Guest Post by Willis Eschenbach
This topic is a particular peeve of mine, so I hope I will be forgiven if I wax wroth.
There is a most marvelous piece of technology called the GRACE satellites, which stands for the Gravity Recovery and Climate Experiment. It is composed of two satellites flying in formation. Measuring the distance between the two satellites to the nearest micron (a hundredth of the width of a hair) allows us to calculate the weight of things on the earth very accurately.
One of the things that the GRACE satellites have allowed us to calculate is the ice loss from the Greenland Ice Cap. There is a new article about the Greenland results called Weighing Greenland.
Figure 1. The two GRACE satellites flying in tandem, and constantly measuring the distance between them.
So, what’s not to like about the article?
Well, the article opens by saying:
Scott Luthcke weighs Greenland — every 10 days. And the island has been losing weight, an average of 183 gigatons (or 200 cubic kilometers) — in ice — annually during the past six years. That’s one third the volume of water in Lake Erie every year. Greenland’s shrinking ice sheet offers some of the most powerful evidence of global warming.
Now, that sounds pretty scary, it’s losing a third of the volume of Lake Erie every year. Can’t have that.
But what does that volume, a third of Lake Erie, really mean? We could also say that it’s 80 million Olympic swimming pools, or 400 times the volume of Sydney Harbor, or about the same volume as the known world oil reserves. Or we could say the ice loss is 550 times the weight of all humans on the Earth, or the weight of 31,000 Great Pyramids … but we’re getting no closer to understanding what that ice loss means.
To understand what it means, there is only one thing to which we should compare the ice loss, and that is the ice volume of the Greenland Ice Cap itself. So how many cubic kilometres of ice are sitting up there on Greenland?
My favorite reference for these kinds of questions is the Physics Factbook, because rather than give just one number, they give a variety of answers from different authors. In this case I went to the page on Polar Ice Caps. It gives the following answers:
Spaulding & Markowitz, Heath Earth Science. Heath, 1994: 195. says less than 5.1 million cubic kilometres (often written as “km^3”).
“Greenland.” World Book Encyclopedia. Chicago: World Book, 1999: 325 says 2.8 million km^3.
Satellite Image Atlas of Glaciers of the World. US Geological Survey (USGS) says 2.6 million km^3.
Schultz, Gwen. Ice Age Lost. 1974. 232, 75. also says 2.6 million km^3.
Denmark/Greenland. Greenland Tourism. Danish Tourist Board says less than 5.5 million km^3.
Which of these should we choose? Well, the two larger figures both say “less than”, so they are upper limits. The Physics Factbook says “From my research, I have found different values for the volume of the polar ice caps. … For Greenland, it is approximately 3,000,000 km^3.” Of course, we would have to say that there is an error in that figure, likely on the order of ± 0.4 million km^3 or so.
So now we have something to which we can compare our one-third of Lake Erie or 400 Sidney Harbors or 550 times the weight of the global population. And when we do so, we find that the annual loss is around 200 km^3 lost annually out of some 3,000,000 km^3 total. This means that Greenland is losing about 0.007% of its total mass every year … seven thousandths of one percent lost annually, be still, my beating heart …
And if that terrifying rate of loss continues unabated, of course, it will all be gone in a mere 15,000 years.
That’s my pet peeve, that numbers are being presented in the most frightening way possible. The loss of 200 km^3 of ice per year is not “some of the most powerful evidence of global warming”, that’s hyperbole. It is a trivial change in a huge block of ice.
And what about the errors in the measurements? We know that the error in the Greenland Ice Cap is on the order of 0.4 million km^3. How about the error in the GRACE measurements? This reference indicates that there is about a ± 10% error in the GRACE Greenland estimates. How does that affect our numbers?
Well, if we take the small estimate of ice cap volume, and the large estimate of loss, we get 220 km^3 lost annually / 2,600,000 km^3 total. This is an annual loss of 0.008%, and a time to total loss of 12,000 years.
Going the other way, we get 180 km^3 lost annually / 3,400,000 km^3 total. This is an annual loss of 0.005%, and a time to total loss of 19,000 years.
It is always important to include the errors in the calculation, to see if they make a significant difference in the result. In this case they happen to not make much difference, but each case is different.
