QUESTIONS SURROUNDING THE 

‘HOCKEY STICK’ TEMPERATURE 

STUDIES: IMPLICATIONS FOR 

CLIMATE CHANGE ASSESSMENTS 

HEARINGS 

BEFORE THE 

SUBCOMMITTEE ON OVERSIGHT AND 

INVESTIGATIONS 

OF THE 

COMMITTEE ON ENERGY AND 

COMMERCE 

HOUSE OF REPRESENTATIVES 

ONE HUNDRED NINTH CONGRESS 

SECOND SESSION 

JULY 19 AND JULY 27, 2006 

Serial No. 109-128 

Printed for the use of the Committee on Energy and Commerce 

Available via the World Wide Web: http://www.access.gpo.gov/congress/house 

U.S. GOVERNMENT PRINTING OFFICE 

WASHINGTON : 2006 

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Internet: bookstore.gpo.gov Phone: toll free (866) 512-1800; DC area (202) 512-1800 

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31-362PDF 
COMMITTEE ON ENERGY AND COMMERCE 

JOE BARTON, Texas, Chairman 

RALPH M. HALL, Texas 

MICHAEL BILIRAKIS, Florida 

 Vice Chairman 

FRED UPTON, Michigan 

CLIFF STEARNS, Florida 

PAUL E. GILLMOR, Ohio 

NATHAN DEAL, Georgia 

ED WHITFIELD, Kentucky 

CHARLIE NORWOOD, Georgia 

BARBARA CUBIN, Wyoming 

JOHN SHIMKUS, Illinois 

HEATHER WILSON, New Mexico 

JOHN B. SHADEGG, Arizona 

CHARLES W. “CHIP” PICKERING, Mississippi 

 Vice Chairman

VITO FOSSELLA, New York 

ROY BLUNT, Missouri

STEVE BUYER, Indiana 

GEORGE RADANOVICH, California 

CHARLES F. BASS, New Hampshire 

JOSEPH R. PITTS, Pennsylvania 

MARY BONO, California 

GREG WALDEN, Oregon 

LEE TERRY, Nebraska 

MIKE FERGUSON, New Jersey 

MIKE ROGERS, Michigan 

C.L. “BUTCH” OTTER, Idaho 

SUE MYRICK, North Carolina 

JOHN SULLIVAN, Oklahoma 

TIM MURPHY, Pennsylvania 

MICHAEL C. BURGESS, Texas 

MARSHA BLACKBURN, Tennessee 

JOHN D. DINGELL, Michigan 

 Ranking Member 

HENRY A. WAXMAN, California 

EDWARD J. MARKEY, Massachusetts 

RICK BOUCHER, Virginia 

EDOLPHUS TOWNS, New York 

FRANK PALLONE, JR., New Jersey 

SHERROD BROWN, Ohio 

BART GORDON, Tennessee 

BOBBY L. RUSH, Illinois 

ANNA G. ESHOO, California 

BART STUPAK, Michigan 

ELIOT L. ENGEL, New York 

ALBERT R. WYNN, Maryland 

GENE GREEN, Texas 

TED STRICKLAND, Ohio 

DIANA DEGETTE, Colorado 

LOIS CAPPS, California 

MIKE DOYLE, Pennsylvania 

TOM ALLEN, Maine 

JIM DAVIS, Florida 

JAN SCHAKOWSKY, Illinois 

HILDA L. SOLIS, California 

CHARLES A. GONZALEZ, Texas 

JAY INSLEE, Washington 

TAMMY BALDWIN, Wisconsin 

MIKE ROSS, Arkansas 

BUD ALBRIGHT, Staff Director 

DAVID CAVICKE, General Counsel

REID P. F. STUNTZ, Minority Staff Director and Chief Counsel

SUBCOMMITTEE ON OVERSIGHT AND INVESTIGATIONS 

ED WHITFIELD, Kentucky, Chairman 

CLIFF STEARNS, Florida 

CHARLES W. “CHIP” PICKERING, Mississippi 

CHARLES F. BASS, New Hampshire 

GREG WALDEN, Oregon 

MIKE FERGUSON, New Jersey 

MICHAEL C. BURGESS, Texas 

MARSHA BLACKBURN, Tennessee 

JOE BARTON, Texas 

 (EX OFFICIO)

BART STUPAK, Michigan 

 Ranking Member 

DIANA DEGETTE, Colorado 

JAN SCHAKOWSKY, Illinois 

JAY INSLEE, Washington 

TAMMY BALDWIN, Wisconsin 

HENRY A. WAXMAN, California 

JOHN D. DINGELL, Michigan 

 (EX OFFICIO)

(II)
CONTENTS 

Page 

Hearings held: 

July 19, 2006 ...................................................................................................................... 1 

July 27, 2006 ...................................................................................................................... 603 

Testimony of: 

Wegman, Dr. Edward J., Center for Computational Statistics, George Mason 

University ...................................................................................................................... 39 

North, Dr. Gerald R., Department of Atmospheric Sciences, Texas A&M University..... 52 

Karl, Dr. Thomas R., Director, National Climatic Data Center, National Oceanic and 

Atmospheric Administration, U.S. Department of Commerce ..................................... 127 

Crowley, Dr. Thomas J., Nicholas Professor of Earth Science, Duke University ............. 138 

von Storch, Dr. Hans, Director of Institute for Coastal Research, GKSS Research 

Center, Germany ............................................................................................................ 215 

McIntyre, Stephen, Toronto, Ontario, Canada.................................................................... 236 

Mann, Dr. Michael E., Associate Professor and Director, Earth System Science 

Center, The Pennsylvania State University ................................................................... 640 

Christy, Dr. John R., Professor and Director, Earth System Science Center, NSSTC, 

University of Alabama in Huntsville ............................................................................. 654 

Cicerone, Dr. Ralph J., President, National Academy of Sciences .................................... 674 

McIntyre, Stephen, Toronto, Ontario, Canada.................................................................... 682 

Gulledge, Dr. Jay, Senior Research Fellow, Pew Center on Global Climate Change ....... 696 

Wegman, Dr. Edward J., Center for Computational Statistics, George Mason 

University ...................................................................................................................... 705 

Additional material submitted for the record: 

North, Dr. Gerald R., Department of Atmospheric Sciences, Texas A&M University, 

response for the record ................................................................................................... 586 

Crowley, Dr. Thomas J., Nicholas Professor of Earth Science, Duke University, 

response for the record ................................................................................................... 585 

Mann, Dr. Michael E., Associate Professor and Director, Earth System Science 

Center, The Pennsylvania State University, response for the record ............................ 764 

Christy, Dr. John R., Professor and Director, Earth System Science Center, NSSTC, 

University of Alabama in Huntsville, response for the record...................................... 770 

Cicerone, Dr. Ralph J., President, National Academy of Sciences, response for the 

record.............................................................................................................................. 780 

McIntyre, Stephen, Toronto, Ontario, Canada, response for the record ............................ 784 

Wegman, Dr. Edward J., Center for Computational Statistics, George Mason 

University, response for the record................................................................................ 829 

(III) 

(1) 

QUESTIONS SURROUNDING THE 

‘HOCKEY STICK’ TEMPERATURE 

STUDIES: IMPLICATIONS FOR CLIMATE 

CHANGE ASSESSMENTS 

WEDNESDAY, JULY 19, 2006 

HOUSE OF REPRESENTATIVES, 

COMMITTEE ON ENERGY AND COMMERCE, 

SUBCOMMITTEE ON OVERSIGHT AND INVESTIGATIONS, 

Washington, DC. 

The subcommittee met, pursuant to notice, at 10:07 a.m., in Room 

2123 of the Rayburn House Office Building, Hon. Ed Whitfield 

(Chairman) presiding. 

 Members present: Representatives Walden, Bass, Stearns, Burgess, 

Blackburn, Barton (ex officio), Stupak, Schakowsky, Inslee, Baldwin, 

Waxman, and Whitfield. 

 Staff present: Mark Paoletta, Chief Counsel for Oversight and 

Investigations; Peter Spencer, Professional Staff Member; Tom Feddo, 

Counsel; Matt Johnson, Legislative Clerk; Mike Abraham, Legislative 

Clerk; Ryan Ambrose, Legislative Clerk; David Vogel, Minority 

Research Assistant; Chris Knauer, Minority Investigator; Lorie Schmidt, 

Minority Counsel; and Edith Holleman, Minority Counsel. 

 MR. WHITFIELD. I call this hearing to order this morning. 

 Albert Gore’s first movie, or documentary, entitled “An 

Inconvenient Truth” is the most recent of many topics in years and years 

of focus on the subject of global warming, and 95 percent of the 

American people certainly are familiar with the term “global warming” 

and they know basically what it means, I would think. However, 95 

percent of the American people and certainly 95 percent of the Members 

of the U.S. Congress have not had the time to examine the data used by 

scientists, paleoclimatologists, and statisticians nor do they have the 

inclination to do so, to look at that data that is used to predict the 

probability that the temperature of one century is warmer or cooler than 

that of another century. 

 Now, the United Nations Intergovernmental Panel on Climate 

Change is the world body with most of the interest and does focus on this 

subject of global warming. And it is the body that most people look to 

on this subject. Now, for many years the Intergovernmental Panel on 

Climate Change used a chart that clearly shows the temperature from 
2

1000 A.D. to about 1450 A.D., that the temperatures during that period 

were significantly warmer than the latter part of the 20th Century, or the 

late 1990s. Now, in 1998 and 1999, a paleoclimatologist, Dr. Michael 

Mann, with Raymond Bradley and Dr. Malcolm Hughes, introduced a 

new technique to develop more quantitative estimates of the nature of 

climate change since 1000 A.D. and concluded that the late 20th Century 

was the warmest in 1,000 years, that the warming during the late 1990s 

was the warmest in over 1,000 years. Now, as a result of that report, the 

IPCC incorporated the study with other data which eliminated the 

warming period for 1000 A.D. to 1450 A.D. and incorporated a new 

graph referred to as the “hockey stick” graph, which shows remarkable 

warming in the late 1990s. Now, when Chairman Barton and I wrote a 

letter asking that the Mann report be reviewed by some statisticians, 

there was a hue and cry around the country among many people in the 

news media that we were being totally political, that all we were trying to 

do was gut this issue that global warming is occurring. But I think quite 

sincerely that we have a responsibility when public policy decisions 

being made on reports like the Mann report and others have such a broad 

impact on so much of our society and certainly the Kyoto arguments 

were primarily based on this new chart, that the U.S. should be part of 

Kyoto. That was an important part of that. And so what we did was, we 

asked that Dr. Wegman and a team that he had review these data. Now, 

when we did that, Sherry Boehlert, who is a good Republican friend of 

ours and is Chairman of the Science Committee, was quite upset about it 

and he said I think you all are being political also, and he asked that we 

ask Dr. North, who is going to be a witness, and would like for him to be 

involved in this data analysis, and he is going to be a witness today also. 

But the real purpose of this is that this issue is so important that I think it 

is imperative that we hear from all sides and try to get some real 

understanding of the strengths and weaknesses of these reports. 

 Now, Dr. Wegman is going to testify today that the mathematics 

used by Mann is incorrect and wrong. Dr. North, I think on page five of 

his testimony, says that they have some concerns about it, the math. But 

the first witness today is going to be Dr. Edward Wegman, a statistician 

from George Mason University, and on his team was Dr. David Scott 

from Rice University and Dr. Yasmin Said from Johns Hopkins, and she 

is sitting behind him there. Dr. Wegman is Chairman of the National 

Academy of Sciences Committee on Applied and Theoretical Statistics, 

and at the committee’s request he assembled this ad hoc committee of 

statisticians to examine the hockey stick studies and related articles and 

his committee report prepared for Chairman Barton and me and the 

committee and publicly released this Friday provides important findings 

for Congress and the public to consider about the soundness and 
3

openness of climate change research and assessment and I can tell you 

right now that his document has been peer reviewed also, and we will get 

into that later. 

 In addition to Dr. Wegman, we have Dr. Gerald North of Texas 

A&M University, who will testify on the first panel about the current 

state of historical temperature understanding. Dr. North chaired a recent 

National Research Council panel on historical temperature 

reconstructions and we look forward to hearing his perspective for 

improving climate change assessments. And to help us understand some 

particulars of the IPCC process, we will hear testimony on the second 

panel from Dr. Thomas Karl, who is a coordinating author of the chapter 

upon which Dr. Mann and his colleagues worked. Dr. Thomas Crowley 

of Duke University will be here and Dr. Hans von Storch, who traveled 

from Germany to be with us this morning. Both will provide their views 

concerning the questions about the hockey stick study as well as 

questions concerning data sharing, transparency and the IPCC process. 

 Finally, I would like to welcome Mr. Stephen McIntyre, who will 

testify about attempting to understanding just what was behind the 

hockey stick graphic promoted by the IPCC. His work is a testament to 

the value of open debate and scrutiny. 

 Now, I have talked about Dr. Mann and we invited Dr. Mann to be 

here today and he was unable to be here. We are extending another 

invitation for him to come and hope that maybe he will be here next 

week. Now, even though Dr. Mann could not come, he specifically 

asked us to request Dr. Crowley to testify on his behalf and Dr. Crowley 

is with us today from Duke University, and we look forward to his 

testimony. But as I said, the real purpose of this hearing is, let us just 

open the book. Let us look at everything. Let us look at the criticisms of 

all parties and see exactly where we are on this important issue of global 

climate change. 

 [The prepared statement of Hon. Ed Whitfield follows:] 

PREPARED STATEMENT OF THE HON. ED WHITFIELD, CHAIRMAN, SUBCOMMITTEE ON 

OVERSIGHT AND INVESTIGATIONS

Good morning and welcome. We convene this hearing today to consider questions 

that begin with and surround the reliability of two particular studies of historical 

temperatures that gained an extraordinary level of public prominence a few years ago, 

and recently featured in former Vice President Al Gore’s motion picture, “An 

Inconvenient Truth.” 

In 2001, the results of these studies were used to promote the view that the very 

recent average temperatures of the northern hemisphere were likely the warmest in 1,000 

years. The temperature history results were portrayed in what is widely known as the 

‘hockey stick’ graph, for its resemblance to the shape of a hockey stick. As a result, these 

studies are known as the “hockey stick” studies. 
4

With its relatively long and even trend for 900 years and then sharp up-tick during 

the 20th Century, the “hockey stick” graph effectively undermined what had been the 

prevailing view that we had experienced periods of similar or even higher average 

temperatures in the past – such as when the Vikings inhabited Greenland. 

The fact that the United Nation’s Intergovernmental Panel on Climate Change, or 

IPCC, prominently relied upon the graph lent the graph its apparent authority. The IPCC 

is an influential international body that conducts scientific assessments for use by 

policymakers. 

The graph offered a simple and powerful message for the public and policymakers 

to understand. It was also a message that some say may have been based on faulty 

methodology. The “hockey stick” studies formed the basis for the IPCC finding in 2001 

that the 1990s were likely the warmest decade of the millennium and 1998 likely the 

warmest year during that time. Some of today’s witnesses will describe in detail that the 

“hockey stick” studies were critically flawed and could not support the findings reached 

by these studies. 

Had the ‘hockey stick’ studies remained in the niche of climate change journals, we 

would not be holding this hearing. Instead, we are here because the questions 

surrounding these studies relate directly to the strength of the findings in the first place. 

What does the “hockey stick” story say about the reliability of these studies for 

policymakers? 

Last summer, Chairman Barton and I inquired into this matter after we learned that 

the lead author of these federally funded studies – Dr. Michael Mann -- to share the 

computer code he used to generate his results with researchers who sought to replicate the 

result of Mann’s studies. The researchers, one of whom will testify today, reportedly 

could not replicate his work based on what the study said. The researchers nevertheless 

identified several methodological and data problems with the work. 

How critical were these problems identified by these researchers? Were the 

problems undetected because Dr. Mann assessed his own work in an IPCC report? 

These are serious questions, and the answers contain broad implications for global 

policy on climate change. We should ensure that science is providing us with reliable, 

balanced, well-considered, and unbiased answers. 

Today, our witnesses will help us address these critical questions. 

I want to welcome, especially, Dr. Edward Wegman, a statistician with George 

Mason University, who will lead off the first panel this morning. Dr. Wegman is 

Chairman of the National Academy of Sciences Committee on Applied and Theoretical 

Statistics. At the Committee request, Dr. Wegman assembled an ad-hoc committee of 

statisticians to examine the hockey stick studies and related articles. His committee’s 

report, prepared for Chairman Barton and me and publicly released this past Friday, 

provides important findings for Congress – and the public – to consider about the 

soundness and openness of climate change research and assessments. The Wegman 

Committee not only identified fundamental flaws in the “hockey stick” studies, it also 

addressed the larger point that climate change studies, like any work with potentially 

large policy implications, must be subject to careful and broad scrutiny. 

Dr. Wegman and his team performed their work completely independent of the 

Committee and without charge. I believe Dr. Wegman’s team has done a great public 

service and their work should help us improve how we discuss climate change when 

crafting policy. 

Additionally, Dr. Gerald North, of Texas A&M University, will testify on the first 

panel about the current state of historical temperature understanding. Dr. North chaired a 

recent National Research Council panel on historical temperature reconstructions, and I 

look forward to hearing his perspective for improving climate change assessments. 

To help us understand some particulars of the IPCC process, we’ll hear testimony on 

the second panel from Dr. Thomas Karl, who was a coordinating author of the chapter 
5

upon which Dr. Mann and his colleagues worked. Dr. Thomas Crowley, of Duke 

University, and Dr. Hans von Storch – who traveled from Germany to be with us this 

morning – both can provide their considered views concerning the questions about the 

“hockey stick” studies, as well as questions concerning data sharing, transparency, and 

the IPCC process. 

Finally, I’d like to welcome Mr. Steven McIntyre. Mr. McIntyre will testify about 

attempting to understand just what was behind the hockey stick graphic promoted by the 

IPCC. His examination of the facts underlying the assessments’ claims really initiated 

some of the important questions concerning the scrutiny provided by climate change 

assessments. His work is a testament to the value of open debate and scrutiny. His 

perseverance should be commended. 

Let me add that we did invite Dr. Mann to this hearing, but his attorney explained 

that he was unavailable, on family vacation. Dr. Mann suggested Dr. Crowley could 

come in his place. We do hope to have Dr. Mann at a future hearing, however. 

At the end of the day, the issues of climate change require open and objective 

discussion. Some of the work we’ll consider today points to the value of policy decisions 

that are informed by sound science and objective advice. 

I’ll now yield to Mr. Stupak, our ranking member, for his opening statement. 

 MR. WHITFIELD. At this time, I would like to recognize Mr. Stupak 

of Michigan for his opening statement. 

 MR. STUPAK. Thank you, Mr. Chairman. 

 It is a little bewildering to me why the committee is holding its very 

first hearing on global warming to referee a dispute over a 1999 hockey 

stick graph of global temperatures for the past millennium. Mr. 

Chairman, in your opening statement you claim that Dr. Mann’s hockey 

stick report of 1999 was the basis for the Kyoto Accord. According to 

my recollection, Kyoto was in 1997, so it could not have been the basis 

for the Kyoto Accord. 

 So as we will hear at this hearing today, global warming science has 

moved on since Dr. Mann put forth his study in 1999. Dr. Mann, who 

did this study, has made changes and even such diehard opponents as 

President Bush now actually admit that global warming exists and must 

be addressed. Congress is particularly ill-suited to decide scientific 

debates. There has been no attempt by this committee to obtain an 

unbiased view of the work done by Dr. Michael Mann, the author of the 

hockey stick research. Dr. Mann, who has done additional work with his 

methodology since 1999, is not even here to confront his critics because 

the Majority would not even postpone this hearing until Dr. Mann could 

be available. Moreover, it was known from the beginning that Dr. Mann 

used a new methodology and proxy material to reconstruct temperatures. 

 Paleoclimatologists, those who try to reconstruct ancient climates, 

are not working with instrumental measurements of temperature as we 

have today. Paleoclimatologists are looking at tree rings, ice cores, bore 

heads and historical records to attempt to determine what happened in an 

earlier time. That is all the research materials paleoclimatologists have 

and it is an admittedly imprecise science. It should not surprise us if the 
6

initial work in a new field can be improved. What should surprise us is 

that Dr. Wegman’s report focuses on critiques of Dr. Mann’s first work 

in 1998 and 1999, even though the field of large-scale temperature 

reconstruction has advanced since that time. 

 The Majority paid for a report to independently verify the critiques 

of Dr. Mann’s 1999 research by a statistician but without any input from 

a climatologist. The Majority left it to the Science Committee to ask the 

National Academy of Sciences to do a full review of all the science 

represented. The Majority made no effort to verify whether the patterns 

in global temperatures detected in the Mann study were valid or 

coincided with conclusions of other researchers in global warming. 

 It is now 7 years since the original work was published and much 

additional work has been done by Dr. Mann and others. As we will hear 

from Dr. North, who chaired the NAS study, the patterns were verified 

with certainty for recent years but less certain for the years 1000 to 1600 

A.D. That is to be expected because there is less data from this long ago 

era. Dr. Wegman has an eminent background in statistics and he 

believes that statisticians should be included in the research teams of all 

these studies because statisticians can make studies better. Perhaps they 

can. Dr. Wegman says Dr. Mann didn’t center his data properly. 

Perhaps he didn’t. But we note that Dr. Wegman’s work is not yet 

published or peer reviewed so it is very difficult for us to evaluate his 

work. Dr. Wegman’s criticism of Dr. Mann should have been 

interdisciplinary and include a statistician can also be said of Dr. 

Wegman’s work. Dr. Wegman did not have a climate scientist on his 

team. However, Dr. Wegman has decided to go beyond his statistical 

expertise to hypothesize that Dr. Mann was allowed to publish and 

defend his work because of the small “social network” of 

paleoclimatologists who work with each other and protect each other. I 

want to emphasize that this is simply a hypothesis. Mr. Chairman, 

whatever the purpose of this hearing is, it is not to hypothesize about the 

impact of professional scientific relationships on research unless we have 

some hard objective evidence. 

 We in Washington know all about undue influence on government 

scientists. A political appointee at NASA just recently tried to keep 

James Hanson, a veteran atmosphere scientist, from discussing the dire 

consequences of global warming by threatening dire consequences to Mr. 

Hanson’s employment status. The science content has been changed on 

NASA and other government websites because it didn’t fit the 

Administration’s world view. This fact ought to be of much more 

interest to this committee, the Oversight and Investigations Committee, 

than hypothesis about scientific social networking. 
7

 And with that, Mr. Chairman, I would yield back the balance of my 

time. 

 MR. WHITFIELD. Mr. Stupak, thank you. I also want to thank you 

for pointing out an incorrect statement that I made. I said something 

about the hockey stick being the impetus for Kyoto. Kyoto certainly 

started way before the hockey stick but the hockey stick graph did add 

impetus to the argument for the adoption of Kyoto, so I want to thank 

you for that. Also, I would point out that the committee did not pay Mr. 

Wegman for this report, we simply contacted him asking him to review 

it. 

 At this time I recognize the full committee Chairman, Mr. Barton. 

 CHAIRMAN BARTON. Thank you, Mr. Chairman. I have a written 

statement, I am going to use some of it, but I want to speak 

extemporaneously briefly based on what my good friend from Michigan, 

Mr. Stupak, just said. 

 The purpose of oversight and investigation is to do exactly that, to 

oversee the jurisdictional issues before this committee and when it seems 

to be called for to investigate issues that arise because of the oversight. 

There has been a disagreement for a number of years in the community 

at large about the issue of global warming. In this Congress, there has 

been a disagreement between the Chairman of the Science Committee 

and myself about that issue. That is normal and that is not anything that 

is a negative. But there were some statements made about a specific 

report by a number of people that basically use that report to come to the 

conclusion that global warming was a fact and that the 1990s was the 

hottest decade on record and that one year, 1998, was the hottest year in 

the millennium. Now, a millennium is a thousand years. That is a pretty 

bold statement. So Chairman Whitfield and myself decided, let us take 

this report that is the basis for many of these conclusions and has been 

circulated widely and once it is in the mainstream, it is stipulated that 

because of that, everything else follows and let us see if it can be 

replicated. Let us see if in fact the facts as purported in that report are in 

truth the facts. 

 Now, I have not seen Dr. Wegman until I walked in this room. I 

have not talked to him on the phone or in person or any of his 

collaborators. I may have seen Dr. North at Texas A&M since I went to 

Texas A&M. I don’t recall it but it is possible. He has got enough white 

in his hair that I could have been one of his students and I wouldn’t 

remember it, so I can’t stipulate that I have never met him but I can 

stipulate that I have never met Dr. Wegman. We asked to find some 

experts to try to replicate Dr. Mann’s work. Now, to their credit, when 

Dr. Wegman agreed to do it, he asked for no compensation. I don’t think 

we have even paid him for the fax paper that he has used. He picked 
8

some eminent statisticians in his field and they studied this thing. Had 

their report said Dr. Mann’s data can be replicated, his conclusions are 

right on point, he is totally correct, we would have reported that, but that 

is not what they said. Now, I took statistics at Texas A&M and I also 

took them in graduate school. I made A’s and B’s, but I really didn’t 

understand it but I kind of understand it. And according to Dr. Wegman, 

Dr. Mann made a fundamental error. He decentered the data. Now, to 

the average person, that doesn’t mean squat. What does “decentered the 

data” mean? What it means apparently is, he moved it off center a little 

bit by enough that it really makes a difference and then using some 

statistical techniques that instead of looking at all the variables and in a 

complex system like climate you are going to have lots of variables, he 

chose one or two as the principal variables and used those to explain 

everything else, and Dr. Wegman and his colleagues who as far as I 

know have got no axe to grind, have said the Mann study is flat wrong. 

Now, it may be wrong just kind of unintentionally. Dr. Wegman doesn’t 

say there is any intent to deceive but he says it is flat wrong. Now, if that 

is not the purpose of the Oversight Subcommittee of the Energy and 

Commerce Committee that has got jurisdiction over energy and 

environmental policy for the United States of America, then I don’t know 

what this subcommittee should be doing. 

 So I want to thank Dr. Wegman and his colleagues for giving us an 

unvarnished, flat out non-political report. Now, admittedly, that report is 

going to be used probably for political purposes but that is not what he 

did, and I want to thank Dr. North for the work that he did in this 

document. Now, it is a lot thicker than Dr. Wegman’s document, and Dr. 

North and his colleagues have kind of looked at the same subject and 

they have come to a somewhat little--they are little bit more, I don’t want 

to use the technical term wishy-washy but they are kind of on both sides 

of it, but even Dr. North’s report says that the absolute basic conclusion 

in Dr. Mann’s work cannot be guaranteed. This report says it is 

plausible. Lots of things are plausible. Dr. Wegman’s report says it is 

wrong. 

 Now, what we are going to do after today’s hearing, we are going to 

take Dr. Wegman’s report, and if my friends on the Minority want to 

shop it to their experts, so be it. We are going to put it up there, let 

everybody who wants to, take a shot at it. Now, my guess is that since 

Dr. Wegman came into this with no political axe to grind, that it is going 

to stand up pretty well. If Dr. Mann and his colleagues are right, their 

conclusion may be right--Dr. Mann’s conclusion may be right but you 

can’t verify it from his statistics in his model so if Dr. Mann’s conclusion 

is right, it is incumbent upon him and his colleagues to go back, get the 
9

math right, get the data points right, get the modeling right. That is what 

science is about. 

 So I want to thank you, Mr. Chairman, for holding this hearing. I am 

planning to participate fully and extensively. I have got a whole series of 

questions. I stayed up half the night studying all the various documents 

so I hope that by the end of today we can shed some light on a subject 

that is very, very important to the future economic and health 

consequences for this country. Thank you, sir. 

 [The prepared statement of Hon. Joe Barton follows:] 

PREPARED STATEMENT OF THE HON. JOE BARTON, CHAIRMAN, COMMITTEE ON ENERGY 

AND COMMERCE

Thank you, Chairman Whitfield. Today’s hearing on the hockey stick temperature 

studies will show why we need to question the quality of climate assessments for policy 

makers. 

This Committee frequently confronts some of our Nation’s most consequential 

public policy questions affecting the quality of human health, our economy, and our 

environment. However, no issue we deal with has more potential to affect the American 

people than climate change. 

Meanwhile, the compounding costs to the U.S. economy posed by some proposals 

for reducing greenhouse gas emissions could rock our economy, drive manufacturing offshore, and spike domestic consumer energy costs. 

That is why we need to be sure that we have a solid factual basis for whatever 

decisions we make in this area. 

The report we are about to receive indicates that the social and statistical 

underpinnings of key climate-change work are prone to produce error. 

I look forward to hearing from all of our witnesses because we have important work 

to accomplish today. I would especially like to thank Dr. Edward Wegman who, on his 

own time and his own expense, assembled a pro bono committee of statisticians to 

provide us with independent and expert guidance concerning the hockey stick studies and 

the process for vetting this work. 

Dr. Wegman and his committee have done a great public service. Their report, with 

clear writing and measured tone, has identified significant issues concerning the 

reliability of some of the climate change work that is transmitted to policymakers and 

characterized as well scrutinized. The Wegman Committee report will be the centerpiece 

of today’s hearing. 

These ‘hockey stick’ studies were the linchpin for what became widely acclaimed as 

the consensus view of the earth’s temperature history during the past thousand years. It 

was presented as part of the leading climate assessment for public policy makers around 

the world – the United Nation’s Intergovernmental Panel on Climate Change, or IPCC. 

Both good science and good public policymaking demand that scientific work 

withstand independent and impartial scrutiny. Information that is not scientifically sound 

is just not acceptable. Indeed, it appears that some of the authors of the IPCC assessment 

dealing with global temperature history were not independent or impartial. They also 

happened to be the authors of the hockey stick studies, themselves. The researchers then 

declined to provide the information necessary to replicate their work, a fundamental 

failure in reliable science. 

The “hockey stick” studies were supported by Federal grants and were central to a 

prominent finding in an influential assessment. In my view, if Congress is going to make 
10

policy decisions based on the authority of climate change assessments, we cannot fail to 

wonder how they have been formulated. Asking questions is at the core of what we do. 

Our central question is: Can we count on hockey stick studies? That answer from 

Dr. Wegman and his panel appears to be, “No.” And it doesn’t appear to be a matter of 

overlooking the researchers’ written caveats about their particular work; rather, the 

Wegman panel has identified a fundamental error of methodology. If that finding holds 

up, it will highlight a mistake that lay dormant for years as a closed network of 

supportive colleagues saw and heard what it wanted. It took scientists outside the network 

to identify the core problems, both in the studies and in the IPCC assessment. 

Congress is in the business of making policy decisions that affect the lives of real 

people. Science provides us with the answers to many policy questions, and we need to 

trust it. I do trust science, and I trust it most when it is transparent, open to question, and 

eager to explain. When research is secretive, automatically and aggressively defensive, 

and self-reinforcing, it becomes easy to distrust. 

As Chairman of the Energy and Commerce Committee, which holds a key role in 

any policy making relating to climate change, I believe it is incumbent on this Committee 

must ensure that the very best information is available to make its decisions. 

Caveats and uncertainty are facts of life, and not only in science. We deal with 

complicated science and research-based decisions and uncertainty in every area of our 

jurisdiction. Some of the most troubling work we confront – on bioterror or radiological 

risks for example – present very tough and complicated issues for us to assess. 

Good science is built on healthy skepticism, and good scientists don’t hide from 

questions. They invite them. Asking questions to establish the validity of scientific 

studies – especially those with enormous policy implications – is why we are here today. 

The caveats and uncertainty are never going to be eliminated, but we would like to know 

whether the facts or caveats contained in these sophisticated climate assessments have 

been adequately and independently scrutinized. 

Heads-I-win, tails-you-lose science can produce any answer that is desired, but 

that’s hardly the way to make multi-billion-dollar decisions. This is a vitally important 

matter. When we deal with global warming, we need to know that the underlying studies 

constitute reliable science. The taxpayers depend on it. My grandchildren depend on it. 

The planet depends on it. 

I want to extend my thanks to all the witnesses for appearing today, and I look 

forward to their testimony. 

 MR. WHITFIELD. Thank you, Mr. Chairman. At this time I 

recognize Mr. Inslee of Washington. 

 MR. INSLEE. Thank you, Mr. Chairman. 

 America is fully capable of dealing with global warming but not if 

Congress engages in snipe hunts, arguments about how many 

statisticians can dance on the head of a pin rather than figuring out what 

our energy policy should be to get a handle on global warming. 

 Now, why are we in this exercise for doubt? I refer you to the first 

slide I have, which is a memo from the tobacco industry when they were 

fighting the clear, unalloyed science that tobacco was bad for you. Here 

is a memo from one of their people: “Doubt is our product.” And those 

who decide that America should stay quiescent, do nothing about global 

warming, doubt is their product. 
11

Our 

Product Product 

is Doubt! is Doubt!

 Next slide. 

Why should we deal with this? What we are going to find out today, 

I hope, we can spend weeks debating the statistics behind one particular 
12

study but what we will find is that every single study ever that has looked 

at proxy data for temperature has indicated we are in a unique 

circumstance and carbon dioxide is going through the roof which you 

will see from these studies, multiple of which are on this slide. Next 

slide. 

Now

Time (thousands of years)

160 120 80 40

Temperature 

difference from 

now °C

CO2

concentration 

(ppmv)

The last

160,000 years 

and the next 

100 years

CO2 now 

CO2 in 2100

(with business

as usual)

Source:

Global Change 

Research Program

100

200

300

400

500

600

700

–10

0

10

Degrees Celcius

CO2 PPMV

 What we find now is that CO2 is going through the roof. No one in 

this room will say otherwise. The first bottom circle is where we are 

today. It is higher CO2 levels than any time in the last 160,000 years. 

Every single scientist in the world agrees to that fact, and by 2100 the 

circle on top, it will be almost twice as it has ever been in the last 

200,000 years. Every single scientist in the world agrees to that fact, and 

because CO2 drives climate, because it drives temperature, we ought to 

get out of this posture of the ostrich and assume the posture of the eagle 

to do something about global warming. Next slide, please. 
13

 I want to point out something that is very important in today’s 

discussion. We can spend years debating what the temperature was on 

July 18, 972, but what we ought to know is that our putting CO2 into the 

atmosphere is destroying the world’s oceans regardless of the 

temperature. The new science shows that the CO2 that we put in the 

atmosphere is acidifying the oceans. The oceans have 23 percent more 

hydrogen ions that create acidic conditions than any time ever that we 

know of in human history, at least. Next slide, please. 
14

 The result of that is that when the oceans become more acidic, it 

becomes much more difficult for any life including plankton, coral reefs, 

clams, oysters, you name it to form shells including plankton, which is 

the basis of the entire food chain of all the protein we get out of the 

oceans. Next slide, please. 
15

 What this shows is the pH level of acidity is changing. Next slide, 

please. 
16

So that by the year 2099, conditions in the ocean may not support 

any coral reefs healthy anywhere in the world. This doesn’t have 

anything to do with Dr. Mann’s report. Even if temperatures did not 

change one-half a degree, the oceans are becoming acidic that may not 

support the protein that we depend on in the world if we don’t act and if 

this committee continues to act like an ostrich. Next slide, please. 

 Why are Americans rejecting this doubt they see with their own 

eyes? Polar icecaps shrunk in density--next slide, please--in the last 12 

years. 
17

Greenland is melting at unprecedented rates. Next slide, please. 
18

The polar icecap has shrunk 20 percent in the summer. The red line 

shows where it used to be. The white is where it is now. Next slide, 

please. We have run out of slides. Well, maybe I ought to talk then. 

 This is very disturbing to me that when the entire world scientific 

community has reached a conclusion with high levels of certainty that 

carbon dioxide is going to astrospheric levels, unprecedented in world 

history, and that when we know beyond a shadow of a doubt the levels of 

carbon dioxide ultimately will drive temperature changes to areas we do 

not want to see, that instead of really engaging Congressional talent in 

figuring out how to deal with this problem, we try to poke little pinholes 

in one particular statistical conclusion of one particular study where the 

overwhelming evidence is that we have to act to deal with this global 

challenge. 

 It is not fitting for this Congress, America that should lead the 

technology that drives the energy future of the world, to sit here to ask 

these fine statisticians to go into mind-numbing detail about whether this 

particular year was hotter than it was in 980. I don’t care whether this 

year or yesterday was the hottest day. It was pretty hot here yesterday, 

but I don’t care whether it may have been hotter in 980. What I care 

about is whether there will be snow in the mountains for my kids and 

grandkids to ski on 50 years from now, and there is not going to be 

unless this Congress pulls its head out of the sand and acts. 

 So I look forward to the day that we have a Congress that will adopt 

the position that we need to deal with technology rather than statistical 

recreations of the tobacco industry’s effort to create doubt. Thank you. 

 MR. WHITFIELD. Mr. Bass. 

 MR. BASS. Thank you, Mr. Chairman, and thank you for holding 

this hearing. 

 I want to start by saying that in my opinion, there is absolutely 

nothing inappropriate about the subject of this hearing, and although the 

data may be mind-numbing, nonetheless there are those--I am probably 

not one of them--who really get into going through the data and the 

details and so forth to try to figure out what the problem is. Ultimately, 

the issue underlying the hearing today and any others that we have is not 

going to be about math, it is going to be about the effect of the extraction 

of enormous quantities of hydrocarbons from the middle of the Earth and 

from underground and the combustion of those hydrocarbons and the 

resultant impact that that has, if any, on the climate of the world. 

 Now, in another life when I used to sell architectural panel products 

for buildings, I was often asked by a customer whether or not the panel 

that I was trying to sell passed the ASTM, American Society for Testing 

Materials, E84 test, and I always used to respond because, of course, we 

couldn’t afford to have that test conducted, I used to say well, it hasn’t 
19

but I subjected it to what I called the elephant foot test and I built--every 

fall I burned a huge pile of brush in my field on the farm I live on and 

one year I just took one of the panels that I planned to sell and I threw it 

on top of the pile and it sat there for 30 minutes and nothing happened. 

Is that satisfactory? Well, we can spend I think a productive period of 

time talking about the basis upon which the data was developed to 

determine the Mann report or the Wegman report or Dr. North’s report 

and so forth, but ultimately I think we need to recognize that there is a 

problem and anyone who denies the existence of any problem associated 

with the release of these hydrocarbons I think really needs--I want to be 

friendly about this--really needs to rethink that premise. There is 

something going on and I think finding out what that something is and 

then trying to debate a policy whereby we address that issue is 

constructive. 

 So I want to thank my friend from Kentucky for holding this hearing 

and I look forward to hearing the witnesses’ testimony, and I yield back. 

 MR. WHITFIELD. Thank you, Mr. Bass. At this time I recognize Mr. 

Waxman of California. 

 MR. WAXMAN. Thank you very much, Mr. Chairman. 

 The party that is in the majority selects the Chairman of the 

committees and the subcommittees and they can decide what priorities 

ought to be given to different issues and what hearings are to be called. 

Now, in the past 12 years, we have had study after study after study 

raising genuine concern about global warming and climate change. The 

Energy and Commerce Committee is a committee that has legislative 

jurisdiction over this issue. So for the past 12 years this committee has a 

very amazing record on this issue. This is only the second hearing in 12 

years. The first one was to look at the very intricate issue of modeling on 

predictions of climate change and this one is to look at studies from 1998 

and 1999 to see whether those studies are refuted by the work of the two 

gentlemen before us today. We have not held a hearing looking at what 

is the overwhelming scientific consensus that global warming is real and 

is caused by humans. We have not focused on some of the important 

recent scientific news on global warming such as a study showing that 

climate change is causing increased wildfires in the American West or 

the recent studies that show that global warming is leading to more 

intense hurricanes. 

 The committee could go a step further by examining the practical 

solutions that could begin to reduce our greenhouse gas emissions, and if 

the committee leadership wanted to conduct important and nonpartisan 

oversight, it could investigate why a former employee of ExxonMobil 

operated out of the Bush White House to sow doubt in government 

publications on global warming. Instead, this committee is doing what 
20

the deniers of global warming would have us do, ignore all the important 

questions and divert ourselves to a ridiculous effort to discredit a climate 

scientist and two studies he published eight years ago. 

 Chairman Barton began this dubious investigation in June of 2005 

when he sent a letter demanding the funding for every study that had 

ever been conducted by Dr. Michael Mann, demanding he turn over all 

of the data for all their research and made over burdensome and intrusive 

requests. The Washington Post accused our Chairman of conducting a 

witch hunt. The Chairman of the Science Committee, Sherwood 

Boehlert, called the investigation “misguided” and “illegitimate.” Well, 

oftentimes when we have scientific disputes we ask the National 

Academy of Sciences to review the matter. Instead of asking them--even 

though they offered their services to help resolve controversy--the 

Academy wasn’t called on by this committee but by Representative 

Boehlert’s committee and the Academy issued its report last month and 

they found that they largely upheld the findings of Dr. Mann. 

 So I have to submit that I don’t find this hearing to be one about 

truth. It is about sowing doubt and spreading disinformation, and I 

chaired all those committees over the years where I heard from tobacco 

executives who always insisted on having their scientists come in and 

say it is only coincidental that more cancers and other diseases seem to 

afflict smokers but there is no causal relationship. Not only is this 

hearing not legit in trying to deal with an important issue, it isn’t even 

fair. We are going to hear people attacking Dr. Mann but we are not 

going to have Dr. Mann here to confront the accusations against him. 

That is not science where you hear only one side. Science is hearing 

both sides, looking at the evidence, reaching conclusions based on the 

evidence. Dr. Mann was willing to testify before the committee but his 

schedule would not be accommodated. Global warming is an incredibly 

serious problem and this is not a serious hearing. 

 I would submit that if you have doubts, fine, but prudent people 

would start doing something in case your doubts on the Republican side 

of the aisle are wrong. We would start taking measures to reduce these 

greenhouse gas emissions that seem to be causing enormous damage to 

our planet and a threat to human life. Instead, we are looking at reports 

from 8 years ago and trying to debunk them. That is not an indication to 

me, that and the 12 years of inaction by this committee, that there is any 

interest on behalf of the Republican leadership to come to terms with 

what is not a partisan issue at all but one that is a very important issue for 

us to address. 

 [The prepared statement of Hon. Henry Waxman follows:] 
21

THE PREPARED STATEMENT OF THE HON. HENRY WAXMAN, A REPRESENTATIVE IN 

CONGRESS FROM THE STATE OF CALIFORNIA

Today, the Subcommittee holds only the second hearing on global warming in the 

Energy and Commerce Committee since the Republicans took over the House of 

Representatives in 1995. With so many important aspects to global warming and twelve 

years of virtual inaction, there's a lot of important work for the Committee to do. 

 It could start by highlighting the overwhelming scientific consensus that global 

warming is real and is caused by humans. Or it could focus on some of the important 

recent scientific news on global warming, such as the study showing that climate change 

is causing increased wildfires in the American West or the recent studies that show that 

global warming is leading to more intense hurricanes. 

 The Committee could go a step further by examining the practical solutions that can 

begin to reduce our green house gas emissions. And if it wanted to conduct important 

and non-partisan oversight, it could investigate why a former employee of ExxonMobil 

operated out of the Bush White House to sow doubt in government publications on global 

warming. 

 Instead, the Committee is doing exactly what the big oil companies hope for it to 

do...it ignores the important questions and diverts to a ridiculous effort to discredit a 

climate scientist and a study he published eight years ago. 

Chairman Barton began this dubious investigation when he wrote Dr. Michael Mann 

and several other researchers in June 2005. He demanded to know the source of funding 

for every study they had ever conducted, demanded they turnover all of the data for all of 

their research, and made other burdensome and intrusive requests. 

The Washington Post accused Chairman Barton of conducting a witch hunt. The 

Chairman of the House Science Committee Sherwood Boehlert called the investigation 

“misguided” and “illegitimate.” And the nation’s premiere science organizations quickly 

condemned the investigation. The American Association for the Advancement of 

Science wrote to Chairman Barton stating that his letters “give the impression of a search 

for some basis on which to discredit these particular scientists and findings, rather than a 

search for understanding.” 

The National Academy of Sciences also weighed in, stating that Chairman Barton’s 

approach was “intimidating” to researchers and offering the services of the Academy to 

help resolve the controversy. 

Ironically, it wasn’t Chairman Barton who took the Academy up on its offer. 

Instead, Rep. Boehlert requested the Academy report that was released last month. The 

Academy largely upheld the findings of Dr. Mann. 

This hearing isn’t about finding the truth. It’s about sowing doubt and spreading 

disinformation. The closest parallel is the decades-long campaign of the tobacco industry 

to deny that nicotine is addictive and cigarettes cause cancer. 

And the hearing isn’t even fair. Today we’re going to attack the work of Dr. Mann, 

but we’re not going to give Dr. Mann a chance to confront the accusations against him. 

Dr. Mann was willing to testify before the Committee, but his schedule was not 

accommodated and so he is going to be tried in absentia. 

Global warming is an incredibly serious problem, but this is not a serious hearing. 

It’s a diversion and a delaying tactic. And – worst of all – it is a missed opportunity to 

begin the process of protecting our children from the catastrophic effects of global 

warming. 

I know that the Chairman of this Subcommittee has never accepted the science about 

global warming. To bolster his argument over the years, he has repeatedly brought to the 

attention of the Committee, the views of Gregg Easterbrook and his book, “A Moment on 

the Earth.” 
22

So, I just want to make sure that the Chairman is aware of Mr. Easterbrook’s op-ed 

from May 26, 2006, in which Mr. Easterbrook announces that he has changed from “a 

skeptic to a convert.” He says that it is “case closed,” and that a strong scientific 

consensus shows that global warming “is a real phenomenon posing real danger.” 

I am glad that Mr. Easterbrook has revisited his views and corrected them 

accordingly. I hope the Chairman is willing to do the same. 

 MR. WHITFIELD. Dr. Burgess, you are recognized. 

 MR. BURGESS. Thank you, Mr. Chairman, for the recognition. I 

thank the Ranking Member for pointing out that partisanship has no 

place in this debate and I hope we won’t see it again this morning. 

 I will point out just for the record that Dr. Mann has been invited to 

appear before this committee before this hearing this morning. He 

couldn’t be here. Apparently he is on vacation that couldn’t be 

interrupted and maybe he can be here next week, and if he can be here 

next week, we will certainly be grateful to hear from him, but fortunately 

we do have his number one colleague, Dr. Crowley, on our second panel 

and I am grateful for that as I am sure the Minority is as well. 

 Again, I thank the Chairman for the recognition and I want to thank 

all of our witnesses for taking their valuable time to be with us here 

today. I know there are many other productive activities you could have 

been doing. And we have already heard from our friends on the other 

side of the room that there does indeed currently exist an international 

consensus that global warming exists and that human beings have caused 

it. They didn’t say so but I would further extrapolate that it is Americans 

that have caused it and it is probably one American in particular and he 

lives in the White House. But I think it is fair to point out that no such 

consensus exists. 

 The Earth has been heating and cooling for millions of years. There 

have been big ice ages, little ice ages and it is fair to say that in between 

those two cooling events it probably even got a little warm. The Earth’s 

climate is cyclical and we have only been paying attention during the 

past few hundred years. With the cyclical nature of the Earth’s climate, 

it is plausible to say that the Earth’s temperatures would be on the rise 

today regardless of what humans did or didn’t do. Thirty-five years ago, 

I was a freshman in a geology class and we learned how the Earth itself 

was spun off as a hot ball of gases and gradually cooled and it was 

postulated that the Earth had been cooling ever since and indeed perhaps 

Armageddon would come one day not as a fire or as a flood but as we 

cooled into that last ice age. Now we have global warming staring us in 

the face. 

 I am not saying we should completely dismiss fears of global 

warming as an inaccurate science. I think that it merits thoughtful and 

serious debate and we owe the subject matter thoughtful and serious 
23

debate. Part of my problem with the whole process is, that it seems that 

the cleaner we make our energy generation capability, and indeed we 

have cleaned our energy generation capability over the years, and the 

Ranking Member can take considerable credit for that with legislation 

that he has passed, but now we want to come up against an obstacle that 

nothing can come out of those pipes, we have already taken out the 

VOX, the NOX, the SOX, the POX, the TOX. Now it is the carbon 

dioxide and water that are coming out of those smokestacks that has to 

be stopped, and it is interesting that later today--we have a mechanism to 

stop the carbon dioxide from coming out of those stacks and later today 

we are having a hearing in the Energy and Air Quality Subcommittee of 

this same Energy and Commerce Committee on the Yucca Mountain 

nuclear waste repository. One of the reasons why Yucca Mountain is so 

important is because of the increasing importance of nuclear power in 

our national fuel mix as an emissions-free, carbon-free-emissions source 

of power. 

 In fact, I would submit that along with the passage of the Clean Air 

Act in the past few decades, perhaps one of the greatest missed 

opportunities--if the Clean Air Act was an enacted opportunity, one of 

the great missed opportunities was abandonment of nuclear power in the 

late 1970s and allowing other countries to get ahead of us in that regard 

so now that our dependence on foreign oil--and we knew in the 1974 

embargo that dependence on foreign oil was not a good foreign policy 

strategy and yet for whatever reason we have lagged with development 

of nuclear fuel, so I am grateful we are having that hearing later on 

today. 

 It is false to presume that a consensus exists today or that human 

activity has been proven to cause global warming, and that is the crux of 

this hearing. What we are here today to discuss is the broader issue of 

the use of sound statistical analysis and the peer review process through 

the lens of the hockey stick temperature studies, but the focus of our 

hearing today is to examine the statistical analysis and methodology used 

when evaluating the influential report on global warming written by Dr. 

Mann. As the U.S. Congress and even the international policymaking 

bodies look to the scientific community to provide information and 

analysis, it is especially important to make certain that the processes are 

in place to ensure that we are using sound and unbiased science that has 

undergone rigorous peer review process. 

 I would point out that simply turning off the electrical generation 

plants that provide the air conditioning back in my district would not be a 

viable option. I would submit that the good people of California got 

upset when some people in Texas turned off their electrical generation 

plants a few years ago. I don’t see that as a viable option. Should we 
24

move to other methods? Perhaps, but we need to do so in a sound and 

scientific manner. 

 With that, Mr. Chairman, I will yield back. 

 MR. WHITFIELD. At this time I recognize Ms. Baldwin of--okay, 

Ms. Schakowsky. 

 MR. STUPAK. Mr. Chairman, before we do that, if I may, I would 

like to put into the record a letter from Georgetown University Law 

Center Institute for Public Representation explaining why Dr. Mann 

cannot be here on such short notice from the committee and other dates 

he was available to testify. I would like to put that in the record, a 

follow-up of the statements that he is on vacation, which is not true. 

 MR. WHITFIELD. We would be happy to do so unless-- 

 MR. STUPAK. Thank you. 

 MR. WHITFIELD. --there is objection. Is there objection to this going 

in? Thank you. 

 MR. STUPAK. This letter of July 19 was provided actually by fax to 

Mr. Spencer and Mr. Paoletta. 

 [The information follows:] 
25
26

 MR. WHITFIELD. Ms. Schakowsky. 

 MS. SCHAKOWSKY. Thank you, Mr. Chairman. 

 I am glad that we are holding a hearing on global climate change 

although I am disappointed in the actual substance of this, and I have a 

statement for the record that is prepared but I would like to just say a 

couple of things extemporaneously about this issue which I care so much 

about. 

 I guess I would ask about this particular hearing in some ways is, 

what is the point? I think that there are certain agreements that all of the 

scientific community would adhere to, and one is that climate change, 
27

the question being how much does human activity contribute to that, but 

the climate change is definitely happening, that the Earth is warming 

right now and there is a large and robust body of science that documents 

that, that even in the Middle Ages it could have been as warm as now 

although that is not clear at all, that the temperature is going up and that 

climate change impacts are being observed now and are projected to be 

of enormous consequence, enormous consequence. If the snow in the 

Himalayas melts, which provides water for I think close to a billion 

people, this is of great concern. 

 As a grandmother, I am concerned that my grandchildren may never 

see or know about a polar bear in the wild and that the coral reefs are 

disappearing. The fact that we are seeing stronger hurricanes and 

tornadoes and that there is drought and flood and hunger and 

displacement as a consequence, these are things that we know about, and 

so the question is, even if human activity is not the principal cause of 

global warming, which most scientists do believe that is the case, but 

even if it weren’t but we are simply contributing to it, why wouldn’t we 

be focusing on now how human activity could reduce the impact of 

global warming, how we could help to stem the tide of these devastating 

consequences that will hurt all of humanity. Why wouldn’t we be 

focusing on that instead of trying to discredit a report that is only one 

piece of the evidence that establishes that we are in the midst of a 

tremendous change that is going to impact the possibility of life as we 

know it on this planet. 

 We don’t have to be talking about the kinds of devastating changes 

in lifestyle that Americans won’t accept. Instead, because of our 

ingenuity, always being on the cutting edge of technology and change, 

we can manage the changes that are needed in order to sustain life on this 

planet. It just makes no sense to me--I mean, we will talk about it and 

we will get into it how the Mann statistics that are going to be discredited 

actually weren’t used in his final report and we can go into all the details 

back and forth about the scientific evidence but it seems to me that this is 

a waste of time, that what we ought to be talking about is how are we 

going to confront what everyone knows is a real problem, and if human 

activity can be changed in some way to ameliorate that problem, for the 

life of me I can’t understand why all of us together in a bipartisan way 

wouldn’t want to do that. 

 I have a young person in my district who really is absolutely 

obsessed with the issue of global warming. He is a junior high school 

student. His mother is worried about him because he worries about it so 

much. To me, the answer isn’t explaining to him oh, be happy, don’t 

worry, this isn’t really an issue, there is nothing you can do about it. The 

answer is, we need to tell young people, the next generation, my 
28

grandchildren, that there are things that we can do today, and so I plead 

with my colleagues on both sides of the aisle, let us get down to 

solutions, not discrediting one tiny piece of the mass of evidence that 

says that we are in trouble right now and that literally billions of people, 

all the people are on our plant, will suffer if we don’t get down to the 

business of finding a solution, so I thank you, Mr. Chairman, for the 

time. 

 MR. WHITFIELD. Thank you. Mr. Stearns, you are recognized for 5 

minutes. 

 MR. STEARNS. Thank you, Mr. Chairman. I think Mr. Stupak put in 

the letter of July 14 from Mr. Mann’s lawyer. I would like unanimous 

consent to put in the letter of July 13 that preceded that, which if without 

objection I would like that-- 

 MR. STUPAK. Well, I guess I will have to object until we see it. Can 

we at least see it? 

 MR. STEARNS. Oh, sure, sure. Yes. You put a letter that came after 

the first letter and I thought it would be appropriate if we include that 

letter too since that is a day earlier in which he said he could not make 

our committee and for whatever reason he couldn’t make it and in fact he 

suggested that if we do have this hearing, that we should have Dr. 

Thomas J. Crowley, and indeed we took his advice and we got Dr. 

Crowley. He is going to be on the second panel, so we took Dr. Mann’s 

advice, we got the people he wanted, and I am sure, Mr. Chairman, other 

people had to cut their vacation short to be here, perhaps even Dr. North 

did. This is a time when a lot of us are taking vacations, not necessarily 

Members of Congress who are into a campaign mode but the rest of you 

perhaps are doing that, and I can understand that, but the letter Mr. 

Stupak put in said that he would not even show up on the 27th. The letter 

I am putting in says he won’t show up today. Unfortunately, his lawyer 

from the Georgetown University Law Center keeps talking about July--I 

think in his letter--I don’t have it in front of me but he has a 

typographical error in both letters in which he cites Friday, July 9. In all 

calendars, July 9 is not a Friday. 

 MR. WHITFIELD. They are not objecting to the letter. 

 [The information follows:] 
29
30

 MR. STEARNS. Okay. Good. All right. Well, I was just talking to 

make sure Mr. Stupak had plenty of time to read it so that I could go 

forward. 

 You know, I think almost everybody in this room and perhaps 

everybody on this oversight committee would agree that there is global 

warming of some kind. The question is, is it sinusoidal, that is, are we 

looking at warming today in which there was warming like this or similar 

to this in the Middle Ages and have we seen a warming and a cooling 

much like a sinusoidal wave, and so we are trying to look at Dr. Mann’s 

analysis and we are trying to say, is he absolutely right that we have this 

hockey stick effect that is just flat and then suddenly comes up. 

 Now, we have Dr. Wegman’s analysis concludes that Dr. Mann’s 

work cannot support the claim that the 1990s were the warmest decade in 
31

the millennium. I mean, that is what he is saying. Some people are 

questioning Dr. Mann, his quantitative analysis, and that is fine. He 

could be right, he could be wrong. Now, Dr. North, in looking through 

his testimony which he is going to give, he sort of confirms what I think 

is possible, that this warming and cooling is a sinusoidal wave and that in 

fact, let me just read what Dr. North says in his testimony. He says that 

it is plausible that the Northern Hemisphere was warmer during the last 

few decades of the 20th Century than during any comparable period over 

the preceding millennium. That is what he says. However, the 

substantial uncertainties currently present in the quantitative assessment, 

same thing that Dr. Wegman says, of large-scale surface temperature 

changes prior to about 1600 A.D. lower our confidence in this conclusion 

compared to the high level of confidence we place in the Little Ice Age 

cooling and 20th Century warming. So we have two distinguished 

individuals who are professionals in their fields indicating that it is not 

absolutely true that Dr. Mann is correct in his analysis and Dr. North 

went on to say even less confidence can be placed in the original 

conclusions by Dr. Mann. 

 So, I mean, for anybody on the other side to say this not a legitimate 

hearing is incorrect. We have taken people that Dr. Mann wanted and 

we put them on here as witnesses. We have asked Dr. Mann to come to 

this hearing. We have asked him to come to the 27th. He won’t come. 

He has hired a lawyer to spar with our people to say why he won’t come. 

By golly, if he really is interested in solving this problem, I would cut my 

vacation short and whatever he is doing to say I will be here because I 

think in the interest of science, I would like to have an open hearing and 

talk about it. So I think, one, it is a legitimate hearing. Two, we have 

offered Dr. Mann two opportunities and yet his lawyer has indicated he 

won’t show up. So this is a very important issue but I think overall, all 

of us here are trying to understand this and we would agree that there is 

probably global warming. What we want to know is, is this sinusoidal or 

is this something that is aberrational. 

 Let me conclude by saying that yes, we should have further inquiries 

into this matter. Perhaps as a result of this hearing we will. Temperature 

studies and the effect of climate change, all these are very important to 

our very existence. So Mr. Chairman, I commend what you are doing 

and I commend the other side too to keep an open mind here and to hear 

Dr. Wegman and to hear Dr. North and to read their opening statements 

where you will see they have less confidence and they certainly have as 

much credibility on this matter as Dr. Mann, and I am just so sorry, so 

sorry that Dr. Mann is not showing up today, he is not showing up on the 

27th, and at this point I am not clear, Mr. Chairman, when you will get 

him. Thank you. 
32

 MR. WHITFIELD. Ms. Baldwin, you are recognized for 5 minutes. 

 MR. STUPAK. Mr. Chairman, may I ask unanimous consent that the 

letter that we received from Dr. Mann’s lawyer indicating he would like 

to come at the same time these witnesses are here be entered into the 

record. 

 MR. WHITFIELD. It has been. 

 MR. STUPAK. Oh, it has been? Oh, okay. Thank you. 

 MR. WHITFIELD. We have had two letters introduced into the record 

from his lawyer, both. 

 MS. BALDWIN. Thank you, Mr. Chairman. It doesn’t take much 

more than a quick walk outside today to know that the thermometer has 

reached dangerously high levels and government heat alerts are 

abounding these days but this summer is not unique. Each year summers 

are growing warmer and warmer and so are the winters, falls, and 

springs. Of the 20 hottest years on record, 19 have occurred in the 1980s 

or later. 2005 was one of the hottest years on records and so far 2006 has 

set record levels for its high temperatures. 

 Unfortunately, despite overwhelming scientific evidence that our 

planet is warming at dramatic rates, no political consensus for bold 

action has followed and that is the problem. Politicians ignore sound 

science showing evidence that the Earth is warming at an unprecedented 

rate, that carbon dioxide levels are rising, and that human activities are 

largely the cause. But beyond ignoring sound science, they are doing 

other disturbing things. I see political interference in science these days. 

In fact, time after time, sound science has been censored in order to 

maintain a political agenda. Here are just a few examples. 

 In 2003, the EPA was ordered by the White House to delete critical 

sections relating to climate change from its report on the environment. 

In 2005, the White House insisted upon weakening language relating to 

the impact of global climate change in a document that served as the 

basis of negotiations during the G8 Summit, and just a few months ago 

the Administration tried to silence a NASA scientist from talking about 

the need to reduce greenhouse gases linked to global warming. I could 

point to many other examples, some on this topic, some outside, but it is 

a disturbing trend indeed. 

 With all these examples, it only becomes more clear that false logic 

will not bring us closer to an understanding of the scientific truth. The 

truth is alarming. Sea levels are rising. Glaciers are melting and storms 

are becoming more intense, and the result is the near extinction of 

animals such as polar bears, the compromising of coastal ecosystems, 

and the threatening of human life as heat waves become prevalent and 

disease-carrying insects grow more abundant. 
33

 Mr. Chairman, I often speak about America’s need to take bold 

action and the importance of us leading the world on environmental 

issues. Now is the time for us to show our commitment for if we do 

nothing, we risk an uncertain and unstable future. So I ask, what are the 

consequences if the cynics and naysayers and keepers of the status quo 

are wrong? We have a moral and an ethical obligation to act and I just 

hope that today we will take some steps in that right direction. 

 Thank you, Mr. Chairman. I yield back the balance of my time. 

 MR. WHITFIELD. Thank you, Ms. Baldwin. At this time I recognize 

Mrs. Blackburn. 

 MRS. BLACKBURN. Thank you, Mr. Chairman. Thank you for 

holding the hearing. Thank you to the staff for the preparation work they 

have done and to our witnesses appearing before us to comment on the 

matter. We thank you for being here. We are concerned about it. I do 

think it is prudent to address the issue and we are seeking information. 

We thank you for being here to supply some. 

 The ability to obtain and analyze the data and the methods that a 

scientist uses to form a theory about the universe is central to science. 

For hundreds of years society has placed the utmost importance on the 

scientific method to validate theories which is predicated on the ability to 

replicate and verify a scientist’s work. If the work cannot be replicated 

and verified by independent experts, then that work’s conclusions 

become more speculation and possibly some will say it should be open to 

classification as outright scientific dishonesty. 

 Last year Chairman Barton inquired into the background of some 

recent climate change studies that had been held by scientific portions of 

the scientific community as proof of drastic global warming. Now, I am 

old enough to remember that as a teen in the late 1960s, I sat in science 

classes and in a geology class and I was warned of a returning and 

impending ice age. By the time I reached my current age, the world was 

going to be covered in ice, North America would have a 9-month winter, 

our food supplies would be short, and I would be freezing to death all the 

time. Well, I guess times changed or maybe that old group of scientists 

had some kind of political interference in favor of the new group of 

scientists who now want the Earth to warm up. 

 Now, after some independent analysis it seems that all scientists 

could possibly be misled on some of their issues. Both the National 

Academy of Sciences and Dr. Wegman’s committee analyzed the hockey 

stick report by Dr. Mann that has become the poster child for proof of 

global warming. The committees came to the conclusion that Dr. 

Mann’s hockey stick report failed verification tests and did not employ 

proper statistical methods. Also, it appears that Dr. Mann is part of a 

social network or could be part of a social network of climate scientists 
34

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 

is holding an investigative hearing, and when doing so we do have the 
35

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 

MM02, 05a and 05b, respectively. 
36

 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 

principal component is intended to explain most of the variation present 
37

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 

the critique of the MBH99 methods. 
38

 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. 

Recommendation one: Especially when massive amounts of public 
39

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 
40

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 1.2o centigrade. In the NAS panel Report chaired by Dr. North, 

.6o 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. 

Archive Minimum Temporal Potential

Sampling Range Information

Interval (order:yr) Derived

Historical records day/hr ~103 T, P, B, V, M, L, S

Tree rings yr/season ~104 T, P, B, V, M, S, CA

Lake sediments yr to 20 yr ~104-106 T, B, M, P, V, CW

Corals yr ~104 CW, L, T, P

Ice cores yr ~5 x 104 T, P, CA, B, V, M, S

Pollen 20 yr ~105 T, P, B

Speleothems 100 yr ~5 x 105 CW, T, P

Paleosols 100 yr ~106 T, P, B

Loess 100 yr ~106 P, B, M

Geomorphic feat. 100 yr ~106 T, P, V, L, P

Marine sediments 500 yr ~107 T, CW, B, M, L, P

Characteristics of Natural Archives

T = temperature P = precipitation, humidity, water balance

C = chemical composition of air or water B = information on biomass, vegetation patterns

V = volcanic eruptions M = geomagnetic field variations

L = sea level S = solar activity

After Bradley and Eddy (1991)

FIGURE 1

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.] 

 
41

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. 
42

FIGURE 3

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 

methodology properly. 
43

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. 
44

CFR Methods

Figure 5

To further illustrate this, we digitized the temperature profile published in the IPCC 

1990 report and applied both the CFR and the CPS methods to them. The data used here 

are 69 unstructured noise pseudo-proxy series and 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 3 panels indicate what happens using principal components with an 

increasing amount of de-centering. Again, the single series begins to overwhelm the other 

69 pure noise series. Clearly, these have a big effect. 

It is not clear that Mann and associates realized the error in their methodology at the 

time of publication. Our re-creation supports the critique of the MBH98 methods.

In general, we found the writing in MBH98 and MBH99 to be somewhat obscure 

and incomplete and the criticisms by MM03/05a/05b to be valid. The reasons for setting 

1902-1995 as the calibration period presented in the narrative of MBH98 sounds 

plausible, 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 paleoclimate studies have had 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 temperature 

reconstruction. 
45

Mann-Rutherford-Jones-Osborn-Briffa-Bradley-Hughes

FUGURE 6

We found that at least 43 authors have direct ties to Dr. Mann by virtue of 

coauthored papers with him. Our findings from this analysis suggest that authors in the 

area of this relatively narrow field of paleoclimate studies are closely connected. Dr. 

Mann has an unusually large reach in terms of influence and in particular Drs. Jones, 

Bradley, Hughes, Briffa, Rutherford and Osborn. 
46

FIGURE 7

DR. MANN

DRs. JONES, 

BRADLEY, 

HUGHES, 

BRIFFA, 

RUTHERFORD, 

OSBORN

Because of these close connections, independent studies may not be as independent 

as they might appear on the surface. Although we have no direct data on the functioning 

of peer review within the paleoclimate community, but with 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. 
47

FIGURE 8

Bradley & Jones (1993)

Mann, Bradley, Hughes 

(1998,1999)

Jones et al. (1998)

Crowley & Lowery (2000)

Briffa (2000)

Esper (2002)

Mann & Jones (2003)

Bradley, Hughes, Diaz 

(2003)

Jones & Mann (2004)

Moberg et al. (2005)

Osborn & Briffa (2006)

D’Arrigo, Wilson, Jacoby 

(2006)

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. Using the same data also suggests a lack of independence. 

The MBH98/99 work has been sufficiently politicized that this community can 

hardly reassess their public positions without losing credibility. Overall, our committee 

believes that the MBH99 assessment that the decade of the 1990s was the likely the 

hottest decade of the millennium and that 1998 was likely the hottest year of the 

millennium cannot be supported by their analysis. 

Recommendations 

Recommendation 1. Especially when massive amounts of public 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, Climate Change 2001: The Scientific Basis, should not be the same people as 

those that constructed the academic papers. 

Recommendation 2. 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 funding agencies has been that 

they do not in general 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 data collectors to have 

exclusive use of their data for one or two years, prior to publication. But data collected 

under federal support should be made publicly available. 

Recommendation 3. 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 
48

based on statistical assessments. In such cases, evaluation by statisticians should be 

standard practice. This evaluation phase should be a mandatory part of all grant 

applications and funded accordingly. 

Recommendation 4. Emphasis should be placed on the Federal funding of research 

related to fundamental understanding of the mechanisms of climate change. Funding 

should focus on interdisciplinary teams and avoid narrowly focused discipline research. 

 MR. WHITFIELD. Thank you, Dr. Wegman, and Dr. North, you are 

recognized for your opening statement. 

 DR. NORTH. Thank you, Mr. Chairman. Before I begin, I would like 

to introduce Peter Bloomfield from North Carolina State University, who 

is a professor of statistics there, and he was on our committee, the NAS 

committee, and so I will use him if I need to during the course of-- 

 MR. WHITFIELD. Welcome, Dr. Bloomfield. 

 DR. NORTH. Good morning, Mr. Chairman, and members of the 

committee. My name is Jerry North. I am a professor of atmospheric 

sciences at Texas A&M University and it is nice to see one Aggie here. 

He said he took some statistics there and I suspect he knows more than 

he is letting on today. And I served as the Chairman of the National 

Research Council’s committee on surface temperature reconstruction for 

the last 2,000 years. 

 My comments today will highlight the findings of our committee’s 

recently released report. Its aim was to asses the state of scientific efforts 

to reconstruct surface temperature records for the Earth over the last few 

thousand years, and to comment on the implications of these efforts for 

our understanding of global climate change. Surface temperature 

reconstructions are only one of many lines of evidence supporting the 

conclusion that the climate is warming in response to human activities. 

These long records give context and perspective to the issue but they are 

not the primary evidence. In fact, human-induced climate change is 

quite real. 

 First some background. Widespread thermometer records only the 

last 150 years or so. To extrapolate deeper into the past, scientists have 

learned to use proxy evidence such as tree rings, corals, ocean and lake 

sediments, ice cores, glacier records, boreholes, and historical 

documents. To give one example, the advances and retreats of glaciers 

can tell us whether the climate has been warmer or cooler on the average 

at that location. Starting in the 1990s, scientists began combining proxy 

evidence for many locations in an effort to estimate temperature changes 

averaged over broad geographic regions for the last few thousand years. 

 Much attention has been concentrated on papers published by 

Michael Mann, Raymond Bradley, and Malcolm Hughes in 1998 and 

1999. This is partly because the authors concluded that the Northern 

Hemisphere was warmer during the late 20th Century than at any time 
49

during the past millennium. In addition, it was illustrated with a simple 

graphic, the so-called hockey stick curve, that was featured prominently 

in the 2001 Intergovernmental Panel on Climate Change report, and you 

have seen that graphic. 

 Our committee examined the scientific literature in great depth, 

considered written and oral remarks from experts representing a broad 

range of perspectives. We reached five major conclusions. Number one, 

the warming of about one degree Fahrenheit during the 20th Century is 

real. No one doubts it. 

 Number two: Besides the rapid warming in the 20th Century, two 

other features appear to be common in the records, a cool period centered 

in A.D. 1700 called the Little Ice Age and a warm period around 1000 

known as the Medieval Warm Period, details about the latter being much 

less certain. 

 Number three: It can be said with a high level of confidence that 

global mean surface temperature was higher during the last few decades 

of the 20th Century than during any comparable period since 1600. This 

statement is justified by the consistency of the evidence from a wide 

variety of geographically diverse proxies. If we could put that graphic 

up. That one. That is the only one I will show. So here is the kind of 

diverse evidence that I would like to just mention. These are different 

curves from different investigators. Most of them have come out after 

the Mann et al. work, and some of them don’t rely on the statistical 

techniques at all. The boreholes, for example, come from the direct 

physics, no calibration with the instrumental temperatures, and the same 

is true for the glacier length records. 

 Number four: Less confidence can be placed in large-scale surface 

temperature reconstructions from A.D. 900 to 1600. We find that 

temperatures at many, but not all, locations were higher during the last 

25 years than during any period of comparable length since A.D. 900, 

but the uncertainties increase substantially as one moves backward in 

time through this period and are not yet fully quantified. Now, the way 

we tried to illustrate that on this graphic is by showing a sort of 

darkening graying as you go back, and one of my colleagues on the 

committee says well, as you go back beyond the year 1600, things get a 

little murkier, so the amount of the kinds of data that we have and so on 

are much less certain. We don’t understand all of the interrelations and 

so forth, so I can go into that in more detail if you need it. 

 And number five, very little confidence can be assigned to 

statements concerning the average surface temperatures prior to about 

A.D. 900, so we just don’t know enough about that period. 

 Now, the basic conclusion of the 1999 paper by Mann and his 

colleagues was that the late 20th Century warmth in the Northern 
50

Hemisphere was unprecedented during at least the last 1,000 years. This 

conclusion has substantially been supported by an array of evidence, but 

substantial uncertainties remain for the period before about 1600, and I 

can give you some illustrations of other ways of looking at the problem 

later if that should come up in questions. Our main disagreements with 

the Mann 98/99 papers are related to the assertions about warmth of 

individual decades and individual years. We don’t subscribe to that kind 

of definition of the problem. We also question some of their statistical 

methodology, in fact, some of the same claims that were put forward by 

Dr. Wegman and you will hear some later as well. 

