who almost always use the same data sets and review each other's works. There is a contention that they would dismiss critics who had legitimate concerns, rarely used statistical experts for the data they used in their reports, and make it very difficult for reviewers to obtain background data and analysis. These revelations point to the lack of independent peer review and how it is practically impossible to replicate or verify Dr. Mann's work by those not affiliated with the network of scientists, so we are looking forward to hearing about that work today. Could it be that this particular work violates the principles of the scientific method and should be dismissed until it meets the basic qualifications? Could that have been some of what happened to the Ice Age return theory of the 1960s?

Climate is affected by numerous causes that interact with each other. When a scientific paper comes to a conclusion about climate, its results must be able to be replicated and shown to have direct causation and not merely correlation. If these steps cannot be done, then making conclusive statements of how one cause changes the climate is unwarranted and not real science.

Now, there is strong evidence that the Earth has warmed about half a degree Fahrenheit from 1900 to 1940 but this is widely attributed to an increase in solar activity during those years and there are indications that the Earth warmed another half degree Fahrenheit from 1940 until the present but that much of this warming occurred in the past 7 years, and if you look at the surface record in the satellite data, it is pretty clear and possible that this warming is mostly due to the 1998 El Nino, so for the past hundred years the Earth has warmed about one degree and you can make the cause that it was not caused by human activity but by natural events. Possibly that is what happened to the return of that old Ice Age.

Mr. Chairman, if one looks at the data in an objective manner, I believe that one would conclude that the Earth's climate is not in serious danger or not standing at the edge of a precipice. Maybe our focus should be first on getting the information. Maybe our focus should not be on environmentalism. Maybe the focus should be on common-sense conservatism. I would challenge my colleagues on the other side to approach this issue to learn the truth about the Earth's climate, not to form an agenda.

I am looking forward to our witnesses in the hearing today. I yield back.

MR. WHITFIELD. Thank you, Mrs. Blackburn. I think that concludes the opening statements so we will proceed to the first panel of witnesses, and I would say to you, Dr. North and Dr. Wegman, that this committee

practice of taking testimony under oath, and I would ask you, do either of you have any objection to testifying under oath?

Now, Dr. Wegman, accompanying you today is one of the statisticians that worked with your three-person panel, and would you introduce her? Although it is my understanding she is not going to be testifying but she is from Johns Hopkins, I believe.

DR. WEGMAN. That is correct. It is Dr. Yasmin Said. Dr. Said actually did a tour at Johns Hopkins but has just won a very prestigious National Institutes of Health postdoctoral fellowship and she will be with us in George Mason for the next 3 years.

MR. WHITFIELD. And although she is not going to testify, you may consult with her. Dr. Wegman, if you and Dr. North would stand up, I would like to swear you in. Of course, under the rules of the House and the rules of the committee, you are also entitled to legal counsel and I am assuming you don't need legal counsel today, but if you do-

DR. WEGMAN. Hopefully not.

MR. WHITFIELD. If you would raise your right hand. [Witnesses sworn.]

MR. WHITFIELD. Thank you, very much. You are now both under oath, and Dr. Wegman, you are recognized for your opening statement, and I would say to both of you, I know both of you have rather lengthy documents that we appreciate your preparing and those will be entered into the record in their entirety, and if you all could keep your statements to 5 to 7 minutes or so, we would appreciate that. Dr. Wegman, you are recognized.

STATEMENTS OF DR. EDWARD J. WEGMAN, CENTER FOR COMPUTATIONAL STATISTICS, GEORGE MASON UNIVERSITY; AND DR. GERALD R. NORTH, DEPARTMENT OF ATMOSPHERIC SCIENCES, TEXAS

A&M UNIVERSITY

DR. WEGMAN. Thank you, sir. I would like to begin by circumscribing the substance of our report. We were asked to provide independent verification by statisticians of the critiques of the statistical methodology found in the papers of Drs. Michael Mann, Raymond Bradley, and Malcolm Hughes published respectively in Nature in 1998 and in Geophysical Research Letters in 1999. These two papers have commonly been referred to as MBH98 and MBH99. The critiques have been made by Stephen McIntyre and Ross McKitrick published in Energy and Environment in 2003 and again in Energy and Environment and in Geophysical Research Letters in 2005. We refer to these are

We were also asked about the implications of our assessment. We were not asked to assess the reality of global warming and indeed this is not an area of our expertise. We do not assume any position with respect to global warming except to note in our report that the instrumented record of global average temperature has risen since 1850 according to the MBH99 chart by about 1.2 degrees Centigrade, and in the NAS panel report chaired by Dr. North, about six-tenths of a degree Centigrade in several places in that report.

Our panel is composed of myself, Edward Wegman at George Mason University, David W. Scott at Rice University, and as mentioned, Yasmin Said at the Johns Hopkins University. This ad hoc panel has worked on a pro bono basis. We have received no compensation, not even taxi fare, and no financial interest and we have no financial interest in this.

Can we see slide one, please? In figure 1, we have a document, a chart that came out of Dr. Bradley's book on paleoclimatology, and sort of indicates the kind of things that are used as proxy data in paleoclimatology. One thing I would like to point out in particular that is important I think for understanding this area is the things that are indicated--if you look-

MR. WHITFIELD. Dr. Wegman, we need for you to use your mic. I know it is going to be difficult but we could not hear you when you turned around there.

