A detailed review of the book: ‘A Disgrace to the Profession’, by Mark Steyn

WUWT
The hockey stick was never validated, yet it became so famous that it was taught to young children all over the world in elementary schools. Many years later, in 2005, it was thoroughly debunked by Steve McIntyre and Ross McKitrick (often abbreviated M&M). They showed that using the statistical technique invented by Michael Mann even random number series (persistent trendless red noise, see M&M Figure 1) will generate a hockey stick. Basically, Mann had mined many series of numbers looking for hockey stick shapes and gave each series that had the shape he wanted a much higher weight, up to a weighting factor of 392! This was truly a case of selecting a desired conclusion and then molding the data to fit it. Prominent statisticians Peter Bloomfield, Dr. Edward Wegman and Professor David Hand said Michael Mann’s method of using principle components analysis was inappropriate and misleading and exaggerated the effect of recent global warming."