 However, our reservations with some aspects of the original papers 

by Mann and colleagues should not undermine the fact that the climate is 

warming and will continue to warm as a result of human activities. In 

fact, the scientific consensus regarding human-induced climate warming, 

global warming, would not be substantively altered if the global mean 

surface temperature 1,000 years ago was found to be as warm as it is 

today although there is evidence that this really is a very exceptional 

period that we are in now, and again, I can come back to that during 

questions. This is because we don’t know enough about the driving 

forces of the climate over that long period. 

 During the last 150 years, we have considerable evidence about the 

increase in greenhouse gas concentrations and we know a lot about the 

other things that tend to nudge the climate system as well. By the way, a 

lot has been learned about climate in the last 30 or 40 years. I mean, it is 

a very rapidly changing field and we have all the giant computers and 

satellites now at our disposal to help us. So we know a lot more about 

this than we did 30 years ago. And in the last quarter century, when 

warming was particularly steep, we also have good data on the sun 

because for the last 25 years we have been measuring the sun very, very 

accurately from outside the atmosphere using satellites. Aerosols--we 

have a very good idea of how the dust and tiny particles in the 

atmosphere have been changing over the last 25 years and probably 50, 

both of which--both of these two drivers of climate change, the sun and 

the aerosols, really are negligible compared to the forcing from 

greenhouse gases. 

 Moreover, climate models can only reproduce the warming of the 

20th Century when greenhouse gases are included. Our knowledge of the 

driving forces over the last several thousands of years is not yet good 

enough to go back beyond this recent period, so that is the reason that 

that early data doesn’t really close or finish off the story. 

 So now in conclusion, our committee finds that large-scale surface 

temperature reconstructions contribute to climate research, they are 

important, and that they contain meaningful climate signals. Our 
51

confidence in the reconstructions becomes stronger when multiple 

independent lines of evidence point to the same general result such as the 

warmth of the last few decades of the 20th Century relative to the last 400 

years. Further research, especially in the collection of additional proxy 

evidence, would help to reduce the uncertainties and allow us to make 

more definitive conclusions over longer time periods. 

 I thank you for your attention, and I would be happy to answer any 

questions, and I may call on Dr. Bloomfield to help me. 

 [The prepared statement of Dr. Gerald R. North follows:] 
52

PREPARED STATEMENT OF DR. GERALD R. NORTH, DEPARTMENT OF ATMOSPHERIC 

SCIENCES, TEXAS A&M UNIVERSITY
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55
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57
58
59

 MR. WHITFIELD. Dr. North, thank you and Dr. Wegman both for 

your testimony, and Dr. North, now, you are a Ph.D. Are you a 

climatologist or-- 
60

 DR. NORTH. I have a Ph.D. in physics from the University of 

Wisconsin. 

 MR. WHITFIELD. From the University of Wisconsin. 

 DR. NORTH. Yes. 

 MR. WHITFIELD. A wonderful school. 

 DR. NORTH. Yes. It is a wonderful school. 

 MR. WHITFIELD. Almost as good as Texas A&M. 

 DR. NORTH. Well, comparable. 

 MR. WHITFIELD. Now, have you had the opportunity to review Dr. 

Wegman’s and his associates-- 

 DR. NORTH. Yes, I did receive it a few days ago so I don’t think I 

have read it in the detail that I should but I have been able to look 

through it. 

 MR. WHITFIELD. And you all don’t know each other? You are not 

friends or-- 

 DR. NORTH. No, I met him at our briefing a couple of weeks ago 

just for a handshake. 

 MR. WHITFIELD. Well, I was wondering if you might just take a 

minute or two to summarize your--as a professional in this area and your 

experience in this area. What is your reaction to their report? 

 DR. NORTH. Well, I think that on many things we are in agreement. 

The studies that--I mean, the examination they did of the statistical 

procedures and the Mann et al. papers is not the way we would--that I 

would have done it in hindsight, especially now looking back. It is not 

the way I would have done it. I don’t think there is anything dishonest 

about it or anything like that, but I think that the analyses that the 

Wegman group did really were--some of those were examined by the 

statisticians on our committee and I don’t think that we are in any great 

disagreement about it. Let me just mention this, that the criticisms don’t 

mean that the MBH claims were wrong. They just mean that the MBH 

claims are not convincing by themselves. So if you pull together other 

information, then that does change the view a bit. 

 MR. WHITFIELD. Now, Dr. Wegman, I am not a statistician but 

obviously a statistician is where you look at data and from that data you 

try to look at the probability of something happening or not happening 

and whatever. Is that just in a rough layman’s term what statistics is all 

about, or give me your definition of statistics or a statistician. 

 DR. WEGMAN. Well, I think a statistician generally tries to look at 

data and represent the meaning, the inferences that are available from 

that data as straightforwardly and honestly as possible. 

 MR. WHITFIELD. Now, Dr. North said that his group had reviewed 

your document and that they agreed with much of what you said and you 

have indicated that one of your primary concerns about the Mann 
61

document is the center point that was utilized in his hockey stick graph. 

Would you elaborate on that a little bit? 

 DR. WEGMAN. Yes. They used the period from 1902 to 1995, which 

was the instrumented temperature record that they used, so they used that 

period to calibrate the proxy data. They centered their overall proxy data 

on that period, 1902 to 1995, and of course temperature was rising in that 

period, so when you center on that period, you push the rest of the proxy 

data below the axis. That has, as I mentioned, the net effect of increasing 

the variance and making the principal component methodology pick out 

that kind of shape. So it preferentially attempts to fit those kind of 

shapes in the first principal component. 

 MR. WHITFIELD. And it does establish this hockey stick showing a 

rapidly increasing-- 

 DR. WEGMAN. That is essentially the mechanism that creates the 

hockey stick. If you do the--as I showed in the one graph, if you do the 

centering properly, the hockey stick disappears. 

 MR. WHITFIELD. Now-- 

 CHAIRMAN BARTON. Would the Chairman yield on that point? 

 MR. WHITFIELD. Yes. 

 CHAIRMAN BARTON. Dr. Wegman, you say when you center it 

properly. Put in layman’s terms that those of us that are not statisticians, 

what does that mean, centering it properly? 

 DR. WEGMAN. Thank you for asking. The principal components 

analysis methodology requires that the data be centered on the mean of 

the overall series, so if you are doing reconstructions, let us say, back to 

year 1000, 1000 to 2000, then you should center on the average value of 

the proxy series for the period 1902 to-- 

 CHAIRMAN BARTON. In which there is better data. I mean, they--

there could be a plausible reason why they did what they did, the more 

accurate data, they are more certain of it? 

 DR. WEGMAN. Well, they are more certain of the temperature data 

but the net effect of the decentering is to preferentially pick out these-- 

 CHAIRMAN BARTON. But what they should have done was if they 

are going to measure from one 1000 to 2000, they should have used all 

the data points and came up with the mean and centered wherever that 

mean was? 

 DR. WEGMAN. That is correct, yes. 

 CHAIRMAN BARTON. Thank you. 

 MR. WHITFIELD. And I think the reason that is important is that 

when you make a categorical statement that the 1990s were the warmest 

decade in a millennium and that 1998 was the warmest year in the 1,000, 

I mean, it is difficult to make a statement like that categorically if the 

centering is not correct. Would you agree with that? 
62

 DR. WEGMAN. Yes, I agree. 

 MR. WHITFIELD. And I think that is the whole basis of this hearing 

because this hockey stick--all of us are concerned about global warming 

but I do think we have an obligation and responsibility--everyone has 

latched onto this hockey stick and almost created a panic in a way, and 

maybe we should be panicked, but I think it is important that we 

understand how the hockey stick came about, and that is what we are 

talking about today. Now, Dr. North, do you agree with Dr. Wegman’s 

centering analysis or not? 

 DR. NORTH. I do. I think that he is right about that. However, you 

know, we have to be careful here and not throw the baby out with the 

water. 

 MR. WHITFIELD. Right. 

 DR. NORTH. Because there have been other analyses, papers 

published after the Mann papers in which people just took a simple 

average. Dr. Crowley wrote a paper just a short time after that in which 

he didn’t use the principal component analysis at all. He got essentially 

the same answer. And so-- 

 MR. WHITFIELD. Is that what we refer to as the CPS analysis? 

 DR. NORTH. I don’t know what the initials--but he just took the 

average instead of dealing with the data the way one does it in the 

principal component analysis, so what I am arguing, and some other 

people have also done this same, there have been many studies later that 

don’t use principal component analysis and the ones that I showed you, it 

is not there now-- 

 MR. WAXMAN. Mr. Chairman. 

 DR. NORTH. They don’t all use principal component analysis. 

 MR. WHITFIELD. Yes? 

 MR. WAXMAN. Will you yield to me? I am just wondering if Dr. 

Wegman is familiar with Dr. Crowley’s way of handling the statistics 

and if he thinks that the conclusions are suspect in the Crowley study. 

 DR. WEGMAN. Well, let me say that simple averaging of proxies, 

depending on how the proxies are selected, can yield the same kind of 

results. In fact, if--I don’t know if you can put up my backup slide, 

backup figure number 2, the backup figure number 2 shows-- 

 MR. WHITFIELD. Well, are we putting this graph up? Where is this 

graph? Okay. There we go. Okay. 

 DR. WEGMAN. This is using the CPS, simple averaging proxy 

methodology, just like the principal components, and by doing the simple 

averaging of proxies appropriately selected, you can reconstruct the same 

shape that you had with the principal component-type methodology. So 

it is possible depending on how you approach this. 
63

 MR. WHITFIELD. So you can do a lot of things, just depending upon 

what data you use, what the centering is and so forth? 

 DR. WEGMAN. Exactly. 

 MR. WHITFIELD. Now, let me just ask both of you one question 

quickly. My time has been used by other people. 

 MR. WAXMAN. I would like to ask unanimous consent that the 

chairman be given two additional minutes, but are you critical--because 

that was my question--are you critical of his methodology in reaching the 

same conclusion? 

 DR. WEGMAN. I am saying that it is quite possible to use the CPS, 

the averaging methodology, and come to the same conclusion that Dr. 

Mann had. I am not saying he did that because I haven’t studied his 

paper in such detail as to be willing to say that. 

 MR. WHITFIELD. Well, let me just ask you on this whole issue of 

scientific analysis and scientific collaboration and so forth, you 

mentioned this social networking, for lack of a better term. I mean, like 

any other profession, scientists, statisticians, they deal with each other, 

they know each other, they write articles together and so forth. But how 

serious is this issue of bodies making scientific reports and getting into a 

pattern of talking to the same people all the time about the same thing 

and they all have the same views? Is that a significant problem or not? 

 DR. WEGMAN. I think it potentially can be. It would be naive to 

think that there are not competing social networks within a discipline 

area. Sometimes the competing social networks keep each other in 

check. In the statistical arena, for example, there is a group of people 

who view themselves as classical statisticians. There is a group of 

people who view themselves as Bayesian statisticians. As one of our 

reviewers said, Heaven help you if you get a reviewer from a competing 

social network. 

 MR. WHITFIELD. Okay. 

 DR. WEGMAN. And I think it would be naive to think that these 

things don’t exist. They exist in peer review journals, they exist in 

reviews of proposals submitted to the NSF and other organizations. 

 MR. WHITFIELD. Would you like to make a comment about this 

whole issue, Dr. North? 

 DR. NORTH. Well, I would be pleased to. There are several matters 

here. Social networking, it does seem to me to be a little bit of a problem 

to pick out that this young scientist got busy and found himself 43 

coauthors. I think a lot of us would look at that and say my, he is quite a 

charismatic young man who has gone out and found himself 43 

collaborators. That is something that I would probably look very 

favorable on if I were considering him for tenure. And so there is that. 

Now, do people collaborate and think similarly? Of course they do. But, 
64

you know, if you look back at the history of, say, quantum mechanics in 

the early 1920s, it was Einstein, Bohr, Heisenberg, all these people. I am 

sure if you did a similar analysis, you would probably find something 

very like that, but in fact these guys hated each other. I mean, they were 

very, very competitive. And if you look at the 43 authors, I am sure that 

not all of them like to go out and have a beer together. This is pretty 

competitive business, and I will tell you, if somebody can find a way to 

knock down someone else’s theory, that is their road to recognition and 

fame. We all do that. That is part of the game and we really enjoy that 

part of the game. So yes and no. 

 MR. WHITFIELD. All right. Thank you. My time has expired and I 

will recognize Mr. Stupak. 

 MR. STUPAK. Mr. Chairman, because of time constraints, I am 

letting Mr. Waxman go now and I will catch the next round. 

 MR. WAXMAN. Thank you very much, Mr. Stupak and Mr. 

Chairman. That was an interesting analysis, Dr. North. We are 

sometimes sheltered by our own politics but it looks like academics have 

their politics. 

 DR. NORTH. They do. 

 MR. WAXMAN. And I guess we should take that into consideration, 

but I don’t think we doubt all science because experts agree with each 

other or that they are competing with each other. Is that-- 

 DR. NORTH. That is correct. You know, the process works. You 

know, as they say, it is a little like making sausage. You have heard that 

one. 

 MR. WAXMAN. On June 7, 2005, 11 National Science academies 

issued a joint statement calling on world leaders “to acknowledge that 

the threat of climate change is clear and increasing” and in their joint 

statement, the science academies of Brazil, Canada, China, France, 

Germany, India, Italy, Japan, Russia, the United Kingdom, and the 

United States declared, “There is now strong evidence that significant 

global warming is occurring.” They also stated that it is likely that most 

of the warming in recent decades can be attributed to human activities. 

Mr. Chairman, I would like to ask unanimous consent that this statement 

from the premiere scientific institutions be placed in the record. 

 MR. WHITFIELD. Without objection. 

 [The information follows:] 
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MR. WAXMAN. Dr. North, I would like to begin with you. Do you 

agree with the statement of these premiere institutions that there is now 
67

strong evidence that significant global warming is occurring and that it is 

likely that most of the warming can be attributed to human activities? 

 DR. NORTH. Yes, I do. 

 MR. WAXMAN. And Dr. North, the national science academies also 

state that the scientific understanding of climate change is sufficiently 

clear to justify nations taking prompt action. They say it is important 

that we take cost-effective steps now to reduce our emissions or else it 

will be more costly to act in the future. Again, do you agree with that 

statement? 

 DR. NORTH. Well, now you are stepping a little bit beyond my role 

here. I will talk about the science but what we ought to do is somebody 

else’s business. 

 MR. WAXMAN. I am concerned that some are going to hear about 

Dr. Wegman’s statistical criticism of the early Mann study and somehow 

conclude that global warming is still an open question. In order to put 

the overall importance of this issue in context, I would like to ask you 

about some of the other evidence of global warming. Are the Mann 

studies the basis for the ice core studies that give us data going back 

hundreds of thousands of years? 

 DR. NORTH. No. 

 MR. WAXMAN. Are the Mann studies the basis for the recorded 

atmospheric temperature records that we have maintained for the last 150 

years? 

 DR. NORTH. No. 

 MR. WAXMAN. Dr. Crowley is going to testify later today that 

although the Mann study was influential in the IPCC’s 2001 assessment, 

the studies, which demonstrated that the instrumental record and the 

models could not be reconciled without an anthropogenic greenhouse 

influence, were even more influential. Were those studies based on the 

Mann studies? 

 DR. NORTH. I don’t think so. I am sorry. I didn’t hear everything 

you said. 

 MR. WAXMAN. Well, Dr. Crowley is going to tell us that-- 

 DR. NORTH. He will talk about that, sure. 

 MR. WAXMAN. --although the Mann study was influential with the 

IPCC’s 2001-- 

 DR. NORTH. Well, it was part of the report. It was a part of the 

report. 

 MR. WAXMAN. Right. 

 DR. NORTH. But as I have said, it is only one of several lines of 

evidence that are used in drawing those conclusions. 

 MR. WAXMAN. And so therefore you have further studies that seem 

to come to similar conclusions? 
68

 DR. NORTH. There are other studies, and they were shown on the 

graphic that I showed you. 

 MR. WAXMAN. And they weren’t based on the Mann studies, were 

they? 

 DR. NORTH. They were not based on the Mann studies. Now, there 

are cases where they use the same data so there is some correlation and 

that is what I think Dr. Wegman referred to and that is correct. See, there 

is only a limited amount of data, so-- 

 MR. WAXMAN. In 2005, two research teams led by scientists at the 

Scripps Institution for Oceanography and NASA’s Goddard Institute for 

Space Studies published studies in Science magazine that concluded that 

not only is the Earth’s air and land warming, but the oceans are warming 

as well and that heating has penetrated more than 1,000 feet into the 

ocean’s depth. Jim Hanson, director of the NASA Goddard Institute for 

Space Studies and the lead author of one of the studies, called these 

findings “the smoking gun of global warming.” Dr. North, are these 

studies in any way based on the Mann 1998 and 1999 studies? 

 DR. NORTH. No, not at all. 

 MR. WAXMAN. In July 2005, Nature magazine published a study by 

Dr. Kerry Emanuel of M.I.T. who found that the destructive power of 

hurricanes is increasing along with ocean temperatures. Dr. Emanuel 

found that the total destructive potential of hurricanes has increased 

markedly during the last 30 years. While natural cycles in the pattern of 

ocean circulation likely played a role, Dr. Emanuel attributes at least part 

of the increase to global warming. Just last month the publication 

Geophysical Research Letters published a new study by Dr. Kevin 

Trenberth and Dr. Dennis Shea of the National Center for Atmospheric 

Research which concludes that global warming fueled hurricane intensity 

in the waters of the tropical North Atlantic in 2005, while natural cycles 

were only a minor factor. Dr. North, are these papers by Dr. Emanuel, 

Dr. Trenberth, and Dr. Shea in any way based upon Mann’s 1998 and 

1999 studies? 

 DR. NORTH. No, no. 

 MR. WAXMAN. Drs. Mears and Wentz published an article in 

Science magazine in August 2005 that resolves a longstanding conflict in 

the global warming debate. For years global warming naysayers, based 

on the work of Dr. John Christy at the University of Alabama, have 

argued that satellite data showed that the Earth’s atmosphere was 

warming far slower than the Earth’s surface. These scientists reanalyzed 

the raw satellite data and found that the lower atmosphere is actually 

warming slightly faster than the surface in agreement with the theory and 

models. These scientists found that the previous analysis of the satellite 

data had inaccurately corrected for changes in the satellite’s 
69

measurement time resulting from the decay of their orbit. Dr. Christy 

has now acknowledged his mistake and has adjusted his data series, 

making it much more consistent with other results. Dr. North, is the 

Mears and Wentz study in any way based on Mann’s 1998 and 1999 

studies? 

 DR. NORTH. Absolutely not. Dr. Christy was actually on our 

committee, by the way. 

 MR. WAXMAN. He was on-- 

 DR. NORTH. He was on the NAS committee. 

 MR. WAXMAN. Finally, if we were to-- 

 DR. NORTH. If I may just add one thing. You know, just because a 

paper is published, it goes out for the community. People--the wolves 

attack, and this particular study by Spencer and Christy took many years 

before the error was finally found. It doesn’t mean these guys are 

villains. It is just that-- 

 MR. WAXMAN. If you knew that Dr. Mears-- 

 DR. NORTH. --they did their best. It took years to find that mistake. 

 MR. WAXMAN. If you knew that those two scientists were friends 

with-- 

 MR. WHITFIELD. Would the gentleman excuse me one minute? Did 

you say it took many years before the error was discovered? 

 DR. NORTH. Before the error in the Spencer-Christy study using 

satellite data was found. It was a good-faith effort on their part but it 

turned out to be wrong. 

 MR. WAXMAN. If you knew that these gentlemen were friends with 

Dr. Mann, would that make you suspect their work? 

 DR. NORTH. I have no idea whether they know him. 

 MR. WAXMAN. Finally, if we were to sweep away the Mann studies 

and forget that they existed, would that in any way erode the validity of 

any of the studies I just mentioned? 

 DR. NORTH. I do not think it would. 

 MR. WAXMAN. Would there still be-- 

 DR. NORTH. We wouldn’t-- 

 MR. WAXMAN. Would there still be a scientific consensus that 

global warming is happening, it is being caused by humans and that 

some people think it is time to act now? 

 DR. NORTH. Yes, I think there would be. 

 MR. WAXMAN. And Dr. North, my point in asking you about these 

other studies is simply to illustrate how wrong it would be for anyone to 

draw sweeping conclusions from a statistical criticism of one or two 

studies from 8 years ago. Unfortunately, the Republican majority on this 

committee has been completely content to sit back and ignore global 

warming. They ignored it while President Bush frayed our relationships 
70

with our international allies over global warming. They ignored it while 

the committee crafted an energy policy that exacerbates global warming 

and they continue to ignore it as evidence piles up about the severity of 

the situation. Instead, we spend our time attacking climate researchers 

who have infuriated the oil lobby by contributing to our knowledge of 

this issue, and apparently that is the one thing that the Majority simply 

cannot ignore. My time is just about expired, and we have a vote on the 

House floor. I thank the witnesses for their testimony and Dr. North for 

responding to my questions. 

 MR. WHITFIELD. Mr. Chairman, we have 8 minutes to vote on the 

floor. Would you like to start your questions and come-- 

 CHAIRMAN BARTON. I would recommend that we recess and let us 

go vote, give our witnesses a chance to have a personal convenience 

break and then come back. 

 MR. WHITFIELD. We have two votes on the floor. The first vote will 

be over in about 10 minutes and then we will have another one, so we 

will reconvene at about 12:15. 

 [Recess.] 

 MR. WHITFIELD. At this time I recognize the Chairman for his 10 

minutes of questions. 

 CHAIRMAN BARTON. Thank you, Mr. Chairman. I appreciate the 

courtesy and I appreciate our witnesses here today. My first question is a 

personal question to you, Dr. Wegman, and it is not normally one that I 

would even think about asking but there has been some attempt to 

portray you as a pawn of this committee or me personally. I am told that 

you voted for Vice President Gore for president in the year 2000. Is that 

correct? 

 DR. WEGMAN. That is correct. 

 CHAIRMAN BARTON. So you are by no means a radical, wild-eyed, 

hard core, right wing Republican? 

 DR. WEGMAN. No, sir. 

 CHAIRMAN BARTON. Okay. How often, if ever, have you been in 

Texas? 

 DR. WEGMAN. I was in Texas in hill country a few weeks ago but I 

have been to Houston a few times, interacting in my social network with 

David Scott. 

 CHAIRMAN BARTON. But you are not--you and I until this morning 

have had no phone calls, no e-mails, no-- 

 DR. WEGMAN. I didn’t even know what you looked like until-- 

 CHAIRMAN BARTON. Which is a blessing for you, right? 

 DR. WEGMAN. No, sir. 

 CHAIRMAN BARTON. All right. Now, let me ask you, Dr. North, 

obviously you and I went to--I attended the school where you have been 
71

an illustrious professor for a number of years and I asked you during the 

break if you and I had met and you said that we had met on an airplane 

once. 

 DR. NORTH. We had a 2-minute--a 30-second conversation. 

 CHAIRMAN BARTON. So you and I have had some personal 

interaction, but that is it. Again, there is no real association in terms of 

continuing basis or anything. When Mr. Waxman was here, he was 

asking some questions of you, Dr. North, about headlines that had 

occurred and papers that had been issued that state the possibility or the 

probability that global warming is real and it is caused by humans, and it 

is your personal opinion that global warming is real and that a large part 

of the reason it is real is because of human emissions of greenhouse 

gases. That is a fair statement of yours? You need to push that button, 

put your microphone on. Let the record show that he said yes. But we 

have some headlines here that have been purported to be because of 

global warming. Dr. North, one of them is that more frogs are dying as 

the planet warms. Are you aware of that? 

 DR. NORTH. I have heard of it. 

 CHAIRMAN BARTON. You have heard of that. How about because 

of global warming, irrigation fuels warmer temperatures in California’s 

central valley, are you aware of that? 

 DR. NORTH. I have not heard of that one. 

 CHAIRMAN BARTON. Okay. How about the irony of global 

warming, more rain, less water? 

 DR. NORTH. I am familiar with that idea. I don’t know if I have 

seen that headline. 

 CHAIRMAN BARTON. Global warming could sour the wine industry? 

 DR. NORTH. I don’t-- 

 CHAIRMAN BARTON. Poison ivy grows faster, bigger, more 

irritating? 

 DR. NORTH. No, I don’t-- 

 CHAIRMAN BARTON. Global warming weakens trade winds. Global 

warming’s next casualty, igloo. Global warming could overwhelm storm 

drains. Strange things happening to Pacific coast marine life. Global 

warming might create lopsided planet. Global warming makes seas less 

salty. Space ring could shade Earth and stop global warming. My point 

is, a lot of people are jumping on the global warming bandwagon and 

there is no question it is serious, there is no question that eminent people 

like yourself believe the causality of human emissions. I don’t have a 

problem with that. I mean, you pointed out in your testimony what 

science is supposed to be about. My problem is that everybody seems to 

think that it is automatically a given and that we shouldn’t even debate 

the possibility of it and we probably shouldn’t debate the causes of it, 
72

and I think that is wrong. That is one of the reasons that we are holding 

this hearing. 

I want to put up the digitized temperature curve number 2 that Dr. 

Wegman was referring to. We determined that you couldn’t prove the 

hockey stick by using the data points, Dr. Wegman concluded that, and 

so Mr. Waxman said well, that is okay but there are other studies and one 

of them is the study of a methodology that was not using the 

methodology that Dr. Mann used, and that is--it is kind of an S curve 

and--that is not? 

 DR. NORTH. Figure number 2 is the one that-- 

 CHAIRMAN BARTON. That one right there. Now, in that curve there, 

Dr. North, the highest point looks to me to be about the year 1300. 

Would you agree with that? 

 DR. NORTH. Well, that is what it shows on that graphic. 

 CHAIRMAN BARTON. Okay. But it is definitely higher than the 

1900s. 

 DR. NORTH. Higher than--I think that curve goes up to the middle of 

the 20th Century although I am not sure. 

 CHAIRMAN BARTON. But it is obvious--I am not saying that is the 

truth, okay, but I am saying, if that is a justification for global warming 

in that particular study, which I believe is purported to be a Crowley 

study, that is using average temperatures, that that particular graph shows 

the warmest period was somewhere between 1100 and 1400. Is that 

correct? 

 DR. NORTH. Well, that is what the curve shows. I cannot tell you 

where that one actually came from. We used a graphic like that in our 

report just to give some perspective about how people thought the curve 

looked 15 year ago, 16 years ago, so we used a graphic like that. I 

believe you have replotted it here. 

 CHAIRMAN BARTON. Now-- 

 DR. WEGMAN. Let me be precise. This is a curve from the IPCC 

1990 report. 

 DR. NORTH. Sixteen years ago. 

 CHAIRMAN BARTON. Okay. And let us go to the study--there is a 

comparison in Dr. Wegman’s testimony of the Mann report and I believe 

this curve. There are two--keep going. There are two documents--yes--

no, not that one. 

 DR. NORTH. Number 4 and 5, I think. 

 CHAIRMAN BARTON. Well, my question is, something happened 

between the chart that we up here that showed the early 1300s being the 

warmest period and Dr. Mann’s study that obviously shows the 20th

Century, and my question is, what changed in the modeling or the 
73

methodology or the data set? Because Dr. Mann wipes out that early 

warming period. It is just not there. 

 DR. NORTH. Is that for me? 

 CHAIRMAN BARTON. It could be for either one of you. 

 DR. NORTH. Well, there is more data available 10 years later than 

there was in that first report. In fact, I have a feeling that that first report-

-I hope you will ask Crowley that later because I think he will know 

more about it than-- 

 CHAIRMAN BARTON. Well, is it now the consensus of the majority 

of the scientific community that this early warming period just didn’t 

exist? 

 DR. NORTH. No, I think that there is good evidence that such a 

medieval warm period did exist, however, it may not have existed at the 

same time at different locations on the Earth, and I could give you some 

information about that. For example, if you look in Greenland, there was 

a very distinct warming period in that time around--between 1000 and 

1200. In fact, there were colonies of people who lived there from 

Denmark and their civilization disappeared there. They went back to 

Denmark or died out, I am not sure which. 

 CHAIRMAN BARTON. But I mean, it is striking-- 

 DR. NORTH. So there is evidence, historical and so on, that-- 

 CHAIRMAN BARTON. It is on page 15 of your report, and I have the 

prepublication copy. You have the figure 03 at the top and then you 

have the figure 04 at the bottom. Oh three is a schematic description of 

global warming that is the IPCC report of 1990 and then the 04 figure is 

the Mann graph, and it is just striking to me that there is no correlation 

between the two, or very little. 

 DR. NORTH. Oh, actually, if you look at the gray area in the Mann 

graph, that is the area where the curve could fall with some reasonable 

probability. That is their error margin. 

 CHAIRMAN BARTON. Let me ask you-- 

 DR. NORTH. If you look at the family of our curves that I showed in 

our graphic, the family of curves that were derived by using several 

different methods and different sources, you find that that family of 

curves really does fall pretty close to where the gray is here, especially if 

you put margins of error on each of those comparable to these. 

 CHAIRMAN BARTON. Let me ask you-- 

 DR. NORTH. And we would dispute how accurately Mann and 

company did that. 

 CHAIRMAN BARTON. I understand that. 

 DR. NORTH. That is another matter. 
74

 CHAIRMAN BARTON. I understand that. It looks like my time is 

expired, so I want to ask one more question. Dr. North, do you dispute 

the conclusions or the methodology of Dr. Wegman’s report? 

 DR. NORTH. No, we don’t. We don’t disagree with their criticism. 

In fact, pretty much the same thing is said in our report. But again, just 

because the claims are made, doesn’t mean they are false. 

 CHAIRMAN BARTON. I understand that you can have the right 

conclusion and that it not be-- 

 DR. NORTH. It happens all the time in science. 

 CHAIRMAN BARTON. Yes, and not be substantiated by what you 

purport to be the facts but have we established--we know that Dr. 

Wegman has said that Dr. Mann’s methodology is incorrect. Do you 

agree with that? I mean, it doesn’t mean Dr. Mann’s conclusions are 

wrong, but we can stipulate now that we have--and if you want to ask 

your statistician expert from North Carolina that Dr. Mann’s 

methodology cannot be documented and cannot be verified by 

independent review. 

 DR. NORTH. Do you mind if he speaks? 

 CHAIRMAN BARTON. Yes, if he would like to come to the 

microphone. 

 MR. BLOOMFIELD. Thank you. Yes, Peter Bloomfield. Our 

committee reviewed the methodology used by Dr. Mann and his 

coworkers and we felt that some of the choices they made were 

inappropriate. We had much the same misgivings about his work that 

was documented at much greater length by Dr. Wegman. 

 MR. WHITFIELD. If I may interrupt just one minute. We didn’t 

swear you in so I want you to swear now that the testimony you gave 

was the truth. 

 [Witness sworn] 

 MR. WHITFIELD. Thank you. 

 CHAIRMAN BARTON. I would like to submit for our record an e-mail 

that was received, and I would be more than willing to share it with the 

Minority if they have not seen it before. They have it? It is an e-mail 

from Yasmin Said to Peter Spencer and it says, “To whom it may 

concern: I have read the reports of Chairman Barton and Chairman 

Whitfield entitled “ad hoc committee report on the hockey stick global 

climate reconstruction by Edward J. Wegman, David Scott, and Yasmin 

H. Said” and what follows this work of Wegman, Scott, and Said is 

simply referred to as Report. The assessment of previous results given in 

the Report is correct. The Report is entirely correct in stating that the 

most rudimentary additive model, the model of a simple temperature 

signal with superimposed noise, is not adequate to describe the complex 

relationships involved in climate dynamics. There is no physical process 
75

found in nature that does not involve feedback in one form or another to 

regulate the action of the system. The statistical methods and models 

described in the report use more variables and make possible the 

construction of more elaborate reconstructions that allow feedback and 

interactions. The report represents the correct way to proceed. It is 

especially important to bring the professional statistical community into 

the picture in order to assure that a sound analytical foundation is secured 

in the continuing development of this program. Sincerely, Enders A. 

Robinson, member of the National Academy of the USA, fellow of the 

European Academy of Scientists, professor emeritus and the Maurice 

Ewing and J. Lamar Rozelle, Chair, Department of Earth and 

Environment, Columbia University.” And I yield back. 

 MR. WHITFIELD. Thank you. At this time I recognize Mr. Inslee. 

 MR. STUPAK. Wait a minute. Did we accept this e-mail that was 

read into the record, or what? 

 MR. WHITFIELD. Well, he asked for unanimous consent if you all--

do you have an objection to it? 

 MR. STUPAK. Well, let us object for now. We will ask some 

questions of it later. 

 MR. WHITFIELD. They object to it being entered until they clarify a 

few things with that. 

 CHAIRMAN BARTON. But they had the document. I don’t want them 

to accept it if they have not seen it. I was told that they had seen it. 

 MR. WHITFIELD. We were told that you all had it last night but is 

that not-- 

 CHAIRMAN BARTON. But certainly we don’t want to put anything in 

that hadn’t been cleared. Mr. Chairman, they have every right to object 

if they haven’t seen it. 

 MR. WHITFIELD. Well, while they are discussing it, Mr. Inslee, why 

don’t you proceed with your questions. 

 MR. INSLEE. Thank you. Dr. Wegman, can you cite to us the first 

three laws of thermodynamics? 

 DR. WEGMAN. Probably not. 

 MR. INSLEE. And you shouldn’t be ashamed of that because you are 

a statistician, not a physicist. 

 DR. WEGMAN. That is correct. 

 MR. INSLEE. But it is important for us to talk about that in the 

context of some things I want to ask you. Because I believe reviewing 

the literature, and I spent some time doing this, it is beyond any 

reasonable doubt that there is a strong worldwide scientific consensus 

that human activities are putting carbon dioxide and other global 

warming pollutants in the air in a way that is changing our climate in 

fundamental ways. I want to ask you some questions about your 
76

testimony here today. I want to refer you to a chart that is up on the 

screen to your left, and it shows concentrations of carbon dioxide in the 

Earth’s atmosphere going back 160,000 years and basically what it 

shows is that the concentrations now which are in the lower right-hand 

circle are higher than they have been in any time in the last 160,000 

years. They also show that those concentrations of carbon dioxide will 

go up approximately doubling in the next century by the year 2100 

unless this Congress pulls its head out of the sand and does something 

about it. Now, the question I want to ask you, these carbon dioxide 

samples are beyond dispute because of direct physical measurement of 

old air trapped in glaciers and that they are not subject to any scientific 

doubt whatsoever. Neither as far as I know is there any question but that 

the carbon dioxide levels will significantly increase in the order of 

doubling of pre-industrial times in the next century if we do not act. So 

the question I ask you, is anything in your criticism of the Mann report in 

any way suggests that those conclusions I just stated to you that are 

reflected on this graph regarding carbon dioxide levels are faulty? 

 DR. WEGMAN. No, I don’t believe they are. 

 MR. INSLEE. So if you accept the first three laws of thermodynamics 

and basic chemistry and our ability to judge CO2 levels and if you accept 

the premise that carbon dioxide in the atmosphere has the capacity of 

essentially trapping heat in the energy system of the Earth--by the way, 

do you accept that proposition? 

 DR. WEGMAN. I don’t know about the second proposition. I do not 

know the mechanisms for trapping heat. 

 MR. INSLEE. Well, I will just tell you, the mechanisms of carbon 

dioxide essentially traps heat in infrared range of a frequency. Light 

comes in an ultraviolet range, it bounces back in an--not really bounces 

back but emitted in an infrared range and carbon dioxide traps it. It traps 

it like a blanket, as a crude metaphor. Now, what we know beyond a 

shadow of a doubt is that carbon dioxide in the next century is going to 

be at levels double any time in the last 160,000 years and double what it 

was in pre-industrial times. Now, does your criticism of Dr. Mann’s 

research in any way suggest that it would not be a good idea to reduce 

our carbon dioxide loading into the atmosphere? 

 DR. WEGMAN. My expertise does not extend to global warming and 

I have no position on this. 

 MR. INSLEE. Well, I think that is important for you to say that 

because what we are finding here is that there is this enormous 

worldwide consensus. I look at the joint academy statement--this is a 

joint academy statement of every science academy in the industrialized 

world and every single one of them state that it is a consensus that human 

activity is causing changes to the climate. I will just read directly. “It is 
77

likely that most of the warming in recent decades can be attributed to 

human activities. This warming has already led to changes in the Earth’s 

climate.” It is signed by Canada, Germany, France, Italy, Japan, United 

Kingdom, Russia, China, Brazil, and the National Academy of Sciences 

under the administration of George Bush. Now, I guess the question to 

you is, do you have any reason to believe all those academies should 

change their conclusion because of your criticism of one report? 

 DR. WEGMAN. Of course not. 

 MR. INSLEE. Why not? 

 DR. WEGMAN. Because my report was very specific on a very 

specific issue that was asked of me and we answered that very specific 

question. 

 MR. INSLEE. Well, let me suggest another reason. The reason you 

don’t suggest these academies are wrong is because they have a 

mountain of evidence from ice core data, through glacier data, to ocean 

acidification, to radar data, to surface and deep ocean temperature data 

that indicate that this world is changing because we are putting too much 

carbon dioxide in it. Isn’t that right? That is why you are not suggesting 

they change their report. 

 DR. WEGMAN. Well, there is the old statistical process that says 

association does not mean causation. 

 MR. INSLEE. Well, there is another statistical by Mark Twain is that 

there are three kinds of lies: lies, damn lies, and statistics, but I won’t 

bring that one up. I want to ask-- 

 DR. WEGMAN. Of course, he is not a statistician either. 

 MR. INSLEE. Dr. North, I want to quote--in your testimony you said, 

“However, our reservations with some aspects of the original papers by 

Mann et al. should not be construed as evidence that our committee does 

not believe that the climate is warming and will continue to warm as a 

result of human activities.” You go on to say, “The scientific consensus 

regarding human-induced global warming would not be substantively 

altered if for example the global mean surface temperature 1,000 years 

ago was found to be was warm as it is today.” Now, in listening to your 

testimony, what I take from this is that even if we were to conclude that 

Dr. Mann had never been born, the study had never been done, conclude 

even if there was a medieval warming period that approximated 

temperatures today, even if we were to accept that as a verity, even if we 

knew that today, what I am hearing your testimony tell us is that there is 

enough evidence of other methods and other dynamics at work in the 

climate today that we can with a reasonable degree of assurance 

conclude that humans are responsible for at least a portion of the changes 

in temperatures. Is that a fair statement? 
78

 DR. NORTH. Well, let me separate myself from the report now. I 

believe that is true but we didn’t address that issue in the report. 

 MR. INSLEE. And could you at least in summary fashion tell us 

about the other evidence that leads to your conclusion other than Dr. 

Mann’s? 

 DR. NORTH. Well, let me mention a few things that my colleague on 

the committee, Kurt Cuffey from the University of California-Berkeley 

sent. So this is a little about the medieval warm period. It takes a couple 

minutes so I apologize for that. So Greenland shows a clear signal of 

both medieval warmth and 20th Century warming. These are recorded 

unambiguously in isotopes and boreholes, nothing to do with this 

extrapolation method. The medieval was warmer than the 20th Century 

up to about 1990, but you know it has warmed quite a bit in the last 15 

years, so another piece of evidence is Ellesmere Island. This is in the 

Canadian Arctic and there is an icecap there. It also shows evidence of a 

medieval warm period and 20th Century warming and the isotopes and 

melt records. The melt in particular shows summertime warmth in the 

20th Century was greater than the medieval warm period, so there is that 

one. The composite of all available low latitude--this is Tibet and the 

Andes and there is things in Africa, Kilimanjaro. Ice core, isotope 

records show the 20th Century climate is truly anomalous on the time 

scale of 2,000 years. This is an objective quantitative measure of climate 

arising from physical processes. We cannot, however, separate a pure 

temperature signal from it because these glaciers are influenced by both 

moisture availability and temperature because hydrology is important 

too. All we can say is that the sum of the climate processes determining 

the isotope records have reached an anomalous state. One more--two 

more. Melt at the summit of Quelccaya--this is a big icecap in the 

Andes, the largest Andean icecap--was strong enough in the late 20th

Century to destroy annual layering of isotopes which did not happen 

during the medieval period. Now, the tropics are a very interesting place 

to look at climate. They are probably a little more representative of the 

global average, not as much natural variability in the tropics. So we had 

melting recently in the Quelccaya glacier but it didn’t happen in the 

medieval warm period. 

 MR. INSLEE. Doctor, I want to ask one quick question. My time is 

almost up. 

 DR. NORTH. I am sorry. 

 MR. INSLEE. Put the slide up on the acidification, Tracy, that one 

right there if I can. Doctor, I made reference to acidification that is 

taking place in our oceans as a result of carbon dioxide going into the 

atmosphere, then going into solution in the oceans. Could you briefly 
79

summarize that dynamic and what the state of our knowledge is about 

that? 

 DR. NORTH. I am not an expert on this. I have seen the report and 

the essence is that as we increase carbon dioxide in the atmosphere, the 

carbon dioxide of course dissolves in seawater just as it does in PepsiCola, so the greater the partial pressure of carbon dioxide in the 

atmosphere, the more that will be dissolved in the ocean and then you 

wind up with--by combining with other things, you wind up with a more 

acidic ocean so the pH of the ocean goes down, becomes more acidic. 

This attacks the corals and other things. So there could be something 

going on with aquatic life. Again, we are really pretty far away from-- 

 MR. INSLEE. And is that independent of temperature issues? 

 DR. NORTH. That is independent of temperature. 

 MR. INSLEE. So even if temperature doesn’t go up, this dynamic can 

acidify the ocean? 

 DR. NORTH. That has been happening and I presume will continue 

to happen. 

 MR. INSLEE. Thank you. Well, we would like to change that 

actually. Some of us have ideas about that. 

 DR. NORTH. That is not my job. 

 MR. WHITFIELD. Mrs. Blackburn, you are recognized for 10 

minutes. 

 MRS. BLACKBURN. Thank you, Mr. Chairman, and thank you all for 

your patience as we work through our votes today. Dr. Wegman, I have 

got three quick questions for you and Dr. North, I have got, I think one 

probably for you and I am going to try to finish so everyone gets their 

questions in before the next vote. But Dr. Wegman, you said in your 

testimony that Dr. Mann’s data is very obscure, incomplete, and 

disorganized, and I wanted you to expand on that and give us an example 

of how that data should have been presented, if you have something 

tangible. 

 DR. WEGMAN. Well, I had two things in mind. First of all, when I 

read the paper originally, it took me probably 10 times to read it to really 

understand what he was trying to say. He uses phrases that are not 

standard in the literature I am familiar with. He uses, for example, the 

phrase “statistical skill” and I floated that phrase by a lot of my statistical 

colleagues and nobody had ever heard of that phrase, statistical skill. He 

uses measures of quality of fit that are not focused on the kind of things 

typically we do. We went to his website to try and figure out where his 

data was. He has a website at the University of Virginia. We basically 

downloaded everything that was in his FTP website to try and gather 

together--try and understand what was going on. The materials tended to 

be very cryptic. When we looked at the Fortran code that he wrote, it 
80

was very difficult to understand how you could, in the Fortran code you 

read in the data, but it was unclear where the data was and how you 

could actually read it in and the coding of the data, so all those things 

tended to make it very difficult to try and replicate anything that he did. 

Ultimately, I believe it was in 2004, he published a corrigendum and it 

showed that some of the data that he used in the 1998 paper was not 

referenced in the 1998 paper and other material that he did reference in 

the 1998 paper was not actually used. So there was a lack of clarity in 

both the archived data as well as the writing of the appear itself that I 

found difficult to decipher. 

 CHAIRMAN BARTON. Will the gentlelady yield just for-- 

 MRS. BLACKBURN. I will yield. 

 CHAIRMAN BARTON. When you said his data was in Fortran code, 

what is Fortran code? 

 DR. WEGMAN. Fortran is a computer programming language that 

was invented in 1957. 

 CHAIRMAN BARTON. And when was the last time anybody else than 

Dr. Mann used that code? 

 DR. WEGMAN. Well, I suspect-- 

 CHAIRMAN BARTON. I knew it at Texas A&M in the 1960s and I 

had not heard the term and I wanted to make sure we were talking the 

same-- 

 DR. WEGMAN. Well, certainly programming languages have 

evolved dramatically over the years. Most of my colleagues use a 

software package called RS Plus. Many people use Mat Lab these days. 

 CHAIRMAN BARTON. The Fortran code is not something that would 

be normally used today by too many people? 

 DR. WEGMAN. I would think in certain circles it might be but it is 

reflective of the notion that there aren’t-- 

 DR. NORTH. Most climate models do use Fortran code. 

 CHAIRMAN BARTON. Oh, they do? 

 DR. NORTH. Yes. 

 CHAIRMAN BARTON. So that is standard? 

 DR. NORTH. It is standard in mathematical solution of these kinds of 

problems, not statistics. He is right about that. So Mat Lab is coming on 

but Fortran is very commonly used in large climate model work. 

 CHAIRMAN BARTON. Well, then I should be able to do some of this 

because I can code in Fortran. I yield back. 

 MRS. BLACKBURN. Dr. Wegman, I still want to come to you. So 

what you are saying is that he--I want to go back to one thing on the data 

that he chose to input on the website, he was selective in the nature of 

what he chose to put in there and I guess that is much like what we saw 

with the calibration issue over the years that he used in that-- 
81

 DR. WEGMAN. There were a large number of proxies that were used 

in the 1998 and 1999 papers. As a matter of fact, it probably wasn’t very 

selective. He essentially threw everything including the kitchen sink into 

this data set. 

 MRS. BLACKBURN. I want to ask you a question that Dr. Crowley 

makes a statement in his testimony that was submitted to us, that the data 

is reused, Dr. Mann’s data is reused because it is the best data. But you 

say that other papers cannot claim to be independent verification if they 

reuse the same data. So I would like for you to speak to that and kind of 

reconcile the differing views. 

 DR. WEGMAN. Well, in one of our plots we had a plot that showed 

the data that was being used as the proxies versus the 11 or 12 papers 

that had been published since 1998 and the striking thing is, I think, that 

essentially there are two methodologies that we talked about, the CPS 

methodology and the CFR methodology, and my contention is that if you 

use the same data and the same basic methodology, you can-- 

 MRS. BLACKBURN. Then following on with that, if you were to 

structure an external statistical review for climate papers that would 

guarantee to be an independent verification of methods used, how would 

you structure this? 

 DR. WEGMAN. Well, I think there are a couple of approaches. One 

of the analogies I kind of liked was that the folks that do the hockey stick 

kind of thing call themselves--I think they call themselves the hockey 

team and when games are being played, you also need referees, so I think 

it would be a good idea to have referees for the hockey games. My own 

feeling is that it would be useful as we said in one of our 

recommendations that there be an external review and that it be funded 

as part of this kind of activity. If you have significant statistical 

methodology being used in a scientific study, then you really ought to 

have statistical review as well as the peer paleoclimate review. I think 

this extends beyond just paleoclimate stuff. It is true, for example, in 

biostatistics, biological science, medical science, that there is typically a 

heavy involvement with statistical review. I think in terms of things like 

sociology, psychology, there is heavy involvement with statisticians in 

this kind of framework. It appears to me that in the physical sciences, 

the same mental set is not typically done. 

 MRS. BLACKBURN. Thank you. Dr. North, I have got a couple of 

quick questions on surface records and satellite measurements that I want 

to give to you but I have only got a minute and a half left and I think I 

will submit these to you and then ask for your response, and Mr. 

Chairman, I will yield back so somebody else can get their questions on 

the record before we go for another vote. 
82

 MR. WHITFIELD. Thank you, Mrs. Blackburn. At this time I 

recognize Mr. Stupak. 

 MR. STUPAK. Thank you, Mr. Chairman. Dr. Wegman, in your 

report you criticized Dr. Mann for not obtaining any feedback or review 

from mainstream statisticians. In compiling your report, did you obtain 

any feedback or review from paleoclimatologists? 

 DR. WEGMAN. No, of course not, but we weren’t addressing 

paleoclimate issues. We were addressing-- 

 MR. STUPAK. But you said you had difficulty understanding some of 

the terms of art that Dr. Mann used and you had to call your social 

network to figure it out so wouldn’t it have been helpful to have 

paleoclimatologists? 

 DR. WEGMAN. To say that I didn’t contact any climate people is not 

entirely accurate. We have-- 

 MR. STUPAK. But they weren’t used in compiling your report--that 

was the question--correct? 

 DR. WEGMAN. Well, I am not sure how to answer that. I certainly-- 

 MR. STUPAK. Well, yes or no is probably the best way. Did you 

have any paleoclimatologists when you compiled your report? 

 DR. WEGMAN. Not on our team, but that doesn’t mean I didn’t talk 

to any. 

 MR. STUPAK. Did anyone outside your social network peer review 

your report? 

 DR. WEGMAN. Yes. 

 MR. STUPAK. Who was that? 

 DR. WEGMAN. Well, Enders Robinson. 

 MR. STUPAK. Is that the e-mail we were talking about earlier? 

 DR. WEGMAN. Pardon? 

 MR. STUPAK. Is that the e-mail that was-- 

 DR. WEGMAN. Yes. So-- 

 MR. STUPAK. When you do peer review-- 

 DR. WEGMAN. Let me answer the question. Enders Robinson, 

Grace Waba, who is a member of the National Academy, Noel Cressy, 

who is at the Ohio State University, Bill Wasorik, who is at Buffalo State 

SUNY, David Banks, who is at Duke University, Rich Schareen is the 

immediate past president of the American Statistical-- 

 MR. STUPAK. Let me ask you this question. If you had a peer 

review, when are peer reviews usually done? Before a report is finalized 

or after? 

 DR. WEGMAN. We had submitted this and had feedback from-- 

 MR. STUPAK. No, no, I am talking about general peer review. If you 

are going to have a peer review, don’t you usually do it before you 

finalize your report? 
83

 DR. WEGMAN. Yes. 

 MR. STUPAK. Well, your peer review was after you finalized it? 

 DR. WEGMAN. No, it was before. We submitted this long before. 

 MR. STUPAK. Well, when was your report finalized? 

 DR. WEGMAN. I think we dated the final copy about 4 days ago. 

 MR. STUPAK. Four days ago, so that would be about July 15. This 

e-mail sort of indicates it is July 17 that you asked for this peer review. 

 DR. WEGMAN. I had feedback from Enders much earlier than that. 

We had asked him to send material to us for purposes of coming here. 

 MR. STUPAK. Well, the e-mail read into the record is Tuesday, July 

18, so that would be 3 days after you finalized your report. 

 DR. WEGMAN. I am sorry. We-- 

 MR. STUPAK. Have you seen this e-mail, the one that-- 

 DR. WEGMAN. Yes, of course I have. Dr. Robinson saw our 

material before the 18th, before the 17th, before the 16th. He gave us 

feedback. We incorporated that. He gave us feedback verbally. We 

incorporated that because there was some interest in getting this report to 

the committee. 

 CHAIRMAN BARTON. Would my friend from Michigan yield for one 

simple question on this same point? 

 MR. STUPAK. Sure. 

 CHAIRMAN BARTON. Dr. Wegman, do you object to Mr. Stupak or 

anybody in the Minority submitting your report for a peer review as long 

as the peers are qualified in statistical analysis? 

 DR. WEGMAN. Not at all. 

 CHAIRMAN BARTON. Thank you. 

 MR. STUPAK. In doing peer reviews, do scientists who do the report, 

do they usually submit to people they want to do the peer review? Isn’t 

that sort of an independent review? 

 DR. WEGMAN. This is basically the same mechanism that was used 

at the National Academy. The national--you know, this is not a-- 

 MR. STUPAK. Did you ask these people to do your peer review? 

 DR. WEGMAN. Yes. 

 MR. STUPAK. So would they be part of your social network? 

 DR. WEGMAN. No. When I talk about social network, I am talking 

about people with whom I have actively collaborated in writing research 

papers. 

 MR. STUPAK. It sounds-- 

 DR. WEGMAN. None of these people have actively collaborated with 

me in writing research papers. 

 MR. STUPAK. Isn’t the same kind of social network you criticized 

Dr. Mann on because the people that reviewed his were 

paleoclimatologists? 
84

 DR. WEGMAN. Were the people that had actually worked with and 

published papers with. 

 MR. STUPAK. And you have published papers with some of these 

people that peer reviewed your report? 

 DR. WEGMAN. No. I just told you no, I haven’t. 

 MR. STUPAK. Let me ask you this. Page 34 of your report, I think 

you have it in front of you, your 52-page summary there, you have a 

figure that you say is a digitized version of the temperature profile in the 

IPCC assessment report of 1990. I take it you read the 1990 IPCC 

report? 

 DR. WEGMAN. I am sorry. What page was it? 

 MR. STUPAK. Page 34 of your report. It is figure 4-5. It is this one 

right here. We have had some--it has been referred to as figure 2 on the 

screen a couple times today. 

 DR. WEGMAN. No, I have not been able to obtain a copy of the 1990 

report. 

 MR. STUPAK. Well, then you must have at least discussed this 

temperature profile. 

 DR. WEGMAN. The temperature profile that was published in 1990 I 

believe was related to the European temperatures and was a cartoon--

essentially a cartoon. The point of our discussion here was not that we 

were trying to say that this was what happened in 1990. The point of our 

discussion was that you could reproduce this shape from the CPF, CFP 

and the climate plus--whatever--CPS methodology so we are not 

endorsing that this was the temperature that was thought of in 1990. We 

are simply using this as an example. 

 MR. STUPAK. Were you endorsing 1300 as being a real high 

temperature time? Were you endorsing it in your report? 

 DR. WEGMAN. No, we have not said that. 

 MR. STUPAK. What was the 1990 IPCC temperature profile based 

on? Basically what was this based on? You are a statistician. 

 DR. WEGMAN. This-- 

 MR. STUPAK. Was this based on data? 

 DR. WEGMAN. As I just said moments ago, this was a cartoon I 

believe that was supposed to be representing a consensus opinion of what 

global temperature was like in 1990 as published by the IPCC. 

 MR. STUPAK. Well, is this cartoon then--again, I am on page 34, I 

am reading now from your report, discussion you have underneath this 

cartoon. Last line: “The 1990 report was not predicated on global 

warming scenario. It is clear at least in 1990 the medieval warm period 

was thought to have temperatures considerably warmer than the present 

era.” Is that your discussion? 

 DR. WEGMAN. Yes. 
85

 MR. STUPAK. So we should not believe that statement then? 

 DR. WEGMAN. No, I said--I didn’t say I believed it was. I said they 

believed it was. The IPCC gave that report in 1990. 

 MR. STUPAK. All right. This chart-- 

 DR. WEGMAN. I didn’t-- 

 MR. STUPAK. This is in your executive summary, right, page 34, and 

what I read was correct? 

 DR. WEGMAN. Yes. 

 MR. STUPAK. Okay. Let me ask you this question. Have you 

reviewed any of Mr. Mann’s later refinements of his 1999 report? 

 DR. WEGMAN. I have reviewed some level of detail, not in intense 

level of detail, the continuing papers, most of which are referenced--in 

fact, the ones that are referenced-- 

 MR. STUPAK. Did he refine his data and his methodology? 

 DR. WEGMAN. My take on the situation is that rather than accept the 

criticism that was leveled, he rallied the wagons around and tried to 

defend this incorrect methodology. 

 MR. STUPAK. But did he refine his methods in later studies that he 

conducted, not whether he rallied the troops? Did he refine his methods? 

Was his job more accurate as he went on with later reports? 

 DR. WEGMAN. I believe that he does not acknowledge his 

fundamental mistake and that he has developed additional papers with 

himself and his colleagues that try and defend the original hockey stick 

shape. 

 MR. STUPAK. Do you know that or are you just guessing? 

 DR. WEGMAN. I am guessing that. 

 MR. STUPAK. Okay. Statisticians, should they guess or should they 

have facts to-- 

 DR. WEGMAN. That is called statistical estimation, yes. 

 MR. STUPAK. I see. Or a cartoon. 

 DR. WEGMAN. The cartoon is IPCC’s cartoon, not mine. 

 MR. STUPAK. You relied upon it though in your executive summary. 

So I am looking at the cartoon. There is no data, is there, to say that 

around 1300 it warmer than it is in the latter half of-- 

 DR. WEGMAN. I think that is an inaccurate statement. I think there 

is data. I think the data-- 

 MR. STUPAK. Do you have any of it? Can you show us where any 

of that is? 

 DR. WEGMAN. No, I don’t have it. I take no responsibility for what 

IPCC did in 1990. There is no way I could do that. Their data is not 

available to me. In fact, the reason it was digitized was that I had to go 

back and construct it from their picture. That doesn’t mean no data exist. 
86

And in fact, as far as I know, it was based on European and Asian 

temperature profiles that were available in the 1990s. 

 MR. STUPAK. Sure, and in that, it was thought--it was still not clear 

that all the fluctuations indicated were truly global. In fact, I think some 

of the testimony earlier said that parts of western Europe, China, Japan, 

and eastern U.S.A. were a few degrees warmer in July than other parts of 

the world. Parts of Australia, Chile, and I think Greenland were actually 

cooler, they said, and China was actually colder than at any other time. 

 DR. WEGMAN. Yes, I don’t dispute that. 

 MR. WHITFIELD. The gentleman’s time has expired. I recognize Mr. 

Bass. 

 MR. BASS. And I thank the gentleman for recognizing me. Before I 

start my questions, I just want to mention that there is a considerable 

amount of climate change work going underway in New Hampshire, my 

home state of New Hampshire, the Cold Research Laboratory which is 

run by the Army Corps of Engineers. They are studying ice core samples 

from both the Arctic and the Antarctic icecaps and also at the University 

of New Hampshire. NOAA, National Oceanographic and Atmospheric 

Administration is conducting ongoing longitudinal studies on the North 

Atlantic, air, water temperatures. And thirdly, at Hubbard Brook which 

is another research lab, they are studying climate change effect on trees 

and plants and other organic matter. 

 CHAIRMAN BARTON. Could the gentleman yield while-- 

 MR. BASS. Yes. Sure. 

 CHAIRMAN BARTON. Dr. North, Mr. Stupak just went to some 

lengths discussing this chart on page 34 of Dr. Wegman’s report that is 

from the IPCC assessment report of 1990. Can you tell us what the 

IPCC assessment report of 1990 was? 

 DR. NORTH. The IPCC is the Intergovernmental Panel on Climate 

Change. It is under the auspices of the United Nations and I don’t know 

the network all the way down to this group but this is a group that meets 

and is tasked to come up with a report every 5 years approximately. 

 CHAIRMAN BARTON. But in layman’s terms, could we say that the 

IPPC-- 

 DR. NORTH. No, IPCC. 

 CHAIRMAN BARTON. IPCC is the technical working group for the 

United Nations council of parties that ultimately drafted the Kyoto 

Accords? 

 DR. NORTH. I don’t know if there is a connection. I just don’t know 

that. I am sorry. 

 CHAIRMAN BARTON. It is my understanding that the IPCC is the 

group that prepared all the analytical materials and forwarded them on-- 
87

 DR. NORTH. They may have used their information. The IPCC, 

their job is to provide assessments, so Congress, political bodies go to 

them and ask for an assessment of the state of the art or the state of the 

science at the particular time as it is seen at that time. Of course, it 

changes so they came out again in 1995 and again in 2000 and there will 

soon be another one issued. 

 CHAIRMAN BARTON. But in 1990 when these scientists produced 

that report, this was their assessment of temperatures between the year 

1000 and the mid-1950s? 

 DR. NORTH. That is what they thought at that time. 

 CHAIRMAN BARTON. It doesn’t mean they were right, it doesn’t 

mean that they haven’t changed their mind. 

 DR. NORTH. That is why-- 

 CHAIRMAN BARTON. But in 1990 the state of the art was, that is 

what-- 

 DR. NORTH. That is what they thought. 

 CHAIRMAN BARTON. That is what it was. I yield back. 

 MR. BASS. Thank you, Mr. Chairman. Dr. Karl is going to follow 

you in the second panel and I will read a sentence out of his testimony 

and ask you a question about it, the last page. “At the present time there 

is no formal process whereby federally funded scientists must submit 

their data to a long-term data archive facility for use by others. The 

submission of data to institutions like NOAA’s, national climatic data 

center, the world’s paleoclimatic data center, requires significant 

investment of time by the principal investigators who collected the data 

to provide the useful information about the proxy data to the receiving 

data center. In addition, if such data are submitted, a significant 

investment by the data center would need to be made to ensure that the 

data is usable by others in perpetuity and safeguards for future 

generations,” and then he goes on about discussions. Dr. North, do you 

think this is an appropriate priority, and if so, do you think it would 

require any legislative action? What are your observations about Dr. 

Karl? And I think Dr. Wegman made the same contention. How do you 

feel about it, Dr. North? 

 DR. NORTH. Before I say anything, I should say that I know Dr. Karl 

and I have actually collaborated with him on some things, so that is a 

fact. I visited his laboratory, his center in Asheville, which is a very nice 

operation there. So I do think it is a good idea. I think it is something 

that the Government through a national laboratory like his should take 

on. I think this is too much for the little principal investigator out at your 

university or mine to deal with. So this is a way that data like this can be 

archived in a nice, clean environment. At Texas A&M, for example, we 

have the ocean drilling program and so we store these cores there that 
88

have been dug and they are carefully archived and protected and so I 

think that different laboratories should be charged with that kind of duty 

instead of having every little PI’s home base, so I do think it is a good 

idea. 

 CHAIRMAN BARTON. Would the gentleman yield on that? 

 MR. BASS. Certainly. 

 CHAIRMAN BARTON. I just think the record should show that when I 

was Congressman for Texas A&M, I helped get the money to establish 

that program and I am responsible for some of those core samples. 

 DR. NORTH. And I work with some of those people-- 

 CHAIRMAN BARTON. I want the record to show that. 

 MR. BASS. Reclaiming my time. I might suggest that this concept 

might be a starting point for some bipartisan cooperation legislatively if 

necessary to achieve this objective which would move the issue forward. 

Dr. Wegman, there has been some discussion about the network issues 

associated with paleoclimatologists. Is it substantially different than--

you know, the incestuous nature of the relationships between the 

paleoclimatologists. Do you think that it is the same or is different from 

other academic subjects? 

 DR. WEGMAN. I don’t know all of the academic subjects. What is 

true, I believe, is that in less focused activities, there are probably more 

competing social networks which even the playing field a little bit more 

than it appears to be in the paleoclimatology area. As mentioned earlier, 

I think for one person to have 43 coauthors is an unusually large number 

of coauthors. I personally believe that I probably have maybe 15 people 

that I have worked with over the years. 

 MR. BASS. Fair enough. Would you take--is it appropriate to take 

into account in that analysis the size of the entire climatic science 

community or is paleoclimatology so specialized that you couldn’t? 

 DR. WEGMAN. Yes. I think one of the interesting things that we will 

probably hear later on is the notion that this paleoclimatology is really an 

interdisciplinary area so it involves dendrology, it involves people that 

work with trees, with ice cores and so on and so forth. So it is not totally 

insular in the sense that it doesn’t involve people from other parts of this 

arena. What is insular though I think is that it doesn’t really involve 

people from the areas that I call the enabling sciences such as 

mathematics, computer science, and so on. But I think if you sort of 

followed the second order, third order, fourth order links, you would 

probably get a more interesting social network as well. 

 MR. BASS. One last question, Dr. Wegman. The National Academy 

of Science report that was released last month states the following: “It 

can be said with a high level of confidence that the global mean surface 

temperature was higher during the last few decades of the 20th Century 
89

than during any comparable”--during, I don’t know, there must be a typo 

here—“during the preceding four centuries.” Now, I understand from 

your testimony on the first page that you want to distance yourself from 

the issue of global warming, its causes, and its solutions, but would you 

agree with that statement? 

 DR. WEGMAN. Yes. I think that is a reasonably cautious verifiable 

statement that in terms of--and I speak now not as a professional 

statistician but as a citizen of this country. It seems to me that it is 

entirely reasonable to say that Dr. North and his panel made an accurate 

assessment, but it must be understood in the context which is that we 

have relatively speaking a Little Ice Age, which everybody seems to 

acknowledge, and so it is not so surprising that it is warming if we are 

coming out of a Little Ice Age. 

 MR. BASS. I want to thank both of you gentlemen for your testimony 

today and I yield back. 

 MR. WALDEN. [Presiding] The gentleman yields back his time. The 

gentlelady from Illinois, Ms. Schakowsky, is recognized for 10 minutes. 

 MS. SCHAKOWSKY. Thank you, Mr. Chairman. I have so many 

things I want to ask here. Let me start again. Dr. North, I want to 

confirm what I think you already said. Is Dr. Mann’s hockey stick study 

considered to be the foundation on which all climate change science is 

based? 

 DR. NORTH. No. 

 MS. SCHAKOWSKY. It isn’t. And again I want to say, if it never 

were, if the study simply--the hockey stick, the original and there was a 

revised in 2003-2004, right, my understanding is, which I guess you 

disagree, Dr. Wegman, acknowledged some of the mistakes and made 

some changes but if it never did, would most scientists essentially arrive 

at the same conclusion as we are seeing, that we are engaged--that this is 

a time of global warming attributable in large part to human activity? 

 DR. NORTH. Yes, I think that is true. 

 DR. WEGMAN. By the way, for what it is worth, I think it is true 

although I would caution you to not say most scientists. Most climate 

scientists would probably-- 

 DR. NORTH. That is better. Thank you. I appreciate that. 

 MS. SCHAKOWSKY. Okay, most climate scientists. Should we not 

rely on climate scientists for our information about the climate? 

 DR. WEGMAN. The point I was making was that you are saying most 

scientists, so the testimony-- 

 MS. SCHAKOWSKY. Well, let me ask-- 

 DR. WEGMAN. --of a chemist is irrelevant to-- 
90

 MS. SCHAKOWSKY. Exactly. So would you agree then that climate 

scientists are those that we should primarily refer to when we are asking 

questions about climate? 

 DR. WEGMAN. Certainly. 

 MS. SCHAKOWSKY. So you would agree that human activities are 

not only increasing atmosphere greenhouse gases but that it is attribute 

would you say in large part mostly in terms of your understanding as not 

a climate scientist to human activity? 

 DR. WEGMAN. I am in no position to say-- 

 MS. SCHAKOWSKY. Well, what did you say you did agree with 

earlier? 

 DR. WEGMAN. I said I agree that it is warming. That is what I 

agreed to. I mean, I said it several times now that the temperature record 

from 1850 onwards indicate that it is warming. 

 MS. SCHAKOWSKY. I also had said earlier that in my question to Dr. 

North and that most scientists agree that in large part or for your 

purposes I will say in some part attributable to human activity. Would 

you agree with that? 

 DR. WEGMAN. I don’t know that for a fact. 

 MS. SCHAKOWSKY. Okay. You don’t know that. 

 DR. WEGMAN. Again, it is the connection between carbon dioxide 

and temperature increase. Now, Mr. Inslee pointed out that he thinks 

there is a physical explanation based on a blanket of carbon dioxide in 

the reflection. Carbon dioxide is heavier than air. Where it sits in the 

atmospheric profile, I don’t know. I am not an atmospheric scientist to 

know that but presumably if the atmospheric--if the carbon dioxide is 

close to the surface of the Earth, it is not reflecting a lot of infrared back. 

 MS. SCHAKOWSKY. Okay. But are you not really qualified to-- 

 DR. WEGMAN. No, of course not. 

 MS. SCHAKOWSKY. --comment on that. I think since we are talking 

about scientific data, statistics, let us be clear, and you are challenging a 

report which form what I understand as Dr. North in some part at least 

you agree with the critique of the Mann data, so--and I am certainly--I 

am neither, but we are policymakers here so what I--do you believe that 

your report disproves that climate change is manmade in any way? 

 DR. WEGMAN. No. 

 MS. SCHAKOWSKY. And since you think that you are not in a 

position to make a decision on global warming, are you uncomfortable at 

all, Dr. Wegman, that the consequences of what you are saying today to 

policymakers, I think most of whom, if not all of them, are neither 

statisticians or climate scientists, could have the impact of saying we 

don’t need to do anything. Does that make you uncomfortable at all? 
91

 DR. WEGMAN. I would hope that our legislators are smarter than 

that to know that when somebody says that they are using wrong 

methodology, that does not imply that some fact is not true. I would 

hope that you would take my testimony with the idea that if something is 

wrong with this piece of work, it ought to be discarded as a policy tool, 

and that is precisely what I am saying. 

 MS. SCHAKOWSKY. Well, let me ask you this. Dr. Mann has 

published dozens of study since the original hockey stick study and as I 

said earlier, beginning in 2003 he reformulated the statistical methods. 

Do you take into account these later studies in your report? 

 DR. WEGMAN. I have read his later studies. I was not asked about 

his later studies. I think as science iterates, things do get better, but as I 

indicated before, one of the unfortunate aspects of this overall situation 

with Dr. Mann and his colleagues, my attack is not an attack at all. It is 

simply trying to lay out what I perceive to be a true statement. I think it 

is unfortunate that rather than moving on and saying gosh, I made a 

mistake and here is the better situation, here is a better approach, there 

continues to be a defense which is captured in his web log called 

realclimate.org. 

 MS. SCHAKOWSKY. And I understand that there are these battles and 

sort of the academic politics and scientific politics, et cetera, but do you 

disagree with Dr. North that even without Dr. Mann altogether or are you 

using these social--what do you call it--to say that everything now has to 

be discredited? 

 DR. WEGMAN. No, I don’t think everything at all has to be 

discredited, and I think the things that do not use the techniques, the 

flawed methodology with respect to principal components, anything that 

doesn’t use those, I have no position on. 

 MS. SCHAKOWSKY. And you talked about the cartoon that was in 

the Wall Street Journal article and then my understanding that the graph 

or whatever you call this, this drawing that it in your report, is it not true 

that it ends in 1975? 

 DR. WEGMAN. I think that is approximately accurate. But again, I--

this also appears in the National Academy report as well as the Wall 

Street Journal. I did not have the original data for that cartoon, for that 

graph, and so I had no way of knowing what the full range of the time 

frame was for that. 

 MS. SCHAKOWSKY. And would you confirm that, Dr. North, that it 

goes approximately or maybe exactly to 1975? 

 DR. NORTH. It is 1975. That is correct. 

 MS. SCHAKOWSKY. I am trying very hard to understand the point of 

this hearing and this conflict because if we are through many studies 

come to the conclusion that there is such a thing is global warming, 
92

which is hard to deny on a day like today and yesterday, et cetera, 

although I am not the scientist, and that it at least in some part is caused 

by human activity, then why we are doing this really does escape me. I 

can understand why in academia you may have an interest in discrediting 

Mann and back and forth, but I am very concerned that this is being used 

in a way to discredit the whole notion that our country and the rest of the 

industrialized and developing ought to do anything about global 

warming, and that is why I asked you that question, Dr. Wegman, if this 

does not make you somewhat uncomfortable. Can you see in any way 

how this is being used and does it bother you? 

 DR. WEGMAN. Well, I can understand that it is your job to sort out 

the political ramifications of what I have said. In some sense it is not fair 

for you to say well, gee, you have reported on some fact and that is going 

to be used in a bad way. The other side of the coin is that, you have tried 

to get me to say that manmade carbon dioxide emissions are associated 

with the global warming. 

 MS. SCHAKOWSKY. Which you can’t, right, because you are not a 

climate scientist. 

 DR. WEGMAN. I cannot say that, but what I can say is that from 

1850 to the present time, the global temperature rise is about 1.2 degrees 

Centigrade according to the Mann chart. One point two degrees 

Centigrade translates to about two degrees Fahrenheit. I challenge 

anybody to go out and tell the difference between 72 and 74 degrees 

Fahrenheit. What I do say and what I have said repeatedly is that you 

need to focus on the basic science. You need to understand what the 

transfer of heat from the ocean to the atmosphere, how that dynamic 

works, how the climate is going to change based on the physical 

mechanisms, a fundamental understanding of the physical mechanisms, 

not on some statistical estimation of those signals. 

 MR. WALDEN. The gentlelady’s time has expired. The gentleman 

from Florida, Mr. Stearns, for 10. 

 MR. STEARNS. I thank you, Mr. Chairman. Let me thank both of 

you for your patience here and how long you have been sitting. We have 

been changing chairmen here. They get to go but you don’t so we are 

very appreciative of what you are doing here. I think you aptly replied to 

Ms. Schakowsky’s comment that basically we are trying to look at the 

science of this. Mr. Chairman, I think it would be appropriate to put by 

unanimous consent this Wall Street Journal article, if you don’t mind to 

put this in. It is-- 

 MR. WALDEN. Without objection. 

 [The information follows:] 
93
94

 MR. STEARNS. Thank you. It talked about the hockey stick hokum 

and it goes on to talk a little bit about Mr. Mann and we all talked about 

it all morning but it says in 2001 the IPCC replaced the first graph with a 

second in its third report on climate change and since then this graph has 

cropped up all over the place. In fact, I think it is in Vice President 

Gore’s movie and I believe it is in his book, “Inconvenient Truth.” On 

page 65 he has got the source as the IPCC and then a little bit above it he 

talks about the hockey stick, a graphic image representing the research of 

climate scientist Michael Mann and his colleagues. So I would just say 

to my colleagues and Ms. Schakowsky to that it is important that if a 

graph suddenly becomes a significant graph in all these publications and 

shows up everywhere and is used in debate to make argument, I think it 

is important for all of us to look at this graph and I think that is all Dr. 

