Guest post by Willis Eschenbach
A few days ago, Steve Goddard put up a post called “Does PIOMAS Verify?” In it, he compared the PIOMAS computer model estimate of the Arctic ice volume with the SIDADS satellite measured Arctic ice area. He noted that from 2007 on, the two datasets diverge.
Intrigued by this, I decided to compare the PIOMAS ice volume dataset with the Cryosphere Today (CT) Arctic ice area dataset. Here is that data:
Figure 1. Arctic ice area (red line) from Cryosphere Today. Black line is a 6 year Gaussian average.
When I compared the two datasets, I expected to find something curious happening with the PIOMASS dataset. Instead, I found a puzzle regarding the CT dataset.
I compared the CT area dataset with the PIOMAS dataset, and I found the same thing that Steve Goddard had found. The datasets diverge at about 2007. So I took a hard look at the two datasets. Instead of an problem with the PIOMAS volume dataset, I found the CT area dataset contained something odd. Here is a plot of the CT daily data with the daily average variations removed:
Figure 2. Cryosphere Today daily ice area anomaly. Average daily variations have been removed.
The oddity about the data is what happens after 2007. Suddenly, there is a strong annual signal. I have put in vertical black lines to highlight this signal. The vertical lines show the end of September of each year. Before 2007, there is only a small variation in the data, and it does not have an annual signal. After 2007, the variation gets large, and there is a clear annual aspect to the signal. The area in September (the time of minimum ice) is smaller than we would expect. And the area in March (the time of maximum ice) is larger than we would expect.
I considered this for a while, and could only come to the conclusion that there was some kind of error in the CT dataset. So I decided to look at another dataset, the NOAA SIDADS dataset.
Again, I removed the monthly signal, leaving only the anomaly. Here is that result:
Figure 3. SIDADS monthly ice area anomaly. Monthly variations have been removed.
Again we see the same oddity after the start of 2007, with a large annual variation where none existed before 2007. In the SIDADS dataset the variation is even more pronounced than in the CT data.
So that is the puzzle. What has changed? Are they using a new satellite? If so, has the changeover been done properly? Since the smallest of the data has gotten smaller and the largest of the data has gotten larger, is the average data still valid? Just what the heck are we looking at here?
Despite searching, I have not been able to find the answer to this question. However, I have great faith that the assembled masses of the WUWT readership will find it very quickly. (And then some of the readers will likely tell me that this shows I am a layman and a fool, and that I should have been able to find the answer easily on my own … so sue me.)
Pop over to Rabett Run.
I think it may be real – maybe it’s “aftershocks” of the 2007 melt? Maybe it’s always like that when the Arctic is at the end of a warm phase? Unfortunately we don’t have good enough data from the 1940s to tell.
Have a look at this recent post on SST by Bob Tisdale:
http://bobtisdale.blogspot.com/2010/05/april-2010-sst-anomaly-update.html
Arctic Sea SST shows a similar pattern, with strong fluctuations over the last 3 years – but note the questions in the comments about which area they use to compute that SST anomaly.
Is this what the future of Arctic looks like, a step change, summer of no ice and winter of a more stable amount of ice, though still declining, just at a far slower rate.
http://rabett.blogspot.com/2010/05/ups-and-downs.html
Increasing seasonal variance, particularly the sharp negative anomaly at maximum melt in September, is (unfortunately) consistent with the notion of progress towards an ice-free Arctic in the summer. If that point were, ever, actually reached, what you’d see is a massive negative anomaly (equivalent to zero ice area/extent) in September, but really very little change in the March/April anomaly. I don’t think even the most ardent warmist is predicting an ice free winter. New ice currently forms each winter all the way down to the Baltic sea, and we’d expect that to continue. But if an increasing proportion of the ice within the main Arctic area is, in fact, thin new ice, that would be expected to melt each summer and reform each winter, then surely this is exactly the pattern you’d expect to see?
Same pattern with AMSR-E.
My fraud dectectors don’t find anything.
I think there’s a good chance it’s a direct effect of the new low magnetic activity sun. Happened about the right time didn’t it?
To me it looks like the instruments used in the satellites are being more fine tuned and see the ice extent better than before. What is considered as ice at the edges anyway? Is slush the same as ice and is that picked up as ice by the satellites?
/Carl
Nigel Harris,
I agree. It is exactly the pattern that we would expect to see. 2007 changed things. It was, indeed, a tipping point (and I know how much that term is loved here. :)). I am one of those alarmists who think that the Arctic will effectively be ice free at the end of the melt period very soon. My specific guess is 2014.
After following this map for about 5 years I have no doubts whatsoever that there is a consistent 5 year significant cooling anomaly for most of South America (specifically Paraguay, Southern and central Brazil, Uruguay, Bolivia. Does no appear to affect sea temps anomaly land only. maybe Meteosul/Watts could comment
http://wxmaps.org/pix/temp8.html
One explanation of the pattern in the last 3 years could be, that Winter ice is a current and Sepetember ice a lagging indicator.
Winter ice is depending on current parameters, especially temperature.
September ice depends a lot on what is left from previous years, particularly the volume.
So, if the overall conditions indicate a turning point to the upside, Winter ice turns up instantly, while September ice still battles with historical leftover.
Phil Clarke says:
June 1, 2010 at 1:40 am
Wouldn’t go there if you paid me. First, he hides behind an alias like a common criminal. Second, he can’t say five words without abusing me, or whoever happens to disagree with him at the moment. I have no use for the man. If you want to pop over there, be my guest, don’t let me discourage you. Me, I prefer to deal with people who are polite and don’t hide their identity.
