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.)
Although the main focus on Arctic ice is summer albedo, come winter is the ice not acting as an insulator for the relatively warm waters flowing in? Significantly lower ice area by sept 07 would leave the ocean exposed to Arctic storms such that it looses more energy than “usual” into the subsequent re-freeze eventually resulting in more ice by thaw time which in turn has retained more ocean heat for the coming thaw and so on into subsequent years.
Looks like a pretty poor control loop (under damped) that will take a few years to return to the previous narrower range after the initial (07 type) “shock”.
Just a thought.
It is the result of ever thinning Arctic Ice. When that ice has reached a threshold thickness of about two feet, it breaks up and melts away very quickly over vast areas. This happens in the second half of summer as of 2005.
The signal you see in the extent graph is a classic example of dissipation containing a catastroph motive. The latter depicts a physics/mathematical term, of course.
In late autumn the sea freezes again, of course, en by virtue of its relative closedness it freezes up over the entire extent, rendering winter and early spring extent near normal every year.
What has been totally missing van Arctic Sea-ice analysis untill very recently is this simple catastrophe concept, which totally delinearizes the melting process. This is why 2007 came as a big suprise. But the holes in half that sea ice that appeared in august 2005 made a melting season like 2007 in fact very easy to predict.
The sea ice has become very weak and a first ice free summer might just be this year. Or in five years.
It is like predicting the exact moment a melting icicle will drop off the gutter. You only know it will drop soon.
IIRC, Summer 2009 arctic sea ice extent minimum was greater than Summer 2008 arctic sea ice extent which in turn was larger than that recorded in Summer 2007. That pattern does not agree with the CT & SIDADS arctic sea ice anomaly charts presented here which show greater negative anomalies for 2009 than for 2008.
http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm,
http://arctic-roos.org/observations/satellite-data/sea-ice/ice-area-and-extent-in-arctic, and
http://ocean.dmi.dk/arctic/icecover.uk.php all confirm greater 2009 sea ice extent minimum than that observed in 2008.
Seems to me grounds exist to question CT and SIDADS sea ice extent anomalies.
My guess would be new processing software installed in 2007. Giving a different result from then on.
The annual variation appears in independent datasets so we cannot blame instruments or anything else. It is clearly a real variation.
From the videos I’ve made, it is my opinion that the Arctic has shifted to a different weather pattern where the ice is buffeted from the Bering strait each year. Warm ocean water gets pushed into the ice melting it for the last 3 years. Visually it is different from previous years and IMHO has nothing to do with warming.
” Georg Hoffmann says:
June 1, 2010 at 6:38 am
Trivial. Think about it a bit more or look here
http://www.scienceblogs.de/primaklima/2009/06/die-mar-vom-rasend-schnellen-meereiswachsen-und-dem-was-die-modelle-vorhersagen-teil-ii.php
The models show it as well, but of course later.”
No doubt you can make your models fit the observations, at least roughly.
JJB MKI says:
June 1, 2010 at 9:57 am
How do 31 years of satellite measurements (and less than a decade of accurate ones) make a ‘trend’, a ‘tipping point’ or a ‘death spiral’? Even if as some have asserted / wildly speculated, the summer Arctic does become ice-free by 2014, why, particularly in the light of early 20th century observations of severe Arctic melt, and longer term proxy observations of temperature oscillations on a millennial timescale, should that be taken as unusual, let alone support of an AGW hypothesis? Satellite observations might be useful as an observational tool, but using them as a basis for prediction and modelling from an insignificant sliver of data goes beyond clutching at straws. It is no surprise that people who deal with these observations for a living (or an obsessive hobby) might imbue them with more significance and predictive value than they actually hold, but really, I am in a better position to make alarming pronouncements on ‘tipping points’ in the global economy having looked at three minutes worth of stock market graphs, especially, to further the metaphor, with my vague and incomplete understanding of the economics involved.
The most salient point in 100+ comments. It will be ignored. Where’s the fun in it?
