Main Page | See live article | Alphabetical index

Michael Mann (scientist)

Michael Mann is an assistant professor at University of Virginia, Department of Environmental Sciences [1].

He is best known for his reconstruction of the Temperature record of the past 1000 years from tree ring, ice core, coral and other data.

Table of contents
1 Agreement on Mann's Work
2 Challenge to Manns's Work

Agreement on Mann's Work

Mann's reconstruction of temperature was reported in the IPCC TAR [1], which shows that his reconstruction agrees with Jones et al. (1998) and Briffa (2000), and in broad scale with borehole reconstructions by Pollack et al. (1998) [1].

Challenge to Manns's Work

Mann's reconstructions have been challenged by McIntyre (an officer or director of several small public mineral exploration companies [1]) and McKitrick (an Associate Professor at the Economics Department at the University of Guelph [1]), who say Mann's work contains "errors" and "defects" and called his "Hockey Stick" graph "an artefact of poor data handling".

However, McIntyre and McKitrick's complaints have themselves been challened [1].

McIntyre and McKitrick say:

" The data set of proxies of past climate used in Mann, Bradley and Hughes (1998, “MBH98” hereafter) for the estimation of temperatures from 1400 to 1980 contains collation errors, unjustifiable truncation or extrapolation of source data, obsolete data, geographical location errors, incorrect calculation of principal components and other quality control defects. We detail these errors and defects. We then apply MBH98 methodology to the construction of a Northern Hemisphere average temperature index for the 1400-1980 period, using corrected and updated source data. The major finding is that the values in the early 15th century exceed any values in the 20th century. The particular “hockey stick” shape derived in the MBH98 proxy construction – a temperature index that decreases slightly between the early 15th century and early 20th century and then increases dramatically up to 1980 — is primarily an artefact of poor data handling, obsolete data and incorrect calculation of principal components." [1]

Michael Mann says of M&M:

"...their analysis appears seriously flawed and amounts to a gross misrepresentation..." [1].

Dr. Tim Osborn, Professor Keith Briffa and Professor Phil Jones, Climatic Research Unit, University of East Anglia, Norwich, UK, say:

"Unfortunately neither MM03 nor the journal in which it was published took the necessary step of investigating (with Mann, Bradley or Hughes) whether the difference between MM03 results and MBH98 could be explained simply by some error or set of errors in MM03's use of the data or in their implementation of the MBH98 method. This should have been an essential step to take in a case such as this where the difference in results is so large and important. Especialy when the MM03 results, regarding a warm 15th century, were also at odds with the many other reconstructions that have been published, not just at odds with MBH98. Simple errors should first be ruled out prior to publication.

Mann, Bradley and Hughes have now made a preliminary investigation into the reasons for the different results, and have already identified a number of likely errors, which may turn out to be the cause of the different results.

Objective readers, with a desire to get to the "truth" of this issue, would do well not to jump to premature conclusions and at least allow these respected, experienced, and invariably careful researchers the courtesy of a considered response, after they have had time to study the so-called audit in detail."