Global Warming Bombshell

[Cicero]

By Richard Muller October 15, 2004

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 (shown below), 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.

<snip>

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!

http://www.technologyreview.com/articles/04/10/wo_muller101504.asp

Mr. Muller then goes on to say that while he counts himself among those who are concerned about global warming and that humans have a hand in causing it, he believes that it is ultimately a good thing that the "hockey stick" has been "broken".

Discussion?

Later,

[On the Road]

1. I Admire This Kind of Thing

You certainly don't see it from the revisionist or corporate-supported side. And it certainly doesn't undercut global warming at all -- just look at the right side of that graph.

To paraphrase Richard Feynman: the most important thing is to prove yourself wrong as quickly as possible.

[chomskysright]

2. great post: use ur critical thinking to check out the stats....

[Nothing Without Hope]

3. So important - needs good descriptive explanations in news media

Statistical arguments are opaque to non-statisticians unless explicated very clearly and concisely. This finding is so important -- I hope there is a highly motivated statistics-trained master explicator/teacher out there who will give this story the boost it needs into comprehensibility by the general public.

On the human side, this is another example of how dangerous it is for scientists to become too attached to their favorite theories and fantasize that they are proven facts rather than working hypotheses that require constant testing and rethinking. As has been said in another context:

To have doubted one's own first principles is the mark of a civilized man. -Oliver Wendell Holmes, Sr., poet, novelist, essayist, and physician (1809-1894)

This is really a universal observation and could be restated:

To have doubted one's favorite theories is the mark of a true scientist.

[UL_Approved]

4. This points out several flaws

1. Bad data model/filtering

2. Bad data set

Not only was the analysis model/filtering scheme inaccurate and biased for a specified trend, the data set consisted of a very confined and localized set of tree ring samples. These samples used in the old analysis showed massive deviation from broader sample spaces.

Now, this could be very interesting to see what happens in the future. Global warming is still up for grabs. One thing that I know from my own experience is what my 92-year grandfather says every time he is outside in the summer: the sun is hotter than it used to be. I tend to agree with his observations.

[phantom power]

5. The Real-Climate folks don't buy it

You can read their opinions of McIntyre and McKitrick here:
http://www.realclimate.org/index.php?p=8

They also have a "myth-vs-fact" discussions of the "hockey-stick":
http://www.realclimate.org/index.php?p=11

[Viking12]

6. M&M nothing more than industry disinfo......

Ross McKitrick is an economist who suggests global warming does not exist. However, his work shows an ignorance of basic science which, when remedied, invalidates his claims.

Notably, he has messed up an analysis of the number of weather stations (http://cgi.cse.unsw.edu.au/~lambert/cgi-bin/blog/2004/04#mckitrick), showed he knew almost nothing about climate (http://cgi.cse.unsw.edu.au/~lambert/cgi-bin/blog/2004/04#mckitrick2), flunked basic thermodynamics (http://cgi.cse.unsw.edu.au/~lambert/cgi-bin/blog/2004/05#georgia), couldn’t handle missing values correctly (http://cgi.cse.unsw.edu.au/~lambert/cgi-bin/blog/2004/05#mckitrick3) and invented his own temperature scale (http://cgi.cse.unsw.edu.au/~lambert/cgi-bin/blog/2004/07#mckitrick5).


Deja Hockey Stick


In this column, Richard Muller claims that McKitrick and McIntyre have shown that the hockey stick graph is an “artifact of poor mathematics”. If you have been following the global warming debate this claim should look familiar, because McKitrick and McIntyre made the same claim last year as well. So what’s new? Well, last year they claimed that the hockey stick was the product “collation errors, unjustifiable truncations of extrapolation of source data, obsolete data, geographical location errors, incorrect calculations of principal components, and other quality control defects.” Now they are saying that the hockey stick is the product of improper normalization of the data. This is an improvement on their previous claims, since it seems that it will be reasonably simple to test. William Connolley has looked at the data and thinks M&M are probably wrong:


http://cgi.cse.unsw.edu.au/~lambert/cgi-bin/blog/science/McKitrick/index.plain

http://cgi.cse.unsw.edu.au/~lambert/cgi-bin/blog/science/McKitrick/


http://www.disinfopedia.org/wiki.phtml?title=Ross_McKitrick