Late last year, the debate over climate change was stirred up when an environmental economist, Ross McKitrick and a mining executive, Steven McIntyre, published a piece claiming to refute climatological research crucial to the claim that the last few decades have seen unparalleled global warming (the ‘hockey-stick‘ paper of Mann, Bradley and Hughes). According to McKitrick and McIntyre, the work of Mann et al was riddled with errors, The paper was loudly publicised by the American Enterprise Institute (home of John Lott) and, as you would expect, Flack Central Station. Mann et al produced an immediate rebuttal, and despite many promises of a rejoinder, McKitrick and McIntyre have never responded on the substantive issues[1].
This would be par for the course, except that McKitrick somehow managed to attract the attention of Aussie computer scientist Tim Lambert, famous for his demolition of Lott’s shonky research, which purported to show that guns reduce crime. The result: McKitrick’s work is even shoddier than Lott’s.
Lambert has mainly focused not on the McKitrick and McIntyre paper but on a subsequent piece by McKitrick and Pat Michaels, which contains a regression purporting to show that it is GDP growth that causes (measured) climate change. McKitrick and Michaels take this as support for the generally-discredited ‘urban heat islands’ hypothesis, that measured warming is an artifact produced by weather stations in or near big cities.
In previous rounds of the debate, Lambert has shown that McKitrick messed up an analysis of the number of weather stations, showed he knew almost nothing about climate, flunked basic thermodynamics, couldn’t handle missing values correctly and invented his own temperature scale.
But Tim’s latest discovery really takes the cake. It’s well-known that the rate of warming varies with latitude, but McKitrick and Michaels find no such effect for their variable, which is the cosine of absolute latitude. Lambert checked and, amazingly enough, found that the data set used by McKitrick and Michaels had latitude in degrees, but the cosine function in the SHAZAM econometric package, they used expected input in radians (which is what any mathematically literate person would expect). If you apply this function to angles measured in degrees you get nonsense.
Once Lambert did the correct analysis, latitude was highly significant and the economic variables became much less important. The results reported by McKitrick and Michaels can be explained by an obvious confounding effect. Rich countries tend to be at high latitudes, and so GDP acts as a proxy for latitude.
Although Tim is almost invariably right in such matters, it was hard to believe that such a gross error could go undetected – it would show up immediately if you looked at descriptive stats on the variables, for example. So I checked myself. The descriptive statistics in the McKitrick and Michaels paper (available here) include the latitude, which is clearly in degrees, but not the cosine variable. The SHAZAM documentation, here, indicates that input to the sine function is in radians ( McKitrick and Michaels derive cosine using a transformation of this).
Bear in mind that McKitrick’s main claim to fame is his assertion to have done a painstakingly careful check of the work of others and to have found numerous errors. Looking at Lambert’s demolition of this paper, I’m reminded of what Julian Sanchez had to say about Lott – if he told you the time was 12 o’clock, you’d check your watch before you believed him[2].
And Michaels was a reputable climate scientist before he sold out to the fossil fuel lobby. It looks as though, as long as he says what his employers want to hear, they don’t feel the need for quality control.
fn1. There was a secondary dispute about the provision and labelling of data, as a result of which Mann et al published a very short corrigendum in Nature, noting that they had incorrectly described some parts of the data set, but that this had no implications for the results.
fn2. Interestingly, Sanchez, like Michaels, has worked at the Cato Institute, which shows that it’s not safe to make generalizations about institutions based on a few, or even a lott, of bad apples. Even TCS publishes some work by reputable people, to add cachet to its real output of lobby-fodder.
{ 16 comments }
Kieran Healy 08.26.04 at 1:13 am
Iain Murray published a “shitty little article”:https://www.crookedtimber.org/archives/000781.html on Flack Central about this where he tried to assert that McKitrick & Michaels’ paper showed that the climatologists had faked their data.
Realist 08.26.04 at 3:29 am
[]
Interesting article.