That’s what angrifies my blood mightily, meaningless numbers with no errors presented for maximum shock value. Looking at the real measure, we find that Greenland is losing around 0.005% — 0.008% of its ice annually, and if that rate continues, since this is May 23rd, 2010, the Greenland Ice Cap will disappear entirely somewhere between the year 14010 and the year 21010 … on May 23rd …
So the next time you read something that breathlessly says …
“If this activity in northwest Greenland continues and really accelerates some of the major glaciers in the area — like the Humboldt Glacier and the Peterman Glacier — Greenland’s total ice loss could easily be increased by an additional 50 to 100 cubic kilometers (12 to 24 cubic miles) within a few years”
… you can say “Well, if it does increase by the larger estimate of 100 cubic km per year, and that’s a big if since the scientists are just guessing, that would increase the loss from 0.007% per year to around 0.010% per year, meaning that the Greenland Ice Cap would only last until May 23rd, 12010.”
Finally, the original article that got my blood boiling finishes as follows:
The good news for Luthcke is that a separate team using an entirely different method has come up with measurements of Greenland’s melting ice that, he says, are almost identical to his GRACE data. The bad news, of course, is that both sets of measurements make it all the more certain that Greenland’s ice is melting faster than anyone expected.
Oh, please, spare me. As the article points out, we’ve only been measuring Greenland ice using the GRACE satellites for six years now. How could anyone have “expected” anything? What, were they expecting a loss of 0.003% or something? And how is a Greenland ice loss of seven thousandths of one percent per year “bad news”? Grrrr …
I’ll stop here, as I can feel my blood pressure rising again. And as this is a family blog, I don’t want to revert to being the un-reformed cowboy I was in my youth, because if I did I’d start needlessly but imaginatively and loudly speculating on the ancestry, personal habits, and sexual malpractices of the author of said article … instead, I’m going to go drink a Corona beer and reflect on the strange vagaries of human beings, who always seem to want to read “bad news”.
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“A C Osborn says:
May 23, 2010 at 10:26 am
I am not sure if anyone else has posted this here, but The Hockey Schtick has just posted a stidy that completely refutes what the Satellites are finding, the ice is growing at 5.4 cm/yr.”
http://www.cfa.harvard.edu/~wsoon/MattCronin-Mar21-07-d/Johannessenetal05-GreenlandIceFinal.pdf
The paper is from 2005, measurements from 1992 to 2003 by satellites ERS-1 and ERS-2 – it would be conceivable that the GRACE instruments are more precise as they’re newer.
Hey Roger,
How do you measure something with “climate modelling”? My understanding was that any work with models involves measuring something(s), and feeding the measurements IN to the model.
Just trying to get my facts straight… 🙂
JimB
I suspect the ice loss isn’t due to melting primarily, but mostly to glacial calving. (Ditto in the Antarctic.) I believe that glaciers in those regions are pushed outward mostly by the weight of precipitation in their interiors, and that the glaciers move in fits-and-starts for periods of decades. So it could be that glaciers at the moment are in a high-flow phase that is not representative of the long-term trend, but higher than it.
Historical evidence tells us that Greenland’s glaciers have retreated and advanced a few times since the Vikings first went there. I would guess often at faster rates than 200 km^3 per year. The AGW alarmists use the most hyperbolic references to elicit apprehension in the public, which is really despicable.
Straight-line extrapolation of an instantaneous (6 years to 15,000) rate is of course ridiculous, but useful to show how paltry the problem is.
AGW propagandists are not above doing this sort of thing.
Now for an exercise in climate science; 0.007% is 70 ppm loss per year (of the Greenland icesheet), and the yearly increase in CO2 is only 1 to 2 ppm, so OBVIOUSLY, increasing CO2 is not the main driver of Greenland’s ice melting, or global warming, LOL.
Or else, it’s worse than we think…
Curiously, such hypocritical proponents of critical thinking as Michael Shermer typically have no problem with such hyperbole, because their critical thinking is generally deployed only on behalf of scientism, not against it.
