By Steven Goddard
[see important addendum added to end of article ~ ctm]
[Note: The title and conclusion are wrong due to bias in the start/end point of the graph, the mistake was noted by Steven immediately after publication, and listed below as an addendum. I had never seen the article until after the correction was applied due to time difference in AU. My apologies to readers. I’ll leave it up (note altered title) as an example of what not to do when graphing trends, to illustrate that trends are very often slaves to endpoints. – Anthony]
JAXA Arctic Ice measurement just had its 8th birthday. They have been measuring Arctic ice extent since late June, 2002.
http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm
We normally see year over year ice graphs displayed in the format above, with each year overlaid on top of previous years. The graph below just shows the standard representation of a time series, with the linest() trend.
As you can see, Arctic ice extent has been increasing by nearly 50,000 km² per year. Over the eight year record, that is an increase in average ice extent of about the size of California. More proof that the Arctic is melting down – as we are constantly reminded. Spreadsheet is here.
How do we explain this? There has been more ice during winter, paralleling the record winter snow in the Northern Hemisphere. Meanwhile in the Southern Hemisphere, ice extent is at a record high for the date.
Size matters, but I’m guessing that Nobel Prize winner Al Gore didn’t share this information with his masseuse.
Addendum:
I realized after publication that this analysis is biased by the time of year which the eighth anniversary occurred. While the linest() calculation uses eight complete cycles, it would produce different slopes depending on the date of the anniversary. For instance, had the anniversary occurred in March, the trend line would be less steep and perhaps negative.
This is always a problem with graphing any cyclical trend, but the short length of the record (8 years) makes it more problematic than what would be seen in a 30 year record.
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R. Gates says:
July 2, 2010 at 2:31 pm
Steve,
This article should be retracted, and I think you know it.
Why should it be? Where’s your ‘scientific data’ that empirically reveals that CO2 causes so-called ‘global warming?’
If CO2 were any kind of agent for ‘CAGW,’ then why –in the name of all that is good and proper– has it NOT caused all the ice to melt?
The polar regions ice have CO2 trapped within their frozen matrix, and heavens, there’s that virtually ‘flooded’ layer of air hanging just above the ice, which SHOULD make the CO2 DOUBLY effective!!!
But it’s not …
One would have thought that by now –what with all that Sunshine and CO2– that the ice would have melted, have become steaming hot, creating a veritable steaming expanse in the process!!!
But it’s not. WHY NOT?!?!!?
Oh, sure, now you post it!…..lol
Achab says:
July 2, 2010 at 3:14 pm
Given that this post is admittedly wrong it should be promptly retracted and let professionals do the job.
I know what global warming professionals will do: they will turn it into an alarming situation that needs grant money, taxation, and a guilt trip laid on everyone, to fix.
Achab says:
July 2, 2010 at 3:14 pm
“Given that this post is admittedly wrong it should be promptly retracted and let professionals do the job.”
Sis, this is called a learning opportunity. You can chose to ignore the post if you wish, or you can take from it the “lesson” given. Here is a great example of how easy it is to skew the perspective of cyclic events. Why take it down? As our friend Toby said, “….a linear trend fitted to a cyclical function is mathematically dubious.”
Can you think of any other “cyclical functions” related to climatology? Can you see how easy it is to skew the perspective of such functions? Can you see how it relates to the overall climate discussion?
Let’s not forget the other mistakes at GISS: Sep/Oct 2008, and 1934/1998(a mistake which has evaporated over time somehow). This is a minor point being argued over. It seems some on one side of this issue are desperate to find something wrong with the other so they can feel glee. They haven’t had anything to feel gleeful about in a long time.
They should spend more time thinking about ClimateGate so that they can re-orient their heads to reality. Global warming has them living in an imagined world, a Matrix.
Steven and Anthony,
I applaud you both on good honest science that any mistakes are corrected and everyone knows that an HONEST error occurred.
u.k.(us) says:
July 2, 2010 at 4:22 pm
I’ll say it again, EVERYBODY SLOW DOWN.
Speed won’t win this “war”, facts will.
The dogma is so ingrained, it will take patience, and time.
A change is coming in November, but will things change ??
Plus ça change.
Same as it ever was.
Same ol’ same ol’.