BTW, he is quite wrong on details (such as second hand smoke) where there is clear, clean evidence.
Note from JQ: I deleted a repost of an entire article by Michael Crichton here and replaced it with this link.
vernaculo 08.26.04 at 10:38 am
Crichton- “The greatest challenge facing mankind is the challenge of distinguishing reality from fantasy, truth from propaganda.”
Unless we’re right.
Then the greatest challenge facing mankind would be violently catastrophic ecological disruption. During which being able to tell the true from the false would certainly still be vitally important. Just as it is when driving or playing golf.
Ethesis 08.26.04 at 1:01 pm
“Unless we’re right.”
Might I ask, about what? Global cooling?
Obviously significant steps need to be taken to continue towards strategic environmental goals.
Crichton only makes the point that the current environment is driven by people who are religious about it rather than scientific, with his starkest example being the 20-30 million already dead from the anti-DDT campaign. Of course Crichton’s background in health care affects the way he feels about those deaths. I’ve talked with people who felt that they weren’t enough.
I think the points are interesting, though I agree that he is wrong on some of his presumptions (which makes me question some of his conclusions).
But he is really calling for real verification and real science, not religion in addressing real problems (assuming that Vernaculo sees the environmental problems as real rather than as religious props).
Makes sense, the environmental problems we face are real. Real science (such as the large particle studies fueled by the Geneva Steel statistics showing that they are actually a threat to human health) seems to be called for.
I don’t know about you, but I have children, and I want a better world for them.
praktike 08.26.04 at 1:37 pm
See, Chrichton wasn’t calling for real science, though. He was calling for garbage like M&M to be accepted just because it bucked the consensus, which wasn’t exactly arrived at willy-nilly.
Sam 08.26.04 at 2:46 pm
I must say that I’m only slightly surprised, but can easily believe that the mistake was an honest mistake. I trained in Econometrics, and worked for almost a year once on a paper with a major math error. I took the derivative of x^2 as x instead of 2x, and used the code-block with that error pervasively in my programming. The paper was reviewed by colleagues numerous times, and no one caught that error until the last review before I would have submitted it for publication. It’s not hard for me to believe that the error of inputting values in degrees when they should have been in radians was an honest mistake–one which I’m glad someone found.
Dem 08.26.04 at 5:59 pm
Crichton’s article was interesting, with some good points. But it was riddled with bad logic.
1) I liked the opening discussion about how the idea of Eden — the “idyllic natural environment before white man spoiled it” — is a myth. But in setting this up he’s setting up a straw man of the environmental movement as people who love nature but don’t know what nature really is. The most strident environmentalists I know all spend lots of time in wilderness experiencing nature. And not all nature is as hostile to humans as the Borneo example … consider John Muir setting up his cabin in Yosemite as a counter-example.
2) His comment about the predictors of overpopulation getting it wrong is equivalent to saying those who predicted Y2K computer problems got it wrong. He misses the key point that because of the predictions actions were taken to counter the impending disaster. In both cases, the responsible scientists predicted that “unless action was taken to change the trend” disaster would strike. In Y2K, billions were spent testing and upgrading software and hardware to prevent the disaster. For the population explosion, billions have been spent researching and distributing contraception, and researching and addressing the root causes of overpopulation.
3) His paragraph that starts talking about second hand smoke pretty much discredits the validity of the entire piece. He doesn’t give the references behind each of his startling claims, but if you have any knowledge of these areas you know he is cherry-picking data and ignoring the whole.
Thomas Palm 08.26.04 at 7:09 pm
Crichton may have a lot he claims he can tell us, but that doesn’t mean he is correct. His statements about DDT are misleading at best.
DDT has never been banned for use to fight malaria. What caused the resurgence in malaria was lack of funding and increased resistance both to DDT, other pesticides and the most common medicines against malaria. The way DDT was used in agriculture and sprayed everywhere to get rid of annoying but harmless insects helped promote resistance. Researchers knew this from the start and urged that DDT should be reserved for fighting malaria so that it would remain effective as long as possible, but no one listened to them. If he wants to blame someone Crichton should blame the farmers.
