Foreword: I had originally planned to post a story on this, but Steven Goddard of the UK Register sends word that he has already done a comparison. It mirrors much of what I would have written. There is a clear discrepancy between the two data sources. What is unclear is the cause. Is it differing measurement and tabulation methods? Or, is it some post measurement adjustment being applied. With a 30 percent difference, it would seem that the public would have difficulty determining which dataset is the truly representative one.
UPDATE: The questions have been answered, see correction below – Anthony
Arctic ice refuses to melt as ordered
Published Friday 15th August 2008 10:02 GMT – source story is here
Just a few weeks ago, predictions of Arctic ice collapse were buzzing all over the internet. Some scientists were predicting that the “North Pole may be ice-free for first time this summer”. Others predicted that the entire “polar ice cap would disappear this summer”.
The Arctic melt season is nearly done for this year. The sun is now very low above the horizon and will set for the winter at the North Pole in five weeks. And none of these dire predictions have come to pass. Yet there is, however, something odd going on with the ice data.
The National Snow and Ice Data Center (NSIDC) in Boulder, Colorado released an alarming graph on August 11, showing that Arctic ice was rapidly disappearing, back towards last year’s record minimum. Their data shows Arctic sea ice extent only 10 per cent greater than this date in 2007, and the second lowest on record. Here’s a smaller version of the graph:
The National Snow and Ice Data Center (NSIDC)’s troublesome ice graphThe problem is that this graph does not appear to be correct. Other data sources show Arctic ice having made a nice recovery this summer. NASA Marshall Space Flight Center data shows 2008 ice nearly identical to 2002, 2005 and 2006. Maps of Arctic ice extent are readily available from several sources, including the University of Illinois, which keeps a daily archive for the last 30 years. A comparison of these maps (derived from NSIDC data) below shows that Arctic ice extent was 30 per cent greater on August 11, 2008 than it was on the August 12, 2007. (2008 is a leap year, so the dates are offset by one.)
Ice at the Arctic: 2007 and 2008 snapshotsThe video below highlights the differences between those two dates. As you can see, ice has grown in nearly every direction since last summer – with a large increase in the area north of Siberia. Also note that the area around the Northwest Passage (west of Greenland) has seen a significant increase in ice. Some of the islands in the Canadian Archipelago are surrounded by more ice than they were during the summer of 1980.
The 30 per cent increase was calculated by counting pixels which contain colors representing ice. This is a conservative calculation, because of the map projection used. As the ice expands away from the pole, each new pixel represents a larger area – so the net effect is that the calculated 30 per cent increase is actually on the low side.
So how did NSIDC calculate a 10 per cent increase over 2007? Their graph appears to disagree with the maps by a factor of three (10 per cent vs. 30 per cent) – hardly a trivial discrepancy.
What melts the Arctic?
The Arctic did not experience the meltdowns forecast by NSIDC and the Norwegian Polar Year Secretariat. It didn’t even come close. Additionally, some current graphs and press releases from NSIDC seem less than conservative. There appears to be a consistent pattern of overstatement related to Arctic ice loss.
We know that Arctic summer ice extent is largely determined by variable oceanic and atmospheric currents such as the Arctic Oscillation. NASA claimed last summer that “not all the large changes seen in Arctic climate in recent years are a result of long-term trends associated with global warming”. The media tendency to knee-jerkingly blame everything on “global warming” makes for an easy story – but it is not based on solid science. ®
Bootnote
And what of the Antarctic? Down south, ice extent is well ahead of the recent average. Why isn’t NSIDC making similarly high-profile press releases about the increase in Antarctic ice over the last 30 years?
The author, Steven Goddard, is not affiliated directly or indirectly with any energy industry, nor does he have any current affiliation with any university.
NOTE OF CORRECTION FROM STEVEN GODDARD:
The senior editor at the Register has added a footnote to the article with
excerpts from Dr. Meier’s letter, and a short explanation of why my analysis
was incorrect.
