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GLOBAL WARMING BOMBSHELL: Hockeystick Broken
MIT Technology Review ^ | 15 October 2004 | Richard Muller

Posted on 01/13/2005 4:20:13 PM PST by neverdem

A prime piece of evidence linking human activity to climate change turns out to be an artifact of poor mathematics.

Progress in science is sometimes made by great discoveries. But science also advances when we learn that something we believed to be true isn't. When solving a jigsaw puzzle, the solution can sometimes be stymied by the fact that a wrong piece has been wedged in a key place.

In the scientific and political debate over global warming, the latest wrong piece may be the "hockey stick," the famous plot (prominently displayed by the IPCC report, 2001), published by University of Massachusetts geoscientist Michael Mann and colleagues. This plot purports to show that we are now experiencing the warmest climate in a millennium, and that the earth, after remaining cool for centuries during the medieval era, suddenly began to heat up about 100 years ago--just at the time that the burning of coal and oil led to an increase in atmospheric levels of carbon dioxide.

I talked about this at length in my December 2003 column. Unfortunately, discussion of this plot has been so polluted by political and activist frenzy that it is hard to dig into it to reach the science. My earlier column was largely a plea to let science proceed unmolested. Unfortunately, the very importance of the issue has made careful science difficult to pursue.

But now a shock: independent Canadian scientists Stephen McIntyre and Ross McKitrick have uncovered a fundamental mathematical flaw in the computer program that was used to produce the hockey stick. In his original publications of the stick, Mann purported to use a standard method known as principal component analysis, or PCA, to find the dominant features in a set of more than 70 different climate records.

But it wasn't so. McIntyre and McKitrick obtained part of the program that Mann used, and they found serious problems. Not only does the program not do conventional PCA, but also it handles data normalization in a way that can only be described as mistaken.

Now comes the real shocker. This improper normalization procedure tends to emphasize any data that do have the hockey stick shape, and to suppress all data that do not. To demonstrate this effect, McIntyre and McKitrick created some meaningless test data that had, on average, no trends. This method of generating random data is called "Monte Carlo" analysis, after the famous casino, and it is widely used in statistical analysis to test procedures. When McIntyre and McKitrick fed these random data into the Mann procedure, out popped a hockey stick shape!

That discovery hit me like a bombshell, and I suspect it is having the same effect on many others. Suddenly the hockey stick, the poster-child of the global warming community, turns out to be an artifact of poor mathematics. How could it happen? What is going on? Let me digress into a short technical discussion of how this incredible error took place.

In PCA and similar techniques, each of the (in this case, typically 70) different data sets have their averages subtracted (so they have a mean of zero), and then are multiplied by a number to make their average around that mean to be equal to one; in technical jargon, we say that each data set is normalized to zero mean and unit variance. In standard PCA, each data set is normalized over its complete data period; for the global climate data that Mann used to create his hockey stick graph, this was the interval 1400-1980. But the computer program Mann used did not do that. Instead, it forced each data set to have zero mean for the time period 1902-1980, and to match the historical records for this interval. This is the time when the historical temperature is well known, so this procedure does guarantee the most accurate temperature scale. But it completely screws up PCA. PCA is mostly concerned with the data sets that have high variance, and the Mann normalization procedure tends to give very high variance to any data set with a hockey stick shape. (Such data sets have zero mean only over the 1902-1980 period, not over the longer 1400-1980 period.)

The net result: the "principal component" will have a hockey stick shape even if most of the data do not.

McIntyre and McKitrick sent their detailed analysis to Nature magazine for publication, and it was extensively refereed. But their paper was finally rejected. In frustration, McIntyre and McKitrick put the entire record of their submission and the referee reports on a Web page for all to see. If you look, you'll see that McIntyre and McKitrick have found numerous other problems with the Mann analysis. I emphasize the bug in their PCA program simply because it is so blatant and so easy to understand. Apparently, Mann and his colleagues never tested their program with the standard Monte Carlo approach, or they would have discovered the error themselves. Other and different criticisms of the hockey stick are emerging (see, for example, the paper by Hans von Storch and colleagues in the September 30 issue of Science).