The more things change, the more they remain the same …
Thank you, Steve! This is the way scholarly and scientific discourse should be conducted. The inevitable mistakes should be corrected as soon as practical, in the same forum where they appeared, with reasons for the correction. Lo, and behold–that’s exactly what happened here! Thanks, WUWT!
stevengoddard says:
July 2, 2010 at 5:41 pm
“This gives me a great idea for an article.”
It should. It is a small wonder why some of our warmists friends want this post deleted. They recognize the signature. Now where was that where I saw a sine wave with a wrongly applied linear trend? How many places have I seen that?
Steve, I know this was inadvertent, but it is beautiful. You should show Steve Mc. this “trick”and do a few Tamino studies with him. (You’ve already covered Hansen, Jones isn’t relevant anymore and even Mann doesn’t like his graph, now.) 🙂
It’s always Marcia, Marcia
Exactly! And the hot temperatures in the interior of Alaska have been pulling cold foggy air into Barrow, keeping temperatures well below normal this summer and slowing the ice melt down.
stevengoddard says:
July 2, 2010 at 5:41 pm
wayne
My error is much less egregious than Hansen, who chose a starting point at the bottom of one leg of a half cycle in 1979 to calculate his advertised trend of 1.7C / century.
http://data.giss.nasa.gov/gistemp/graphs/Fig.D.lrg.gif
The full cycle trend for GISS is actually closer to 0.6C/century….
________________________________________________________________
And that was based on Hansen’s graph after he “corrected” it several times!
Blink graph: http://i31.tinypic.com/2149sg0.gif
Raw vs adjusted graph: http://i26.tinypic.com/2bux35.jpg
With out Hansen’s ADDing a positive correction for UHI you are closer to perhaps negative? 0.1C/century from 1880 to 1980
And of course that is looking at the data without considering the error
See: http://strata-sphere.com/blog/index.php/archives/11420
More importantly, is the Jaxa graph swinging right now that Hudson Bay has melted out like Steve said it would? Good call perhaps?
I’m on the opposite side of the spectrum to Steve but at least he puts his money where his mouth is! I still think sub 5M though.
Andy
stevengoddard says:
July 2, 2010 at 5:41 pm
wayne
My error is much less egregious than Hansen, who chose a starting point at the bottom of one leg of a half cycle in 1979 to calculate his advertised trend of 1.7C / century.
http://data.giss.nasa.gov/gistemp/graphs/Fig.D.lrg.gif
The full cycle trend for GISS is actually closer to 0.6C/century.
This gives me a great idea for an article.
Only thing I see you did is not putting “Trend of June 2002 to July 2010” or “Regression of June 2002 to July 2010” in the title of the chart. I could see that, you said that in the text, but you have to know all about trend lines to see that, some apparently can’t.
On cyclical data you will always have a minimum and maximum as the endpoints change that following the waves in the data with the trend’s cyclical magnitude dependent on the number of cycles in the regression, even when you make sure you do not have partial cycles. If you then plot the regression’s “a” of “ax” you will get a near sine form in this case.
Yes, on Hansen, if I remember right his big flaw was he tacked on the word “trend” and then proceeded to attach significance to the data and project predictions into the future, in so many words. A regression, of any type, is but a statement of minimum variance of historic data, no more, however, a regression with attached statistics of significance and extrapolation into the future is what can get you in trouble, and as VS pointed out (I’m still thanking him), sometimes it will always gets you in trouble! 🙂
( I know you know that, just said for others that might not know a very, very important fact about charts, regressions, trends, and statistics, you better know the differences, some get confused. )
PJP: July 2, 2010 at 2:07 pm says:
“Are you absolutely certain that trend line is correct?
Just eyeballing it, it doesn’t look right …”
There you have it. Eyeballing is always the correct thing to do.
If the trend is not blindingly obvious to the eye, there isn’t a trend.
I’ll always trust my eye ahead of some fancy mathematical (and wrong) calculations.
Remember those amazing spaghetti gaphs of tree ring data where somebody got a trend out of it? Absolute rubbish of course.
R. Gates says:
July 2, 2010 at 2:31 pm
Steve,
This article should be retracted, and I think you know it.
Not to embarrass you but your true color are now showing!
I thought scientists were supposed to publically correct themselves and never remove it from the public records? Are you that much against proper science?
RoyFOMR says:
July 2, 2010 at 5:18 pm
“thanks Gav. I owe you one! But to Dhogoza, certainty!”
Me too! Especially The Mad Dhog!
