article and writer aren't "pro" or "anti" global warming, just pointing out that there's apparently a fatal flaw in the methodology around one of the prime underpinnings supporting the theory of global warming. http://www.technologyreview.com/articles/04/10/wo_muller101504.asp?trk=nl -- A prime piece of evidence linking human activity to climate change turns out to be an artifact of poor mathematics. By Richard Muller Technology for Presidents 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. 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 into a short technical discussion of how this incredible error took place. In PCA and similar techniques, each of the (in this case, typically 70) different data sets have their averages subtracted (so they have a mean of zero), and then are multiplied by a number to make their average variation around that mean to be equal to one; in technical jargon, we say that each data set is normalized to zero mean and unit variance. In standard PCA, each data set is normalized over its complete data period; for key climate data sets that Mann used to create his hockey stick graph, this was the interval 1400-1980. But the computer program Mann used did not do that. Instead, it forced each data set to have zero mean for the time period 1902-1980, and to match the historical records for this interval. This is the time when the historical temperature is well known, so this procedure does guarantee the most accurate temperature scale. But it completely screws up PCA. PCA is mostly concerned with the data sets that have high variance, and the Mann normalization procedure tends to give very high variance to any data set with a hockey stick shape. (Such data sets have zero mean only over the 1902-1980 period, not over the longer 1400-1980 period.) The net result: the “principal component” will have a hockey stick shape even if most of the data do not. McIntyre and McKitrick sent their detailed analysis to Nature magazine for publication, and it was extensively refereed. But their paper was finally rejected. In frustration, McIntyre and McKitrick put the entire record of their submission and the referee reports on a Web page for all to see. If you look, you’ll see that McIntyre and McKitrick have found numerous other problems with the Mann analysis. I emphasize the bug in their PCA program simply because it is so blatant and so easy to understand. Apparently, Mann and his colleagues never tested their program with the standard Monte Carlo approach, or they would have discovered the error themselves. Other and different criticisms of the hockey stick are emerging (see, for example, the paper by Hans von Storch and colleagues in the September 30 issue of Science). Some people may complain that McIntyre and McKitrick did not publish their results in a refereed journal. That is true--but not for lack of trying. Moreover, the paper was refereed--and even better, the referee reports are there for us to read. McIntyre and McKitrick’s only failure was in not convincing Nature that the paper was important enough to publish. How does this bombshell affect what we think about global warming? It certainly does not negate the threat of a long-term global temperature increase. In fact, McIntyre and McKitrick are careful to point out that it is hard to draw conclusions from these data, even with their corrections. Did medieval global warming take place? Last month the consensus was that it did not; now the correct answer is that nobody really knows. Uncovering errors in the Mann analysis doesn’t settle the debate; it just reopens it. We now know less about the history of climate, and its natural fluctuations over century-scale time frames, than we thought we knew. If 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.
1500+ nobel laureates agree global warming is happening and is a result of human activity. Contending its not happening or not related to human activity is either delusional or a direct result of working for big oil.
Uh, yes. I read the article. I didn't really see a 'bombshell' in it. Wonder why Nature decided not to publish it? Maybe because people would trumpet it as a 'bombshell' that disproves the science behind global warming...(despite the fact that neither of these guys are climatologist - one is a statistician and one an economics professor). Let's take a look. Here's a good review of their findings (their own caveats notwithstanding): "The same fate is likely to befall Canadian researchers Steve McIntyre and Ross McKitrick, who have just destroyed the "hockey stick" theory on recent global warming for the British journal Energy & Environment. (Questioned the theory, or called it into doubt might be less-charged wording, but I'll stick with destroyed.) The "hockey stick" has been among the holiest of holies in the greenhouse priests' liturgy." Simply put, these are economists submarining Kyoto because of their economic concerns. 'Good science' indeed.
don't know how you got that from the article. he sstates quite clearly he's a believer, just that the math behind this implementation of the hocky stick is flawed. seems pretty convincing. this guy isn't bjorn lomberg.
google their names and you'll pull up nothing but anti-global warmingists using their conclusions to 'debunk' global warming in its entirety.