To expound further – after a lot of examination of UIUC maps, I discovered
that while their 2008 maps appear golden, their 2007 maps do not agree well
with either NSIDC maps or NASA satellite imagery. NSIDC does not archive
their maps, but I found one map from August 19, 2007. I overlaid the NSIDC
map on top of the UIUC map from the same date. As you can see below, the
NSIDC ice map (white) shows considerably greater extent than the UIUC maps
(colors.) The UIUC ice sits back much further from the Canadian coast than
does the NSIDC ice. The land lines up perfectly between the maps, so it
appears possible that the UIUC ice is mapped using a different projection
than their land projection.
Click for larger image
Because the 2007 UIUC maps show less area, the increase in 2008 appears
greater. This is the crux of the problem. I am convinced that the NSIDC
data is correct and that my analysis is flawed. The technique is
theoretically correct, but the output is never better than the raw data.
Prior to writing the article, I had done quite a bit of comparison of UIUC
vs. NSIDC vs. NASA for this year. The hole in my methodology was not
performing the same analysis for last year. (The fact that NSIDC doesn’t
archive their maps of course contributed to the difficulty of that
exercise.)
My apologies to Dr. Meiers and Dr. Serreze, and NSIDC. Their analysis,
graphs and conclusions were all absolutely correct. Arctic ice is indeed
melting nearly as fast as last year, and this is indeed troubling.
– Steven Goddard
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Interesting thought, Phil. Anyway to pinpoint the error? Steve?
=======================================
I overlaid the iceextent line from 08/11 onto the earlier chart from 07/14 and found the line has been changed from even the stating point at the beginning of May. I have been following the extent all summer and have seen discussion re: the slope change last month, but more than that has been changed. I may be off a pixel or two, but believe this is pretty accurate:
http://i33.tinypic.com/2rgyzvm.jpg
Why is there so much attention on the Arctic ice? I’m reading this fascinating book “1421: The Year China Discovered America” by Gavin Menzies. In the section on the voyage of Zhou Wen, he reviews the claims that the Chinese circumnavigated Greenland around 1421-2. He discusses evidence of a much warmer climate in Greenland between 1422 and 1428 before the onset of the mini ice age in the 1430s, including a change in the types of flies found during excavations dated to this period in Greenland. He mentions Captain Nares’s voyage in 1875 when all but 15 miles of the Greenland coastline were free of ice. Browsing the image archives at http://arctic.atmos.uiuc.edu/cryosphere/, I don’t see any satellite captures showing an ice free route around the coast of Greenland in recent history (including the most extreme times of the 2007 melt). So why all the attention on the Arctic ice now, when it appears there is ample evidence to suggest the ice has melted more in the recent past than it has melted in the past decade? From the layman’s perspective, this appears to be a Red Herring fallacy.
Phil – thanks for clarifying the projection used in the data. I assumed that the projection used standard k-space, i.e. the sphere tangent to the projection plane at the pole. Now that you bring it up, I do recall the 70 deg comment from the Sea Ice thread at CA.
Your comments may be inconvenient, but they are always thoughtful. It is appreciated.
Mike C (18:14:33) :
Well, uh, in fact the full moon is out.
Can some define what Extent is?
Area is an easy concept for me, Extent seems like it can have many defintions.
[I said Jeff twice above when I meant Phil – sorry!]
John McD, extent is the area of ocean containing 15% ice, ‘area’ is the calculated area of the ice itself.
Why is there so much attention on the Arctic ice?
For the same reason there was so much attention paid to hurricanes a few years ago and global surface temps before that. The warmist spin machine is desperate to find weather events which can be trumpteted as evidence of catastrophic anthropogenic global warming.
If artic ice rebounds, the COGW will seize on something else.
There is no mystery to my calculations, and I explained them clearly in the article.