Wegman is doing is to say we are looking at this graph and as it turns out 

in this book, “An Inconvenient Truth” by Vice President Gore that he is 

using a graph as I understand it that has been established this morning 

that the methodology and the statistical analysis of it is incorrect and-- 

 MS. SCHAKOWSKY. No, that is not--will the gentleman yield for a 

second? 

 MR. STEARNS. Well, let me ask-- 

 MS. SCHAKOWSKY. Just for one second. 

 MR. WALDEN. Just regular order. 

 MR. STEARNS. I will be glad to do that. Let me just ask Dr. 

Wegman, if I have in his book the reference to the hockey stick and I 

have reference to the IPCC, then we have here a graph that you in fact 

are disputing because of its methodology and the statistics. Would that 

be a fair statement? 

 DR. WEGMAN. Well, I would like to be careful in that regard. 

 MR. STEARNS. Sure. I know. Do you want me to bring the book 

down and have the staff bring the book to you? 

 DR. WEGMAN. I have one. 

 MR. STEARNS. Oh, you have it. 

 MS. SCHAKOWSKY. Would the gentleman yield-- 

 MR. STUPAK. Would the gentleman yield on that point then? 

 MR. STEARNS. Well, let me just finish with my question here 

because what I am trying to understand is, you have a graph that 

suddenly goes everywhere and we have established today that the 

methodology for Dr. Mann’s graph is questionable, so the question is, if 

it shows up everywhere, shouldn’t the American people understand that 

some of the reference here in the book, the methodology is in question? 

That is all I am asking. 

 MR. STUPAK. Would the gentleman yield on that point? 

 MR. STEARNS. Well, let me ask-- 
95

 MR. STUPAK. Because if you are going to ask the question-- 

 MR. WALDEN. Regular order, please. It is the gentleman’s time-- 

 MR. STEARNS. I am not asking the question to you. I am asking it to 

Dr. Wegman, so I think, Mr. Chairman, I would like to have the question 

asked to him and not to my fellow colleagues. 

 DR. WEGMAN. Let me be precise on the statement. There is some 

ambiguity in this book because it talks about ice cores and as I 

understand it, this particular-- 

 MR. STEARNS. This is on page 65. 

 DR. WEGMAN. This particular picture-- 

 MR. STEARNS. Yeah, that is right, the same one. 

 DR. WEGMAN. --was based on ice core studies-- 

 MR. STEARNS. But it says below, it says source, IPCC, at the very 

little, small little note there. 

 DR. WEGMAN. Right. 

 MR. STEARNS. Okay. 

 DR. WEGMAN. Higher on the same page in the text it talks about 

Mann but I believe if one is going to be precise, this is a piece of study 

based on ice cores, not on the temperature reconstruction. 

 MR. STEARNS. So we just don’t know, and I think that is accurate. I 

am glad you pointed that out so that the reader or anybody looking at this 

would not necessarily say that the source of the IPCC is indeed Dr. 

Mann’s hockey stick-- 

 MS. SCHAKOWSKY. Would the gentleman yield for just a minute? 

 MR. STEARNS. No, I am just asking Dr. Wegman-- 

 MS. SCHAKOWSKY. Please, I can read from--I am looking at the 

same-- 

 MR. STEARNS. You folks had your time. I am just-- 

 MR. WALDEN. Regular order. 

 MR. STEARNS. When I complete my thing. So the question is, he 

says IPCC here and he has got this graph that looks like a hockey stick, 

you are saying that you cannot correlate that to mean that it is Dr. 

Mann’s graph? That is what you are saying? 

 DR. WEGMAN. I believe that is true. 

 MR. STEARNS. Okay. All right. Yes, I will be glad to yield to Ms. 

Schakowsky. 

 MS. SCHAKOWSKY. Thank you. I just want to read to you from that 

same--it says “But as Dr. Thompson’s thermometer show,” and so it is 

not based on Dr. Mann. This is a different source which our staff had 

confirmed with Al Gore. I just want to make-- 

 MR. STEARNS. I respect that. 
96

 MS. SCHAKOWSKY. --that point. I know, but your question wanted 

to reinforce the notion that this was based on this false or inaccurate Dr. 

Mann study-- 

 MR. STEARNS. Well, I think-- 

 MS. SCHAKOWSKY. --and it is not. 

 MR. STEARNS. Okay. 

 DR. WEGMAN. And I responded that it was not. 

 MS. SCHAKOWSKY. No, I-- 

 MR. STEARNS. Go ahead. You respond to that. 

 DR. WEGMAN. I responded exactly the same way you just did. 

 MR. STEARNS. And I think that is important to realize because it is 

showing up not just here but it is showing everywhere and so it is not 

precise that that is Dr. Mann’s graph here, and that is what you have 

confirmed. Now, I think the other real big question that we sometimes 

forget is, what effect does this have? I mean, what is--you mentioned 

here that it could be two degrees Fahrenheit from 1850 to 2006 and you 

say how many people could know the difference between 72 degrees and 

74. That was your words. The Competitive Enterprise Institute put out a 

report and let me just read from that. Dr. James Hanson of NASA, the 

father of the greenhouse theory, and Richard Linzen of MIT, both of 

them are renowned climatologists in the world, agree that if nothing is 

done to restrict greenhouse gases, the world will see a global temperature 

increase of about one degree Centigrade in the next 50 to 100 years. 

Hanson and his colleagues predict additional warming in the next 50 

years of .5 degrees Centigrade. A warming rate of .1, tenth of a percent 

Centigrade per decade, does that seem like an accurate statistic to you? 

Would you generally agree with that or disagree? I know it is difficult 

but-- 

 DR. WEGMAN. I have no way of truly knowing. 

 MR. STEARNS. But I mean, if you say in the last 156 years we have 

only had two degrees Fahrenheit, I mean, this would confirm that this is 

not something that is out of control. Wouldn’t you say that basically--

my point I am trying to establish is, that the estimates of this future 

warming should not get us into a hysterical mode. I know-- 

 DR. WEGMAN. I would tend to concur but what I would also say is 

that the global average temperature is probably not a very good measure 

of global warming in the sense that, as I said before, ocean circulation, 

salinity, how the Gulf current subducts when it gives up its heat in the 

Northern Hemisphere, understanding the coupling of that to the 

atmosphere seems to me to be the scientific issue at hand that really 

ought to be investigated more thoroughly. 

 MR. STEARNS. Also in this Competitive Enterprise Institute, the 

question came up, and Mr. Waxman mentioned a whole group of 
97

scientists, renowned scientists, that said that we are into a global 

warming and in this report it says, “What do scientists agree on and they 

agree that global average temperature is about .6 degrees Celsius or just 

over one degree Fahrenheit higher than it was a century ago. 

Atmospheric levels of carbon dioxide have risen by about 30 percent 

over the 200 years and carbon dioxide like water vapor is a greenhouse 

gas whose increase is likely to warm the Earth’s atmosphere.” Is that 

generally you think accurate? 

 DR. WEGMAN. As far I know, yes. 

 MR. STEARNS. But is there in your opinion a scientific consensus 

that global warming is real and bad for us? Could you say categorically, 

both you and Dr. North today, that there is a scientific consensus and 

evidence that global warming is bad and we should be very concerned 

about it? That is a tough question, I know. 

 DR. WEGMAN. I believe there is a consensus that global warming is 

real. My friends in Finland think it is a great thing. 

 MR. STEARNS. And your friends here in the United States don’t. 

Would that be fair to say? 

 DR. WEGMAN. Well-- 

 MR. STEARNS. I mean, that it is occurring but it is not as significant 

the people that are out there saying we have got to do something 

tomorrow, we have got to do something, do something. 

 DR. WEGMAN. I think it is probably less urgent than some would 

have it be. 

 MR. STEARNS. Dr. North, I am going to give you a few moments, 

unless you want to--you don’t have to say anything. 

 DR. NORTH. Well, my feeling is that it is happening but I don’t do 

good or bad. 

 MR. STEARNS. Let me just conclude, Mr. Chairman, just by saying 

that Dr. Wegman said that in the last 156 years it has gone up just about 

two degrees Fahrenheit and so I don’t really think we are into a very, 

very serious concern that we all should be worried about getting overly 

hot tomorrow. 

 MR. WALDEN. The gentleman’s time has expired. The gentlelady 

from Wisconsin, Ms. Baldwin, for 10 minutes. 

 MS. BALDWIN. Thank you, Mr. Chairman. Dr. Wegman, your 

report includes a social networking analysis of the authorship in 

temperature reconstruction, and to your knowledge, has this type of 

social network analysis ever been done before to look at an academic 

field? 

 DR. WEGMAN. No, and in fact, based on reactions to this, I think it 

is probably a good idea that we do this more broadly. 
98

 MS. BALDWIN. And am I correct in understanding that your analysis 

did not include talking to the paleoclimatologists to get their perspective 

on how they interact nor did it include substantively analyzing their 

interactions? 

 DR. WEGMAN. No. We simply looked at their connection in terms 

of, based on engineering compendics, based on their coauthorship. 

 MS. BALDWIN. In your report, you state that, and I quote, “Our 

findings from this analysis suggest authors in the area of paleoclimate 

studies are closely connected and thus independent studies may not be as 

independent as they might appear on the surface.” Are you saying that 

based on your social network analysis, that you are concluding that 

independent studies may not be independent or are you saying that your 

network analysis suggests a lack of independence as a hypothesis that 

one would need to investigate further before one could draw a 

conclusion? 

 DR. WEGMAN. I think one should take our social network analysis 

with a grain of salt to understand that this is an unusual configuration of 

people with a highly central person involved in this. It is no surprise to 

any working scientist that there are groups of statisticians, groups of 

mathematicians, groups of paleoclimate scientists, groups of physicists 

that work together closely and that there are competing social networks. 

I would hasten to add that social networks doesn’t mean I go out and 

drink a beer with somebody. It doesn’t mean I am a buddy of theirs. It 

means that I work with them, that I think like they do, that we have 

similar approaches. Now, if the group of people operating in this area is 

relatively small, as I believe it is in the paleoclimate area, then I think 

there is some evidence that probably should be investigated more clearly, 

that these people are refereeing their own papers. After all, Michael 

Mann was an editor of the Journal of Climate and he publishes a lot of 

his papers in the Journal of Climate. It is pretty hard to say well, I am 

going to take this guy who is well known and I am going to start 

rejecting his papers. That is a pretty hard thing to do. 

 MS. BALDWIN. Well, Dr. Wegman, my question was, is this a 

hypothesis or is it a conclusion that you have drawn? If it is a hypothesis 

that would need to be investigated further and of course earlier we heard 

Dr. North’s response to a question about what this--how fiercely 

competitive people early in their scientific careers, late in their scientific 

careers are. I am a granddaughter and a niece of two researchers and I 

feel like I have had a lifelong sense of how competitive these things, 

even if you have a very narrow perspective. But are you reaching a 

conclusion or a hypothesis? 

 DR. WEGMAN. No, this is a hypothesis. 
99

 MS. BALDWIN. Okay. Then if I understand you correctly, there are 

at least two problems with the Wall Street Journal’s statement in an 

editorial last week that your “conclusion is that the coterie of the most 

frequently published climatologists is so insular and so close-knit that no 

effective independent review of the work of Mr. Mann is likely,” because 

first your social network analysis wasn’t of climatologists but a much 

narrower group of temperature reconstructionists, and second, your 

social network analysis did not allow you to reach a conclusion about the 

independence of review of Dr. Mann’s work. 

 DR. WEGMAN. I think that there is--you know, in some sense you 

are putting words in my mouth but I think there is evidence-- 

 MS. BALDWIN. Well, the Wall Street Journal-- 

 DR. WEGMAN. Let me finish. I think there is evidence based on this 

social network analysis, based on the real climate.org web log, based on 

the general reaction of Dr. Mann and, for that matter, Dr. Bradley and 

Dr. Hughes to the initial inquiries to the committee that there is a tightknit group of people who are interacting with each other and who frankly 

don’t seem to like to be criticized. 

 MS. BALDWIN. Dr. Wegman, I have an additional question. I think 

it has been touched on before but I just want to get some real clarity on 

this. I understand that the data that you used is based on Mann’s 1998 

and 1999 studies. In the recent years Dr. Mann has altered his 

reconstructions using different methods and proxies. Each time he has 

been able to reach virtually the same conclusions. Did you analyze any 

data from Mann’s later studies or those from other reputable climate 

scientists who have reached similar conclusions? 

 DR. WEGMAN. We did not attempt to reproduce any of the later 

material. However, what we did do was look at the proxies that were 

used and we looked at the series of papers beginning actually with Jones 

and Bradley, I think it was, in 1993 and compared the proxies that they 

were using and the methodologies that they were using. Basically Mann 

articulates I believe in his 2005 paper the set of papers that used the 

climate field reconstruction, the CFR methodology, and also uses the 

CPS methodology. Those are articulated by Mann, not by me. 

 MS. BALDWIN. But you used the 1998 and 1999 studies? 

 DR. WEGMAN. We were asked to address the issues in 1998 and 

1999, yes. 

 MS. BALDWIN. I would now yield my remaining time to Mr. Inslee, 

who requested that. 

 MR. INSLEE. Thank you. Doctor, I have been trying to figure out 

how to characterize the situation, and the best I can do is to say that we 

don’t debate gravity anymore and we should not debate whether there is 

a human contribution to global warming anymore, and the way I look at 
100

this is sort of like if you had reviewed Newton’s Principia where he laid 

out the basic laws of physics that we have now based, until quantum 

mechanics came around, most of our science, if you found a statistical 

flaw, which I will bet you could if you looked at the whole Principia that 

didn’t meet sort of regular statistical proofs right now, you might come 

into Congress, if the Republicans controlled Congress in 1695, anyway, 

and say, you know, I found this statistical flaw in this one little piece of 

Newton’s theory, even after we have a mountain of evidence that gravity 

is a fact, not a theory, upon which we base our science, and that is the 

reason that you are not urging, as I understand it, us to reject Dr. Mann 

and his group’s conclusion, that humans are a causative factor for global 

warming. The reason you are not asking us to reject that conclusion is 

that you recognize that you have found what you believe is a statistical 

flaw in one study but it does not contravene the mountain of evidence 

that says global warming is caused a not insignificant part by human 

activity. Is that a pretty fair metaphor for this? 

 DR. WEGMAN. Well, I--you know, the issue is, I was asked a very 

specific question. I came here to testify on a very specific question. And 

you are asking me to testify off of my level expertise and I-- 

 MR. INSLEE. Well, let me just ask you-- 

 DR. WEGMAN. --am not going to do that. 

 MR. INSLEE. Let me ask you a quick question. If you found a 

statistical flaw in the Principia published by Sir Isaac Newton in 16 

whenever it was, would you suggest that we reject the theory of gravity? 

 DR. WEGMAN. I would not suggest anything because that was not 

the question I was asked and that is not the reason I am here. 

 MR. INSLEE. Well, unfortunately, this is the reason-- 

 DR. WEGMAN. I mean, if you are asking me as an ordinary citizen-- 

 MR. INSLEE. No, I want you to make sure you understand the reality 

of the situation. I am giving you all the sincerity that I can give to you. 

But the reason you are here is not why you think you are here, okay. The 

reason you are here is to try to win a debate with some industries in this 

country who are afraid to look forward to a new energy future for this 

Nation, and the reason you are here is to try to create doubt about 

whether this country should move forward with a new technological 

clean energy future or whether we should remain addicted to fossil fuels. 

That is the reason you are here. Now, that is not the reason individually 

why you came but that is the reason you are here. Thank you very much. 

 MR. WALDEN. The gentleman’s time has expired, which is the 

reason I am here to keep control of this. 

 DR. WEGMAN. But I didn’t get to answer. 

 MR. WALDEN. Well, I will just give Dr. North a question. Does 

anybody still study gravitational theory in the scientific community? 
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 DR. NORTH. Yes, they do. 

 MR. WALDEN. If you find-- 

 DR. NORTH. It is a very active field in physics. 

 MR. WALDEN. Do you ever learn anything new? 

 Dr. North. Absolutely. Things are being learned all the time. 

 MR. WALDEN. And are you allowed then to publish new findings 

that might contradict old findings? 

 DR. NORTH. Absolutely. 

 MR. WALDEN. Okay. Good. Science moves forward. Now, I have 

to apologize. I was in another markup earlier and so I missed some of 

the questions and some of the opening statements although I am familiar 

with both of your gentlemen’s testimony. But I just want to make sure I 

understand one sort of underlying piece, and that is, did you both indicate 

that Dr. Mann’s underlying statistical analysis was incorrect? Dr. 

Wegman? 

 DR. WEGMAN. Yes. 

 MR. WALDEN. Dr. North? 

 DR. NORTH. Well, we found that it is not--there were many choices 

to make. They probably didn’t make the best choice when they did the 

analysis the way they did. 

 MR. WALDEN. What do you when-- 

 DR. NORTH. When their claims are wrong, it just means they are not 

very convincing because of the way they did it. 

 MR. WALDEN. Okay. Now, I am not a scientist so tell me-- 

 DR. NORTH. That was nuanced. I apologize. 

 MR. WALDEN. No, no. Tell me what that means as a layperson, as a 

lawmaker, when you say they made choices in their-- 

 DR. NORTH. Well, when you approach a problem like this, there are 

many choices when you try to do a statistical analysis and so there are 

many choices as to should you deter in the data in the 20th Century or 

should you not. Should you use this kind of validation procedure or a 

different one. 

 MR. WALDEN. Right. 

 DR. NORTH. And in fact, one series of papers by Burger and 

Cubasch actually looked at the situation and decided there were 64 

different ways you could have done it, and had you chosen--and so they 

actually showed us a family of extrapolations you would have gotten 

using all of those different-- 

 MR. WALDEN. And did they all look like a hockey stick? 

 DR. NORTH. They all--well, I mean, to me they do. But, it is a bit 

curved. It is not exactly like the hockey stick but within the error bars, 

and by the way, in the Wall Street Journal article, there is really a 

mistake made in that graphic, and that has to do with the error bars. It 
102

does show--these two graphics are in our reports, the same ones that are 

in the Wall Street Journal report, and if you look at the Wall Street 

Journal article, they don’t put the margin of error in there, which is 

really important. 

 MR. WALDEN. What is the margin-- 

 DR. NORTH. I mean, it is totally irresponsible to do this without the 

margin of error. 

 MR. WALDEN. Okay. Can I ask you, what should that be so we 

clarify the record, the margin of error? 

 DR. NORTH. The margin of error is the plus-minus 95 percent 

confidence interval. 

 MR. WALDEN. And that is what it should have been here? 

 DR. NORTH. That is right. 

 MR. WALDEN. The plus or minus-- 

 DR. NORTH. And so when you look at the family of curves, they all 

fall pretty close to that gray area in this graphic but in the Wall Street 

Journal article, the gray is removed. 

 MR. WALDEN. Now, in the Wall Street Journal article too, they 

make a reference to a McIntyre and McKitrick critique, and I guess, have 

you reviewed that one, Dr. North 

 DR. NORTH. Oh, I am familiar with their work and, in fact, Mr. 

McIntyre is here. He will be testifying later. 

 MR. WALDEN. Did he present to your panel? 

 DR. NORTH. Yes, he did. And in fact-- 

 MR. WALDEN. Can their data be replicated or the results be 

replicated? 

 DR. NORTH. Well, what they did was a critical study, somewhat like 

the Wegman report, and I think they did an honest job. It was a nice 

piece of work. 

 MR. WALDEN. Dr. Wegman-- 

 DR. NORTH. I have no complaint about what they did. 

 MR. WALDEN. In terms of replicating data or replicating studies, my 

understanding is, it is difficult to replicate the Mann study but it was 

possible to replicate the McIntyre and McKitrick study. 

 DR. WEGMAN. Yes, that is correct, and we did so. 

 MR. WALDEN. I want to move on to a little different topic and that is 

related to data sharing because I have run into this in another committee 

where I am a subcommittee chair on science and that was, there was a 

dispute--imagine that--over a report that was run out and published and 

somebody else tried to get the data to see if they could replicate it and 

there was a long delay and it was a real problem, and I know Dr. North, 

in your report, you say--page 112 of the surface temperature 

reconstructions the past 2,000 years, you make a comment that says, 
103

“Our view is that all research benefits from full and open access to 

published data sets and the clear explanation of analytical methods is 

mandatory. Peers should have access to the information needed to 

reproduce published results so that increased confidence in the outcome 

of the study can be generated inside and outside the scientific 

community,” and you make that comment. Then I note-- 

 DR. NORTH. I was about to read it to you. 

 MR. WALDEN. What is that? 

 Dr. North. I was about to read it to you. 

 MR. WALDEN. Well, we can do it in the key of C next time together. 

Then Dr. Wegman, on page 4 of your testimony, you say, “Additionally, 

we judge that sharing research materials, data, and results was 

haphazardly and grudgingly done,” and further I believe it on page 66, 

there is a reference--there is a question, “Has the information needed to 

replicate their work been available, and the answer is, in our opinion, no. 

As mentioned earlier, there were gaps in MBH98.” Do we have a 

situation here where it was very difficult to get the data to do replication, 

and if so, why, do you think? 

 DR. WEGMAN. As I mentioned earlier, we did download the data. 

We have seen the letter that Dr. Mann replied to the committee which 

basically took the position that this is my intellectual property and I don’t 

have to share it and the National Science Foundation tells me so. 

 MR. WALDEN. Is that the case, Dr. North? Do you speak for the 

National Academy of Science? 

 Dr. North. No, no. 

 DR. WEGMAN. But the issue is that if there is free and open access to 

the data and the materials that are associated with the data, it makes the 

policing of this kind of activity, the referees for the hockey game as I 

said earlier, it makes it so much easier to be able to do that, and we think 

that that is an important aspect of the scientific enterprise. 

 MR. WALDEN. How do statisticians do these sorts of evaluations? 

Do you share data among yourselves? 

 DR. WEGMAN. Typically in terms of computer code, there are two 

places that people typically go to. There is an electronic journal called 

the Journal of Statistical Software which is a refereed journal. People 

submit their code to that journal. There is also a website that people 

submit both data and code to. 

 MR. WALDEN. I don’t know if you have had a chance to see Mr. 

Crowley’s testimony whom we will hear from later today but he has 

some rather unflattering statements about your report. I know it is 

shocking that different scientists have different views of different 

scientists and their reports. He says that there are a number of flaws in 
104

your report and goes on to list some. Do you have any comment on the 

testimony we are going to hear later since you won’t be back at-- 

 DR. WEGMAN. Well, I probably will be here but not sworn in or at 

least-- 

 MR. WALDEN. Right. You will still be under oath, they inform me. 

 DR. WEGMAN. I understand where Dr. Crowley is coming from. He 

is in a relatively awkward position of having to defend the position that 

Dr. Mann had taken. 

 MR. WALDEN. Why? Why is that an awkward position? 

 DR. WEGMAN. Well, because you have heard from both of us this 

morning that there are fundamental flaws in the Mann work and to come 

and have to defend that is an awkward situation, I think. Frankly, I 

would not have wanted to get the letter that Dr. Mann got and the other 

coauthors because that is kind of not on the radar screen of typical 

scientists. You know, you write a paper and you have a file somewhere 

and right now my dean is telling me that we should throw everything that 

is more than 3 years old, we shouldn’t keep it in the file drawers because 

we have space considerations, we have to keep space, but I--you know, I 

think I jotted down the phrases he used about me which is that I am naive 

and--I think it was naive and uninformed. I don’t think those are 

accurate statements because he has never talked to me either. He has 

only read what we wrote and he has read it without the interaction with 

us as statisticians so we will see what happens this afternoon. 

 MR. WALDEN. Is he a statistician, do you know? 

 DR. WEGMAN. Not that I know of. 

 MR. WALDEN. You made a comment about the potential conflict 

with Dr. Mann being an editor of a journal and also submitting work to 

that journal. 

 DR. WEGMAN. Yes. 

 MR. WALDEN. Do you know if he proofs his own work or does he 

hold himself-- 

 DR. WEGMAN. Generally the process is that an editor of a journal 

will submit it, pass on the material to an associate editor who will in turn 

select some referees. That process is typically what happens in a journal. 

When I was editor of a journal, I refrained from submitting anything to 

the same journal that I was editor of simply because it puts pressure on 

the associate editors and referees to approve. 

 MR. WALDEN. Gentlemen, we appreciate your testimony and I will 

go to the full committee Chairman, Mr. Barton. 

 CHAIRMAN BARTON. Well, I don’t want to do a second round 

because we have subjected these two gentlemen to close to--what is it--

four hours of dialog. I would want to--I want to ask unanimous consent 

to ask Dr. North to comment on the recommendations that Dr. Wegman 
105

gave and I also want to renew my request that the Enders Robinson email be put into the official record. 

 MR. STUPAK. Mr. Chairman, as to the e-mail of Robinson, I have no 

problem with that being entered in the record, but if you are going to ask 

further follow-up questions, I know there is one two further follow-up 

questions on this side we would like to ask. 

 [The information follows:] 
106
107
108

 CHAIRMAN BARTON. I am sorry. I got the first part. I didn’t get 

your second part. 

 MR. STUPAK. I said there are one or two follow-up questions-- 

 CHAIRMAN BARTON. Oh, you all have some follow-up? Okay. 

Could I be recognized then for 5 minutes? Could we do the second-- 

 MR. STUPAK. No objection. 

 CHAIRMAN BARTON. Five minutes so that we can let this panel go. 

 MR. WALDEN. The Chairman is recognized for 5 minutes. 

 CHAIRMAN BARTON. Thank you. Dr. North, Dr. Wegman makes 

four recommendations on page 6 of his testimony. Do you have that in 

front of you? 

 DR. NORTH. I think I have copied them out of there so I think I have 

them here, yes. 

 CHAIRMAN BARTON. Could you comment on each recommendation, 

whether you think his recommendations have merit? 

 DR. NORTH. Let--I will try to do that. So recommendation one was 

when massive amounts of public monies and so forth are at stake, 

academic work should have more intense level of scrutiny and review. 

Well, nobody would argue with that, of course. It is especially the--we 

always want to do things better. It is especially the case that authors of 

policy-related documents like IPCC and so forth should be-- 

 CHAIRMAN BARTON. He says the review should not be the same 

people that constructed the academic paper. 

 DR. NORTH. So that is a really very interesting question and subject. 

You know, when you ask for an expert scientific review of the state of 

art or the science and you go to the world experts, and that is what the 

IPCC tries to, you will find authors of the chapters who have also 

coauthored some of the papers involved and indeed I think sometimes 

they do promote their own work. That is human nature. We all know 

how that works. So that process isn’t exactly perfect, but I cannot 

imagine a better, more efficient way to pull several thousand scientists 

together and they have to meet repeatedly several times over the course 
109

of a year, over the course of a couple of years. One time we actually had 

one of the meetings in College Station some years ago and so people get 

tired of this. It is really hard to work. I mean, it sounds like it is fun but-

- 

 CHAIRMAN BARTON. To the largest extent possible, if you can-- 

 DR. NORTH. So it is very, very hard to-- 

 CHAIRMAN BARTON. Sometimes there is not but two experts in the 

world and so, you know-- 

 Dr. North. That is right. 

 CHAIRMAN BARTON. But if it possible-- 

 Dr. North. So, you know, you could go another way and ask a 

situation like the academy did. We had a small committee of 12 people 

who were picked on the basis that they were not connected with any of 

the--I mean, as little as we could possibly do, connected with any of the 

principals and the problem, so-- 

 CHAIRMAN BARTON. But what about his recommendation number 

two that there should be a more comprehensive and concise policy on 

disclosure and that data collected under Federal support should be made 

publicly available? 

 DR. NORTH. This is not a bad idea, and in fact, I think Tom Karl is 

going to address that. 

 CHAIRMAN BARTON. And then his recommendation number three is 

that if you are doing review and doing studies that include some sort of a 

statistical approach on which your conclusions are based, that there 

should be statistical evaluation of the statistical practices. He says it 

should be a mandatory part of all grant applications. 

 DR. NORTH. I think that is a little over the top. I think-- 

 CHAIRMAN BARTON. A little over-- 

 DR. NORTH. I think carrying this to the Federal drug approval 

process is-- 

 CHAIRMAN BARTON. So you would-- 

 DR. NORTH. It is not a good analogy. 

 CHAIRMAN BARTON. Well, what about his last one, that emphasis 

should be placed on the Federal funding of research related to 

fundamental understanding of the mechanisms of climate change. I think 

you would accept that. And that the funding should focus on 

interdisciplinary teams and avoid narrowly focused discipline research, 

and he is trying to broaden the field so that it is not the same group of 

people talking to the same group of people. 

 DR. NORTH. Well, it seems to me the two statements are 

contradictory. The first one says you should narrow the field and the 

second one says you should broaden the field, so, I mean-- 

 CHAIRMAN BARTON. You are not real fired up about-- 
110

 DR. NORTH. I want to see more money come into the field. I think 

we all would like to see that. That is great. But I am not sure that one 

was very well formed out. 

 CHAIRMAN BARTON. Well, let me before I yield back my 52 

seconds say why we are doing this hearing, because I have been here 

almost the entire time for every question and every statement. I missed a 

little bit but not much. I don’t disagree fundamentally with some of what 

my friends on the minority side have stated. There is no question that the 

temperature is warmer today than it was in 1850. I think there still is a 

question about the cause of that, and some of these reports and studies 

that purport not only to state the fact of the warming but the 

consequences of it, I think should be open to honest public debate 

without challenging the merits. Where I disagree with some of my 

friends on the minority side is that before we make massive public policy 

changes that affect every American citizen in this country, we need to 

have with the highest degree of certainty that the facts really are the 

facts. Now, I have right here a magazine article from Newsweek April 

28, 1975, that is talking about the cataclysmic consequences of global 

cooling. Now, that is 30 years ago and the science has changed. Now 

we are talking about the cataclysmic consequences of global warming. If 

the United States has ratified Kyoto and if the United States Congress 

working with the Administration had begun to implement Kyoto, it 

requires a reduction in CO2, I believe about 30 to 40 percent, and that 

means you are not going to have coal-fired power plant combustion in 

many parts of this country. It means that you are going to have to reduce 

the automobile emissions of the vehicles that are made in Michigan. 

And before we go down that trail, I think it is imperative that we do the 

oversight and do the science and talk--I am not opposed to talking to the 

climatologists but I agree with Dr. Wegman that we need to make sure 

that it is an interdisciplinary approach so that we really get everything on 

the table. If that shows that the human correlation is beyond dispute, 

then I believe we do have an obligation to take what steps we can to 

remedy that but I don’t believe that science yet shows that. With that I 

yield back, Mr. Chairman. 

 MR. WHITFIELD. Thank you, Mr. Chairman. At this time I 

recognize Mr. Stupak for-- 

 MR. STUPAK. Thank you, Mr. Chairman. Chairman Barton, and I 

take it, that means we are going to have a lot more hearings on global 

warming because there are a lot more reports than just Dr. Mann’s 1998-

1999 report, so if we are going to come to those policy decisions, I would 

hope we would have more than just one hearing about one report and 

look at the whole spectrum of reports on global warming. Dr. North, if I 
111

may, the IPCC process, is that based upon sound science, sound 

methodology? 

 DR. NORTH. In my opinion, when you go out and ask the active 

scientists in the field to give you an assessment, they select themselves 

and it has been my experience in the three that have been produced that 

they do just that. I had very little to do with the last one. I served a 

referee on-- 

 MR. STUPAK. Sure. 

 DR. NORTH. But the one before, I had a little bit more to do with it, 

but I think the process is pretty good. You know, it is human. It has 

some flaws in it but I think I--it is probably the most massive assessment 

of this kind that has ever been made. It is remarkable that you get people 

to do that. And I will tell you this, people are tired of participating. It is 

a lot of work. Traveling to these countries and having these workshops 

and meetings, it is a lot of work and so to actually ask people who are not 

experts to come in and read all of those papers that they weren’t involved 

in, that is asking a lot of people and you won’t get anybody to do it 

because there is no money for this. There is no pay for this. 

 MR. STUPAK. Okay. 

 DR. NORTH. Incidentally, the academy report people didn’t get paid 

anything either. 

 MR. STUPAK. Dr. North, you also mentioned the hockey stick 

hokum that was in the Wall Street Journal last Friday in which they 

claimed that the graph from 1990 that we have talked a lot about today 

showing the warming period in the Middle Ages, the Wall Street Journal

goes on to say that in 1990 the consensus “held that the medieval warm 

period was considerably warmer than the present day.” It has been a 

long hearing here today but is there any scientific evidence from anyone 

that supports the claim that temperatures in the Middle Ages were higher 

than they are today? 

 DR. NORTH. There may be some locations on the Earth but so why 

do we care about the global average? You know, that has come up a 

couple of times. Because if CO2 is the reason, it is a global forcing so 

you expect the response to be at the global scale. This is really 

important. That is why--I mean, nobody takes a picnic at the global scale 

but the scientists are very interested in what happens to the global 

average because that is what is being forced by the CO2. So that is why 

we are so fixated on the global average and getting large-scale averages. 

It is easier to measure it because when make measurements at a lot of 

locations, a lot of the random errors cancel out. That is good. The same 

thing happens with our models. They do that better than anything else. 

 MR. STUPAK. Dr. Wegman, I thought I heard you say, and correct 

me if I am wrong, when you are making comparisons you are saying that 
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you used--I think it was figure 4 on your chart--that you used North 

American factors in your analysis with Dr. Mann’s? 

 DR. WEGMAN. Dr. Mann himself used North American--what he 

called the North American PC1 proxy which was a composite based on 

the principal of component methodology of North American tree rings. 

 MR. STUPAK. Sure. 

 DR. WEGMAN. And that is what--we replicated that, yes. 

 MR. STUPAK. So in your analysis, you used just North American, 

right? 

 DR. WEGMAN. We used the North America proxy. 

 MR. STUPAK. The P1, the P2-- 

 DR. WEGMAN. The PC1-- 

 MR. STUPAK. --and the P3? 

 DR. WEGMAN. Yes. 

 MR. STUPAK. PC. I am sorry. PC1, PC2. But didn’t really Dr. 

Mann use 12 proxy indicators from all over the world? 

 DR. WEGMAN. We were not trying to do paleoclimate 

reconstruction. We were trying to illustrate what happened if you did-- 

 MR. STUPAK. Sure. 

 DR. WEGMAN. --the principal component-- 

 MR. STUPAK. Dr. Mann used 12 proxies to come up with his 

analysis. You took three from North America. Is it fair to say then that 

using from throughout the world would have a different result than if you 

just looked at the three in North America? 

 DR. WEGMAN. Let us be clear. He was doing Northern Hemisphere, 

NH, reconstruction. He wasn’t doing global reconstruction in-- 

 MR. STUPAK. But if you take a look at his report, and I know you 

did, they talk about Tasmania, taking tree rings from there, Morocco, tree 

rings from there, France, the Greenland stack core which we talked 

about, the ice core, polar Urals, again, the tree ring density. It seemed to 

me he took them from all over the world where your focus is only on 

North America. So how could you make the comparison then when you 

use global statistics as opposed to just one part of the world in doing your 

measurements? 

 DR. WEGMAN. Well, I am not sure I understand what you are getting 

at. The-- 

 MR. STUPAK. From a layperson who is not a statistician, I would 

think if you are going to compare Dr. Mann’s statistics, if you will, you 

would use all of them as opposed to-- 

 DR. WEGMAN. Our discussion-- 

 MR. STUPAK. --just three of them. 

 DR. WEGMAN. Our discussion is on Dr. Mann’s methodology, not 

his conclusions in terms of paleoclimate-- 
113

 MR. STUPAK. But you charted, did you not? Didn’t you use X axis, 

Y axis and chart it all out and that is why you got different than the 

hockey stick? You only used three where he used 12. 

 DR. WEGMAN. No, no, no. We used the same data to get the hockey 

stick in that one figure-- 

 MR. STUPAK. From North America? 

 DR. WEGMAN. From North America. 

 MR. STUPAK. And he took his from the worldwide. 

 DR. WEGMAN. No, no, no. 

 MR. STUPAK. That is not what table one says. 

 DR. WEGMAN. What we said was that we used that comparison 

chart that we had that showed the hockey stick. The comparison was 

meant to show that if-- 

 MR. STUPAK. Right here, yes? 

 DR. WEGMAN. That is it. If you go to the top chart by using his 

methodology on the same set of data and the bottom chart is what you 

would get if you did the centered data, if you did it properly 

mathematically. So the point-- 

 MR. STUPAK. But yours is only on PC1, PC2-- 

 DR. WEGMAN. So is his-- 

 MR. STUPAK. --and PC3. 

 DR. WEGMAN. --in that picture. 

 MR. STUPAK. So you are saying that picture was only PC1, PC2-- 

 DR. WEGMAN. That is-- 

 MR. STUPAK. --PC3 from Mann. 

 DR. WEGMAN. We are using exactly the same data in the top picture 

and the bottom picture. 

 MR. STUPAK. Okay. Thank you. 

 MR. WHITFIELD. The gentleman’s time has expired. Dr. North, in 

the testimony today, there seems to be universal agreement that the 

temperature is going up and in the last century it went up about one 

degree Fahrenheit, I believe is what most people have agreed to, and 

there has also been a lot of testimony that for a period of time between 

1500 to 1800, whatever, that there was a period in which there was a 

cooling off. So I just want to zero in on this. You have said and others 

have said and I think there is universal agreement that we are going 

through a warming trend, and it has been said by some people that that 

might not be surprising coming from a cooling off period that you would 

normally get warmer going through a warming trend. So the question 

that I would ask, as you look into the future, how much warmer can it 

become before it is something that we should really be alarmed about 

from your viewpoint, from experiences? 
114

 Dr. North. Well, I will say this--well, two things. One is about the 

Little Ice Age and is it simply a recovery. In other words, is the Earth’s 

temperature a kind of oscillating thing and that the slope upward now is 

just recovery from a Little Ice Age which was apparently maybe some 

natural phenomenon. Well, I am not sure that that is actually the right 

picture. We don’t know exactly the true origins of the Little Ice Age but 

some studies, in fact, a very good one by Tom Crowley, who will be 

speaking later, suggests that this is due to a series of volcanoes during 

that period which caused a cooling. It was not a great cooling but some 

cooling. So now it is--you know, now that we are going through a period 

when they are not as frequent as they were at that time, the Earth is 

simply warming back toward equilibrium from that. But now we are 

also forcing the warming with the CO2 and other greenhouse gases that 

are being emitted into the atmosphere. So while if we look at the future, 

what we might think is that by the end of this century the warming, if it 

continues and we do nothing about it, will probably be somewhere 

between about three degrees Fahrenheit and about eight degrees 

Fahrenheit. Well, three may not be so bad. Eight would be pretty bad, 

pretty bad. And so in fact, even three is not as benign as you might 

think. You know, you can look at--for us in our everyday life, three 

degrees Fahrenheit doesn’t seem to mean anything. People after all live 

in Minneapolis and they live in Houston. But it really does affect 

conditions. Tree lines move. There is a tree line that runs right up the 

center of the United States along I-35 between Austin and Minneapolis. 

 MR. WHITFIELD. Right. 

 DR. NORTH. That tree line can move hundreds of miles depending 

on just a couple of degrees or changes in moisture. So what looks like to 

us in our everyday life not very much, if these things persist for a long 

time, there are broader ecological responses at these kind of low 

frequencies that are important. So, I don’t know all of the bad or good 

things that might happen. I mean, there would probably be some winners 

and losers in a situation like this. And I have to confess to you, I don’t 

know enough about it. 

 MR. WHITFIELD. But you know as we grapple with this, we have 

like a 250-year reserve of coal in America. We all want to be less 

dependent on foreign oil. There are some people that don’t want to use 

fossil fuel at all, it would be better to come up with new innovation, new 

technology and move on to something cleaner and that can be a goal of 

ours. In representing a coal area of the country, I have a lot of 

constituents who come up to me and they will say well, sure, there is 

some carbon dioxide caused by human beings but there is more carbon 

dioxide emissions caused by natural processes. Now, I would just like to 
115

get your views on that comment. Is there any basis for that or is that just 

somebody-- 

 DR. NORTH. There is a lot of carbon dioxide emitted into the 

atmosphere every year and a lot of absorbed back into the system every 

year, in fact, many times what humans put in. The problem is this. 

There was an equilibrium established between what is going out and 

what is drawn back down every year by the system. The oceans and the 

biosphere, there is this exchange that goes on all the time. The problem 

with this is that the time scale, the time constant, as we say, is quite long. 

It takes a couple of hundred years for these adjustments to re-establish 

themselves, so if you dump in the carbon dioxide much more rapidly 

than the system can accommodate, it builds up in the atmosphere. If we 

were to wait several hundred years, then things may come back down, 

but we don’t have that luxury. So the fact is, we are pouring it in there 

faster than the system can dispose of it. That is the way-- 

 MR. WHITFIELD. Thank you very much. Who is next over here? 

Mr. Inslee. 

 MR. INSLEE. Thank you. Just on that note, Dr. North, I have heard 

the CO2 that we put in today in the atmosphere could be there as long as 

100 years? 

 DR. NORTH. A couple of hundred years. 

 MR. INSLEE. I want to use Dr. Wegman’s expertise to try to 

understand an interesting phenomenon. You talked about social 

networking. I thought you could give us some insights about that. Dr. 

Naomi Oresky of the University of California at San Diego published a 

study in Science magazine some time ago. She and her team selected a 

large random sampling of 928 articles about global warming that have 

been published in peer-reviewed scientific journals and she wanted to 

look at what they said, these 928 randomly selected peer-reviewed 

articles about whether they accept or reject or question the idea that 

humans are contributing to global warming. Of 928 studies, what do you 

think percentage questioned the proposition or rejected or even cast 

doubt on the proposition that humans were causing global warming? 

What do you think, Dr. Wegman? What percentage? Zero. Zero 

percentage of the scientifically peer-reviewed articles drew the same 

conclusion that my good friend Joe Barton drew, that there is doubt 

about this. Zero. Now, my question is, another study looked at 636 

randomly selected articles about global warming chosen from the New 

York Times, the Washington Post, the L.A. Times, and the Wall Street 

Journal. Of those randomly selected publications and those wellrespected publications, what percent cast doubt as to the cause of global 

warming? What do you think? 

 DR. WEGMAN. Probably about 50 percent. 
116

 MR. INSLEE. Fifty-three percent. You win the prize for the day of 

closest guess, or as you say, estimation. Over half of the popular articles 

suggested there is a significant question as to whether or not humans are 

contributing to global warming but zero percentage of the peer-reviewed 

science. Now, I believe that is one of the reasons that Congress has not 

acted on this because frankly, the press is creating doubt where there 

isn’t any. So the question of a social scientist, the social networks, do we 

have a problem with the press that are hanging out in the bars all together 

too much too like the climatologists or what is your explanation for this 

huge anomaly? 

 DR. WEGMAN. Well, there is no doubt in my mind that there are two 

camps in the publication literature as well in the popular press and, they 

are competing just like I suggested that academics compete in social 

science that there is two networks that are trying to promote different 

agendas. 

 MR. INSLEE. Well, my point is, I hope the press starts to get off the 

story of doubt and get on the story of a scientific consensus which exists 

in those 900 articles, and no one should report this hearing unless they 

say that because both you and Dr. North and every single person who is 

going to testify today is going to say that there is a scientific consensus 

that humans are responsible for at least a portion of the global warming 

that is taking place. Now, I want to ask Dr. North if we can put this slide 

up here about the CO2 and go back to the one he had there just a moment 

ago. Dr. North, I gave some of a very inarticulate description of how 

carbon dioxide works to trap energy in the planetary system. Could you 

give a little better explanation? We will see that all the scientists, 

everybody has projected levels of approximating double of pre-industrial 

times if we don’t change our course. Could you explain in a little better 

way how carbon dioxide affects the energy balance of the Earth? 

 DR. NORTH. I will try. First of all, carbon dioxide is well mixed in 

the atmosphere so it isn’t just lying down on the surface. It is very well 

mixed. This process takes a few months but--and in fact, if you emit it in 

one hemisphere of the Earth, it takes about a year or two before it 

homogenizes throughout the world. So whether you emit your gas, your 

CO2 in Texas or anywhere else, it doesn’t make any difference. It winds 

up homogeneous throughout the world. So what happens now? So the 

sunlight comes in, passes right through the CO2 and warms the ground. 

The ground in contact with the atmosphere through latent heat release, 

that is, evaporation from the surface and just sensible heat convection to 

the surface warms the atmosphere. So and then we establish an 

equilibrium because the radiation going out to space matches exactly 

what comes in over a long-term average. So that is the energy balance of 

the Earth. Now, suppose you turn up the carbon dioxide a little bit in the 
117

atmosphere. Well, one thing that happens is, since the gas homogenizes 

all through the planet, all around the planet. The level up in the 

atmosphere where the CO2 emits to space goes up a little bit and higher 

in the atmosphere, 50 meters or something like that if you double it. 

That means it emits from a cooler place in the atmosphere once you have 

doubled it. That means the amount going out isn’t as much as it was 

before. So what happens is, you have to warm the surface in order to 

regain the equilibrium. That is a complicated explanation. But in the 

process right in the middle of this, you warm the planet a little bit, more 

water comes into the atmosphere from the oceans and other wet surfaces. 

Water vapor is also a greenhouse gas so this process gets amplified 

maybe a factor of two. So basically, I mean, what you said about the 

blanket is more or less right. A slightly more technical discussion is 

well, when you put in more of this stuff, it now emits from a higher place 

from a cooler surface rather than a warm surface so the radiation out to 

space is less, you have got to warm up the planet to match again. Sorry 

for such a long-winded answer. 

 MR. WHITFIELD. Thank you. The gentleman’s time has expired. 

Mr. Walden. 

 MR. WALDEN. Thank you very much, Mr. Chairman. Dr. North, 

what are some of the biggest natural emitters of CO2? 

 DR. NORTH. Well, there are many. Decaying biological matter is 

one, so rotting, decaying at the floor of the great forests and all over the 

planet, respiring animals and so forth. So there are many-- 

 MR. WALDEN. What about forest fires? 

 DR. NORTH. Forest fires contribute but not nearly as significant as 

these other natural products, and also volcanoes of course emit CO2 but 

on our scale, I mean, that is sporadic. It does happen from time to time 

and of course it is the historical origin of CO2 in our atmosphere but-- 

 MR. WALDEN. And what consumes-- 

 DR. NORTH. --it is not important. 

 MR. WALDEN. What consumes CO2? 

 DR. NORTH. So what consumes CO2 is the biological matter, the 

photosynthesis process, so sunlight is combined with-- 

 MR. WALDEN. Plant matter-- 

 DR. NORTH. --chlorophyll in the plant leaves and that is converted 

to--so it removes CO2. 

 MR. WALDEN. So younger, healthier plants and trees consume more 

CO2 than older, dying-- 

 DR. NORTH. As they grow, they consume. Right. You are making 

wood with the carbon. 

 MR. WALDEN. Because I also in my other part in the Congress chair 

the Subcommittee on Forests and Forest Health and we see-- 
118

 DR. NORTH. That is very important. 

 MR. WALDEN. --these overgrown, decaying and dying forests. We 

see fires occur that emit far more than CO2. They emit a lot of other 

noxious gases. They have-- 

 DR. NORTH. Sure. 

 MR. WALDEN. You know, the smoke will settle on the valleys. I 

mean, it causes all kinds of problems and then the decaying matter sits 

there for 3 or 4 years rather than being processed and a new forest 

planted sooner. Are you aware of any research that would indicate that 

by planting sooner, getting a healthy forest a start faster, you might begin 

consuming carbon quicker than just leaving it to regenerate naturally? 

 DR. NORTH. Well, you are getting way off from my field but, 

intuitively, yes. 

 MR. WALDEN. All right. Dr. Wegman, in your report, it is page 27, 

you say a common phrase among statisticians is correlation does not 

imply causation, and you go on to say the variables affecting Earth’s 

climate and atmosphere are most likely to be numerous and confounding, 

making conclusive statements without specific findings with regard to 

atmospheric forcings suggests a lack of scientific rigor and possibly an 

agenda. What do you mean by that? 

 DR. WEGMAN. Well, as we--when we were talking about tree ring 

growth, for example-- 

 MR. WALDEN. Right. 

 DR. WEGMAN. --there are many, many factors. Moisture as well as-

- 

 MR. WALDEN. Carbohydrates. Right. 

 DR. WEGMAN. And nitrates, for example, that are emitted into the 

atmosphere. All of those affect tree ring growth. 

 MR. WALDEN. Can you pinpoint temperature in a tree ring? 

 DR. WEGMAN. Well, presumably there is some element of that. I 

am not an expert on tree ring dendrology but presumably all other factors 

being equal, if things are warmer, there is more sunlight, there is a longer 

growing season, presumably the trees are going to have wider tree rings. 

So the issue though is the confounding factors. If you simply say that 

this tree ring growth, what is called the late wood density, is higher, that 

means the temperature is higher and ignore all the confounding factors, 

you are certainly not teasing out what really is the temperature. 

 MR. WALDEN. Now, we have seen the slide a couple of times from 

my colleague from Washington, Mr. Inslee, that shows CO2 levels back 

160,000 years. Can either of you tell me, how do we know with 

precision what happened 160,000 years ago? 

 DR. NORTH. Would you like me to-- 
119

 MR. WALDEN. Sure. Maybe from you, Dr. Wegman, statistically, 

what does that mean and how do you evaluate it, and Dr. North, from 

you maybe, the science behind-- 

 DR. WEGMAN. Well, we have read actually Bradley’s work on this 

material so essentially when snow gets deposited, it gets compressed, 

ultimately it becomes a second layer called a firn, f-i-r-n, and then 

ultimately ice and when the snow gets compressed it has ice, so it has 

bubbles of air in there and presumably what is happening is that as they 

drill ice cores down and go further into the past, presumably 160,000 

years of ice, they can look at these microscopic bubbles of air and get the 

greenhouse gas composition associated with that. So that is again a 

statistical estimation process-- 

 MR. WALDEN. Are you comfortable with that process as a 

statistician, not as a-- 

 DR. WEGMAN. Well, presumably that curve that we have seen a 

couple of times from Congressman Inslee should have error bars as well 

associated with it. 

 MR. WALDEN. Should have what? 

 DR. WEGMAN. Error bars associated with it, imprecision, how much 

variability there is. 

 MR. WALDEN. And do we know what that would be? I guess he has 

left. So we are--it is much like the criticism Dr. North had of the Wall 

Street Journal report where it lacked the 95 percent-- 

 DR. NORTH. Yes, we would like to see those error bars. That is 

very-- 

 MR. WALDEN. Yes, we would like to see it as politicians in our polls 

too to know, what plus or minus are we dealing with here. Thank you, 

Mr. Chairman. Thank you, gentlemen. 

 MR. WHITFIELD. Ms. Schakowsky. 

 DR. NORTH. I would like to point out that we now actually can go 

back 650,000 years. Six hundred and fifty thousand years in Antarctica 

in the past year. 

 MR. WALDEN. With precision? 

 DR. NORTH. Just not 150 but 650,000 years, still no CO2 at this 

level. 

 MR. WALDEN. There is still no what? 

 DR. NORTH. No CO2 at this same concentration. 

 MR. WALDEN. I see. Thank you. 

 MS. SCHAKOWSKY. I wanted to explore a little bit the statement that 

Chairman Barton made. He was referring to, I think it was 1975 or 

sometime in the 1970s when apparently there was a prediction of 

cooling, that actually the planet was getting cooler, and here is my 

question, and maybe I am not asking the right one and you could fill me 
120

in on that. But could not--and he used it, I thought, as making the point 

that science is not conclusive. But I am wondering if one could not also 

see it as a confirmation that human activity is in fact causing fairly 

dramatic change in the climate, something that may not have been 

factored in in 1975 but the science based on sort of older predictors. So I 

just wanted to ask how to interpret--and first of all, is that the case that it 

was predicted to be a cooling period? Let me ask Dr. North, the climate 

scientist, first. 

 DR. NORTH. Yes, there was a prediction made in the 1970s by Reed 

Bryson, a professor at Madison. He probably gave us all a hard time 

about this because I have heard this a thousand times in the last year or 

so, few years. So but, there are two competing factors. There is the dust 

in the atmosphere, the tiny aerosols, tiny droplets of water and they come 

from air pollution and volcanoes and other things but mainly air 

pollution in our urban areas, manufacturing processes and so on. So out 

come these tiny droplets. Well, they scatter the sunlight back to space 

and therefore tend to cool the planet a little bit. The other competing 

factor is the greenhouse gases. They have been rising, and especially 

during the war when there was a lot of energy produced and not very 

much regulation on what was allowed to go into the atmosphere. At that 

time there was actually--the aerosols were kind of winning the war, 

winning the war of balancing the heat in the atmosphere, so there was a 

cooling that did occur and probably Reed Bryson was right and that that 

was probably the dominant effect. But it didn’t take very long the way 

we are putting the greenhouse gases in exponentially. The greenhouse 

gas is increasing roughly a percent per year all together, so this is an 

enormous rise in the other competing factor which causes the warming. 

So the thinking is that the warming has now become much greater than 

the cooling due to the aerosols. 

 MS. SCHAKOWSKY. And haven’t we--because of the hole in the 

ozone layer, haven’t we reduced aerosols or-- 

 DR. NORTH. Well, the ozone layer, I would give--that is a 

completely different story, so I would rather we not get off to that. 

 MS. SCHAKOWSKY. Okay. There was another scientific question I 

wanted to ask you and again I am not sure how to phrase it. There was 

something about variability, and isn’t there a conclusion that could be 

made that if there is a great variability, that that might be something that 

we really need to worry about in fact that the effects of carbon dioxide in 

the atmosphere in fact may be worse than we thought if we are-- 

 DR. NORTH. Yes. There are natural fluctuations in the system just 

as weather tickles the whole system and the whole thing rumbles. I 

mean, we have a climate system that sort of rattles around, so this is the 

part that we call natural variability. It is a kind of noise in the system. 
121

But then when we apply these nudges that are continuous, then we get a 

secular trend and the noise on top of it. And by the way, that does tend 

to be a linear process. There have been many, many studies with climate 

models, and while of course they are not perfect, they do imitate the 

atmospheric climate system quite well, and for small nudges like the 

ones we are talking about, I mean, they seem to us to be quite big but in 

fact, in that system, they are tiny. We are changing the temperature a 

degree or two Kelvin compared to 300, so they are tiny. So this is 

actually a fairly linear process. The signals that we see in the system 

from warming and cooling and other things, pretty linear, not that 

nonlinear. So natural variability is there and we worry that we don’t 

understand every bit of it. For example, it could be that there are slow 

processes in the climate system such as the deep oceans, the overturning 

and so on of the deep oceans, and it could be that that is the underlying 

reason for whatever this medieval warm period was. We are not sure 

about that. It could be that some warm water surfaced. What we know 

now though is that that is not the cause of the warming in the last 50 

years. The warming in the last 50 years could not have been because of--

we now have data. We know that is not the reason. In fact, if we look at 

the map of warming, we see that it is warming more over the continents 

than it is over the oceans. They are being pulled along because they are 

not as heavy, they are not as inertial. So the fingerprints of the warming 

are exactly what we would expect if carbon dioxide were the reason. 

 Now, as we go back 1,000 years, we don’t have all that information 

to put in there to check it out so we don’t know exactly why that might 

have happened then but we have a very good idea of what has been going 

on the last 100 years. 

 MS. SCHAKOWSKY. Thank you. 

 MR. WHITFIELD. The gentlelady’s time has expired, and Ms. 

Baldwin, you are recognized. 

 MS. BALDWIN. Thank you, Mr. Chairman. As has been referenced 

earlier in several opening statements and some questions, we know how 

the tobacco industry wanting to keep doubt in the public mind and in fact 

in 1993 the Wall Street Journal published a front-page exposé on how 

the tobacco industry had kept the public doubt alive about whether 

smoking caused cancer. For four decades the big tobacco companies 

funded a sham research organization to feed the public doubt about the 

health effects of smoking, and despite smoking being responsible for 

over 400,000 deaths a year, that strategy worked tremendously well for 

decades. The Wall Street Journal quoted one big tobacco employee who 

said, and I quote, “The scientists can come from Mars but no matter how 

obscure or misbegotten, as long as they are willing to tell the scientific 

lie that it is not proven, the tobacco industry is off the hook.” In May of 
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this year, we learned that some of the same people who worked on 

tobacco also worked to confuse the consensus on global warming. Mark 

Hurtsgard reported in Vanity Fair that for 20 years Dr. Frederick Siete 

directed $45 million in medical research for R.J. Reynolds to maintain a 

hint of doubt about the hazards of smoking. In the 1990s Sietes turned 

his attention to global warming. Dr. Sietes assaulted the integrity of the 

Intergovernmental Panel on Climate Change on the op-ed page of the 

Wall Street Journal. He accused the Clinton Administration of 

misrepresenting the science and authored a paper which said that global 

warming was an exaggerated threat. 

 These people have a plan. They want this hearing to stand for the 

proposition that there is not a consensus on global warming and they 

have stalled action for a decade or two and they think they can drag it out 

even longer. So Dr. North, I am wondering if you can help put this in 

context. Dr. Mann had concluded that the late 20th Century warmth in 

the Northern Hemisphere was unprecedented during the last 1,000 years. 

You said very clearly in your testimony that Dr. Mann’s conclusion has 

been subsequently supported by an array of evidence. We have a high 

level of confidence that late 20th Century is the warmest period the planet 

has seen in the last 400 years and you found it was plausible that the 

planet is warmer than it has been in 1,000 years. Is that a fair summary? 

 DR. NORTH. Yes. 

 MS. BALDWIN. You said it was plausible that the planet is warmer 

now than it has been any time in the last 1,000 years. Has anyone 

provided affirmative evidence that there has been a warmer period in the 

last 1,000 years? 

 DR. NORTH. No, we have not. That is what we mean by plausible, 

that there just doesn’t seem to be any counter information, so it is a 

reasonable thing to-- 

 MS. BALDWIN. Is it plausible that human beings have caused 

greenhouse gas emissions that are contributing--I am sorry. Let me put it 

in the negative. Is it plausible that human-caused greenhouse gas 

emissions are not contributing to global warming? 

 DR. NORTH. It is not plausible. 

 MS. BALDWIN. How confident is the scientific community that 

human emissions are contributing to global warming? Seventy-five 

percent, 80 percent? 

 DR. NORTH. In the scientific--in the climate science community, I 

think that Mr. Inslee’s quote about the number of papers and who says 

yes and who says no tells the story. 

 MS. BALDWIN. Okay. 

 DR. NORTH. It is hard to find anyone who works in this field who is 

opposed. I mean, if somebody can come up with a really good physical 
123

explanation for why this is false, they will win the Nobel Prize. So there 

are a lot of people who might be attracted to the idea but we can’t find 

any. 

 MS. BALDWIN. Well, finally, I just want to ask you about the IPCC 

report since we have been hearing a lot about it. Does the NRC report in 

any way discredit the IPCC’s 2001 third assessment report? 

 DR. NORTH. Well, we have some differences with the details of the 

hockey stick curve and we said that. We are a little less confident. I 

mean, our error bars as we have been saying, our margin of error is a 

little larger than what was stated in that report and that is natural. As we 

go on and learn more, we adjust and adapt. So, no, we don’t believe 

individual years--Dr. Wegman said this, and we agree. We don’t trust 

individual years, the 1998 or 2006 or something as being the warmest of 

any time period because we can’t state things to that degree. 

 MS. BALDWIN. Just to clarify, my question was, did your report in 

any way discredit the IPCC’s 2001 third assessment report? Would you 

view-- 

 DR. NORTH. No, we wouldn’t-- 

 MS. BALDWIN. --what you are describing as discrediting that report? 

 DR. NORTH. No, it doesn’t discredit it. 

 MS. BALDWIN. Okay. Thank you. 

 MR. WHITFIELD. Thank you, and after almost 5 hours, that 

concludes the first panel, so we should be through with the second panel 

in about 10 hours. Dr. Wegman, I want to thank you very much and Dr. 

North for your testimony and obviously this is a subject matter of great 

interest and importance and we thank you for your testimony, and now I 

look forward to the second panel and so I will release you all. And on 

the second panel we have another distinguished group of individuals. 

Mr. Thomas Karl is director of the National Climatic Data Center from 

Asheville, North Carolina. Dr. Thomas Crowley is the Nicholas 

Professor of Earth System Science at Duke University. Mr. Stephen 

McIntyre of Playter Boulevard in Toronto Canada, and then Dr. Hans 

von Storch, who is the director of the Institute for Coastal Research who 

flew to this meeting from Germany exclusively for this meeting, and Dr. 

Storch, how do I pronounce the name of your town in Germany where 

you are from? On here it says G-e-e-s-t-h-a-c-h-t. 

 DR. VON STORCH. Geesthacht. 

 MR. WHITFIELD. Geesthacht. Okay. Anyway, we welcome all of 

you, and as you know, this is an Oversight and Investigations hearing 

and it is our customary manner to take this testimony under oath and I 

would ask you, do any of you have objection to testifying under oath? 

And I am assuming you do not need legal counsel. So if you would 

please raise your right hand. 
124

 [Witnesses sworn.] 

 MR. WHITFIELD. Thank you very much. You all are now under 

oath, and Mr. Karl, we will start with you and we will recognize you for 

your 5-minute opening statement. 

STATEMENTS OF DR. THOMAS R. KARL, DIRECTOR, 

NATIONAL CLIMATIC DATA CENTER; DR. THOMAS J. 

CROWLEY, NICHOLAS PROFESSOR OF EARTH SYSTEM 

SCIENCE; DR. HANS VON STORCH, DIRECTOR OF 

INSTITUTE FOR COASTAL RESEARCH; AND MR. 

STEPHEN MCINTYRE, TORONTO, ONTARIO 

 DR. KARL. Mr. Chairman, members of the committee, I am pleased 

to have the opportunity to testify before you today. I am the Director of 

NOAA’s National Climatic Data Center. The National Climatic Data 

Center houses the World Data Center for Paleoclimatology, which 

includes the data sets that have been used to reconstruct temperatures for 

the past 1,000 years or more. 

 I was one of the two coordinating lead authors for chapter 2 of the 

Intergovernmental Panel on Climate Change, the IPCC 2001 assessment. 

The primary intent of the IPCC periodic assessments is to provide 

government policymakers with the latest and most comprehensive 

scientific information possible about the human influences on our global 

climate in a language that has meaning and relevance to government 

policymakers. Our responsibility as coordinating lead author was to act 

as co-chair during the lead author chapter meetings. Each chapter has 

multiple lead authors and chapter 2 had 10 lead authors. Chapter 2 was 

to assess the data for changes and variations in climate. Coordinating 

lead authors are ultimately responsible for ensuring that the final version 

of the chapter is delivered to the IPCC bureau on schedule. Each chapter 

is agreed to by all lead authors and discussed and reviewed with other 

chapter lead authors. There is a very lengthy review process which 

includes review editors to oversee the review process. In 2001 the IPCC 

report concluded, and I quote, “New analyses indicate that the magnitude 

of the warming over the 20th Century is likely to have been the largest of 

any century in the last 1,000 years,” and I emphasize warming here, the 

magnitude of the warming. Those are my words. “The 1990s are likely 

to have been the warmest decade of the millennium in the Northern 

Hemisphere and 1998 is likely to have been the warmest year.” These 

findings were developed after careful consideration of the published 

literature on this topic in 2001. 

 The IPCC lead authors considered uncertainties related to two types 

of temperature reconstruction errors. Such errors can be thought of as 
125

having two fundamentally different sources. I will use some technical 

terms. Parametric and structural, but I will define these. Parametric 

uncertainty, which results from finite sample sizes to estimate 

coefficients of a statistical model, is much less important than structural 

uncertainty. Human decisions that underlie the development of the 

reconstructed time series may be thought of as forming a structure 

depicting both real and artificial behavior in paleoclimatic data. 

Assumptions that guide the decisions made by the experts may not be 

correct. More important factors may have been ignored. These 

possibilities lead to structural uncertainty. Structural uncertainty can 

only be estimated by comparing the differences of equally plausible 

reconstruction methods. The IPCC 2001 lead authors were able to 

estimate structural uncertainty associated with the IPCC findings because 

of the availability of several reconstructed time series. 

 It is important to note the language used by IPCC in the 2001 

assessment included an expert assessment of the certainty of various 

findings. The IPCC reported findings when the probability of being true 

reflected certainty between 66 and 90 percent, or in odds terms, better 

than two to one. Lead authors were asked to develop findings based on 

at least three levels of certainty, likely, better than two to one odds of 

being correct, very likely, better than nine to one odds, and virtually 

certain, better than 99 to one. These odds of probability were based on 

the lead author’s assessment of the published literature and in 

consideration of thousands of expert review comments. I note that such 

expert assessments in related fields such as the probability of 

precipitation forecasting have proven to be quite reliable. 

 Several research teams have challenged the reconstructed 

temperatures featured in IPCC. These challenges are not without 

validity. But now each of the challenges have been assessed in a variety 

of new analyses. For the past several years there have been at least half a 

dozen new analyses using many of the same paleoclimatic data featured 

in IPCC 2001 as well as new data covering longer time periods or 

slightly expanded geographic coverage. Of all these analyses, none show 

temperatures during the past 1,000 years higher than the last few decades 

of the 20th Century and into the 21st Century. These analyses used 

different statistical methods, various types of paleoclimatic data and 

different temperature calibration approaches. 

 In June, the National Research Council reassessed the 1,000-year 

reconstructed time series. The NRC not only assessed the paleoclimatic 

data but considered how well the data stands up to our ability to simulate 

the temperature record of the past 1,000 years. The NRC found that for 

the most part, climate model simulations are consistent with 

reconstructed paleoclimatic data of the Northern Hemisphere. The NRC 
126

report indicates it is plausible, as we heard, that the last few decades of 

the 20th Century were warmer than any other time during the past 1,000 

years. I note the NRC does not define the odds of probability associated 

with the term “plausible.” In contrast to IPCC 2001, the recent NRC 

report did not highlight the rate of temperature increase during the 20th

Century compared to the previous 10 centuries. I note the rate of 

temperature increase is also relevant to our ability to adapt to changes in 

both our society as well as the planet’s ecosystems. 

 In order to improve our estimates of reconstructed temperature, more 

proxy records await our extraction. Setting out to extract and calibrate 

proxy paleoclimatic data is necessary but not sufficient to reduce further 

uncertainty. The data from proxies must also be accessible by the 

broader science community for analysis. At the present time there is no 

formal process whereby federally funded scientists must submit their 

data to a long-term data archive facility for use by the general 

community. 

 In conclusion, considering the additional evidence since the IPCC 

2001 assessment, I would extend the IPCC 2001 statement about the 

Northern Hemisphere temperatures in the 1990s being higher than any 

other decade during the past 1,000 years with probability of better than 

two to one to include the most recent two decades. 

 Thank you, Mr. Chairman and committee members, for allowing me 

the opportunity to discuss and inform the committee. 

 [The prepared statement of Dr. Thomas R. Karl follows:] 
127

PREPARED STATEMENT OF DR. THOMAS R. KARL, DIRECTOR, NATIONAL CLIMATIC DATA 

CENTER, NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION, U.S. DEPARTMENT OF 

COMMERCE
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 MR. WHITFIELD. Thank you, Mr. Karl, and Dr. Crowley, you are 

recognized for your 5-minute opening statement. 
135

DR. CROWLEY. Thank you very much for the opportunity to present 

my testimony. I will briefly state my credentials and give a short history 

of the Mann et al. paper with respect to the Intergovernmental Panel for 

Climate Change report. 

 As background, I received a Ph.D. in marine geology from Brown 

University and I specialized in study of the Earth’s past climates. Over 

the last few years I have spent part of my time working on climate 

change over the last 1,000 to 2,000 years. You have gone over some 

aspects of the Mann et al. paper ad nauseum so I am going to skip over 

some elements of what I am going to say and then discuss aspects of how 

I perceived the Mann et al. report was included in the IPCC, okay. I was 

not part of IPCC but I am familiar enough with some of the science that 

was going on that I thought it might be useful. But it is my perception of 

it, okay. 

 So with respect to the inclusion of the Mann et al. report, especially 

into the summary for policymakers, at that time there were three 

reconstructions that went back 1,000 years, okay, at the time of the IPCC 

3, so back to the Middle Ages. Now, one of the reconstructions--Mann 

et al. was the second to come along. One of the reconstructions uses 

completely different methodology from Mann et al., and if I could have 

the second figure there, okay, and I can’t read that very well. Really 

focus on, if you can even read, the right axis, okay. That is temperature 

variations. Forget the left axis there, and that is time over the last 1,000 

years, and the Mann et al. reconstruction is in green. That is decadally 

smooth Mann et al., reconstruction, okay. And this other reconstruction 

which I was involved in really stemmed from a discussion I had at a 

meeting where people say well, I don’t believe Mann, and there was 

nothing written about it. They just say they don’t believe Mann. And so 

out of this grew, I said okay, I got so exasperated. We just--I will go 

analyze some data myself and just see what it looks like, and we 

deliberately took a very different approach rather than using what they 

call the sealed method for reconstructing a temperature. We took this 

other methodology which has the scientific term “bonehead” associated 

with it in which we just added up all the individual curves and took the 

average, okay. And the reason we do that in part is so we can see exactly 

in the terms of the curve here, you can understand exactly how your 

composite curve originates from the nature of the raw data, okay, and 

that is real easy. If there is a bump, you can go back to the raw data and 

see where it came from, okay. And the other reason for doing that is 

geological data is by definition dirty data and sometimes it is very 

helpful sometimes to be somewhat conservative in the statistical 

methodologies you employ. So what we did is, the bonehead approach 

using some of the data from Mann et al. but other records also, some of 
136

which have been cited as indicative of a medieval warm period, and even 

though some of these records locally clearly show temperatures locally 

warmer than 20th Century during the Middle Ages, when we summed up 

all the different records, we got a pattern that was surprisingly similar to 

what Mann had gotten as you can see from the red curve there. Yes, 

there are some differences there but the similarities look a lot more--you 

know, a lot--there are more similarities than there are differences there. 

We stopped our analysis in 1960, okay, so that is why we don’t get this 

big tail at the end. But over most of it is pretty similar. So this was in 

some way was a very--it was a surprise. I had no idea what it would look 

like, but it suggested that the Mann et al. result might be robust in terms 

of its pattern about the relative magnitude of warmth in the Middle Ages 

and what was happening there, when you go back to the raw data which 

you can easily do with this type of reconstruction, the reason we didn’t 

get a very warm medieval warm period was that whereas some places 

were warm, others were cold at the same time so when you averaged 

them, it came out to some value in between. So we understood then why 

that happened, why we were getting that result. 

 Now, there is a follow-up to that. Our reconstruction, we weren’t 

trying to say it was better than Mann or anything. We were just trying to 

do what is called a sensitivity test on the Mann et al. result, okay. Now, 

the Mann et al. result was the only paper that actually estimated the 

sensitivities, the uncertainties of your conclusion which Dr. North has 

emphasized is very important, and for that reason, I believe it was 

legitimate to include that, to select that as the paper that would go in to 

highlight the millennial perspective for IPCC because it was the one that 

had the objectively determined uncertainties in the reconstruction, okay. 

So that is how it wound up in IPCC and they had some additional 

information that it might be okay. 

 Now, science progresses and sometimes past conclusions have to be 

modified. A notable example with respect to IPCC involves this 

significance of satellite upper air data that previously had not agreed with 

model predictions. Now they seem to, okay. That is just the way science 

goes. Similarly, some papers have been published since the IPCC 

suggesting greater variability than Mann et al., and contrary to claims of 

the Wegman report, and again, I should point out here, I apologize for 

the sometimes poor use of terms that I have used to describe Dr. 

Wegman and I apologize to Dr. Wegman for that. But contrary to the 

claims in that report, one of these reconstructions used a completely 

independent data set for verification. 

 Can we have the next figure, please? And I was hoping to have a 

pointer, but the main point here is what you see here is--I just want to 

spend a little bit of time on this because you are seeing basically the 
137

same net conclusion as you see from Mann et al. even though we had 

greater variability that Mann et al. in this reconstruction, and again, this 

is sort of a slightly sophisticated update of the bonehead methodology, 

okay. So it is bonehead squared or something. But what you see here is 

we have reconstructions here in blue and red and yellow, different length 

of time series, but it goes back to about 500 A.D., and we have 

uncertainties assigned to these reconstructions based on the uncertainty 

in the overlap interval with the instrumental record here. But the 

difference we get is that we have a completely independent validation 

based on the methodology data from borehole measurements of heat flow 

in the Earth’s interior, okay. That is completely independent from the 

data we use. And statistically, we actually have two borehole scientists 

on our team for that paper plus two sets of statistical climatologists, I 

might add, that the relationship between this low resolution borehole 

record and this higher resolution surface reconstruction are 

indistinguishable and yet the variations you see here are much greater 

than what you see in Mann et al., okay, the variability. We have a 

slightly warmer medieval warm period than Mann et al. but even there if 

you take decadal smoothing there, that peak value here in the medieval 

warm period really at best approximates what happens in the mid-20th

Century, all right? And again, because of the nature of the way we 

combine the data, we understand exactly why it doesn’t get really warm, 

okay. And so this is a paper that is coming out--well, it has actually been 

accepted by the Journal of Climate and will be out sometime later this 

year. So this is one of the things we don’t agree with Mann in terms of 

variability. Others, Mann has updated his reconstruction and he still 

believes that it is the same. So there are still differences in the field but a 

number of other studies show higher variability at that time. 

