I have been attempting to identify the actual data that you are all claiming Professor Mann has refused to release. I have a sketchy memory that there were data used in MBH98 that he simply did not have the right or permission to release, but I am unaware of anything else. I have been searching and there are piles of articles about Mann, but I can find nowhere the specific data you believe he has refused to release. Since you're all ready to shoot him for it, I'm certain you must know spot on what it might be. So, what is it if you please?
And in case anyone wanted some objective information on the development of the hockey stick graphs, here's a good section from Wikipedia.
From the Wikipedia article on Michael E Mann
Postdoctoral research: the hockey stick graph
From 1996 to 1998, after defending his PhD thesis at Yale, Mann carried out
paleoclimatology research at the
University of Massachusetts Amherst funded by a
United States Department of Energy postdoctoral fellowship. He collaborated with
Raymond S. Bradley and Bradley's colleague
Malcolm K. Hughes, a Professor of
Dendrochronology at the
University of Arizona, with the aim of developing and applying an improved statistical approach to
climate proxy reconstructions. He taught a course in Data Analysis and Climate Change in 1997 and became a Research Assistant Professor the following year.
[1][17]
The first truly quantitative reconstruction of
Northern Hemisphere temperatures had been published in 1993 by Bradley and
Phil Jones, but it and subsequent reconstructions compiled averages for decades, covering the whole hemisphere. Mann wanted temperatures of individual years showing differences between regions, to find spatial patterns showing natural oscillations and the effect of events such as volcanic eruptions. Sophisticated statistical methods had already been applied to
dendroclimatology, but to get wider geographical coverage these tree ring records had to be related to sparser proxies such as ice cores, corals and lake sediments. To avoid giving too much weight to the more numerous tree data, Mann, Bradley and Hughes used the statistical procedure of
principal component analysis to represent these larger datasets in terms of a small number of representative series and compare them to the sparser proxy records. The same procedure was also used to represent key information in the
instrumental temperature record for comparison with the proxy series, enabling
validation of the reconstruction. They chose the period 1902–1980 for calibration, leaving the previous 50 years of instrumental data for validation. This showed that the statistical reconstructions were only skillful (statistically meaningful) back to 1400.
[18]
Their study highlighted interesting findings, such as confirming anecdotal evidence that there had been a strong
El Niño in 1791, and finding that in 1816 the "
Year Without a Summer" in Eurasia and much of North America had been offset by warmer than usual temperatures in Labrador and the Middle East. It was also an advance on earlier reconstructions in that it went back further, showed individual years, and showed
uncertainty with
error bars.
[19] "Global-scale temperature patterns and climate forcing over the past six centuries" (MBH98) was published on April 23, 1998, in the journal
Nature. In it, "Spatially resolved global reconstructions of annual surface temperature patterns" were related to "changes in greenhouse-gas concentrations,
solar irradiance, and volcanic aerosols" leading to the conclusion that "each of these factors has contributed to the climate variability of the past 400 years, with greenhouse gases emerging as the dominant
forcing during the twentieth century. Northern Hemisphere mean annual temperatures for three of the past eight years are warmer than any other year since (at least) AD 1400.
[20] The last point received most media attention. Mann was surprised by the extent of coverage which may have been due to the chance release of the paper on
Earth Day in an unusually warm year. In a
CNN interview,
John Roberts repeatedly asked him if it proved that humans were responsible for global warming, to which he would go no further than that it was "highly suggestive" of that inference.
[21]
In May 1998,
Jones,
Briffa and colleagues published a reconstruction going back a thousand years, but not specifically estimating uncertainties. As Bradley recalls, Mann's initial reaction to the paper was "Look at this. This is rubbish. You can't do this. There isn't enough information. There's too much uncertainty." Bradley suggested using the MBH98 methodology to go further back. Within a few weeks, Mann responded that to his surprise, "There is a certain amount of skill. We can actually say something, although there are large uncertainties."
[22][23] Mann carried out a series of statistical
sensitivity tests on 24 long term datasets, in which he statistically "
censored" each proxy in turn to see the effect its removal had on the result. He found that a dataset which would otherwise have been reliable diverged from 1800 until around 1900, suggesting that it had been affected for that time by the CO2 "
fertilisation effect". Using this dataset corrected in comparisons with other tree series, their reconstruction passed the validation tests for the extended period, but they were cautious about the increased uncertainties involved.
[24]
The Mann, Bradley and Hughes reconstruction covering 1,000 years (MBH99) was published by
Geophysical Research Letters in March 1999 with the cautious title
Northern Hemisphere temperatures during the past millennium: inferences, uncertainties, and limitations.
[23][25] Mann said that "As you go back farther in time, the data becomes sketchier. One can't quite pin things down as well, but, our results do reveal that significant changes have occurred, and temperatures in the latter 20th century have been exceptionally warm compared to the preceding 900 years. Though substantial uncertainties exist in the estimates, these are nonetheless startling revelations."
[26] When Mann gave a talk about the study to the
National Oceanic and Atmospheric Administration's
Geophysical Fluid Dynamics Laboratory, climatologist
Jerry D. Mahlman nicknamed the graph the "hockey stick".
[23]