MIT Technology Review...
has some second thoughts
about a widely published study of global warming.
A famous study done by MIT's own Michael Mann and others on the effects of humanity on global temperatures produced a pretty alarming graph that showed no real change in global temperatures until right at the start of the 20th century-the industrial revolution-where an alarming trend of warming appeared and predicted global doom for all mankind. This graph is widely used by proponents of the Kyoto Treaty to explain why the US needs to subjugate its domestic policy to a global body. Obviously, our short term political greed and evil can't stand in the way of dire emergencies with the planet's health!
Too bad Mr. Mann(I feel like Kathy Bates in Misery when I say that) apparently didn't test his methods very well, or his results. Stephen McIntyre and Ross McKitrick have produced some compelling evidence that the study is fundamentally flawed and the results are only correct if by coincidence they accidentally got the answer right. So far they've met with resistance in their attempts to publish their critique in a peer-review journal. Hopefully this article will go a ways toward letting them state their case. It's a pretty good one:
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!
When they say hockey stick, they mean the shape of the graph. Here's a pic of the graph itself:
If these guys are correct, it's probably not willful manipulation of the facts, but even so this kind of gross incompetence is really very bad for science, politics and you.
posted by M@ at 12:16 PM