 The interesting point about the higher variability and you have to be 

really aware of this is that it is not--some people may--it almost seems 

sometimes in reading papers that people enjoy disproving Mann, okay, 

but one of the things you have to be aware of, you have a reconstruction 

that has higher variability and greater warming in the Middle Ages. 

What it means is, your climate system has higher sensitivity, okay, than 

the Mann et al. reconstruction which has only small wiggles, okay, and 

high climate sensitivity carries over to what the implications are for 

carbon dioxide forcing because the only--sensitivity means that if you 

have a certain amount of forcing, you either get a small response or a big 

response, okay. You have a system with low sensitivity, then it doesn’t 

wiggle much. If that was true for carbon dioxide, you wouldn’t have to 

worry about it. You just close the door and throw away the key and keep 

burning oil until you want. If it has a high sensitivity though, you have 
138

to start worrying, and the implication of this result is that climate 

sensitivity is much higher than before, okay. 

 So now, I may be almost out of time here, okay, because I have spent 

a lot of time on this. I have a few comments-- 

 MR. WHITFIELD. Dr. Crowley, you are about 4 minutes over your 

time, but if you want to summarize, then there will be plenty of questions 

for you as well. 

 DR. CROWLEY. Okay. I just wanted to highlight a couple points on 

the Wegman report. I am not going to talk about their assessment of the 

Mann et al. thing. That is really--I disagree with them with respect to 

their recommendations and I will just summarize these disagreements, 

one being that the interactions with the statistics community have really 

increased very significantly and I think that Dr. Wegman and his 

colleagues may have been working with--had a small sample problem 

just looking at some of the paleoclimate papers because in fact it is a 

rather substantial improvement in the interactions between real 

statisticians and the climate--and percolating down into the paleoclimate 

community, and that is true even for the IPCC. The key chapter in the 

new IPCC report actually has a statistician and a statistical climatologist 

as co-lead authors of this chapter, okay. So they are being well 

integrated into the process. 

 And finally, with respect to authors should not assess their own 

work, this sounds fine in theory but in practice it seems almost 

unworkable because who else but experts can produce an expert report. 

And with respect to the IPCC, I think it is a marvelous document. It 

involves hundreds of scientists, reviews of thousands of papers, and 

received on the order of 10,000 comments for each of the earlier drafts. 

 MR. WHITFIELD. Are you about ready to conclude, Dr. Crowley? 

 DR. CROWLEY. So my feeling is that it is a very, very thoroughly 

reviewed and vetted manuscript and I think it is just about the best thing 

we have. 

 [The prepared statement of Dr. Thomas J. Crowley follows:] 

PREPARED STATEMENT OF DR. THOMAS J. CROWLEY, NICHOLAS PROFESSOR OF EARTH 

SCIENCE SYSTEM, DUKE UNIVERSITY

I thank the committee for the opportunity to submit my response to the findings of 

the NRC and Wegman Reports. As background to my testimony, I will briefly state my 

credentials. I received a Ph.D. in marine geology from Brown University and have a long 

interest in the history of the Earth’s past climates, both from a modeling and 

observational viewpoint. I have published about 100 peer-reviewed papers and have coauthored a book on the subject. I have worked in academia, the private sector, and at two 

government agencies – at NSF as a program director in climate and at NASA/Goddard 

Space Flight Center as a National Research Council senior fellow. I am presently the 

Nicholas Professor of Earth Systems Science in the Nicholas School of the Environment 

at Duke University. 
139

Because this hearing has been called to better understand the influence of the muchdiscussed 1998 and 1999 papers by Michael Mann, Raymond Bradley, and Malcolm 

Hughes, I think it would be useful to provide a brief scientific background to the subject. 

Prior to 1998 there had been only one attempt to summarize the various types of data 

from past climate to get a broader picture as to how it has changed over the last few 

centuries. In 1998 Mann et al. introduced a new technique to develop more quantitative 

estimates of the nature of climate change since AD 1400 for the northern hemisphere, and 

in 1999 the group extended that record back to AD 1000 and concluded that the late 20th

century warming was the largest in the last 1000 years. This report was among a number 

of scientific studies highlighted in the IPCC Third Assessment Report (TAR) to conclude 

that “there is new and stronger evidence that most of the observed warming over the last 

fifty years is attributable to human activities”. 

With respect to the committee’s interests in whether the objectivity of the IPCC with 

respect to the Mann et al. studies I elaborate on several points below. At the time of 

IPCC TAR it represented the best estimate of past millennial temperatures and their 

uncertainties, and that the most important conclusion from IPCC (stated above) does not 

depend on the Mann et al. papers for its credibility, and are even more robust today than 

they were in 2001. 

The final part of my presentation involves a number of objections, both major and 

minor, to the Wegman Report. 

I have five main points to make concerning the following subjects: 

(1) The relation between the Mann et al paper and the IPCC Third Report in 

2001. The Mann et al paper was certainly influential in the IPCC Third 

Assessment Report (TAR), but so were many other papers. But the papers 

that made the biggest difference were the ones focusing on the instrumental 

record in which it was shown that models and data could not be reconciled 

unless an anthropogenic greenhouse influence was invoked. The most 

compelling driver of all was the fact that global temperatures kept going up 

and up since the 1996 report, and meltback of glaciers increased in many 

parts of the world. I might add that this trend has only accelerated since 

2001, with melting in the Arctic and on Greenland reaching alarming levels. 

(2) The Mann et al paper in and of itself. At the time of IPCC TAR there were 

two other reconstructions going back to the Middle Ages, with decadally 

smoothed data showing, at best, past millennial temperatures comparable to 

the mid-20th century warm interval. One reconstruction (Crowley and 

Lowery, attached) using a completely different methodology agreed with 

Mann et al. quite well (Fig. 2). However, Mann et al. was the only paper of 

the three that estimated uncertainties, and it is no surprise that this paper was 

the one chosen to highlight the millennial perspective for IPCC. The 

significant criticisms of the Mann et al. paper that have been published since 

2001 are by definition after the fact with respect to IPCC TAR. 

(3) The present state of our knowledge on millennial changes Science always 

progresses and sometimes past conclusons have to be modified. A notable 

example with respect to IPCC involves the significant reassessment of 

satellite upper air data that previously had not agreed with model predictions 

of increasing air temperatures in that region; new assessments indicated that 

the models and data were now in approximate agreement. Similarly, some 

papers have been published in the last five years suggesting greater 

variability than Mann et al. Contrary to the claims of the Wegman Report, 

one of these reconstructions (Hegerl et al., attachment 2) uses a completely 

independent data set from borehole measurements (fig. 3) of the effects of air 

temperature change on heat flow in the upper part of the Earth’s crust. 
140

 Because Mann et al. have more recently obtained results similar to their 

earlier work, but now using a different methodology, it continues to be 

necessary to understand the causes of differences among the different 

reconstructions before the estimates of higher temperature variability can be 

accepted. Even if the latter estimates ultimately prove to be more accurate, 

there is no room for gloating (as sometimes seems evident in discussion of 

the newer results), for the higher variability inevitably implies a higher 

climate sensitivity, which is a cause of much more serious concern for either 

the committee, or society at large. By this I mean that for any given level of 

climate forcing from carbon dioxide, the expected temperature response 

would be larger than it would if the Mann et al. reconstruction was ultimately 

deemed to be the “final word” on the magnitude of past climate change (see 

Hegerl et al., third attachment). 

(4) The claim of unusual level of warmth for the late 20th century is still valid for 

all but one of the new reconstructions. Contrary to the conclusions of the the 

Wegman report, there is reason to believe in the unique nature of late 20th

century warmth (this is the only major point in which I differ from the NRC 

report). Although the early millennium records are small in number, the 

composite reconstruction agrees in the overlap interval (A.D. 1500-1960) 

with reconstructions using more extensive data sets. Furthermore, 

examination of the raw data indicates that even in the high latitude northern 

hemisphere they show regional variations in the timing of warmth that is 

much greater than in the late 20th century. In other words, some regions are 

warm and some cold – a very different pattern from the late 20th century, 

where almost every region has warmed over the last 100 years. It is 

therefore no surprise that, when these records are composited, the sum value 

is smaller than for the late 20th century. 

(5) The conclusions and recommendations of the Wegman Report have some 

serious flaws. In addition to a number of technical errors, large and small, 

the following comments can be made in the bullets on page two of the 

committee’s summary of findings (fact sheet): 

(a) bullet one (concerning specifics of Mann et al.) – responses discussed 

above 

(b) bullet two – “many of the proxies are reused in most of the papers....it 

is not surprising that would obtain similar results...” This almost 

sounds as if it is wrong for everyone to use the best existing data! 

The more important point, and one not stated, is that different 

methodologies are employed by each of the investigators. 

Furthermore, there is nothing wrong with talking to or even 

collaborating with someone else in a field that you respect, and has 

expertise that you don’t have. The Wegman Report almost seems to 

imply that collaboration is equivalent to collusion, a result that would 

apply to the Wegman Report itself if that were always true. 

The inference in the same bullet concerning the failure of the peer 

review statement is an oversimplification. The anonymity of peer 

review still allows papers to be rejected, as almost any scientist can 

testify. As a former NSF program director, I have had significant 

opportunity to evaluate the peer-review system. It is not perfect but in 

general the best work gets funded. For publications, editors usually 

select a variety of reviewers who cover the different expertises in the 

study. But it is just not practical to expand the number of peer 

reviews for many publications – the work load is just too onerous for 

the reviewing pool, and most people will simply decline the request to 
141

review the papers. Finally, I would like to comment that the Wegman 

Report now before the committee has not undergone any extensive 

peer review from anyone in the climate community prior to its 

submission to the committee for inclusion into the record and, most 

problematically, possible use as a guide to further recommendations 

by the committee. 

(c) Bullet three – the researchers do not seem to be interacting with the 

statistical community. This statement is based on a small subsample 

of paleoclimate papers. Overall, there is increasingly strong 

incorporation of statistical methodologies in the climate sciences, 

including increased interactions with statisticians. For example, the 

National Center for Atmospheric Research has had a postdoctoral 

program for statisticians for thirteen years. A key project jointly 

funded by DOE and NOAA for detection and attribution of climate 

change involves not only several statistical climatologists but also 

explicitly seeks out input from statisticians. The present (and key) 

IPCC Fourth assessment chapter on detection and attribution of 

climate change has a statistician and statistical climatologist (with a 

training in applied mathematics) as co-lead authors. Statisticians are 

welcome to respond to any of the chapters in the review process. 

From these statements it is clear that the Wegman Report is 

somewhat uninformed with respect to the effort to include statisticians 

in the IPCC review process. 

I might add that interactions between geoscientists and statisticians 

have long been hampered by what can only be described by some as a 

condescending attitude from some statisticians that geoscientists were 

not employing the most recent, state of the art statistical methods. 

Such attitudes almost guarantee subsequent poor communication and 

fail to recognize the unusual nature of “field laboratory” geoscience 

data, which are very different than “closed laboratories” where the 

conditions of an experiment are well controlled. The latter types of 

data require an intimate understanding of the raw data and simpler, 

more robust statistical methodologies that recognize the limitations of 

such data. 

(d) Bullet four – authors of policy assessment should not assess their own 

work. This statement may sound fine but in practice but seems almost 

totally workable. Who else but experts should produce an expert 

report? The third and fourth IPCC reports involved hundreds of 

scientists around the world, a review of thousands of papers, and 

received on the order of 10,000 comments in the early stages of drafts. 

The final summary for policymakers requires a vote – by government 

representatives of the signatory nations -- on every single sentence 

before it is accepted! I can attest from personal experience that the 

resultant high quality of the IPCC documents make them ideal choices 

for teaching graduate and professional courses because they are by 

definition our best statement on the present state of knowledge of the 

climate system. It is inconceivable to me that a report of this quality 

could be produced by a group of nonspecialists. 

(e) Bullet five – paleoclimate data does not provide insight into physical 

processes The statement on physical processes is completely wrong. 

In fact, paleoclimate modeling results indicate that about half of the 

decadally scaled variance between 1270 and 1850 can be explained by 

natural variations in solar and (primarily) volcanic forcing. When 
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these forcings are carried over into the 20th century, they cannot 

explain the 20th temperature rise. Only greenhouse gases can explain 

the rise, not only for the late 20th century, but also in part for the mid20th century. 

In this same bullet the Wegman Report recommends that federal 

research should emphasize fundamental understanding of the 

mechanisms of climate change and should focus on interdisciplinary 

teams to avoid narrowly focused discipline research. I find this to be 

an extremely naïve statement. Climate studies are among the most 

interdisciplinary field that one can imagine – as just one example I 

submit a copy of a paper (attachment four) on causes of climate 

change over the last millennium that discusses changes in solar 

output, volcanism, trace gas variations in climate, tree rings, ice cores, 

climate models, impact of vegetation, etc etc. There are many other 

examples of interdisciplinary activities. 

As a former program director at the National Science Foundation, I 

think I can also speak for many present program managers in federal 

agencies concerning the lack of interdisciplinary activities on different 

projects. This interdisciplinary is the core concept of terms such as 

“Global Change” and “Earth Systems Science” and as such the 

agencies have made a great effort at supporting interdisciplinary 

research. Furthermore, every major modeling group in IPCC 

addresses a host of interdisciplinary science. 

But it would be a big mistake to forget the lone investigator. 

Sometimes the most fundamental findings in a field come from these 

lone investigators (who may nevertheless have much contact with 

many others). There must be room for individual creative science in 

climate science. 

Summary and Concluding Remarks In my view the debate over the Mann et al 

paper is a tempest in a teapot. It is legitimate material for scientific discussion but the 

implications with respect to the operations of the IPCC are unproven and seemingly 

based, in my opinion, much more on repetition of innuendo than on any real facts. 

Although there is always a need for enhanced interaction with the statistics community, 

the lack of communication is seriously misrepresented in the Wegman Reprot. I believe 

that this report should not be used as either a legitimate assessment of the science or as a 

guide to policy modification. Finally, I believe it is time to stop using Michael Mann as a 

whipping post and to start directing attention to the more important matters of whether 

anything should be done about global warming, and if so, what? 

Attachments: 

1. Crowley, T.J., and Lowery, T.S., 2000. How warm was the Medieval Warm 

Period? Ambio (publication of the Royal Swedish Academy of Sciences), v. 

29, no. 1, pp 51-54. 

2. Hegerl, G.C., Crowley, T.J., Allen, M., Hyde, W.T., Pollack, H.N., Smerdon, 

J., and Zorita, E., 2006. Detection of human influence on a new, validated, 

1500 year temperature reconstruction, Journal of Climate (accepted). 

3. Hegerl, G.C., Crowley, T.J., Hyde, W.T., and Frame, D.J., 2006. Climate 

sensitivity constrained by temperature reconstructions of the past seven 

centuries. Nature, v. 440, 1029-1032. 

4. Crowley, T.J., Causes of climate change over the last 1000 years. Science, v. 

289, 270-277. 
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Photo Courtesy of John Garver and Donald Rodbell

On the Need for Perspective

Regarding the Mann et al Reconstruction

Thomas Crowley

Nicholas School of the Environm ent

Duke University

Photo: Glacier Meltback in the High Andes since the Little Ice Age

(1) Mann et al and IPCC

Magnitude of influence over-rated
209

Courtesy G. H egerl

(2) Mann et al in and of itself

The best estimate we had at the time
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0.0

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Mann et al. vs Crowley-Lowery (2000)

Crowley-Lowery (scaled)

Mann et al sm 11

Crowley-Lowery Scaling (0 to 1)

Temperature Variations (°C)

Year

Hegerl, Crowley et 

al. submitted

N. Hemisphere land temperatures (30-90N)
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-1.0

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Evidence for Overwhelming 

Anthropogenic Greenhouse Gas 

Influence on 20th Century Temperatures

Instrument - 30-90N (smoothed)

Paleo-reconstruction (smoothed)

volcanism + solar only (smoothed)

Model - all forcings

Temperature Variations (C)

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no Greenhouse Gas Forcing
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Individual Records of Long Composite (956-1960)

w.U.S.

Alberta, Canada

w.Greenland

n.Norway

w.Siberia

c.Siberia

Mongolia

e.Asia

Standard Deviation Units

Year

 MR. WHITFIELD. Thank you. Dr. von Storch, you are recognized for 

5 minutes. 

DR. VON STORCH. Thank you very much for inviting me here. I just 

wanted to mention that I am joined here by my colleague, Eduardo 

Zorito, from the same laboratory sitting there in the back. 

 Next transparency, please. So I am just summarizing my paper here. 

So first scientific aspects. So the progression-type methods of the socalled hockey stick studies of Mann, Bradley, and Hughes suffer from a 

number of problems which should have been addressed before the 

hockey stick was elevated to an authoritative description of the 

temperature history of the past 1,000 years. It says 1,000 to 2,000 years 

but that is an error. 

 Second, the claim by the IPCC third assessment report, that is the 

2001, that there is reliable evidence that climate is beginning to change 

due to human action was based on a number of different lines of 

argument which are insensitive to the validity of the MBH studies, that 

is, the present debate about the validity of the hockey stick is of marginal 

relevance for the detection of present anthropogenic climate change. I 

claim the major problems are not of a statistical nature but are related to 

the social practice of climate change studies. 

 Next transparency, please. In the Wegman report, let me say a few 

words about the Wegman report. We have in our working group 

examined how serious the error of biased centering would be on the 
213

overall results given a temperature history reminiscent of the IPCC 1990 

version. The paper has been published and the effect is very minor. It 

does not mean that it is not a glitch but it really doesn’t matter here, at 

least to the extent we could test it. 

 There are other aspects which are much more relevant I would have 

hoped that Dr. Wegman would have taken this up, that is, the usage of 

the trend as a key element for training the progression model. It is a bit 

funny to use the trend to train something and I will show you in a second 

what that means. 

 And second, the method of something, what is called scaling, that is, 

that you artificially make sure that the variance of the predictor, that is, 

the temperature, equals the variance of the predicted temperature, the 

derived temperature. So you multiply it by a number so that it just 

comes out as if you could explain the total variance by the proxy. You 

cannot. You know that you cannot do it and therefore you introduce an 

error which you cannot avoid. 

 Third, we welcome the suggestion by Wegman and his colleagues to 

invest much more effort to examine the error structure in deriving 

temperature data from proxies. 

 There are two main issues. First is the homogeneity of proxies. If in 

the year 1960 the tree ring means something for temperature--no, I mean-

-yes, it does not mean that this is the same information in the year 1200. 

It could be that the process to get out the information from a 1200 tree 

ring is different from the 1960. Second, the instationarities of the late 

proxy and temperature. We know that there are some problems at least 

that has been explained at the Academy hearing that nowadays the link 

between temperature and CO2 seems to be damaged. When Hughes was 

asked what the reason could be, he gave three different hypotheses, and 

when he was asked, do you think it could have happened in the past, the 

answer was yes. So it could be that the link which we see now these 

days in the past 100 years or so would be different than previous times. 

We cannot know that and we have to think about how to model this 

effect. 

 The next transparency, please. That shows the danger of relying on 

trends. So you see here, a times series throughout the instrumental 

period, that is, the period when we think we have enough data to derive 

Northern Hemisphere mean annual temperature from instrumental data, 

and you see in yellow, that is the area when the method has been trained 

and then we see it has been trained from 1910--well, it has been trained 

for a longer time showing a 21-year running means. And the red curve is 

what the MBH method was indicating the temperature variation should 

have been in this period and the black is a new analysis of the climate 

research unit. It was produced after that was done, and now what you 
214

see here is that the green and the black curve are very nicely coincident 

during the trend but nothing else. Nothing else is reproduced and so it is 

just what this method is fixing up is the trend and nothing else, or it may 

be so. One should check that out. And so this is a bit dubious. 

 Next transparency, please. Understand that you are concerned about 

the quality control process of climate change science, and I would claim 

that parts of climate change science, in particular paleoclimatic 

reconstructions have suffered from gatekeeping and insistence usage of 

reviewers. I myself can say that they were always the same type of 

reviews we got, the same style and I am sure that it was the same person 

and I am sure it was the person we have spoken about here quite a bit. 

 And I also claim that editors in science magazines have failed to 

ensure the reproducibility of key results. The methods have not been 

described properly and their data one could not access. Part of the mess 

here is due to the practice of Nature and Science that they have a bias 

towards interesting results. I mean, they have--their way of operating is 

not only that the results are innovative and valid but they must also be 

interesting. Then what I think is really not good that in the IPCC process 

experts assess their own work. 

 That is, to conclude this, climate change science has suffered from 

limiting action of gatekeepers and the public preference for interesting 

results. Climate change science should provide stakeholders with a 

broad range of options and not narrow this range to reduce numbers of 

options preferred for certain world use. 

 I was a bit disappointed about the comment from the lady from 

Illinois who said aren’t you afraid if you say this that this would have 

negative implications for the policy process. I mean, is that really--I 

mean, I was kind of shocked. I mean, should we really adopt what we 

say if that is useful for the policy process? Is that what you expect from 

science? If we give advice, that we first think is it useful for something. 

I think that is not the way we should operate, or if we do that, you should 

not listen to us. 

 Next transparency. This is not to please the people on the right-hand 

side. The acceptance of the IPCC in the community, this is actually--it is 

very well accepted and it is very hard to see this but it is the result of a 

survey which was asking to what extent do you agree or disagree that the 

IPCC report is of great use of the advancement of science. That is on the 

left-hand side. And then you see a statistical description of the 

responses. At the bottom they would say strongly agree. At the top they 

would say strongly disagree. And then there are--on the left-hand side 

there are results from 1996 and on the right-hand side 2003, one block 

for U.S., the other for E.U., and you see in 1996 there was a median of 

three. That means people, most said well, it is useful. In 2003 the 
215

median was two, so they are much more convinced that this is done well. 

And the same result is with a question to what extent do you agree or 

disagree that the IPCC reports accurately reflect the consensus of thought 

within the scientific community. So there is broader agreement that the 

community is doing right even though I don’t think that the Oreskes 

study was done well and there have been numerous responses on that 

which have not been accepted by science for whatever reasons. 

 The last transparency, please. We have to keep in mind that climate 

change science takes place in a cultural context. It has something to do 

with what we think we have been trained at and a possibly remarkable 

result is that the concept of anthropogenic climate change is not new in 

Western culture. This is not a new invention in the history of this. We 

have documented very many cases and the first scientific publication we 

have on that is from 1781 by a physician named Williamson from 

Philadelphia who was speaking about the changing climate due to human 

action. At that time the weather in this part of the world was greatly 

improved because of taking away forests. 

 Second, climate change science is something what we call postmormal, that means it goes along with high uncertainties and high 

relevance. In that case, it is quite normal that the boundaries between 

value-driven agendas and curiosity-driven science get blurred and we 

should admit that there is a considerable influence of extrascientific 

agendas on the scientific process of climate change studies. I think we 

have seen that today also. The processes of climate change studies need 

to be analyzed and accompanied by social and policy scientists. So this 

process we are seeing here, how we argue, we should be something like--

yes, always an analysis by social scientists and I think what Dr. Wegman 

and his colleagues started to do was quite useful in this respect, that we 

understand to what extent we are driven by non-scientific motives, and 

this ends my presentation here. 

 [The prepared statement of Dr. Hans von Storch follows:] 

PREPARED STATEMENT OF DR. HANS VON STORCH, DIRECTOR OF INSTITUTE FOR COAST 

RESEARCH, GKSS-RESEARCH CENTER, GERMANY

Introduction of person 

I, Hans von Storch, have been actively involved in climate science since the early 

1980s. I have held positions with the Meteorological Institute of the University of 

Hamburg and at the Max-Planck Institute for Meteorology in Hamburg. At the present 

time, I am a director of the Institute for Coastal Research of the GKSS Research Center 

in Germany. I have co-authored more than 120 peer-reviewed articles on various issues 

of climate dynamics, climate statistics, climate change and climate impact as well as the 

textbook “Statistical Analysis in Climate Research” (together with Francis Zwiers) 

published by Cambridge University Press. I was a lead author of Chapter 10 of the Third 

Assessment Report of the IPCC, but I am not involved in the Fourth Assessment Report 

of the IPCC. 
216

Based on the scientific evidence, I am convinced that we are facing 

anthropogenic climate change brought about by the emission of greenhouse gases 

into the atmosphere. 

For further personal details please refer to my web-page: http://w3g.gkss.de/staff/storch. 

Hans von Storch 

Director of Institute for Coastal Research, GKSS Research Center, Geesthacht, Germany 

Professor at Meteorological Institute, University of Hamburg, Hamburg, Germany 

e-mail: hvonstorch@web.de, mobile +49 171 212 2046 

Outline 

I briefly address three aspects of the hockey-stick issue, namely 

1. Scientific aspects: 

- How valid are the regression-type methodologies for reconstruction historical 

climates? 

- How relevant are these reconstructions for claims that we presently experience 

a climate change outside the range of what we consider as “normal” (no human 

interference). 

2. The process of achieving success of a scientific knowledge claims in the 

climate science community: 

- Independence of the review process or presence of gatekeepers. 

- Reproducibility 

- Selection process by Nature & Science. 

- Acceptance by IPCC assessment process. 

3. The social conditioning of climate science: 

- The history of perceived anthropogenic climate changes. 

- Post-normal science. 

On the basis of my analysis I draw a couple of conclusions, chief being that the 

process of climate science must be organized in a sustainable manner. This means that 

climate science should be conducted with a low sense of subjective passion; that climate 

science provides “if-then” answers to questions society poses; that it presents to the 

society a broad range of possible policy responses and does not restrict the range of 

policy options to a small corridor that appeals to certain value-driven agendas. 

The conditioning of science by the culture of its actors and society is unavoidable. 

However, the scientists can attempt to make such influences explicit by acknowledging 

and explicitly reflecting on such influences, especially by engaging social scientists in the 

process of critical self-reflection. The Wegman-report claims that a major problem in 

studies such as MBH would be an insufficient engagement by mainstream statisticians. I 

think a major problem with this study and its transformation into a policy-relevant issue 

is an insufficient comprehension of the social dynamics of the post-normal process of 

(not only) climate science. 

There are three appendices to this document: 

1. My responses to the “Boehlert”-questions given at the NRC hearing on March 

2, 2006 in Washington. 

2. A contribution to the debate about the “Barton-letters” on the “Prometheus”-

weblog http://sciencepolicy.colorado.edu/prometheus/ dated July 8, 2005 

(http://sciencepolicy.colorado.edu/prometheus/archives/climate_change/000486

hans_von_storch_on_b.html) 

3. An English translation of an article published in the German weekly “DER 

SPIEGEL” (4/2005): von Storch and Stehr: A climate of staged angst. 

(http://sciencepolicy.colorado.edu/prometheus/archives/climate_change/000343

a_climate_of_staged_.html) 
217

Scientific aspects 

How valid are the regression-type methodologies for reconstruction historical 

climates? 

The key statistical assumption of any of such methods is the uniformity of 

informational content in the proxies which are regressed on the climate variables (mostly 

temperature). In other words, are these data influenced by non-climatic variable factors 

(inhomogeneity), is the transfer function linking proxies and temperature constant in time 

(stationarity)? Likely, most if not all proxy data (tree rings, coral rings, vine harvests) 

suffer from some inhomogeneities and instationarities. This is unavoidable and has to be 

dealt with by using additional insight into the system, e.g. by data assimilation 

approaches combining limited theoretical (models) and empirical knowledge (uncertain 

data). 

Regression-type models are designed so that they return only part of the full 

variability of the variable of interest, namely that part which can be traced back to the 

proxies. Not all of the variability can be accounted for in this way. The difference in 

variability of temperature and of proxy-derived temperature is dealt with by “scaling”, 

i.e., by applying a suitable normalization. If “scaling” is used, then the basic principle of 

regression is violated, as the part of variability in the predictand (temperature), which can 

not statistically traced back to the predictor (proxy), is nevertheless related to predictorvariability. Scaling is useful, when the transfer function is not regression (screening of 

co-variability of two variables) but based on physical arguments. 

Nevertheless, attempts like those by MBH are useful and should be explored. They 

may provide useful estimates. The problem with MBH was that the result was presented 

by the IPCC and others in a manner so that one could believe a realistic description of 

historical temperature variations had successfully been achieved. The NRC report 

published in June 2006 has made clear that such a belief was incorrect. 

How relevant are these reconstructions for claims that we presently experience a 

climate change outside the range of what we consider as “normal” 

Whether the present climate is influenced by non-natural factors is answered 

through “detection” studies. Such studies are based on the insight that the predicted signal 

of human-caused climate change should emerge in most recent times from the natural 

variability. Second, one would expect it to manifest itself with a higher “than normal” 

rate of change. Thus, the signal is expected to be a rapid warming in the most recent past. 

The method to test this hypothesis is to find out if we have a “steeper-than-normal” 

recent upward temperature trend. The hypothesis is not “we have a period which is 

warmer than ever in historical times”. In that sense the claim whether the last decade is 

the warmest of the past millennium is not relevant to detection; the question is whether 

the recent rate of warming is markedly stronger than what has happened in the past. 

The hypothesis is tested by framing the problem as a statistical test of a null 

hypothesis. The null hypothesis reads “the present trend is of natural origin”. Then, one 

determines the range of trends consistent with natural variability – and rejects the null 

hypothesis (and accepts the hypothesis that the trends is not of natural origins) if the 

present trend is larger than, say, 97.5% of trends originating entirely from natural 

variability. 

The crux of this approach is of course the determination of the range of trends which 

are observable under natural conditions. To do so, one may rely only on the instrumental 

period, which is contaminated by the expected signal and rather short, on multi-century 

reconstructions as MBH and on extended model simulations of undisturbed conditions. 

Obviously the determination of the range of “normal” trends is uncertain and absolute 

certainty can not be attained within a reasonable time. 
218

We1 have examined which range the different historical reconstructions suggest. To 

do so, the time series of reconstructions have been “modelled” as a long-memory process, 

and standard deviations of trends are derived. Here, the trend is defined as the difference 

of two 30 years means 100 years apart. Then these trends are determined from the 

instrumental record as given as multiples of the standard deviations derived from the 

different reconstructions. 

The result is given in the diagram; the curves are all the same, but they differ in 

scale because of the unit of different standard deviations derived from the reconstructions 

given at the figure caption. The horizontal dashed lines mark 2, 2.5 and 3 standard 

deviations. Two standard deviations correspond to a risk of false rejection of the null 

hypothesis of 2.5%. 

Obviously, in all cases, the critical 2-standard deviation mark is passed sometimes in 

the past decades; in case of MBH this happens very early, while in Moberg’s more 

variable reconstruction at about 1980. 

I conclude that the claim of “detection of anthropogenic climate change” is 

valid independently of which historical temperature reconstruction one chooses to 

believe in. 

It should also been taken notice that the claims of successful detection on nonnatural warming trends and its attribution to chiefly elevated greenhouse gas 

concentrations in the atmosphere in the Third Assessment report were not based on the 

historical reconstructions but on the analysis of the instrumental temperature record as 

well as on numerical experiments with climate models. 

The process of achieving success of a scientific knowledge claim in the climate 

science community 

A normal condition in the progress of science is that knowledge claims are accepted 

only after a “peer-review” process. The peer-review process attempts to assure that 

knowledge claims are consistent with the empirical evidence, and properly related to 

contemporary accepted knowledge claims, and that the methods are sound and are 

reproducibly described. The “peer-review” process does not eliminate the possibility that 

new ideas are rejected since they may contradict contemporary, powerful but possibly 

false knowledge claims (see Ludwik Fleck’s seminal book on “Generation of a Scientific 

Fact”). In order to minimize such a danger, the verdict of peer-reviewers should, to first 

order approximation, be independent of the persons involved in the review process. 

Nonetheless, the danger is that a few scholars may become powerful gatekeepers, for 

 

1

 Rybski, D., A. Bunde, S. Havlin,and H. von Storch, 2006: Long-term persistence in climate and the 

detection problem. Geophys. Res. Lett. 33, L06718, doi:10.1029/2005GL025591 
219

example as reviewers who are regularly called upon or as editors of scientific journals. 

The primary goal of such gatekeepers is to fend off publications which may contradict 

their own thinking, and not to ensure that only internally consistent and plausible 

publications reach the market of knowledge claims (i.e. scientific journals). 

Unfortunately this seems to have happened in the field of historical global climate 

reconstructions, where a small group of scientists has exerted an undue control of the 

entire field. 

Usually, a further mechanism more closely tied to the substance of research is used 

to quality-control scientific knowledge claims, namely reproducibility. This mechanism 

has ceased to operate in some quarters of paleo-climate science, since some scientists 

consider “their” data as their personal property and not that of the scientific community, 

so that others are unable to challenge conclusions drawn from these data by analysing the 

raw data in their own manner. Although such secrecy is a very human trait it violates the 

norms of science. Even hostile competitors should have an opportunity to independently 

re-examine the empirical evidence for conclusions drawn by others, in particular when 

they become relevant for the policy domain. Data must be become public; the methods 

employed must be described in algorithmic detail. 

Another relevant aspect is the functioning of the two prestigious journals “Science” 

and “Nature”. The journals enjoy high esteem within and outside of the scientific 

community as having the highest scientific standards, which is not always the case. The 

contents of Nature and Science also receive exceptional attention in the media worldwide. However, different from “normal” scientific journals, the editorial decision to 

accept a scientist’s contribution to Science or Nature is also based on the newsworthiness 

of the research contribution. The presented results must not only be valid and innovative 

but must also be of interest for a wider community of readers. Such a criterion is 

reasonable from a economic point-of-view, but it clearly introduces a filter in what is 

reaching the public is not solely based on the scientific merit of research. Research results 

with stronger media appeal fare better in this competition of scientific findings; results 

biased towards higher sensitivity to human interference are more interesting to a broad 

audience than findings that report low sensitivities. In addition, there may also be a bias 

towards certain authors, who are well known, because they enjoy public visibility, or 

command appealing writing skills, “sell” well. Sometimes such contributions are invited. 

Another problem with the same journals is that their articles must be relatively short 

so that technical aspects cannot be described in any detail; indeed, the MBH publication 

was cursory on the methodical side – thus the statistical method, the validation and the 

reproducibility, have not been seriously subject to the review process. Ironically, after 

publication in “Nature” the method was considered “peer-reviewed” and thus valid. 

However, this was not the case, as the method had not been properly described. 

The IPCC has different levels of operation – the generation of the technical chapters, 

which is done by a group of “lead authors”, headed by “convening lead authors”, and the 

process of arriving at a SPM (Summary for policymakers) and other overall assessment 

documents, which is done by the convening lead authors and representatives of the 

countries. 

How the selection process of lead and convening lead authors is done, I do not know 

– but it is clear that the “lead authors” are supposed to be experts in the field. This leads 

to the situation that the IPCC chapters are dominated by the authors of the most 

influential articles in their respective fields of research. Participation as a lead or 

convening lead author has the advantage that one can make sure that one’s own work is 

positively covered in the IPCC report. However, most lead and convening lead author 

excel as honest brokers, but some level of gatekeeping may prevail. Indeed, the 

reputation of the IPCC among scientist has increased to very high levels in the past years. 

The IPCC procedure differs markedly from the procedure adopted by the National 

Research Council assessment. In that case, a group of eminent scientists was chosen, who 
220

have contributed to the issue only little or not at all, but have a god understanding of the 

field as a whole. These scientists then invited a group of experts to present the different 

angles and knowledge claims. I consider the NRC procedure better in assessing the field 

of knowledge than the IPCC approach. It may be, however, that the NRC approach can 

not be used for such a complex and large field, which the IPCC is covering. 

In case of the MBH temperature reconstruction one should note that in the technical 

chapter of the TAR different reconstructions had been presented; it was the SPM and the 

synthesis report, where the range of reconstructions was reduced to just one, the MBH. It 

would be interesting to learn how this could have happened. 

The social conditioning of climate science

Science is a social process, which, as all social processes, is conditioned by the 

culture of the actors. This does not mean that scientists would do their analysis 

irrationally or in a biased manner, but it means that our questioning may by guided by 

culturally constructed concerns and interests. Also, we may be convinced of the validity 

of some findings more easily if these findings are consistent with our prior layknowledge. 

The history of perceived anthropogenic climate changes 

It has often been claimed that anthropogenic climate change is a recent concept. This 

is incorrect. In the history of ideas of the past 1000 years, we2 have found a number of 

occasions when (western) people have used the concept to explain observed changes: 

“During the last 20 years the concept of anthropogenic climate change has left 

academic circles and become a major public concern. Some people consider 

‘global warming’ as the major environmental threat to the planet. Even though 

mostly considered a novel threat, a look into history tells us that claims of 

humans deliberately or unintentionally changing climate is a frequent 

phenomenon in Western culture. Climate change, due to natural and 

anthropogenic causes, has often been discussed since classical times. 

Environmental change including climate change was seen by some as a biblical 

mandate, to ‘complete the Creation’. In line with this view, the prospect of 

climate change was considered as a promising challenge in more modern times. 

Only since the middle of the 20th century, has anthropogenic climate change 

become a menacing prospect. The concept of anthropogenic climate change 

seems to be deeply embedded in popular thinking, at least in Europe, which 

resurfaces every now and then after scientific discoveries. Also, extreme 

weather phenomena have in the past often been explained by adverse human 

interference.“3

This finding is insofar relevant as it points out that we, as members of the western 

culture, are somehow prepared to accept “anthropogenic influence” as an explanation for 

otherwise unexplainable events, such as a cluster of extreme events. Our common 

understanding is that such a human influence would be associated with negative impacts. 

This pre-conditioning may influence our process of drawing conclusions, in particular 

when we (scientists) deal with the problem of transferring scientific findings into the 

political arena. 

 

2

 von Storch, H., and N. Stehr, 2000: Climate change in perspective. Our concerns about global 

warming have an age-old resonance. nature 405, 615 

3

 von Storch, H. and N. Stehr, 2006: Anthropogenic climate change - a reason for concern since the 

18th century and earlier. Geogr. Ann., 88 A (2): 107–113. 
221

Post-normal science. 

Most of environmental science is what sociologists call “post-normal”, i.e., loaded 

with high uncertainty on an issue of great practical importance. Climate change science is 

an example of such post-normal science.4

A characteristic of post-normal science is that the boundaries between science and 

value-driven agendas get blurred; that representatives of NGOs are considered to know 

better about the functioning and dynamics of systems than scientists; that parliamentarian 

committees delve into the technicalities of science; that amateurs engage in the technical 

debate: and that some scientist try to force “solutions” upon policymakers and the public. 

In such a situation it becomes entirely possible that individual scientists emphasize those 

insights which are assumed to influence certain policy decisions more forcefully, while 

downplaying others. 

Typical for such a post-normal situation is the flooding of the media with books and 

movies which dramatize the issue. Recent examples include: The Day After Tomorrow, 

State of Fear, Satanic Gases, The Revenge of Gaia, and An Inconvenient Truth. 

In this situation we need a discussion, not only among scientists about the role of 

science for the public, which must be the provisions of options for policy, not the 

narrowing of the range of options to satisfy different worldviews. To limit the influence 

of non- or pre-scientific knowledge claims, social and policy scientists need to analyse 

the different processes in climate science, and the interdependence of culture, policy, 

politics, media and climate science. Even if science can never be fully “objective”, it may 

nevertheless be possible to make climate science a considerably more objective practice 

than what we have in these days. 

 

4

 Bray, D. and H. von Storch, 1999: Climate Science. An empirical example of postnormal science. 

Bull. Amer. Met. Soc. 80: 439-456 
222

Appendices

(a) My answers to Chairman Boehlerts questions, given at the NRC hearing 

What is the current scientific consensus on the temperature record of the last 1,000 or 

2,000 years? What are the main areas of uncertainty and how significant are they? 

• There is consensus on the “blade”, but the claimed smoothness of the shaft is 

likely false. 

• The main problem is the loss of information encoded in the proxy data and the 

shortness of the instrumental record for training the statistical models. 

What is the current scientific consensus on the conclusions reached by Drs. Mann, 

Bradley and Hughes? What are principal scientific criticism of their work and how 

significant are they? 

Has the information needed to replicate their work been available? Have other scientists 

been able to replicate their work? 

• There is no consensus on the claims (which?) made by MBH. The main critique 

is that the method is suffering from a too large loss of variability on long time 

scales. 

• No, the information required for replication was not made available in a 

suitable manner. The original publication in “nature” did not provide this 

information and was obviously published without careful review of the 

methodology. 

• Yes, the details of the method were finally determined, among others by Bürger 

et al., who checked a wide range of combinations of details – which all gave 

widely different results. 

How central is the debate over the paleoclimate temperature record to the overall 

consensus on global climate change? How central is the work of Drs. Mann, Bradley and 

Hughes to the consensus on the temperature record? 

• The main conclusions about “detection and attribution” are drawn from the 

instrumental record and models; the different reconstructions do not contradict 

“detection”. 

• The MBH work is widely accepted as truth outside of people directly engaged 

in the issue, because of a less than satisfactory marketing by the IPCC. 
223

(b) My posting on weblog “Prometheus” July 08, 2005 on the “Barton letters” 

My reaction to Rep. Barton's requests is split. In his five letters, he is asking for 

information from two different groups, namely institutions with reviewing 

responsibilities (IPCC, NSF) and individuals with scientific responsibilities (M, B and 

H). I find his inquiry of the performance of the institutions IPCC and NSF valid, but the 

interrogative questioning of the individual scientists is inadequate. 

a) Scientists. The scientists have the task to be innovative, creative, to try new 

avenues of analysis and the like. They have the right to err, the right to suggest 

explanations and interpretations which may need to be revised at a later time. They 

should document what they have done, so that others can replicate. 

However, this documentation often can not take the form of keeping runnable old 

codes of the applied algorithms, simply because the software is no longer consistent with 

quickly replaced hardware. For instance, most of the state-of-the-art coupled AOGCMs 

used in the mid 1990s are simply no longer available and running at, for instance, the 

German Climate Computer Center. After replacing a high performance computer with a 

new system, the standard model codes, including community models, need to be adapted 

to the requirements and possibilities of the new system, and the old code will often no 

longer run. This has nothing to do with the norms of the community but simply with 

technological progress. Also specific commercial libraries of specialized algorithms may 

no longer be accessible. Data and codes written on old magnetic tapes or even floppies 

are usually no longer readable. 

Therefore the documentation must take the form of a mathematical description of 

the algorithms used. This is in many if not most cases sufficient for replication. Also, the 

intention of replicability is not to exactly redo somebody's simulation and analysis, but to 

find the same result with a similar code and different but statistical equivalent samples. 

The problem is usually not that the codes contain errors (even if many of the more 

complex ones likely contain minor, mostly insignificant errors), but that specific elements 

of implementation and specific aspects of the considered sample of evidence will lead to 

conclusions, which do not hold if another sample is considered or a different but equally 

good algorithm is employed. The reason is that we want to learn about the dynamics of 

the real world, and these insights should not depend on random choices in sampling and 

implementation. We generally do not expect scientists to manufacture results, or that 

unintended but significant errors will affect the eventually published conclusions. 

Having this situation in mind, I consider Rep. Barton's requests to the three scientists 

as inadequate and out-of-scale. However, the language used by Rep. Barton makes me 

perceiving this request as aggressive and on the verge of threatening. 

The situation is different with the second groups of recipients, the: 

b) "Reviewers". Reviewers have a different role, namely they shall make sure that 

the standards of scientific reporting are held up. They have to ensure that the proposed 

explanations are considered by independent experts as to whether the presented analysis 

seems valid and in principle reproducible. "Independent" means that the reviewers have 

no vested interests for or against the case presented. In the conventional set-up these 

interests usually refer to academic schools of thought, but in the unfortunate, post-normal 

case of climate science independence from the political utility of the case should be 

established. 

In this case, I find the inquiry of Rep. Barton to be valid. The IPCC has failed to 

ensure that the assessment reports, which shall review the existing published knowledge 

and knowledge claims, should have been prepared by scientists not significantly involved 

in the research themselves. Instead, the IPCC has chosen to invite scientists, who 

dominate the debate about the considered issues, to participate in the assessment. This 

was already in the Second Assessment Report a contested problem, and the IPCC would 

have done better in inviting other, considerably more independent scientists for this task. 
224

Instead, the IPCC has asked scientists like Professor Mann to review his own work. This 

does not represent an "independent" review. 

The NSF seems to have failed to ensure that sufficient information is provided about 

work done under its auspices. 

Rep. Barton should also have asked the editors of "Nature", why the original 

manuscript was accepted for publication even though the key aspect of replicability was 

obviously not met by the MBH manuscript. Actually, MBH could not meet this condition 

because of the strict length limitation of that journal (nowadays one would ask for 

extensive Supplementary Online Material). One should ask why the manuscript was 

accepted nevertheless - and not, as in many other cases, the manuscript was 

recommended to be published in a "normal" journal without the severe length limitations. 

I believe the reasons for Nature were the journalistic reasons - namely the expected broad 

interest in the subject. One should also ask why after the critique von McIntyre and 

McKitrik only MBH got the opportunity for a correction of his paper, whereas the short 

manuscript of their opponents was rejected. 

To conclude - the requests to M, B and H are not fair but may unfortunately lead to a 

repressive atmosphere within climate science; the requests to NSF and the IPCC, 

however, are appropriate, as these institutions may have failed in a primary task, namely 

to guarantee an open scientific discourse. And, Rep. Barton should have included the 

editors of Nature in his analysis. 
225

A Climate of Staged Angst 

By Hans von Storch and Nico Stehr 

The days are gone when climate researchers sat in their ivory towers packed to the 

rafters with supercomputers. Nowadays their field has become the stuff of thrillers, and 

they themselves have risen to take on the leading roles. The topic is so hotly contested, 

the prognoses so spectacular, that they are no longer merely the subject of media reports; 

now the specialists in staged apocalypse have moved in. Last year Roland Emmerich 

depicted a climatic collapse provoked by humankind in his film “The Day After 

Tomorrow.” Since last week the belletristic counterpart has been available in German 

bookstores: the novel “State of Fear,” by the best-selling author Michael Crichton. 

The thriller is about the violent conflict between sober environmental realists and 

radical environmental idealists. For the idealists, the organized fear of abrupt climate 

change serves as a handy weapon. They interpret every somehow unusual weather event 

as proof of anthropogenic global warming. “You have to structure your information so 

that it’s always confirmed, no matter what kind of weather we have,” the P.R. consultant 

for the environmentalist organization advises. The realists, who protest that the evidence 

that human activity has increased meteorological extremes is thin, are fighting a losing 

battle. Their dry scientific arguments are unable to gain any ground against the colorful, 

horrific visions of the climate idealists. 

Film and novel have certain aspects in common. Where Emmerich holds out the 

prospect of a threatening climate catastrophe, the book prophesies an economic collapse. 

In both cases, greenhouse gases produced by humankind are the culprit – in the film, 

because the emissions themselves are too much; in the book, because the fear of them is. 

The idealists are so obsessed with their mission that ultimately, in order to rouse the 

public, they themselves bring about the foretold catastrophes. 

Despite a good deal of factually untrue – and thus all the more striking – 

compression, Crichton has quite correctly observed the dynamic of the paths of 

communication among scientists, environmentalist organizations, the state and the 

civilian population. For there is indeed a serious problem for the natural sciences: 

namely, the public depiction and perception of climate change. Research has landed in a 

crisis because its public actors assert themselves on the saturated market of discussion by 

overselling the topic. 

Climate change of man-made origin is an important subject. But is it truly the “most 

important problem on the planet,” as an American senator claims? Are world peace, or 

the conquest of poverty, not similarly daunting challenges? And what about population 

growth, demographic change or quite normal natural disasters? 

In the U.S., only a very few remain interested in the greenhouse effect. At the end of 

the 1980s, the situation was still different. That was the era of the great drought of 1988, 

the Mississippi flood of 1993, and the climate capers ought by rights to have taken off in 

earnest from that point. But that never happened in the U.S., and interest petered out. 

According to a survey by the CBS television network in May 2003, environmental 

problems were no longer ranked among the six most important subjects; and even within 

environmental problems, the topic of climate came in only in seventh place. In Germany, 

so far, things are still seen differently. But for how much longer? 

In order to keep the topic of “climate catastrophe” – a concept nonexistent outside 

the German-speaking world, by the way – continually in the public eye, the media feel 

obligated, exactly like the protagonists in Crichton’s thriller, to keep framing the topic “a 

bit more attractively.” At the beginning of the 1990s – severe storms had just swept 

through the country – one could read and hear in the German media that storms were due 

to become ever more severe. Since then, storms have become rarer in northern Europe. 

But no notice is taken of this. The fact that barometric fluctuations in Stockholm have 
226

shown no systematic change in the frequency and severity of storms since Napoleon’s 

time is passed over in silence. Instead, there is now talk of heat waves and floods. Very 

much in the style of Crichton’s instigators of fear, the story is now that all manner of 

extreme events are on the increase. Thus even drought in Brandenburg and deluge on the 

Oder fit the picture without apparent contradiction. 

Add to this – besides normal floods and storms – other, more dramatically 

threatening, scenarios: the reversal of the Gulf Stream and the resultant cooling of large 

areas of Europe, for instance, or even the rapid melting of the Greenland ice pack. The 

question has already been publicly raised whether perhaps even the Asian tsunami can be 

attributed to the disastrous effects of human activity. 

This will not be able to hold the public’s attention for long. Soon people will have 

become accustomed to these warnings, and will return to the topics of the day: 

unemployment and Hartz IV, Turkey’s entry to the E.U. or whether Borussia Dortmund 

can avert disaster on the soccer field and in the boardroom. Thus we will see firsthand 

how the prophets of doom will draw the climatic dangers in even more garish colours. 

The terrifying visions to haunt the future can already be guessed at: the breakup of the 

west Antarctic shelf ice, which will cause the water level to rise much more rapidly, and 

after a few decades of uncontrolled carbon dioxide emissions, an abrupt rise in 

temperatures, giving us a deadly atmosphere like that of Venus. Prospects such as these 

have long been in the public eye; can they not compete effortlessly with Emmerich’s 

Hollywood images? 

The costs of stirring up fear are high. It sacrifices the otherwise so highly valued 

principle of sustainability. A scarce resource – public attention and trust in the reliability 

of science – is used up without being renewed by the practice of positive examples. 

But what do climate researchers themselves think, how do they deal with the media 

and the population? 

Public statements by noted German climate researchers give the impression that the 

scientific bases of the climate problem have essentially been solved. Thus science has 

provided the prerequisites for us now to react appropriately to the goal; meaning, in this 

case, to reduce greenhouse gas emissions as much as possible. 

This does not at all reflect the situation in the scientific community. A considerable 

number of climatologists are still by no means convinced that the fundamental questions 

have been adequately dealt with. Thus, in the last year a survey among climate 

researchers throughout the world found that a quarter of the respondents still harbor 

doubts about the human origin of the most recent climatic changes. 

The majority of researchers are indeed of the opinion that global climate change 

caused by human activity is occurring, that it will accelerate in the future, and that it will 

thus become more readily apparent. This change will be accompanied by warmer 

temperatures and a higher water level. In the more distant future, that is, in about 100 

years, a considerable increase of atmospheric greenhouse gases is foreseen, together with 

an increase in heavy precipitation in our latitudes; in some regions there could be more 

powerful storms, in others weaker ones. 

But again and again, there are scientists to whom, true to the alarmists’ maxim in 

Crichton’s book, this does not sound dramatic enough. Thus, more and more often they 

connect current extreme weather events with anthropogenic climate change. To be sure, 

this is usually carefully formulated; interviews sound something like this: “Is the flooding 

of the Elbe, the hurricane in Florida, this year’s mild winter evidence for the climate 

catastrophe?” Answer: “That’s scientifically unproven. But many people see it that way.” 

Neither of these statements is false. In combination, however, they suggest the 

conclusion: Of course these weather events are evidence. Only no one dares to say this 

explicitly either. 

The pattern is always the same: the significance of individual events is processed to 

suit the media and cleverly dramatized; when prognoses for the future are cited, among 
227

all the possible scenarios it is regularly the one with the highest rates of increase in 

greenhouse gas emissions – and thus with the most drastic climatic consequences – that is 

chosen; equally plausible variations with significantly lower emission increases go 

unmentioned. 

Whom does this serve? It is assumed that fear can motivate listeners, but it is 

forgotten that it mobilizes them only in the short term. Climatic changes, however, 

demand long-term reactions. The effect on public opinion in the short view may indeed 

be “better,” and thus may also have a positive effect on reputation and research funding. 

But in order for this to function in the long run, each most recent claim about the future 

of the climate and of the planet must be ever more dramatic than the previous one. Once 

apocalyptic heat waves have been predicted, the climate-based extinction of animal 

species no longer attracts attention. Time to move on to the reversal of the Gulf Stream. 

Thus there arises a spiral of exaggeration. Each individual step may appear to be 

harmless; in total, however, the knowledge about climate, climate fluctuations, climate 

change and climatic effects that is transferred to the public becomes dramatically 

distorted. 

Sadly, the mechanisms for correction within science itself have failed. Within the 

sciences, openly expressed doubts about the current evidence for climatic catastrophe are 

often seen as inconvenient, because they damage the “good cause,” particularly since 

they could be “misused by skeptics.” The incremental dramatization comes to be 

accepted, while any correction of the exaggeration is regarded as dangerous, because it is 

politically inopportune. Doubts are not made public; rather, people are led to believe in a 

solid edifice of knowledge that needs only to be completed at the outer edges. 

The result of this self-censorship in scientists’ minds is a deaf ear for new and 

surprising ideas that compete with or even contradict conventional patterns of 

explanation; science degenerates into being a repair shop for popular, politically 

opportune claims to knowledge. Thus it not only becomes sterile; it also loses its ability 

to advise the public objectively. 

One example of this is the discussion of the so-called “hockey stick,” a temperature 

curve that allegedly depicts the development over the last 1000 years, and whose shape 

resembles that of a hockey stick. In 2001 the Intergovernmental Panel on Climate 

Change, the committee of climate researchers appointed by UNO, rashly institutionalized 

this curve as the iconic symbol for anthropogenic climate change: At the end of a 

centuries-long period of stable temperatures, the upward-bent blade of the hockey stick 

represents the human influence. 

In October 2004, we were able to demonstrate in the scientific journal “Science” that 

the methodological bases that led to this hockey-stick curve are mistaken. We wanted to 

reverse the spiral of exaggeration somewhat, without also relativizing the central message 

– that climate change caused by human activity does indeed exist. Prominent 

representatives of climate research, however, did not respond by taking issue with the 

facts. Instead, they worried that the noble cause of protecting the climate might have been 

done harm. 

Other scientists lapse into a zeal reminiscent of nothing so much as the McCarthy 

era. For them, methodological criticism is the spawn of “conservative think tanks and 

propagandists for the oil and coal lobby,” which they believe they must expose; 

dramatizing climate change, on the other hand, is defended as a sensible means of 

educating society. 

What is true for other sciences should also hold for climate research: Dissent is the 

motor of further development, Differences of opinion are not an unpleasant family affair. 

The concealment of dissent and uncertainty in favor of a politically good cause takes its 

toll on credibility, for the public is more intelligent than is usually assumed. In the long 

term, these allegedly so helpful dramatizations achieve the opposite of that which they 

wish to achieve. 
228

By doing so, however, both science and society will have wasted an opportunity. 

Hans von Storch, 55, heads the Coastal Research Institute of the GKSS Research Centre 

in Geesthacht, Germany; he is considered leading experts statistical analysis of 

climatological data and simulations. Together with Nico Stehr, 62, sociologist at the 

Zeppelin University in Friedrichshafen, Germany he has conducted ongoing research into 

the public perception of climate change. 

Translated by Paul Malone 

First published in Der Spiegel No. 4, 2005. 
229
230
231
232
233

 MR. WHITFIELD. Thank you, Dr. von Storch, and Mr. McIntyre, you 

are recognized for 5 minutes. 

MR. MCINTYRE. Good afternoon, Mr. Chairman and members of the 

committee. My name is Steve McIntyre. I appreciate the invitation to 
234

appear today to discuss my research coauthored with Ross McKitrick of 

the University of Guelph which in part led to today’s meeting. 

 I have three main messages. First, little reliance can be placed not 

only the original Mann reconstruction, various efforts to salvage it, or 

similar multi-proxy studies even ones which did not use Mann’s 

methodology. Second, peer review as practiced by academic journals is 

not an audit but something much more limited. In turn, scientific 

overviews such as the ones produced by IPCC or even by the NAS panel 

are based almost entirely on literature review rather than independent 

testing. Third, there is already an existing data archive which is 

excellent, but in order to make it work scientists actually have to archive 

their data and code. This is not done consistently in the paleoclimate 

community and it makes replication virtually impossible in many cases. 

Much of this work is funded by the U.S. Federal government and some 

very simple administrative measures under existing policies could 

alleviate many of the problems. 

 In the two reports, only one topic was specifically audited in the 

sense of independent testing as opposed to literature review, and that was 

simply whether Mann’s method was biased towards producing hockey 

stick-shaped series. Both reports verified this hotly contested result. 

Both panels agreed with varying emphasis that no confidence could be 

placed on reconstructions prior to 1600 and that Mann’s statistical 

methods were unsatisfactory. The Wegman report considered how such 

an error could have remained undetected. In addition to their comments, 

an important reason that the IPCC does not carry out independent tests. 

 Some comments of Dr. Bloomfield’s at the NAS press conference 

may lead people to believe that a hockey stick could be obtained from a 

simple average of all MBH proxies. This is simply not the case as you 

see by the graph on both screens. The NAS panel illustrated several 

other reconstructions but their consideration was merely a literature 

review. They did not attempt to replicate or audit these other studies as I 

have tried to do. Each one has replication problems. One of the 

criticisms of the Mann study recognized by the NAS panel was its use of 

bristle cones and closely related foxtails, a flawed proxy which the panel 

said should be avoided. However, they did not assess this. The impact 

of not using bristle cones can be substantial. Removal of merely two 

bristle cone series changes relative medieval modern levels in the 

Crowley and Lowery reconstruction that was shown to you earlier. The 

panel noted the so-called divergence problem in which temperatures in 

the last half of the 20th Century increase while tree ring widths and 

densities decrease. They offered no solution other than reduced 

confidence, but the problem is worse. How can we even trust the shape 

of the curve in previous warm periods if they miss the present one? Bias 
235

sampling can arise not simply from Mann’s principal component 

methods, but by non-random and biased selection of small samples. In 

this graph shown here, even the selection of a single site, of a different 

version from a single site can have a dramatic impact on a worldwide 

reconstruction. Here different versions impact the Briffa 2000 

reconstruction and all but one subsequent reconstruction shown in the 

various spaghetti graphs. The issue of the polar Urals is substantive. 

Naurzbaev et al., which included Mann’s coauthor Hughes, whose 

methods were cited by the NAS panel with a approval, concluded that 

medieval summer temperatures in this area were over 2.3 degrees 

Centigrade warmer than at present. 

 The Wegman reported noted pervasive problems in paleoclimate 

research practices. A simple policy shown here already in existence at 

the American Economic Review and other journals and in fact a policy 

introduced by Dr. Bernanke, presently Chairman of the Federal Reserve 

System, would alleviate many of these problems. There is no reason for 

journals not to adopt similar rules for paleoclimatology where data sets 

are similar in size and scale to many econometric studies. In fact, the 

1991 policy statement of the U.S. global change research program 

already requires data archiving and many agencies such as NASA have 

complied with these policies. However, the National Science Foundation 

does not and a senior NSF official wrote to me saying that dissemination 

of data was merely up to the professional judgment of the researchers. 

Ironically, even the NAS panel relied heavily on unarchived data. The 

Department of Energy itself does not comply. It funded the development 

of the well-known CRU temperature series used by IPCC but their 

agreements failed to ensure that even DOE has access to the supporting 

data. 

 Nothing that I say here should be construed as diminishing the 

seriousness of climate change as public issue. It is precisely because it is 

a serious issue that policymakers are entitled to the best possible 

information. You should not receive incorrect confidence assessments as 

happened with the hockey stick. You should discourage practices that 

interfere with efforts to verify results. 

 Finally, at the NAS press conference, when asked about overselling 

of the hockey stick, panelist Cuffy said that the IPCC sent a very 

misleading message through its prominent use. Yet IPCC procedures 

which permitted this remain unchanged for the upcoming fourth 

assessment report. 

 Thank you very much. 

 [The prepared statement of Mr. Stephen McIntyre follows:] 
236

PREPARED STATEMENT OF STEPHEN MCINTYRE, TORONTO, ONTARIO, CANADA

SUMMARY 

1. little reliance can be placed on the original MBH reconstruction, various efforts 

to salvage it or similar multiproxy studies, even ones which do not use Mann’s 

principal components methodology; 

2. peer review as practiced by academic journals is not an audit, but something 

much more limited. Scientific overviews, such as ones produced by IPCC or 

the NAS panel, are nearly entirely based on literature review rather than 

independent due diligence. 

3. much work in dispute is funded by the U.S. federal government. Some very 

simple administrative measures under existing policies could alleviate many of 

the replication problems that plague paleoclimate.

TESTIMONY 

Good morning, Mr Chairman and members of the Committee. 

My name is Stephen McIntyre. I appreciate the invitation to appear today to discuss 

my research, coauthored with Ross McKitrick of the University of Guelph. Our 

publications led in part to the reports of the NAS panel and the Wegman committee. 

A year ago, the University Corporation of Atmospheric Research (UCAR) issued a 

national news release stating that our “highly publicized criticisms of the MBH graph are 

unfounded.” Sir John Houghton, co-chair of IPCC, gave evidence to a Senate committee, 

stating that our results had been shown to be “largely false”. The situation today is 

different as both the NAS and Wegman reports have recognized our major findings while 

drawing different conclusions on their impact. 

I would like to convey three main messages today: 

1. little reliance can be placed on the original MBH reconstruction, various efforts 

to salvage it or similar multiproxy studies, even ones which do not use Mann’s 

principal components methodology; 

2. peer review as practiced by academic journals is not an audit, but something 

much more limited. Scientific overviews, such as ones produced by IPCC or 

the NAS panel, are nearly entirely based on literature review rather than 

independent due diligence. 

3. much work in dispute is funded by the U.S. federal government. Some very 

simple administrative measures under existing policies could alleviate many of 

the replication problems that plague paleoclimate. 

In the NAS and Wegman reports, only one topic has been specifically “audited” – in 

the sense of carrying out independent simulations as opposed to review of previous 

literature: 

• Mann’s principal component method is biased towards producing hockey stick 

shaped series. 

Both audits verified this result, first published by us, but hotly contested for the past 

two years. Both panels agreed (with varying emphasis) that MBH confidence claims were 

incorrectly calculated, indeed that no confidence intervals prior to 1600 could be 

calculated and that MBH statistical methods were unsatisfactory. 

The Wegman report considered why such an error could have remained undetected 

in such a prominent study, an issue not considered by the NAS panel. In addition to their 

comments, I note that IPCC does not verify information from the scientific literature. 

The NAS panel also endorsed our important criticism of MBH dependence on 

proxies known not to be temperature proxies, agreeing that bristlecones should be 

avoided. 
237

The NAS panel cited several other reconstructions, but their consideration was 

merely a literature review. They did not attempt to replicate or audit these other studies 

and cannot vouch for them. Having examined most of them closely, I do not believe that 

any of them provide robust or reliable information on relative medieval-modern levels. 

For example, some comments of Dr Bloomfield’s at the NAS press conference may 

lead people to believe that a hockey stick could be obtained from a simple average of all 

415 MBH proxies. This is not the case, as shown in Figure 1 below. 

Figure 1. Top – Average of all 415 MBH proxies; bottom – MBH reconstruction. 

The NAS panel illustrated four other multiproxy studies, as shown in Figure 2 

below. However, all four use bristlecones or closely-related foxtails. The panel did not 

analyse the impact on each study of avoiding bristlecones, as they elsewhere 

recommended. 

Figure 2. Excerpt from figure S-1 of NAS panel report 

The impact of avoiding bristlecones in accordance with the NAS recommendation 

can be substantial – as shown in Figure 3 for Crowley and Lowery 2000, where the 

removal of two bristlecone series changes relative medieval-modern levels. 
238

1000 1200 1400 1600 1800 2000

-0.4

-0.2

0.0

0.2

0.4

Figure 3. Left – Excerpt from Crowley (2000); right – replication with red showing effect 

without bristlecones and without instrumental splicing. 

The NAS panel noted the so-called “Divergence Problem”, in which temperatures in 

the last half of the 20th century increase, while tree ring widths and densities decrease, 

demonstrated here for a rare large-sample (387) study of “temperature-sensitive” sites 

[Briffa et al 1998]. NAS offered no solution other than reduced confidence. But the 

problem is worse: how can we even trust the shape of the curve in previous warm 

intervals, if they miss the present one? 

Figure 4. Ring widths and density from Briffa et al 1988. 

Biased sampling can arise not simply from Mann’s principal component methods, 

but from non-random and biased selection of small samples. If you “mine” or “snoop” a 

network of red noise looking for what appear to be “temperature-sensitive” trends, an 

average of the picks will also yield a hockey stick shaped series. The Wegman report 

shows evidence of non-random picking. While the NAS panel noted the potential impact 

of inclusion/exclusion of even individual series, they did not investigate it. Here is an 

important example that affects multiple studies. The first Briffa version of the Polar Urals 

series said that the early 11th century was among the coldest of the millennium; updated 

sampling in 1998 showed the opposite, but Briffa did not report it. Instead he substituted 

another series from a site 70 miles away with a hockey stick shape. This substitution had 

a dramatic impact on the medieval-modern relationship in the Briffa (2000) 

reconstruction and nearly all other subsequent studies. 
239

Figure 5. Left – three different versions of Polar Urals series. Top – from Briffa et al 

1995; middle – from Esper et al 2002 (the only use of this version); bottom – the version 

in Briffa (2000) and subsequent studies other than Esper et al 2002. Right: the impact on 

the reconstruction in Briffa (2000). Black – Briffa (2000) version; red – using Polar Urals 

update. . All series in standard deviation units and 21-year gaussian smooth. 

In our NAS presentation, we cited Naurzbaev et al 2004 (including MBH co-author 

Hughes) as offering a promising new line of handling tree ring data. NAS cited this with 

approval, but did not report their conclusion that medieval summer temperatures were 

over 2.3 deg C warmer or that medieval treelines in the Polar Urals (and elsewhere) were 

higher than modern treelines. 

Figure 6. Treelines at Polar Urals site (Shiyatov 1995). 

While the NAS panel did not address the issue of archiving, other than in 

generalities, the Wegman report noted pervasive problems in paleoclimate research 

practices. A simple policy – already in existence at the American Economic Review and 

other journals - would alleviate many of these problems. There is no reason not to 

require similar rules for paleoclimatology, where data sets and code are similar in size 

and scale. 

Submitters should be aware that the Editors now routinely require, as a condition of 

publication, that authors of papers including empirical results (including 

simulations) provide to this office, in electronic form, data and code sufficient to 

permit replication. 
240

To the extent that senior policy-makers have previously turned their attention to the 

matter, the 1991 Policy Statement of the U.S Global Change Research Program already 

requires data archiving after a limited period of exclusive use and, in 1997, provided 

recommended language for agencies to implement in grant agreements. Many agencies 

(e.g. NASA) have complied with these policies. 

The overall purpose of these policy statements is to facilitate full and open access to 

quality data for global change research. They ...represent the U.S. Government’s 

position on the access to global change research data.... 

For those programs in which selected principal investigators have initial 

periods of exclusive data use, data should be made openly available as soon as 

they become widely useful. In each case the funding agency should explicitly 

define the duration of any exclusive use period. 

 Yet when I copied NSF on a request for data necessary to replicate key MBH 

results, a program officer not only refused to support the request, but intervened to 

counsel Mann against supplying the data. 

Dr. Mann and his other US colleagues are under no obligation to provide you with 

any additional data ... His research is published in the peer-reviewed literature 

which has passed muster with the editors of those journals and other scientists who 

have reviewed his manuscripts. You are free to your analysis of climate data and he 

is free to his. 

 Subsequently, a senior NSF official said that dissemination of data was merely up 

to the “professional judgement” of the researchers. Ironically, the NAS panel relied 

heavily on unarchived data. 

In general, we allow researchers the freedom to convey their scientific results in a 

manner consistent with their professional judgement... 

The Department of Energy funded the development of the well-known CRU 

instrumental temperature series, used by IPCC and others. In response to a request for 

supporting data, Philip Jones, a prominent researcher said: 

We have 25 or so years invested in the work. Why should I make the data available 

to you, when your aim is to try and find something wrong with it? 

Although DOE had funded the collection, their past and present grant agreements 

had not ensured that even DOE had access to the supporting data and they said that they 

were unable to assist. 

Phil [is] not obligated under the conditions of past or present DOE proposal awards 

to provide these items to CDIAC. I regret we cannot furnish the materials you seek 

In conclusion, I re-iterate that you can place little reliance on any existing 

multiproxy study; that you need to distinguish between the limited due diligence of 

journal peer review and the substantive due diligence of an audit; and that simple 

administrative measures can substantially improve paleoclimate research practices. 

Both the NAS report and Wegman reports are valuable studies by accomplished 

authors. Nothing that I say here should be construed as diminishing the seriousness of 

climate change as a public issue. It is precisely because it is a serious issue that policymakers are entitled to the best possible information and should ensure that data, code and 

methods be accurately and completely archived and discourage practices that interfere 

with scientific reproducibility. 

References: 

See NAS Panel report. 
241

1

Presentation to the 

Subcommittee on Oversight and 

Investigations of the 

House Energy and Commerce 

Committee.

Stephen McIntyre

Toronto Ontario

Washington DC, July 19, 2006.

2

Overview:

1. little reliance can be placed on the original MBH 

reconstruction, various efforts to salvage it or on 

other similar studies, even ones which do not use 

Mann’s principal components methodology;

2. peer review as practiced by academic journals is 

not an audit, but something much more limited. 

Literature review is not independent due diligence.

3. much of the work in dispute is funded by the U.S. 

federal government. Some very simple 

administrative measures could accomplish much 

improvement regardless of one’s view on climate 

policy.
242

3

Both Panels Agreed ...

| MBH principal components method was biased 

toward producing hockey-stick shaped series 

| MBH claims to statistical significance were 

over-stated

| MBH claims to establish confidence intervals 

prior to 1600 should be rejected

The NAS panel also agreed: 

| MBH use of bristlecones should be avoided

4

A simple average of MBH proxies does 

not yield a hockey stick

Top: average of MBH proxies. Bottom: result of MBH method. 
243

5

NAS cited but did not audit 

other multiproxy studies

| all 4 rely on bristlecones; 2 of 4 even rely on Mann’s 

PC method

6

Avoiding bristlecones impacts medievalmodern levels in other studies

Left: Figure 4 of Crowley (2000) comparing that reconstruction to MBH. 

Instrumental data has been spliced since 1870.

Right in red – Without bristlecones, horizontal line showing closing level 

with at least 5 proxies. No instrumental data is spliced. 

1000 1200 1400 1600 1800 2000

-0.4

-0.2

0.0

0.2

0.4
244

7

Divergence problem:

Proxies trend down while

temperatures trend up 

Source: Average of 387 temperature-sensitive sites (Briffa 

et al 1998)

8

Polar Urals versions are inconsistent; 

selection impacts “worldwide”

reconstruction

Left: Three versions of Polar Urals data used in multiproxy studies. Top 

and bottom series used in all but one study. 

Right – red shows impact of using Polar Urals update in Briffa (2000) 

reconstruction

-1

0

1

2 Briffa 1995

-1

0

1

2 Updated

800 1000 1200 1400 1600 1800 2000

-1

0

1

2 Yamal
245

9

Medieval treelines were higher than at 

present in Siberia. Naurzbaev et al 2004 

estimated that medieval summer 

temperature were warmer by more than 

2.3 deg C.

10

Archiving policy at American 

Economic Review

Submitters should be aware that the Editors 

now routinely require, as a condition of 

publication, that authors of papers including 

empirical results (including simulations) 

provide to this office, in electronic form, data 

and code sufficient to permit replication.
246

11

1991 US Global Research Change 

Program Policy Statement

The overall purpose of these policy statements is to facilitate 

full and open access to quality data for global change 

research. They ...represent the U.S. Government’s position 

on the access to global change research data.

...

For those programs in which selected principal 

investigators have initial periods of exclusive data use, 

data should be made openly available as soon as they 

become widely useful. In each case the funding agency 

should explicitly define the duration of any exclusive 

use period.

