Global warming Bombshell ...

[Stormsfury]

http://www.technologyreview.com/article ... asp?trk=nl

Global Warming Bombshell
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.

Richard A. Muller, a 1982 MacArthur Fellow, is a physics professor at the University of California, Berkeley, where he teaches a course, called “Physics for Future Presidents.” Since 1972, he has been a Jason consultant on U.S. national security.

[x-y-no]

That's how science works.

I am a little disappointed in "Nature" for not publishing this analysis. While I think the characterization of Mann's work as a "key piece" of global warming evidence is a bit of an exaggeration, it was certainly viewed as important work, and therefore its refutation is surely important as well.

There's plenty more to the body of evidence about global warming, though.

[MGC]

And still no explaination of the heat wave of the 1930's when global CO2 levels were way below todays.......MGC

[rainstorm]

scientists with an agenda will make the facts fit the theory

[vbhoutex]

scientists with an agenda will make the facts fit the theory

Don't most scientists have an agenda?

Very interesting read! Thanks SF!!!

[Sanibel]

Global warming is connected to man controling his population explosion and destruction of the planet's open space and environment. It's not surprising people are willing to seize on speculation about the forumla being off.

The melting glaciers and rapidly-changing habitats speak enough without the formula. I'm amazed because some reactionary people want to jump on this that they think it makes those recorded GW events happening now go away...




.

[MWatkins]

Global warming is connected to man controling his population explosion and destruction of the planet's open space and environment. It's not surprising people are willing to seize on speculation about the forumla being off.

The melting glaciers and rapidly-changing habitats speak enough without the formula. I'm amazed because some reactionary people want to jump on this that they think it makes those recorded GW events happening now go away...
.

I don't think this was the point of the article at all. In fact, the author still is a proponent of the idea that the planet is getting warmer:

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.

I think the real inflamotory question...not addressed here...is whether the warming is man-made...and I'm not sure that anyone has proven this conclusively.

MW

[Sanibel]

Let's wait until 2015. I doubt the planet will cool.


People are not waiting for perfect science to know what to do. They are looking for cop-outs for the reasons I cited above. Some people just want to build forever and pretend it isn't killing the planet. The process shouldn't be divided, it's all one process...



.

[Sanibel]

I think people are forgetting that just a few weeks ago a new report came out telling how in the last 2 years the rate of GW jumped higher than previously forecasted...

.

[gtalum]

I know no one who refutes the idea of global warming. What is refuted here is the idea that mankind has had a significant effect on it. IMHO it's egomania that drives us to blame ourselves for geological cyclic changes that have been occurring for Billions of years on our planet. We are on the way up out of an ice age that occurred just 10,000 years ago, the blink of an eye in geological terms. That coupled with teh fact that we have only had an accurate picture of global average temperatures for ~40 years (the satellite age) means that the data we have on long-term trends is nearly worthless in determining such a thing anyway. What we need to do is focus on ways to insulate ourselves from the effects of global warming since there is no way we're going to stop it. Creating legislation like Kyoto that will destroy our economy in a futile attempt to thwart global warming is not the way to save ourselves from the impending problem.

[Sanibel]

That coupled with the fact that we have only had an accurate picture of global average temperatures for ~40 years (the satellite age) means that the data we have on long-term trends is nearly worthless in determining such a thing anyway.

I find people living in areas now undergoing high sprawl rates, where the economy depends on this, tend to adhere to the conservative position.

The quote above is in direct contrast to ice and earth core sampling and other advanced scientific methods currently used to determine earth climate cycles for the past 100,000 years or more. I know that some more knowledgeable members are aware of this. I find it telling that they don't come in and say so in relation to posts that uphold the conservative view...

A few days ago I saw a story on CNN about having to take measures to prevent ozone and particulate damage to the nervous system just from the air outside. They were talking about damage that kills you...

[vbhoutex]

That coupled with the fact that we have only had an accurate picture of global average temperatures for ~40 years (the satellite age) means that the data we have on long-term trends is nearly worthless in determining such a thing anyway.

I find people living in areas now undergoing high sprawl rates, where the economy depends on this, tend to adhere to the conservative position.

The quote above is in direct contrast to ice and earth core sampling and other advanced scientific methods currently used to determine earth climate cycles for the past 100,000 years or more. I know that some more knowledgeable members are aware of this. I find it telling that they don't come in and say so in relation to posts that uphold the conservative view...

A few days ago I saw a story on CNN about having to take measures to prevent ozone and particulate damage to the nervous system just from the air outside. They were talking about damage that kills you...

Please expound on what you mean that you "find it telling that they don't come in and say so in relation to posts that uphold the conservative view".

Could be they haven 't seen the posts yet since this just started today.

[Wnghs2007]

Interesting read SF Thanks.

[wxman57]

Let's wait until 2015. I doubt the planet will cool.

You didn't read the article closely. The paragraph below was just an example, not a forecast. Personally, I'm with the majority of atmospheric scientists who question that man has anything at all to do with any global warming. I believe that it was calculated that when Mt. Pinatubo errupted back in the 90s that it spewed more greenhouse gasses out than man has produced over his entire history on earth.

"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."

Here's another good link about the "global warming" myth:
http://www.intellicast.com/DrDewpoint/Library/1305/

I remember back in the 70s when all the environmental nuts were talking about "global cooling" and the next ice age coming because of man's pollution. The environmentalist groups have a definite anti-industry agenda. No matter what is predicted, man must be at fault. I think the planet is much more resilliant than they give it credit for.

[Wnghs2007]

Let's wait until 2015. I doubt the planet will cool.

You didn't read the article closely. The paragraph below was just an example, not a forecast. Personally, I'm with the majority of atmospheric scientists who question that man has anything at all to do with any global warming. I believe that it was calculated that when Mt. Pinatubo errupted back in the 90s that it spewed more greenhouse gasses out than man has produced over his entire history on earth.

"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."

Here's another good link about the "global warming" myth:
http://www.intellicast.com/DrDewpoint/Library/1305/

I remember back in the 70s when all the environmental nuts were talking about "global cooling" and the next ice age coming because of man's pollution. The environmentalist groups have a definite anti-industry agenda. No matter what is predicted, man must be at fault. I think the planet is much more resilliant than they give it credit for.

Thanks for the information and I totally agree wxman57

[stormcloud]

So many people have pointed to the warm waters of the Atlantic and the unusual hurricane season and yelled 'global warming!' Dr. Bill Gray predicted these kind of oscillations over 25 years ago.

[x-y-no]

So many people have pointed to the warm waters of the Atlantic and the unusual hurricane season and yelled 'global warming!' Dr. Bill Gray predicted these kind of oscillations over 25 years ago.

So if someone points to a car bombing and says "Arab terrorists" and it turns out to have been done by someone else - that means Arab terrorists don't exist?

[crice]

Off point a bit but: I have always felt it was a little species-arrogant to say that Homo Sapiens was killing the planet. What we should be concerned about is if Homo Sapiens are like yeast in a fermentation tank, producing wastes in a closed environment that will eventually kill off the yeast while leaving behind a vessel that will normalize its chemistry in time, of course there won't be any yeast to enjoy it.

[rainstorm]

scientists with an agenda will make the facts fit the theory

Don't most scientists have an agenda?

Very interesting read! Thanks SF!!!

they are supposed to make conclusions based on facts. instead, they mold "facts" to fit pre-existing conclusions

[WXBUFFJIM]

The globe could easily cool or easily warm up in my lifetime. In this case it seems to be warming.

Jim