Given that they are measuring the gravity anomaly, rather than anything else, it is only one possibility that the decrease in the gravity anomaly is due to ice melt. It could well be so. However, other sources do spring to mind As such it is potential confirmation of ice melt, but not definitive confirmation of ice melt.
i don’t buy it at all. greenland and antarctica are gaining ice…buildings are being buried, and how about the glacier girl, buried under 270 ft of ice. that’s over 5ft a year.
south pole station
greenland DYE stations
Willis raises a reasonable point. But he frames it in a misleading way: “There is a new article about the Greenland results called Weighing Greenland.”
The article is a brief bio piece about Scott Luthcke who happens to work on estimating the mass of Greenland. If the article were about Greenland, then I would agree with Willis’s point. In fact I would make an even stronger criticism of the statement: “Greenland’s shrinking ice sheet offers some of the most powerful evidence of global warming.” No context is given for this. We are not told what the ice volume loss was estimated to be before Luthcke work or why a warmer Greenland is not a regional phenomenon.
I searched Grist’s website for articles about Greenland and found this:
http://www.grist.org/article/greenland2 (12 Jan 2009)
Massive Greenland meltdown? Not so fast, say scientists
The recent acceleration of glacier melt-off in Greenland, which some scientists fear could dramatically raise sea levels, may only be a temporary phenomenon, according to a study published Sunday.
There was also an article about making beer from glacier melt. That might by the real news story.
Brad says:
May 23, 2010 at 5:47 am
Show me that it was BP that “modified” the blow-out preventer.
Let’s do a comparison between this scary number and another that is probably equally or more scary… how much water vapor gets stripped from the earth’s upper atmosphere by solar winds? Our atmosphere is slowly being eroded, and it’s only a matter of (a very long) time before there is just nothing left!
I have no idea what the real numbers are, but can anybody come up with a ballpark estimate?
Just ask’n!
Yeah, I’ve been thinking that their reliance on extrapolating this finding may come back to bite them in the behind, like their extrapolations of increasing hurricanes, decreasing Arctic ice cap, etc.
Paul Daniel Ash says:
May 23, 2010 at 6:59 am
Is anyone talking about the loss of the Greenland Ice Cap? No, no they are not. So this is a ridiculous straw man>>
Paul, in any large organization or community there are two types of information upon which decisions are made. Percieved and reality. This is closely related to value which can also be percieved or real. When perception diverges from reality, bad decisions get made.
This kind of study is dangerous not because anyone is talking about the loss of the Greenland Ice Cap specificaly, nor because it is factualy innacurate. It is dangerous because the manner in which it is presented creates a perception that is out of proportion to reality. It is dangerous because the culture within the climate research community rewards perception management. Had the conclusion of the paper been that the changes measured were of complete insignificance, the likelihood for funding of follow up studies would be zero. The culture and funding mechanisms within the climate community promote the presentation of studies like this in such a manner that they seem significant and so worthy of being publsihed, quoted in the media, and of coure, further funding.
When perception management over rides reality in a single study, it is unimportant. When perception management becomes systemic, then perception continus to diverge from reality, and the perception managers must make increasingly alarmist statements and increasingly selective use of data to maintain the fiction that they have created. It happens in busines, and Fortune 500 companies have crashed and burned because of it.
But climate decisions aren’t about the 200,000 employees in a company who will be affected by bad decisions. Climate decisions are about the 7 billion people on the planet and how they will be affected. If CAGW happens, billions will die. If we cut fossil fuel consumption by 50% to 80% as proposed, billions will die.
So itz not about a straw man. Itz about debunking a study that adds to a false perception of reality instead of adding to a better understanding of reality. Itz about understanding that climate research happens in an environment where both the culture and the funding mechanisms influence perception management over reality. Itz about understanding that correcting this drift from reality can only be accomplished by debunking all the straws one at a time, until the straw man is gone and only the framework of reality upon which he is built remains.
The GRACE satellites are also being used to determine the depletion of groundwater:
It is good to keep a weather eye on GRACE, and the way it is being used to promote the AGW agenda, as well as other policies based on “sustainable”/rationing arguments.
I wonder how solid the science is behind it? There are a lot of anomolous accelerations which scientists are not able to explain. And I recall that the gravity readings for Venus’ surface are used by some planetary scientists to argue for a thick crust, and by others to argue for a thin crust!
