The “hockey stick” graph purporting to show a rise in temperature in the 20th century has for years been viewed with suspicion by many scientists. Now researchers cited in this article in Technology Review take a close look the most compelling demonstration of global warming and finds that the hockey stick pattern was a mistake, nothing more than a mathematical artifact of the flawed method used to compile and analyze the data.
Now comes the real shocker. This improper normalization procedure tends
to emphasize any data that do have the hockey stick shape, and to
suppress all data that do not. To demonstrate this effect, McIntyre and
McKitrick created some meaningless test data that had, on average, no
trends. This method of generating random data is called “Monte Carlo”
analysis, after the famous casino, and it is widely used in statistical
analysis to test procedures. When McIntyre and McKitrick fed these
random data into the Mann procedure, out popped a hockey stick shape!
Spoons’ post on this subject has more detail. Also be sure the read the comments there from visitor Chuck.
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