I don't see how it is a debateable thing if the problem is a mathematical one. It is either right or wrong.
Yeah, I don't really know about that, since he's got a book out about 'bad science' behind global warming. But if the numbers are wrong on this part of one theory of warming, why is that a bombshell if there is still a consensus that its happening and is man made?
What is it about so many Republicans? I honestly can't get it. Why do they feel compelled to deny science and global warming? Is it their Bible reading that makes them reject science like they do with evolution. I can understand the factory owners/ fat cats who oppose environmentalism or the tobacco company guys who just want to make a buck. Why do you have ordinary working guys like Basso so determined to deny gobal warming? Is it just child like faith in the GOP or Bush? What? It really doesn't seem like it should be a Democrat/ Republican thing, yet so many Republicans feel a need to deny global warming. The whole thing reminds me of the folks who tried for so many years to deny that cigarette smoke is bad for your health. I just don't get the need to try to deny global warming by the ordinary GOP members. Can someone explain it to me?
They're against regulations that hinder business. Same reason they're against environmental regulations generally (who cares about a spotted owl? loggers need jobs!; who cares about the arctic caribou - we need oil; who cares about turtles, fishermen need tuna! who cares about smog - detroit needs big profits! etc etc). Claims that Kyoto will crush the world economy are too scary for them.
I think that you are making some sweeping generalizations and stereotypes. Capitalism has created enormous wealth in this nation that has allowed us one of the highest standards of living in the world. With that we live in one of the cleaner environments and as we are growing more into a service economy, industrial plants are being opened in other countries. Outsourcing will also help to clean up our environment. The Kyoto accord was a farce and even Clinton did not pass it. Essentially the accord would have lowered US demand which would have lowered energy prices to others such as Japan and European nations creating more growth in their nations.
Yes. And? For those GOP members who aren't economists, they are pretty valid generalizations. Whether or not Kyoto would have crushed the world economy is another matter. We're talking about what everyday Republicans believe, which IMO has nothing to do with actual economic data (without granting any claims about Kyoto's actual projected effect).
With all respect, Glynch, you're the one who sounds "religious" about the subject. The article did not discount Global Warming - it merely pointed out that some of the math was wrong with regards to the initial findings. A good scientist would take all the evidence into consideration (and, again, the evidence does not dispute global warming - just the original methodology that arrived at the conclusions). As someone already mentioned a whole lot of other people have reached similar conclusions. Why is it when someone presents some science that contradicts something you believe in - even something as ho-hum as what was posted - you have to deny it without consideration? That reaction sounds very much like the reaction religious zealots have when someone contradicts doctrine. Global Warming is not religion. It's a "natural" phenomenon (as in it's happening in nature). If the science bears out that humans cause it - so be it. But if the science doesn't bear it out then what are you going to do? Dispute every study that comes out against your "beliefs"? As a rational thinking being the only reaction to this article should be something along the lines of "hmmm...that's interesting...” Also, as the authors point out it's really important to have sound science backing up the global warming theory because it's so important. Flawed science will just arm anti-global warming camps with ammunition. As I mentioned earlier, neither the article, nor the authors nor the original poster are disputing Global Warming. Why the religious reaction?
i wasn't aware that belief in GW broke on strict party lines. also, opposition to kyoto doesn't equal disbelief in GW.
I agree that you want to correct your models as you find mistakes. However, the authors mentioned do, or at least McIntyre does in his book. The only reason this is a 'bombshell,' rather than 'interesting' (as you put it) is that it is being used by those denying warming outright as proof for their claims. The 'rational' reaction, as you put it, is what Nature had, and why they decided not to publish. The body of evidence indicating warming is happening and at least to some extent because of human activity is so large that this correction is 'interesting' but that's it.
Not true in every case, for sure. But I don't think its out of line to generalize that the GOP is more likely to be against regulation than the Democratic party, especially where the environment is concerned; that the environment has a higher priority in the democratic party than the GOP; that the GOP would prioritize access to resources and/or jobs higher than potential environmental impact.