DR. WEGMAN. I will refrain from doing that. The point of this graphic is that there are many factors that affect all of the proxies that are used in paleoclimate temperature reconstruction, and without carefully teasing out those effects, the tree rings, the ice cores, and so on, are not by, in and of themselves totally temperature records.

So MBH98 and 99 use several proxy indicators to measure global climate change. Primarily these include historical records, tree rings, ice cores, and coral reefs. More details of the proxies are given in our report and mentioned in the written testimony.

Could we go to figure 2, please? Some examples of tree ring proxy series are given in figure 2. Most of the proxy series for these tree rings show little structure but the last two show the characteristic hockey stick shape. The principal component-like methodology in MBH98 and 99 preferentially emphasizes these shapes as we shall see. Principal component analysis methodology is at the core of the MBH98 and 99 analysis methodology. Principal component analysis is a statistical methodology often used for reducing data sets with many variables into data sets with fewer but composite variables. The time series proxy data involved are transformed into their principal components where the first

in the data variables. Each of the subsequent principal components explains less and less of the variation. In the methodology of MBH98 and 99, the first principal component is used in the temperature reconstruction.

Could we have figure 3, please? The two principal methods for temperature reconstructions have been used. CFR, climate field construction is used in MBH98/99 although that terminology was not used formally until 2005, I believe, and the other is CPS, climate-plusscale methodology. The CFR is essentially the principal componentbased analysis and the CPS is a simple averaging of climate proxies. The controversy of the MBH98/99 method lies in that the proxies are incorrectly centered on the mean period of 1902 to 1995, rather than on the whole time period. The proxy data exhibiting the hockey stick are actually decentered low. The updated MBH98/99 reconstruction is given in figure 3. This fact that the proxies are centered low is apparent in figure 3 because for most of the thousand years the reconstruction is below zero. This is temperature anomaly. Because the hockey stick proxies are centered too low, they will exhibit a large effective variance, allowing the method to exhibit a preference for selecting them as the first principal component. The net effect of decentering the proxy data in MBH98 and MBH99 is to produce the hockey stick shape. Centering on the overall mean is a critical factor in using principal component methodology properly.

Could we have figure 4, please? To illustrate this, we consider the North American tree series and apply the MBH98 methodology. The top panel shows the result from decentering. The bottom panel shows the result when the principal components are properly centered. The centering does make a significant difference in the reconstruction, and as you see, while the top panel illustrates the temperature rise or purported temperature rise in the last 100 years or so, the bottom panel when properly centered does not have this temperature rise.

Could we go to figure 5? To further illustrate this, we digitized the temperature profile published in the IPCC 1990 report and we did apply both the CFR and the CPS methods to them. The data used here are 69 unstructured noise pseudo-proxy series with only one copy of the 1990 profile. The upper left panel illustrates the PC1 with proper centering. In other words, no structure is shown. The other three panels indicate what happens when using principal components with an increasing amount of decentering. Again, the single series begins to overwhelm the 69 other pure noise series. Cleary, this decentering has a big effect.

It is not clear that Dr. Mann and his associates realized the error in their methodology at the time of publication but our re-creation supports

As commentary, in general we found the writing in MBH98 and 99 to be somewhat obscure and incomplete and the criticisms by MM03/05a and 05b to be valid. The reasons for setting 1902-1995 as the calibration period presented in the narrative of MBH98 sounds plausible on the surface and the error may be easily overlooked by someone not trained in statistical methodology. We note that there is no evidence that Dr. Mann or any of the other authors in the paleoclimate studies have significant interactions with mainstream statisticians.

Because of this apparent isolation, we decided to attempt to understand the paleoclimate community by exploring the social network of authorships in the temperature reconstruction area. We found that at least 43 authors have direct ties to Dr. Mann--and this should be figure 6, please; thank you--have direct ties to Dr. Mann by virtue of coauthored papers with him. Our findings from this analysis suggest that authors in this area of the relatively narrow field of paleoclimate studies are closely connected. Dr. Mann has an unusually large reach in terms of influence. He is the coauthor with every one of these people which are indicated by the black edge borders on the top and the side of this graph. In particular, he has a close connection with Drs. Jones, Bradley, Hughes, Briffa, Rutherford, and Osborne and those are indicated by the solid block on the upper left-hand corner.

This area of social networks is based off a graph theoretic representation, and if we go to figure 7, we can see the graph theoretic representation. Because of these close connections, independent studies may not be as independent as they appear to be on the surface. Although we have no direct data on the functioning of peer review within the paleoclimate community but, with me having 35 years of experience with peer review in both journals as well as evaluation of research proposals, peer review may not have been as independent as would generally be desirable.

Could we have figure 8, please? Figure 8 is a graphic that depicts a number of papers in the paleoclimate reconstruction area together with some of the proxies used. We note that many of the proxies are shared. Some of the same data also suggests a lack of independence.

The MBH98/99 work has been sufficiently politicized that this committee can hardly reassess their public positions without losing credibility. Overall, our community believes that the MBH98/99 assessment that the decade of the 1990s was likely the hottest decade in the millennium and that 1998 was likely the hottest year in the millennium cannot be supported by their analysis because of the mathematical flaws.

We have some recommendations which flowed out of our analysis.