Richard Muller, a believer in and cautionary on global warming, points out new analysis that calls into question one of the major statistical studies that has pointed to rising temperatures since the coal era began. That study shows a “hockey stick” of steady temps since medieval times, then rising temps over the last century.
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.
Even if random data is entered into the model, as calculated, it will show an increase in temps.
Muller remains convinced that global warming should be of concern — but is more interested, at this point, in making sure that bad analysis (which can mask as well as exaggerate climatic change) doesn’t pollute the pool of evidence.
f you are concerned about global warming (as I am) and think that human-created carbon dioxide may contribute (as I do), then you still should agree that we are much better off having broken the hockey stick. Misinformation can do real harm, because it distorts predictions. Suppose, for example, that future measurements in the years 2005-2015 show a clear and distinct global cooling trend. (It could happen.) If we mistakenly took the hockey stick seriously–that is, if we believed that natural fluctuations in climate are small–then we might conclude (mistakenly) that the cooling could not be just a random fluctuation on top of a long-term warming trend, since according to the hockey stick, such fluctuations are negligible. And that might lead in turn to the mistaken conclusion that global warming predictions are a lot of hooey. If, on the other hand, we reject the hockey stick, and recognize that natural fluctuations can be large, then we will not be misled by a few years of random cooling.
A phony hockey stick is more dangerous than a broken one–if we know it is broken. It is our responsibility as scientists to look at the data in an unbiased way, and draw whatever conclusions follow. When we discover a mistake, we admit it, learn from it, and perhaps discover once again the value of caution.
How … scientific.
(via GeekPress)
Well, there’s still the eyeball method. Glaciers are melting back, the Antarctic floating ice is melting pretty fast, cold water fish are moving closer to the poles, little atolls in the Pacific are slowly going under… It’s happening. The Why? has always been debatable, as well as the How Much More?
It seems that M&M may have it http://groups.google.com/groups?hl=en&lr=&c2coff=1&selm=417041db%40news.nwl.ac.uk&rnum=5 “target=”register only”>wrong, and have been wrong in the http://cgi.cse.unsw.edu.au/~lambert/cgi-bin/blog/2004/08#mckitrick6 “target=”register only”>past.
Interesting. And all of it way beyond my feeble understanding of statistics — that’s why I married a statistician. 🙂
I can grasp the concepts. Degrees vs. Radians being a big one, the rest of it I understand from a purely theoretical standpoint (I can follow the logic, but not able to posit an argument on it).
It would be interesting to have Margie go over it and see what she can glean from it.
And of course Randy’s point is the strongest real world point of view. Having been up to St. Marys once this summer, I was shocked by how much it has retreated up the valley from a decade ago.