Guest post by Steven Goddard
In my May 1st piece, Dr. Walt Meier at NSIDC hypothesized that differences in algorithm between NSIDC and NANSEN (NORSEX) were causing the gap between the NSIDC interpretation of normal and the NANSEN interpretation of normal, as seen below. They use different baseline periods which introduces some difference – but the discrepancy should go the other way due to the fact that the NANSEN base period (1979-2007) includes more low ice extent years from the current decade.
So I tried an experiment to test this out, where I overlaid NANSEN on top of NSIDC for the entire winter – and found that they are nearly identical. This would tend to discount the theory that differences in the algorithm are to blame. It appears from this more likely that one or the other has an error in their historical database which is affecting the interpretation of “normal.” Dr. Meier has stated that he is confident about the accuracy of the NSIDC database.
Using a third reference point, I tried another experiment comparing NSIDC (blue) vs. AMSR-E (red) and did see something interesting. Starting in late March, NSIDC (in blue) began to show more ice than AMSR-E (in red) – which uses a different satellite.
Last winter, the SSM/I satellite used by both NSIDC and NANSEN began to degrade, as reported by NSIDC and WUWT (of course.)
The degradation caused the ice extent to appear lower than AMSR-E, but now the problem seems to be going the other way – with SSM/I showing more ice than AMSR-E. What does it all mean? Given that NSIDC and NANSEN seem identical this year, I don’t think this explains the discrepancy in their baseline. It does appear that there is still an error in the SSM/I data however.
UIUC has quit posting their SSM/I images because the quality has become so bad.
February 25, 2009 – The SSMI images for many days in 2009 were bad enough that we removed them from this comparison display (see note below and the NSIDC website). There is enough interest in these side-by-side comparison images that we will try to replace them with corresponding images from the AMSR-E sensor in the coming weeks.
Regarding the comparison of NSIDC, Nansen and JAXA current values are ~13.8, 13.1 and 13.0 respectively which reflects the differences that have existed through the winter. That is Nansen and JAXA are very close and NSIDC somewhat higher. The real outlier is DMI which has a much smaller range, currently ~10.3.
Phil,
There is a fixed Y-offset between NSIDC extent and NANSEN extent. That has been normalized in the graphs above. Since you can’t make direct numerical comparisons between them, the point of this exercise is to show the relative deviations (or lack of them) over time.
Frederick Michael 21 36
You are right. Using the data from the JAXA site gives an average 2009 April extent of 13.58 m sq km compared with average 2003 April extent of 13.65 m sq km.
Frederick Michael (20:09:19) :
… The weather forecast for Barrow, AK is NOT GOOD for melting sea ice.
http://www.weather.com/outlook/health/skin/tenday/USAK0025?from=36hr_topnav_skin
and, you’re welcome for the cute beach scene at the top. Really makes you think of Barrow, eh?
Yes, it does look a bit nippy: http://www.gi.alaska.edu/snowice/sea-lake-ice/barrow_webcam.html
and the UAF sensors show that the ice is still 1.36m thick off Barrow: http://www.gi.alaska.edu/snowice/sea-lake-ice/Brw09/
Jeff ID:
Your work http://noconsensus.wordpress.com/2009/05/03/global-sea-ice-nears-record-high/ is very fine indeed, thankyou.
I have used it on http://www.klimadebat.dk
K.R. Frank
Jeff, the precise URL :
http://www.klimadebat.dk/forum/global-warming-alarmists-out-in-cold-d12-e929.php#post_11944
Oh! No sunspots today.
So much for the Watts Effect.
I guess it only works for Gore.
Well, NSIDC’s May update essentially shows April trend flat since 1989. But then it did last year too, before the “1st year ice” phenom hit in summer. I’ve still got my money on Arctic minimum being right around the 2005 line, which would still be Good News Going in the Right Direction (unless you’re a panic-monger, of course).