“Dave says:
June 1, 2010 at 10:31 am
IIRC, Summer 2009 arctic sea ice extent minimum was greater than Summer 2008 arctic sea ice extent which in turn was larger than that recorded in Summer 2007. That pattern does not agree with the CT & SIDADS arctic sea ice anomaly charts presented here which show greater negative anomalies for 2009 than for 2008.
http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm,
http://arctic-roos.org/observations/satellite-data/sea-ice/ice-area-and-extent-in-arctic, and
http://ocean.dmi.dk/arctic/icecover.uk.php all confirm greater 2009 sea ice extent minimum than that observed in 2008.
Seems to me grounds exist to question CT and SIDADS sea ice extent anomalies.”
The largest negative anomaly values don’t necessarily occur at the summer minimum, they lag by a month or more depending on the rapidity of the refreeze.
BTW, whatssup with the vertical scales on the anomaly graphs? Anomalies ranging from 8-11 million km2, what am I missing here?
chopbox says:
June 1, 2010 at 8:17 am
So we are going to believe this guy’s anecdotal information and discount measurements when it suits us?
Frankly, this guy looks a little squirrely to me. If you want to believe him, go right ahead. I’m afraid that the two recent expeditions to the North Pole that got frostbite and had to be rescued, because they could not negotiate the floating ice mountains and record low temperatures, believed him and others of his ilk. To their surprise.
One guy’s bread is another man’s poison. That is why we have to get good hard RAW data.
Jeff Id says:
June 1, 2010 at 11:01 am
“The annual variation appears in independent datasets so we cannot blame instruments or anything else.”
That depends. Then we would need a flow-chart of really, really raw data and all the way to the plots. Just like for groundstations. Are there any common points?
Are all those plots from different satelites? Just asking, because I havent got a clue.
The really,really raw data is of course just gibberish. Time values for reflected radar waves? Whatever it is,it will need heavy processing to get something one could call ice thickness.
If it comes from different satelites maybe the processing software is outsourced to the same software company in china….just kidding.
2006/7 marked the transition from a predominantly MY ice regime to a predominantly FY ice regime. FY ice not only melts faster but breaks up easier and moves around more easily. The Arctic is now showing seasonal sea ice now like the Antarctic.
Yes, a different weather or flow pattern is a likely explanation. Mathematically (not much math but graphically) if the nearly sinusoidal variation shifts phase slightly when compared to the average for previous years, a larger fluctuation will be seen. Find a new norm for the past three years and all the previous years will show seasonal fluctuations. The variation in extent clearly has not changed that much. Things may or may not slip back in phase, but whether or not this has anything to do with global warming is TBD.
JJB MKI says:
June 1, 2010 at 9:57 am
Ice is being used as a diversion from the real fact that CO2 does not cause global warming. They tried to substitute “climate change” for “global warming”, but that did not work, so they are throwing lots of mud darts around hoping for “stick”.
Ice is what they have left. It is another multivariate system that defies easy explanation (although it is much simpler, even, than the “global” climate). Ice extent is like the Chewbakka defense – “Look at the silly monkey” while the magician picks our pockets. It is neither global, nor climate, nor if it all melted would sea levels rise.
Let us always, after all this speculative icicle fun is over, focus on the main event. Does man cause catastrophic climate changes globally?
If AGW were true, the climastrologers would not be focused on ancillary issues, like ice, or malaria, or who someone’s mother is!
Remember, more CO2 = good times, not bad.
@ur momisugly 899 says:
June 1, 2010 at 3:12 am
“So Willis, what was the Sun doing in 2007?”
