As I mentioned yesterday, NSIDC had an oops moment, but with the help of skeptical blogs, was notified of the problem and responded timely and appropriately. They posted this update today:
Update, April 19, 2012: The nine-day trailing average climatology on the daily data graph has been changed to a five-day trailing average, to be consistent with the five-day trailing average for the daily data.
I verified their correction for the climatology was accurate with a new overlay, combining the unaffected graph NSIDC’s Dr. Julienne Stroeve sent me from their internal server storage Tuesday night with the corrected one published on the web today:
http://nsidc.org/data/seaice_index/images/daily_images/N_stddev_timeseries.png
The extent data and the climatology now match, whereas yesterday they did not. The x-axis offset is to be expected given that we are comparing graphs with the temporal data offset due to a trailing average they implemented.
This is what the same comparison looked like yesterday, for graphs made on the same day:
So, problem solved.
Unfortunately, somebody jumped to a conclusion and has already had to issue a correction.
April19: NSIDC graph still appears wrong
now reads:
Correction : April 19 – NSIDC Graph Now Lines Up With April 16
The maxim “haste makes waste” seems appropriate.
The way NSIDC’s Dr. Walt Meier and Dr. Julienne Stroeve handled this should be an example to other agencies that don’t bother to even respond to skeptics.
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NSIDC should take the opportunity to switch to center point averaging. Given the changes this week, switch to center weight immediately.
Sorry to be completely skeptical on this, but do you really believe they would have corrected their “error” unless it wasn’t pointed out to them by skeptics? 9 times out of 10 (a number I pulled out of my arse but I bet is close) the “adjustments” favour the CAGW theory.
REPLY: If not by us, eventually it would have been caught. In this particular case, I see no nefarious motives, just simple miscommunications. The graphs match, the wiggle problem is solved, and if the extent line data is reflecting a situation where it will cross the median line, we’ll see it. – Anthony
Posted this on the previous ice blog, but I think it bears repeating now it has been superceded….
For those of you calling for NSIDC to use a 30-year average : I took the opportunity to raise this issue on Steve’s blog yesterday, and Julienne responded that they were planning to do just that later in the year.
Let’s hope that implementation goes more smoothly than this one…….
That standard deviation calculation is way, way wrong. You cannot go from 2 std down back to near average in two months. This would be like going from the bottom of the NBA to second best team in the two months. Doesn’t happen. I don’t know how they calculated that std, but I can tell you with simple visual inspection that they did the math wrong.
Ok, I have to admit it, they’ve done a good job. Well done.
Out of interest, does anyone know the longest period of sea ice volume being continually within the statistically ‘normal’ range since the Millennium? If it’s right now, maybe that’s an indication that a slow but steady recovery may be underway?
Which internet gossip blog reports the exact history and status of Watts/Goddard relationship?
It’s still going to be wrong to use what they call a ‘trailing average’, since the output of the averaging operator (1,1,1,1,1) is going to be artificially shifted ahead by half of the operator length.
An operator outputs at its centre point, not at its ends.
Its not ice, it is our knowledge of CO2 that is the issue. From Tallblokes workshop:
Sorry to dissapoint everyone, but it looks like we can all go home. We did not cause the big rise in CO2.
Steven Kopits says:
April 19, 2012 at 9:25 am
I assume they computed the the std the conventional way taking all the extents for a particular day and doing the math on it. There’s no indication the data is at all useful for short term limits as you suggest in you NBA example. To continue that analogy, a team can go from the bottom of the NBA to second best in one year.
What you are expecting would be an interesting display, perhaps you can work on generating it.
Nice shot, guys!
I can imagine what kind of tricks are applied in the statistical data analysis. Just keep an eye on those cheaters!
Works for me. Thanks Anthony and Drs. Walt and Julianne.
And a “climatology” update is coming this year. Great.
Dear Anthony,
Excuse me, but I see plenty of nefariousness in the graph.
Why else would they hide the actual data and instead post phony “confidence” intervals around a known data set. There is no estimating needed. The facts (the data) are known with 100% “confidence”. I cannot see any reason for the gray zone except to artificially (and nefariously) shrink the actual range of the actual measurements.
Are some years “outliers”? Why does the government (aka Big Brother) need to hide the actual facts? Why vanilla-ize what really happened?
Please forgive me if I hurt somebody’s feelings because I want the actual real data, that I paid through my taxes to have collected. The NSIDC is not the CIA. National security will not be jeopardized. Are the big bad gummit scientists having a pout because some lowlife upstart dared to ask for the ACTUAL DATA!!!
And what’s with the 2007 line? Why is that year the ONLY year graphed? Is there something special about 2007, something so ALARMING such that the paternalistic head-patter gummit mucky mucks need me to see that year and none of the others?
