Corrections to the Mann et al (1998) Proxy Data Base and Northern Hemisphere Average Temperature Series
Our conclusion, after detailed study of the
Mann et. al. data base, is that the “hockey stick” graph is an artefact of poor
data handling, selective use of sources, reliance on obsolete versions of
source data and erroneous statistical calculations. Correcting the copying
errors and updating the source data yields the following revision to the
The top diagram is from the Mann et. al. study
(with the error bars removed). The vertical axis measures “anomalies” or
departures from a notional hemispheric “average temperature” in tenths of a
degree C. The bottom diagram is based on the corrected data. Applying the Mann
et. al “multiproxy” procedure on their own data, when updated and correctly
collated, contradicts the claim that the late 20th century climate
is unusually warm or variable.
The above shows the same comparison using 20-year moving averages.
You can get the spreadsheet that produced these pictures
Here is the same figure in b&w.
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