The solar wind velocity was very generous through 2006/7 winter:
http://www.solen.info/solar/coronal_holes.html
This led to a very warm winter in England:
http://climexp.knmi.nl/data/tcet.dat
this is a common denominator in years with more ice melt, look at temperatures from October to February in 1989/90, 1992/3 (see ice increase mid `92, {not Pinatubo!}), 1993/4, and 2006/7. Notice that the high ice loss years are also hotter on the yearly figure.
http://wattsupwiththat.com/2010/06/01/the-ice-who-came-in-from-the-cold/#comment-401337
The next thing to factor in is Sudden Stratospheric Warmings:
http://www.geo.fu-berlin.de/en/met/ag/strat/produkte/northpole/index.html
There was a serious lack of SSW`s through the 1990`s. Late warmings seem to correlate well to high ice loss years. With the SSW comes the mixing of sub tropical, and polar air through a colapse of the polar vortex.
So if its not one thing, its another.
That pattern makes sense to me. It’s not much different than saying the May and June NSIDC extent graphs are bottlenecked, and why (as are generally November and December). Extent is not volume. 4 inches thick and a mile x mile wide in March counts for the same extent as 4 feet thick and a mile x mile wide in March. And in the core areas of the Arctic, you’re always going to get at least that 4″ thick during growth season. Global warming will have gone a very far way down the road indeed before that was no longer true!
Tom P says:
June 1, 2010 at 3:11 am
Thanks, Tom P. Some problems with that.
1. There was no increase in the seasonal cycle from 1979 to 2007. Where is the model prediction during that time?
2. There has been no statistically significant warming in the last 15 years. Why would the seasonal cycle suddenly jump in 2007?
3. The models also predict a decreasing ice area …
Here’s what I asked:
w.
899 says:
June 1, 2010 at 3:12 am
Taking a nap?
More convenient science:
US projects 4 percent emissions rise by 2012 to UN
http://news.yahoo.com/s/ap/20100601/ap_on_re_us/un_un_us_climate
The explanation may be simpler than we think. In 2007, the ice melt was substantial. The new ice is necessarily thiner now, and will take some time to reach its previous thickness. In the mean time, that thiner ice is more subject to wider fluctuation (warming in spring melts more thiner ice, and cold temperature can reach previous extand levels, resulting in wide fluctuation) . The volatility will remain until the thickness is back to previous levels.
@ur momisugly bubbagyro says:
June 1, 2010 at 12:50 pm
“Remember, more CO2 = good times, not bad.”
And a warmer World will have enough rain to feed us all, and shrink the deserts, just look at East Australia bloom, locusts and all. The history lesson about the collapse of all the great civilisations of the past, due to cold and drought, seems to have gone over the heads of many. Our only climatic threat in reality, is run away Global cooling. How often does the Sun actually make it too hot here?
Malaga View says:
June 1, 2010 at 4:41 am
Well, this makes sense. The article goes on to say:
I think we may have a winner. From AIRS/AMSU/HSB Version 5 Modification of Algorithm to Account for Increased NeDT in AMSU Channel 4 (emphasis in original).
ɳʊ says:
June 1, 2010 at 5:17 am
You can express an anomaly around any value. I find it most useful to express the anomaly around the mean of the actual values, so that we can see the changes in the proper scale.
w.
AnonyMoose says:
June 1, 2010 at 5:24 am
One is using monthly data, one is using daily.
stevengoddard says:
June 1, 2010 at 6:42 am
Possible, but the lack of the reduction in the anomalous swing in 2008 and 2009 argues against it. I think it is the introduction of the new algorith (see above).
For my 2 pence worth I would guess that Tenuc is on the right lines pointing to ocean current changes. Tsonis showed a chaotic interference effect in which when a certain phase relationship is reached between major ocean oscillatory systems such as PDO and AMO, this triggers a step change in pcean current pattern leading to a climate shift, one way or another.
If Tsonis is right, this is a hugely significant insight into climate temporal pattern – such a shift, which may have taken place in 2007, should be called a Tsonis shift or transition.
At 2007 the Arctic ice minimum dropped and the max rose. Since then the min shows a suggestive increase while the max holds steady. If this pattern continues, and a climate cooling takes hold, this would strengthen evidence of a “Tsonis transition”.