The Final Rebutal of Mann's Hockey Stick

[westwall]

I've been sitting on this awhile to see how things shook out. It looks like the end is nigh though for poor Mr. Mann and his silly little hockey stick. Good riddance too! The paper linked through WUWT is set to be published in the next volumne of the Annals of Applied
Statistics.

A brief review here...

"This paper is a direct and serious rebuttal to the proxy reconstructions of Mann. It seems watertight on the surface, because instead of trying to attack the proxy data quality issues, they assumed the proxy data was accurate for their purpose, then created a bayesian backcast method. Then, using the proxy data, they demonstrate it fails to reproduce the sharp 20th century uptick."

http://wmbriggs.com/blog/?p=2773

The whole enchilada is here.

Watts Up With That?

 

[IanC]

Looks like Ed and OR don't like statistics when it makes their favourite scientists look stupid.

 

[Old Rocks]

Hardly final, since there are nearly twenty other studies that confirm the basic shape of the graph.

 

[westwall]

Hardly final, since there are nearly twenty other studies that confirm the basic shape of the graph.

Not from a statistical standpoint. It has failed evey statistical test run on it so far. From a methodology stanpoint it is a complete and utter failure. Even the people who Mann claimed gave it the green light said they didn't. He lied about what they said...not too surprising coming from a serial prevaricator.

The only way that the stick was found to work was when a SINGLE tree from the grove was used. The one tree was found to fairly accurately match Mann's graph.

 

[konradv]

When you have only one victory, I guess you have to keep trumpeting it, even after it's become old news!

 

[Old Rocks]

Hardly final, since there are nearly twenty other studies that confirm the basic shape of the graph.

Not from a statistical standpoint. It has failed evey statistical test run on it so far. From a methodology stanpoint it is a complete and utter failure. Even the people who Mann claimed gave it the green light said they didn't. He lied about what they said...not too surprising coming from a serial prevaricator.

The only way that the stick was found to work was when a SINGLE tree from the grove was used. The one tree was found to fairly accurately match Mann's graph.

Now that is a complete lie. But the kind of thing that you are good at, Walleyes.

Some of the leading scientists at the NAS did not like Mann's statistical methods, either. But when they used their own methods, the resultant graph was pretty much the same.
Seems that there are about as many statistical methods as there are statiticians.

The Hockey Stick Controversy: New Analysis Reproduces Graph of Late 20th Century Temperature Rise - Media Advisory

Media Advisory: The Hockey Stick Controversy
New Analysis Reproduces Graph of Late 20th Century Temperature Rise
May 11, 2005

BOULDER—Caspar Ammann, a paleoclimatologist at the National Center for Atmospheric Research (NCAR), is available to comment on the so-called hockey stick controversy discussed by Stephen McIntyre and Ross McKitrick today at the National Press Club in Washington, D.C. The hockey stick refers to the shape of a frequently cited graph of global mean temperature that shows a rapid rise between 1900 and 2000 after 900 years of relative stability. The graph first appeared in a research paper by Michael Mann, Raymond Bradley, and Malcolm Hughes published in the journal Nature in 1998.

Ammann and Eugene Wahl of Alfred University have analyzed the Mann-Bradley-Hughes (MBH) climate field reconstruction and reproduced the MBH results using their own computer code. They found the MBH method is robust even when numerous modifications are employed. Their results appear in two new research papers submitted for review to the journals Geophysical Research Letters and Climatic Change. The authors invite researchers and others to use the code for their own evaluation of the method.

Ammann and Wahl’s findings contradict an assertion by McIntyre and McKitrick that 15th century global temperatures rival those of the late 20th century and therefore make the hockey stick-shaped graph inaccurate. They also dispute McIntyre and McKitrick’s alleged identification of a fundamental flaw that would significantly bias the MBH climate reconstruction toward a hockey stick shape. Ammann and Wahl conclude that the highly publicized criticisms of the MBH graph are unfounded. They first presented their detailed analyses at the American Geophysical Union’s Fall Meeting in San Francisco last December and at the American Association of Geographers Annual Meeting in Denver this year.

 

[westwall]

Here is a nice scientifically broad review of all of the problems with Manns hockey stick. I suggest you read the whole thing. Below that is a review of why Bristlecone Pines are not a very good data source for temperature proxies. And below that is a review published by MIT that shows Manns computer program was more than just bad it was junk science personified. That is highlighted in red.

So, you see, the hockey stick is crap. Started off as crap and will allways be crap.



Bristlecone Pine Trees grow in the dry boarder regions of California and Utah at high elevations. The major advantages of using this tree in the temperature reconstruction is that it is possible to go back 2000 year using living trees and they are easily accessible. You don't need to dive down into a bog to get old tree logs. Another advantage if you want to erase historical climate variations and create a "global warming smoking gun", as in this case, is that temperature reconstruction from these trees are almost useless.

This is because the trees live in a dry region, they are very susceptible to CO2 fertilization and the CO2 drought resistance effect. Temperature only play a minor role and at high temperatures it is also susceptible to drought which reduces growth. Therefore the temperature growth relation can in fact can be reversed. The trees respond positive to higher CO2 levels, humidity levels and sunshine but not to temperature. In other words, temperature reconstruction which in large part is based on this tree is perfect if you want to erase The Medieval Warm Period and The Little Ice Age.

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!
The Hockey Stick: A New Low in Climate Science

http://www.global-warming-and-the-climate.com/mann's-hockey-stick-climate-graph.htm

http://www.technologyreview.com/energy/13830/