I took the August 12, 2007 and August 11, 2008 maps from Cryosphere Today – located here :
http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/ARCHIVE/
I counted the number of pixels in the two images marked as being >15% ice concentration (NSIDC’s definition of “extent”.) 2008 was 30% greater than 2007.
You can see the difference visually here:
It is obviously much greater than a 10% increase.
The NSIDC 10% figure was taken from their graph issued with the press release, which showed about 6.3 vs 5.7 last year.
http://nsidc.org/images/arcticseaicenews/20080811_Figure2.png
Additionally, you can see that Arctic melt has nearly stopped this year.
The point of the article is that some of the NSIDC data seems inconsistent with other sources. Some posters here are trying to use NSIDC data to prove NSIDC data – which is obviously a flawed approach.
John McDonald,
Well the NSIDC chart of “Sea Ice Extent” shows “Area of ocean with at least 15% sea ice”.
http://nsidc.org/data/seaice_index/images/daily_images/N_timeseries.png
So extent is a measure of two dimension area.
I don’t know how that would differ from the “atmos” pics of “sea ice concentrations” except they can go lower than 15%. However, I’ve not seen that.
http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/ARCHIVE/20070812.jpg
One more point. The UIUC maps are centered directly over the pole. I did not make any corrections to the data in the article, but had I – the discrepancy would have been increased due to latitudinal distortion as you move away from the poles.
This is very simple stuff. Some people here are making bold declarations that I am in error, without actually addressing the methodology that I used.
Steven Goddard,
You say:
The NSIDC 10% figure was taken from their graph issued with the press release, which showed about 6.3 vs 5.7 last year.
So you have eyeballed a graph and think that your guestimate of what it shows will do, when you could use the actual figures, as I have quoted to you? These figures were given in the very same press release from which that graph comes! To repeat:
Arctic sea ice extent on August 10 was 6.54 million square kilometers (2.52 million square miles), a decline of 1 million square kilometers (390,000 square miles) since the beginning of the month. Extent is now within 780,000 square kilometers (300,000 square miles) of last year’s value on the same date and is 1.50 million square kilometers (580,000 square miles) below the 1979 to 2000 average.
http://nsidc.org/arcticseaicenews/index.html
That is 13.5% greater than last year, not 10% as you claimed. This is basic arithmetic! You are significantly in error, and should have the integrity to say so (and given this blog’s proper concern for accuracy, that is an expectation that I suggest should be widespread here).
As for your comment here –
The point of the article is that some of the NSIDC data seems inconsistent with other sources. Some posters here are trying to use NSIDC data to prove NSIDC data – which is obviously a flawed approach.
I presume by ‘other sources’ that you mean the Cryosphere Today site? What, pray, is the source of their data, other than the NSIDC? It is actually you who is trying to use one representation of NSIDC data to question another! The data is the same in both cases!.
Anyone can make a mistake, Mr Goddard, but not everyone has the capacity to admit it, it seems.
Goddard “error” (i’ll use this euphamism for what he really did) is obvious even to the layman. He totally ignores the scale on the image that shows the various colors represent different levels of sea ice coverage. Red is 60% while purple is 100%. Goddard treats them equally but it is clear from inspection the current year has more area with less % coverage – so goddard’s primitive calculation is bound to be way off.
Its pretty funny how you guys can question the NSDIC’s numbers based on this obviously bogus analysis.
rjb,
How can I best put this? Gavin Menzies’ book has been the object of considerable contempt from professional historians. Here’s a basic Wiki article on the subject –
http://en.wikipedia.org/wiki/1421_hypothesis
Of course, the ‘consensus’ of historians might be wrong and Menzies might be right, so you’re welcome to make your own judgment. Lord Monckton has also referenced Menzies in support of his arguments (http://www.telegraph.co.uk/news/uknews/1533290/Climate-chaos-Don%27t-believe-it.html), so I guess you have company if you judge it to be plausible.
