"The Hockey Stick is broken.  Michael Mann refuses to release his code & data."
Common Arguments from Skeptics
From Logical Science


        The "Hockey Stick is broken" argument comes from climateaudit.org which is ran by Steve McKitrick and a others.    As a little background,  McKitrick is an economist and his partner McIntyre works in the mining industry.  They are commonly referred to as "MM".  They've tried and failed to get papers published at the scientific journal Nature.  However, they did manage to get a highly publicized paper published via the American Geophysical Union which criticized the hockey stick and claimed it was full of errors.  That in itself is not definitive as the editors of the AGU review several papers a day.  Bad papers make it into even the best of journals which is why reproducibility and assessment reports are so important.  Peer review, in any journal, is only a first filter.  And not all first filters are built the same.  The Hockey stick has been reproduced by multiple researchers.  The AGU, which published McKitrick's and McIntyre's first paper, subsequently published a paper that described McKitrick's and McIntyre's claims as "unfounded".  The ballyhoo surrounding the hockey stick has been inflamed by claims from numerous people that Mann "faked' his data.1,2,3   So began the hockeystick controversy.  Mann's data is available via Nature and his personal server at the University of Virginia.  Therefore claims of Mann hiding and covering up fraudulent code and data are unfounded.  The following image is a comparison of Mann's original temperature reconstruction and Wahl's attempt to see if the hockey stick was legitimate or not:


Wahl and Amman Reproduce the Hockey Stick
NCAR: media advisory

As you can see Mann & Wahl's reconstruction line up very well.  The National Center for Atmospheric Research subsequently released this media advisory:

[Wahl & Ammann] 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 [hockey stick] climate reconstruction toward a hockey stick shape. Ammann and Wahl conclude that the highly publicized criticisms of the MBH [hockey stick] 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.

        MBH stands for Mann, Bradley, and Hughes which are the authors of the first hockey stick paper that has been attacked so intensely.  Standing papers at the American Geophysical Union, American Meteorological Society, Nature, Science, the National Academy of Sciences, and the IPCC third assessment report all defend Mann's hockey stick.  The IPCC has been in turn endorsed by the National Academies of 18 different countries.  Therefore claims that Mann "faked his data" are simply unfounded.  Claims of an extremely low confidence in the hockey stick are also refuted by the National Academy of Sciences.  While the confidence level does shrink as you go back in time, the National Academy of Sciences has a "very strong" confidence in the hockey stick up to 400 years ago.  This is the strongest endorsement of the hockeystick that is possible within the scientific community.  A more detailed analysis can be heard in an audio recording of the National Academy of Sciences' press briefing.  Despite all of this McIntyre continues to insist the hockey stick is broken in numerous blog entires.  1, 2, 3  McIntyre has not been able to get another paper published on the matter.






Original Paper
Reproducability of the Hockey Stick
Articles critical of McKitrick's (and others) claims:



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