12

NSF leaves compliance up to the 

researcher and the journals

Program Officer:

Dr. Mann and his other US colleagues are under no 

obligation to provide you with any additional data ... His 

research is published in the peer-reviewed literature which 

has passed muster with the editors of those journals and 

other scientists who have reviewed his manuscripts. You 

are free to your analysis of climate data and he is free to his.

Senior Official: 

In general, we allow researchers the freedom to convey 

their scientific results in a manner consistent with their 

professional judgement...
247

13

DOE funds collection of the most 

widely-used temperature data but fails 

to ensure access to it

Jones: 

We have 25 or so years invested in the work. Why should I 

make the data available to you, when your aim is to try and 

find something wrong with it.

DOE:

Phil [is] not obligated under the conditions of past or present DOE 

proposal awards to provide these items to CDIAC. I regret we 

cannot furnish the materials you seek

14

End of Presentation

Sir John Houghton at press conference releasing IPCC Third 

Assessment Report.
248

15

Robustness

| Burger and Cubasch (2005)

 MR. WHITFIELD. Thank you, Mr. McIntyre, and at this time I am 

going to recognize the full committee Chairman, Mr. Barton, for 10 

minutes. 

 CHAIRMAN BARTON. Thank you. I want--let me thank Ms. Baldwin 

before she leaves. She and Mr. Inslee and Mr. Stupak have been here the 

entire time and I think they need to be given accolades. Mr. Whitfield 

and I almost have to be here but they don’t, so we appreciate you all’s 

attendance. I want to thank these witnesses for waiting 5 hours to testify. 

That shows a little bit of fortitude on your part. 

 My first question goes to you, Dr. Karl. Talking about the peer 

review and the acceptance, if I were to ask Mr. Inslee and Mr. Stupak 

and Ms. Baldwin to review the work of this committee in this Congress 

and then turn around and ask Mr. Whitfield and Mr. Walden and Mr. 

Shimkus, I would probably get two radically different assessments. 

Same body of work but my friends on the Democrat side would view the 

accomplishments in all probability substantially different than my 

colleagues on the Republican side because both are biased in an open and 

honest way and have a different worldview on some issues, not on all 

issues. So it shouldn’t be surprising if the same people that Dr. Wegman 

calls a social network and are interacting all the time that they view 

positively the output, should it? 
249

 DR. KARL. Are you asking about whether or not the review process 

is skewed? 

 CHAIRMAN BARTON. No, I am just asking you to comment because 

I will stipulate that everybody in the climatology community, the 

environmental community, have got good faith and are trying to do what 

they think is right for the world. I am not--but there are biases on both 

sides, and one of Dr. Wegman’s criticisms, and Dr. McIntyre reinforces 

it, is that you are not really getting independent review, and there are 

cases, as Dr. Crowley pointed out, there may not be anybody that can be 

independent because they don’t understand it. If I want somebody to 

interview Albert Einstein’s work in the 1930s, there probably weren’t 

two or three people in the world that even knew what he was talking 

about, so you do get that, but what happened with Dr. Mann’s study in 

1998 was that it was accepted very quickly as kind of the gold standard 

and it was given a literary review, but it really wasn’t given an 

independent scientific statistical review. It was just accepted. And 

unless Dr. McIntyre is not being true, some of these other studies that 

have come out that Dr. Crowley referred to, he used the same data sets 

and the same modeling or something that is very close to it. So how can 

us poor mortals that have to make the policy decisions know what to 

believe when the so-called scientific community could be portrayed as 

scratching each other’s back? I mean, I am not trying to be mean about 

it. You know, I just am kind of puzzled. 

 DR. KARL. I mean, I can tell you the process that we use in IPCC. It 

may shed some light on it. In the IPCC report, each of the lead authors 

are asked to assess the published literature up until a certain time after 

which no more new material can be considered and what lead authors do 

is take a look at that material and try to write up their consistencies 

among what has been published, inconsistencies, what is available today 

compared to what was available during either the previous IPCC report 

or previous to that. Having done that, those writings then are subjected 

to international review. Anyone and everybody is open to review to 

report and the process takes place over several years. So there is ample 

time, ample review time-- 

 CHAIRMAN BARTON. But do they really review it? Again, I am not 

saying that your folks don’t make a good-faith effort, but it is just like 

my analogy. If I asked Mr. Whitfield, who is a subcommittee Chairman 

because I appointed him subcommittee Chairman as Chairman, if I say 

Ed, could you review my performance as chairman of the full committee, 

I bet he is going to give me a pretty high performance rating. Now, on 

the other hand, if I asked Mr. Inslee to review my performance as full 

committee Chairman, and I have consistently opposed his amendments 

and I have consistently made life difficult for him, which is not true but 
250

let us assume that it is true, he is not going to rate me the same. In all 

probability, Jay Inslee is going to be more independent and objective 

than Ed Whitfield, and they are both good people. But one of them is 

more dependent on me, interacts more, benefits more with that 

interaction than the other and it appears to me that what Dr. Wegman and 

Mr. McIntyre are saying is, it may be because there are just not enough 

experts, it may be for any number of reasons, but a very small set of 

people review each other’s work and lo and behold, they all come to the 

same conclusions. 

 Now, we didn’t put it into the record, but in 1975 we have the 

Newsweek story about the meteorologists all being unanimously in 

agreement that the world is in a world-cooling period and it has 

catastrophic consequences and there was unanimous agreement. It was 

la di la di da. Those were meteorologists. Now, that is 31 years ago. 

The world has changed. We are now worried about global warming but 

it the same thing. You know, I am not qualified to say whether the 

conclusions are right or wrong. I agree with what Dr. Wegman said and 

Dr. North said, that--I can’t conclusively say what is causing it. I can 

admit that the statistical record in the last 150 years that the temperature 

is going up, but I would like to see the scientific community self-regulate 

itself a little bit better so that when you have these statements like Dr. 

Mann made that the 1990s were the warmest period in 1,000 years and 

1998 is the warmest year in 1,000 years, that you can replicate that with 

statistically valid modeling technique that is open to the public and 

everybody takes their shot at. I think we have pretty conclusively proven 

today that that is not the case, at least in that study. That is not the case. 

So that is my question to you, what can the scientific community do to 

give us more certainty or more reliability that the conclusions of these 

studies are really based on fact and not on opinion. 

 DR. KARL. I suspect, and I don’t know for sure, but if you request 

the records from the IPCC Bureau, for example, you could--because it is 

public--you could get available the disciplines of the individuals who 

commented on that report and I note there is an IPCC report going on 

now, and that may be a way for this committee to try and see the breadth 

and scope of-- 

 CHAIRMAN BARTON. Well, are you willing to recommend that--one 

of the recommendations of Dr. Wegman is that the data be publicly 

available? Is that something that you would support? Because we have 

apparently had a real problem with Dr. Mann, getting his data and, it has 

been federally funded. I think it should be available, that anybody who 

has the scientific ability and the mathematical ability to study it, study it. 

Do you agree with that? 
251

 DR. KARL. Yes. Our Center actually houses the Paleoclimate World 

Data Center and we actually encourage researchers to archive their data, 

not the actual proxy itself like the tree ring or the ice core but the data 

from which they are derived. We are fairly successful in many instances, 

but I am sure there is a number of instances where we don’t have data 

simply because of its significant investment on both the PI’s time and-- 

 CHAIRMAN BARTON. And either Dr. North--I think Dr. North’s 

report, or it may have been Dr. Wegman’s, says there are only 30 of 

these data sets in existence right now, that there are a fairly limited 

number of data sets. So we are basing a lot of decisions on a fairly 

narrow band. 

 Let me ask you something, Mr. McIntyre. Since you had the 

gumption to criticize Dr. Mann, how have you been received in this 

community. Are people patting you on the back and inviting you to their 

Christmas party and saying right on, way to go, we really appreciate it, or 

are they kind of giving you the cold shoulder and ask why the hell you 

did what you did? 

 MR. MCINTYRE. I would say cold shoulder would be overstating the 

friendliness of it. I would say that I have been reviled and-- 

 CHAIRMAN BARTON. And so your skepticism for scientific truth has 

not been welcomed with open warms. Is that a fair statement? 

 MR. MCINTYRE. I would say it has been an uphill fight. Having said 

that one finds certain allies and certain moments of comfort. I mean, 

quite frankly I could understand why there would be some reluctance to 

take the claims seriously at the beginning. That is one of the reasons 

why I archived the source code and calculations so that people could 

replicate it. Aside from the fact that I think it is something that should be 

done anyway, but my position was if anybody thinks that my results are 

wrong, then I would like to know. I would like to be the first person to 

know rather than the last person to know, and--but I--for example, the 

University Corporation of Atmospheric Research put out a national press 

release saying that all our claims are unfounded. Sir John Houghton, cochair of IPCC, testified to a Senate committee that our claims were false. 

So while I would say not all of our claims have been acknowledged, 

some of them have. Both of these reports have certainly endorsed a 

finding on methodology that surprised people and so, I feel a little more 

comfortable now. Also, some people have been very generous and 

welcoming. Dr. von Storch has encouraged me both publicly and 

privately. 

 CHAIRMAN BARTON. Dr. Crowley, this might be my last question. 

You mentioned in your oral statement--I didn’t see it in your written 

statement but it may have been there--that there have been problems in 

the past with correlation of current temperature readings and their 
252

consequences with satellite readings and that those correlations are much 

better today. Is that true? Did I-- 

 DR. CROWLEY. Yes, that is true. 

 CHAIRMAN BARTON. Now, my understanding is that what changed 

is that we have gone back and reprogrammed the software on the 

satellites so that they will conform with the model predictions. Do you 

agree or disagree with that? 

 DR. CROWLEY. I completely disagree with that. 

 CHAIRMAN BARTON. Can you push your--I don’t know that your 

microphone is on. You said--I think you said-- 

 DR. CROWLEY. I disagree with you. It is not the case of trying to get 

it to conform to model predictions. In fact, it stuck out like sore thumb 

for 10 years. The climate community took it very seriously as a 

disagreement and pondered over it and there was eventually a 

comparison between two different groups of satellite analysts in which 

they found a programming error in one of the algorithms for reducing the 

data that gave the differences in the trends because this other group 

actually had gotten a bigger trend in the satellite data than the one that 

John Christy at University-- 

 CHAIRMAN BARTON. Do you think that that disagreement is worthy 

of being pursued by this subcommittee? 

 DR. CROWLEY. Well, what has happened is that the disagreement 

has diminished to the point where I am not sure it is worth the 

subcommittee’s effort to inquire. It has been found to be a programming 

error, and an innocent one but that happens when you are working with 

satellite or any other thing. It just took a long time-- 

 CHAIRMAN BARTON. Do you consider Dr. Mann’s methodology a 

programming error? If you were Dr. Mann and-- 

 DR. CROWLEY. No, because I don’t think he actually wrote--I don’t 

think his programs--when it is a programming error, it is like a coding 

error or something. I think that there is a methodological error, okay. 

There is a difference between, as you know, since you took 

programming, between the--you can program a methodology that could 

be wrong, okay. So I don’t think it was programming. I think it was a 

methodological error. 

 CHAIRMAN BARTON. Well, my time-- 

 DR. CROWLEY. Not a--yeah, a methodological. 

 CHAIRMAN BARTON. Thank you, Mr. Chairman. 

 MR. WHITFIELD. Mr. Inslee, you are recognized for 10 minutes. 

 MR. INSLEE. Thank you. I wanted to ask Mr. Karl about the 

conclusions, if I can find them here. In your testimony you talked about 

reviewing a variety of papers and you said of all the analysis, only one 

shows temperatures during medieval times higher than those of the early 
253

20th Century and none of the analyses show temperatures higher than the 

last few decades of the 20th Century and into the 21st Century. So I take 

it that means that none of the analyses that have been done have shown 

temperatures at any point higher than the last few decades and into this 

century. Is that an exhaustive review of the analyses or is there 

something you might have missed or is that pretty much a total review of 

the literature on this? 

 DR. KARL. There is always a danger one could have missed a report 

but none of the reports I looked at, which probably seven or eight reports 

using the approaches from as been discussed here. I think “bonehead” is 

a term and RPG and various terms have been given to these things, but I 

don’t think any of them show temperatures, except for one, that were as 

warm as what we saw in the mid part of the 20th Century, none of them 

as warm as the late part of the 20th Century and the early part of the 21st 

century, and in addition, I might add the error bars are frequently being 

discussed. If you look at the error bars, the wide error bars, the 95 

percent confidence error bars, it is even hard to find in those error bars in 

those reports to come up to the levels as high as we see in the last couple 

decades. 

 MR. INSLEE. So is it a fair synopsis here that today we have heard 

some criticism of one report that suggested that these are higher 

temperatures we are experiencing now than we have at any time in the 

last 1,000 years and multiple reports that have reached the conclusion 

that it is likely we are having higher temperatures right now than we did 

at any time in the last 1,000 years. Is that sort of a fair statement of what 

we are hearing? 

 DR. KARL. I think so, and again, the word “likely” you know, I point 

out, we use the word “likely” with better than two to one odds and so 

with that kind of a caveat, I feel quite comfortable in saying that. 

 MR. INSLEE. Well, the way I look at this, just so you know, is that 

you have got about six studies showing that gravity exists and you have 

got one study questioning the statistical mechanisms used in one of those 

six studies, and I sort of conclude that both gravity and global warming 

due to human activity exist, and that is just how I look at it. I want to 

refer--you also concluded, “These analyses indicated that the later half of 

the 20th Century is certainly warmer than any time during the past several 

hundred years, parentheses, based on the length of the borehole and 

glacial length proxies, paren, and the past 1,200 years based on isotopic 

ice core records.” So you indicated that these are warmer during the past 

several years and you say based on the length of the borehole and glacial 

length proxies. What are those two proxies? 

 DR. KARL. Those are proxies that are completely independent of the 

tree ring analysis which is heavily used in some of these multi-proxy 
254

reconstructions. But the borehole measurements are--there is probably 

about--I think the academy actually gave a number of about 679 different 

boreholes where the conduction of heat from the atmosphere is 

constantly conducting into the Earth’s surface and you can go back in 

time to try and deduce what the actual temperatures were in the lower 

parts of the atmosphere. Now, you have to be careful which boreholes 

you look at but nonetheless, with current methods, you can go back to 

about 400 or more years. That was an important piece of evidence that 

when we did the IPCC in 2001 we intercompared those borehole 

measurements with the Mann record, for example. 

 MR. INSLEE. So as I take it then, we have got totally independent 

results independent from the Mann analysis that is consistent with the 

conclusion that it is likely that we are in warmer temperatures now than 

we have been in the last several hundred years. Now, you made 

reference to glacial length proxies. What are those? 

 DR. KARL. Now, the glacial length proxies, this is where a model 

was used to try and look at the ablation of glaciers across primarily the 

Northern Hemisphere and a model has been shown to be able to 

reproduce approximately the temperatures that would be needed to cause 

those glaciers to melt. Again, you have to be careful about what glaciers 

you select. Some of them are more sensitive to precipitation but 

nonetheless another independent method, and again, it shows that the 

later part of the 20th Century is warmer than anything we have seen in the 

last several hundred years. 

 MR. INSLEE. Now, you also reported that these analyses indicated 

that these temperatures we are now experiencing are warmer than in the 

past 1,200 years based on isotopic core records. Are the isotopic core 

records independent of the Mann research and could you describe what 

they are? 

 DR. KARL. Yes. They are independent as well. The difference is, 

they are far fewer in terms of geographic coverage. So what you are 

actually looking at here is the isotopic decay within these records, the 

same kind of records that are looked at for the air bubbles that are 

trapped in the ice. Now you try to relate through isotopic decay to 

temperatures and there are some relationships that have been developed 

and again you see some significant warming in the latter part of the 20th

Century compared to what we saw earlier. 

 MR. INSLEE. So we have multiple independent scientifically sound 

measures to conclude these are the likeliest warmest temperatures we 

have had in 1,000 years independent of the Mann report. Is that correct? 

 DR. KARL. That is correct. 

 MR. INSLEE. Dr. Crowley, you talked about something that I had 

heard and I appreciate you talking about it, about amplitude, about the 
255

effect of how much amplitude there is in the system, how sensitive the 

system it is to CO2 forcing, and I think this is interesting because 

basically the Wall Street Journal editorial staff has done everything they 

can to suggest this is not a problem and they have attacked the Mann 

research effectively saying that, but is it fair to say that actually if one 

would want to debunk the idea of global warming, if one would want to 

say we shouldn’t worry about global warming, if one would want to say 

that we should really just continue on our path of putting megatons of 

CO2 in the air without change, if one really wanted to argue that, one 

would really want to argue that Mann was right because Mann had a 

conclusion that there was less effect on temperature by CO2 changes than 

some of the other studies. Is that right? 

 DR. CROWLEY. That is true. Another way of putting it is that those 

who love to hate Mann should learn to hate to love him. 

 MR. INSLEE. Well, that will take us about 8 minutes to figure out up 

here on this panel. But could you explain why that is? I just heard this 

yesterday for the first time. It is an intriguing thought, that this could be 

a reversal of approaches here, but why is it important to know how much 

CO2 can affect temperature and what does the Mann research indicate 

versus other research? 

 DR. CROWLEY. Well, it is like pushing on a string. Jerry North 

explained this to me years ago. Suppose you have two strings, one that is 

very thick, coiled spring, and then another one that is very thin and weak. 

You push on the thick coiled spring, it is not going to move very much 

whereas one that is very flexible is going to move a lot, and that is really 

like pushing is like the climate forcing the responses to climate system, 

so if you have a system that has a very low sensitivity, it is not going to 

respond much, like the thickly coiled spring. You have one that is less 

thickly coiled, it is going to respond more and you are going to get 

bigger temperature changes and that is the thing we worry about, is 

whether the temperature change is being large, and the study came out 

recently in Nature where we tried to quantify that and that at least with 

respect to the paleoclimate records and showed objectively what I was 

saying-- 

 MR. INSLEE. So if Mann was wrong, this problem that we are going 

to be at in 2100 when CO2 levels are twice the rate of pre-industrial 

times-- 

 DR. CROWLEY. We are going to have larger temperature variability. 

 MR. INSLEE. So if Mann is wrong, that means we are going to have 

greater increases in temperature once this CO2 levels skyrocket like this 

and even some of the other researchers have predicted. Is that the 

situation? 

 DR. CROWLEY. Right. 
256

 MR. INSLEE. That will news to the Wall Street Journal editorial 

board. 

 DR. CROWLEY. Sure. 

 MR. INSLEE. Thank you. 

 MR. WHITFIELD. Thank you, Mr. Inslee. Dr. von Storch, in your 

presentation you made the comment that parts of climate change science, 

in particular paleoclimatic reconstructions have suffered from 

gatekeeping and incestuous usage of reviewers and then you talked about 

they have a bias toward interesting results, and we have a lot of 

testimony today about the Wall Street Journal and the oil industry and 

the coal industry love to debunk all of this science about global warming, 

which may be true, but I was interestingly reading an article the other 

day about a gentleman named Chris Landsea, who was on the IPCC 

panel and was an expert in hurricanes. And we heard testimony today in 

some of the opening statements that global warming is causing more 

hurricanes, stronger hurricanes and it is a serious problem. Henry 

Waxman is the one that made that comment and there was another 

person that made that comment. And Chris Landsea was asked by a 

gentleman named Dr. Kevin Trenberth to provide the write-up for the 

AR4 assessment, the fourth assessment report of the IPCC. He was 

asked to do the write-up for the Atlantic Hurricanes, and soon after he 

was asked, Dr. Trinberth went to Harvard University and participated in 

a program entitled on the topic: “experts to warn global warming likely 

to continue spurring more outbreaks and intense hurricane activity.” 

And there was big press about it and there were all sorts of articles 

written about it. And Landsea was so upset about this as they were just 

getting ready to do this assessment that he submitted his resignation. 

And he said, “It is beyond me why my colleagues would utilize the 

media to push an unsupported agenda that recenty hurricane activity has 

been due to global warming. Given Dr. Trenberth’s role as the IPCC’s 

lead author responsible for preparing the text on hurricanes, his public 

statements are so far outside of any scientific understanding led me to 

concern that it would be very difficult for the IPCC process to proceed 

objectively with regards to the assessment on hurricane activity.” Now, 

we are all human beings, we make a lot of mistakes. We are biased. We 

do this, we do that. But is that something that happens in the IPCC 

frequently or infrequently or do you have any comment about it? 

 DR. VON STORCH. Only through the media, and I had the impression 

that this was not very helpful, what has happened there, but I don’t know 

the details, and this would be an example where I would ask some social 

scientists to really go after this, what really has happened here. I think it 

would be worth doing it. But when we speak about this storm business, I 

would like to tell a little story, namely in the early 1990s we had the 
257

press in northern Europe full of messages that we would have more 

storms, and these storms would be proof or would be a result of global 

warming going on. And you have to know that when people think about 

climate change, anthropogenic climate change in the past, it always is 

associated with more storms. So if you read about the cooling in the 

1970s, what the response would be, it was cooler and more stormy, so it 

seems that it is part of our cultural heritage that whenever we think we 

change climate to the worse, then we have more storms. Later on it 

turned out that we actually have less storms now in northern Europe. 

And if we believe our climate change models, and I do believe them and 

I am sincerely convinced that we see global warming happening. If we 

believe these models then we should have an intensification of storms in 

our part of the world with stronger wind speeds of the order of 10 percent 

of the end of the century, that would be a signal which cannot be 

detected. While if you go into the details, then you find out that several 

aspects are rather similar to the ongoing hurricane debate, namely that 

good data exists only for a short time. Satellites are flying only since the 

1970s or so, and observing this, and you have decades with strong 

activity and decades with less strong activity. It is the same with the 

storms in our part of the world. And so I would say in this case one 

should be very careful in making definite conclusions about that. And if 

we believe our models, and I am not sure if we should believe in this 

respect our models, then we also should have a signal which is much 

weaker now, hardly detectable at this time. So in this case with the 

hurricanes, I would advise to wait a little bit before definite conclusions 

are drawn. And this would be an example that somehow this 

preconception that storms are getting worse when climate is changing is 

somehow controlling what we think. 

 MR. WHITFIELD. Mr. McIntyre, I know that you and Mr. McKitrick 

were the ones that first started looking at the Mann study or report. How 

did that come about? Was this just an area of interest that you have had, 

or what? 

 MR. MCINTYRE. Well, that is actually a fairly long story but I was 

just--at that time I was just a private citizen. The study was being--we 

were told in Canada that 1998 was the warmest year of the millennium. I 

have worked in the mineral exploration business for many years. I deal 

with geologists who were unimpressed by that statement and I just 

wondered one day how they knew that. When I looked at the IPCC 

report as somebody that is in the mineral exploration business, which is a 

very promotional business, I was struck at how promotional many of the 

statements were and particular how promotional the hockey stick graph 

was. I thought actually sort of in a professional way, I thought it was 

well designed, well presented. It was there to convey a message but I 
258

certainly felt like I was being sold when I saw that. Some months later, 

business was slow. I thought I would be interested in looking at the data. 

I assumed there was some kind of due diligence package like you would 

see in a business thing that they had prepared for the IPCC auditors. At 

that time I had no idea that such things didn’t typically exist in the 

academic community so I e-mailed Dr. Mann out of the blue and asked 

him where the data was and just for the location of the data of this which 

I assumed to be part of the due diligence package and he said he had 

forgotten where the data was. So I was astonished as there had been so 

much publicity. He said he would have an associate locate it for me. 

The associate said that it wasn’t in any one place, but he would get it 

together for me so I thought that was nice of him but just, it seemed an 

odd situation and I just thought well, nobody has ever looked at this and 

if nobody has ever looked at it, well, I will do it, so I didn’t expect to be 

the center of an academic debate or any furor, but when I looked at it, I 

started finding problems and here we are today. 

 MR. WHITFIELD. And I would ask Dr. Crowley and Mr. McIntyre or 

anybody else that wants to comment: the Wall Street Journal that has 

been referred to many times today says that Dr. Mann’s methodology 

could produce hockey sticks from random trendless data. Is that a 

correct statement or is that incorrect statement? 

 MR. MCINTYRE. Well, let me answer that. That is true, and that is 

the one specific item that was verified by both panels, and both the NAS 

panel and the Wegman report specifically confirm that his methodology 

would produce a hockey stick from random data. 

 MR. WHITFIELD. Okay. Dr. Crowley, did you want to comment on 

that? 

 DR. CROWLEY. I am not an expert in statistics so I just have to defer 

from that answer. All I can say is that when we took a completely 

different approach with the very simple averaging, we got an answer that 

was pretty similar. 

 MR. WHITFIELD. Dr. von Storch? 

 DR. VON STORCH. I think I have a bit of reputation in studies of 

climatology as I am the coauthor of I would say the leading statistics 

book in that field. So first of all, what Mr. McIntyre is saying is correct. 

You can get that. But this requires that you have no other significant 

signals in the field, in particular no correlation in space, and this is not 

the case in climatological variables and so I would say even if it is 

entirely true what he said and I would include it in the next version of 

this book we have written. I would say in very many practical situations 

it would not show up. 

 MR. WHITFIELD. Thank you. My time has expired. 

 CHAIRMAN BARTON. Has Mr. Stupak not gone yet? 
259

 MR. STUPAK. No. 

 CHAIRMAN BARTON. Well, then let us get Mr. Stupak. He has 

waited patiently all afternoon. 

 MR. STUPAK. Dr. Karl, if I may, Dr. von Storch says that the 

reputation of the IPCC has increased to very high levels in the past years, 

that most lead authors are honest brokers of the work they review and 

that perhaps in such a complex and large field as the IPCC is addressing, 

it may not be possible to have lead authors who have not contributed to 

the field. But then Dr. von Storch concludes that an independent review 

by the IPCC is not possible under the current system. How would you 

respond to that? 

 DR. KARL. Again, no human-conceived system is perfect. I don’t 

know how you might improve it in terms of the way it operates today. 

The peer review process really is driven by others’ availability to 

comment and the IPCC documents are open for everyone from every 

discipline to comment on including the governments of the world. I 

think one of the issues that has been discussed in the hearing today is one 

that is typical of science where you can publish something but sometimes 

it takes a period of years to try and come up with a different analysis, 

technique, or to explore the decisions that are made in a particular 

analysis technique. The IPCC process right now is over a period of 2 

years. I don’t see how you could actually open up a process more and I 

don’t see how you could actually have a process whereby every piece of 

information is going to be evaluated in terms of a new analysis, and that 

is the reason it is done every 5 or 6 years to update, see if there are 

differences. So, for example, I am sure all the work being done since the 

2001 IPCC assessment and the next one that is coming out next year will 

be included and assessed. 

 MR. STUPAK. Well, the 2001 IPCC report really referenced other 

studies other than the 1998 and 1999 Mann hockey stick study, right? 

 DR. KARL. Yes. In fact, as I said, it would have been--I hate to use 

the words “very unlikely” because those are like the words that are used 

in the IPCC but I don’t think IPCC would have actually made a 

statement about the 1990s had it only been based on one article. If it was 

just the Mann work, I just don’t think we would have had the confidence 

to say anything. 

 MR. STUPAK. I am looking at your 2001 report here, and I am on 

page--and in there it says new analysis of proxy data for the Northern 

Hemisphere indicate that the increase in temperature in the 20th Century 

is likely to have been the largest of any century during the past 1,000 

years. It is also likely that in the Northern Hemisphere the 1990s was the 

warmest decade and 1998 was the warmest year. That was the 
260

conclusion of 2001 and that is based upon more than just the Mann 

study. Isn’t that correct? 

 DR. KARL. That is correct. 

 MR. STUPAK. Okay. You used the word “likely.” I know today 

especially when the Chairman asked questions it was like absolute based 

upon the Mann study and that is not the case, it based upon--your 2001 

report takes some other things other than the Mann hockey stick study, 

right? 

 DR. KARL. That is correct. 

 MR. STUPAK. What is the significance of the word “likely”? Not 

working in your field, I may have a different view of “likely” but you use 

it twice. Can you give any further explanation of that? 

 DR. KARL. What we tried to do is clarify what we meant by the 

word “likely” because it can be taken all different ways because it is used 

frequently in the literature. We define “likely” as a probability of the 

statement being true between 66 and 90 percent of the time. That means 

slightly better than two to one odds at the low end, and at the high end 

close to nine to one odds. 

 MR. STUPAK. You have been here all day. Is there anything you 

have heard today which would make you change your mind about the 

conclusions of the 2001 IPCC report? 

 DR. KARL. No. If you ask me to give qualifications about the 

findings in the 2001 report with the same caveat in terms of defining 

likelihood, I personally would not change anything. 

 MR. STUPAK. And going further in this, your 2001 report, the IPCC 

report, they talk about the Jones et al., about having the warmest year of 

the past millennium in the Northern Hemisphere, Jones et al. in 1998 

came to a similar conclusion from largely independent data and entirely 

independent methodology. Crowley and Lowery in 2000 reach a similar 

conclusion. Borehole data, Pollick, et cetera, in 1998 independently 

support this conclusion for the past 500 years. So there is plenty of other 

things to base that conclusion upon and not just the Mann-- 

 DR. KARL. That is correct. 

 MR. STUPAK. And somewhere today someone said something like 

there is over 900 reports or studies on global warming. Is that correct? 

 DR. KARL. I am sure there is even more than that. I think that was a 

random sample, so there is probably in the tens of thousands. 

 MR. STUPAK. Okay. Thank you. Dr. Crowley, if I may, when I was 

asking Dr. Wegman about this chart here, which was showing the warm 

age there in around 1300 or so, I think he called it the cartoon graph, was 

his word. Is that based on any set of data or anything or-- 

 DR. CROWLEY. That is pretty much a cartoon graph actually. This is 

really in the first round of IPCC. Nobody ever felt there was a need to--
261

had thought of whether there should be a need to have a quantitative 

estimate of climate for the last 1,000 years. They wanted to try to 

provide a perspective and they didn’t realize they didn’t have one and 

they basically talked to some people and there was a lot of anecdotal 

evidence for medieval warm period, that people said it was warmer than 

the present roughly during these years, you know, so it was really pretty 

much of a guesstimate, and it was only when we started looking at a 

number of sites that had a very good chronology so we knew where they 

were in time and that we realized that the timing of the warmth was not 

the same in different regions, that that peak collapsed. 

 MR. STUPAK. So it is not fair to compare this cartoon graph with Dr. 

Mann’s hockey stick? 

 DR. CROWLEY. No, I don’t think that was intention of Dr. Wegman. 

I think he was just-- 

 MR. STUPAK. No, I guess the Wall Street Journal used it more as 

one of those. You said the Wegman report should not be a legitimate 

assessment of the science of global warming or as a guide to policy 

modification. Can you elaborate a little bit on that? 

 DR. CROWLEY. Well, I felt that--again, I have to--I can’t remember 

exactly where--do you have it listed where I said that so I can-- 

 MR. STUPAK. Let me find it here. 

 DR. CROWLEY. Last page. So what I said is I disagree with many in 

the fact sheet and also in the report itself. It is not like I disagreed with 

what he was saying about his analysis of the Mann et al. record there but 

some of the recommendations that he was making I think that I felt there 

was a need---I just disagreed with him and so I was concerned that in 

terms of recommending any changes. I am not saying that interaction 

with statisticians is bad. I strongly favor very enhanced interaction but a 

lot of that is already happening. 

 MR. STUPAK. Mr. McIntyre, you are not a paleoclimatologist, right? 

 MR. MCINTYRE. No. 

 MR. STUPAK. And you are not a statistician? 

 MR. MCINTYRE. I studied mathematics and statistics at university. 

 MR. STUPAK. So are you a statistician then? 

 MR. MCINTYRE. I have not practiced as a statistician, but this is 

what I have been doing for the last few years. I think that-- 

 MR. STUPAK. You have been doing statistics the last 2 years then? 

 MR. MCINTYRE. I have been working at statistical analysis of multiproxy studies for the last 3 years. 

 MR. STUPAK. Three years. Okay. 

 MR. MCINTYRE. I note that my findings have been endorsed by both 

the NAS panel and the Wegman report. 
262

 MR. STUPAK. In this--again, reading the Wall Street Journal

editorial. I am not sure how accurate this is but it say you and Mr. 

McKitrick published an article in a peer review journal. What discipline 

did the peer review? 

 MR. MCINTYRE. We have published articles in two journals, 

Geophysical Research Letters, which is the same journal that published 

the original Mann article, and Energy and Environment. 

 MR. STUPAK. Let me ask Dr. Crowley if I can. Both you and Dr. 

Karl and the National Research Council have stated that the Mann study 

was not the most influential work in the IPCC 2001 report. You testified 

that the papers that made the biggest differences were ones that said the 

influence of greenhouse gases had to be used to reconcile the data and 

the models and the most compelling driver was the fact that global 

temperatures kept going up and glacier melt was increasing. Why then is 

there so much emphasis on the Mann report? 

 DR. CROWLEY. Well, there has been this discussion before about it 

being used as an icon, okay, and people say well, if it is not right, then is 

IPCC wrong, so there has then been that connection drawn. So I think 

for rightly or wrongly, I am not sure if IPCC is the only one responsible 

for broad--for using that as an icon but it has effectively become one and 

I think that is really the--what the--I guess the argument settles down to. 

 MR. STUPAK. Thank you. I guess my time is up. We have got 3 

minutes to go vote. 

 MR. WHITFIELD. I want to thank all of you on the panel, one, for 

being here, two, for being so patient, and three, for what you do and the 

contributions that all of you are making. We may or may not have some 

more hearings on this. I know we do have an invitation out to Dr. Mann 

and we will see if he is going to come or not. But I want to ask 

unanimous consent that the document binder be submitted into the record 

of this hearing, unanimous consent that the document in Newsweek that 

Chairman Barton referred to about the cooling world be entered into the 

record and then I would like to keep the record open for 30 days for any 

follow-up questions we may have. So without objection, so ordered and 

this hearing is concluded, and thank you all again for being with us. We 

genuinely appreciate it. 

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 [Whereupon, at 4:12 p.m., the subcommittee was adjourned.] 
586

RESPONSE FOR THE RECORD OF DR. GERALD R. NORTH, DEPARTMENT OF ATMOSPHERIC 

SCIENCES, TEXAS A&M UNIVERSITY

The Honorable Ed Whitfield

1. As you chaired the National Research Council panel that recently issued the report on 

millennial temperature reconstructions: 

a. Where in the report did the panel describe "plausible" as suggesting roughly a 

2/3rds probability of being correct? 

In the report we shunned the use of numerical probability assessments in favor of 

descriptive statements (e.g., "high confidence") and statements that describe our relative 

confidence in different conclusions (e.g. "less confidence"). I may have mistakenly 

mentioned the "two to one odds" figure in the oral press release of the report, and it may 

also have appeared in some press accounts, but it does not appear in the report, and I 

avoided using it in my sworn testimony. 

b. In the report, did the panel attach probability estimates to the term "plausible"? 

No. The committee avoided numerical probability estimates because many of the 

uncertainties associated with reconstructing surface temperatures are not purely 

statistical in nature, but rather arise from physical factors associated with each proxy 

that are simply unquantifiable at this time. In our view it is not possible to quantify all of 

the inherent uncertainties associated with reconstructing surface temperatures from 

proxy data, which in turn precludes assigning numerical probabilities to statements 

regarding the unique nature of recent warmth. 

c. Why did the panel choose to use the term "plausible," as opposed for example to 

terms such as "likely," to describe confidence in millennial temperature 

reconstructions? 

In the IPCC reports, the term "likely" is used to indicate an estimated probability of 

between 66% and 90%, i.e. greater than two-thirds odds but less than nine-in-ten 

chances. We avoided numerical estimates such as these because we did not want to 

imply that we had performed a rigorous probability assessment. Instead, we tried to 

express our collective confidence in different conclusions using descriptive language. 

2. When considering the panel's findings that it is "plausible" that recent decades were the 

warmest in a millennium, is that correct to interpret that to mean the panel's consensus 

view was that plausible means roughly a 2/3rds probability of being correct, as was 

suggested in news reports following the press conference releasing the report? 

Our working definition of "plausible" was that the assertion is reasonable, or in other 

words there is not a convincing argument to refute the assertion. We used this term to 

describe our assessment of the statement that “the last few decades of the 20th century 

were warmer than any comparable period over the last millennium" because none of the 

available evidence to date contradicts this assertion. In our view it is not currently 

possible to perform a quantitative evaluation of recent warmth relative to the past 1,000 

years that includes all of the inherent uncertainties associated with reconstructing 

surface temperatures from proxy data. This precludes stronger statements of confidence, 

but it does not mean that the assertion is false. In fact, all of the large-scale surface 
587

temperature reconstructions that we examined support the assertion that global-mean 

temperatures during the last few decades of the 20th century were unprecedented over at 

least the past 1,000 years, and a larger fraction of geographically diverse proxy records 

experienced exceptional warmth during the late 20th century than during any other 

extended period from 900 A.D. onward. 

3. Did the panel perform its own, in-depth technical analysis of the methods and 

procedures-- such as checking the underlying data sets or attempting to replicate the 

findings – used in the various temperature reconstruction articles and presentations it 

considered in formulating its report? 

Our committee relied on the published, refereed scientific literature to reach its 

conclusions. We did not attempt to replicate the work of any previous author, with the 

lone exception of a simple computer program (reproduced in Appendix B of our report) 

that was used to illustrate an interesting artifact of the principal components 

methodology first noted by McIntyre and McKitrick. When evaluating the results of 

different studies, we placed higher confidence in those results that were reproduced in 

several different studies--for instance a number of independent lines of evidence indicate 

that the late 20th century warmth was unprecedented in at least the last 400 years, giving 

us high confidence in this conclusion. Less confidence can be placed in conclusions 

regarding large-scale surface temperatures prior to about 1600 A.D. because there are 

simply fewer independent lines of evidence to consider, although the evidence that does 

exist indicates that the late 20th century warmth is unprecedented for at least the last 

1,000 years. 

4. The NRC panel made specific reference to ice borehole studies in Greenland by DahlJensen, which suggest warmer temperatures in that region during the Medieval Warm 

Period than today. Please explain the value of regional temperature measurements such as 

this for understanding the potential effects of recent warming trends? 

There are two main reasons for using large-scale averages rather than individual 

regional measurements to evaluate global environmental changes: 1) Random 

measurement errors and climate fluctuations tend to cancel out when spatial averages 

are performed, allowing researchers to obtain a more reliable estimate than is possible 

for a local or a regional average; 2) The greenhouse effect operates at the global scale, 

hence large-scale averages are the best way to evaluate the response of the climate to 

increasing greenhouse gas concentrations. Current climate models also are better at 

computing large-scale averages than regional-scale values. 

Of course in order to detect large-scale climate anomalies, either in the modern 

temperature record or in proxy-based temperature reconstructions, it helps to have a 

large network of high quality measurements for geographically-diverse regions. The 

main reason that we have high confidence in the temperature increase over the past 100 

years and in the statement that temperatures are warmer now than at any other time over 

the last 400 years is because we have a sufficiently large number of well-characterized 

local measurements to calculate a reliable large-scale average. Several proxies 

(including historical and archeological evidence as well as quantitative temperature 

estimates from ice cores and boreholes) indicate that the area around Greenland was 

warmer between about 1000 and 1200 A.D. than it is today. There is also evidence for 

warm temperatures during medieval times from other regions of the world. However, 

studies suggest that these warm anomalies appear to have occurred at different times at 
588

different places rather than being globally synchronous, and also appear to have been 

offset by cold anomalies in other regions. The few large-scale surface temperature 

reconstructions that extend back far enough to rigorously compare large-scale medieval 

temperatures to modern warmth suggest that the medieval period was, at most, 

comparable in warmth to the first half of the 20th century. However, as noted above in 

response to question (4), it is difficult to quantify the full uncertainty associated with 

estimates of surface temperature prior to about 1600 A.D. 

The Honorable Bart Stupak

1. In the study performed by a special committee of the National Academy of Sciences 

(NAS) on surface temperature reconstructions over the past 2,000 years, it was stated 

that, for the time prior to 1600 A.D., scientists are less certain about the actual average 

northern hemispheric surface temperatures. The Medieval Warm Period (MWP) occurred 

prior to 1600. How certain are climatologists that there was a globally or even 

hemispherically MWP that was warmer than the past several decades? 

Indeed, the paucity of proxy data for periods prior to about 1600 A.D., especially in the 

tropics and the Southern Hemisphere, limits our confidence in statements regarding the 

global mean temperature of the past few decades compared to medieval times. Several 

proxies indicate that the area around Greenland was warmer between about 1000 and 

1200 A.D. than it is today. There is also evidence for warm temperatures during 

medieval times from other regions of the world. However, studies suggest that these 

warm anomalies appear to have occurred at different times at different places rather 

than being hemispherically or globally synchronous, and also appear to have been offset 

by cold anomalies in other regions. Although it is difficult to quantify the full uncertainty 

associated with estimates of surface temperature prior to about 1600 A.D., all of the 

large-scale surface temperature reconstructions that we examined support the assertion 

that global-mean temperatures during the last few decades of the 20th century were 

unprecedented over at least the past 1,000 years, and a larger fraction of geographically 

diverse proxy records experienced exceptional warmth during the late 20th century than 

during any other extended period from 900 A.D. onward. Hence we find it plausible (or 

in other words, no evidence exists to refute the claim) that “the last few decades of the 

20th century were warmer than any comparable period over the last millennium." This 

statement can be more strongly applied to the Northern Hemisphere than to the globe 

because there is very little proxy data from the Southern Hemisphere before about 1600 

A.D. 

2. The 1990 Intergovernmental Panel on Climate Change (IPCC) Report contains a 

"schematic diagram" that shows temperature changes for 900 A.D. through 1975, but 

does not give specific temperatures. The text of the report notes, "it is still not clear 

whether all the fluctuations indicated were truly global." Am I correct in my 

understanding that this schematic diagram is not a graph of specific data points consisting 

of global temperature for particular years or time periods? Am I also correct that the 

scientific consensus at the time was that there was significant uncertainty about whether 

the diagram accurately portrayed the global temperature profile over the last 1,000 years? 

Yes, the schematic diagram that appeared in the 1990 IPCC Report was simply a 

qualitative depiction of how scientists thought that large-scale temperatures may have 

evolved from 900 A.D. to about 1975. There was very little proxy data available at that 

time, and the data that did exist tended to be concentrated in just a few geographical 
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regions, such as Greenland. The lack of a temperature scale and supporting 

documentation strongly suggests that the diagram was not based on a quantitative 

analysis, and also implies that there was considerable uncertainty about the magnitude 

and timing of the indicated fluctuations. As stated in our report, there is still 

considerable uncertainty about the exact timing and magnitude of past temperature 

fluctuations, especially prior to about 1600 A.D., but our knowledge has advanced 

considerably since 1990. Figure S-1 from our report illustrates the current state of the 

science in large-scale surface temperature reconstructions for the last 1,000 years. 

3. What level of certainty is there that the temperature ranges for the period of 900 

through 1975 A.D. schematically displayed in the 1990 IPCC report are accurate? Prior 

to Dr. Mann's work, had anyone attempted to attach a level of certainty to the data 

relating to surface temperature reconstruction? 

There were no uncertainty assessments attached to the 1990 IPCC diagram. As 

discussed in response to question (2) above, this diagram was simply a qualitative 

depiction of how scientists thought that large-scale temperatures may have evolved from 

900 A.D. to about 1975. The papers by Dr. Mann and his colleagues in 1998 and 1999 

were, to my knowledge, the first attempts to assign statistical error bars to a large-scale 

surface temperature reconstruction. As noted in our report, these error bars provide an 

indication of how well the reconstructed temperatures match observations during the 

"calibration period," but they do not represent all of uncertainties inherent in 

reconstructing surface temperature from proxy data. The actual uncertainties in the 

reconstruction would be somewhat larger, and difficult to quantify. 

4. Mr. McIntyre has testified that the NAS report stated that the bristlecone pine proxy 

used by Dr. Mann in his original work should not have been used. Was that the 

conclusion of the panel? Please describe the conclusion and provide citations. 

Let me quote directly from page 50 of the prepublication version of our report: 

The possibility that increasing tree ring widths in modern times might be 

driven by increasing atmospheric carbon dioxide (CO2) concentrations, rather 

than increasing temperatures, was first proposed by LaMarche et al. (1984) 

for bristlecone pines (Pinus longaeva) in the White Mountains of California. 

In old age, these trees can assume a “stripbark” form, characterized by a 

band of trunk that remains alive and continues to grow after the rest of the 

stem has died. Such trees are sensitive to higher atmospheric CO2

concentrations (Graybill and Idso 1993), possibly because of greater wateruse efficiency (Knapp et al. 2001, Bunn et al. 2003) or different carbon 

partitioning among tree parts (Tang et al. 1999). Support for a direct CO2

influence on tree ring records extracted from “full-bark” trees is less 

conclusive. Increasing mean ring width was reported for Pinus cembra from 

the central Alps growing well below treeline (Nicolussi et al. 1995). Free-Air 

CO2 Enrichment (FACE) data for conifer plantations in the Duke Forest 

(Hamilton et al. 2002) and at the alpine treeline (Hättenschwiler et al. 2002) 

also showed increased tree growth after exposure to atmospheric CO2

concentrations about 50 percent greater than present. On the other hand, no 

convincing evidence for such effect was found in conifer tree ring records from 

the Sierra Nevada in California (Graumlich 1991) or the Rocky Mountains in 

Colorado (Kienast and Luxmoore 1988). Further evidence comes from a 

recent review of data for mature trees in four climatic zones, which concluded 
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that pine growth at treeline is limited by factors other than carbon (Körner 

2003). While ‘strip-bark’ samples should be avoided for temperature 

reconstructions, attention should also be paid to the confounding effects of 

anthropogenic nitrogen deposition (Vitousek et al. 1997), since the nutrient 

conditions of the soil determine wood growth response to increased 

atmospheric CO2 (Kostiainen et al. 2004). However, in forest areas below 

treeline where modern nitrogen input could be expected to influence 

dendroclimatic records, such as Scotland (Hughes et al. 1984) and Maine 

(Conkey 1986), the relationship between temperature and tree ring parameters 

was stable over time. 

 

In summary, it appears that there is a carbon dioxide fertilization effect in some trees, but 

not in all the places where the samples used in the Mann et al studies were taken. Also 

note that this section of the report discusses the calibration of tree-ring records since 

atmospheric carbon dioxide levels started to increase around 150 years ago. Hence, in 

context, what the clause "strip-bark samples should be avoided for temperature 

reconstructions" was intended to convey is that strip-bark samples from the mid-19th 

century to the present are very difficult to calibrate against instrumental records of 

temperature, and the easiest solution is therefore not to use them. However, strip-bark 

data are considered suspect only after the modern increase in atmospheric carbon 

dioxide concentrations. This is why other studies that rely on strip-bark pine records only 

use them to infer past temperatures prior to 1850 (e.g., Biondi et al. 1999). This 

reference, and all of those cited in the above quote, can be found in the reference section 

of our report. 

5. The recent work by Wahl & Amman redid Dr. Mann's original work, but recentered it 

as Mr. Mcintyre suggested. Wahl and Amman's work, however, resulted in the same 

"hockey stick" distribution. Please explain why this work was not fully considered and 

evaluated in the NAS study. 

We did consider the Wahl and Ammann paper that was accepted for publication in the 

journal Climatic Change on February 28th of this year, in which they found that 

decentering has only a relatively minor influence on the shape of the final reconstruction. 

This paper was one of many that influenced our evaluation of the Mann et al. (1998, 

1999) papers and the robustness of surface temperature reconstructions in general. The 

effects of decentering are described explicitly in Chapter 9 of our report, and our 

conclusions regarding how decentering influences surface temperature reconstructions 

can be found in the following excerpt from page 106 of the prepublication version of the 

report: 

As part of their statistical methods, Mann et al. used a type of principal 

component analysis that tends to bias the shape of the reconstructions. A 

description of this effect is given in Chapter 9. In practice, this method, 

though not recommended, does not appear to unduly influence reconstructions 

of hemispheric mean temperature; reconstructions performed without using 

principal component analysis are qualitatively similar to the original curves 

presented by Mann et al. (Crowley and Lowry 2000, Huybers 2005, D’Arrigo 

et al. 2006, Hegerl et al. 2006, Wahl and Ammann in press). 

Drs. Wahl and Ammann (along with Dr. Ritson) also authored a paper that appeared in 

Science magazine on April 28th of this year alongside a response written by Drs. von 

Storch and Zorita. These papers were under embargo during our deliberations, and thus 
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we were not able to consider them during our deliberations, although we did note (on 

page 105) that "the...debate in the scientific literature continues even as this report goes 

to press (von Storch et al. 2006, Wahl et al. 2006).” These papers address a separate 

statistical issue than the one discussed above, in particular the issue of detrending the 

data prior to performing principal components analysis. My personal impression of 

these two papers is that the quote cited above still applies, that is, none of the statistical 

criticisms that have been raised by various authors unduly influence the shape of the final 

reconstruction. This is attested to by the fact that reconstructions performed without 

using principal components yield similar results. 

6. In the hearing, Dr. Wegman challenged "anybody" to tell him the difference between 

72 and 74 degrees Fahrenheit. Please describe the climatic and other changes that can 

result from a global increase in temperature of 2 degrees Fahrenheit. 

As context, let me first point out that the difference in global-mean temperature between 

today and the height of the last Ice Age, when New York and Seattle were covered with 

over a kilometer of ice, is estimated to be only about 10 degrees Fahrenheit. Hence, a 

change in global-mean temperature of two degrees would represent a considerable 

perturbation to the global climate system. Small changes in local temperatures can also 

be associated with large impacts. For example, for every degree Fahrenheit increase in 

mean annual temperature near Greenland, the rate of sea level rise is projected to 

increase by 10%. Snowpacks on mountains in the western U.S., which millions of people 

depend on for drinking water and other uses, is likewise extremely sensitive to small 

temperature changes. Natural ecosystems are also vulnerable to changes in 

temperature--in the Midwest, a one degree change in annual mean temperature might 

translate into several hundred miles in the ecological distribution of certain plants and 

grasses, and a warming of just a few degrees could have devastating impacts on New 

England's maple syrup industry and California's vineyards. Many parts of the climate 

system are already feeling the impacts of the one degree rise in global-mean temperature 

observed during the 20th century. As we noted on page 27 of the prepublication version 

of our report: "glaciers are retreating, permafrost is melting, snowcover is decreasing, 

Arctic sea ice is thinning, rivers and lakes are melting earlier and freezing later, bird 

migration and nesting dates are changing, flowers are blooming earlier, and the ranges 

of many insect and plant species are spreading to higher latitudes and higher elevations 

(e.g., ACIA 2001, Parmesan and Yohe 2003, Root et al. 2003, Bertaux et al. 2004, 

Bradshaw and Holzapfel 2006).” 

7. Dr. Von Storch testified that the effect of the "decentering" error in the Mann study, 

which was the basis of the McIntyre and Wegman criticisms, was "very minor." The 

NAS study did not refer to "decentering." How significant was the analysis of 

"decentering" to the NAS conclusions? 

I believe Dr. von Storch was referring to the same phenomenon that I described in my 

response to your question #5. Our committee did consider the effects of decentering, 

along with other criticisms of the Mann et al methodology, and found that it "does not 

appear to unduly influence reconstructions of hemispheric mean temperature.” 

8. At the hearing you were asked if you disputed the conclusions or the methodology of 

Dr. Wegman's report, and you stated that you did not. Were you referring solely to Dr. 

Wegman's criticism of the statistical approach of Dr. Mann, or were you also referring to 
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Dr. Wegman's social network analysis and conclusions? 

Dr. Wegman’s criticisms of the statistical methodology in the papers by Mann et al were 

consistent with our findings. Our committee did not consider any social network 

analyses and we did not have access to Dr. Wegman’s report during our deliberations so 

we did not have an opportunity to discuss his conclusions. Personally, I was not 

impressed by the social network analysis in the Wegman report, nor did I agree with most 

of the report’s conclusions on this subject. As I stated in my testimony, one might 

erroneously conclude, based on a social network analysis analogous to the one 

performed on Dr. Mann, that a very active and charismatic scientist is somehow guilty of 

conspiring or being inside a closed community or ‘mutual admiration society’. I would 

expect that a social network analysis of Enrico Fermi or any of the other scientists 

involved with the development of modern physics would yield a similar pattern of 

connections, yet there is no reason to believe that theoretical physics has suffered from 

being a tight-knit community. Moreover, as far as I can tell the only data that went into 

Dr. Wegman’s analysis was a list of individuals that Dr. Mann has co-authored papers 

with. It is difficult to see how this data has any bearing on the peer-review process, the 

need to include statisticians on every team that engages in climate research (which in my 

view is a particularly unrealistic and unnecessary recommendation), or any of the other 

findings and recommendations in Dr. Wegman’s report. I was also somewhat taken 

aback by the tone of the Wegman Report, which seems overly accusatory towards Dr. 

Mann and his colleagues, rather than being a neutral, impartial assessment of the 

techniques used in his research. In my opinion, while the techniques used in the original 

Mann et al papers may have been slightly flawed, the work was the first of its kind and 

deserves considerable credit for moving the field of paleoclimate research forward. It is 

also important to note that the main conclusions of the Mann et al studies have been 

supported by subsequent research. Finally, while our committee would agree with Dr. 

Wegman that access to research data could and should be improved, as discussed on 

page 23 of the prepublication version of our report, we also acknowledge the 

complicated nature of such mandates, especially in areas such as computer code where 

intellectual property rights need to be considered. 

The Honorable Marsha Blackburn

1. Dr. Mann used many temperature measurements from different sources to produce his 

graph. In your opinion, how much emphasis or reliance did he place on surface records 

and satellite measurements? 

To perform their surface temperature reconstruction, Dr. Mann and his colleagues made 

use of proxy data derived primarily from tree rings, ice cores, and documentary sources. 

Tree rings and ice cores, like other natural proxies, do not record temperature directly, 

but are correlated with local temperatures through physical and physiological 

mechanisms. They also made use of surface thermometer records from the last 150 

years, which were used to calibrate the reconstruction (i.e. translate the proxy data into a 

record of temperature) and to validate their results (i.e. test whether the reconstructed 

temperatures match a portion of the observations reserved for this purpose). All 

paleoclimate reconstructions use a similar methodology, with the exception of 

reconstructions based on borehole temperature measurements and glacier length 

records, which are translated directly into temperature time series using models based on 

the laws of physics. Satellite measurements are not used in any paleoclimate 

reconstructions because they only go back about 30 years, which is much too short for 

this application. 
593

a. How much weight do you think should be given to these measurements? 

Dr. Mann and his colleagues used all of the quality-controlled proxy data that they had 

at their disposal at the time. As we indicated in our report, the available proxy data are 

plentiful and geographically diverse for the last 400 years, but decrease in number and 

become subject to increasing uncertainties going back further into the past. Hence, we 

have high confidence in the surface temperature reconstructions based on these data for 

the last 400 years, but less confidence in reconstructions for the period from 900 to 1600 

A.D. This increasing uncertainty moving back in time is reflected, in part, by the 

increasing size of the error bars prior to 1600 A.D. in the original 'hockey stick' curve, 

although these error bars do not account for all of the uncertainties inherent in the 

reconstruction. 

2. The surface record and the satellite measurements indicate that if maybe natural 

warming and not human-induced warming. Yet, in your testimony, you say that 

increasing concentrations of greenhouse gases caused the warming. How do we reconcile 

your statement with the historical record? 

The temperature record alone cannot tell us the difference between ‘natural’ and 

‘human-induced’ temperature changes. One has to try to explain the observed warming 

using the laws of physics. During the last 100 years, the global-mean temperature first 

increased strongly, then remained constant or decreased slightly, then increased strongly 

again. Simple radiative transfer calculations and sophistical climate models both show 

that the total amount of warming observed over the 20th century is consistent with the 

observed increases in greenhouse gas concentrations in the atmosphere, which are 

undeniably the result of human activities. Changes in solar output can also influence the 

climate system. However, satellite measurements show that the sun has not increased in 

luminosity over the last 30 years, and estimates based on terrestrial measurements show 

only a modest increase in solar output during the first half of the 20th century. A third 

factor that may have had a significant influence on global-mean climate during the 20th 

century is atmospheric aerosols. These are the tiny particles that, like greenhouse gases, 

are emitted from volcanoes and other natural sources as well as from anthropogenic 

sources, but have been increasing in concentration in the atmosphere over the past 

century mainly due to the burning of fossil fuels and other human activities. Aerosols 

influence climate in a variety of ways, some of which are well known and others of which 

are active areas of research, but in general they have a cooling influence on climate. 

There is some evidence that suggests that aerosols may be primarily responsible for the 

slight decrease in global-mean temperature observed during the middle of the 20th 

century, and they might also be offsetting some of the warming due to greenhouse gases. 

a. Also, the historical record indicates that in the past 100 years, the Earth's global 

temperature warmed and cooled significantly while the concentrations of carbon dioxide 

increased. Would this not also indicate that the level of carbon dioxide in the atmosphere 

has had little effect on the warming of the atmosphere? 

No. The Earth's temperature over the past 100 years was influenced by increases in 

carbon dioxide and other greenhouse gases, which have a warming effect, by changes in 

aerosols, which generally cool the climate, and by other climate forcings. Thus, the 

observed temperature variations reflect the net effect of these different forcings. 

We have a very good understanding of the direct impact of carbon dioxide and other 
594

greenhouse gases on global temperature. Straightforward radiative transfer calculations 

tell us that carbon dioxide has a significant influence on global climate. Sophisticated 

climate models also show that the observed temperature changes during the 20th century 

cannot be reproduced unless greenhouse gases increases are included. There are also 

other lines of evidence indicating that carbon dioxide and other greenhouse gases have a 

strong influence on global climate. For example, models cannot reproduce the globalmean cooling that occurred during the last Ice Age without incorporating the reduced 

levels of greenhouse gases that prevailed during that time. 

3. You also state in your testimony that even if it was as warm or warmer 1000 years ago 

than today that it would not effect today's consensus on global warming. That seems to 

not be logical because if the Earth goes through natural cycles of warming and cooling, 

then would not the warming and cooling cycles over the past 60 and 500 years be a 

similar indication of phenomenon? 

It is true that the Earth has experienced natural cycles of warming and cooling over its 

history, however natural climate forcings (solar activity, changes in natural aerosols) 

observed over the last century are not large enough to produce the observed warming, 

especially for the last 30 years. There is a large and compelling body of evidence 

indicating that human-induced greenhouse gas increases are responsible for at least part 

of the total warming over the 20th century, and most of the warming over the last 30 

years. Over the last 100 years and especially the last 30 years, we have very good data 

for both temperature and all of the major climate forcings (greenhouse gases, solar 

activity, and aerosols). Analyses of these data indicate that human-induced greenhouse 

gases appear to be responsible for much of the warming over the last 30 years and at 

least part of the total warming over the last century. Reconstructions of surface 

temperature over the past 1,000 years are one piece of the scientific evidence, but these 

reconstructions are sufficiently uncertain, especially prior to 1600 A.D., that they are not 

usually considered to be among the primary evidence for human-induced global 

warming. In addition, temperature data alone do not tell us anything about cause and 

effect. 

In contrast, we know that greenhouse gases did not vary much during the 1,000 years 

prior to the industrial revolution, but we have very little data about how solar output and 

aerosols varied over this period. Moreover, what little evidence we do have shows only 

small variations in climate forcing due to natural causes. Hence, if we were to find out 

that the global-mean temperature 1,000 years ago was warmer than today, this would 

mean that the Earth's climate is even more sensitive to small forcings than we thought, 

which would mean that projections of future warming may be overly conservative. 
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RESPONSE FOR THE RECORD OF DR. THOMAS J. CROWLEY, NICHOLAS PROFESSOR OF EARTH 

SCIENCE SYSTEM, DUKE UNIVERSITY

Response by T. Crowley to Followup Questions on July 19 Testimony 

The Honorable Marsha Blackburn:

1. Do you agree or disagree with the surface record and satellite data which 

indicate that global temperatures did not start to rise significantly until the 1998 

El Nino? 

I emphatically disagree with this statement. The surface temperature record clearly 

shows very substantial warming before 1998. Recent work furthermore indicates that 

the satellite observations are close to being reconciled with these surface 

observations – and that the prior differences between the two was to a coding error in 

the analysis of the satellite data, not a problem with the surface data. 

Congresswoman Blackburn, anyone who tries to tell you that the warming did not 

occur until 1998 is seriously misleading you. 

2. Do you believe the available data shows a global Little Ice Age and/or Medieval 

Warm Period? 

It is not easy to give an unequivocal answer to this, because southern hemisphere 

data are considerably more spotty than northern hemisphere data. The available data 

suggest that the southern hemisphere did indeed have a cold period about the same 

time as the northern hemisphere. There are some indications of warmth in the 

southern hemisphere prior to that time, but it is not clear whether the timing of that 

warmth was the same as in the northern hemisphere. Although some northern 

hemisphere places during the Middle Ages were locally warmer than they are today, 

in the best-dated records the timing of Medieval warmth varied in different places. 

This is why composite reconstructions almost always show that the mean warmth 

for the Middle Ages is usually comparable to the mid-20th century but not the late 

20th century. 

3. Do you agree or disagree with the statement that warming from 1900 to 1940 

was caused by increase of solar activity or the warming of the Sun? 

I disagree with the statement because it is too categorical. There are some 

indications that changes in solar behavior may have contributed to the mid-20th

century warming. But when this “solar connection”is tested by going farther back in 

time the conclusions become much more equivocal. The most methodical analysis 

(see Attachment #1 – Hegerl et al. 2003) provides at best weak support for the longterm role of solar variability. Furthermore, the magnitude of past solar variations is 

very uncertain – even optimistic estimates indicate it is only a fraction of present 

greenhouse gas forcing. The present thinking is that the mid-20th century warming 

was due to a combination of weakened volcanic cooling, greenhouse warming, 

“natural variability”, and perhaps a modest contribution from solar output changes. 

4. What is your opinion on the effect of the 1998 El Nino on the recent rise in 

temperatures? 
596

The 1998 El Nino certainly contributed to the (at that time) record global 

temperatures but I don’t think anyone seriously thinks it has a long term effect on 

global temperature – the heat just dissipates too quickly in the atmosphere to have 

such an effect. I might add that it has taken less than a decade for the continually 

rising temperatures to approach or equal the 1998 temperatures. This increase is 

very disconcerting in terms of how fast the planet is warming. 

End of reply to the Honorable Marsha Blackburn 

 

The Honorable Bart Stupak:

1. In the hearing, Dr. Wegman testified that your 2000 published work, which 

used a simple averaging proxy methodology, obtained the same “hockey stick” 

configuration as Dr. Mann’s original work did. Dr. Wegman blames this 

conclusion on “proxies appropriately selected” apparently because of use of the 

bristlecone pine proxy. 

Please explain if and why your work also used the bristlecone pine proxy and 

respond to Dr. Wegman’s criticisms of its use. 

I do not recall Dr. Wegman making this testimony but will accept your claim. 

Actually the purpose of the Crowley-Lowery 2000 study (ms. submitted as hard 

copy during testimony) was not to reproduce Mann et al. with a different 

methodology but just to determine what would happen if we took a broad swath of 

data and just summed them up. I was as surprised as anyone that the result was as 

close to Mann et al. as it was – bristlecone pine or no bristlecone pine (the one we 

used was different than Mann et al’s). The principal significance of our finding was 

that the Mann et al. result appeared to be robust because it could be reproduced with 

a different methodology – a standard approach in science. 

The bristlecone pine business is a red herring. If the bristlecone pine record is 

removed from the composite of a dozen or so records, it will show slightly greater 

warming in the Middle Ages. But one record can only make so much a difference 

when it is averaged among a dozen, especially since the general shape of the 

bristlecone pine record is comparable to the other records. 

A more important objection to the bristlecone pine argument is that it should not be 

included. Why not? In statistics anyone can use something as a predictor or 

something else. The question is how could a predictor is it? Some have claimed 

that it should not be included because it is more affected by some other process (for 

example, precipitation). But a principal assumption of regression based prediction 

approaches is that the variables used for making predictions are linearly correlated 

with the variable they are predicting (in this theoretical case, precipitation with 

temperature). The degree of skill in the predictor can be tested by its correlation 

with temperature. If it has a poor correlation, it has little skill. This is an approach 

we have adopted in later papers, but the purpose of the original study was to just 

take as simple as an approach as possible. 
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2. There were numerous references in the hearing to a schematic drawing of what 

scientists supposed surface temperatures might have been from 1000 A.D. to 

1975 in the 1990 report of the Intergovernmental Panel for Climate Change 

(IPCC) . You stated in your testimony that Dr. Mann’s study represented the 

first attempt to estimate the uncertainties for surface temperature 

reconstructions prior to the instrumental period. Can you describe what level 

of uncertainty would have been placed on the 1990 schematic drawing, and 

what level of uncertainty Dr. Mann established for the period prior to 1600 

A.D. 

This is a good question! But before answering it I have to explain what happened 

during the formulation of the 1990 figure. At that time we really did not have any 

hemispheric estimates of temperature. What IPCC did in 1990 was informally poll 

various experts for a “guesstimate” of what the temperatures were like (I vaguely 

recall being asked by someone around that time, but I do not know if it was related 

to the IPCC figure). Many scientists had heard of the “Medieval Warm Period” and 

stories of warmth greater than the present. Despite warnings from a prominent 

Chinese scientist, and a prominent English scientist, that the timing of warmth in the 

Middle Ages was not the same in all places, many people (including some still now) 

assumed that the Medieval Warmth was globally synchronous. Thus the 1990 figure 

– entirely schematic and left standing until it could be replaced by an alternate 

quantitative estimate, with meaningful uncertainty estimates (i.e., the Mann et al. 

paper, and others that have followed). 

Now for the uncertainty estimates. One would have to be very wary to apply 

uncertainty estimates to a qualitative figure, but if one were to do so, then maybe a 

“ball park” 0.5 °C (about 1.0 °F) uncertainty might be applied. If so, then one 

would have to conclude that is not possible to make a robust statement that the 

Middle Ages were warmer than the present, because the original estimate likely did 

not exceed 0.5°C above “present” (which at the time of writing of the report was 

about seventeen years ago). [Note that I cannot find my copy of the original figure, 

so I would have to doublecheck the 0.5*C peak, but because the uncertainty estimate 

is also uncertain, I still stand by my conclusion about “inability to make a robust 

statement” 

With respect to the uncertainty estimates prior to 1600 in the Mann et al. paper, the 

most that can be stated is the estimates are substantially larger than for the later 

period just because there are much fewer records. The uncertainties for estimates of 

annual temperature are about 0.5°C in Mann et al. (1999). However, the degree of 

uncertainty would decrease as records are smoothed. For example, forty year 

smoothing of the Mann et al. record yields uncertainties of about 0.4°C. Smoothing 

comparable to the very smoothed 1990 IPCC figure has not, to my knowledge, been 

computed, but a reasonable guess would be that it would be in the range of 0.2-

0.3°C. 

3. Please describe the peer review process for your most recent publications. 

The peer review process has been pretty similar for my entire scientific career. The 

paper goes out to 2-3 reviewers, who almost always provide anonymous peer 

reviews (i.e., they can say anything they want about it!). If the reviewers like the 

paper but have questions, the editor will request that a revised manuscript be 

prepared that takes into account reviewer concerns, and that a separate accounting 
598

be made to the editor and reviewer about how specifically we addressed those 

concerned. Depending on the seriousness of the concerns, the editors will then 

either review the response themselves, or send it back to the reviewers (if the 

concerns are minor he or she would probably not sent it back to the reviewers). In 

some cases the reviewer may still be dissatisfied, in which case the authors would 

have to reiterate, but in many cases the reviewers will be satisfied. In some cases an 

editor might decide that if a reviewer is still dissatisfied, then the editor may choose 

to reject the paper. Only after the editor is fully satisfied that reviewers and 

reconciled will the editor accept the paper. In some cases the editor may accept a 

paper even if there are disagreements with reviewers, because a subject matter may 

be controversial and an editor may feel that all sides of an issue deserve a public 

airing. In that case an editor may still accept a paper that has been opposed by a 

reviewer. 

End of reply to the Honorable Bart Stupak 

The Honorable Henry A. Waxman: 

1. You were added to the witness list for this hearing on short notice, and 

therefore had very little time to prepare your testimony. In reviewing your 

previously submitted testimony, is there anything you would like to clarify or 

supplement for the record. 

Thank you for the opportunity to respond to this. I am satisfied with most of the 

document but there are a few typos and grammatical mishaps I would like to correct. 

I am also chagrined by the choice of words I sometimes used to describe some of 

Dr. Wegman’s report, and would like to change those. I will therefore send you a 

slightly revised version of the original document that makes such changes. If it is 

not possible to replace the original with the revision, then my statement herein is all 

I would like to add as a supplement. 

End of Reply to the Honorable Henry A. Waxman 
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QUESTIONS SURROUNDING THE 

‘HOCKEY STICK’ TEMPERATURE 

STUDIES: IMPLICATIONS FOR CLIMATE 

CHANGE ASSESSMENTS 

THURSDAY, JULY 27, 2006 

HOUSE OF REPRESENTATIVES, 

COMMITTEE ON ENERGY AND COMMERCE, 

SUBCOMMITTEE ON OVERSIGHT AND INVESTIGATIONS, 

Washington, DC. 

 The subcommittee met, pursuant to call, at 2:00 p.m., in Room 2322 

of the Rayburn House Office Building, Hon. Ed Whitfield (Chairman) 

presiding. 

 Members present: Representatives Stearns, Pickering, Bass, 

Blackburn, Barton (ex officio), Stupak, Schakowsky, Inslee, Baldwin, 

Waxman, and Whitfield. 

 Staff present: Mark Paoletta, Chief Counsel for Oversight and 

Investigations; Peter Spencer, Professional Staff Member; Tom Feddo, 

Counsel; Matt Johnson, Legislative Clerk; John Halliwell, Policy 

Coordinator; Clayton Matheson, Analyst; Mike Abraham, Legislative 

Clerk; Edith Holleman, Minority Counsel; David Vogel, Minority 

Research Assistant; Chris Knauer, Minority Investigator; and Lorie 

Schmidt, Minority Counsel. 

 MR. WHITFIELD. This hearing will come to order, and I want to 

certainly welcome everyone to today’s hearing. This is the second day 

of our hearing regarding questions about what we popularly call the 

hockey stick temperature studies and the implications for climate change 

assessments. We have reconvened this hearing to accommodate a key 

person in the matters before us, and that is Dr. Michael Mann of Penn 

State University. Dr. Mann was unable to attend the session on the 

subject last week, and we are looking forward to his testimony. 

 As you know, he was one of the leaders in the methodology of 

developing the methodology that developed the hockey stick graph, and 

we hope we can continue to explore some of the broader questions 

surrounding temperature reconstruction findings, their use in the IPCC 

assessment, and other issues that prompted our inquiry into this matter 

last year. Now the hockey stick graphic and the underlying studies were 

influential in a prominent set of findings by the IPCC, and really the 
604

hockey stick graphic has become an icon for all those concerned about 

global warming. 

 In point of fact, from the very first set of findings on the very first 

page of discussion in its 2001 summary for policy makers the IPCC 

states that 20th Century temperature increases were likely the largest in 

1000 years, and it was likely that in the Northern Hemisphere the 1990s 

was the warmest decade and 1998 the warmest year, a phrase that is 

almost verbatim what Dr. Mann and his colleagues wrote in their 1999 

paper. Next to these findings the IPCC summary then displays Dr. Mann 

and his colleagues’ hockey stick shaped temperature graph which helped 

this work prominently and moved it into the public eye. 

 Now let me just take a moment and make a few observations about 

last week’s hearing. First, through our discussion of both the National 

Research Council report and the Wegman report the original studies by 

Mann and his co-authors appeared to be flawed, and cannot support the 

related findings of the 2001 IPCC assessment. Dr. Wegman’s 

independent committee found and reported that Dr. Mann and his coauthors incorrectly applied a statistical methodology that would 

preferentially create hockey stick shapes. 

 Dr. Wegman also found that more recent methodologies used in 

temperature reconstruction studies may also generate problematic biases 

when determining temperature histories. Now the National Research 

Council based on the Mann analysis and newer supporting evidence finds 

that it is plausible that the Northern Hemisphere was warmer during the 

last few decades of the 20th Century than during any period comparable 

in the preceding millennium. Even less confidence, and I am quoting 

from their report, even less confidence can be placed in the original 

conclusion by Mann that the 1990s are likely the warmest decade, and 

1998 the warmest year. 

 The NRC’s panel review determined that Dr. Mann made in the 

words of the NRC witnesses inappropriate choices and that the panel had 

much the same misgivings about Dr. Mann’s work, That was 

documented at much greater length by Dr. Wegman. Moreover, both the 

NRC and Wegman reports essentially corroborated the main criticisms 

raised by the McIntyre-McKitrick studies about Dr. Mann’s initial 

hockey stick studies. Now while much attention was given to Dr. 