Steven Goddard (10:39:20) :
One more point. The UIUC maps are centered directly over the pole. I did not make any corrections to the data in the article, but had I – the discrepancy would have been increased due to latitudinal distortion as you move away from the poles.
No as pointed out above the minimum distortion is at 70ºN and increases as you move away!
The NSIDC calculations and the JAXA calculations both agree that the extent is today ~9.9 Mm^2 even though they use data from different satellites (SSMI vs AMSR-E). Based on their data the current extent is 8% above last year. You are the odd one out!
Also the Arctic melt has not ‘nearly stopped’, in fact it’s continuing even faster than last year as shown by Aaron Wells graph from CA: http://img352.imageshack.us/img352/4760/seaiceextentlossratebi9.jpg
And that despite the fact that if you’re interested in ‘melt’ you should be looking at area which is even closer
Ed,
You are confusing the calculation of ice area with extent. “Extent” treats all regions greater than 15% concentration equally – just as I did.
Phil and Steven Talbot,
If the UIUC maps are correct, there is nothing in my extremely straightforward calculations which could be broken. You seem to be (rather obtusely) attempting to make an argument that the UIUC maps do not correctly map the satellite data on to the polar projection they use. Polar map projections have minimum distortion at the pole, where the land is perpendicular to the viewer.
If you wish to argue that the UIUC maps are incorrect, that might be an interesting topic of discussion. However, you have yet to make any attempt to analyze the methodology I used – which (obviously) assumes the correctness of the maps.
According to the UIUC maps, there has been almost no change in the amount of Arctic ice since August 8. Once again, if you believe those maps are incorrect – please state your case – and I suggest that you take it up with Phil Chapman over at CT.
Steven Talbot:
I appreciate the links (although like Middlebury’s history department, I do not consider wikipedia a reliable source; rather a convenient research tool, littered with inaccuracies). I only just picked up the book, so it is a starting point for me. I was unaware of the fervent opinions surrounding the publication.
Thanks,
rjb
My Pixel for pixel, calculations for 2005, 2007 and 2008 16´th august:
(ice area 2007 16 aug = 100% )
2007: 100%
2008: 130,3%
2005: 132,7%
I thus get 30,3 % more ice in 2008 than 2007, very close to Mr Goddards 30 % in the article. I can only agree.
Notice also how close 2008 and 2005 are. We are as good as back to 2005 of ice extend.
I then measured the colour nuances, and the area*concentration with 2007 as 100% is :
2007: 100%
2008: 125,0%
2005: 123,6%
So yes, if we incalculate concentrations, 2008 hass not 30 % larger ice extent but ”only” 25% larger ice extend than 2007.
BUT, notice that doing so reveals that there is now more ice in 2008 than there where in 2005…
Another thing, i see here and there in this debate the argument that “NSIDC measures from 15% ice extend”. The thing is, is changes nothing realy. If you compare 2007 with 2008 you use SAME method on both pictures, so if you on BOTH pictures set the limit to 15% this cannot realy change outcome when comparing. Unless of course that one year had extremely much 15% ice. But thats certainly not likely. Check the cryosphere photos and you will see that the big areas are never with low concentration. Such low cincentrations areas of ice mekt away very quickly.
Summa whether you use 15% or 25% changes nothing as long as you use same method on the 2 figures you compare.
Thanks Anthony and Goddard for pointing out this example of distorted data.
Its realy appreaciated by many many many peoble, thankyou.
Cryosphere opereates with concentrations in their graphs, but NSIDC does not, and therefore has no obvious excuse for their underestimation of this years ice extend. It just does not look good as so many many other things in this strange debate.