I find it interesting they are now claiming +/- 2 standard deviation as their claimed “natural deviation” standard. Have they done that before? The suspicious side of me is wondering if they are doing so both to avoid noting that the current line is actually within 1 standard deviation, and also to give themselves more room on the upside to still claim “natural deviation” if/when the current trend line crosses above the long-term trend line.
Is there an error in the first graph? The NANSAN data uses the ice area up to ’07 so it should have a lower mean. But the 1st graph shows NSIDC having a lower mean.
Forgive me, but how can we accept the data from the NSIDC as uncorrupted and reliable? Consider these gems from their website:
“Arctic sea ice has declined dramatically over at least the past thirty years, with the most extreme decline seen in the summer melt season. ”
Their data do not support this assertion. I see no visible trend line from 79 – 97. The decline was certainly not ‘dramatic’. We do not have complete records of arctic sea ice prior, so we cannot comment on what happened earlier more than 30 years ago; doing so is misleading. There was a substantial negative trend 1998 through 2008; with substantial recovery in the past year. From the data, that’s pretty much what we can say.
Here’s another one: “For sea ice extent data, the standard deviation is computed for each day of the year from the extent on that day over the 22 years of the average climatology, 1979-2000.” This is akin to saying, lets take only men taller than 5’8″ and shorter than 6’0″, and compute the mean and stnd deviation using this pool. As a result, anyone 5’7″ or 6’1″ will almost surely be two standard deviations outside the norm. But the chosen pool is entirely arbitrary and the standard deviation is meaningless.
How can they expect me to accept the impartiality of the data or algorithms when their statistical technique is so poor and their bias so strong? Is the University of Colorado really this feeble?
I wonder what alarmists think of 2009 divergence from 2008?
http://arctic-roos.org/observations/satellite-data/sea-ice/ice-area-and-extent-in-arctic
Or do the even care what the graphs show?
Steven Kopit: Is the University of Colorado really this feeble?
That could be it. It could also be that your interpretation is lacking. Is that an option for you?
The two datasets, NSIDC and AMSR-E for ice extent are very close, show you how close in a moment.
In a recent email I said
“Making a rash prediction based on known amsr-e daily data so far this
month, April, the month northern extent data you will be producing will
be 14.55 +-1%”
And I see the published figure is 14.58
I’ve not updated AMSR-E data here yet, maybe it is closer.
Here is a very wide plot of the two datasets as monthly plotted on top of each other. Making that clear, raw AMSR-E daily data and NSIDC monthly compensated by a fiddle factor for each month.
The compensation could be improved but this is good enough for now.
http://www.gpsl.net/climate/data/sea_ice/northern-ice-extent-combined-raw-2009-04-28a.png
13.58
—- = 14.55 or of course reversed
0.933
To 3 dec places these are the monthly compensation figures for all the dataset, is consistent over the overlap years. The graph assumes this is so over all time for the longer dataset. Valid? No way of knowing or do you have a way of cross checking?
Nov 0.932
Dec 0.922
Jan 0.942
Feb 0.939
Mar 0.925
Apr 0.933
May 0.926
Jun 0.926
Jul 0.933
Aug 0.990
Sep 1.000
Oct 0.878
Meier has said in reply to an email that the dataset match problem is for ice area, extent is not the problem. This makes sense.
Geo (05:29:43)
Good points you make there. I noticed the same thing on the NSIDC May 4 posting.
1-They seem to have toned down the ‘spin’ in the way they wrote up the report.
2-Mr. Goddard might be having an impact as they included a graph with a ±2 StdDev shaded area, similar to the ±1 StdDev that’s been shown at NANSEN. And the skeptic in me also wonders why ±2 StdDev instead of ±1 StdDev? Is it to give themselves some breathing room in case the ice extent goes much above the 1979-2000 mean?
3-While the April Extent graph for the period still shows a downward trend, I think it’s noteworthy that it also shows that this year’s level is the highest in seven years, as is apparent in the AMSR-E graph.
Now all that remains is to see what the ice looks like in September; whatever happens between now and then will be the result of storms and variations in wind and ocean currents moving the melting ice about.