In the same way Crichton claims that DDT is harmless. This isn’t really true, but it has a grain of truth. The major damage to birds come not from DDT but from DDE, which is formed when DDT breaks down in nature. Thus DDT is still to blame.
John Quiggin 08.26.04 at 8:54 pm
My guess is that the mistake was “half-honest”. That is, M&M were running lots of regressions, trying to find a specification that gave them the answer they wanted.
In particular, I’ll bet they used absolute latitude before trying the cosine and found it highly significant. When they found that their cosine variable was insignificant, and the economic variables came out “right”, they didn’t look to hard at the diagnostic stats.
Matt Weiner 08.26.04 at 10:24 pm
It seems to me that if McKittrick is half-honest his work isn’t shoddier than Lott’s; Lott made up data.
OTOH if McKittrick said
there is no such thing as a Global Temperature. Temperature is a continuous field, not a scalar, and there is no physics to guide reducing this field to a scalar, by averaging or any other method
then if I’m not mistaken he’s a buffoon. Can’t you integrate over the space on which the field takes values?
Ethesis 08.27.04 at 1:26 am
Good points on Crichton — it was interesting to discover he was as wrong on other points as he was on second hand smoke.
Thanks!
Neil Sinhababu 08.27.04 at 7:26 am
I just want to affirm that Tim Lambert is awesome.
joe silverman 08.27.04 at 7:49 pm
the y2k example is an example of the familiar argument that the wasteful and mostly unnecessary steps we took to avoid disaster must have worked…because the disaster didn’t happen as predicted. as i was on the inside of that “disaster” i can attest to the fact that there were a lot of groups that found it useful to (1) predict disaster and (2) profit from a lot of unnecessary efforts to avoid it. i’m not on the inside of possible environmental “disasters” so i can’t comment intelligently on that subject…but i am cautious about all claims on almost all subjects.
Dem 08.27.04 at 11:40 pm
joe silverman: the y2k example is an example of the familiar argument that the wasteful and mostly unnecessary steps we took to avoid disaster must have worked…because the disaster didn’t happen as predicted.
I’ll agree with you on a lot of what you said, but let’s not pretend there wasn’t truly a severe problem to be solved with Y2K.
Yes, you are correct that the lack of a disaster, by itself, doesn’t prove there ever was a problem.
You are also right that most of the steps taken were unnecessary. Once the ball got rolling lots of people took advantage of Y2K to either sell stuff to unsuspecting people (thanks, MSFT), or (in the case of IT depts) use Y2K to justify getting stuff they wanted but couldn’t get approval of otherwise.
However, I too was on the inside of Y2K, having worked at a major computer vendor, and I took away three lessons. First, there really was a serious problem. We found lots of things in our operating system code that would have taken the computers down, either on that day or soon thereafter. Second, that a lot of noise had to made by engineers before the leaders reacted (it wasn’t until the CEO realized he was personally liable if precautions weren’t taken that he took action). And third, that all that noise we made caused an over-reaction, causing huge overexpenditures.
dave heasman 08.28.04 at 12:37 am
I was on the inside of the Y2000 software project. Mirror Group newspapers spent £170 000 for 4 experts to spend a year ensuring that adverts could be booked (in advance, obviously) over the year-change. We inspected programs, designed a coherent solution, changed and tested 800+ programs, drove it through user-testing and against an unchanged suite. Hard, fairly rewarding work. Almost certainly worth the money to the customer. All it took to make it cost-effective was for one competent person at the customer site hiring an expert contractor to scope the project and then hire more experts directly. If they’d used a major software house they’d have got inferior results and spent over a million. Ho hum, as the New Yorker has stopped saying.
liberal japonicus 08.30.04 at 4:22 am
John,
shonky = sh*tty + wonky??
And thank god for Tim Lambert.
Comments on this entry are closed.