Wegman’s social network analysis, I think it is only fair to observe the 

limits of what he was trying to illustrate as he himself explained. 

 Dr. Wegman was not seeking to impugn the integrity of any of the 

scientists who work in the area, but it is clear that peer review somehow 

failed to pick up the flaws in the hockey stick studies. Dr. Wegman 

simply raises the possibilities that given the evident publishing 

relationship among the authors of many of the relevant works combined 
605

with the failure to involve statisticians that Dr. Manns’ peers may have 

been too close to the topic to scrutinize the studies as rigorously as they 

might have. 

 Whatever the case, Dr. Manns’ peers failed to catch the errors that 

Wegman, the NRC and McIntyre identified. Now this failure as Dr. von 

Storch suggested last week may be less an issue with the community of 

paleoclimatologists than with the journal editors themselves. Now 

finally I think it is important to note that virtually everyone at the hearing 

last week, both members and witnesses, took the view that criticisms of 

the hockey stick studies or of the peer review and assessment process 

should not be considered as a judgment about the changes in global 

temperature, but rather the issues at hand concern legitimate questions 

about the rigor of scientific analysis, the results of which ultimately reach 

policy makers and that is what we base our decision-making decisions 

on. 

 So the hockey stick story provides a clear case study into what may 

be the lack of proper scrutiny, and the questions last week about the 

independence of peer review or the gate keeping issues in my mind are 

legitimate. And I think that everyone would agree that we must be very 

careful and make sure that when we do these analyses and they receive 

the publicity that they do that they be scientifically based and as close to 

accurate as possible. 

 Now in addition to Dr. Mann, both Dr. Wegman and Dr. McIntyre 

are returning to recap their testimony and to answer any questions related 

to their work, and certainly Dr. Mann may want to raise some issues 

regarding what you all said. We have a few additional panelists as well. 

As we were preparing this panel, some have been suggested by the 

minority side, and I am not sure which ones, but I want to welcome Dr. 

John Christy, the Director of the Earth System Science Center, and an 

Alabama State climatologist at the University of Alabama, Huntsville, 

and Dr. Gulledge of the Pew Center for Climate Change. And then 

finally I would like to recognize Dr. Ralph Cicerone, who is the 

President of the National Academy of Sciences, and happened to be in 

the same fraternity that I was, so, Dr. Cicerone, welcome. 

 And he has been instrumental in the National Academy’s focus on 

climate change research in recent years. Indeed, he chaired the National 

Research Council’s 2001 report for President Bush that helped pave the 

way for the United States to conduct its own climate change assessment. 

I want to welcome all of you. Thank you for your time. We look 

forward to your testimony. And I yield and recognize the distinguished 

ranking member, Mr. Stupak. 

 [The prepared statement of Hon. Ed Whitfield follows:] 
606

PREPARED STATEMENT OF THE HON. ED WHITFIELD, CHAIRMAN, SUBCOMMITTEE ON 

OVERSIGHT AND INVESTIGATIONS

Good afternoon and welcome to a second day of our hearing regarding questions 

about what we popularly call the “hockey stick” temperature studies and the implications 

for climate change assessments. 

We’ve reconvened this hearing to accommodate a key person in the matters before 

us, Dr. Michael Mann, of Penn State University. Dr. Mann was unable to attend the 

informative session on this subject last week. Although Dr. Thomas Crowley – Dr. 

Mann’s personally recommended replacement – did testify, we are providing Dr. Mann 

the opportunity to discuss his work and respond to some of the views expressed about his 

work. 

Welcome Dr. Mann, I’m looking forward to your testimony and participation. I 

hope we can continue to explore some of the broader questions surrounding temperature 

reconstruction findings, their use in the IPCC assessment, and other issues that prompted 

our inquiry into this matter last year. 

 The hockey stick graphic and the underlying studies were influential in a prominent 

set of findings by the IPCC. In point of fact, from the very first set of findings on the 

very first page of discussion in its 2001 Summary for Policymakers, the IPCC states that 

20th Century temperature increases were likely the largest in 1,000 years and it was 

[quote] “likely that, in the Northern Hemisphere, the 1990s was the warmest decade and 

1998 the warmest year,” a phrase that is almost verbatim what Dr. Mann and his 

colleagues wrote in their 1999 paper. Next to these findings, the IPCC Summary then 

displays Dr. Mann and his colleagues’ hockey stick-shaped temperature graph, which 

helped this work prominently into the public eye. 

Let me take a moment and make few observations about last week’s hearing. 

First, through our discussion of both the National Research Council report and the 

Wegman report, we established that the original studies by Mann and his coauthors were 

flawed, and could not support the related findings of the 2001 IPCC assessment. Dr. 

Wegman’s independent committee found and reported that Dr. Mann and his coauthors 

incorrectly applied a statistical methodology that would preferentially create hockey stick 

shapes. Dr. Wegman also found that more recent methodologies used in temperature 

reconstruction studies may also generate problematic biases when determining 

temperature histories. 

The National Research Council, upon its review of the current state of science on 

this subject, likewise found that the hockey stick studies could not support the 2001 IPCC 

finding drawn from them. The NRC panel’s review determined that Dr. Mann made, in 

the words of the NRC witnesses, “inappropriate” choices, and that the panel had “much 

the same misgivings about [Dr. Mann’s] work that was documented at much greater 

length by Dr. Wegman.” 

Moreover, both the NRC and Wegman reports essentially corroborated the main 

criticisms raised by the McIntyre-McKitrick studies about Dr. Mann’s initial hockey stick 

studies. 

While much attention was given to Dr. Wegman’s social network analysis, I think it 

is only fair to observe the limits of what he was trying to illustrate, as he himself tried to 

explain. 

Dr. Wegman was not seeking to impugn the integrity of any of the scientists who 

work in this area, but it is clear that peer review somehow failed to pick up the flaws in 

the hockey stick studies. Dr. Wegman simply raises the possibility that, given the evident 

publishing relationship among the authors of many of the relevant works, combined with 

the failure to involve statisticians, Dr. Mann’s peers may have been too close to the topic 

to scrutinize the studies as rigorously as they might have. Whatever the case, Dr. Mann’s 

peers failed to catch the errors Wegman, the NRC, and McIntyre identified. 
607

This failure, as Dr. von Storch suggested last week, may be less an issue with the 

community of paleoclimatologists, than with the journal editors themselves. The 

Committee can remain cautious about Dr. Wegman’s social network analysis, as he is, 

and still legitimately raise the broader question about the rigor of review and breadth of 

reviewers in this field. 

Finally, I think it is important to note that virtually everyone at the hearing last week 

– both members and witnesses – took the view that criticisms of the hockey stick studies 

or of the peer-review and assessment process should not be construed as a judgment 

about the changes in global temperatures. 

Rather, the issues at hand concern legitimate questions about the rigor of scientific 

analysis, the results of which ultimately reach policy makers. The hockey stick story 

provides a clear case study into the lack of proper scrutiny, and the questions last week 

about the independence of peer-review, or the “gate keeping” issues, were entirely 

legitimate. I hope that as we proceed today, we keep this in mind. And I hope that we 

can all reach agreement on ways to improve the process. 

Let me note that we have, in addition to Dr. Mann, both Dr. Wegman and Mr. 

McIntyre returning to recap their testimony and to answer questions related to their work, 

if necessary. Both of them graciously agreed to adjust their busy schedules, including 

family and work obligations, to return today at our request so that Dr. Mann could 

confront his critics. Thank you very much for coming back. 

We have a few additional panelists as well. As we were preparing this panel, our 

minority counterparts requested an additional witness. In the event, we accommodated 

their requests so that we could have as informative and balanced a panel as possible. 

So let me welcome Dr. John Christy, the Director of the Earth System Science 

Center and Alabama State Climatologist at the University of Alabama, Huntsville and Dr. 

Jay Gulledge, of the Pew Center for Climate Change. 

Finally, I’d like to recognize a most-distinguished witness, Dr. Ralph Cicerone 

[sisserone], President of the National Academy of Sciences. Dr. Cicerone has been 

instrumental in the National Academies’ focus on climate change research in recent 

years. Indeed, he chaired the National Research Council’s 2001 report for President Bush 

that helped pave the way for the United States to conduct its own climate change 

assessments. 

Welcome Dr. Cicerone, and welcome all the witnesses, I look forward to another 

informative panel. 

I now yield to my distinguished Ranking Member, Mr. Stupak. 

 MR. STUPAK. Thank you, Mr. Chairman. Today we are holding a 

very strange hearing. Originally scheduled to give Dr. Michael Mann a 

chance to respond to critics who provided testimony to this committee 

last week, this hearing has now expanded to allow these critics to attack 

the very science of global warming. Witnesses reappearing in the 

committee today, once commissioned by the Majority to do a very 

limited and biased review, had attempted to discredit Dr. Mann’s 8-year 

old study on reconstruction of surface temperatures over the last 

thousand years, and his conclusion that the earth is warming at an 

unprecedented rate. 

 However, as Dr. North testified last week, a comprehensive review 

of temperature reconstruction research by the National Academy of 

Science at the request of the Science Committee found that there were 

numerous other studies concluding that the Earth is warming at an 
608

unprecedented rate. Now instead of allowing Dr. Mann to respond to last 

week’s allegations, two of our witnesses, apparently unhappy with the 

outcome of last week’s hearing have decided to rewrite and expand their 

testimony to raise new issues, new complaints, and new questions. 

 This re-written testimony is no longer limited to Dr. Mann’s 

statistical methods and their own work, but also includes areas of 

climatology totally outside their expertise. As a result, it appears that 

these critics have lost interest in simply attacking Dr. Mann’s work. 

Now the purpose of today’s hearing is to cast doubt on all scientific 

evidence of global warming. Mr. Chairman, if we are going to discuss 

the larger issue of global warming, which many of us on this side would 

be happy to do, we need to put more time and effort into putting together 

a series of well thought out hearings with adequate time for witnesses 

and staff to prepare. 

 If the Majority were truly interested only in temperature 

reconstruction over the past thousand years we could have heard from all 

of the scientists who have worked on this topic both before and after Dr. 

Mann’s original 1998 and 1999 publications. Instead, the Majority asked 

Dr. Wegman, a statistician with no expertise in paleoclimatology, to 

verify only Mr. McIntyre’s critique of Dr. Mann’s initial work. Dr. 

Wegman was not even asked if Dr. Mann’s conclusions would change if 

the criticisms were incorporated and the analysis were re-created, nor did 

he volunteer to do that. 

 Other climatologists have recreated Dr. Mann’s work and have come 

to the same conclusions using both similar and different data sets and 

methodologies. Dr. Wegman, who has not reviewed this work and did 

not discuss any of the studies in his testimony last week, will try to 

discredit all of these studies with an unsupported hypothesis questioning 

the independence of a large group of scientists work. 

 Another witness we will hear from today, Dr. Christy, has supported 

the science behind global warming but will argue that by acting to curb 

global warming we may deny the poor in other countries the advantages 

that we have here in America. This is also the argument of a new group, 

the Interfaith Stewardship Alliance, but we have not heard from the 

alliance when trying to provide low-income emergency assistance for 

people in my district. 

 However, the threat of rising temperatures and the negative results of 

them, including diminished agricultural production, and quite possibly 

the flooding of vast heavily populated coastal areas due to the melting of 

the polar ice caps, can be far more of a threat to developing countries 

than efforts to limit harmful industrial emissions. The National Climatic 

Data Center has recently confirmed that the first half of 2006 was the 
609

warmest first half of any year in the United States since 1895. This 

warming trend is continuing. 

 Today’s headline in the Washington Post, I should say Tuesday’s 

headline in the Washington Post, “Deadly Heat Continues in California.” 

The morgue in Fresno, California has many bodies of elderly people 

overcome by heat. Unprecedented temperatures have been recorded 

recently in Oregon and South Dakota, among other places. Forty-five 

percent of the United States is in moderate to extreme drought 

conditions. These conditions have spawned more than 50,000 wildfires 

burning approximately 4 million acres. 

 Congress is not particularly capable to judge science that deals with 

linear regressions, Pearson’s R square, centering and de-centering, or 

regulized expectation maximization. As Dr. Cicerone will remind us, 

that is why Congress created the National Academy of Science. We are, 

however, able to understand the strategy of Exxon Mobil, outlined in 

their 1998 action plan. This plan argued, and I quote, “victory will be 

achieved when average citizens understand, recognize uncertainties in 

climate science.” This appears to be the focus of today’s hearing, to 

confuse and complicate the findings of climate scientists, and Dr. Mann 

is unfortunately in the crosshairs. I yield back the balance of my time. 

 [Additional information submitted for the record follows:] 
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 MR. WHITFIELD. The chair recognizes the chairman of the Energy 

and Commerce Committee, Mr. Barton of Texas. 
619

 CHAIRMAN BARTON. Thank you, Mr. Chairman, and thank you for 

this hearing. I want to thank our witnesses for being here, some of them 

for the second time. We are obviously glad to have Dr. Mann here. We 

appreciate you being able to join us. It is clear from last week’s hearing 

on global climate temperature studies that we face issues involving more 

than the particulars of Dr. Mann’s specific hockey stick study. However, 

it is the particulars of these studies and how the existing climate 

assessment process has dealt with them that got us here today. 

 I appreciate the participation of this panel. I am glad that Dr. Ralph 

Cicerone is here. He is the President of the National Academy of 

Sciences. I think he is going to add significant weight and gravitus to the 

hearing today. As you noted in your statement, Chairman Whitfield, last 

week’s hearing demonstrated why we as policymakers need to 

understand the quality and the reliability of the science on which we are 

urged to base public policy that is both sweeping and costly. Some very 

respected and authoritative sources testified last week that Dr. Mann’s 

studies were flawed. They couldn’t support the findings for which they 

were used in the United Nations Climate Change Assessment, the IPCC. 

Today I hope that we are going to examine some of these issues in more 

detail. 

 I recognize that additional work has been published that supports the 

broad outline of some of those conclusions in Dr. Mann’s initial hockey 

stick study, but according to the National Research Council even that 

subsequent work cannot provide the level of confidence that IPCC placed 

upon the original hockey stick analysis. Nothing about the process of 

turning observations into accepted theory is smooth. It has been said that 

the politics of small towns and big universities are brutal. They make us 

look amateurs by comparison. Looking at what is happening in this 

issue, I think that might well be true. Unfortunately, that is the way this 

science progresses. 

 I not only accept it, bumps included, but, believe it or not, I support 

it. What I can’t accept is the improbable notion that this committee may 

not ask science or research-related questions that bear on policy making 

when the answers could improve the information we use to reach the 

policy decisions that we are elected to make. It is just wrong to say that 

questions are not permitted, free debate is improper or that anyone who 

wonders if the scientific establishment really has it right should be 

dismissed as anti-science or oblivious to the real risk of man-made 

climate change. 

 This committee holds a very key role in any policy-making decision 

related to climate change. As its Chairman, I have an obligation to be 

cognizant of that and to do everything possible to get a fair record but 

also get into the details of some of the theories that the policies, the 
620

recommended policies, are supposedly based upon. We are interested in 

Dr. Mann’s work, not because of Dr. Mann, as nice a fellow as he may or 

may not be; we are interested in Dr. Mann’s work because it was the 

original. It was seminal. It is referred to. 

 I haven’t seen Vice President Gore’s movie, but I am told in that 

movie Dr. Mann’s hockey stick diagram is shown repeatedly. It is only 

fair to take a look at the original seminal work to see if it really lives up 

to what it claims to be. During our last hearing, we were shrugged at for 

asking about that particular study saying it was too early, too distant, but 

the fact is that that particular study is the study that much of the latter 

conclusions have been based upon. It is only common sense to take a 

look at it. We are going to work on the issue, and if it turns out that that 

study is not the right study and if there are more current studies that are 

more correct, we will take a look at those too and we will find out what 

the truth is. The truth is the truth. The truth may be inconvenient. It 

may be politically incorrect, but the truth is the truth. 

 A couple of months ago Chairman Whitfield and I asked the U.S. 

Government Accountability Office to help us examine Federal data 

sharing policies especially as they related to climate change research. 

This work will help our efforts to improve the exchange of scientific data 

and other essential information, which as we have seen has been a 

particular problem in the climate change arena. When the dust settles on 

these hearings, I am going to prepare a request to the National Research 

Council, which Dr. Cicerone who is with us today chairs, to take some of 

the issues that Dr. Wegman and others have raised and take a look at it. 

 I am going to ask for a study to assess how to include a wider 

spectrum of scientific disciplines in climate change research so that we 

can be enlightened by the very best work across the field of scientific 

research. I am going to ask that this study be coordinated and run though 

the NRC’s Division on Engineering and Physical Sciences so that we can 

ensure that the disciplines like mathematics and physics and statistics 

participate up front. I would be happy to hear any of Dr. Cicerone’s 

comments on that today as we go forward. 

 Letting a wider scientific community address questions about climate 

change assessments can only help the process and improve the results. 

We have an obligation on this committee on behalf of the American 

people to ensure that the decision makers have the best information 

possible, not just the politically correct information. I want to thank 

again our panel for coming. I want to especially thank Dr. Mann for 

changing his schedule to be here. I look forward to a very productive 

exchange of views as we go forward today. Thank you, Mr. Chairman. 

 [The prepared statement of Hon. Joe Barton follows:] 
621

PREPARED STATEMENT OF THE HON. JOE BARTON, CHAIRMAN, COMMITTEE ON ENERGY 

AND COMMERCE

Thank you, Chairman Whitfield. It is clear from last week’s hearing on global 

climate temperature studies that we face issues involving much more than the particulars 

of Dr. Mann’s “hockey stick” studies. However, it is the particulars of these studies – 

and how the existing climate assessment process dealt with them – that got us here today. 

And so I appreciate that Dr. Mann accepted our invitation to lay out his important work 

on global temperature reconstruction, as well as to answer our broader questions 

concerning climate change assessments. 

I also appreciate the participation and perspective of our distinguished panelists 

today, including Dr. Ralph Cicerone, the President of the National Academy of Sciences. 

Let me also welcome back Dr. Wegman and Mr. McIntyre, who testified last week. 

 As you noted, Chairman Whitfield, last week’s hearing demonstrated why we as 

policymakers need to understand the quality and reliability of the science on which we 

are urged to base policy that is both sweeping and costly. Some very respected and 

authoritative sources testified last week that Dr. Mann’s studies were flawed, and that 

they couldn’t support the findings for which they were used by the United Nation’s 

climate change assessment, the IPCC. Today I hope we can examine some of these 

issues a bit more. 

I do recognize that additional work has been published that supports in broad outline 

some of the conclusions of Dr. Mann’s initial “hockey stick” studies. But according to 

the National Research Council, even that subsequent work cannot provide the level of 

confidence that IPCC placed upon the hockey stick studies. 

Nothing about the process of turning observations into accepted theories is smooth. 

It has been said that the politics of small towns and big universities are brutal enough to 

make our kind look amateurish by comparison, and I think that might be true. In any 

case, that’s the way science progresses. I not only accept it -- bumps included -- but I 

support it. 

What I can’t accept is the improbable notion that this committee may not ask 

science- or research-related questions that bear on policymaking when the answers could 

improve the information we use to reach those policy decisions. It is just wrong to say 

that questions are not permitted, or that free debate is improper, or that anyone who 

wonders if the scientific establishment really has it right should be dismissed as antiscience or oblivious to the real risks of manmade climate change. Because this 

Committee holds a key role in any policymaking relating to climate change, as its 

Chairman I will do everything I can to ensure that the very best information on these 

issues is available to us. 

We’re interested in Dr. Mann’s work because it is seminal. During our last hearing, 

some shrugged at it as distant and early, but the fact is that Dr. Mann’s conclusions 

influence both current research and global policy. As we try to close the loop on our 

concerns, I also want to emphasize that this Committee will continue to work on the 

issues raised here, to help ensure the reliability of future scientific assessments. 

A couple of months ago, Chairman Whitfield and I asked the U.S. Government 

Accountability Office to help us examine federal data sharing policies, especially as they 

related to climate change research. This work will help our efforts to improve the 

exchange of scientific data and other essential information – which as we have seen has 

been a particular problem in this climate change arena. 

Also, when the dust settles on these hearings, I’m going to prepare a request to the 

National Research Council, which Dr. Cicerone chairs, to take on some of the issues that 

Dr. Wegman and others have raised for us. I will ask for a study that assesses how to 

include a wider spectrum of scientific disciplines in climate change research so that we 

can be enlightened by the very best work that our scientists conduct, all of them. I’ll ask 
622

that this study be coordinated and run though the NRC’s Division on Engineering and 

Physical Sciences, so that we can ensure that disciplines like mathematics, physics, and 

statistics participate up front. I’ll welcome Dr. Cicerone’s perspective on this today, so 

that we can formulate an effective request. 

Letting a wider scientific community address questions about climate change 

assessments can only help the process and improve the results. We have an obligation on 

this Committee to ensure that America’s decision-makers have the best information 

possible. 

Thank you all for coming to testify today. I yield back the remainder of my time. 

 MR. WHITFIELD. Mr. Waxman of California is recognized. 

 MR. WAXMAN. Thank you very much, Mr. Chairman. The 

magnitude of global warming and the crisis that we are facing on this 

planet demands a serious response from this body. We should be holding 

hearings to understand the ramifications of recent studies detailing the 

harmful effects of global warming that we are seeing all around us from 

increased wildfires in the west to more intense hurricanes, more acidic 

oceans. We should examine practical steps this Congress and the 

Administration must take to reduce global warming pollution. We 

should explore how best to re-engage with the international community 

on addressing this problem because this is going to require all countries 

to do their part. 

 We should investigate the well-funded effort by certain oil 

companies to manufacture controversy and cast doubt on the reality of 

global warming and the human contribution to it. This hearing today is 

the third that this committee has held on the issue of global warming. 

We are the committee that would move legislation forward on this 

subject, and this is really a continuation of the second one, which was 

last week. In that hearing, the Republican majority attempted to discredit 

a respected climate scientist and a study he published 8 years ago. Well, 

not only is this use of the subcommittee ridiculous and unfair, it is also a 

waste. Yet, despite its intended focus, today’s hearing does give us the 

opportunity to learn more about the current state of climate science, and I 

am looking forward to hearing the views of Dr. Ralph Cicerone, who is 

the President of the National Academy of Sciences, and the Chairman of 

the National Research Council and a fraternity brother of the Chairman 

of this subcommittee, and he is an eminent climate scientist. 

 I am also very pleased we are going to hear from Dr. Mann, who is 

one of the world’s most distinguished paleoclimatologists. Eight years 

ago, Dr. Mann and his colleagues published a groundbreaking study that 

reconstructed the temperature of the Earth over the past 600 years using 

proxy data such as tree rings. Since 2002, Dr. Mann has published 

another half dozen papers revising and building on his work. These 

latter studies, as well as many independent paleoclimate reconstructions 

by other scientists continue to find the same thing. The warmer 
623

temperatures in the last few decades are unprecedented compared to 

anything we have experienced in the last thousand years. 

 Now the Majority, the Republicans, won’t use this hearing to 

examine Dr. Mann’s recent studies or the independent confirmation of its 

work. Instead, they want to focus exclusively on his original work in 

1998 and 1999 because they think they can find a statistical flaw. So 

what? The strategy is not a subtle one. Because they think they found a 

flaw in one study out of thousands the Majority wants to build the one 

study into the pillar of the scientific case for global warming. The 

Chairman seems to think that if he can discredit one climate scientist, Dr. 

Mann, he can cast doubt on all the climate change research. In effect, it 

is back to the tactics of the tobacco industry. 

 I remember well when they would send their scientists to come in 

and just cast a little doubt about whether smoking cigarettes really do 

cause cancer, whether there is really a medical problem. I think 

intimidation is part of the strategy we are seeing. This subcommittee 

launched this campaign against Dr. Mann and several of his colleagues 

last year by demanding to know the source of funding for every study 

they had ever conducted and demanding that they turn over all the data 

for all their research. These are bullying tactics and they drew highly 

unusual protests from the American Association for the Advancement of 

Science, the National Academy of Sciences, and the Republican 

Chairman of the House Science Committee, among others. 

 Well, we are having Dr. Mann here today. It is important that he be 

here. Last week we held a hearing where he was criticized. Now he has 

got his accusers back again. They couldn’t wait to have the hearing 

where all of them were together. But this subcommittee will hear about 

Dr. Mann’s work from him and those who criticize him. The 

subcommittee will hear the many other completely independent lines of 

evidence that support the reality of global warming and the role of 

humans in causing it. 

 The scientific evidence of human contribution to global warming is 

clear and compelling. The only open question is how long members of 

this subcommittee will keep pretending that it doesn’t exist. I don’t 

know how many hearings we are going to have on the subject of Dr. 

Mann’s one study in 1998, but it seems to me that as we look around this 

country and in in fact all around the world just today we are seeing a 

continuation of some of the highest temperatures on record. We ought to 

get serious about this matter of global warming and climate change. We 

ought to be holding hearings about the important issues that relate to it 

and not this one issue over and over again. I yield back the balance of 

my time. 
624

 MR. WHITFIELD. I would point out that even though Dr. Mann was 

not here last week, he did suggest that Dr. Crowley come on his behalf, 

and Dr. Crowley did testify. I recognize the gentleman from Mississippi 

for an opening statement. 

 MR. PICKERING. Mr. Chairman, I thank you for this hearing, and I 

yield back my time. I want to get to the panel as quickly as possible. 

 MR. WHITFIELD. Mrs. Blackburn, you are recognized. 

 MRS. BLACKBURN. Thank you, Mr. Chairman. I do want to thank 

you for the hearing, and I want to welcome all of our witnesses. I want 

to thank you for being patient with us and allowing us some more time to 

visit with you. At last week’s hearing we did hear testimony regarding 

errors in Dr. Mann’s 1998 and 1999 hockey stick report, and today we 

are going to be able to hear Dr. Mann’s response to that. We are pleased 

to have him join us and are looking forward to that response. 

 I do still have some questions, and I find some of the circumstances 

involving Dr. Mann’s paper a little bit disconcerting. It seems that it 

could only be corroborated by a social network and that seems to be a 

problem. It is difficult for me to see how scientists and policy makers 

could agree with and legislate anything based on research which by all 

appearances cannot be corroborated by independent review. Second, it is 

apparent that until now no independent experts have examined Dr. 

Mann’s data and statistical procedures. 

 Again, it is difficult to rely on data that has not been rigorously 

examined for consistency and validity. I am looking forward to some 

answers on that, and I would not say that it is intimidation that has 

brought questions forward. I would say it really is curiosity and a desire 

to know answers. Finally, I have noticed a trend, and this trend raises 

questions, and it is that trend by where a close group of scientists who 

support climate change theory tend to be serving as the primary peer 

reviewers and the lack of that independent review, and those reviewers 

are checking one another’s work. And it may be strictly coincidence but 

again it does not lead me to believe these papers are being as thoroughly 

examined as they might by those that are independent, and the public is 

not being as well served as they should of what they are told is scientific 

proof. 

 It is critical that even if we should discount the 1990 IPCC report, 

recent analysis of over 250 climate studies and historical records showed 

that the medieval warm period was global and higher than present day 

temperature, and they both concurred that the little Ice Age occurred 

worldwide and produced a substantial drop in the average temperature. 

Also, satellite data and the U.S. surface record indicate that the Earth’s 

temperature in the past 100 years has undergone both warming and 

cooling trends. 
625

 Last week I mentioned in 1960 when I was in high school there was 

a commonly held premise that we were returning to the Ice Age and by 

the time I reached my current age and a new millennium dawned we 

would be in a perpetual winter with food shortages, et cetera. So we had 

that, that we were dealing with in a cooling trend and that we were being 

taught as high schoolers in the ‘60s, but recent trends seemed to be 

caused by solar activity in the 1990 El Nino, not necessarily by the 

increase of green house gas emissions. 

 Mr. Chairman, policy makers depend on the integrity of data. The 

public depends on the integrity of data. Educational institutions depend 

on the integrity of data and results, and I believe it is necessary and 

proper for us to set quality standards for data release and verification for 

any research that receives Federal funds. Thank you, and I yield back. 

 MR. WHITFIELD. Thank you. I recognize Ms. Baldwin of Wisconsin 

for her opening statement. 

 MS. BALDWIN. Thank you, Mr. Chairman. Again, we are here 

discussing global warming, and again I think our focus is off target. 

Rather than addressing action steps to address global warming in a 

bipartisan coordinated and effective manner, we are covering up the real 

issues with irrelevant chatter about the basis of a study that was released 

almost a decade ago, a study that has been updated, revised, reviewed, 

and validated time and time again in recent years. Unfortunately, the 

goal of these hearings is not to show that there is an abundance of 

science demonstrating that the Earth is warming at an unprecedented 

rate, that carbon dioxide levels are rising, and that human activities are 

largely the cause. Rather it is an attempt to poke holes in an old study 

and divert attention away from the decisions that we as policy makers 

often have to make. 

 Decisions like should we let big business profits override human 

interests or should our policy time horizon be a few short years or should 

we be thinking about protecting generations yet to come. For if this 

hearing and even Dr. Wegman’s analysis were not commissioned for 

political reasons but rather out of a concern that study after study shows 

the Earth is warming, sea levels rising and snow caps melting, then we 

would be focusing on current information. The committee would have 

asked Dr. Wegman to review Dr. Mann’s and other reputable scientists’ 

work that has been published in recent years. But this is not what the 

committee requested nor what Dr. Wegman studied. 

 Instead, the focus is on Dr. Mann’s 1998 and 1999 study that 

contains acknowledged flaws. The argument made over the last week 

against Dr. Mann’s early work are old and tired and really I believe their 

desperate attempts to divert attention away from what countless experts 

agree, that climate change is happening, the global warming is 
626

happening, and that our actions, things we as humans do each and every 

day, contribute to this crisis. It is troubling that the United States appears 

to be alone on this island of skeptics. More troubling is that we are 

virtually alone and are inaction. 

 Despite being the largest consumer of electricity, oil, and natural gas, 

we refuse to take bold steps that will allow us to lead the world on 

environmental issues, yet countries with significantly smaller footprints 

on the world are making incredible advances that improve the quality of 

the air they breathe, the food and water they consume, and the lifestyles 

they lead. Let me just give a couple of examples. China’s fuel economy 

standards are more stringent than those in Australia, Canada, California, 

and the United States. Meanwhile, we haven’t increased our fuel 

economy standards in over 20 years. 

 Brazil’s ethanol program, the largest in the world, has created rural 

jobs, reduced air pollution, and reduced Brazil’s green house gas 

emissions while reducing its dependence on imported oil, yet we refuse 

to take necessary steps to reduce our dependence on foreign energy. 

Denmark has the highest utilization rate of wind energy in the world with 

wind producing approximately 20 percent of Danish electrical 

consumption. Meanwhile, our government has issued notices of 

presumed hazard to wind developers in the Midwest halting and 

threatening to permanently derail wind production. 

 And just yesterday Northern Ireland announced that all new homes 

built starting in 2008 must have solar roof panels. In this country, I look 

forward to the day when we take this bold step. Mr. Chairman, we could 

spend the next few hours discussing the fine points of Dr. Mann’s 1998 

and 1999 study, and Dr. Wegman’s analysis of it, or we could focus on 

what is really going on. The Earth’s temperature is rising and has 

reached levels higher than ever recorded. It is true regardless of whether 

you center, de-center, or average the data each and every way you read it 

the conclusion is the same. 

 False logic will not bring us closer to an understanding of the 

scientific truth, so let’s stop politicizing science. Rather, let’s show our 

commitment to our environment which we have a moral and ethical 

obligation to protect. I hope that today we will take steps in that right 

direction but I fear we will not. I yield back, Mr. Chairman. 

 MR. WHITFIELD. Thank you, Ms. Baldwin. I recognize Mr. Stearns 

of Florida. 

 MR. STEARNS. Thank you, Mr. Chairman, and I thank you for 

having this hearing. Listening to the folks on the other side, I would say 

to my colleague from California asking why aren’t we spending our time 

developing legislation, I would say it is probably incumbent upon us as 

Chairman Barton pointed out to find out if the facts are correct. We have 
627

from the last hearing some inquiry that shows there potentially exists 

some dubious research particularly embodied on the hockey stick effect 

that shows a huge global warning in our period. 

 Now if you look at the data and you go to the recent release from the 

National Research Council, Thursday, June 22, 2006, it shows that from 

the period 1400 A.D. to 1900 A.D. were in a little Ice Age, but when you 

go back further back to 1000 A.D. to 1400 A.D. we were in a warm 

period, so is it possible that what we are seeing here is sinusoidal and 

that perhaps we should inquire if this hockey stick graph is the basis for 

this alarm that we should start developing legislation immediately. 

Obviously, it is the centerpiece of movies. It is the centerpiece of 

documents that have been popular, but what it shows is that the 

temperatures were stable in other parts of our period and were much 

higher in the medieval and obviously there was not the human 

population, there was not the gasoline that supposedly is driving this 

warming period now. 

 So I think we owe it to our constituents. We owe it to all the 

Americans to find out if the policy decision for this hockey stick is 

accurate so I think what we are doing today, Mr. Chairman, is just simply 

trying to develop an accurate understanding of what is out there. Now 

we had the hearing last week and we heard from Dr. Wegman. This 

report provided an independent critique of the statistical method of Dr. 

Mann, which shows that his information basically produced the hockey 

stick. Dr. Mann asserted that the increase in the temperatures in the 

Northern Hemisphere in the 20th Century is likely to have been the 

largest of any century during the past 1,000 years. 

 The report also found that 1990 was the warmest decade and 1998 

the warmest year of the millennium. Dr. Mann’s claims are repeated so 

often they are now considered facts, but as often the case with statistics, 

a deeper look at some of these claims show that perhaps there is more 

than meets the eye. Dr. Wegman’s final report found that Dr. Mann 

misused certain statistical methods in his studies which inappropriately 

selected hockey stick shapes in the temperature history. Dr. Wegman 

concludes that Dr. Mann’s work cannot support the claim that the 1990s 

were the warmest decade of the millennium. 

 Specifically, Dr. Wegman found that the temperature proxies used by 

Dr. Mann are incorrectly centered on the mean of the period 1902 to 

1995 rather than on the whole time period. Because the hockey stick 

proxies are centered too low, they will exhibit a larger affected variance 

allowing the graph to exhibit a much more dramatic jump in average 

temperature. The net effect of de-centering in Dr. Mann’s study is to 

produce this hockey stick shape. Centering on the overall mean is a 
628

critical factor in using the principal component of methodology properly 

according to Dr. Wegman. 

 So that is sort of in a nutshell what we have here so by golly, I think 

it is worthwhile to have a second hearing on this, Mr. Chairman, and to 

try to understand what is happening here, and at the same time not be 

overly critical of anybody because in the end all we want is the truth, and 

to understand if we are in an emergency situation or basically we are in a 

period where there are highs and lows in this earth temperature. And, in 

fact, in the report that has come out with the working group of the 

Intergovernmental Panel on Climate Change, which was used in many 

reports, it shows the last 140 years the temperature of the Earth has gone 

up 1.5 degrees Fahrenheit, so that is 140 years. Now that could be 

coming off a cold cycle which means 1.5 degrees Fahrenheit is even 

more negligible. 

 So the question of global warming is something we should look at, 

and I think before we pass legislation or as Ms. Baldwin talked about this 

chattering irrelevance, we should find out what is relevant to the studies 

and if they make sense before we pass legislation. I yield back, Mr. 

Chairman. 

 MR. WHITFIELD. Thank you. The chair recognizes Ms. Schakowsky 

of Illinois. 

 MS. SCHAKOWSKY. Thank you, Mr. Chairman. I find this hearing 

really depressing among other things. There is a sense that somehow 

there is a pretense that what we are engaged in here is some sort of 

scientific-like inquiry but the fact of the matter is that the scientific 

community has reached consensus. You can say anything you want at 

this hearing but that is simply the truth. I want to read something from 

Al Gore’s book but lest you think it is Al Gore’s words it is a statement 

of 48 Nobel Prize winning scientists. It says, “By ignoring scientific 

consensus on critical issues such as global climate change President Bush 

and his Administration are threatening the Earth’s future.” 

 I am not so upset about a waste of time. We do plenty of that around 

here. But I am depressed about it because that is what is at stake here, 

the time that we are spending here. I also just want to say since we are 

getting into this petty he said, you said, back and forth, the charts that Al 

Gore said--he talked about this teacher of his, Dr. Roger Ravelle. It was 

his chart that he first presented. When he showed a chart that looks very 

similar to our hockey stick it was Dr. Lonnie Thompson’s study that he 

was talking about. These have been repeated over and over again. How 

many times, 928 peer reviewed articles dealing with climate change 

published in scientific journals during the previous 10 years, percentage 

in doubt as to the cause of global warming, 0 percent. 
629

 The answer is in. And so it seems to me unless somewhere there, 

and Dr. Wegman already has told us over and over again, he is nearly a 

paleoclimatologist, he is not a climate scientist of any sort, unless 

someone can tell us that the planet is not warming and that it is not that 

the warming, I am sure no one would do that, that the warming is not at 

least in part attributable to human activity then what we should be talking 

about is what we are going to do to address the problem. What do we 

know? We know Greenland is melting. We know that some of our 

districts could be under water. We know that human life as we know it 

could be unsustainable in many ways on this planet. Drought, more 

severe storms, flooding, all the things, not to mention for my littler 

grandchildren that polar bears are drowning and different species of trees 

aren’t going to be there. 

 Look in magazines, the old National Geographics, to look at the 

changing of the trees in the north. This is happening. So why we would 

be spending our time in what may be--fight about it. Fine. Let the 

scientific community do whatever it wants, Dr. Mann and his old study, 

and let Dr. Mann defend himself, but what we should be sitting down 

and doing, what are those strategies that we can employ to decrease the 

effects of global warming so that life as we know--so what if it is 

normal? So what if--but if human activity is contributing to a greater 

than normal warming or even an upswing right now and the life that we 

have established on this planet is in danger then we ought to be thinking 

about the ways that we address this problem. 

 And Mr. Waxman talked about the tobacco companies. Well, we 

have now here on July 27, 2006, ABC News--ever wonder why so many 

people still seem confused about global warming? This is a quote from 

the--the answer appears to be that confusion leads to profit especially if 

you are in some parts of the energy business. One Colorado electric 

cooperative has openly admitted that it has paid $100,000 to a university 

academic who prides himself on being a global warming skeptic. 

Intermountain Rural Electric Association is heavily invested in power 

plants that burn coal, one of the chief sources of greenhouse gases that 

scientists agree is quickly pushing Earth’s average temperature to 

dangerous levels. 

 Scientists and consumer advocates say the co-op is trying to confuse 

its clients about the virtually total scientific consensus on the causes of 

global warming. Now virtually totally scientific consensus. Well, 

maybe we can find one or two more. Maybe we could have a dozen 

more hearings of individuals who want to come in and challenge what is 

the scientific consensus. But I am depressed about it and I am worried 

about it because time is wasting for us to do something constructive 

about this. I thank you, Mr. Chairman. 
630

 MR. WHITFIELD. Thank you. Mr. Bass of New Hampshire. 

 MR. BASS. Thank you, Mr. Chairman. I wasn’t planning to give an 

opening statement but I am kind of warming up to it here. I have been 

somewhat amused listening to these opening statements going back and 

forth like a ping pong ball across the table, and I just have to observe that 

we could sort of divide this debate into four different categories. We 

have the don’t worry, be happy crowd. We have the crowd that believes 

that the world is warming but because we can’t agree on what to do, we 

might as well let the good times roll while we can. Then there is the for 

want of a better word the political crowd that maintains that this whole 

issue is the fault of George Bush, Halliburton, the tobacco companies, 

tax cuts, and failure to raise the minimum wage. 

 Frankly, Mr. Chairman, I think these hearings have been 

constructive. I think they have been logical. I think Dr. Wegman’s 

testimony’s last week was dispassionate, scientific, interesting. I think it 

is great that we have Dr. Mann here today to present another point of 

view. I happen to believe personally that there is a problem of global 

warming in the world and there is a pretty good possibility that that may 

have been caused by the excessive growth of the use of hydrocarbons 

over the last century. I don’t blame Republicans or Democrats or 

tobacco companies or any other entity for it. I think it is an issue that we 

need to address, and we need to address it in a logical fashion, and this is 

the beginning of that process. 

 Now I think if I were a member of the general public I would want to 

have a few questions answered ultimately as a result of this debate. 

Number one, is there a warming trend going on? Number two, is it 

caused by natural sources or by man? Are the oceans getting warmer? 

Are hurricanes getting stronger? Is global warming the reason why 

hurricanes might be getting stronger? The oceans are a CO2 sink. Is 

global warming affecting the ability of the oceans to absorb CO2 and so 

forth? I think that is the logical progression that a hearing such as the 

one that we had last week and what we have today leads to--we don’t 

need to have a hearing that deals with the conclusions before we build 

the evidence. 

 So I want to thank you, Mr. Chairman, for this hearing and as one 

who supports the concept that we need to address this problem I think we 

are moving in the right direction. I yield back. 

 MR. WHITFIELD. Thank you. At this time I recognize Mr. Inslee of 

Washington. 

 MR. INSLEE. This really is pathetically unworthy of America, the 

most technologically oriented society in human history, and we are here 

debating the equivalent of gravity. Literally while America literally 

burns we fiddle. This hearing makes Nero look like a responsible 
631

Roman citizen. And we have got to pull our heads out of the sand in that 

regard. Now the reason is--and I am not depressed like Ms. 

Schakowsky. I am enraged. Since the last hearing if anybody bothers to 

read the newspapers an article comes out showing that 80 percent of the 

mass of the glaciers in my state in North Cascades National Park, one of 

the jewels in the crown, melted. A study comes out yesterday. Highest 

heat loss, 50 deaths in California, and we are sitting here fiddling around. 

 Article comes out yesterday. We have a dead zone in the North 

Pacific where fish are dying because of change in the circulation patterns 

in our oceans. And we sit here and fiddle around. This would be the 

equivalent after the Titanic of the oversight committee having a hearing 

on how they arranged the deck chairs back in that good old day. Now 

why is this so ridiculous? It is ridiculous because there is total scientific 

consensus not only in American but in the world that we are responsible 

in part for the change in the climatic systems of the globe. I would refer 

to a science article that studied 928 peer reviewed articles and not a 

single one of those peer review articles said anything that most of the 

folks on the Majority side want them to say. 

 They all said that every single association in the world that has 

studied this have concluded the climate is changing and humans are 

partially responsible. That includes the American Meteorological 

Society, the American Geo-Physical Unit, the Advancement of Science 

Association, the American Academy of Sciences, and the International 

Panel of Climate Change. And you know what they got here? They got 

nothing. They got nothing to say that those things are not true. We are 

sitting here trying to poke holes in an 8-year old study. You know what 

it is like to me? It is like at the soccer final championship, and you saw 

the head butt by Zidane. He head butted, and everybody says he butted 

him. And they would argue but there was a guy up there in section 23B 

and it didn’t look like a head butt to him, and maybe his eyesight was a 

little bad. 

 The world knows what is going on here, and it is a sham. I want to 

refer to some of the science of this. They know it is a sham if you look 

at this graph up here. Atmospheric concentrations of carbon dioxide are 

going up unassailable. 
632

1

 Next slide, please. 

2

 Our contributions are going up from fossil fuel burning. No question 

about that. Next slide, please. 
633

3

 We see the contributions, the CO2 levels globally over the last 

400,000 years on the top and the temperature at the bottom. What you 

see is that they are very, very closely related. It is an amazing 

relationship. And what you will see at the top if I can get a laser pointer 

to show right up here were 370 PPM. That is higher than any time in the 

last 400,000 years, and what is scary is it is going through the roof. It 

will be double preindustrial times in my lifetime and my children’s 

lifetime. 

 None of this is arguable. All of this is known. And we are going to 

hear discussion today that we have ice core data that I will talk about that 

is independent of Dr. Mann’s research. We have physical evidence of 

changes of oxygen isotopes that prove what is going on, which is we are 

changing the climate of the United States and the world. Next slide, 

please. 
634

4

I just want to show you, this is Antarctic ice core data. The blue 

showing, if I can get my facts straight here, the blue showing 

temperature, the red showing CO2 variations. The relationship is 

incredibly similar. 

 And again if you look where we are going to be during my lifetime 

and my children’s lifetime, we will be right here. We will be almost off 

the charts, and we will be double what we were in preindustrial times. I 

challenge anyone here at this table, and I got an outstanding question for 

all of you in this hearing, you tell me if you double CO2 levels for 

preindustrial levels if you think that is a good idea for America. I want 

all of you tell me if you think that is a good idea. I think it is a really bad 

idea. We ought to start being more the American eagle and less the 

ostrich and we ought to fly with new technology instead of putting our 

head under the sand on this issue and then this commerce committee will 

start helping America. 

 Next slide, please, if I can just show you one more thing. 
635

5

 

This is a picture of ice core. We are sitting here talking about some 

paleoclimatic proxy data, and we are going to spend hours talking about 

it, but the fingerprints, the DNA evidence, is in the air in that core picture 

I am showing you because it is 400,000 year old air. We can directly 

measure the oxygen isotopes that is a direct measurement of the 

temperature. We know what is going on and it is not a pretty picture. 

And I look forward to the day that we start doing something about this 

instead of just having these ridiculous examples and arguing gravity. 

Thank you, Mr. Chairman. 

 One more comment too before I leave just briefly. I noted Mr. 

Barton, my good friend, I congratulate him on the baseball game this 

year, they whooped us again, and I notice he hadn’t seen this movie 

about climate change. I am going to invite Mr. Barton to go see this 

movie with me. I am going to buy him as much popcorn as he wants, 

and I am going to agree to go to any movie he wants to go to from Zorba 

the Greek to Lawrence of Arabia, anything he wants me to see. I think it 

would be good for both of us. Thanks very much. 

 MR. WHITFIELD. Thank you very much. You can see we are a very 

social group. 

 CHAIRMAN BARTON. If I go he is going to have to pay. 

 MR. WHITFIELD. Obviously this is a subject that people feel very 

strongly about, and we are delighted with our witnesses on the first panel 

today. Now it is your turn to talk, and we appreciate you being so patient 
636

while we talked. Our first witness, and I will introduce all of you, Dr. 

Michael Mann who is the Associate Professor and Director of the Earth 

System Science Center at Penn State University, University Park, 

Pennsylvania; Dr. John Christy, Professor and Director of Earth System 

Science Center, University of Alabama in Huntsville; Dr. Ralph 

Cicerone, President of the National Academy of Sciences; Mr. Stephen 

McIntyre of Toronto, Ontario, Canada; Dr. Jay Gulledge, Senior 

Research Fellow, Pew Center on Global Climate Change; and Dr. 

Edward Wegman, Director, Center for Computational Statistics at 

George Mason University. 

 We welcome all of you. As you know, this is an Oversight and 

Investigations hearing, and we do take our testimony under oath, and I 

would ask any of you do you have any objection to testifying under oath? 

Under the rules of the House and rules of the committee you also are 

entitled to legal counsel. I am assuming that none of you have legal 

counsel with you today, but do any of you have legal counsel today? 

Okay. Then if you would stand and raise your right hand, I would like to 

swear you in. 

 [Witnesses sworn.] 

 MR. WHITFIELD. Thank you very much. All of you are now under 

oath. And, Dr. Mann, we will recognize you for 5 minutes for your 

opening statement. 

TESTIMONY OF DR. MICHAEL E. MANN, ASSOCIATE 

PROFESSOR AND DIRECTOR, EARTH SYSTEM SCIENCE 

CENTER, THE PENNSYLVANIA STATE UNIVERSITY; DR. 

JOHN R. CHRISTY, PROFESSOR AND DIRECTOR, EARTH 

SYSTEM SCIENCE CENTER, NSSTC, UNIVERSITY OF 

ALABAMA IN HUNTSVILLE; DR. RALPH J. CICERONE, 

PRESIDENT, NATIONAL ACADEMY OF SCIENCES; MR. 

STEPHEN MCINTYRE, TORONTO, ONTARIO, CANADA; 

DR. JAY GULLEDGE, SENIOR RESEARCH FELLOW, PEW 

CENTER ON GLOBAL CLIMATE CHANGE; AND DR. 

EDWARD J. WEGMAN, DIRECTOR, CENTER FOR 

COMPUTATIONAL STATISTICS, GEORGE MASON 

UNIVERSITY 

DR. MANN. Mr. Chairman, members of the committee, thank you 

for inviting me here to appear before you today. I became a climate 

scientist because the Earth’s climate is a fascinating and complex system 

and understanding how it works is so important. Part of my research has 

involved examining preindustrial climate history in order to learn about 

the natural variations in the Earth’s climate. My research in this field, 
637

not just the initial work that my colleagues and I published in the late 

1990s, but my recent research as well suggests late 20th Century Northern 

Hemisphere average temperatures are unprecedented over at least the 

past 1,000 years. 

 Of course, we have accurate thermometer measurements only back 

about 100 years, and so we estimate climate prior to that period from 

indirect sources called climate proxies such as tree rings, corals, and ice 

cores. This work involves many uncertainties and there are numerous 

judgment calls that must be made. For that reason we are rarely 

categorical in the conclusions that we reach. What is important, 

however, is that the scientific community has reached consensus that 

recent northern hemispheric average warmth appears to be 

unprecedented over at least the past 1,000 years, and that this warmth can 

only be explained by anthropogenic or human influences on the climate. 

 This conclusion is not based on single studies or isolated research but 

is confirmed by many studies using different sets of data and 

independent statistical methods and indeed this conclusion was just 

echoed weeks ago by a report of the National Academy of Sciences, the 

most prestigious nonpartisan scientific body in the Nation. So where 

does my research fit into this? Taken as a whole my own research is in 

accord with the scientific mainstream reflected in the National Academy 

report and elsewhere that there has been unprecedented warming in the 

Northern Hemisphere over the past 100 years. 

 Exhibit A, if you can take a look at Exhibit A there, that shows that 

this conclusion is common to a number of similar studies including two I 

was involved with. This committee is not looking at my work on the 

whole or on the larger body of science on this issue. It is instead 

focusing on the first study of this type my colleagues and I published and 

undertook in 1996 while I was still a graduate student. While there were 

previous reconstructions based on proxy data our study was the first to 

estimate global patterns of past temperature change and the first to 

estimate uncertainties. Our initial study published in the journal, Nature, 

in 1998 was followed by an additional study in the journal, Geophysical 

Research Letters, in 1999. The main conclusion of the 1998 study was 

that there had been unprecedented warming in the Northern Hemisphere 

in recent decades. The 1999 study reinforced this conclusion but also 

reassessed and expanded the uncertainties and added the tentative 

conclusion that it was likely that the 1990s were the warmest decade over 

that thousand year time period and that 1998 was the warmest year. 

 The 1999 study included a graphic depiction of the temperature 

history over the last millennium, which demonstrated an unprecedented 

rise during the 20th Century. Some have dubbed this graphic the hockey 

stick. If the question this committee seeks to answer is whether knowing 
638

what I know today, a decade after starting the original study, my 

colleagues and I would conduct it in exactly the same way, the answer is 

plainly no. The field of paleoclimate reconstruction has evolved 

tremendously over the past decade. 

 Important new proxy data have been developed. Reconstructions 

have been compared with independent estimates from climate model 

simulations and confirmed by those simulations. Statistical methods for 

reconstructing climate from proxy data have been refined and rigorously 

tested, and I have been actively working in each of these areas. This is 

important because all the focus of criticism on our work in the late 1990s 

has been on the statistical conventions we used. My co-authors and I 

have not used those conventions in our later work. 

 The critique goes only to our first reconstruction effort. It does not 

apply to our more recent studies all of which indicate the same basic 

hockey stick result. Exhibit B demonstrates this point. The green 

reconstruction does not use principal component analysis at all so the 

statistical conventions being discussed here have no relevance, and it is 

the same basic reconstruction, if you will, essentially the same “hockey 

stick.” Now our critics do not confront the fact that our basic conclusion 

is not an isolated or aberrational finding reached only in one study. 

Every climate scientist who has performed a detailed reconstruction of 

the climate of the past 1,000 years using different proxy data and 

different statistical methods has come up with the same basic hockey 

stick pattern, that is to say a reconstruction that agrees with our original 

reconstruction within its estimates uncertainties. 

 My critics also fail to recognize that even if their criticisms are 

accepted it has no bearing on the outcome. Dr. Wegman’s report argues 

that the hockey stick pattern derives from the statistical conventions used 

in our 1998 and 1999 studies. However, using alternative statistical 

conventions yields the same hockey stick pattern. The hockey stick 

pattern is intrinsic to the data. That was the conclusion of the National 

Academy. Page 116 of the National Academy report says the statistical 

convention my colleagues and I used “does not appear to unduly 

influence reconstructions of hemispheric mean temperature; 

reconstructions performed without using principal component analysis 

are qualitatively similar to the original curves presented by Mann et al.” 

 This was also the conclusion reached by Dr. Hans von Storch who 

testified here last week, and by four independent teams of scientists who 

published peer reviewed articles considering and rejecting the conclusion 

that the statistical methods used in our early studies were responsible for 

the hockey stick result. Finally, my critics ignore the fact that other 

scientists have repeated original results using the centered PCA analysis 
639

that Dr. Wegman favors and have concluded that the result is basically 

the same as we originally reported. This is summarized in Exhibit C. 

 So even if one accepts as valid the criticisms about the statistical 

conventions used in our early work our results are essentially unaffected. 

As you can see, the two curves are barely distinguishable within the 

width of the lines that are shown. And as I have said before our key 

conclusion that recent hemispheric warmth appears unprecedented over 

at least the past millennium has been confirmed by every study that has 

examined the same question. 

 Finally, it is worth expressing again that paleoclimate reconstructions 

represent just one of many independent lines of evidence that support the 

conclusion that human activity is already having a substantial impact on 

global climate. I appreciate this opportunity to answer the committee’s 

questions. I am sorry I could not be here last week but as I had explained 

to committee staff, I had to take care of my infant daughter while my 

wife was attending a conference. 

 [The prepared statement of Dr. Michael E. Mann follows:] 
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PREPARED STATEMENT OF DR. MICHAEL E. MANN, ASSOCIATE PROFESSOR AND DIRECTOR,

EARTH SYSTEM SCIENCE CENTER, THE PENNSYLVANIA STATE UNIVERSITY
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 MR. WHITFIELD. Dr. Mann, thank you. You have heard all the bells 

going off. We do have a series of four votes on the floor but before we 

go, Dr. Christy, I am going to ask you to give your opening statement. 

Then we will recess for probably about 30 minutes and we will come 

back and take the rest of the testimony. 

DR. CHRISTY. Thank you. Chairman Whitfield, Ranking Member 

Stupak, and committee members, I am John Christy, Director of the 

Earth System Science Center at the University of Alabama in Huntsville, 

and the Alabama state climatologist. I served as a lead author of IPCC 

2002 chapter on observations with Dr. Mann, and as panelist on the NAS 

report on temperature reconstructions. As the lead author of the IPCC, I 
652

helped craft the now infamous statement about the 1990s and 1998 being 

the warmest decade and year. 

 Our confidence was described as likely rather than very likely or 

virtually certain. In other words, we chose a relatively low level of 

confidence because of the following concerns known at that time. First, 

that the hockey stick was new and had not had time for independent 

analysis for confirmation or revision. Two, a key factor or a key anchor 

for that early part of the record was a western tree ring series that 

explained only about 5 percent of the overall variability. And, three, that 

the unavoidable constraints on the length of the calibration and validation 

periods really prevented confident knowledge of the relative warmth of 

different centuries. 

 A more disappointing aspect of the IPCC regarding temperatures 

over the last millennium was that some important work was not included, 

specifically the work of Dahl-Jensen et al., 1998, which I recommended 

for inclusion many times, was completely missing from this section. 

These borehole temperatures from Greenland represented probably the 

most reliable regional temperatures over the last millennium. Thus, in at 

least one location we had high confidence that it was warmer 1,000 years 

ago, and though Greenland’s temperature may not be tightly connected 

to hemispheric averages, Greenland is important for sea level averages. 

If Greenland were warmer in the relatively recent past were its edges also 

melting as they appear to be now under cooler conditions? I believe the 

IPCC missed an opportunity to demonstrate climate complexity by 

excluding this information in 2001. 

Dr. Roy Spencer and I created the first satellite-based data set 

temperature back in 1990. We are now working on improvements to the 

8th revision brought about by the divergence of the two most recent 

satellites. 

 When asked by others, we provided sections of our code and relevant 

data files. By sharing this information, we opened ourselves up to 

exposure or a possible problem which we had somehow missed, and 

frankly this was not personally easy. On the other hand, if there was a 

mistake we wanted it fixed. Not knowing the outcome of the work done 

by scientists at Remote Sensing Systems they asked if they could publish 

what we had sent them. In my formal scientific response, I wrote, “Oh, 

what the heck. I think it would be fine to use and critique, that is sort of 

what science is all about.” 

 And so it was that in August 2005 RSS published a clear example of 

an artifact which created errors in the tropics in our data. In Science

magazine the following November we published the information about 

our now-corrected temperatures and expressed our gratitude to RSS for 

discovering our error. While a bit painful, this process as recommended 
653

in the National Academy’s report, resulted in progress and better 

scientific information. 

 Finally, greenhouse gas concentrations are increasing, and therefore 

the radiation budget of the atmosphere will be altered. In response, the 

surface temperatures will or should rise. Our observational work, 

however, has not been able to show clear support for the manner or 

magnitude of this response as depicted by current climate models. For 

policy makers this is important. For example, we cannot reliably 

reproduce or predict the climate for large regions within the United 

States. It would be a far more difficult task to reliably predict the effects 

of a policy that reduce greenhouse gas emissions. 

 Simply put, we cannot say with any confidence to you or to the 

American taxpayer that by adopting policy X we will cause an impact Y 

on the weather of the climate system. 

What I really find disturbing today is the demonization of energy and 

its most common byproduct, carbon dioxide, CO2. I cannot call CO2 a 

pollutant when it is a source of life on the planet. CO2 is plant food. 

But, as importantly, the extra CO2 we have put in the air represents 

astounding improvements in the health, longevity, and quality of human 

life. I suspect half of us in this hearing room would not be here but for 

the benefits wrought by affordable energy. Energy use is not evil. 

 I believe my experience in Africa is important in this whole 

discussion of energy and climate. In the 1970s I taught science and math 

as a missionary teacher, and I saw the energy system there. The energy 

source was wood chopped from the forest. The energy transmission 

system was the backs of women and girls hauling wood an average of 

three miles each day. The energy use system was burning the wood in an 

open fire indoors for heat and light. The consequence of that energy 

system was deforestation and habitat loss while for people it was poor 

respiratory and eye health. The U.N. estimates 1.6 million women and 

children die each year from the effects of this indoor smoke. 

 Energy demand will grow, as it should, to allow these people to 

experience the advances in health and quality of life that we enjoy. They 

are far more vulnerable to the impacts of poverty, water pollution, and 

political strife than whatever the climate does. I simply close with a 

plea, please remember the needs and aspirations of the poorest among us 

when energy policy is made. Thank you very much. 

 [The prepared statement of Dr. John R. Christy follows:] 
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PREPARED STATEMENT OF DR. JOHN R. CHRISTY, PROFESSOR AND DIRECTOR, EARTH 

SYSTEM SCIENCE CENTER, NSSTC, UNIVERSITY OF ALABAMA IN HUNTSVILLE
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 MR. WHITFIELD. Dr. Christy, thank you. We are going to go vote. 

It is now 15 after 3:00 so we will reconvene about 15 till 4:00. Down in 

the basement there is a little snack center and if you go out the main first 
670

floor of the Rayburn Building and walk over to Longworth there is a 

wonderful ice cream shop so whatever you decide to do. 

 [Recess.] 

 MR. WHITFIELD. The hearing will reconvene, and we apologize for 

the delay. We are about 35 minutes later than we said. But, Dr. 

Cicerone, you are recognized for your 5-minute opening statement. 

DR. CICERONE. Thank you, Chairman Whitfield and members of the 

committee. My name is Ralph Cicerone. I am President of the National 

Academy of Sciences and Chairman of the National Research Council. 

Prior to this year, I was Chancellor of the University of California at 

Irvine where I was Aldrich professor in Earth System Science and also 

professor of chemistry. This afternoon I will summarize the state of 

scientific understanding on climate change very briefly, based on 

findings and recommendations in NAS and NRC reports and in some 

recent refereed publications. Our reports, quite often written with the 

National Academy of Engineering and the Institute of Medicine, go 

through a peer review process and although we are not part of the 

Government, we were chartered by Congress and President Lincoln to 

provide advice on matters of science and technology. 

 I would like to first start with how is it that humans can influence the 

climate of an entire planet. The strongest answer is the greenhouse effect 

which is a natural phenomenon. Without the natural greenhouse effect, 

the Earth would be much colder than it is right now. We can test that 

prediction by looking at Mars and Venus, for example. Now humans are 

amplifying the natural greenhouse effect. Just to give you one major, the 

extra energy trapped near the earth’s surface by a variety of greenhouse 

gases is about 2-1/2 watts per square meter now, which is about 100 

times larger than all the energy usage by humans worldwide on the entire 

planet from all sources, fossil fuels, nuclear wind, hypothermal, you 

name it. It is a big number. This is what gives humans leverage to 

influence an entire planetary climate. 

 There is no doubt that the Earth is warming. Weather station records 

and ship-based observations show that the global average surface 

temperature in the air has increased by about 1.2 degrees Fahrenheit 

since the beginning of the last century, more than half of the increase 

since 1975. Scientists have also measured upward temperature trends in 

the lower atmosphere and in the upper oceans, and this continuing 

warming has been accompanied by worldwide changes and many other 

indicators, such as decreases in Arctic sea ice thickness and extent, and 

shifts in ecosystems. 

 What is the primary evidence for this widely accepted view that 

global warming is occurring, that human beings are responsible at least 

in part for the warming and that the Earth’s climate will continue to 
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change during this current century. There are many lines of evidence. 

Let me summarize them briefly. First, measurements show large 

increases in carbon dioxide and other greenhouse gases, such as methane 

and nitrous oxide, beginning in the middle of the 19th Century. These 

increases in greenhouse gases are due to human activities such as 

burning fossil fuel for energy, agricultural and industrial processes, and 

so forth. The concentration of carbon dioxide is now at its highest level 

shown by actual measurements in the last 650,000 years. The record has 

been extended back that far now. 

 Second, we understand how carbon dioxide and other greenhouse 

gases physically affect global temperature. Rigorous radioactive transfer 

calculations of the temperature changes due to increasing greenhouse gas 

concentrations, together with reasonable assumptions about climate 

feedbacks provide a physically based mathematically sound explanation 

for the observed warming. 

 Third, state-of-the-art mathematical climate models are able to 

reproduce the warming of the past century, but only if human-caused 

greenhouse gases are included. Fourth, and I did not have this in my 

written testimony, but simulations of the stratospheric penetrating 

volcano, Mount Penatubo, in mid-June 1991 were able to show the exact 

timing of the cooling that took place afterwards based on the sulphate 

particles and got the magnitude of the cooling almost right. And these 

were primitive models at the time. Models have improved a great deal 

since. 

 Fifth, analysis of high-quality, precise measurements of the sun’s 

total brightness over the past 25 years show little, if any, change in the 

long-term average of solar output over this time period. Thus, changes in 

the sun, the best explanation for a natural explanation cannot explain the 

warming over the past 25 years. 

Six, the oceans have warmed in recent decades and the stratosphere 

has cooled. Land masses north of the tropical region in the Northern 

Hemisphere have warmed even more than the oceans. All of these large 

scale changes, their sizes and patterns are consistent with the predicted 

geographical and temporal pattern of greenhouse surface warming. 

 Seventh, ice covered regions of the Earth have experienced 

significant melting. For example, the average annual sea ice extent of 

the Artic has decreased by about 8 percent or nearly a million square 

kilometers over the past 30 years. Sea ice thickness measured, for 

example, by the United States Navy has decreased over the period. 

Measurements from Earth orbiting satellites from synthetic aperture 

radars and from Earth’s gravity sensors over the last few years have 

shown that both Greenland and West Antarctic ice sheets are losing ice. 
672

 Eighth, several publications in the last 2 years show that hurricane 

intensities have increased in some parts of the world in lock step with sea 

surface temperatures. 

While we are quite certain that the Earth’s surface has heated up 

during the last 30 years, and that it is hotter now than at any time during 

the last 400 years, predicting what will happen to important climate 

variables besides temperature is more difficult. 

 As we stated in our 2001 report climate change simulations yield a 

globally averaged surface temperature increase by the end of this century 

of maybe 2-1/2 to 10 degrees Fahrenheit. As I said, temperature is easier 

to predict than other changes such as rainfall, storm patterns, and 

ecosystems, and the prediction of extreme events, which is what 

probably humans and other biological creatures respond to the most are 

very difficult. 

 While these future climate changes and their impacts are inherently 

uncertain, they are far from unknown. We can paint useful broad brush 

pictures now of how global warming may affect certain regions of the 

world. For example, these mathematical models generally project more 

warming in continental regions than over the oceans and in polar regions 

rather than near the equator. Precipitation is expected to increase in the 

tropics, decrease in the subtropics, and increase in the midlatitudes. 

Rainfall is expected to increase in monsoon regimes. We can give a lot 

of broad brush predictions like that that are difficult to prove, but that is 

the state of the science now. 

 Even if no further increases in the atmospheric concentrations of 

greenhouse gases occur, which would be a difficult to achieve scenario, 

we are very likely to experience additional warming of about 7/10ths of a 

degree Fahrenheit in the coming decades. In colder climates such 

warming could bring less severe winters and longer growing seasons if 

soil moisture is adequate. Several studies, quite credible, have projected 

that summertime ice in the Arctic could disappear in this century, the end 

of the century. 

 The combined effects of ice melting and sea water expansion from 

ocean warming will likely cause the global average sea level to rise by 

anywhere between 1/10th and 9/10ths of a meter in this century. So 

coastal communities will experience increased flooding due to seal level 

rise and are likely to experience more severe storms and storm surges. 

And of course increased acidification of the surface ocean due to the 

added carbon dioxide from the atmosphere is occurring. It will continue 

and it will harm marine organisms such as corals and some plankton 

species. 

 In summary, there are multiple lines of evidence supporting the 

reality of and human roles in global climate change. I think I will stop 
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there to be as brief as possible. With your permission, Mr. Chairman, I 

have submitted two appendices. 

 [The prepared statement of Dr. Ralph J. Cicerone follows:] 
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PREPARED STATEMENT OF DR. RALPH J. CICERONE, PRESIDENT, NATIONAL ACADEMY OF 

SCIENCES
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 MR. WHITFIELD. Well, thank you so much, and your entire 

statement is part of the record, and we appreciate your being here. Mr. 

McIntyre, you are recognized for 5 minutes. 
680

MR. MCINTYRE. Thank you. Good afternoon, Mr. Chairman, and 

members of the committee. My name is Stephen McIntyre. I appreciate 

the invitation to appear before you once again. I will recap my testimony 

from last week, referring to the NAS and Wegman reports. The Wegman 

report drew attention to a remarkable lack of independence in data used 

in supposedly independent studies. Some proxies are used in nearly 

every such study. This raises the spectre that problems in one proxy can 

spill over to multiple reconstructions. 

 One such problem has already been identified. The NAS panel 

agreed that strip bark bristlecones should be avoided in temperature 

reconstructions but they did not assess the potential impact of this 

conclusion. Last week I showed that this recommendation reversed the 

estimates of medieval modern levels in the Crowley and Lowery 

reconstruction. Here we show the impact of this on the Mann study, 

where the conclusion of 20th Century uniqueness does not withstand 

removing the bristlecones. Every reconstruction using bristlecones will 

have to be reconsidered in the light of thee NAS recommendation. 

 By coincidence the key bristlecone sites are located in an area 

recently studied by Dr. Christy where he recompiled high altitude 

temperature data. There is actually a slight negative correlation between 

Christy’s temperature data and Mann’s key principal component series. 

You can readily see why the NAS panel said that bristlecones should be 

avoided as a temperature proxy. Further grounds for concern about the 

use of this data comes from fossil trees located well above modern tree 

lines in this area, dated to the Medieval Warm Period. Recent ecological 

niche studies have concluded that the annual minimum temperatures in 

this area were 3.2 degrees Centigrade warmer, that is 6 degrees 

Fahrenheit warmer, than at present. 

 Dr. Mann likes to say that any problems do not arise simply, and I 

emphasize simply, from the flawed PC method. If the proxies were 

ideal, such as the synthetic data studied by von Storch and Zorita, the bad 

method may not make a difference. But in such circumstances a simple 

average would also have a hockey stick shape which were not observed 

in the simple average of the Mann proxies. The real problem, and the 

one observed by Wegman, is that the PC method as applied to low 

quality data caused a minor pattern, in this case bristlecones, to be 

exaggerated as a dominant pattern in worldwide climate. 

 Notably, Dr. Mann’s testimony does not mention bristlecones but in 

his data, the hockey stick shape is dependent on them. The graph here 

shows in red the contribution to his reconstruction for bristlecones. The 

other colors show the contribution from other classes of proxies. As you 

can see, there is very little information from the other proxies. 
681

 Dr. Mann has also said that he can get a hockey stick shape in 

another way. There are many ways of processing Mann’a data set. 

Some result in hockey stick shape series, some do not. Burger and 

Cubasch in 2005 showed a bewildering variety of outcomes based on a 

slight variation in methodology. Sometimes you are told that scientists 

have moved on, and that the criticized methods are no longer used. This 

is not the case. All of Dr. Mann’s more recent work used his disputed 

PC1. Mann’s PC1 was used in the prominent article, Osborne and Briffa 

2006, and even occurs illustrated as a temperature proxy in one of the 

NAS illustrations. 

 An important control on any statistical study is reporting of adverse 

results. The verification r2 statistic is commonly used in paleoclimate 

studies and was said in the original article to have been considered. 

However, early periods of the reconstruction failed the significance test, 

a fact which was never reported. At the NAS press conference, Dr. 

Bloomfield said that he found nothing unusual about MBH reporting. If 

paleoclimate research practices do not require scientists to disclose 

results adverse to their claims, then this reduces the ability of policy 

makers to rely on these studies. 

 Last week I pointed out many problems with data and code access. 

Much relevant Mann data did not become available until 2004, 6 years 

after the original study, and then only after a formal complaint to Nature. 

Mann’s archiving practices are by no means the worse in the community. 

Much of Lonnie Thompson’s data remains unarchived 20 years after it 

was collected. The efforts of your committee led to Dr. Mann disclosing 

a considerable amount of source code. Unfortunately, the source code 

does not operate with the data as archived and it does not include code 

for important steps such as the calculation of confidence intervals or PC 

retention rules. 

 Wahl and Ammann have been described as independent studies but 

they are co-authors and collaborators with Dr. Mann and their efforts, 

whatever their merit, can hardly be described as independent. To the 

credit of Wahl and Ammann, they have archived their code for their 

study following a practice that we followed. Their code reconciles to 

ours and any differences between the studies do not arise from differing 

arithmetic. 

 The interest of this committee in reconstruction seems to have been 

prompted in part when Dr. Mann was quoted by the Wall Street Journal

as saying that he would “not be intimidated into disclosing his 

algorithm.” Such attitudes are inconsistent with the requirement of 

policy makers if they are to rely on such studies. If you are to rely on 

paleoclimate studies you should be concerned about disclosure, data 

access, and replication because, first, peer review at journals is very 
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limited and does not constitute sufficient due diligence for policy 

reliance. 

 Second, IPCC does not carry out independent testing or verification. 

Third, to enable and facilitate independent testing, paleoclimate research 

needs to achieve dramatically improved standards for archiving data and 

code. Fourth, because much of the work is funded by the U.S. Federal 

government, improved administrative practices by NSF and DOE could 

make a direct and immediate impact and improvement. Thank you. 

 [The prepared statement of Stephen McIntyre follows:] 

PREPARED STATEMENT OF STEPHEN MCINTYRE, TORONTO, ONTARIO, CANADA

SUMMARY 

1. little reliance can be placed on the original MBH reconstruction, 

various efforts to salvage it or similar multiproxy studies, even ones 

which do not use Mann’s principal components methodology; 

2. peer review as practiced by academic journals is insufficient due 

diligence for policy reliance. IPCC reports are only a literature review 

rather than independent due diligence.

3. to enable and facilitate independent testing, paleoclimate research 

practices need to achieve dramatically improved standards for 

archiving data and code. 

4. administrative policies governing work directly funded by the U.S. 

government can make a direct and immediate difference.

Good morning, Mr Chairman and members of the Committee. 

My name is Stephen McIntyre. I appreciate the invitation to appear before you once 

again. I will recapitulate my testimony from last week, making further reference to the 

NAS and Wegman reports. 