Nefarious, nefarious, nefarious.
Pretty obvious to me that Big Brother is putting out propaganda masquerading as science. Not welcome. Dirty tricksters should be shown the door.
Reblogged this on Climate Ponderings.
I will have a profound sense of relief when those lines cross.
To me it represents the Arctic ice cycle as an oscillation as opposed to a straight line to a hot hell.
It plunges an ice dagger into the heart of CAGW zombieism.
I will pop a cork when it happens.
The ’12 ice appears way more robust that ’07.
A good sign.
However, I am dismayed by the recent flurry of Global Warming “propaganda” that has been
released recently. It seems like “the last gasp” when something is dying. I hope so.
I can’t wait to tell my warmy friends when “Arctic ice is above normal”.
Regardless of which way it goes, the truth will out.
…but I’m rootin’ for the ice.
Anthony, I don’t know if you or Steve McKintyre have noticed it, but it is very unlikely indeed that the standard deviation for sea ice is correct for late March. It necks in to (eyeballed) half of its extent in early March or mid-April even though the mean is smooth across the two domains. Either there is some extremely odd climate factor that causes a crossover between two essentially independent mechanisms that are responsible for the larger variance before or after or, more reasonably, the standard deviation should be at its fattest all the way across this region. This, by the way, would keep late March in 2007 from being a 5 or 6 sigma event (which is absurd). If one smooths the sd the way it almost certainly should be, March 2007 would be a less than 3 sigma, maybe a 1 in 50 to 1 in a 100 shot (consistent with the whole year).
Oh, and if one adds in the 2007 data, there is no way in hell that the sd is right for any moderate number of sample years. An outlier like this simply bumps the sd to accommodate for few samples (and suggests if anything else a possible bimodal distribution so that the central limit theorem hasn’t yet kicked in, although outliers do happen).
So either the data for late March is “miraculously” tightly clustered compared to expectations from the time immediately before or after or there is something funky about either the data or the way it is being processed into a sigma here. At the very least, something that demands explanation in terms of climate observations over this period, where the ice melts (a tiny bit) consistently where before and after it is melting and growing much more variably.
As they say, “What’s Up With That?”_tm…;-)
rgb
NSIDC have done a good job here; listening to criticism, and fixing the problem quickly and openly in a way that we don’t see from the usual AGW suspects. As such I don’t think they deserve any rebuke.
Moving to a 30 year baseline later in the year will certainly screw up the narrative as the confidence intervals will widen and the averages will drop so that relatively low sea ice levels won’t appear anywhere near as impressive as they do with the old baseline.
Sure right … oops, we got caught.
Sumpin’ funky about the last two months.
H/t Bill Illis.
========
Regarding the 1979-2000 average, NSIDC uses it for both Arctic and Antarctic graphs. If 1982-2011 were used, current Arctic extent would probably be above the average, but Antarctic extent would probably be less above the average. I doubt it would make any difference to True Believers and, by definition, objective observers don’t care.
That NSIDC uses 2007 for Arctic reference and 2011 for Antarctic reference is inconsistent. On the one hand, 2007 is a revered year for warmistas but, on the other hand, 2007 has made every succeeding year look like one of cooling.
“Ed_B says: April 19, 2012 at 9:40 am
Its not ice, it is our knowledge of CO2 that is the issue. From Tallblokes workshop
http://www.youtube.com/watch?feature=player_embedded&v=YrI03ts–9I ”
Thanks for the HT – All I can say is WOW. Everyone needs to watch this presentation.
A government agency tried to improve their product, had some internal misscomuniction and growing pains. They then openly admitted this and promptly made corrections. How sad that this is considered so remarkable.
The maxim “haste makes waste” seems appropriate.
Dear Anthony
Unlike you to be churlish, at least Mr Goddard corrected his error and he did spot the change in the first place so credit where credit is due. 🙂
Another maxim by a great American “The only man who never makes mistakes is the man who never does anything”
Thank you for all your great work and keeping this blog alive and lively.
S
REPLY: In the original post I gave him full credit for spotting it first, but he also published first, and used a title that said “data tampering” suggesting malfeasance where there was simply a boneheaded mistake brought on by poor communications at NSIDC. He published that without having asked NSIDC a single question, that responsibility fell to me. Steve then compounded his first error by rushing out an opinion on the correction which he had to retract today.
So yes, in this case, “haste makes waste” – Anthony
The big question now is will it? wont it?
Do NOT attribute to arravice or malevolence that which may more simply explained by ignorance, stupidity or laziness. Anonomous…
However, I’d add, “Hey, a calculational mistake not immediately caught…as there are a limited number of reviewers!” (Which I think is the case here.)