You know that graph is the inverse of the integral of the heat flux into the Arctic?
Because this corresponds to the 95% confidence interval which has been standard in statistical analysis for a very, very long time.
Steven Kopits (05:37:36) :
Forgive me, but how can we accept the data from the NSIDC as uncorrupted and reliable?
Dr. Meier’s comments reflect his observation a steady decline in arctic sea ice for quite a while and he isn’t yet convinced that the recent recovery will reverse the trend. I don’t recall him ever speculating on the cause of the trend, so he shouldn’t get lumped in with the CO2 crazies. His data passes every check I know of for being legit and his recent mea culpa was textbook perfect.
Real data has warts — sometimes embarrassing ones. Phony data is just too perfect. Real data from multiple sources is easy to check and thus holds to a higher standard.
You can trust the sports scores in the NY Times.
E.M.Smith (19:40:38) :
Just for grins, I did a Google search of “2009 record snow” and got:
Results 1 – 10 of about 11,000,000 for 2009 record snow. (0.24 seconds)
Well, you did it without the quotes, not as you indicate here. That means any article with any of the words, which obviously give you 11 million hits. But if you try it as shown, the number of hits are considerably less:
Try this instead
Results 1 – 10 of 10 for “record snow 2009”. (0.39 seconds)
Which doesn’t prove anything, except you have to do such “Google surveys” carefully….
“dhogaza (08:20:50) :
And the skeptic in me also wonders why ±2 StdDev instead of ±1 StdDev?
Because this corresponds to the 95% confidence interval which has been standard in statistical analysis for a very, very long time.”
Agreed; but there might be a reason to choose another:
1) If you travel to some place and wonder if you have enough gas.
2) If you wonder about surviving an operation.
Answer: 1) by car 1 SD; by Skyhawk 100% 2) for cancer: maybe less; to remove a mole: 3 SD
It would be interesting if someone in contact with Dr. Walt M. would ask for a someone more rigorous comparison of different years of ice thickness. Tho I recognize that, say, 3rd year ice in a multi-year warming trend might only be on average as thick as 2nd year ice in a multi-year cooling trend.
Still, something like “2nd year is usually ~100% thicker than 1st year ice. 3rd year ice is usually ~50% thicker than 2nd year ice. 4th year ice is ~25% thicker than 3rd year ice. 5th year and greater is pretty much indistinguisable.”
Something like that would be useful to know.
“Still, something like “2nd year is usually ~100% thicker than 1st year ice. 3rd year ice is usually ~50% thicker than 2nd year ice. 4th year ice is ~25% thicker than 3rd year ice. 5th year and greater is pretty much indistinguisable.”
Something like that would be useful to know”
The ice is floating and moves… there is no permanent ice, it just moves on out of the Arctic and melts. So it is more a matter of ice which manages to be located in lucky places and gets to live longer.
(twiddle)
Here we go, have fun
http://cersat.ifremer.fr/news/scientific_results/global_mapping_of_arctic_sea_ice_drift_a_unique_database
I have a question: Whats the maintenance record of the Mauna Loa CO2 concentratometer and what are the decay rates of the components in it? If it can be shown the supposed CO2 curve is really reflective of the decay in the value of a given electronic component in it, that would be a huge blow to the alarmists.
Mike Lorrey: These articles and their comments have links and information about the Mauna Loa operation:
http://cdiac.ornl.gov/trends/co2/sio-mlo.html
http://wattsupwiththat.com/2008/08/04/mauna-loa-co2-january-to-july-trend-goes-negative-first-time-in-history/
http://wattsupwiththat.com/2008/08/07/mauna-loa-to-improve-the-co2-data/
Anthony,
It appears NSIDC started time stamping their arctic sea ice extent figures. I believe that has been a topic of concern on WUWT before. Sorry if this is old news!
REPLY: Nope, you are the first to notice. I suppose it would be too much for them to credit WUWT for suggesting this on more than one occassion, but it is nice to know they read. – Anthony