R. Gates says:
July 2, 2010 at 2:31 pm
Steve,
“This article should be retracted, and I think you know it.”
What? And spoil all your fun?
stevengoddard says:
July 2, 2010 at 5:21 pm
EFS_Junior
Now it is time for you retraction. You wrote:
It’s wrong, he knows it’s wrong, yet no retraction of this extremely biased analysis, and no change to the post titled;
“Arctic Ice INCREASING By 50,000 km2 Per Year (if you start with a trough and end with a grest, oops, my bad, I don’t know what I’m doing)”
Everything you said was incorrect. I wrote up the addendum within five minutes of the article being published. The JAXA data does not start at the low as you claimed, it starts at the midpoint and ends at the midpoint eight years later.
You have posted rather large amounts of misinformation on WUWT over the last few days. Now let’s hear your retraction.
____________________________________________________________
You really don’t get do you.
You data started with the 6-month TROUGH and ended with the 6-month CREST.
You have to start with a full creat-tofull crest or a full trough-to full trough.
To define full crests or full troughs you need to do a time domain analysis to find the zero upcrossing and zero downcrossing points, which is defiined as the mean of the number of full cycles of interest.
It’s quite obvious you didn’t know what you were doing then, as it quite obvious that you still don’t know what you are doing now.
These words are from a SME in ocean wave analyses ()frequency and time domains).
Also known as, been there, done that (like 25 years ago).
Dennis Gaskill says:
July 2, 2010 at 4:03 pm
The biggest problem with the Sea Ice Extent Discussion, is that 8 years of data is TOO
SMALL of a sample, to allow ANY conclusions to be determined.
Who’s looking for conclusions?
The data is the data, it’s all we’ve got (sorry Joe). Now, trying to discern from the data what the climate system is doing, that’s a different matter. One is asking the data questions, the other is saying what the data means, those are two very different operations, and the later is rarely correct in a chaotic and cyclical system, best to bet against it.
About the time you can discern what looks like a secular trend the other part of the cycle kicks in. That is how so many lose so much in the stock market (and a few who know it’s cyclical make a fortune). In fact, that’s much the way I view the climate. If it’s been hot, get ready for a cold front. If it’s been dry, watch for the time to bring in the cushions outside, and this happens on all time scales, usually right, rarely wrong. Even what we view as a secular trend on our short (few decade) viewpoint is most likely just another longer multi-decadal wave that is about to turn. Just look at the temperature record for the last 100,000 years or so and that is the only ‘conclusion’ you can get!
Jimmy Haigh says at 7:44 pm…
LOL! You’ve got R. Gates’ number.
James Sexton says:
July 2, 2010 at 6:17 pm
“You should show Steve Mc. this “trick”and do a few Tamino studies with him.”
Dang the Freud! I meant tree ring studies!
stevengoddard says:
July 2, 2010 at 5:12 pm
EFS_Junior
Why on earth would you waste all of your many, many precious talents writing comments on blog site which you don’t respect?
Clearly your skills are far beyond what we deserve, and you should move on to work with well respected scientists (like Mann) devoted to rewriting history for highly respected organisations like the IPCC. We don’t deserve you, and I am sure everyone would understand if you moved on to bigger and better things.
Though I have to admit that I would miss your paranoid rantings.
____________________________________________________________
Dude, no comment necessary, as you continued logical fallacies and ad hominem attacks, make my day.
Thank you.
EFS_Junior
You are truly a legend in your own mind. Now critique Hansen’s widely published 1.7C temperature trend – which starts in 1979.
http://data.giss.nasa.gov/gistemp/graphs/Fig.A2.lrg.gif
Steve (or maybe Willis), you know, that brings up a long term question I’ve had, how do you de-cycle a sine form sequence of data while minimizing the sum of the variances and maintaining daily data points. I’ve often looked at this up and down of temperatures or sea-ice and thought, I’d like to see this if the seasonal sine imprint were properly remove from the sequence but have never come across the algorithm. Have you?
Wait, maybe it’s as easy as best fiting (least squares) of a sine wave of best fit magnitude and phase parameters using a solver to the data then merely subtracting the daily sine values from the data. I think that’s it. Have you ever tried this? I am, right now on this JAXA data.
Excuse me for asking, but, I am waiting for CO2 to harm me.
To tell you the truth, I thought it might be exciting, now it’s just boring.