The Wegman report drew attention to a remarkable lack of independence in the 

proxies used in supposedly “independent” studies. Some sites are used in nearly every 

study. This raises the spectre that problems with one proxy can spill over to multiple 

studies. One such situation has already been identified. The NAS panel agreed that stripbark bristlecones should be “avoided in temperature reconstructions”. Last week, we 

showed that this reversed medieval-modern levels in the Crowley and Lowery 2000 

reconstruction. Figure 1 below shows the impact on MBH, where conclusions of 20th

century uniqueness do not withstand removing the bristlecones. Wegman showed that 

bristlecones were used in multiple studies and each one will have to be reconsidered in 

light of the NAS recommendation. 
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Figure 1. MBH99 reconstruction and estimate of MBH99-type reconstruction without 

bristlecones. 20-year gaussian smooth.

By coincidence, the key bristlecone and foxtail proxies that establish the pattern in 

Mann’s critical PC series are located in almost the exact area studied by Christy, as 

shown in the location map on the left. As you see, there is little correlation on either a 

smoothed or unsmoothed basis – actually a slight negative correlation – between 

temperature and Mann’s PC1. You can readily see why the NAS panel said that this data 

should be avoided as a temperature proxy. 

Figure 2. Left - location of foxtail and bristlecone sites in the Sierra Nevada and White 

Mountains. Right - Black – annual mean of maximum and minimum temperatures (data, 

Christy, pers. comm.); red – MBH98 NOAMER PC1. 

Further grounds for concern about using Mann’s PC1 as a temperature proxy comes 

from the evidence of fossil trees well above modern tree lines, dated to the Medieval 

Warm Period. Millar et al. 2006 concluded that annual minimum temperatures in this 

area were then significantly warmer (+3.2 °C) than at present. 
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Figure 3. A dead trunk above current treeline from a foxtail pine that lived about 1000 

years ago near Bighorn Plateau in Sequoia National Park. 

Dr Mann likes to say that any problems do not arise simply from the flawed PC 

method. However, it’s not true that the flawed PC method has nothing to do with the 

problems. A simple average of Mann’s proxies does not yield a hockey stick shaped 

series, as shown in Figure 4 below. If you have proxies of ideal quality, even a bad PC 

method can yield meaningful results – which is what von Storch and Zorita observed, 

using idealized data generated in a climate model. However, the problem is that Mann’s 

PC method was applied to low-quality data, where the flawed method caused a minor 

pattern in bristlecones to be exaggerated as a “dominant pattern” in worldwide climate. 

Figure 4. Left: Top – Average of all 415 MBH proxies; bottom – MBH reconstruction. 

Both in standard deviation units. 

In the MBH data set, the hockey stick shape is dependent on the bristlecones. All the 

statistical salvage jobs Dr. Mann cites are variations on schemes to load the final weight 

on the very data the NAS panel said should not be used. 
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Figure 5. Top – Contribution (deg C) of proxy groups (proxy type x continent e.g. Asian 

tree rings; South American ice cores) to the MBH reconstruction, with bristlecones and 

foxtails in red. Bottom – Same series in standard deviation units. The bristlecone 

contribution closely matches the final MBH reconstruction.

There are many ways of processing the MBH data – some result in hockey-stick 

shaped series; some do not. Bürger and Cubasch 2005 showed a bewildering variety of 

outcomes based on slight variations in MBH methodology. 

Figure 6: Different MBH-type results from slight methodological differences from 

Burger and Cubasch [2005] SI Figure 1.

Sometimes you’re told that scientists have “moved on” and that the methods 

criticized by Wegman and the NAS panel are no longer used. However, this is not the 

case. Rutherford et al., coauthored by Dr Mann and published in late 2005, used the 

identical PC method as the 1998 paper. 
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Although 415 individual proxy series were used, data reduction by using 

leading PCs of tree-ring networks results in a smaller set of 112 indicators in 

the multiproxy–PC network available back to 1820 (Fig. 1a), with a decreasing 

number of indicators available progressively further back in time. Twenty-two 

of the indicators (representing 95 individual proxy series) extend back to at 

least A.D. 1400. 

Mann’s PC1 was also used in Osborn and Briffa 2006. And despite criticisms of the 

PC methodology by the NAS panel, they themselves used it, perhaps inadvertently, in 

one of their illustrations as a temperature proxy – see the top panel of Figure 6 of the 

NAS report. 

An important control on any statistical study is reporting of adverse results. The 

verification r2 statistic is commonly used in paleoclimate studies and was said to have 

been considered in MBH98. However, its early periods had insignificant values of this 

statistic, a fact that was never reported. At the NAS press conference, Dr Bloomfield said 

that he found nothing unusual about reporting of results in MBH. If paleoclimate research 

practices do not require scientists to disclose results adverse to their claims, then this 

reduces the ability of policy-makers to rely on these studies. 

Source: Wahl and Ammann 2006. 

Last week, we pointed out many problems with data and code access in 

paleoclimate. In the MBH case, much relevant data did not become available until the 

2004 corrigendum, 6 years after the original study, and only then after a formal complaint 

to Nature. The efforts of your committee led to Dr Mann disclosing a considerable 

amount of source code. Unfortunately, as Dr Wegman reported to you, the source code 

does not work with any data sets presently archived and is inoperable. It also does not 

include code for some important steps, such as MBH99 confidence intervals or PC 

retention rules, which neither ourselves nor Wahl and Ammann have been able to 

replicate. Since Wahl and Ammann are recent coauthors and collaborators with Mann, 

their efforts hardly can be described as “independent” replication. 

Dr Mann and his associates are by no means the worst in the paleoclimate field in 

archiving data. It is undoubtedly frustrating for Dr Mann to be the center of attention 

when many of his colleagues are much worse. For example, despite over 2 years of effort, 

I have been unsuccessful in learning what sites were used in one of three paleoclimate 

studies illustrated in the IPCC Third Assessment Report (Briffa et al 2001). These sites 
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were recently been used by Mann and coauthors, who have also failed to even disclose 

the location of the sites. 

The reason why data access and replication should be of concern to you is that: 

(1) peer review at journals is very limited and does not constitute sufficient due 

diligence for policy reliance; 

(2) IPCC does not carry out due diligence on articles. 

(3) In order to properly assess a study, it needs to be replicated. Placing obstacles 

in the way of access to data and code makes this either impossible or simply 

impractical for people with less than infinite patience. 

(4) Because much of the work is funded by the U.S. federal government, there are 

direct and practical steps that can be taken with NSF and DOE that would have 

an immediate impact in improving the quality of due diligence in this field. 

1

Presentation to the 

Subcommittee on Oversight and 

Investigations of the 

House Energy and Commerce 

Committee.

Stephen McIntyre

Toronto Ontario

Washington DC, July 19, 2006.
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2

NAS Panel Recommendation on 

Bristlecones Affects MBH

Figure 1. MBH99 reconstruction and estimate of 

MBH99-type reconstruction without bristlecones. 

20-year gaussian smooth.

3

Up-to-date temperature data from Sierra 

Nevadas shows no correlation of key MBH 

PC indicator to temperature

Left - location of foxtail and bristlecone sites in the Sierra Nevada and 

White Mountains, California. Sheep Mountain is denoted SHP. Right -

Black – annual mean of maximum and minimum temperatures (data, 

Christy, pers. comm.); red – MBH98 NOAMER PC1.
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4

MWP annual minimum temperature in the 

California Sierra Nevadas estimated to be 

+3.2 °C warmer than at present

Left: A dead trunk above current 

treeline from a foxtail pine that lived 

about 1000 years ago near Bighorn 

Plateau in Sequoia National Park.

5

PCs matter: a simple average of MBH 

proxies does not yield a hockey stick

Top: average of MBH proxies. Bottom: result of MBH method. 
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6

MBH Methods enhance weighting of 

bristlecones – a proxy rejected by NAS 

Top – Contribution (deg C) of 10 proxy groups (proxy type x continent e.g. 

Asian tree rings; South American ice cores) to the MBH reconstruction, 

with bristlecones/foxtails in red. The bristlecone contribution closely 

matches the final MBH reconstruction.

Bottom – Same series in standard deviation units.

7

New research in late 2005 showed 

that a bewildering variety of results 

can be obtained from MBH proxies. 

Source: Bürger and Cubasch SI Figure 1
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8

Moving On?: Precisely the same PC 

series were used late last year in 

Rutherford et al 2005

“Although 415 individual proxy series were 

used, data reduction by using leading PCs of 

tree-ring networks results in a smaller set of 

112 indicators in the multiproxy–PC network 

available back to 1820 (Fig. 1a), with a 

decreasing number of indicators available 

progressively further back in time. Twenty-two 

of the indicators (representing 95 individual 

proxy series) extend back to at least A.D. 

1400.”

9

MBH Results Failed Verification r2 Test

Source: Wahl and Ammann 2006
692

10

Replication Problems Persist

| MBH source code provided to Committee does 

not work with any data sets presently archived 

and is inoperable. 

| code for some important steps, such as MBH99 

confidence intervals or the application of 

Preisendorfer’s Rule N, was not provided

| Other authors are even worse: identity of sites 

in Briffa et al 2001 (also used in Rutherford et al 

2005) remain unreported and unavailable

11

You can make a difference ...

| peer review at journals is very limited and is 

insufficient due diligence for policy reliance; 

| IPCC does not carry out due diligence on articles;

| to enable and facilitate independent testing,

paleoclimate research practices need to achieve 

dramatically improved standards for archiving data 

and code;

| Because much of the work is funded by the U.S. 

federal government, administrative changes at NSF 

and DOE would have an immediate impact on 

paleoclimate due diligence.
693

12

End of Presentation

Sir John Houghton at press conference releasing IPCC Third 

Assessment Report.

 MR. WHITFIELD. Thank you. Dr. Gulledge, you are recognized for 5 

minutes. 

DR. GULLEDGE. Thank you, Mr. Chairman, Ranking Member, and 

members of the committee. I am Jay Gulledge. I am a Senior Research 

Fellow with the Pew Center on Global Climate Change, and an Adjunct 

Assistant Professor at the University of Louisville, where I conduct 

research on the carbon cycling. I just want to try to provide a little bit of 

context here today. I am not a paleoclimatologist or a statistician, but I 

am a professional scientist observing--I am a generalistic climate change 

scientist through my duties at the Pew Center on Global Climate Change. 

 [Slide] 

 Next slide, please. I just want to reiterate, now Dr. Cicerone 

mentioned most of these things, but this is not about the fundamentals of 

climate change science and the hockey stick reconstruction is not a 

foundation. Chain activities are increasing greenhouse gases. The Earth 

is warming. These are unequivocal facts. The warming over the past 5 

decades has been attributed through sound science to human activities 

associated with greenhouse gases. The effects of warming are being seen 

today all over the globe, and this warming is going to continue for a long 

time even if we stabilize greenhouse gases in the atmosphere today. 

Next slide. 

 [Slide] 
694

 Now the main points I want to make today, the so-called hockey 

stick controversy is not a scientific construct. The controversy is in 

science and that is because debate is normal in science and people reexamine each other’s methods and so forth. This is not controversial. It 

is just not controversial in science. The criticisms of the hockey stick 

scientifically speaking do not undermine the climate, the science of 

climate change. It is just not central to our understanding of it. 

 The results of the hockey stick actually represent a gradual 

development in the understanding in the paleoclimate community of past 

climate, not any kind of step change in the understanding. This is readily 

demonstrated from the scientific literature over the past 20 years. And in 

my opinion climate change assessments are working well under the 

supervision of climatologists. 

 [Slide] 

 The next slide, I just want to point out the bottom quote here from 

the NAS report that says the surface temperature reconstructions I have 

included such as the hockey stick are consistent with other evidence of 

global climate change and can be considered, and this is the operational 

phrase here, my point, as additional supporting evidence. It is not central 

to climate science. Next slide. 

 [Slide] 

 This is the hockey stick as presented in the 2001 IPCC. It is a 

reconstruction of the average northern hemispheric temperature over the 

last thousand years. Next slide. 

 [Slide] 

 And the main conclusions as you have heard over and over again the 

20th Century is the warmest in the past thousand years. The 1990s were 

the warmest decade, and even 1998 being the warmest year as 

represented by the blade of the hockey stick here. Next slide. 

 [Slide] 

 Now the criticisms that have been discussed in this hearing as 

leveled by McIntyre and McKitrick have to do with statistical 

methodology and whether they were applied properly, inappropriate use 

of data, and a general complaint that this has resulted in an incorrect 

elimination of the Medieval Warm Period which would show where the 

red oval is here. Next slide. 

 [Slide] 

 Now as a result of these criticisms this committee has asked Mr. 

Wegman to produce a report along with his colleagues to examine these 

criticisms. And the primary objective of this report, as quoted from the 

report, is to “reproduce the results of McIntyre-McKitrick nor to 

determine whether the criticisms were valid and have merit.” I put in red 
695

the last phrase. I think this has not been accomplished by the Wegman 

report at all, and I will illustrate why. Next slide. 

 [Slide] 

 It just seems reasonable that you got to look at what has happened 

since this because you are trying to find out the reliability of the science 

here. Second, Mann’s claims that McIntyre and McKitrick didn’t apply 

his method correctly are not addressed in the Wegman report at all but 

they certainly are germane. If those criticisms are being used to question 

the work then that has to be examined. Corroborating evidence wasn’t 

looked at. That was the strength of the NAS report, I would say. And 

finally in red here a very important report with regard to the questions of 

this committee was really overlooked by this report showing up only in a 

footnote on a later page or on a middle page. 

 But this thing, this study by Wahl and Ammann from the National 

Center of Atmospheric Research, actually looked at all the main 

criticisms of the McIntyre-McKitrick papers, and whether they are 

correct or not, this should have been examined by any investigation 

wanting to look into the merits of the McIntyre-McKitrick criticisms. 

Next slide. 

 [Slide] 

 Now what they are showing is that they are able to reproduce 

extremely closely the original Mann 1998 hockey stick. Here in gray is 

the original Mann result, and if you can’t see it it is because it is under 

the red line, which is their emulation. They did this writing their own 

code in the R programming language, and they made a very faithful 

reproduction. Next. 

 [Slide] 

 Now using their reproduction they then tested whether or not the 

McIntyre-McKitrick criticisms had an effect on the result of the 

reconstruction. In this figure they have corrected for the de-centering 

problem prior to the PC analysis, and also they removed the gaspe tree 

ring series that was questioned by McIntyre and McKitrick. And the 

result is the only change that occurred that has any significance is in the 

14th Century. You see the red line is their emulation of Mann and the 

blue, which is sticking up a little bit on the very left hand of the graph, is 

the effect of the corrections. 

 Now this really just doesn’t change--and these green and magenta 

are the 95 percent confidence intervals. This really just doesn’t change 

the picture of the 20th Century being unique. Now it does leave the 

impression that perhaps there is a trajectory of warming as you move 

back in time. Maybe that continues to go up and the Medieval Warm 

Period, which isn’t even shown here, maybe got warm. Next slide, 

please. 
696

 [Slide] 

 I asked Dr. Ammann yesterday whether or not he had used these 

corrections and taken them back in time. He said that he had, that he has 

a paper that is submitted for review on this, and I want to make clear that 

this hasn’t been peer reviewed yet. It is the same correction applied to 

the data going back a thousand years, and this is the result. The blue line 

is the emulation of Mann 1999. The red line is the result. And in fact it 

does not continue to go up. And this is going to be my last slide so don’t 

be concerned. There are a lot more slides in your handout. I want to 

point out here that if you look at the medieval times here which would be 

the first couple of frames from the left in that graph it is warmer than 

what you see to the right of that. There is a Medieval Warm Period on 

this graph. It is just weak, and that is completely consistent with the 

scientific examination of paleoclimate over the last 20 years. There has 

been a consistent trajectory and this is completely consistent with that. 

Thank you. 

 [The prepared statement of Dr. Jay Gulledge follows:] 

PREPARED STATEMENT OF DR. JAY GULLEDGE, SENIOR RESEARCH FELLOW, PEW CENTER 

ON GLOBAL CLIMATE CHANGE

Mr. Chairman, Ranking Member, and Members of the Committee: 

Thank you for the opportunity to speak today. I am Jay Gulledge, Ph.D., Senior 

Research Fellow for Science and Impacts at the Pew Center on Global Climate Change. I 

am also an Adjunct Assistant Professor at the University of Louisville, which houses my 

academic research program on carbon cycling. 

The Pew Center on Global Climate Change is a non-profit, non-partisan and 

independent organization dedicated to providing credible information, straight answers 

and innovative solutions in the effort to address global climate change. In our eight years 

of existence, we have published almost seventy reports by experts in climate science, 

economics, policy and solutions, all of which have been peer-reviewed and reviewed as 

well by the companies with which we work. 

Forty-one major companies sit on the Pew Center’s Business Environmental 

Leadership Council, spanning a range of sectors, including oil and gas (BP, Shell), 

transportation (Boeing, Toyota), utilities (PG&E, Duke Energy, Entergy), high 

technology (IBM, Intel, HP), diversified manufacturing (GE, United Technologies), and 

chemicals (DuPont, Rohm and Haas). Collectively, the 41 companies represent two 

trillion dollars in market capitalization and three million employees. The members of the 

Council work with the Pew Center to educate the public on the risks, challenges and 

solutions to climate change. 

If you take nothing else from my testimony, please take these three points: 

1. The scientific evidence of significant human influence on climate is strong and 

would in no way be weakened if there were no Mann hockey stick. 

2. The scientific debate over the Medieval Warm Period (MWP) has been gradually 

evolving for at least 20 years. The results of the Mann hockey stick simply reflect the 

gradual development of thought on the issue over time. 

3. The impact of the McIntyre and McKitrick critique on the original Mann paper, 

after being scrutinized by the National Academy of Science, the Wegman panel and a 
697

number of meticulous individual research groups, is essentially nil with regard to the 

conclusions of the Mann paper and the 2001 IPCC assessment. 

The science of climate change is an extraordinary example of a theory-driven, datarich scientific paradigm, the likes of which, arguably, has not occurred since the 

development of quantum mechanics in the first half of the twentieth century. The product 

of this strong scientific framework is a body of strong, multifaceted evidence that manmade greenhouse gases are causing contemporary global warming, and that this warming 

trend is inducing large-scale changes in global climate. The primary evidence is based on 

physical principles and observational and experimental analysis of contemporary climate 

dynamics, as opposed to analyses of past climates, which are the subject of this hearing. 

We can now say with confidence that the evidence of human influence on climate is 

strong, as described by Dr. Cicerone. 

Although paleoclimatology – the study of ancient climates – is an important part of 

the climate science frame work, reconstructions of temperature over the past millennium 

play a secondary, expendable role in the larger body of evidence, as stated in the recent 

NAS report titled, Surface Temperature Reconstructions for the Last 2,000 Years: 

“Surface temperature reconstructions are consistent with other evidence of global 

climate change and can be considered as additional supporting evidence” (National 

Research Council 2006, p. 23; hereafter referred to as the NAS report). Dispensing with 

such reconstructions entirely or proving them fundamentally flawed would have little, if 

any, impact on our understanding of contemporary climate change. This statement does 

not imply that millennial climate reconstructions are unimportant, but their main 

influence will be in the future, when their potential to reveal how climate varied across 

the earth’s surface from year-to-year in the past (i.e. an annual record of spatially explicit 

climate dynamics) is fully realized. At that point, such reconstructions will be used in a 

manner parallel to thermometer records today. This capability would contribute 

significantly to resolving the current genuine debate in climate science, which is not 

about whether humans are changing the climate—a point over which there is no scientific 

controversy—but is about how much human influences will change the climate in the 

future as a result of greenhouse gas accumulation and other forcings we apply to the 

climate system. In other words, the goal of spatially explicit paleoclimate reconstructions 

is to help climatologists determine how physical forcings, such as solar radiation, 

volcanic eruptions, land-use changes, and changes in atmospheric greenhouse gases, have 

affected the planet in the past, so that we can improve estimates of how they will do so in 

the future. 

The early MBH reconstructions (Mann et al. 1998; Mann et al. 1999; hereafter 

referred to as MBH98 or MBH99 or, collectively, MBH) were the first to offer spatially 

explicit climate reconstructions and therefore represented a breakthrough in climate 

change science that continues to develop and promises to further our understanding of 

climate physics in the future. The Wegman report’s conclusion that paleoclimatology 

“does not provide insight and understanding of the physical mechanisms of climate 

change” (p. 52), fails to appreciate that the purpose of Dr. Mann’s research is to improve 

our knowledge of physical mechanisms of climate change by examining how they 

operated in the past. 

Turning our attention to the methodological issues this hearing seeks to investigate, 

in my opinion, the Wegman report failed to accomplish its primary objective, which was 

“to reproduce the results of [McIntyre & McKitrick] in order to determine whether 

their criticisms are valid and have merit” (p. 7). Although the panel reproduced MM's 

work—verbatim—it only partially assessed the validity, and did not at all assess the 

merits, of the criticisms directed toward the MBH reconstructions. For instance, MM 

(McIntyre and McKitrick 2003; McIntyre and McKitrick 2005; heafter referred to 

collectively as MM) allege that the so-called MBH “hockey stick” result is biased by 

methodological errors that undermine the conclusion that the late 20th century was 
698

uniquely warm relative to the past 1000 years. This critique only has merit if, after 

correcting for the errors pointed out by MM, the resulting reconstruction yields results 

significantly different from the original result that can no longer support the claim of 

unusual late 20th century warmth. However, the Wegman Report takes no steps to make 

such a determination. 

Fortunately, a different group, one well qualified both statistically and 

climatologically to tackle this question of merit, had already performed the task several 

months before the Wegman Report was released. The study by Wahl & Ammann (In 

press; hereafter referred to as WA06), was peer-reviewed and accepted for publication in 

the journal, Climatic Change, early last spring, and has been publicly available in 

accepted form since last March (http://www.cgd.ucar.edu/ccr/ammann/millennium/refs/ 

WahlAmmann_ClimChange2006.html). This study, titled, Robustness of the Mann, 

Bradley, Hughes Reconstruction of Northern Hemisphere Surface Temperatures: 

Examination of Criticisms Based on the Nature and Processing of Proxy Climate 

Evidence, carefully reproduced the MBH98 reconstruction and then used their faithful 

reproduction to test MM’s suggested corrections. They tested each of the criticisms raised 

by MM in all of their published papers, including both the peer-reviewed and non-peerreviewed papers. Given that this report specifically examined MM’s criticisms, including 

the decentering issue that was the main focus of the Wegman report, it is unfortunate that 

the Wegman report dismissed it in a footnote (p. 48) as “not to the point.” 

WA06 have performed a meticulous and thorough evaluation of MBH98, and the 

answers that this committee seeks about the MBH reconstructions are to be found within 

this report. After examining each of MM’s three methodological criticisms, WA06 

accepted two of them as valid, and have used them to correct the MBH98 reconstruction. 

I will now show you what effect these corrections have on the MBH98 reconstruction, 

and then reconsider the uniqueness of the late 20th-century warming trend in the light of 

these corrections. 

The original MBH98 “hockey stick” is shown as a gray line (Fig. 1). The WA06 

reproduction of MBH98 is shown in red (Fig. 1). Except for a couple of minor 

simplifications, WA06 remained faithful to the original MBH method and retained all of 

the original MBH data, including the original instrumental temperature series from 1992. 

They wrote their own computer code to perform the calculations, using the R 

programming language, as recommended by the MM and the Wegman report, rather than 

Fig. 1. WA06 reproduction of MBH98 reconstruction. The gray line is the original MBH98 

reconstruction. The red line is the WA06 emulation. The black line is the original 1992 instrumental 

data used for calibration. The blus line is the latest instrumental data. The black bar with triangles 

represents the mean of the instrumental mean of the verification period. 
699

the original Fortran language used by Dr. Mann. As you can see, the two reconstructions 

are materially the same. This result demonstrates that MBH98 can be reproduced based 

on information available in the original MBH papers and supplemental information and 

data available on the Internet. 

Fig. 2. WA06 corrections of MBH98 for accepted MM corrections. The left frame shows original WA06 emulation 

of MBH in red and the corrected reconstruction accounting for decentering and excluding the Gaspe tree-ring 

series in blue. The right frame shows the same but with the bristle cone pine series removed (green line). 

Instrumental data are shown in black.

With this successful reproduction in hand, WA06 were able to test the effects of 

each of MM’s criticisms on the outcome of the MBH98 reconstruction. After carefully 

considering the validity of MM’s three criticisms of MBH’s reconstruction methodology, 

WA06 agreed that 1) decentering the proxy data prior to Principle Component analysis 

and 2) including the poorly replicated North American Gaspé tree-ring series from 1400-

1449 both affected the MBH results. After correcting for these effects, WA06 obtained 

the results shown in blue (Fig. 2, left frame). The result is a slightly warmer (0.1 °C) 

early 15th century, with no other time period affected. MM’s third methodological 

criticism surrounding the inclusion of the bristlecone/foxtail pine series was rejected for 

several reasons. The right frame in Fig. 2 illustrates that excluding these series has little 

effect on the MBH98 reconstruction, except to force it to begin in 1450 instead of 1400, 

because of lack of a data. Since the exclusion had little effect, and losing these data series 

would hinder reconstructions of earlier climate, WA06 rejected this criticism. 
700

Fig. 3. Wahl-Ammann corrections of the MBH99 reconstruction (Ammann & Wahl, submitted). The original 

MBH99 reconstruction is shown in blue and the corrected WA version is shown in red. Corrections were made 

for the decentering issue and the Gaspe tree-ring series. Instrumental data are in black. 

The additional 15th-century warmth revealed by making the valid MM corrections 

still does not approach the warmth of the late 20th century, so MM’s critique cannot yet 

be said to have merit. However, the corrected result creates the impression of an upward 

temperature trend backward in time before 1400, begging the question of what would 

happen to the Middle Ages in the 1000-year MBH99 reconstruction if it were also 

corrected? Answering that question is requisite for determining the merit of MM’s 

critique of MBH. The original 1000-year MBH99 reconstruction is shown in blue and the 

corrected version is shown in red (Fig. 3; Ammann & Wahl, submitted). Carrying the 

correction back to the full millennium reveals that the largest effects remain in the early 

15th century, and both earlier and later periods were less affected. Therefore, there is very 

little difference between the corrected MBH98 and MBH99 reconstructions and the 

originals, and the original observation that the late 20th century is uniquely warm in the 

context of the past 1000 years is not affected. Hence, the valid methodological caveats 

that MM pointed out do not undermine the main conclusions of the original MBH papers 

or the conclusion of the 2001 IPCC assessment. 

The scientific debate over the Medieval Warming Period (MWP) has been on the 

same trajectory for at least 20 years, with early indications that the MWP was not a 

globally coherent event becoming more solid over time. The MBH99 reconstruction 

represented an evolutionary step—not a revolutionary change—in this established 

trajectory. The 1990 IPCC figure that Mr. McIntyre, the Wall Street Journal editorial 

page, and Dr. Wegman have used in their own assessment of past climate is a cartoon, as 

stated by Dr. Wegman in his testimony last week. I have confirmed this with a number of 

individuals who were involved with the 1990 IPCC report or with versions of the 

schematic that pre-dated the 1990 IPCC report. The schematic is not a plot of data and is 

inappropriate as a comparison to MBH. The text of the 1990 IPCC report clearly states 

that the figure is a "schematic diagram" and that “it is still not clear whether all the 

fluctuations indicated were truly global” (p. 202). Furthermore, only three sources of 

information were cited and those sources conflicted on whether the Northern Hemisphere 

was warm or cold: “The late tenth to early thirteenth centuries... appear to have 

been exceptionally warm in parts of western Europe, Iceland and Greenland... 

China was, however, cold at this time, but South Japan was warm...” Clearly, this 

report certainly did not paint a picture of any consensus regarding a Medieval Warm 
701

Period as a hemisphere-wide phenomenon and characterizing it as such reveals a 

fundamental misunderstanding of climate science. 

The 1992 and 1995 IPCC reports continued this same trajectory of thought. Four 

years before MBH99, citing 6 papers—still a very limited number by twice as many as 

were cited in 1990—the 1995 report stated: 

There are, for this last millennium, two periods which have received special 

attention, the Medieval Warm Period and the Little Ice Age. These have been 

interpreted, at times, as period of global warmth and coolness, respectively. 

Recent studies have re-evaluated the interval commonly known as the Medieval 

Warm Period to assess the magnitude and geographical extent of any prolonged 

warm interval between the 9th and 14th centuries... The available evidence is 

limited (geographically) and is equivocal. ...a clearer picture may emerge as 

more and better calibrated proxy records are produced. However, at this point, 

it is not yet possible to say whether, at a hemispheric scale, temperatures 

declined from the 11-12th to the 16-17th century. Nor, therefore, is it possible 

to conclude that the global temperatures in the Medieval Warm Period were 

comparable to the warm decades of the late 20th century” (p. 174). 

Remember that this was written by a team of climatologists as a consensus statement. 

The consensus at this time, as in 1990, was that there was no strong evidence of a 

hemisphere-wide MWP. 

Continuing the same trajectory, the 2001 IPCC Third Assessment Report examined 

evidence from 10 cited sources for the MWP. The consensus at this point seemed to be 

turning to the conclusion that the there actually was a generally warm Northern 

Hemisphere during the Middle Ages, but that it was not a strong, coherent pattern of 

warming: 

It is likely that temperatures were relatively warm in the Northern Hemisphere 

as a whole during the earlier centuries of the millennium, but it is much less 

likely that a globally-synchronous, well defined interval of “Medieval warmth” 

existed, comparable to the near global warmth of the late 20th century... 

Marked warmth seems to have been confined to Europe and regions 

neighboring the North Atlantic. 

Since the MBH reconstructions were hemisphere-wide, and the MWP probably was not, 

it should not surprise us that the reconstructions lack a strong MWP (MBH99 does show 

slightly warmer temperatures in the 9th to 14th centuries than in the 15th to 19th centuries). 

All available evidence indicates that the situation during the Middle Ages was 

fundamentally different that what is happening with climate today, which is a welldocumented, globally coherent warming trend that is happening North, South, East, and 

West; at low latitudes and high latitudes; over land and over—and into—the sea. There 

are new data, published earlier this year, indicating that the atmosphere above Antarctica 

has warmed dramatically in recent decades (Turner et al. 2006). There is no large region 

on Earth where large-scale 20th century warming has not been detected, which simply 

cannot be said of the MWP. 

Wahl and Ammann (2006) have demonstrated that the results of MBH are robust 

“down in the weeds”: 

Our examination does suggest that a slight modification to the original Mann et 

al. reconstruction is justifiable for the first half of the 15th century (~ +0.05°), 

which leaves entirely unaltered the primary conclusion of Mann et al. (as well 

as many other reconstructions) that both the 20th century upward trend and high 

late-20th century hemispheric surface temperatures are anomalous over at least 

the last 600 years. 

The NAS has affirmed the MBH results are also robust in the bigger picture, as well: 
702

The basic conclusion of MBH99 was that the late 20th century warmth in the 

Northern Hemisphere was unprecedented during at least the last 1,000 years. 

This conclusion has subsequently been supported by an array of evidence that 

includes both additional large-scale surface temperature reconstructions and 

pronounced changes in a variety of local proxy indicators, such as melting on 

icecaps and the retreat of glaciers around the world, which in many cases 

appear to be unprecedented during at least the last 2,000 years. Not all 

individual proxy records indicate that the recent warmth is unprecedented, 

although a larger fraction of geographically diverse sites experienced 

exceptional warmth during the late 20th century than during any other extended 

period from A.D. 900 onward. (p. 3) 

Examination of the IPCC reports through time, as well as the primary scientific 

literature, reveals why the MBH results are so robust—MBH simply assimilated all the 

available evidence into a quantitative reconstruction—evidence that had already been 

evaluated qualitatively as lacking a coherent MWP. 

This committee is seeking to know the significance of the criticisms leveled at the 

MBH reconstruction for climate change assessments. The significance is that these 

criticisms have resulted in the most thoroughly vetted single climate study in the history 

of climate change research. Dr. Tom Karl summarized the impact most succinctly in his 

testimony to this committee last week when he said that he would stand by the IPCC’s 

original assessment: “If you ask me to give qualifications about the findings in the 2001 

report with the same caveat in terms of defining likelihood, I personally would not 

change anything.” Hence, the impact of the MM critique, after being scrutinized by the 

NAS, the Wegman panel, and a number of meticulous individual research groups, is 

essentially nil with regard to the conclusions of MBH and the 2001 IPCC assessment. 

Also relevant to this committee's questions about climate change assessments is the 

revelation that climate scientists do know their business, and that a lack of knowledge of 

geophysics is a genuine handicap to those who would seek to provide what they deem 

"independent review.” If the assessment of climate science presented in Mr. McIntyre's 

presentation to the NAS committee, the Wegman Report, and the WSJ is an example of 

what can be expected from those who have not conducted climate research, then the 

investigation launched by this committee has demonstrated clearly that “independent 

review” by non-climate scientists is an exceedingly ineffective way to make climate 

change assessments. 

References

Mann, M E, R S Bradley and M K Hughes (1998). "Global-scale temperature patterns 

and climate forcing over the past six centuries." Nature 392(6678): 779-787. 

Mann, M E, R S Bradley and M K Hughes (1999). "Northern hemisphere temperatures 

during the past millennium: Inferences, uncertainties, and limitations." Geophysical 

Research Letters 26(6): 759-762. 

McIntyre, S and R McKitrick (2003). "Corrections to the Mann et al. (1998) proxy data 

base and northern hemisphere average temperature series." Energy & Environment

14(6): 751-771. 

McIntyre, S and R McKitrick (2005). "Hockey sticks, principal components, and spurious 

significance." Geophysical Research Letters 32(3). 

National Research Council, C O S T R F T L, 000 Years. (2006). "Surface temperature 

reconstructions for the last 2,000 years." from http://www.nap.edu/catalog/ 

11676.html. 

Turner, J, T a Lachlan-Cope, S Colwell, et al. (2006). "Significant warming of the 

Antarctic winter troposphere." Science 311: 1914-1917. 
703

Wahl, E and C Ammann (In press). "Robustness of the Mann, Bradley, Hughes 

reconstruction of northern hemisphere surface temperatures: Examination of 

criticisms based on the nature and processing of proxy climate evidence." Climatic 

Change (accepted). 

 MR. WHITFIELD. Dr. Wegman, you are recognized for 5 minutes. 

DR. WEGMAN. Thank you. Good afternoon. I would like to begin 

by summarizing our previous testimony. Let me first begin by 

circumscribing the substance of our report. As you know, we were asked 

to provide an independent verification by statisticians of the critiques of 

the statistical methodology found in the papers of Dr. Michael Mann, 

Raymond Bradley, and Malcolm Hughes, published respectively in 

Nature and Geophysical Review Letters. These two papers have 

commonly been referred to MBH98 and 99. The critiques have been 

made by Stephen McIntyre and Ross McKitrick published in Energy and 

Environment in 2003, and in that same journal and also in Geophysics 

Research Letters in 2005. We refer to these as MM03, 05A, 05B, 

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. Our panel was composed of myself from 

George Mason University, Dr. David W. Scott from Rice University, and 

Yasmin Said, Dr. Said, from the Johns Hopkins. This ad hoc panel has 

worked pro bono, has received no compensation, and has no financial 

interest in the outcome. 

 The debate over Dr. Mann’s principal components methodology has 

been going on for nearly 3 years. When we got involved, there was no 

evidence that a single issue was resolved or even nearing resolution. Dr. 

Mann’s RealClimate.org website said that all of Mr. McIntyre and Dr. 

McKitrick claims had been discredited. UCAR had issued a news 

release saying that all their claims were unfounded, by the way, based on 

the Ammann paper just referred to. 

 The situation was ripe for a third party review of the types that we 

and Dr. North’s NRC panel have done. Because of the very high 

visibility of the original study, we see no harm and much advantage of 

having two independent analyses of the situation, from quite different 

perspectives. 

 While the two studies overlap on the important topic of Mann’s 

principal components methodology, Dr. North’s NRC panel considers 

topics that were outside the scope of our study, such as other temperature 

reconstructions. Where we have commonality, I believe our report and 

the NRC panel essentially agree. The error in the use of principal 

components methodology, the NRC panel reported under some 
704

conditions, the leading principal component can exhibit a spurious trend 

in the proxy-based reconstruction. 

 The NRC panel illustrated this with their own spurious hockey stick 

in Figure 9-2 on page 87 of the report. Our explanation of this 

phenomenon was similar, the authors make the seemingly innocuous and 

somewhat obscure calibration assumption. Because the instrumental 

temperature records are only available for a limited window, they use 

instrumental temperature data from 1902-1995 to calibrate the proxy data 

set. This would seem reasonable except for the fact that temperatures 

were rising during this period. So that centering on this period has the 

effect of making the mean value for any proxy series exhibiting the same 

increasing trend to be decentered low. 

 Because the proxy series exhibiting the rising trend are decentered, 

the calculated variance will be larger than their normal variance when 

calculated based on centered data, and hence they will tend to be selected 

preferentially as the first principal component. The centering of the 

proxy data is a critical factor in using principal components 

methodology. 

 The effect of decentering was illustrated by us in Figure 2, which is 

Figure 4.3 in our report. The top panel represents the North American 

Tree Ring PC1 as calculated based on the MBH98 methodology. The 

bottom panel illustrates the PC1 based on the same set of tree ring 

proxies with the centered PCA computation. We believe that our 

discussion, together with the discussion from the NRC report should take 

the centering issue off the table. The decentering methodology is simply 

incorrect mathematics as was illustrated in our Appendix A as well as 

with ample simulation evidence in both our report and that of the NRC 

report. 

 I am baffled by the claim that incorrect method doesn’t matter 

because the answer is correct anyway. The method wrong plus answer 

correct is just bad science. But with the centering issue off the table, the 

question then shifts from principal component analysis to which proxies 

exhibit the hockey stick shape and whether these proxies contain valid 

temperature signals. We agree with Dr. Mann that the hockey stick 

shape is in some proxies. 

 Figure 4 is an image that I showed in our previous testimony 

showing just six bristlecone pine proxies used in the construction of the 

North American PC1 series. The hockey stick shapes are clearly visible 

in the last two proxies. Given our discussion, it is clear how the 

decentering methodology will select these and give them prominence in 

PC1. So the question is are these valid temperature proxies. I quote 

from our report, “Graybill and Idso, 1993, specifically sought to show 

that bristlecone pines were CO2 fertilized. Bondi et al., 1999, suggest 
705

bristlecones are not reliable temperature proxy for the last 150 years as it 

shows an increasing trend in about 1850 that has been attributed to 

atmospheric CO2 fertilization.” We also know that IPCC 1996 report 

stated that the possible confounding effects of carbon dioxide 

fertilization need to be taken into account when calibrating tree ring data 

against climate variations. At the very least, the effect of these proxies 

on temperature reconstruction should be examined. 

 Figure 5 shows Dr. Mann’s own illustration, MBH, Internet, 2003, of 

the direct effect of North American tree ring data on reconstruction 

results in the 15th century. Indeed, it is our understanding as outsiders 

that all parties agree as to the significance of this tree ring network to 

final results, and that has made the use of the tree ring network a 

disputed issue as Mr. McIntyre has just pointed out. 

 Figure 6 is also a repeat graphic from my previous testimony. Please 

note that the Bristlecone/Foxtail PC1 proxy is used not only in MBH, but 

in virtually every subsequent reconstruction. We do not claim to be 

experts in dendrology either but it seems to us as outsiders that there are 

sufficient confounding factors that proxies based on bristlecones should 

be avoided. We should add that we were specifically asked to resolve 

the differences between MPH98/99 and the McIntyre and McKitrick 

papers. There is a bewildering array of subsequent work that we were 

not asked to consider, but which probably deserves much more intense 

scrutiny. We would include such refereed papers as Rutherford et al., 

2005, and Wahl and Ammann, 2006, which are purported to be written 

by independent teams, but which are co-authored by Dr. Mann himself in 

Rutherford et al. and by Dr. Mann’s student Dr. Ammann in Wahl and 

Ammann. 

 MR. WHITFIELD. Dr. Wegman, excuse me for interrupting. You are 

about 3 minutes over on the testimony, and we did hear your testimony 

last week and we have it in the record. And we genuinely appreciate 

your being back here today, and I am sure we will have some questions 

for you. 

 DR. WEGMAN. Thank you, sir. 

 MR. WHITFIELD. And you adequately covered last week also the 

social network and which we appreciate very much. 

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

PREPARED STATEMENT OF DR. EDWARD J. WEGMAN, DIRECTOR, CENTER FOR 

COMPUTATIONAL STATISTICS

Good morning. I would like to begin by summarizing our previous testimony. The 

debate over Dr. Mann’s principal components methodology has been going on for nearly 

three years. When we got involved, there was no evidence that a single issue was 

resolved or even nearing resolution. Dr. Mann’s RealClimate.org website said that all of 
706

the Mr. McIntyre and Dr. McKitrick claims had been “discredited”. UCAR1 had issued a 

news release saying that all their claims were “unfounded”. Mr. McIntyre replied on the 

ClimateAudit.org website. The climate science community seemed unable to either refute 

McIntyre’s claims or accept them. The situation was ripe for a third-party review of the 

types that we and Dr. North’s NRC panel have done. Because of the very high visibility 

of the original study, we see no harm and much advantage of having two independent 

analyses of the situation, from quite different perspectives. 

While the two studies overlap on the important topic of Mann’s principal 

components methodology, the Dr. North’s NRC panel considers topics that were outside 

the scope of our study, such as other temperature reconstructions. Where we have 

commonality, I believe our report and the NRC panel essentially agree. On the error in 

the use of principal components methodology, the NRC panel reported, “...under some 

conditions, the leading principal component can exhibit a spurious trend in the proxybased reconstruction. To see how this can happen, suppose that instead of proxy climate 

data, one simply used a random sample of autocorrelated time series that did not contain 

a coherent signal. If these simulated proxies are standardized as anomalies with respect to 

a calibration period and used to form principal components, the first component tends to 

exhibit a trend, even though the proxies themselves have no common trend. Essentially, 

the first component tends to capture those proxies that, by chance, show different values 

between the calibration period and the remainder of the data.” 

Figure 1 – Spurious Hockey Stick as reported in the NAS Panel 

report (Figure 9-2 in the NAS report). 

The NRC panel illustrated this with their own spurious hockey stick in Figure 9-2 on 

page 87. Our explanation of this phenomenon is similar. “... the authors make a 

seemingly innocuous and somewhat obscure calibration assumption. Because the 

instrumental temperature records are only available for a limited window, they use 

instrumental temperature data from 1902-1995 to calibrate the proxy data set. This would 

 

1

 UNIVERSITY CORPORATION FOR ATMOSPHERIC RESEARCH, FINANCIAL ARM OF 

THE NATIONAL CENTER FOR ATMOSPHERIC RESEARCH (NCAR). 
707

seem reasonable except for the fact that temperatures were rising during this period. So 

that centering on this period has the effect of making the mean value for any proxy series 

exhibiting the same increasing trend to be decentered low. Because the proxy series 

exhibiting the rising trend are decentered, the calculated variance will be larger than their 

normal variance when calculated based on centered data, and hence they will tend to be 

selected preferentially as the first principal component. ... The centering of the proxy 

series is a critical factor in using principal components methodology.” 

The North American Tree Network PC1 proxy was featured in MBH98. The top panel is the PC1 

using the MBH98 methodology. The bottom panel is the centered PCA reconstruction.

Figure 2

The effect of decentering was illustrated by us in Figure 2, which is Figure 4.3 in our 

report. The top panel represents the North American Tree Ring PC1 as calculated based 

on the MBH98 methodology. The bottom panel illustrates the PC1 based on the same set 

of tree ring proxies with the centered PCA computation. 
708

CFR Methods

Figure 3

To illustrate that this spurious decentering effect is not limited to just hockey sticks 

we created an additional illustration based on the IPCC 1990 temperature curve. With 69 

uncorrelated white noise proxies and one IPCC 1990 curve, it is clear that decentering 

can overwhelm the remaining proxies and preferentially select the one anomalous one. 

We believe that our discussion together with the discussion from the NRC report 

should take the “centering” issue off the table. The decentered methodology is simply 

incorrect mathematics as was illustrated in our Appendix A as well as with ample 

simulation evidence in both our report and that of the NRC report. I am baffled by the 

claim that the incorrect method doesn’t matter because the answer is correct anyway. 

Method Wrong + Answer Correct = Bad Science. But with the centering issue off the 

table, the question then shifts from principal component analysis to which proxies exhibit 

the hockey stick shape and whether these proxies contain valid temperature signals. We 

agree with Dr. Mann that the hockey stick shape is in some proxies. 
709

Sample Proxy Series

FIGURE 4

Figure 4 is an image that I showed in our previous testimony showing just six 

sample Bristlecone pine proxies used in the construction of the North American PC1 

series. The hockey stick shapes are clearly visible in the last two proxies. Given our 

discussion, it is clear how the decentering methodology will select these and give them 

prominence in PC1. Are these valid temperature proxies? I quote from our report, 

“Graybill and Idso (1993) specifically sought to show that Bristlecone Pines were CO2

fertilized. Bondi et al. (1999) suggest [Bristlecones] ‘are not a reliable temperature proxy 

for the last 150 years as it shows an increasing trend in about 1850 that has been 

attributed to atmospheric CO2 fertilization.’ ... We also note that IPCC 1996 report stated 

that ‘the possible confounding effects of carbon dioxide fertilization need to be taken into 

account when calibrating tree ring data against climate variations.’” At the very least, the 

effect of these proxies on temperature reconstruction should be examined. 
710

Figure 5

Figure 5 shows Dr. Mann’s own illustration (MBH, Internet, 2003) of the direct 

effect of North American tree ring data on reconstruction results in the 15th century. 

Indeed, it is our understanding as outsiders that all parties agree as to the significance of 

this tree ring network to final results. And that has made the use of the tree ring network a 

disputed issue. 
711

FIGURE 6

Bradley & Jones (1993)

Mann, Bradley, Hughes 

(1998,1999)

Jones et al. (1998)

Crowley & Lowery (2000)

Briffa (2000)

Esper (2002)

Mann & Jones (2003)

Bradley, Hughes, Diaz 

(2003)

Jones & Mann (2004)

Moberg et al. (2005)

Osborn & Briffa (2006)

D’Arrigo, Wilson, Jacoby 

(2006)

Figure 6 is also a repeat graphic from my previous testimony. Please note that the 

Bristlecone/Foxtail PC1 proxy is used not only in MBH, but also in virtually every 

subsequent reconstruction. We do not claim to be experts in dendrology, but it seems to 

us as outsiders that there are sufficient confounding factors that proxies based on 

Bristlecones should be avoided. We should add that we were specifically asked to resolve 

the differences between MBH98/99 and MM03/05a/05b. There is a bewildering array of 

subsequent work that we were not asked to consider, but which probably deserves much 

more intense scrutiny. We would include such refereed papers as Rutherford et al. (2005) 

and Wahl and Ammann (2006), which are purported to be written by independent teams, 

but which are co-authored by Dr. Mann himself in Rutherford et al. and by Dr. Mann’s 

student Dr. Ammann in Wahl and Ammann. 
712

Indeed, far from there being uniform agreement on the hockey stick shape, Bürger 

and Cubasch (2005) have reported that a discomforting array of different results can be 

obtained from MBH proxies under minor methodological differences. Figure 7 illustrates 

that while there may be reasonable consensus on warming since 1900, i.e. the calibration 

period, as the NRC report suggests, paleoclimate temperature reconstruction past 1600 is 

much more problematic. Indeed, on the matter of consensus, the NOAA website titled A 

Paleo Perspective ... on Global Warming has the following contradictory statements: 

“The latest peer-reviewed paleoclimatic studies appear to confirm that the global warmth 

of the 20th century may not necessarily be the warmest time in Earth's history, what is 

unique is that the warmth is global and cannot be explained by natural forcing 

mechanisms.” 

 From http://www.ncdc.noaa.gov/paleo/globalwarming/paleobefore.html 

Also from the same website: “In summary, it appears that the 20th century, and in 

particular the late 20th century, is likely the warmest the Earth has seen in at least 1200 

years.” 

From http://www.ncdc.noaa.gov/paleo/globalwarming/medieval.html 
713

Figure 8

We do agree with Dr. Mann on one key point: that MBH98/99 were not the only 

evidence of global warming. As we said in our report, “In a real sense the paleoclimate 

results of MBH98/99 are essentially irrelevant to the consensus on climate change. The 

instrumented temperature record since 1850 clearly indicates an increase in temperature.” 

We certainly agree that modern global warming is real. We have never disputed this 

point. We think it is time to put the ‘hockey stick’ controversy behind us and move on. 

I would like to make it clear that our role as statisticians in the hockey stick game is 

not as players in the hockey game, but as referees. What we have seen and continue to 

see is that, not withstanding the efforts by Dr. Nychka and others at NCAR, there is 

relatively little interaction between the statistical community and the climate 

science/meteorology communities although the latter frequently use statistical techniques. 

Statisticians in general have to pay their mortgages just like everyone else and in general 

cannot afford to do pro bono work such as we have been doing. We advocated in our 

report that if statistical methods are being used, then statisticians ought to be funded 

partners engaged in the research to insure as best we possibly can that the best quality 

science is being done. Drs. Nychka and Bloomfield, the statisticians involved with the 

NRC report, raise other issues on calibration, validation, and full quantification of 

uncertainty in these studies. Indeed there are a host of fundamental statistical questions 

that beg answers in understanding climate dynamics. 

Sampling 

How were the 70 trees in NOAMER 1400 selected? 

 4 Arkansas 

 4 Arizona 

 13 California 

 12 Colorado 

 3 Georgia 

 1 Louisiana 

 1 Montana 
714

 1 North Carolina 

 5 New Mexico 

 14 Nevada 

 3 Oregon 

 1 South Dakota 

 3 Utah 

 1 Virginia 

 4 Wyoming 

How representative are these trees of the population of trees that grew from 1400-

2000? In terms of geography, altitude, and type. If these trees seemed “interesting” to 

various individuals who took the core samples, do you believe those trees can/should be 

treated as a “random sample”? Are there biases in the selection of these trees? 

Presumably many trees could not be sampled because they had died or been harvested. 

What is the effect of this “censoring” on your data (and your analysis)? Similar questions 

exist about ice cores and how representative such data might be. What are the effects of 

gas diffusion in the ice core layers? 

Analysis 

What is the correlation between temperature and tree ring growth? What calibration 

studies have been performed? The rescaling steps taken seem to suggest that the 

correlation must be near 100%. Is that the case? The temperature proxy search is a 

regression problem. Why did you choose to use principal components (not appropriate 

for finding a nonstationary mean)? What weights do you use to combine different proxy 

types? Why? If the data are not a random sample, then what confidence can be given to 

any modeling and to any “error bars”? 

Forecasting and Modeling 

CO2 modeling shows a rapid increase in the near term. What do the models show in 

the longer term? Given the apparent high correlation between CO2 and temperature in the 

model outputs, how direct is the link in the model itself? What is the difference between a 

true forecast and a “model run”? Do you believe your model runs have any statistical 

validity? The output looks like a Taylor series with no higher order terms? 

Planning Experiments 

What data should be collected that would be most cost-effective in increasing our 

understanding of the climatic models and the underlying physics (and statistics)? Is all 

data valuable? How does one avoid the desire to collect data at sites that appear 

“interesting” beforehand? What are the parallels between modern experimental science 

and experimental medical research of the 1960's? How many surgeons were “certain” 

their treatments were superior or that drugs were safe and found out otherwise with 

carefully designed and controlled studies? Is the risk of global warming so acute that such 

studies are deemed unwise? 

Our report is not aimed at criticizing Dr. Mann or his colleagues, but in outlining a 

path for doing the science better. We note that the American Meteorological Society has 

a Committee on Probability and Statistics. I believe it is amazing for a committee whose 

focus is on statistics and probability that of the nine members only two are also members 

of the American Statistical Association, the premier statistical association in the United 

States, and one of those is a recent Ph.D. with an assistant professor appointment in a 

medical school. The American Meteorological Association recently held the 18th

Conference on Probability and Statistics in the Atmospheric Sciences (January, 2006). Of 

the 62 presenters at a conference with a focus on statistics and probability, only 8 

(12.9%) are members of the American Statistical Association. I believe these two 
715

communities should be more engaged and if nothing else our report should highlight to 

both communities a need for additional cross-disciplinary ties. 

 MR. WHITFIELD. So at this time I will start off the questions, and I 

would direct my first question to Dr. Mann and Dr. Christy and Dr. 

Cicerone. If you look at the 1990 U.N. report from the 

Intergovernmental Panel on Climate Change, it is quite pronounced the 

so-called Medieval Warming Period. And so the first question I would 

ask was there a Medieval Warming Period, Dr. Mann? 

 DR. MANN. Let me tackle that first. Actually the graphic you are 

referring to in the 1990 report was not an actual numerical estimate. It 

was a schematic based on very limited evidence in some parts of the 

globe, and that was actually emphasized in the report that they based that 

schematic on very limited information. Another interesting thing about 

that plot is that it actually ends in 1975. Now there has been roughly .5 

degrees C of additional warming in the climate in the Northern 

Hemisphere since 1975. And if you superimpose-- 

 MR. WHITFIELD. How much since then? 

 DR. MANN. Point 5 degrees C additional warming since 1975. 

 MR. WHITFIELD. Point 5 degrees. Okay. 

 DR. MANN. Yes. So if you superimpose that on the end of that 1990 

curve where it stops in 1975 actually the modern warmth is above the 

medieval peak. So it actually reinforces the later conclusions shown in 

the 1996 report and the 2001 report. 

 But we have learned a lot since then. For example, we know that the 

so-called Medieval Warm Period was actually fairly cold in the tropical 

Pacific. There is coral data that tell us that it was a La Nina like period. 

Now that means that there were large parts of the global surface that 

were cold at that time. As we learn more about the regional detail, we 

realize that it is incorrect to simply label that period as the Medieval 

Warm Period, and that is why most scientists now call it the Medieval 

Climate Anomaly. 

 MR. WHITFIELD. Okay. Dr. Christy, would you make comment 

about it? 

 DR. CHRISTY. Yes. Regarding the 1990 picture-- 

 MR. WHITFIELD. The Medieval Warming Period. 

 DR. CHRISTY. Some places were obviously warm, other places 

weren’t, and it is one that doesn’t look like it has a warm period at that 

time but there were other places that were warmer than today, I think. 

 MR. WHITFIELD. Okay. And Dr. Cicerone. 

 DR. CICERONE. I have nothing to add. I went back and looked at the 

cartoon after last week’s hearing and read all the surrounding pages and I 

have nothing to add. 

 MR. WHITFIELD. Okay. Now Mr.-- 
716

 CHAIRMAN BARTON. Mr. Whitfield, could I-- 

 MR. WHITFIELD. Yes, sir. Yes, sir. 

 CHAIRMAN BARTON. Why do we call that a cartoon and these others 

something different? I know the methodology is different but I would 

assume that the 1990 graphic was based on some mathematical evidence. 

It may not have been as complicated with as many variables as Dr. 

Mann’s later work, but I don’t think they just pulled that out of the air, 

did they? 

 DR. MANN. Let me comment. Actually it is a schematic. It is a 

cartoon. It was not a numerical estimate. 

 CHAIRMAN BARTON. They threw spaghetti up on the wall and 

wherever it stuck is what they put in the chart. 

 DR. MANN. Guided by some qualitative interpretations of historical 

climate records in a few locations in the Northern Hemisphere. It was 

not a quantitative estimate of climate. 

 CHAIRMAN BARTON. There is no averaging, there is no data to back 

it up? 

 DR. MANN. There is no numerical estimate that I am familiar with 

that went into that calculation that went into that graphic. There was no 

calculation. 

 DR. GULLEDGE. Mr. Barton, I have some--if you please. I actually 

spoke to some scientists who a couple have actually retired now who 

were involved in a 1975 NAS report on climate change that actually used 

a figure like this. And I spoke to Dr. Tom Webb who remembers the 

development of this figure and it actually originated from somebody’s 

lecture notes at one time from the early ‘70s. 

 CHAIRMAN BARTON. There is no data set? 

 DR. GULLEDGE. That is correct. There is no data set that is used in 

the production of this plot. There were studies where they said it looks 

like the north Atlantic was warm. There are studies that say China was 

cold. You know, we are proposing that there may have been a warm 

period in the Middle Ages, and to quote from the 1990 IPCC report in 

reference to this figure it says specifically, “It is still not clear whether all 

the fluctuations indicated in the diagram were truly global.” And that is 

directly from the report referring to this diagram. 

 CHAIRMAN BARTON. Thank you, Mr. Whitfield. 

 MR. WHITFIELD. Yes, sir. Just referring to Mr. Inslee’s chart about 

CO2 concentration levels and temperatures going back 400,000 years, it 

is constantly up and down, constantly up and down. Now is that 

something that we normally expect that CO2 emissions constantly go up 

and down for 400,000 years? Would someone reply to that? 

 DR. CICERONE. May I respond? 

 MR. WHITFIELD. Yes, sir. 
717

 DR. CICERONE. The CO2 data comes from extracting gas dissolved 

in ice as was explained last week. 

 MR. WHITFIELD. And where is the Vostock ice core, where is that? 

 DR. CICERONE. It is at a particular region in Antarctica where the ice 

is so thick that you can actually go back that many years and do 

reasonable dating. It doesn’t mean that every year is exactly one year but 

it is pretty good resolution so they crush the ice or melt it. The problem 

with melting is some of the gas can dissolve in liquid so probably the 

safest technique is to crush the ice and extract the air. The CO2 record is 

absolutely quantitative. It shows that through the last four ice ages if you 

go back to 650 or 700,000 years when the Earth was cold the CO2

amounts were low. 

 When the Earth was warm in between the ice ages the CO2 got 

higher, and the range was about 180 to 280 parts per million. Those are 

the natural cycles of the Earth. People have tried very hard to say did the 

CO2 increase cause the warming or the cooling or did the warming and 

cooling cause the CO2. The only evidence that seems clear is that there 

were times when the warming preceded the CO2 and the cooling 

preceded the loss in CO2 but they are nearly linked in time. So people 

are scratching their heads, what are the feedbacks that cause this? How 

did these ice ages start? What triggered them? How do we get out of 

them? 

 Methane amounts also track perfectly. When Earth was warm 

methane was two-thirds of a part per million. When it was cold it was 

one third of a part per million. Now we are at five-thirds of a part per 

million so we are out of that range. That is about all I can say. So the 

biological process that release CO2 and methane were probably 

responsible. 

 MR. WHITFIELD. So it is continually going up and down. Would 

you anticipate that it would go down at some point in the future or do 

you feel like it is going to continue to go up? 

 DR. CICERONE. Well, the CO2 that is in the air now is 385 parts per 

million, which is 200 parts per million larger than the 180 minimum at 

cold times and 100 larger than the CO2 maximum at hot times. It is 

going to take 200 years for that CO2--if we quit putting CO2 in the 

atmosphere today and all the plants decomposed, it would take a couple 

hundred years for the CO2 to fall back to that region. It is not going to 

happen. 

 MR. WHITFIELD. And what percent of all the CO2 being emitted 

today would you say is man-made and what percent is natural? 

 DR. CICERONE. Well, the decay in biota and respiration and 

geological processes put 100 gigatons of CO2 carbon in the air each year. 

Combustion of fossil fuels puts in 6 or 7. So the natural inputs are larger 
718

by far but the equilibrium of the system as established as Professor North 

mentioned last week is the processes that suck it up are about 100, so the 

imbalance is the 6 or 7 and about half of that shows up in the air and the 

other half seems to go in the oceans every year. 

 MR. WHITFIELD. But the natural emissions are overwhelmingly 

larger than man made but the man-made part is what messes up the 

equilibrium. 

 DR. CICERONE. Well, numerically they are overwhelmingly larger 

but the atmosphere seems to think otherwise because the atmosphere is 

responding to the increase. 

 MR. WHITFIELD. Right. Now, Dr. Christy, you have done some 

work on satellites, observations of the Earth’s surface, and I read a book 

a number of years ago entitled “A Moment on the Earth” by a guy named 

Greg Easterbrook, and there was some part of that where he talked a lot 

about the satellites were not--the models being used to project global 

warming and the satellite observations were not in sync. I am sure I am 

not expressing it in the proper scientific way but hopefully you may 

know what I am referring to. 

 And I know that some of the work that you did, you received a lot of 

criticism or not criticism, but people were taking shots at you also 

because you had an error in your work relating to satellites and you were 

off like .035 percent of one degree or something. But would you 

elaborate a little bit about the satellite observations today and how that 

matches up with the global warming that we hear about from a scientific 

standpoint? 

 DR. CHRISTY. Yeah, it is curious. I have a couple papers coming 

out this year, in fact, in which we show that the evidence indicates the 

atmosphere is not warming as fast as it is typically thought from 

enhanced greenhouse gases particularly in the tropics, so that is the short 

answer. 

 MR. WHITFIELD. Okay. And these papers will be coming out when? 

 DR. CHRISTY. I turned the page proofs back for one yesterday so it 

is probably a couple months. The other one will probably be about 3 

months. 

 MR. WHITFIELD. Okay. My time has expired. Mr. Stupak. 

 MR. STUPAK. Mr. Chairman, as a courtesy to Mr. Waxman I am 

going to yield my time to Mr. Waxman, and I will assume his time when 

his time comes. 

 MR. WAXMAN. Thank you very much, Mr. Stupak. Mr. Chairman, 

it is interesting that you are citing Gregg Easterbrook as someone who in 

the past had been a skeptic, and he recently wrote where he said “as an 

environmental commentator, I have a long record of opposing alarmism. 
719

But based on the data I am now switching sides regarding global 

warming, from skeptic to convert.” 

 MR. WHITFIELD. Well, I mentioned his name so you could bring that 

up, Mr. Waxman. 

 MR. WAXMAN. All right. Dr. Mann, your work was extensively 

criticized by Dr. Wegman last week. He criticized certain statistical 

aspects of your work and provided testimony on global warming more 

generally. However, Dr. Wegman isn’t a climatologist, and I would like 

to give you the opportunity to respond to some of his statements from 

last week’s hearing. He stated, “Carbon dioxide is heavier than air.” And 

“if the carbon dioxide is close to the surface of the Earth it is not 

reflecting a lot of infrared back.” Would you care to respond to that 

statement? 

 DR. MANN. Yes. It is a somewhat problematic statement on a 

couple levels. First of all, of course the greenhouse effect is not based on 

the reflection of radiation, it is based on the absorption of outgoing 

radiation. Rather than escaping to space it is radiated back towards the 

surface and the surface has to warm up in response to that. So reflections 

isn’t involved at all. It is the process of absorption, selective absorption. 

 The other problem with that statement is that the well mixed 

atmospheric constituents, oxygen, nitrogen, carbon dioxide, their 

distribution, their vertical distribution in the atmosphere doesn’t have to 

do with their weight or their relative masses. It just has to do with the 

basic force balances that act in the atmosphere. There is gravity and then 

there are gradients due to the pressure of the atmosphere and these two 

things have to balance out. And it turns out that all of the well-mixed 

gases decay with the same vertical profile falling to about one-third of 

their surface concentration at roughly eight kilometers up in the 

atmosphere. And that is true for CO2 as well as oxygen. 

 MR. WAXMAN. I thought that at the time, and I am glad to hear your 

response because I knew there was something wrong with that statement. 

When Dr. Wegman was asked about your research since 1999 he stated 

that you had circled your wagons “and tried to defend this incorrect 

methodology.” I would like to know if this is true. Did you continue to 

use the same methodology or have you worked to improve your 

approach since 1998? 

 DR. MANN. Thanks for the question. It is another troubling 

statement that you quote there because of course my collaborators and I 

have far from circling our wagons, we have been spearheading efforts to 

develop more sophisticated statistical methodologies for reconstructing 

climate and rigorously testing those methods using climate model 

simulation. We published a number of papers that show that the methods 

we used performed very well in the context of climate model simulations 
720

where we know the answer. We don’t have to guess because we have 

the simulation. There were some other statements-- 

 MR. WAXMAN. Well, let me asks you about some of the other 

statements because he attempted to impeach your statistical background 

by complaining that you used non-standard statistical phrases in your 

research like “statistical skill.” Can you help us understand? Is this an 

unusual phrase as Dr. Wegman suggests? 

 DR. MANN. That was another very odd statement on his part, and I 

found his lack of familiarity with that term somewhat astonishing. The 

American Meteorological Society considers it such an important term in 

the context of statistical weather forecasting verification that they 

specifically define that term on their website and in their official 

literature. And in fact it is defined by the American Meteorological 

Society in the following manner: “A statistical evaluation of the accuracy 

of forecasts or the effectiveness of detection techniques.” Several simple 

formulations are commonly used in meteorology. The skill score is 

useful for evaluating predictions of temperatures, pressures, et cetera, et 

cetera, so I was very surprised by that statement. 

 MR. WAXMAN. Dr. Wegman testified he thought global warming “is 

probably less urgent than some would have it be.” He also discounted 

the impact of increasing the planet’s temperature by 2 degrees testifying 

that he would “challenge anybody to go out and tell the difference 

between 72 and 74 degrees Fahrenheit.” Dr. Mann, the impacts of 

climate changes are a well studied area. Does Dr. Wegman have any 

basis for being so cavalier about global warming? 

 DR. MANN. Well, just to provide some context. The difference 

between the height of the last glacial period when there was more than a 

kilometer of ice sitting above New York City global temperatures were 

probably only about 4 degrees colder than they are today so that gives 

you some idea of the dramatic nature of climate associated with fairly 

moderate changes in global mean temperature. Those changes in global 

mean temperature are often associated with much larger changes in 

certain very important regions like the Arctic where the warming over 

the last century is much greater than the global mean, and we have seen 

melting of perma frost and other impacts of that. 

 MR. WAXMAN. He also said that global warming “must be 

understood in the context which is that we have relatively speaking a 

Little Ice Age, which everybody seems to acknowledge, and so it is not 

so surprising that it is warming if we are coming out of a Little Ice Age.” 

Does Dr. Wegman’s statement accurately reflect the scientific 

consensus? 

 DR. MANN. No. In fact, the implications are just about the opposite 

of what he had stated. In fact, we know with the climate models that we 
721

have today that embody the basic physics of the atmosphere and the 

ocean and the interactions between them, actually we can describe, we 

can predict and explain the factors that underlied the Little Ice Age and 

the fact that certain regions like Europe cooled somewhat more 

dramatically than the rest of the globe some time between the 17th and 

19th Century. 

 It turns out that that is the response of the climate to the changes in 

natural factors like explosive volcanic eruptions and small changes in 

solar radiants that were relevant to the past. Those same models that so 

successfully describe the Little Ice Age tell us that there is no way to 

explain the warming of the last century without the influence of human 

beings on concentration of greenhouse gases in the atmosphere. 

 MR. WAXMAN. So I shouldn’t be nostalgic for that Little Ice Age. 

 DR. MANN. Perhaps not. 

 MR. WAXMAN. Did Dr. Wegman ever contact you to talk about your 

work or ask for any further explanation from you about it? 

 DR. MANN. No. 

 MR. WAXMAN. Some have criticized you for lack of willingness to 

disclose your data and computer code. Could you briefly tell us how you 

have handled the availability of your research? 

 DR. MANN. Well, first of all I would like to draw a distinction 

between data and code. The statement was made earlier here that I didn’t 

make my data available until 2004, and that is simply incorrect. Our 

entire data set was available on the worldwide web several years before 

that. Now a code, well, that is a different sort of thing. It is a matter of 

intellectual property because it takes a lot of work to implement the 

algorithm that one might be using to perform a certain sort of operation, 

but as long as the algorithm is available then other people can 

independently reproduce your work without having the actual physical 

code. 

 And, in fact, that is what Dr. Wahl and Dr. Ammann have shown. 

They have independently implemented our algorithm in a different 

programming language that is available to anybody who wants to go to 

their website to access it. As a matter of fact, over the past few years we 

have been making all of our codes available for all of the calculations 

that we do, and that is actually a standard that many others in our 

community, the climate research community, haven’t really followed, so 

we are sort of leading the way there. 

 MR. WAXMAN. Thank you. I want to ask Dr. Christy about this 

because you stated that you provided your computer code to other 

researchers when it has been requested, and you specifically mentioned 

providing your code to Remote Sensing Systems or RSS. Is that 

accurate? 
722

 DR. CHRISTY. We provide the part of the code that was in question. 

 MR. WAXMAN. Well, I contacted RSS about your testimony and Mr. 

Frank Wentz sent me a letter last night, and he wrote to say, “Dr. Christy 

has never been willing to share his computer code in a substantial way,” 

and he provides the text of a 2002 e-mail exchange between RSS and 

yourself. And according to this letter when asked for your code, you 

replied “I don’t see how sharing code would be helpful because there are 

at least seven programs that are executed (several thousands lines of 

code) and we would be forced to spend a considerable amount of time 

trying to explain coding issues of the spaghetti we wrote.” In light of 

this letter, Dr. Christy, I would be interested if you care to clarify your 

testimony because Mr. Wentz wrote further, “I think the complexity 

issue was a red herring. My interpretation of Dr. Christy’s response is he 

simply didn’t want us looking over his shoulder, possibly discovering 

errors in his work. So we had to take a more tedious trial-and-error 

approach to uncovering the errors in his methods.” 

 And then he went on to explain “RSS manages data software from a 

large array of climate satellites.” What do you say about that? That 

sounds inconsistent with what you have told us. 

 DR. CHRISTY. We shared with them the parts of the code that they 

were most concerned about. What is called the drift effect was one of 

them. Because ours were machine dependent and so on like that but we 

did share not only that but we also shared the intermediate data to say, 

okay, if you implement this code this is the intermediate data you should 

get, and that is what they published. 

 MR. WAXMAN. I must say I am a politician as all the people here at 

our dais are and all of us engage in politics as we know it, but here is a 

session with scientists, and you went ahead and attacked Dr. Mann, who 

is an accomplished and respected climate researcher. I think you and Dr. 

Wegman attempted to smear his good name. Now I just got a letter from 

another person-- 

 MR. WHITFIELD. The gentleman’s time has expired. 

 MR. WAXMAN. --in your field who says that you haven’t been 

forthcoming, so I just want to point out to all of you, we don’t do the 

back biting as frequently as it seems to me that some of you scientists 

seem to do to each other. 

 MR. WHITFIELD. But Dr. Christy did say that he shared part of the 

code that he asked for. 

 DR. CHRISTY. Yes. They got what they wanted. 

 MR. WAXMAN. May I ask unanimous consent to put the letter from 

Dr. Wentz in the record? 

 MR. WHITFIELD. Without objection. 

 MR. STEARNS. I would object, Mr. Chairman. 
723

 MR. WHITFIELD. Okay. Objection. 

 MR. STEARNS. I object just because I think staff should have an 

opportunity to see the letter first. 

 MR. WHITFIELD. Okay. 

 MR. WAXMAN. I certainly would share it with staff. Assuming staff 

sees no objection from the letter that I received last night, I would like 

to-- 

 MR. STEARNS. Mr. Chairman, you remember last time that I asked a 

letter to be submitted to the record and they objected until they saw it-- 

 MR. STUPAK. But we put the letter in. 

 MR. STEARNS. I know, but I produced a letter for the gentleman. 

 MR. WHITFIELD. If I could have order a minute. We will look at the 

letter. We will have staff look at the letter. In the meantime I recognize 

the Chairman of the full committee for 10 minutes. 

 [The information follows:] 
724

 CHAIRMAN BARTON. We are about truth, and my guess is Mr. 

Waxman’s letter helps the truth so we will almost certainly put that in the 

record. Dr. Mann, I read your prepared testimony and I have listened to 

your synopsis, and you said something that I didn’t see in the prepared 

testimony. Maybe it was there. You talked about scientists trying to 

make certain they don’t make categorical statements. I don’t know 
725

exactly but it sounded, to coin a phrase, plausible what you said. Now in 

our opening statements my friends on the other side, and they really are 

my friends. We get along a lot better off camera than we do on camera. 

 Their opening statements seem pretty categorical to me. Their minds 

seem to me to be pretty made up, that this is a major problem and it is 

time to stop foot dragging and let’s get on and fix it. I don’t quite have 

that religion yet. I haven’t been born again quite yet. And that is what 

this is all about. If in fact all these things that my friends, Mr. Inslee and 

Ms. Schakowsky and Mr. Waxman, believe so fervently are literally 

factually true without question then we need to move to problem 

solution. 

 But I look at these data sets, I look at these data points, I look at 

these theories and things, and I see a sign curve phenomenon where the 

Earth gets warmer, the Earth gets cooler, the Earth gets warmer the Earth 

gets cooler. It certainly appears that it is getting warmer faster in this 

century. It is certainly plausible that it has got to be partially caused by 

man-made emissions. But I think it is a little early to categorically make 

some of the statements that my friends on the Minority side are making. 

 And the reason that we asked you to try to provide your data sets and 

your codes and stuff is because yours was the very first one and it is 

referred to. Now there may be a hundred since then and maybe we ought 

to look at all hundred of them, but yours is the one even in the National--

the science review--Research Council review. It talks about that in the 

executive summary. So do you feel--from everything I can find out about 

you is that you are a very fine person and an excellent scientist and 

totally dedicated to your work, but do you think it is fair to ask you to try 

to let other people verify that first study since it seemed to have such an 

impact on the community? 

