BrothersJudd Blog: CANADIANS VS. HOCKEY:

BrothersJudd Blog: CANADIANS VS. HOCKEY:: "CANADIANS VS. HOCKEY:



Global Warming Bombshell : A prime piece of evidence linking human activity to climate change turns out to be an artifact of poor mathematics. (Richard Muller, October 15, 2004, Technology for Presidents)



Progress in science is sometimes made by great discoveries. But science

also advances when we learn that something we believed to be true isn't.

When solving a jigsaw puzzle, the solution can sometimes be stymied by

the fact that a wrong piece has been wedged in a key place.



In the scientific and political debate over global warming, the latest

wrong piece may be the 'hockey stick,' the famous plot,

published by University of Massachusetts geoscientist Michael Mann and

colleagues. This plot purports to show that we are now experiencing the

warmest climate in a millennium, and that the earth, after remaining

cool for centuries during the medieval era, suddenly began to heat up

about 100 years ago--just at the time that the burning of coal and oil

led to an increase in atmospheric levels of carbon dioxide.



I talked about this at length in my December 2003 column. Unfortunately,

discussion of this plot has been so polluted by political and activist

frenzy that it is hard to dig into it to reach the science. My earlier

column was largely a plea to let science proceed unmolested.

Unfortunately, the very importance of the issue has made careful science

difficult to pursue.



But now a shock: Canadian scientists Stephen McIntyre and Ross McKitrick

have uncovered a fundamental mathematical flaw in the computer program

that was used to produce the hockey stick. In his original publications

of the stick, Mann purported to use a standard method known as principal

component analysis, or PCA, to find the dominant features in a set of

more than 70 different climate records.



But it wasn't so. McIntyre and McKitrick obtained part of the program

that Mann used, and they found serious problems. Not only does the

program not do conventional PCA, but it handles data normalization in a

way that can only be described as mistaken.



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!



That discovery hit me like a bombshell, and I suspect it is having the

same effect on many others. Suddenly the hockey stick, the poster-child

of the global warming community, turns out to be an artifact of poor

mathematics. How could it happen? What is going on? Let me digress..."