Mann's hockey stick wrong?

Francis Massen
file: hockeystick01.html, version 1.1, 31Oct2003

The hockey-stick graph of the Mann, Bradley and Hughes calculation of past temperature was the master-piece evidence to declare that global warming is unprecedented during the last years compared to the temperature profile of the preceeding centuries (see: Mann, Bradley, Hughes (1998): Global-Scale Temperature Patterns and Climate Forcing Over the Past Six Centuries, Nature, No. 392, pp. 779-787, 1998).
Here is the original hockey stick graph with a comment from co2andclimate (see:

Now it seems that the graph is based on faulty and/or incomplete data; a recalculation using Mann's own methodology has been made by independent (not sponsored nor funded!) researchers Stephen McIntyre and Ross McKitrick (Corrections to the Mann et. al. (1998) Proxy Data Base and Northern Hemispheric Average Temperature Series, Energy & Environment, vol.14, number 6, 2003, ISSN 0958-305X; complete text as as pdf file here), . The results are staggering: if correct data are used, there is no hockey stick, no unprecedented warming during the late 20th century!


This paper is a possible fatal blow to one of the IPCC's pillars in "documenting" global warming!

Here the conclusion of the authors;

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

So, is a man-made global warming just a wishful thinking of the IPCC and it's fellows?


Here a letter from Prof. Fred Singer (also a "climate sceptic") with more information:

Dear All
There is an additional point I would like to add to Aynsley Kellow's
excellent letter:
1. As Knutti/Joos/Stocker correctly point out, the IPCC conclusion, i.e.,
that the 20th century was the warmest in 1000 years, is based on the
instrumental record of surface temperature and NOT on the Mann et al
reconstruction. They should have said "SOLELY based" since Mann et al
stopped in 1980, at which point their temperature did not exceed the
Medieval values.
2. Mann et al do not show proxy temperatures beyond 1980. When I
questioned him regarding this matter 3 years ago, he replied by e-mail that
there were no suitable data available. I had found several proxy records
[1-6] that extended well beyond 1980; none showed higher temperatures.
3. I have now examined several dozen more [7]; again none show higher
4. I conclude therefore that -- contrary to Mann -- many data sets ARE
available; as far as can tell, none agree with the instrumental
SURFACE record; all agree with the satellite and balloon data that show NO
appreciable atmospheric warming trend after 1979.[8]
5. Hence, the IPCC conclusion is not tenable

Best Fred Singer
1. Briffa K.R. 2000.Annual climate variability in the Holocene:
Interpreting the message of ancient trees. Quat. Sci. Rev. 19: 65-73 ;
2. Broecker W. S. 2001. Was the medieval warm period global? Science 291:
3. Dahl-Jensen, D., Mosegaard, K., Gundestrup, N., Clow, G.D., Johnsen,
S.J., Hansen, A.W. and Balling, N. 1998. Past temperatures directly from
the Greenland Ice Sheet. Science 282: 268-271;
4. Jacoby et al 1996 Mongolian tree rings and 20th century warming, Science
273: 771-773; Jacoby and DArrigo 1997 Proc Natl Acad Sci USA 94: 8351;
5. Naurzbaev, M.M. and Vaganov, E.A. 2000. Variation of early summer and
annual last two millennia inferred from tree rings. J Geophys Res 105:
6. Thompson L. G. et al. 2000. Ice core evidence for climate change in the
tropics. Science 289: 1916, Fig 6B
7. Singer, S.F. 2003. Science 301, 595 .
8. A full account is submitted for publication elsewhere.
S. Fred Singer, Ph.D.
President, The Science & Environmental Policy Project (SEPP)
1600 S. Eads St., Suite 712-S
Arlington, VA 22202-2907
e-mail: Web:
Tel: 703-920-2744