Some people may complain that McIntyre and McKitrick did not publish their results in a refereed journal. That is true--but not for lack of trying. Moreover, the paper was refereed--and even better, the referee reports are there for us to read. McIntyre and McKitrick's only failure was in not convincing Nature that the paper was important enough to publish.

How does this bombshell affect what we think about global warming?

It certainly does not negate the threat of a long-term global temperature increase. In fact, McIntyre and McKitrick are careful to point out that it is hard to draw conclusions from these data, even with their corrections. Did medieval global warming take place? Last month the consensus was that it did not; now the correct answer is that nobody really knows. Uncovering errors in the Mann analysis doesn't settle the debate; it just reopens it. We now know less about the history of climate, and its natural fluctuations over century-scale time frames, than we thought we knew.

If you are concerned about global warming (as I am) and think that human-created carbon dioxide may contribute (as I do), then you still should agree that we are much better off having broken the hockey stick. Misinformation can do real harm, because it distorts predictions. Suppose, for example, that future measurements in the years 2005-2015 show a clear and distinct global cooling trend. (It could happen.) If we mistakenly took the hockey stick seriously--that is, if we believed that natural fluctuations in climate are small--then we might conclude (mistakenly) that the cooling could not be a natural occurrence. And that might lead in turn to the mistaken conclusion that global warming predictions are a lot of hooey. If, on the other hand, we reject the hockey stick, and recognize that natural fluctuations can be large, then we will not be misled by a few years of random cooling.

A phony hockey stick is more dangerous than a broken one--if we know it is broken. It is our responsibility as scientists to look at the data in an unbiased way, and draw whatever conclusions follow. When we discover a mistake, we admit it, learn from it, and perhaps discover once again the value of caution.

Richard A. Muller, a 1982 MacArthur Fellow, is a physics professor at the University of California, Berkeley, where he teaches a course called "Physics for Future Presidents." Since 1972, he has been a Jason consultant on U.S. national security.


TOPICS: Business/Economy; Canada; Culture/Society; Editorial; Foreign Affairs; Government; News/Current Events; Politics/Elections; US: District of Columbia
KEYWORDS: climatechange; globalwarming; hockeystick; horsehockey; junkscience
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1 posted on 01/13/2005 4:20:13 PM PST by neverdem
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To: neverdem

This is old news.


2 posted on 01/13/2005 4:23:24 PM PST by AndyTheBear (Disastrous social experimentation is the opiate of elitist snobs.)
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To: neverdem

Oh. "Black Eye from Broken Hockey Stick".


3 posted on 01/13/2005 4:23:28 PM PST by bitt (Why didn't they shove Dan Rather out of the door in his underwear?)
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To: neverdem

John Daly, RIP, cracked the hockey stick theory as soon as it came out.


4 posted on 01/13/2005 4:28:36 PM PST by Always Right
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To: neverdem

I have to drive my SUV a full tear to feed 5 acres of rainforest.


5 posted on 01/13/2005 4:29:41 PM PST by Cold Heart
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To: neverdem

I did not need math to tell me the global warming nonsense is, well, nonsense.


6 posted on 01/13/2005 4:30:56 PM PST by BJungNan (Did you call your congressmen to tell them to stop funding the ACLU? 202 224 3121)
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To: neverdem

I wonder how Noam Chomsky feels about MIT Technology review publishing this report?


7 posted on 01/13/2005 4:31:59 PM PST by Lx (If dolphins are so smart, why do they live in igloos?)
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To: neverdem

http://www.freerepublic.com/focus/f-news/1248429/posts

http://www.freerepublic.com/focus/f-news/1245759/posts

http://www.freerepublic.com/focus/f-news/1245729/posts

</hall monitor>


8 posted on 01/13/2005 4:32:20 PM PST by Yardstick
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To: AndyTheBear
look at the date. it is old news for us, but an earthshattering sea change for the technical/liberal MSM to actually cover this. Buckhead and FR have changed the media world!

note that Nature rejected the paper and it went over to a "blog" on the internet, and now is getting more and more traction with those who can no longer stomach the monolithic leftist lie. that is the classical breakout, and very similar to the way the rathergate fiasco came about.

kyoto fans will be deeply saddened (but watch them claim it is necessary anyway!)