What about earth’s varying efield, could that affect the readings? You will excuse the amateur musings 🙂
Willis wrote:
“And as this is a family blog, I don’t want to revert to being the un-reformed cowboy I was in my youth, because if I did I’d start needlessly but imaginatively and loudly speculating on the ancestry, personal habits, and sexual malpractices of the author of said article … instead, I’m going to go drink a Corona beer and reflect on the strange vagaries of human beings, who always seem to want to read “bad news”.”
Old saying in the news biz: If it bleeds, it leads.
Excellent posting, Willis. I find it very revealing that what they leave out of these kind of articles, like the one you have just disembowelled, is more scary than the fear they seem to be trying (knowingly) to induce. They must know that they are leaving out important pieces of information. Or that they are incompetent in the extreme. Very scary either way. Why the need for their choir to be afraid all the time? Our choir does not need fear to manipulate. Even those who are “sold” on AGW, would have to acknowledge that this should raise some hard questions that need answers, not blind faith.
About .6mm /yr, or 6cm/century (assuming the past 6 years’ warmth continues…)
Good post Willis with further explanation. But the forecast remains the same ; between 12k and 17 k, the Greenland ice cover will be gone. But the next ice age is just around the corner. Greenland has no need to worry.
Another way to put these trifling changes into perspective would be to express it as a proportion of the annual turnover of ice. Every year a huge quantity of water must fall as snow to be packed into ice and lost to the icesheet by melt and glacial calving. It would be utterly amazing if it was in such perfect equilibrium that it didn’t vary up and down a little.
I suspect one of the more erudite contributors may have the figures to hand.
I didn’t read all the comments but has there been any calculations of sublimation losses during extended periods of cold by dry weather conditions. This would certainly be a factor in the interior of Anarctica where annual snow is a few centimetres. I remember as a child helping my mother hang out the clothes on the clothesline in our backyard in a Manitoba winter where they fairly handily dried in (-)30C. The steam from the laundry frosted your eye-lashes together and the sheets were like sheets of plywood for a while but as I recall, in a few hours, they were pretty dry.
Crustal isostatic movement (Post Glacial Rebound, PGR) is taken into account to the degree with which it can be estimated.
In most cases the margin of error for the PGR is not much smaller than the volume of ice melt that is being asserted.
200 km^3/yr is well within the margin of error of any geophysical measurements of volumetric changes of a 3 million km^3 sheet of mobile ice.
Good point.
The ice maker in my freezer only “calves” ice cubes, when it’s making more ice than it can handle.
If the temperature in the freezer is too high, calving doesn’t occur.
Jeff L says:
May 23, 2010 at 6:37 am (Edit)
Jeff L, you and tty are right about isostatic rebound, and I was wrong. The mass of the Greenland bedrock is not changing. But what I hadn’t considered is that when it moves closer to the GRACE satellites, it will be affecting the satellites more strongly. This will affect the results.
However, the GRACE folks are not fools. There’s a variety of discussions between the scientists involved on this exact subject here. So I would say that their error estimates are no more out of line than the rest of the basic scientists in the field … which is either damning with a faint praise, or praising with a faint damn …
Look, folks, the GRACE data is amazing stuff. It can detect the change in the weight of Brazil resulting from the annual hydrological cycle. The problem is not the data … it’s the spin, and we’re up to 45RPM and heading for 78RPM as we speak.
Thanks for this enlightening article Willis – it’s good to see the AGW hyperbole put into perspective every now and then. It would be interesting to see a graphical representation of the 0.007% icecap ‘loss’ but not sure if my monitor’s big enough.. 🙂
Toby,
Trenberth’s comment piece in Nature on the Lyman et al paper you link has to be one of the most ironic scientific articles I’ve ever read in Nature.
Basically, he says it does not amount to a hill of beans.
“You guys always discount the downside risks. It would be an interesting intellectual exercise, except that you are gambling with huge stakes. Anyway, enjoy the beer.”
This snippy little line is incredibly deceitful at best.
Very easy to say the same…as in YOU guys always IGNORE the downside risks, however, that discussion ultimately digresses to facts, and then it seems to just end at that point.
There are ramifications to the course that Warmers would set us on, that are continually ignored by the AGW religion. And that’s a criticism you want to foist on US?
JimB