monies and human lives are at stake, academic work should have a more intense level of scrutiny and review. It is especially the case that authors of policy-related documents like the IPCC report should not be the same people as those that constructed the academic papers.

We believe that federally funded research agencies should develop a more comprehensive and concise policy on disclosure. All of us writing this report have been federally funded. Our experience with Federal funding agencies has been that they do not generally articulate clear guidelines to the investigators as to what must be disclosed. Federally funded work, including code, should be made available to other researchers upon reasonable request, especially if the intellectual property has no commercial value. Some consideration should be granted to the data collectors to have exclusive use of their data for 1 or 2 years prior to publication but data collected under Federal support should be made publicly available.

Recommendation three: With clinical trials for drugs and devices to be approved for human use by the FDA, review and consultation with statisticians is expected. Indeed, it is standard practice to include statisticians in the application for approval process. We judge this to be a good policy when public health and also when substantial amounts of monies are involved--for example, when there are major policy decisions to be made based on statistical assessments. In such cases, evaluation by statisticians should be standard practice. The evaluation phase should be a mandatory part of all grant applications and funded accordingly.

Finally, recommendation four; emphasis should be placed on the Federal funding of research related to a fundamental understanding of the mechanisms of climate change. Funding should focus on interdisciplinary teams and avoid narrowly focused disciple research. That is a general comment and by interdisciplinary teams, I mean including teams that involve what I like to call the enabling sciences such as mathematics, computer science, and statistics. Thank you, sir.

[The prepared statement of Dr. Edward J. Wegman follows:]

PREPARED STATEMENT OF DR. EDWARD J. WEGMAN, CENTER FOR COMPUTATIONAL STATISTICS, GEORGE MASON UNIVERSITY

I would like to begin by circumscribing the substance of our report. We were asked to provide an 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 in Energy and Environment and in Geophysical Research Letters in 2005. We refer to these as MM03, MM05a, and MM05b respectively. 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 MBH 99 chart by about 1.2° centigrade. In the NAS panel Report chaired by Dr. North, .6° centigrade is mentioned in several places.

Our panel is composed of Edward J. Wegman (George Mason University), David W. Scott (Rice University), and Yasmin H. Said (The Johns Hopkins University). This Ad Hoc Panel has worked pro bono, has received no compensation, and has no financial interest in the outcome of the report.

MBH98, MBH99 use several proxy indicators to measure global climate change. Primarily, these include historical records, tree rings, ice cores, and coral reefs. More details of proxies are given in the report and mentioned in the written testimony. [The width and density of tree rings vary with climatic conditions (sunlight, precipitation, temperature, humidity, and carbon dioxide and nitrogen oxides availability), soil conditions, tree species, tree age, and stored carbohydrates in the trees. The width and density of tree rings are dependent on many confounding factors, making isolation of the climatic temperature signal uncertain. It is usually the case that width and density of tree rings are monitored in conjunction in order to more accurately use them as climate proxies. Ice cores are the accumulation of snow and ice over many years that have recrystallized and have trapped air bubbles from previous time periods. The composition of these ice cores, especially the presence of hydrogen and oxygen isotopes, provides a picture of the climate at the time. The relative concentrations of the heavier isotopes in the condensate indicate the temperature of condensation, allowing for ice cores to be used in global temperature reconstruction. In addition to the isotope concentration, the air bubbles trapped in the ice cores allow for measurement of the atmospheric concentrations of trace gases, including greenhouse gases carbon dioxide, methane, and nitrous oxide.]

Sample Proxy Series

FIGURE 2

Some examples of tree ring proxy series are given in Figure 2. Most of the proxy series show little structure, but the last two show the characteristic 'hockey stick' shape. The principal component-like methodology in MBH 98/99 preferentially emphasizes these shapes as we shall see.

Principal component analysis methodology is at the core of the MBH98/99 analysis methodology. Principal component analysis is a statistical methodology often used for reducing datasets with many variables into datasets with fewer, but composite variables. The time series proxy data involved are transformed into their principal components, where the first principal component is intended to explain most of the variation present in the data variables. Each subsequent principal component explains less and less of the variation. In the methodology of MBH98/99, the first principal component is used in the temperature reconstruction.

Two principal methods for temperature reconstructions have been used; CFR (climate field construction used in MBH98/99) and CPS (climate-plus-scale). The CFR is essentially the principal component based analysis and the CPS is a simple averaging of climate proxies. The controversy of the MBH98/99 methods lies in that the proxies are incorrectly centered on the mean of the period 1902-1995, rather than on the whole time period. The proxy data exhibiting the hockey stick shape are actually decentered low. The updated MBH99 reconstruction is given in Figure 3. This fact that the proxies are centered low is apparent in Figure 3 because for most of the 1000 years, the reconstruction is below zero. Because the 'hockey stick' proxies are centered too low, they will exhibit a larger effective 'variance', allowing the method to exhibit a preference for selecting them as the first principal component. The net effect of this decentering using the proxy data in MBH98 and MBH99 is to produce a 'hockey stick' shape. Centering on the overall mean is a critical factor in using the principal component

Top Panel is the MBH98 reconstruction
Bottom Panel is the centered PCA reconstruction

FIGURE 4

To illustrate this, we consider the North America Tree series and apply the MBH98 methodology. The top panel shows the result from the de-centering. The bottom panel shows the result when the principal components are properly centered. Thus the centering does make a significant difference to the reconstruction.