Graham Wayne
graham@gpwayne...
217.44.218.133

Hi folks,

I've done the following: changed the heading to 'entirely melt', changed all instances of ice cap to 'ice sheet', and revised the percentage argument to illustrate the impact of a mere 1% global melt.

I didn't use the graphic Riccardo sent me (thanks anyway) because it would have required as much text again to explain it.

To CBW: You mentioned this: "...suggests that we don't know what is happening with the mass balance (gaining ice?), when all the studies I've seen strongly indicate a loss of ice...my first (and second) reading left me with the impression that there was uncertainty about what was happening."

Your impression is correct. There is tremendous uncertainty about the entire issue. I have to concur with Robert's take on the data, which is subject to constant review, challenge and improvement. Right now, Wu et al have contested the rate and amount of mass balance changes based on comparisons of GPS (Khan) and various Grace estimates. The picture down south is very insubstantial and I'd say that the whole issue is very equivocal right now. It was my intention to make that clear because to fail to address the uncertainties is one way we make things more difficult for ourselves.

2010-10-14 21:45:48
Rob Painting
Rob
paintingskeri@vodafone.co...
118.93.157.171
Looks fine to me.
2010-10-14 22:20:27
nealjking

nealjking@gmail...
91.33.104.180
ok to go
2010-10-15 01:34:56Response
Robert Way

robert_way19@hotmail...
137.122.14.20
I think it is good to go. But that being said I think i got the same impression as CBW to some degree. I think that although we can't make statements about how much ice is being lost with amazing accuracy, even the most conservative methodologies are concluding that ice loss is occurring. So including the "gaining" word might be a little much. I think losing or staying in equilibrium is fine but I would be absolutely shocked if a study came out saying ice is gaining. Either way. Good Job.
2010-10-15 03:12:46On the contentious line
gpwayne
Graham Wayne
graham@gpwayne...
217.44.218.133
OK folks, that line drew too much criticism for me to defend any longer. I've modified it to be more modest in its appraisal of measurement accuracy. Hope that improves it...?
2010-10-15 09:47:55Comment
Robert Way

robert_way19@hotmail...
137.122.14.20
Perfect Graham,
perhaps your original statement might have been the best if we're being absolutely 100% honest in appraising the measurement accuracy but those details are best to be left to Glaciologists to figure out before we pass judgement. I think it could be misconstrued but that is just because much of this is for public consumption. Anyways though good job

Cheers,

2010-10-15 15:13:24Published
John Cook

john@skepticalscience...
124.186.160.198
I'm starting to develop a morbid fascination with wondering what tiny factoid or phrase the skeptics will obsess over in order to avoid thinking about things like metres of sea level rise. My prediction in this case is they'll focus on "Given how much uncertainty surrounds even the accurate measurement of negative mass balance...".
2010-10-15 18:47:59Chuckles...
gpwayne
Graham Wayne
graham@gpwayne...
217.44.218.133

Ah yes John, you're probably right. Trouble is, the only rebuttal we could offer that wouldn't have a line in it for them to chew, would also be one entirely free of facts. Or text.

And the trouble is that when I took another look, to see if I could just dump it, the thought then occurred that by not addressing the uncertainties (Wu et al particularly) we can be painted as concealing them. It would be a no-win situation if it were not for the fact that science will prevail because it must. All the rest is just delay of the inevitable.

2010-10-17 03:51:52
Paul D

chillcast@googlemail...
82.18.130.183

Is it nessacery to say Marc Morano 'employ(ed) gross exaggeration' even if he was doing that?

I think it should be the reader that decides that, based on reading the evidence.

I think it is always important to consider who you are writing for.

2010-10-18 18:06:47Comment
gpwayne
Graham Wayne
graham@gpwayne...
217.44.218.133

The Ville: "I think it is always important to consider who you are writing for".

I'm not sure why you might assume I would fail to make that consideration, but frankly, given that I'm writing ostensibly for those who might take Morano seriously, I would say it was necessary to explain exactly what was going on, and in words of one syllable or less. Which I've done.

It's also a matter of calling a spade a spade. Identifying the tactic assists in foiling the greater assault, and naming names as well as shames.