Mann, Bradley & Hughes (1998)
McIntyre & McKitrick (2003)

The recent paper by McIntyre and McKitrick (Energy and Environment, 14, 751-771, 2003; hereafter MM03) claims to be an "audit" of the analysis of Mann, Bradley and Hughes (Nature, 392, 779-787, 1998; hereafter MBH98).

We suggest that those interested in the claim by MM03 should also read the initial response from Mann and his colleagues, available from the link below.

The MBH98 reconstruction of Northern Hemisphere temperature since 1400 AD is an important result that certainly deserves scientific attention. MM03 obtain a rather different result to MBH98, which - if it were correct - would be very important.

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. Especially 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.

Mann, Bradley and Hughes' preliminary response to MM03 is available here:

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