Nigel Harris says:
June 1, 2010 at 1:58 am (Edit)
Possible, I suppose … but why would that pattern not appear for 25 years, even though the ice cover was reducing, and then suddenly appear? And why would it appear just when the average area started to rise?
And how would we know that it is “consistent with” progress towards an ice-free summer? What theory predicts that? This is the kind of hindcasting that drives me spare. No one (as far as I know) predicted that pattern … but now that it is happening, suddenly it is “consistent with” AGW?
cark1 says:
June 1, 2010 at 2:13 am
From memory, the satellites count as “ice-covered” all gridcells with more than 15% ice.
I’m Polite!
Geology is my area, so I am probably not even close to asking the right question here BUT: is it possible the data is being subjected to some kind of smoothing?
I, for one, predict a good, heavy, Thick ice by 2014.
David Gould says:
June 1, 2010 at 2:15 am
Care to put some money on that prediction? I’m a betting man … a hundred bucks says it won’t go below a million square km of ice by 2014?
And why is it “the pattern that we would expect to see”? Do you know of anyone who predicted it before 2007, anyone who foresaw that we would see a) increasing ice area, combined with b) greatly increased winter ice, and c) greatly reduced summer ice? This is historical revisionism.
Me, I think this new pattern reflects a change in satellites, or a change in procedures, or something like that. But hey, I’ve been wrong before …
Possibly, espen, but the graph that Bob shows for the Arctic doesn’t show anything like the pattern we see in Figure 3. In Figure 3, there is only small variation with no annual pattern until 2007, and large annual variation after that. I don’t see that pattern in the graphic Bob shows:
The variations after 2007 in this dataset are not annual, and only one of them is unusually large.
Manfred says:
June 1, 2010 at 2:32 am (Edit)
Possible, but there was an slight upturn around 1984, and we didn’t see that pattern.
Willis Eschenbach,
No, I know of no specific prediction of this. However, ice cover is a two-dimensional model. Thus, if we have strong melting in the melt period, we would still expect the ice to recover on the surface during winter, and to roughly the same extent as usual – in other words, we would see a strong up and down signal, with more variance between the top and the bottom.
You are correct that there would be no expectation for a higher rebound in winter. That is more likely to be noise over the last couple of years.
As to a bet, $100 sounds fine. I am assuming that you are talking in US dollars.
And which dataset do you want to use? They are all somewhat different in the values that they give, as they all have slightly different procedures. These guys http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm are fine with me. We should wait for corrections, though. I am not sure how long they take, but perhaps the data as presented on that site on 1 November 2014, my time (Australian time)?
Willis Eschenbach asked:
“No one (as far as I know) predicted that pattern … but now that it is happening, suddenly it is “consistent with” AGW?”
This pattern of behaviour of the Arctic ice was indeed predicted by the models at least four years ago, and prior to the 2007 melt:
“Sea ice evolution over the 20th and 21st centuries as simulated by current AOGCMs” Olivier Arzel, , Thierry Fichefet and Hugues Goosse, Ocean Modelling
Volume 12, Issues 3-4, 2006, Pages 401-415
From the abstract:
“We show that the amplitude of the seasonal cycle of sea ice extent increases in both hemispheres in a warming climate, with a larger magnitude in the Northern Hemisphere. Furthermore, it appears that the seasonal cycle of ice extent is more affected than the one of ice volume.”
By the way, I am not as confident as my bet suggests. It is just interesting to have a managable consequence for being in error. 🙂
Does something similar repeat in the Antarctic ice extent?
If it does then maybe it is satellite, instrumental or processing based.
If not then it may be inherent in the present behaviour of the Arctic ice.
So Willis, what was the Sun doing in 2007?
Tom P,
Thanks for that. Very interesting.
Willis Eschenbach says:
If some people are right about reaching a tipping point (about which I am, genuinely, sceptical), then unfortunately this is what you’d expect to see. Maximum winter ice extent would stay high, but minimum summer extent would start to dramatically decrease. And the onset would be quite sudden – that’s what “tipping point” means, of course. All it would take is one year with unusually high level of summer ice loss – whether it was caused by air temperatures, sea temperatures, wind patterns, ice shear, or hyperactive polar bears. From then on, if changing Arctic climatic conditions have been gradually making it harder for ice to both reform and build enough thickness not to melt away the next summer, you’d get this effect.
The increase in winter ice extent is, indeed, something that nobody predicted. But at the risk of annoying you further with my hindcasting, that also isn’t too ridiculous. If 2006-07 was a particularly “bad” year for Arctic ice formation, which triggered a tipping point in summer ice extent, then unless you’re an extremist “death spiral” type, you might expect some recovery in winter ice extent simply because we’re no longer in such a “bad” state (cooler temps, different wind patterns, whatever).
As a genuine sceptic, I have a completely open mind as to where it is likely to go from here. Certainly, for anyone sticking their neck out for an ice-free summer in 2014, the current pattern would be supportive. But the fact that winter extent is holding up and even increasing suggests, maybe, this is only a temporary situation, and the ice will “tip” back into the previous pattern again. As other posters have pointed out, our detailed history of ice extent is too short to know whether, and how frequently, these sorts of events may have happened in the past, and, if so, how long they typically last for.
I seem to remember an article here pertaining to the 2007 Arctic melt, and how it was caused by not rising temperature, but rather a shifted/unusual wind pattern which blew the ice out into warmer waters which in turn melted the ice.
Could it be that what we’re seeing in the graph is not as a result of large temperature fluctuations, but rather, large swings in Arctic wind patterns which might be caused the current extended solar minimum? Just a thought.
Also, looking at the historical Arctic temperature charts at I see no particularly unusual changes in the temperature patterns – apart from 2006 perhaps which shows some pretty wild readings at the beginning of that year (same with 1976 I notice too).