See for yourself what i measured above, there is now slightly more ice in 2008 than 2005, 16´th august:
http://igloo.atmos.uiuc.edu/cgi-bin/test/print.sh?fm=08&fd=16&fy=2005&sm=08&sd=16&sy=2008
Phil wrote: “Also the Arctic melt has not ‘nearly stopped’, in fact it’s continuing even faster than last year as shown by Aaron Wells graph from CA: http://img352.imageshack.us/img352/4760/seaiceextentlossratebi9.jpg”
Although you claim the the above, I could not find the link anywhere on climateaudit.org that led to the above. Could you provide a definitive URL on CA that leads to the above?
Thanks!
Jack Koenig, Editor
The Mysterious Climate Project
http://www.climateclinic.com
Phil,
A bit more on your post. The graph of melt you sent over shows an average of about 50,000 km2 / day. If it kept that up through the end of the month – which it won’t – the total would only be a loss of an additional 8% before the season ended.
You made the comment that I should be looking at area rather than extent. That is a more difficult calculation and beyond the scope of a newspaper article. According to CT, the minimum area was hit on August 16 or 17 last year.
http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/current.365.jpg
Temperatures around the North Pole have dropped well below freezing the last couple of days. NOAA Buoy 30065 is reporting -4.3C and their North Pole Buoy is reporting -1.5C.
I did a comparison of the CT map projection vs. Google Earth. It appears that CT uses a polar projection taken from an altitude of about 10,000 miles over the North Pole. Unlike the NSIDC extent maps, they do not attempt to elongate lower latitudes – instead preserving the view that a satellite would see from 10,000 miles. That may be what is causing some readers here to be confused.
Apologies – I meant to say William Chapman in my last post, rather than “Phil” Chapman.
Steven Goddard,
However, you have yet to make any attempt to analyze the methodology I used – which (obviously) assumes the correctness of the maps.
Sigh. I have demonstrated that your premise of 10% above 2007 (on the basis of the graph) was incorrect, and that the correct figure was 13.5%. Sorry to repeat myself, but you seem to be ignoring this incontrovertible fact.
If your name were Hansen or Mann you would be eviscerated here for making such an error, and for avoiding recognition of it. As it is, you’ve received plenty of messages of ‘support’, since your article seems to fuel the notion of data being cooked. Such is the nature of ‘scepticism’ when one gets a proper look at it, I guess.
But I give up. I didn’t really imagine that you would want to respond to ‘review’ in the way that we (quite rightly) expect scientists to do.
It is interesting that a self-described warmer objects to internet publication when it was just such quick fast communication that birthed the internet and moves science along much faster than the peer review publication system can.
Ed:
“Goddard “error” (i’ll use this euphamism for what he really did) is obvious even to the layman. He totally ignores the scale on the image that shows the various colors represent different levels of sea ice coverage. Red is 60% while purple is 100%. Goddard treats them equally but it is clear from inspection the current year has more area with less % coverage – so goddard’s primitive calculation is bound to be way off.
Its pretty funny how you guys can question the NSDIC’s numbers based on this obviously bogus analysis.”
Perhaps you should take a look at the NSIDC graph header: “Area of ocean with at least 15% sea ice”. Why should Goddard not treat the colors equally?
And why is his a bogus analysis? The Cryosphere maps are or should be based on real data, and that data should match data that other analyses are based. My understanding is that Steven has attempted to pull data out of the Cryosphere map and compare that data to the NSIDC’s, and I see nothing in principle wrong about that concept.
Glenn,
“My understanding is that Steven has attempted to pull data out of the Cryosphere map and compare that data to the NSIDC’s”
It’s the same data. It all comes from the NSIDC. That is why Goddard’s comments about comparing different sources make no real sense.
Look, the NSIDC data is expressed in a graph (which Goddard has mis-described in terms of difference to 2007). Then it’s represented in a map. Then Goddard counts up pixels and thinks there’s a discrepancy. And all the ‘sceptics’ leap to the conclusion that someone’s cooking the data somewhere. But it’s the same data!
If NSIDC were into the game of cooking their data, then the map would be cooked as well as the graph, no?
Darn, I thought I’d given up. I really, really do now, promise 😉