9 posted on 01/13/2005 4:33:28 PM PST by chilepepper (The map is not the territory -- Alfred Korzybski)
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To: chilepepper
I had read the paper back when it had come out (I occasionally frequent junkscience.com and co2science.com). I hope your right about it getting traction. The global warming as science shake down has gone on long enough.
10 posted on 01/13/2005 4:38:29 PM PST by AndyTheBear (Disastrous social experimentation is the opiate of elitist snobs.)
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To: AndyTheBear; chilepepper; Yardstick; neverdem; BJungNan; Always Right
Check out this:

Meltdown : The Predictable Distortion of Global Warming by ..... and the Media ( author on Foxnews)

11 posted on 01/13/2005 4:43:25 PM PST by Ernest_at_the_Beach (A Proud member of Free Republic ~~The New Face of the Fourth Estate since 1996.)
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To: neverdem
Not only does the program not do conventional PCA, but also it handles data normalization in a way that can only be described as mistaken.

Like CBS, they liked the answer, so they didn't question the results. That is of course putting the best possible spin on it. The worst it that they did it more or less deliberately to fulfill their agenda.

While this could be simple incompetence, it sounds to me like an awfully hard mistake to make accidentally.

12 posted on 01/13/2005 4:44:00 PM PST by El Gato (Activist Judges can twist the Constitution into anything they want ... or so they think.)
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To: AndyTheBear; Yardstick

Check my link for the story. Someone else added "Hockeystick Broken". I searched the title with "match all words" and "match exact phrase" twice as well as an archive search.


13 posted on 01/13/2005 4:53:03 PM PST by neverdem (May you be in heaven a half hour before the devil knows that you're dead.)
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To: El Gato

When government funds science, science becomes a whore of government.


14 posted on 01/13/2005 4:53:05 PM PST by annalex
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To: neverdem

RE: Apparently, Mann and his colleagues never tested their program with the standard Monte Carlo approach [!!!]

That's a big boo boo. What sort of real scientist would fail to do this?

RE: Did medieval global warming take place?

Well, we know this much. Vinyards in the UK and a place in Bavaria called "Valley of the Limes." Sure it's only circumstantial evidence, but it is hard to explain away with the Medieval Warming.


15 posted on 01/13/2005 4:53:07 PM PST by GOP_1900AD (Stomping on "PC," destroying the Left, and smoking out faux "conservatives" - Take Back The GOP!)
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To: neverdem

I think you narrowed your search too much by setting it to match all words. I just copied your title into the search box and did a quick "by title" search, and it pulled up those three articles (plus yours).

But whatever the case, taint no big deal.


16 posted on 01/13/2005 5:01:13 PM PST by Yardstick
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To: Ernest_at_the_Beach

Thanks for the link.


17 posted on 01/13/2005 5:01:35 PM PST by neverdem (May you be in heaven a half hour before the devil knows that you're dead.)
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To: El Gato

LOL!


18 posted on 01/13/2005 5:02:47 PM PST by neverdem (May you be in heaven a half hour before the devil knows that you're dead.)
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To: JudyB1938; Robert A. Cook, PE; lepton; LadyDoc; jb6; tiamat; PGalt; Dianna; farmfriend; archy; ...

FReepmail me if you want on or off my health and science ping list.


19 posted on 01/13/2005 5:04:10 PM PST by neverdem (May you be in heaven a half hour before the devil knows that you're dead.)
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To: neverdem; Ernest_at_the_Beach
And for fun, read Micheal Crichton's new book, State of Fear.
20 posted on 01/13/2005 5:09:40 PM PST by no more apples (my give-a-damn's busted)
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