 DR. MANN. Well, no, I don’t think it is unfair at all to expect the 

scientific community to validate previous results and to refine them, and 

that process has been occurring over the past 10 years since our work 

was begun. I think the National Academy members at their press 

conference said something to the effect that they felt that the scientific 

process had worked quite well in this area in that methods have been 

refined, new proxy data have become available. Multiple estimates are 

now available where there were three at the time of the IPCC 2001 

report. There are now more than a dozen different estimates. There are 

also independent model simulations-- 

 CHAIRMAN BARTON. You don’t think it is unfair to have a little 

scrutiny to the--if it is a conclusion, anybody has a right to a conclusion 

and an opinion but when it gets into the mainstream that it is just a given 

that is what I take a little exception to even today. Now I want to ask a 

follow-up question. Dr. Wegman said when he tried to get enough 
726

information to try to verify the model, verify the algorithm, he says he 

had some trouble getting that. Now you talked about codes and 

algorithms. What is the difference, and I am not a statistician and I am 

not a climatologist or a paleoclimatologist. What is the difference 

between a code and an algorithm? 

 DR. MANN. Okay. Let me try to use an analogy. 

 CHAIRMAN BARTON. Use a simple one. 

 DR. MANN. I will do my best. 

 CHAIRMAN BARTON. The simpler, the better. 

 DR. MANN. Well, let’s think of an algorithm is--suppose you were 

trying to build a house. And you wanted to build a house and the data 

would be the materials you need to build the house, the nails, the wood, 

et cetera. The algorithm would be the architectural plan. Now what 

would the code be? Well, imagine that instead of builders you had a 

computer to make your house for you. Well, the code would be 

implementing the architectural plan by telling the computer to pick up 

the hammer, pick up the nail, hammer it in. And so the code is simply 

implementing the algorithm but the real scientific process is embodied 

within the algorithm, and the algorithm is what has been independently 

reproduced. 

 CHAIRMAN BARTON. What is proprietary about a formula or 

mathematical model that tries to compute something as gargantuan as 

world climate over 2,000 years? I don’t see anybody making any money 

on that. I mean if you put it out there and said this is what is happening 

and try to predict the future, why should that not all be made available in 

some public way that independent reviewers can try to replicate it? 

 DR. MANN. Well, let me preface this by putting out that we now as a 

matter of course do make available our codes that we have written to 

implement these different methods and so the Rutherford et al. paper that 

was shown earlier reproduces essentially the original reconstruction, that 

entire code can be downloaded from our website. 

 CHAIRMAN BARTON. If we asked, which we are going to, asked Dr. 

Cicerone--we are going to ask him to review some of these 

recommendations that Mr. McIntyre and Dr. Wegman and others have 

made, but one of them is going to be that because the stakes are so big 

and the consequences are so big that these models and data sets and 

things be made available in some way that they can be verified. Do you 

have a problem with that? 

 DR. MANN. No. I think this is a bigger question than one that 

should be asked of me. There are bigger questions about intellectual 

property rights, and people--the scientific community and the policy 

makers need to work that out, what is the balance between making sure 

that scientists are allowed to write a code, spend a whole lot of time 
727

doing it and be able to implement it and use it without immediately 

having to turn it over to somebody else who suddenly then gets all of 

their intellectual contributions over a several year period. So I think 

there is a balance there. I don’t disagree with the premise of what you 

are saying. 

 And I think there is the issue that Dr. Christy brought up earlier, if 

you take, for example, our 1998 work, well, that was a program, I think 

you alluded to this last week, it was written in Fortran and a fairly-- 

 CHAIRMAN BARTON. I was stunned to know that that program was 

still in existence. 

 DR. MANN. It is still more widespread than you might think actually. 

 CHAIRMAN BARTON. What generation is it now because I was up to 

Fortran 4. 

 DR. MANN. It was 90 and then--and we were back in F77, Fortran 

77 is what we wrote this program in. So there is the issue of platform 

dependence. And now we are getting away from that. For example, we 

write all of our codes now in MAT Lab, which is a portable 

programming language and anybody who has MAT Lab can implement 

it. And that is the direction things are moving but to apply the standard 

to work that was done 10 years ago may be unfair because the standards 

have changed. 

 CHAIRMAN BARTON. Dr. Christy, I read your testimony, and I want 

to compliment you on its preparation and your forthrightness. On page 

11 you talk about, in the second paragraph, that the issue of climate 

model evaluation has been performed mostly by the modelers 

themselves. It is my view, this is you speaking here, and 

recommendation that policy makers would learn much from independent 

hard-nosed assessments of these model simulations by those who are not 

directly vested in the outcome. Some of this is going on but the level of 

support is minimal. Do you still stand by that? 

 DR. CHRISTY. Yes, I do. I think probably any scientific endeavor 

could stand with independent eyes looking over it. 

 CHAIRMAN BARTON. Dr. Cicerone, do you agree with that 

statement? 

 DR. CICERONE. The more the merrier. I have done a lot of 

mathematical modeling maybe 15 or 20 years ago, and I remember 

efforts to try to compare models where unfortunately what happened was 

everybody said, well, let’s put the same assumptions in the models and 

see how they do. And I think it worked against the science because it 

created less independence. So to do this kind of exercise I think we have 

to take everything into account but generally it is a good idea in my 

opinion. 
728

 CHAIRMAN BARTON. I know I am over time. I want to read one 

more paragraph in Dr. Christy’s testimony because it kind of 

encapsulates the policy dilemma that we are faced with and ask the panel 

to comment on it. And I am quoting, “To understand the scale of what 

we are dealing with this serves as a rough example. We know that we on 

Earth benefit from 10 terawatts of energy production today. To achieve 

a reduction of the CO2 representing 10 percent, 1 terawatt, of that 

production we need 1,000 nuclear power plants at 1,000 megawatts each. 

Massive implementation of wind and solar does not achieve this result 

and would not provide the baseload power needed by the economies 

today in any case. Thus, to have a 10 percent impact on emissions from 

energy, that is growing at the same time, will require a tremendous and 

difficult and expensive restructuring of energy supplies.” 

 So even if we accept the problem and move to solution to get a 10 

percent reduction in CO2 takes 1,000 megawatt nuclear power plants and 

it probably doesn’t have any impact for 50 to 100 years. Do you all want 

to comment on that, anybody, other than Dr. Christy, which you can. It 

is your statement. 

 DR. CHRISTY. I would just say the energy committee is where a lot 

of this is going to be done and that is just to give you an idea of the scale 

of what you are going to be tackling, I think, in the next few years. 

 CHAIRMAN BARTON. That is why I am still a skeptic. I don’t want 

to jump in there especially if this is a naturally reoccurring phenomenon 

that is exacerbated by human emissions but it is going to happen 

regardless of what we do. Dr. Cicerone. 

 DR. CICERONE. The numbers that you just summarized from Dr. 

Christy are really intimidating. I agree with you. I would like to see us 

all get together with the elements of a win-win strategy. There are some 

actions we can take as first steps, I think, which are truly win-win, and 

they have to do with energy efficiency. Just look at it from the United 

States point of view. If we could decrease our dependence on foreign 

energy we would improve national security, we would decrease the trade 

deficit, we would, I think, stabilize geo politics a little, we would 

increase national competitiveness by making our manufactured products 

cheaper. 

 When energy prices are high you know better than I our 

manufactured products have to bear that increase. We could develop 

new products which would create new world markets and we could be 

leaders. We would decrease the energy costs for households and 

incidentally slow down the emissions of CO2. So I think we need a winwin strategy and we can take a bite out of that 1,000 gigawatts with 

energy efficiency. 
729

 CHAIRMAN BARTON. My time has more than expired so I apologize. 

Thank you all for being here. 

 MR. WHITFIELD. I recognize Mr. Stupak of Michigan. 

 MR. STUPAK. Thank you. We were talking about that Fortran 4 

program, and I was just wondering was that during the Medieval 

Warming Period we have been talking about? If I may, Mr. Chairman, 

when I gave my opening statement I had a couple of exhibits. I should 

have asked at that time that they be made part of the record with my 

opening statement. It is the Interfaith Stewardship Alliance that I 

mentioned and how they were funded by ExxonMobil, so if I may 

without objection put that as part of my opening statement. 

 MR. WHITFIELD. And we have a copy of it. 

 MR. STUPAK. Yes. 

 MR. WHITFIELD. Thank you. 

 MR. STUPAK. Dr. Cicerone, just speaking of the Medieval Warming 

Period as it was described in the Wall Street Journal. We talked a little 

bit about it earlier. In fact, are we even sure that even happened in the 

Northern Hemisphere, that Medieval Warming Period that the Wall 

Street Journal talked about, that was that chart there, the 1990 chart that 

we had some discussion about earlier. 

 DR. CICERONE. I am sorry. Were you addressing that to me, sir? 

 MR. STUPAK. Yes, sir. 

 DR. CICERONE. Okay. There were certainly records of warm places 

in that period of time. 

 MR. STUPAK. Warm places and cold places. 

 DR. CICERONE. The question continues to be how extensive was it, 

how long did it last, and how solid is the evidence. But, yes, there is 

evidence of a Medieval Warm Period, but no one can sit here and tell 

you how geographically extensive it was with strong evidence and how 

long it lasted. But, yes, there was a Medieval Warm Period. 

 MR. STUPAK. Dr. Crowley says that even though it was difficult to 

unequivocally assert that the current warming period is significantly 

greater than the peak warmth of the Medieval Warm Period there is even 

less justification for saying that the medieval period was warmer than it 

is today, is that correct? 

 DR. CICERONE. The committee that Professor North reported on, 

Professor North from Texas A&M, last week representing the National 

Research Council, I am pretty sure what they concluded was there was 

no evidence that that period was warmer than say the year--the decade of 

the 1990s through 2006. 

 MR. STUPAK. But were considerably warmer? 

 DR. CICERONE. They could not say with strong evidence that each 

year in the 1990s was warmer than then but there was no evidence that 
730

the Medieval Warm Period over an extensive geographical region was as 

warm as the Northern Hemisphere is now. 

 MR. STUPAK. Is it fair to say then that neither the pro-hockey stick 

researchers or the anti-hockey stick researchers can talk with scientific 

certainty about this medieval period, would that be correct? 

 DR. CICERONE. In certain locations they can where there were 

records kept, but the question again is how does one location compare 

with all the others. For example, some proxy indicators from China 

inferred what the temperatures were from agricultural crops and stream 

flows and so forth, which are pretty extensive, but it is hard to compare 

the timing of those with other strong proxies from elsewhere. 

 MR. STUPAK. Let me ask you this question then. This is the second 

hearing we have had on this hockey stick theory, but you were on the 

National Academy of Science panel that looked at these studies. Are you 

telling us basically forget the hockey stick and the Medieval Warm 

Period, it is a diversion? Is it your position that global warming is 

occurring now in the 20th and 21st Century? Human beings are at least 

partially responsible. Our climate will continue to change during the 

next century and we ought to pay attention to it today. Is that fair to say? 

 DR. CICERONE. Well, I wouldn’t say forget the hockey stick and 

efforts to reconstruct because what we can learn, and if we work harder 

we might be able to learn some more about the context, it is still 

important, but, yes, all the other evidence shows us that the climate is 

changing and that the human hand is there causing at least part of the 

warming and that everything we know from physics and chemistry and 

mathematics is that it is going to continue as long as we continue to load 

up the atmosphere with greenhouse gases. 

 MR. STUPAK. Do you think it is useful then, Doctor, for us policy 

makers to hold hearings on just one 8-year old study, Dr. Mann’s study, 

that your committee found was not even the principal evidence for the 

conclusion about current warming period? 

 DR. CICERONE. I hope that it has been useful. I have never seen this 

kind of interest before. I think a couple--I have forgotten who said it 

earlier on about that this could be--perhaps it was Mr. Bass, who said this 

could be the beginning of even more serious interest. So I guess I will 

wait and see what happens. 

 MR. STUPAK. If there is so much interest in this one and if in the 

Vice President’s book he talks about 928 more peer reviewed articles, so 

that means if we have two hearings for every one of these we would have 

about 1,800 hearings just on global warming. I guess that would be a 

sufficient amount to get everyone’s attention. Let me ask this question if 

I can. There has been a lot of discussion about social networking, and I 

think it is a practice that is not utilized, should not be utilized. Peer 
731

review and whether it is an accepted practice, isn’t it, in 

paleoclimatology field, social networking, Dr. Cicerone? 

 DR. CICERONE. No. No, that was I guess kind of an original piece 

work. It is not common. 

 MR. STUPAK. Have you looked at or have you reviewed Dr. 

Wegman’s social network analysis of the paleoclimatology field? 

 DR. CICERONE. Last week at the time of the hearing I got a copy and 

I read it. 

 MR. STUPAK. I know that the National Academy of Science has 

done research of social networking analysis. Do you have any views you 

would care to share with us about the field of research? 

 DR. CICERONE. Not today. I think there is probably some 

developments that have taken place in the classified arena that I am not 

totally up on that I would like to find out earlier before I would 

comment. 

 MR. STUPAK. Is it a relatively new field? 

 DR. CICERONE. Graph theory, the kind of statistical patterns, I think 

so. I haven’t seen it applied to this kind of a field of study before. 

 MR. STUPAK. What do you think of Dr. Mann’s social network 

analysis of the paleoclimatology field? Dr. Wegman’s. I am sorry. I 

said Dr. Mann’s. Dr. Wegman’s. 

 DR. CICERONE. I have no further comment. 

 MR. STUPAK. Okay. Dr. Wegman, in looking at your report here 

today and your testimony, I am on page 6, if you would, sir, and I am 

looking at the paleo perspective on global warming. And you say these 

are contradictory statements, and I guess I am a little confused on it and 

maybe you could help us out. It says the latest--and I am quoting the 

first here, the first paragraph on page six. You got it there? 

 DR. WEGMAN. Yes. 

MR. STUPAK. “The latest peer-reviewed paleoclimatic studies 

appear to confirm that the global warmth of the 20th Century may not 

necessarily be the warmest time in Earth’s history, what is unique is that 

the warmth is global and cannot be explained by natural forcing 

mechanisms.” And it says also from the same website, and this is a 

NOAA website, “In summary, it appears that the 20th Century, and in 

particular the late 20th Century, is likely the warmest the Earth has seen 

in at least 1,200 years.” How is that inconsistent? You said 

contradictory statements. How is that contradicting? 

 DR. WEGMAN. Well, at one stage people are suggesting that it is the 

warmest and another stage it is saying it not necessarily the warmest. 

Being likely is a phrase that has been bandied about quite a bit. 

 MR. STUPAK. But aren’t those really different time frames? One is 

talking about 1,200 years, the other one is talking about the 20th Century 
732

and Earth’s history, it seems like, because one says the 20th Century and 

particularly the late 20th Century is likely the warmest, and the other one 

is talking about the earth’s history. So that is why I didn’t see it as 

inconsistent. One is talking about 20th Century, late 20th Century, and the 

other one is talking about all of Earth’s history, so that is why I didn’t see 

the inconsistency. Do you see what I am saying, those two statements? 

 DR. WEGMAN. Yes, sir, I see what you are saying. 

 MR. STUPAK. Dr. Mann, if I may ask you a question. I want to go 

back to this social network. Dr. Wegman has hypothesized that you have 

a social network of 42 other scientists and that they cannot independently 

evaluate your work because they have at various times co-authored work 

with you. This may be based on his belief that people who interact 

regularly will foster a common attitude or identity. What is your 

response to that? 

 DR. MANN. Well, frankly, I was a bit baffled by that finding. My 

profession is highly competitive. We often disagree publicly. Scientists 

disagree publicly and in our articles, with each other on certain matters, 

and yet we can co-author on other areas where we agree so there is no 

contradiction in-- 

 MR. STUPAK. Well, do you have peer review of your articles by 

people who don’t agree with you? 

 DR. MANN. I have probably had articles rejected because of reviews 

by people who were co-authors with me on other articles. In fact, I am 

quite certain that is the case. Of course, Dr. Christy and I are co-authors 

and yet there are a lot of issues in the science that we don’t agree on. So 

I was very surprised by that. I was flattered by that. The implication that 

as a post doc when I started this work back in the late 1990s that I was 

sort of the center of the entire field of climate research but it is as 

incorrect as it is flattering. 

 MR. STUPAK. You don’t dominate the thinking of the entire 

paleoclimatology community, do you? 

 DR. MANN. Well, I don’t know if I do now but I am sure I didn’t 

back in the late 1990s. 

 MR. STUPAK. My time is up. Thank you, Mr. Chairman. 

 MR. WHITFIELD. Thank you. At this time I recognize Mr. Stearns of 

Florida. 

 MR. STEARNS. Thank you, Mr. Chairman. Mr. McIntyre, you are 

the only one who doesn’t have a Ph.D. here on the table so I thought I 

would ask you this question. As I understand your background, your 

undergraduate degree is mathematics. Is that from Oxford? 

 MR. MCINTYRE. My degree in mathematics was from the University 

of Toronto but I attended Oxford subsequently. I think my stay there 

probably overlapped with that of President Clinton’s. 
733

 MR. STEARNS. Oh, good. 

 MR. MCINTYRE. I think we might have played rugby against one 

another. 

 CHAIRMAN BARTON. We hope you did a little more studying than he 

did. 

 MR. STEARNS. Well, you know, I just want to give you your due 

here. We have heard in testimony that Drs. Wahl and Ammann have 

reproduced Dr. Mann’s work and shown your criticism to be invalid, and 

I guess--is this true and were your criticism erroneous? I will give you 

an opportunity to respond to that. 

 MR. MCINTYRE. Well, a couple of points. First of all, the code that 

we used to emulate Dr. Mann’s work reconciles almost exactly with that 

of Wahl and Ammann. And so any conclusions that differ are not 

because of differences in how we have emulated the reconstruction. 

They think that certain steps are fine, we don’t. They have in my opinion 

not carefully considered the implication of bristlecones. Our codes 

reconcile so right now I am confident in our conclusions that if you 

remove the bristlecones you have a major impact on the final results. 

 Last December, I met with Ammann in San Francisco and suggested 

to him that since our codes reconciled so closely that it would make 

sense if we co-authored a paper in which we set down the points that we 

agreed on, set down the points we disagreed on in an objective way so 

that we didn’t seem to be launching missiles at one another and creating 

more controversy. I said that we could declare an armistice for 6 weeks 

until we accomplished this, and if we didn’t get to conclusion everybody 

would go back to square one and that each of us could write separate 

appendices, say where we disagreed. 

 I formally sent e-mails to him suggesting that. He told me in San 

Francisco that if he did that that that would interfere with his career 

advancement. 

 MR. STEARNS. Dr. Wegman, I am going to give you an opportunity 

to respond to some of the testimony today. The testimony of both Dr. 

Gulledge and Dr. Mann draw upon the findings of Dr. Wahl and 

Ammann to suggest your work doesn’t matter. Let me give you an 

opportunity to respond to that. 

 DR. WEGMAN. Well, I think although the social network analysis 

has been sort of dismissed the amazing thing to me is that these supposed 

independent replications of the original Mann work are done by 

Rutherford et al., which includes the top seven people in the social 

network that we identified last week. Every one of them is in there, and 

they are frequent co-authors with Dr. Mann. So I can hardly see how 

that is an independent replication of his original work. 
734

 Secondly, on Dr. Mann’s résumé he lists Dr. Ammann as one of his 

students as a co-advisor to him although Dr. Ammann does not list him 

as an advisor. But it is clear to me that Wahl and Ammann are not 

independent agents as well. 

 MR. STEARNS. And that goes to this idea of the social network you 

are talking about? 

 DR. WEGMAN. Yes. We never claimed, by the way, that Dr. Mann 

was, in 1998 as a post doc was the center of the social network. What we 

are saying is that subsequently he has 42 co-authors many of whom, 

particularly the top seven in the block we identified, who are frequent coauthors with him and co-authors with each other, and there is some 

element of thinking that if they are frequent co-authors they are thinking 

the same way. 

 MR. STEARNS. Is there anything else that you have heard Dr. Mann 

say earlier that you would like to comment on? You are welcome to go 

across the spectrum. 

 DR. WEGMAN. Well, first of all, in the question that Mr. Waxman 

mentioned about the carbon dioxide distribution, that was prefaced by a 

comment by me that I didn’t know anything about this but I suppose, for 

example, that carbon dioxide, so that was purely a hypothetical 

conjecture which I did not mean to be taken as testimony. It was also 

clear in the discussion that even Dr. North talked about a barrier of 

carbon dioxide at high levels of the atmosphere so he gave in his diagram 

an illustration that carbon dioxide was not mixed so that certainly is 

something that should be clarified. I did not mean to testify that carbon 

dioxide sat at the ground level. That certainly was not what I was saying. 

 MR. STEARNS. Any other thing that has come up that you wish to 

comment on either that Dr. Mann or others have spoken on or perhaps 

we as members have spoken on you would like to-- 

 DR. WEGMAN. Well, I stand by the statements that I have made and 

particularly in the written testimony that I didn’t get a chance to 

comment on. My own sense is that if you look at, for example, this 

matter of statistical skill, it doesn’t matter that the American 

Meteorological Society says what statistical skill is. Statisticians do not 

recognize that term. I went around to a whole dozen or so of my 

statisticians network and asked them if they knew what they were talking 

about. It is my contention that there is a gulf between the meteorological 

community and the statistical community. 

 We examined, for example, this committee that is on probability and 

statistics of the American Meteorological Society. We found only two of 

the nine people in that committee are actually members of the American 

Statistical Association, and in fact one of those people is an assistant 

professor in the medical school whose specialty is bio-statistics. The 
735

assertion I have been making is that although this community, the 

meteorological community in general and the paleoclimate community in 

particular, used statistical methods. They are substantially isolated. 

They are using our methods but not talking to us. In contrast, we are not 

doing meteorology and-- 

 MR. STEARNS. You are talking to them. 

 DR. WEGMAN. We are talking to them. 

 MR. STEARNS. I understand. 

 CHAIRMAN BARTON. Would the gentleman yield just for 

clarification, please? Dr. Mann in his testimony referred to this Dr. 

Ammann and Wahl study who said they have recentered the data and the 

conclusion is the same if I understood him correctly. Could you 

comment on that because one of your points was when you center it 

correctly the conclusions don’t follow. 

 DR. WEGMAN. The studies are done in different ways. There is the 

so-called CFR methodology, the CPS methodology, and in I believe it 

was Dr. Mann’s 2005 report he illustrates several different studies that do 

this. One of the things that is critical is the set of proxy data that you use 

when you are trying to replicate these studies. And in fact if you use a 

nice set of proxies that all have the same signal in them then it really 

doesn’t matter a whole lot what methodology you use. If you use a very 

mixed set of proxies that have some noise and different kinds of structure 

in it then it does matter what kind of-- 

 CHAIRMAN BARTON. It goes to Mr. McIntyre’s point that depending 

on the data set you use it is the result you are going to get. 

 DR. WEGMAN. That is right. 

 CHAIRMAN BARTON. If I understood him correctly. 

 MR. STEARNS. Reclaiming my time. Mr. Christy, Dr. Christy, have 

you read Dr. Wegman’s report, and, if so, what is your opinion of his 

working conclusion? I understand you are one of the individuals that 

was in the group that developed the National Research Council on 

surface temperature reconstruction of the last 2,000 years, so I would 

appreciate, Dr. Christy, your comment. 

 DR. CHRISTY. This is the short answer. I have not read the report. 

 MR. STEARNS. You have not read the report? 

 DR. CHRISTY. No, I am sorry. 

 MR. STEARNS. Okay. Dr. Cicerone, you are the President of the 

National Academy of Science. Dr. Wegman is an appointed member of 

the National Academy of Science Board of Mathematical Sciences and 

Their Application. He is chair of the NAS Committee on Applied and 

Theoretical Statistics, highly credentialed in math and statistics, wouldn’t 

you say? Shouldn’t we take his judgments on statistical matters very 

seriously, and don’t they carry significant weight? Would you say his 
736

judgment about statistical matters is important and that he has credibility 

based upon those credentials? 

 DR. CICERONE. Yes. 

 MR. STEARNS. So there is some attempt by some folks to make 

some of his findings not correct but based upon what you just said this 

man is highly credible in math and statistics and we should take his 

judgment particularly on statistical matters with a high credibility? 

 DR. CICERONE. Yes, but not on the mixing of gases. 

 MR. STEARNS. Not on the mixing of gases. All right. Thank you, 

Mr. Chairman. 

 MR. WHITFIELD. The chair recognizes Mr. Inslee. Oh, no, Ms. 

Schakowsky. I am sorry. Ms. Schakowsky. 

 MS. SCHAKOWSKY. Thank you, Mr. Chairman. I want to begin by 

referring to the end of Dr. Christy’s testimony where you drew on a 

certain kind of expertise where you were a missionary in Africa, and you 

end with a plea. And I just want to quote from the testimony. It says, 

speaking of the people in Africa you say, “They are far more vulnerable 

to the impacts of poverty, water, and air pollution, and political strife 

than whatever the climate does.” I actually found that to be a pretty 

strange comment from someone who is the chair of the Earth System 

Science Center and deal with climate. 

 And I wanted to actually ask Dr. Cicerone don’t those issues of 

certainly of water and air pollution, et cetera, are they unrelated entirely 

to issues of climate? 

 DR. CICERONE. No. Of course they are related. I don’t know what 

Dr. Christy would answer to the question of what he meant, but, yes, it is 

clearly related. 

 MS. SCHAKOWSKY. So I was really confused by that because, first 

of all, I have to tell you I resented that a little bit. I close with a plea to 

remember the needs and aspirations of the poorest amongst us when 

energy policy is made as if to say that those of us who would ask for 

some changes in business as usual and energy as usual somehow are not 

taking into consideration the poor people of Africa. So I found that a 

condescending remark, I have to tell you. 

 But are not those things--because I have to tell you, Dr. Christy, that 

precisely for the reasons of the kind of impact it will have on human life 

including drought and exacerbating poverty and even you mention 

political strife, war water actually do worry me a bit. So how do you 

segregate that from climate issues? 

 DR. CHRISTY. Was that water wars? 

 MS. SCHAKOWSKY. You said political strife. I would say that if we 

end up with a situation where people are fighting over water or limited 
737

food supplies because of drought that that could be related to the climate, 

could it not? 

 DR. CHRISTY. We don’t know what is going to happen, for example, 

with the water cycle as the climate evolves so-- 

 MS. SCHAKOWSKY. The overall statement about water and air 

pollution, are they unrelated to climate? 

 DR. CHRISTY. We know today that people die because of water 

pollution, air pollution and those other things. Those are issues that we 

know today and can assess and determine how answers and solutions can 

be found. So those are critical things to do today. And I am sorry if that 

last line came across condescendingly. When you live with the people as 

I did you know that they don’t have much of an advocacy in places. 

 MS. SCHAKOWSKY. Actually in the Congress they do have a number 

of people who care and advocate on their behalf. I wanted to get to that 

and it is a perfect lead into the Chairman’s question, and what do we 

know, this was his question, and so I wanted to look at Dr. Gulledge’s 

materials that he provided. And again I would like to ask him or anyone, 

it says in your presentation, Dr. Gulledge, human activities are increasing 

atmospheric greenhouse gases, that that is unequivocally agreed to in the 

scientific community. The Earth is warming unequivocal at an 

unprecedented rate, confident, so somewhat less. 

 Warming over past five decades caused primarily by man-made 

greenhouse gases, confident. So let me add one more preface to this 

question that I would like to put to the panel, first of all, the question of 

agreement. We have a panel here where it is three and three, so if there 

is a reporter looking at this they would say, well, there is three people 

who agree with this, three that don’t, so there is a split here. So part of 

my question is does the disagreement over your unequivocal, 

unequivocal, confident on this panel reflect the scientific community in 

any kind of accuracy. And I would like to just question these 

unequivocal and confident ratings. 

 DR. GULLEDGE. Well, I am not sure if you are describing the panel 

as being three against three on whether they agree with these statements 

or not, but I suspect that it might not fall out exactly that way. 

 MS. SCHAKOWSKY. Okay. 

 DR. GULLEDGE. It might vary among some of the lower statements 

and then-- 

 MS. SCHAKOWSKY. Then let me ask this, let me ask the panel. Is 

there anyone who disagrees with the unequivocal--that it is unequivocal 

that human activities are increasing atmospheric greenhouse gases? Is 

there anybody? Okay, good. That the Earth is warming? Okay. And at 

an unprecedented rate? 

 DR. CHRISTY. What is the confidence level on that? 
738

 MS. SCHAKOWSKY. Confident. 

 MR. MCINTYRE. I don’t know that it is unprecedented. 

 MS. SCHAKOWSKY. Actually I wanted to ask you--I hope you don’t 

think this sounds rude but when I looked at the witness list I see, you 

know, everyone has got kind of a credential and then it just says your 

name, so I wanted to ask you about your credentials, Mr. McIntyre, and 

perhaps it gets into social networks because when I asked for your 

resume what I found was: for the last 16 years I have been an officer and 

director of several small public mineral exploration companies, previous 

to that I worked for a large international mining company, and that 

mainly it is your experience in mineral exploration industry that you tout 

in your resume and your background. I don’t know if that gets to social 

networks or not. 

 MR. MCINTYRE. Well, in this case this has nothing to do with any 

work that I have ever done. I just became interested in it as a citizen 

when I read the studies, and I thought that politicians were facing 

difficult policy decisions so I thought that it would be interesting to 

examine one particular paper which was being cited by the Canadian 

government. It wasn’t clear to me how people knew that 1998 was the 

warmest year in the millennium, and I was just interested in how-- 

 MS. SCHAKOWSKY. So are you qualified to make a judgment on 

whether or not the Earth is warming at an unprecedented rate? 

 MR. MCINTYRE. For the things that I have published on, my 

statistical and mathematical skills are adequate for what I have published 

on. The findings that we have had about principal components have 

been-- 

 MS. SCHAKOWSKY. But are you qualified to comment on whether or 

not the Earth is warming at an unprecedented rate? 

 MR. MCINTYRE. Well, you asked whether the people knew or didn’t 

know. I am just saying I didn’t know. 

 CHAIRMAN BARTON. Will the gentlelady yield? 

 MS. SCHAKOWSKY. Yes. 

 CHAIRMAN BARTON. That group is much more qualified than I am 

to comment on these things, and yet I have the responsibility as 

Chairman of the committee to put the bill together to change the way 

Americans work every day if we decide to do something about it. 

 MS. SCHAKOWSKY. Absolutely. Absolutely. 

 CHAIRMAN BARTON. The least qualified--I will stipulate-- 

 MS. SCHAKOWSKY. And me too. I am with you. 

 CHAIRMAN BARTON. The quality of the commenters is more on that 

side of the dais than at least it is in the Chairman’s chair. I am not going 

to comment on anybody else’s qualifications but in a democracy 

anybody with an opinion is entitled to express that opinion and some are 
739

more qualified than others obviously because of their credentials, but I 

don’t think we have a standard of witnesses that says unless you have a 

Ph.D. you cannot testify before-- 

 MS. SCHAKOWSKY. Well, actually we are having a--reclaiming my 

time. Actually we are having a conversation today about the science 

here so it is not just about opinion, and it is relevant, I think, to talk 

about. And Dr. Wegman has been pretty up front about what he is 

qualified to testify to and what he is not, and I think that that is fair and it 

is fair to ask for individual’s backgrounds and what their connections or 

interests might be. That is the kind of conversation that we are having. 

 But what I really wanted to get to was your question about what is it 

that we know, and if there is pretty wide agreement or no comment 

because you don’t know that human activity is increasing atmospheric 

greenhouse gases and that the Earth is warming and that it has certain 

consequences. Mr. Chairman, when you said that you are a skeptic the 

difficulty of the task at hand to me is not a reason to be a skeptic about 

the science. 

 Admittedly, this is a daunting task, and we heard about the 1,000 

nuclear power plants or whatever it could take, but we also heard 

practical suggestions from Dr. Cicerone about energy efficiency that we 

could make a start on this. And so if there is widespread agreement that 

human activity is contributing to this that this climate--that the warming 

of the climate is happening, that it can have very detrimental effects. I 

am anxious to understand why we don’t just move toward solution at this 

point, and that is what I really was getting to so I have over stepped my 

time, and I thank you, Mr. Chairman. 

 MR. WHITFIELD. Thank you. And at this time I will recognize Mrs. 

Blackburn of Tennessee. 

 MRS. BLACKBURN. Thank you, Mr. Chairman, and you all are very 

patient with us. As I said in my opening remarks, I think a lot of this is 

born out of curiosity of knowing what the truth is and being able to have 

some answers. And I will tell you one of the reasons I have such an 

interest in this. I have a mom who is 81 years old who has been very 

involved in conservation efforts all of her life. She won the Keep 

America Beautiful Lifetime Achievement Award here about 15 years 

ago, and she is very careful in her instruction to her children and her 

grandchildren that one of the things we have to be very careful about is 

environmental extremism which many times hurts our argument for 

actually being good conservationists and leaving this Earth in better 

shape than we have found it. 

 And so when we have studies that seem to go around the horn and 

then they can’t be substantiated and they are coming out as government 

proof as something it does cause us questions. And as I mentioned, we 
740

have been through this thing and we have talked about it and I have 

talked about how when I was growing up in the 60s that, the thing was 

that it was going--we were going to be in an ice age or have a return of 

the ice age. And then I guess that there were some schooled scientists, if 

you will, some of your colleagues maybe who found that that was not 

going to be so. 

 So I think it is important that we have the opportunity to visit with 

you and find out what is an item of agreement and what is not an item of 

agreement. And, Dr. Mann, if I could have your attention for just a few 

moments if you don’t mind, I would like to direct my question, my 

opening question, to you. You have said that other studies have 

confirmed your results, but it does not appear that their statistical 

analysis has been thoroughly examined, and I wanted to know if you 

would be open to a review by an independent team of top statisticians of 

climate change papers before those papers get published. 

 You know, I think Dr. Christy had mentioned that in some of his 

work there were some flaws that were found. He mentioned that in his 

testimony and then they submitted to that. So if we are going to put 

government money into papers should they be reviewed by others other 

than your social network before they are published with government 

funds and considered to be the truth? 

 DR. MANN. Well, I think there is a misunderstanding about the 

nature of peer review as it currently exists with scientific journals, and 

there have been some misstatements along these lines in the previous 

comments by some of the others on this panel. For example, two of the 

studies that have shown that the centering convention in PCA doesn’t 

make a difference in the reconstruction as shown also by Dr. Gulledge 

were done by groups that are entirely independent of me and my 

collaborators, von Storch and Zorita. In fact, von Storch and Zorita and I 

and my collaborators have had vigorous disagreements in the peer 

reviewed literature. 

 So one of the studies that actually validated our approach in showing 

that the centering convention doesn’t make a difference was by that 

group. Another scientist at Woods Hole, Peter Huybers, if I could finish 

that, also came up with the same result so there are four different studies, 

only one of which I was connected with that came to that conclusion so 

the peer review process is actually working quite well. 

 MRS. BLACKBURN. My question to you is do you think that they 

should be submitted for independent review before they get published? 

 DR. MANN. Well, that goes on so again it requires an understanding 

of what the peer review process at the major scientific journals actually 

is. For example, with Nature and Science when they receive a paper that 

involves both statistics and climatology you can be certain that they will 
741

seek out leaders in the world’s scientific community in all of the relevant 

areas before they make a decision about the publication of that paper, 

and that is standard in most of the leading journals. 

 MRS. BLACKBURN. Now let me ask you this then. If your work 

were submitted to an independent group and they had questions or found 

items that needed to be changed would you be willing to make those 

changes prior to that work being published? 

 DR. MANN. Again, as I have tried to convey to this committee in my 

earlier testimony and some of my earlier responses to questions, in fact, 

that has been going on for more than 10 years now. My collaborators 

and I have been re-examining the data. Other groups have been reexamining the data, testing different methods, testing the methods with 

climate models simulations, figuring out which methods perform well, 

which methods don’t perform so that process is ongoing. It has been 

going on for more than a decade now and that is how scientific progress 

works. 

 MRS. BLACKBURN. Thank you. Dr. Wegman, your thoughts on 

those questions? 

 DR. WEGMAN. Well, I think, first of all, we disagree on, you know--

Dr. Mann did not answer your question which was if-- 

 MRS. BLACKBURN. Absolutely he did not answer my question. 

 DR. WEGMAN. If you would submit to a statistical review panel, 

would you be willing to do that. He did not answer that question. And 

one of the troubling aspects of this paleoclimate and the meteorological 

community in general is that they don’t have interaction with statistical 

people even though they used statistical methods heavily. We have 

examined this group in general as I mentioned before with Mr. Stearns. 

We have tried to examine this to see the engagement of the 

meteorological community, the paleoclimatology community with the 

statistical community, and it is almost non-existent, so they are not 

interacting with our group although they are using methods that are 

based in the statistical literature. 

 I would like to see, frankly, I would like them to be engaged with us. 

I think it would be a good idea. What we were trying to do in our 

testimony was create a path to a better way of doing the science 

essentially saying that these are two groups that should be interacting and 

in some sense it behooves the meteorological community to be 

interacting with us. They are using our methods. We are not using their 

methods. So I think it would be an important thing to do and I-- 

 MRS. BLACKBURN. Let me ask you very quickly too, I had Michael 

Crichton’s testimony that he had before the Senate. Let’s see, I think this 

was in ‘05. And he was talking about having a--that government grants 

should require a replication package which would provide some 
742

transparency as part of their funding where posting that package online 

so that saying that if it is funded with government money there is no 

reason to exclude anyone from reviewing the data that is found in 

research. Is that the type thing that you think would be appropriate for 

transparency? 

 DR. WEGMAN. As I said last week in one of our conclusions, 

basically when there is important public policy and human health 

implications this stuff ought to be subject to exceptionally more intensive 

review. We drew the NIH model out last time talking about the FDA 

and how the FDA requires some statistical consultation just to that the 

drug issue, and it seems to me that in this climate arena this has 

incredibly important implications for society in general, the world in 

general, and I think it ought to be carefully reviewed. The fact is Dr. 

Mann continues to appeal to peer review but the fact is the peer review 

process failed in the 1998 paper. 

 MRS. BLACKBURN. And you would say that was primarily because it 

was not an independent and separate review outside of that social 

network? 

 DR. WEGMAN. I believe that is the case. 

 MRS. BLACKBURN. Okay. Thank you very much. Dr. Christy, let 

me ask you this. There is an article we have gone to a couple different 

times in my office, Energy, Environment and Economics. It was Dr. 

Soon wrote an article, Ten Myths of Global Warming. I don’t know if 

you have seen that or not. Are you-- 

 DR. CHRISTY. Sorry, ma’am. I haven’t seen it. 

 MRS. BLACKBURN. Okay. I know there is so much here that has 

been written. We have killed a lot of trees using all this paper, haven’t 

we? Okay. And he talks about showing the Medieval Warm Period, and 

I was going to ask you to comment on this but since you have not and my 

time has basically expired I will just let that pass. And I thank you. 

Thank you, Mr. Chairman. 

 MR. WHITFIELD. Thank you. At this time I recognize Mr. Inslee for 

10 minutes. 

 MR. INSLEE. Thank you. I think this really is an amazing hearing. It 

is amazing because all six people at this table have all agreed on the 

fundamental thing that this Congress has got to figure out, and that is 

whether CO2 is going up, whether humans are partially responsible for 

that, and whether that is part of the reason the Earth is getting warmer. 

That is the fundamental issue that Congress faces. And all six people at 

this table agree with those propositions so I have been asking myself why 

if we have unanimity on the fundamental question that we got to ask, has 

Congress not done diddley to do anything about this, and I think the 
743

answer is fear, because we fear our inability to deal with it we blind 

ourselves to the science. 

 And I think it is a little bit like a person who is shown an X-ray of 

their lung cancer, refusing to believe it because they don’t want to deal 

with it. And I think that is a pretty good metaphor of what is going on 

right here. I want to ask Dr. Cicerone, because I think he represents 

President of the National Academy of Science, how many scientists are 

involved in that organization, by the way? 

 DR. CICERONE. About 2,000 members, but our work is done largely 

by another 6,000 people who are chosen from expertise from different 

fields who are non-members. 

 MR. INSLEE. So I figure there is somewhere between 6,000 and 

8,000 scientists that you represent here today, and I am impressed by 

that. The consensus as I understand it in the scientific community is that 

smoking causes lung cancer on a more probable than not basis in certain 

instances. Is it the scientific consensus now on a more probable than not 

basis that increasing CO2 is associated with global climate change and 

that humans are responsible for increasing CO2? 

 DR. CICERONE. Yes. 

 MR. INSLEE. So we can say that we have the same level of 

probability in our belief as to what humans are doing to raise 

temperatures or at least that both are above 50 percent as we do about 

lung cancer, is that a fair statement? 

 DR. CICERONE. I think we understand the mechanics of CO2 and 

climate better than we do of what causes lung cancer. 

 MR. INSLEE. So here we as a country have decided to try to limit and 

reduce the tremendous damage that is done by lung cancer, but we have 

got as good or better science on a global cancer and this Congress hasn’t 

done a single thing to deal with that, and I think that is very, very 

disturbing. Now could I put a slide up here, please, gentlemen, if we 

can? I want to ask Dr. Cicerone to explain something to us. 

 If we look at this slide it is going to show the cyclical nature--that is 

not actually the one I want. Yes. If we look at this slide here it shows 

the cyclical nature. It is from Dr. Gulledge’s slides. It will show the 

cyclical nature going back 450,000 years ago moving forward to today. 

We also see CO2 going down, back up, down, back up, down, back up, 

and we show a natural variability that has occurred before the industrial 

age of from about 190 parts per million to about 290 parts per million, 

and I think that is what Dr. Cicerone referred to as the natural variability 

that has occurred before we started burning coal, oil, gas, and wood. 

 Now what I see since the industrial period I have seen this vertical 

curve go up, and it is vertical since the beginning of the industrial period, 

so that now we are at a level, this says about 372. I actually think it is 
744

about 382 today. And as I understand it, it is bound again on about a 

vertical curve on this scale to levels of about 550 PPM double, double 

the highest level of CO2 in pre-industrial ages back 450,000 years. 

 So is my understanding of that, Dr. Cicerone, basically accurate that 

we have an accelerated rate of CO2 that will end up about twice as high 

carbon dioxide, which is a known heat trapping gas in our atmosphere 

that is occasioned since the dawn of the pre-industrial age? 

 DR. CICERONE. Yes, although I don’t think it is necessary that we 

will end up at double CO2. And then also we don’t know for sure what 

happened before this time. This is the longest instrumental record we 

have of real data. 

 MR. INSLEE. So this is going back as far as we can with real data. 

We are at higher levels by about 130--excuse me, more than that, about 

170 parts per million, is that a fair statement? 

 DR. CICERONE. Above the minimum, yes. 

 MR. INSLEE. Now the projections I have seen would suggest that if 

we continue to spew carbon dioxide and methane into the air or carbon 

dioxide into the air the best assessments I have seen we will end about 

double pre-industrial levels by the end of the century. Could you give us 

your best estimate of that or comment on that at all? 

 DR. CICERONE. Oh, by the end of the century. It depends on human 

population. It depends on our energy usage and what technologies we 

are using to produce the energy so you have to make assumptions about 

human population, how much energy we will use, and what the 

technologies will be. Double CO2 is certainly plausible. It really 

depends on what humans do. 

 MR. INSLEE. And it depends on what this Congress does, and what 

Congress should do is what British Petroleum has done. British 

Petroleum 7 or 8 years ago decided they were going to meet Kyoto 

targets. Maybe it was 5 years ago. And in 3 years they met their Kyoto 

targets in their internal operations. They reduced their CO2 as much in 

their internal operations as the Kyoto targets would require. You know 

what they did? They saved $350 million in wasted energy when they 

decided to adopt efficiencies of the type that Dr. Cicerone talked about. 

 The other thing we will do is try to get these plants started. Right 

down the hallway here yesterday I met with these guys, Iogen 

Corporation. They are going to open up the first cellulosic ethanol plant 

in southeastern Idaho. When they do that, we will power our cars on E85 ethanol. We will reduce our CO2 emissions per mile by 80 percent or 

more. They actually think it may actually be negative because of some 

of the stuff you grow actually takes carbon out of the air and puts it into 

the soil. It might actually be negative. 
745

 This is the kind of thing we need to do, and we are not going to do 

that until we come to grasp what this science really is. I want to ask--I 

think there is just such an overwhelming consensus of--I will just read 

the Academy of Science report. “The IPCC’s conclusion that most of the 

observed warming of the last 50 years is likely to have been due to the 

increase in greenhouse gas concentrations accurately reflects the current 

thinking of the scientific community on this issue.” That is a direct quote 

from the National Academy of Science. Now there has been some issues 

brought about Dr. Mann’s studies. There has been some questions about 

Dr. Christy’s studies. I frankly think there are some legitimate questions 

about the statistical assessments, and the first one Dr. Mann did, I think 

they have been changed a little bit since then, I think the same could be 

said for Dr. Christy, but I guess the question I have, Dr. Cicerone, if Mr. 

and Mrs. Mann had never met and we never had the services of Dr. 

Mann, would that have varied the conclusion of the National Academy of 

Sciences on these fundamental questions? 

 DR. CICERONE. You must be referring to his parents and not his 

wife. 

 MR. INSLEE. I am indeed. 

 DR. CICERONE. I don’t think so. 

 MR. INSLEE. And why do you say that? In other words, if Dr. 

Mann’s work had just never appeared, and, by the way, I respect it and I 

think it has added to the debate but if his work had never occurred why 

do you think the Academy of Science would still reach the same 

fundamental conclusions? 

 DR. CICERONE. Because of the blending of the physical evidence, 

the mathematical rigor and the comparisons that can be made now with 

the predictions and the actual records of the last 30 years especially. 

 MR. INSLEE. And I have a chart here, gentlemen, if you can put it up 

here of ice core data. I think it might be the last slide on the series that I 

had introduced. If you have the groupings of the one that I had brought 

today. This is just another representation of the CO2. There should be 

one more slide. You are not finding it right now. Let’s keep going. Just 

go through these quickly. Right there. Okay. This is a slide basically 

showing ice core data and we show CO2, and if I can read this basically 

this is methane at the top, carbon dioxide here, from ice core data 

showing these levels, only it goes backwards. These are today’s dates. 

This goes back 400,000 years. These are today’s dates showing CO2

levels higher in ice core data than at any time in the last I believe it is 

400,000 years. It should be 600,000 years. 

 If you can, Dr. Cicerone, can you describe how that ice core data 

work through the deuterium isotopes, if you can just give us a quick 

description. 
746

 DR. CICERONE. I mentioned earlier the way the gases are pulled out 

of these dated ice cores. With CO2 you can do it two ways. With 

methane you can do it two ways. With nitros oxide you get similar 

results, low when it was cold, high when it was warm. The deduction of 

temperatures at the same time depends on the different isotopes, the 

different forms of the same chemical like carbon, the same element in 

carbon, in this case oxygen and hydrogen where because the way they 

evaporate a gas like water evaporates differently if it has heavy hydrogen 

in it, deuterium, for example, or oxygen 18 instead of O-16. 

 We can go back and infer what the temperature was in the vicinity of 

the ice when it formed or the snow in this case which later becomes ice. 

These records are pretty widely used now, and under certain 

circumstances they are absolutely the best we can do. They are very 

quantitative. The statistics are clear. There is some concern over 

whether the temperature at which the snow formed that made the ice was 

really a global or a hemispherically average temperature or did it just 

reflect what was happening regionally, but there you can go into how 

much O-18 was in the oceans and the changes are big enough that you 

can infer a pretty good geographical validity of these temperature 

deductions as well as the carbon dioxide. 

 MR. INSLEE. Thank you, and thank you all for your testimony today. 

 MR. WHITFIELD. We may just have a short second round here. I am 

going to recognize the Chairman of the full committee for 5 minutes. 

 CHAIRMAN BARTON. Yeah, and I have to go so I apologize for 

going out of order. This is today’s USA Today newspaper, the 

temperature map on the back. It shows the high temperature was 126 

degrees Fahrenheit and the low temperature was 43 degrees Fahrenheit. 

That is yesterday. Is there a model in existence that can replicate this 

with any degree of accuracy? This is yesterday’s temperature. Dr. 

Mann, do you have a model that can do that? This is just one country. 

 DR. MANN. I personally do not. 

 CHAIRMAN BARTON. We have got an 83 degree difference on one 

day out of 365 days in one country. 

 DR. MANN. If I can just talk a little bit to that. 

 CHAIRMAN BARTON. I only have 4 minutes and-- 

 DR. MANN. I will make it quick. 

 CHAIRMAN BARTON. Dr. Christy, you are the meteorologist, I think, 

for Alabama. Do you have a model that could even do this in Alabama? 

 DR. CHRISTY. No, sir, we wish we did. 

 CHAIRMAN BARTON. Okay. Now did you want to comment, Dr. 

Cicerone? 

 DR. CICERONE. I would. Chairman Barton, you said any degree of 

accuracy. That gives us some room. The British meteorological office is 
747

probably the world’s best. They are in the Ministry of Defense in 

England. Their models have pretty good predictive capability. If you 

average over a few days and you say let’s not argue about the difference 

between San Francisco and Marin County or San Antonio and El Paso. 

If you average over enough space in time they can hit that. The models 

at Penn State University are excellent. The National Weather Service 

can give you some degree of accuracy and predictability, and they can 

reproduce a lot of those patterns. 

 CHAIRMAN BARTON. Well, my point is, and I am not trying to be 

cute about this, in preparing for last week’s hearing I read the summary 

and I read most of the report of the National Academy of Sciences here, 

the National Research Council. I read Dr. Wegman’s report. And 

somewhere in those two reports it said the data sets they use to base all 

these models on in the whole world there are like 60 or less data sets. 

There are just not a lot of data, and we are trying to make predictions 

over thousands of years. Even where we have really good records for the 

last hundred years, and some of the most advanced satellites and smart 

people that put these computer models together with hundreds of 

variables, we can’t really predict after the fact yesterday’s weather with 

too much accuracy, and yet to go to Dr. Christy’s point if we accept 

Congressman Inslee’s point that we need to be in solution mode a 

thousand nuclear power plants by themselves is a trillion and a half 

dollars, and that will get you a CO2 reduction of 10 percent. 

 There are somewhere between 5,000 and 10,000 power plants in this 

country. Now I don’t know exactly but I know there are only 100--I 

think 112 operating nuclear plants of those between 5,000 and 10,000. 

And that is just one part of the economy. We have got 300 million cars 

and trucks. We have a lot. I mean, it is not scientifically accurate but we 

have got a boon’ doggle worth of economic consequences if we really go 

where Mr. Inslee says we ought to be going. And I am not dogmatic 

about it. I am concerned when I hear Dr. Cicerone say that the parts per 

billion of CO2 in the atmosphere is 100 parts per million higher than it 

ever has been. 

 Now that has got to give anybody pause to think, but I look at all 

these charts and all these data sets and I can’t back it up, but it would 

certainly appear to me to be plausible, to use that term again, that the 

Earth is always changing temperature. It is either in a warming period or 

a cooling period. It appears that it is a curve function. It appears that it 

is over the same general period of time and it certainly appears that in the 

last 100 years that the upward curve has accelerated at a more rapid rate 

than say a thousand years ago. But it is not clear what, if anything, we 

can do to change that basic system. And so before we go off the deep 

end I really do want to make sure that these models are independently 
748

reviewed and really are scientifically accurate and really can be 

replicated. And I really do want to know what the confidence levels are. 

We are going to get to problem solution, and we are going to have a huge 

debate about that. But since we can’t even predict with much accuracy 

what yesterday’s temperature was, it is a little bit much to ask us to make 

multi-trillion dollar decisions on models that 10 years ago when Dr. 

Mann put out his report, he was the first one, and even today most of the 

people that are doing the modeling are some part of his network, which is 

not a bad thing. It shows you operate with a lot of smart people that care 

a lot about the environment. 

 But it doesn’t mean that the United States government makes trillion 

dollar changes in public policy until we get a little bit more information 

about that, and that is why we are doing these hearings. And so I 

apologize for going another minute over but I thank you, Mr. Chairman, 

for holding this, and I thank the members, Mr. Inslee and Mr. Stupak and 

Mrs. Blackburn for being here. I wish every member of the Oversight 

Subcommittee was here. I wish we had more intensity on this so that we 

could get more involved. Thank you, Mr. Chairman. 

 MR. WHITFIELD. Thank you. Dr. Mann, did you want to make a 

comment? 

 DR. MANN. I just wanted to clarify a distinction here in this 

discussion. On the one hand we are talking about weather, and that is the 

day-to-day fluctuations and the character of the atmosphere, and in the 

other cases we are talking about climate and there is a very important 

distinction between the two. Climate is the statistics, the long-term 

statistics of the weather, and there are certain things that we can say very 

well about climate. 

 CHAIRMAN BARTON. But your model is predicting temperature 

change. 

 DR. MANN. It is not a model. 

 CHAIRMAN BARTON. That may be the variable but that is the 

variable, and we are talking about catastrophic consequences with 3 to 4 

degree Fahrenheit changes. 

 DR. MANN. That is the point. It is not a model. A model is a set of 

numerical equations that we try to solve the equations that describe the 

atmosphere and the ocean. Our reconstructions aren’t that. They are not 

a model. The models are a completely different thing, and there are 

weather forecasting models as well as climate models, and in certain 

things the climate models are quite good. We are doing very well now in 

predicting El Ninos. 

 CHAIRMAN BARTON. What term should I be using? Not model. 

Program, algorithm? 
749

 DR. MANN. They are statistical reconstructions and data and then 

there are the models, and I just wanted to make that distinction. 

 CHAIRMAN BARTON. I stand corrected. 

 MR. WHITFIELD. I just have one other question I would like to ask 

because we have heard a lot today about core samples, and I have been 

sort of interested in this chart that Mr. Inslee brought in showing CO2

concentrations and from that extrapolating temperatures. And I would 

just ask Mann and Christy and Cicerone once again, I didn’t really ask 

this question before, but I would like for you to tell us the facts about the 

reliability of the ice core samples. And we have heard a lot of comments 

about using that to determine CO2 and then the question is using ice core 

samples as historical thermometers. Can they really be considered 

accurate thermometers. Can you take those CO2 levels from ice cores 

and extrapolate in an accurate way? 

 DR. MANN. I will take the first stab at that. There are certain 

physical processes and there are basic physical processes that control the 

ratio of different isotopes, of oxygen in the ice, the water that is in solid 

form, it is ice trapped in those ice cores, and so it is on a somewhat 

different footing from some of the other sorts of proxies like tree rings 

that we use where we are relying on some biological relationship. 

 In the case of ice core isotopes it is really physics. It is physics that 

is controlling the ratio of the different isotopes of oxygen and that is 

telling us something about the sea surface temperatures when the water 

evaporated from the ocean because the ice that is deposited at some point 

had to evaporate from the ocean surface. It also tells us something about 

the local conditions when the ice was deposited. Both the evaporation 

and the deposition depend--they influence the ratio of those isotopes. 

 DR. CHRISTY. Just in terms of the temperatures, reproducing 

temperatures from them? 

 MR. WHITFIELD. Yes. 

 DR. CHRISTY. The closer you get to the poles, the better the 

temperature relationship is. I think in the NAS report we show six 

tropical and Tibetan ice cores and they are all different. All six of them 

are different. But the closer you get to the poles the relationship looks a 

lot better there. 

 MR. WHITFIELD. Okay. Do you have anything to add, Dr. 

Cicerone? Okay. Yes. Mr. Waxman had asked we enter into the record 

the remote sensing system letter which we will do and you asked about 

the interface stewardship alliance which we will do. And then we are 

going to keep the record open for 30 days. And does anyone else have 

any comments? 

 MR. STUPAK. If I may, Mr. Chairman. We were talking earlier, I 

was going to start off my questioning and we were talking about the 
750

Fortran, and I was joking with the Chairman so I forgot to ask these 

questions. Dr. Wegman, in your report you state that, and I am quoting 

now, “We judge that the sharing of research materials data and results by 

Dr. Mann was haphazardly and grudgingly done.” You also go on to 

state that Dr. Mann--you had trouble reading Dr. Mann’s code in part 

because it was in Fortran and that you had trouble understanding some of 

the data that Dr. Mann used. 

 Did you or your co-authors contact Mr. McIntyre and get his help in 

replicating his work? 

 DR. WEGMAN. Actually, no. What I did do was I called Mr. 

McIntyre and said that when we downloaded his code we could not get it 

to work either, and it was unfortunate that he was criticizing Dr. Mann 

when in fact he was in exactly the same situation. Subsequently, he 

reposted his code to make it more user friendly and we did download it 

subsequently and verified that it would work. 

 MR. STUPAK. And then after you re-downloaded and verified it 

worked, did you have any further contact with Mr. McIntyre then? 

 DR. WEGMAN. Well, as I testified last week, Dr. Said and myself 

had gone to one of the meetings where he was talking, and we spoke 

with him but did not identify who we were at the time. This was early in 

the phase. Subsequently, I had had no contact with him until basically 

last week. 

 MR. STUPAK. Okay. Any of your co-authors that you know of, Dr. 

Said or any others, have contact with Mr. McIntyre other than that one 

time at this convention or wherever he was speaking? 

 DR. WEGMAN. One of my graduate students, John Rigsby, who did 

the code for us, worked the code for us, did have some interaction with 

him in order to verify some of the details of the code. 

 MR. STUPAK. So you, Dr. Said and this Mr. Rigsby would be the 

people who had contact with Mr. McIntyre then? 

 DR. WEGMAN. That is correct, yes. 

 MR. STUPAK. Thank you. Nothing further. 

 MR. WHITFIELD. Mr. Inslee, do you have any-- 

 MR. INSLEE. I just want to comment in response to Chairman 

Barton’s comment about the 1,000 or 10,000 nuclear plants he posited 

might be necessary. I really--and I don’t want to get in debate about 

nuclear but I am really much more optimistic about that, and the reason I 

say that is that we have been so successful in improving the efficiency of 

our economy because of the intellectual capital of men and women like 

you who have helped us develop technologies to be much more efficient. 

Let me give you an example. 

 We actually per unit of gross domestic product use almost half as 

much energy as we did in 1973. You think about that. Since 1973 our 
751

economy produces twice as much domestic product with the same 

amount of energy that it did in 1973, and there is just no reason on this 

green Earth that all of a sudden we got stupid, that we are not going to be 

able to continue as the most brilliant society on Earth and innovation to 

continue those efficiency innovations. 

 And they are not rocket science. Three of my neighbors drive cars 

that have already reduced their transportation related CO2 by 50 percent. 

The Chairman talked about the need to reduce our emissions by 40 

percent to meet Kyoto. Three of my neighbors and myself, I may add, 

have already reduced ours by 50 percent in our transportation sector. 

Simple. They are on the lots today. This is no new technology. So I just 

want to say in partial closing that I am a person, as my comments have 

indicated, who believe this is a major challenge for us and that we have 

to act, and it is well past the date where we need to move to solutions 

rather than debating the problem. 

 But I also believe that I am an optimist because I totally believe it is 

in the human--it is capable because of our intellectual ability to invent 

our way out of this pickle. And those who are people of great faith, 

because the faith community is now becoming engaged in this debate, 

because we are stewards of God’s creation, and they are starting to urge 

Congress to act as well. We also ought to be optimists and believe we 

can do it. 

 And I got to tell you, in the last 3 weeks I have met five people, one 

in cellulosic ethanol, one in wave power, one in efficiency in cars, one in 

efficiency in airplanes the Boeing 787 we are building in Seattle is going 

to get 20 percent better fuel mileage than their last model. These are the 

kind of things that America is going to do when we tackle this. So I just 

hope that this is a first step toward moving just one quick question, Dr. 

Cicerone. I have heard there has been some new evidence about finding 

large amounts of energy in the ocean that has suggested that this is sort 

of new research to indicate in the last 12 months. Is this something I am 

dreaming or is there new research in that regard? 

 DR. CICERONE. Maybe methane clath rates would be the only thing I 

am-- 

 MR. INSLEE. I am sorry. What I mean is as far as we found 

temperature increases in the oceans that have-- 

 DR. CICERONE. Oh, yeah. The result was reported about a year and 

a half ago about over the last 40 or 45 years the oceans, the upper 700 

meters or so have warmed up, and I summarize it very briefly in my 

testimony, yes. 

 MR. INSLEE. And I will put in the record a study called Penetration 

of Human-Induced Warming into the World’s Oceans. It is published in 

Science in July, 2005. Many people thought this was sort of the nail in 
752

the coffin of skeptics about global warming. And again thank you for 

your testimony. 

[The information follows:] 
753
754
755

 DR. GULLEDGE. Mr. Inslee, if I may just may make a comment. 

Also regarding Mr. Barton’s comments, I realize he is gone. I am also 

from Texas and I use scientific terms from down there. There are whole 

passels of money to be made on alternative energy, and it is not just 

about being expensive. Also, there are real serious costs to inaction that 

have not been figured into this equation here. 

 MR. INSLEE. And I just want to compliment the Chairman’s humor 

about this. As I was walking off the field at the baseball game this year 
756

and he was at third base, and I just pulled my hamstring. As I was 

walking by he says, well, Inslee, I suppose that was because of global 

warming too. So he has a great finely tuned sense of humor and we will 

look forward to using it as the debate goes on. Thank you. 

 MR. WHITFIELD. Thank you, Mr. Inslee. I would like to stipulate 

that in my district we just opened up two new ethanol plants as well. So 

I want to thank you all very much for your patience. We got documents 

to enter here. 

 MR. STUPAK. Mr. Chairman, that is a request to put in an abstract of 

an article. I would suggest we just get the whole article, put it in there, 

and then we have the complete article for everyone to see. 

 MR. WHITFIELD. Okay. Without objection. 

 MR. STUPAK. That can serve as a place holder until I get the whole 

article. 

 MR. WHITFIELD. So ordered. And then we will keep the record 

open. Mr. Inslee. 

 [The information follows:] 
757
758
759
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MR. INSLEE. Mr. Chairman, I would like to submit an essay. It is 

published in Science called the Scientific Consensus of Climate Change. 

It relates to that 928 papers as well as the article I just made reference to. 

Thank you. 

 MR. WHITFIELD. Okay. Without objection. And we will keep the 

record open for 30 days. 

 [The information follows:] 
762
763

 MR. WHITFIELD. Thank you all again for your testimony. We look 

forward to working with you as we move forward. That concludes 

today’s hearing. 

 [Whereupon, at 6:48 p.m., the subcommittee was adjourned.] 
764

RESPONSE FOR THE RECORD OF DR. MICHAEL E. MANN, ASSOCIATE PROFESSOR AND 

DIRECTOR, EARTH SYSTEM SCIENCE CENTER

Question No. 1. I understand that although your current practice is to make your 

computer code available publicly, many researchers in your field do not do so. 

Although computer code may not have commercial value, why would a researcher 

not want to release his code? 

Answer: 

 This is a question that my colleagues and I have wrestled with over the years. As 

the question acknowledges, for the past five years or more, my colleagues and I have 

made public our computer codes, just as we made public our code for the 1998 study last 

year. Our decision to make our code public comes at a time when there is increased 

standardization in codes, and the need to tailor codes to accommodate the various and 

often idiosyncratic computer systems that were used in the 1990s has diminished. But 

even today, many, perhaps most, climate scientists do not share their codes. In my view, 

there are legitimate reasons for reaching that decision, even though it is not the decision 

my colleagues and I have made. 

 For one thing, most code is written to enable scientists to perform specific functions, 

and thus code is generally written in a form of short-hand that is not easily understood by 

others. To make code usable by other researchers, the code writer has to undertake 

significant additional work, in the form of documentation, testing for potential platform 

dependence, tidying, and so forth, that places a significant burden on the code writer. 

Many scientists do not think that undertaking that additional burden is worth it. 

 Second, access to computer codes is not necessary to replicate a study. I realize that 

some of my critics have argued otherwise, but it is just not the case that scientists need 

access to computer codes to replicate studies. As I tried to make clear in my testimony 

before the Committee, a study may be replicated if the scientists conducting the initial 

study make available both the underlying research data and an algorithm that gives a 

step-by-step account of how that data was analyzed. As my testimony pointed out, the 

1998 and 1999 work by my colleagues and me was recently replicated by a team of 

scientists (Wahl and Ammann) who did not have access to our codes, but who were able 

to replicate our work without difficulty. So replication does not depend on access to 

computer codes. 

 Moreover, scientists, like entrepreneurs, corporations, and others engaged in the 

production of intellectual capital, are competitive, and rightly so. Competition in the 

marketplace of ideas is what science is all about. We would all like to make our greatest 

possible contributions to advancing the forefront of our scientific disciplines. Indeed, we 

are rewarded (in terms of grants, promotions, academic recognition, and do forth) in 

proportion to the contributions we make in the advancement of science. Asking scientists 

to release their codes before they have had an opportunity to apply them to a number of 

potential interesting problems is asking them to sacrifice their competitive advantage. 

This would be no different than asking Microsoft to release the code for its latest 

operating system as soon as it reaches the market. Microsoft is not about to do that, and 

most people would consider a requirement that Microsoft freely dispense its intellectual 

property --- its codes --- as antithetical to the principles of a free market. The argument is 

no different in the case of scientists and their computer codes or other tools of their trade. 

Question No. 2. Dr. Wegman states that paleoclimatologists do not interact with 

statisticians. Do you have any response to that statement? What steps, if any, is the 

paleoclimatology field taking to ensure that it is using appropriate statistical 

methodologies? 
765

Answer: 

 Unfortunately, Dr. Wegman made this claim without engaging in any effort to 

ascertain the extent to which climate scientists interact with statisticians. To the contrary, 

Dr. Wegman simply assumed --- without data, indeed, without any basis at all --- that 

climate scientists, and paleoclimatologists in particular, do not interact with statisticians. 

 Dr. Wegman’s accusation could not be further from the truth. The participation of 

statisticians in climate science has become so routine that there is an entire field of 

climate research known as “statistical climatology,” which involves the collaboration of 

large numbers of statisticians and climate scientists. There are even textbooks dedicated 

to the study of statistical climatology. In his testimony before the Committee, Dr. Hans 

Von Storch found it necessary to inform Dr. Wegman of this fact. And Dr. Von Storch 

should know; he and Dr. Francis Zwiers (a Ph.D. statistician specializing in climate 

applications) have written one widely used textbook on statistics and its applications to 

climate studies. Another statistician, Professor Dan Wilks of Cornell University, has 

written an additional textbook on statistics and its applications to the atmospheric 

sciences. 

 The extensive collaboration between climate scientists and statisticians is also 

reflected in the academic literature. Hundreds of papers have been published in the 

climate and paleoclimate literature involving the collaboration of statisticians and climate 

scientists. These are all publicly available and could have been identified by Dr. 

Wegman in a few hours of research. Two members of the NRC committee that reviewed 

paleoclimate reconstructions in its recent report (Dr. Douglas Nychka and Dr. Peter 

Bloomfield) are statisticians (both of their doctorates are in statistics) who have published 

in the climate literature and who have actively collaborated with climate scientists. 

Had Dr. Wegman bothered to make even the slightest inquiry, he would have found that 

there are in fact many statisticians (that is, individuals with doctorates in statistics) who 

have been and remain active members of the community of researchers in the areas of 

atmospheric science and climate research. Even a cursory review of the structure of our 

community reveals this readily. I have been informed that many of my statistical 

climatologist colleagues are deeply offended by Dr. Wegman’s unfounded 

pronouncements to this Committee, pronouncements which effectively deny their 

contribution to the advancement of science. 

 Moreover, the American Meteorological Society --- the leading professional 

organization of atmospheric scientists --- has a Committee on Probability and Statistics, 

and members of the committee are drawn from both atmospheric/ocean/climate scientists 

and statisticians. I was a member of that committee for a 3-year term (2003-2005) that 

recently ended. The committee’s website can be found here: 

http://www.isse.ucar.edu/ams/ams_ps.html, and the committee members’ biographies are 

available here: 

http://www.isse.ucar.edu/ams/ams_ps.html#members. The chair of the committee, Dr. 

Rick Katz is a statistician (with his doctorate in statistics from Penn State University) and 

senior scientist at NCAR. Other statisticians on the committee include Dr. Tilmann 

Gneiting (Department of Statistics, University of Washington), and Dr. William Briggs 

(Adjunct Assistant Professor of Statistical Science, Cornell University). These 

statisticians are active members of the climate research community. 

Equally important, one of the primary centers for climate research in the U.S., 

NCAR, has maintained a thriving Geophysical Statistics Project (“GSP”), which was 

founded more than a decade ago. This program has been funded by the National Science 

Foundation’s Division of Mathematical Sciences, which has recognized for some time the 

importance of encouraging statisticians to collaborate actively with atmospheric 

scientists/climate scientists. I participated as a graduate student in GSP’s inaugural 

workshop in 1994. Many leading statisticians (e.g., Dr. Grace Wahba, Dr. Arthur 

Dempster, and Dr. Noal Cressie) were participants. The GSP has since thrived, providing 
766

an important opportunity for collaboration between statisticians and climate researchers. 

More information can be found at the GSP webpage: http://www.image.ucar.edu/GSP/. 

 It bears noting that the project has now produced more than two dozen Ph.D. 

statisticians who have become active researchers in the atmospheric, oceanographic, and 

climate sciences. Its members and visitors have included dozens of statisticians who 

have worked collaboratively with atmospheric scientists and climate researchers. The 

leader of the project, Dr. Douglass Nychka, was one of the members of the 

aforementioned NRC panel. He was also a consultant in the recent paper by Wahl and 

Ammann that refutes the oft-cited criticisms of the Mann et al. work by McIntyre and 

McKitrick. 

Question No. 3. Dr. Wegman has hypothesized that the peer review process failed 

and allowed publication of your 1998 and 1999 studies without adequate vetting of 

the study. This was based in part on his social network analysis that showed you 

have connections with 42 other authors in paleoclimatology. Of the 42 co-authors 

identified by Dr. Wegman, how many of them were co-authors with you in or before 

1999? 

Answer: 

 Dr. Wegman’s accusations are so riddled with flaws that it’s hard to know where to 

begin in response. But let me first address the specious accusation by Wegman that the 

peer-review process somehow “failed” with respect to our ’98 and ’99 studies. It is 

bewildering that Dr. Wegman (who has no expertise in the area of atmospheric 

science/climate, and indeed was wholly unable to correctly answer some of the most 

basic questions about climate science during the hearings) would characterize the 

publication of our work as a “failure.” One would assume that an academic would avoid 

rendering judgments in fields in which he is demonstrably unknowledgeable. Certainly 

the scientific community has reached the precisely the opposite conclusion. Our 1998 

and 1999 studies are widely cited, and the conclusions stated in them have been 

repeatedly reaffirmed. Just one example of the scientific support for these works should 

suffice: The National Research Council panel in their recent Report characterized our 

study as “groundbreaking”, and the panel concluded that its key conclusions have held up 

over nearly a decade of exhaustive and independent follow-up research. That is a pretty 

good track record by any standard. Thus, judged by experts who understand climate 

studies, Wegman’s efforts to disparage our work as “failed” are nothing short of silly. 

 Let me next address Wegman’s equally specious and unsupported claim that 

scientists who work in a given field cannot objectively review the work of their 

colleagues and competitors in that field. By way of illustration, I have attached (as 

Attachment 1 to these Responses) the famous 1927 photograph of attendees of the Solvay 

Physics meeting in Brussels. It shows a group of 29 physicists engaged in a collegial, 

small conference. Virtually every attendee was a driving figure behind our understanding 

of modern physics. Appearing in the photograph are Einstein, Heisenberg, Bohr, Fermi, 

Dirac, de Broglie, Born, Pauli, Langmuir, Planck, Curie, Compton, Ehrenfest, Lengevin, 

and others of equal prominence. The members of this group all knew each other, worked 

with each other, collaborated on research with one another, visited each other, went 

mountain-climbing together, and so forth. Familiarity did not compromise their 

contributions to science. While I do not claim that the group I collaborate with is likely 

to duplicate the feats of the scientists who gathered in Brussels 80 years ago, the point 

remains --- scientific collaboration does not turn scientists into timid lapdogs unwilling to 

criticize the work of their colleagues. 

 Let me turn now to the specifics of the question. It is baffling how Dr. Wegman 

arrived at the number (42) he used to describe my co-authors. One would think that a 

statistician could do simple arithmetic. My curricular vitae (CV) is available on the 
767

internet, and it is clear that Wegman consulted it (but not me) in the preparation of his 

paper. Nonetheless, none of the numbers he uses add up. Part of the problem may stem 

from Wegman’s ill-advised effort to distinguish between authors engaged in 

“paleoclimatology” and “climatology,” since most climate researchers have worked, in 

some manner, on some aspect of paleoclimate. So the distinction he attempts to draw 

between “paleoclimatologists” and “climatologists” is illusory at best. This too 

underscores the hazards of an amateur seeking to draw conclusions in a field in which he 

has no expertise. 

 But to answer the question Wegman poses, let us consider the correct numbers (see 

Attachment 2 to these Reponses) which are based on all of my peer-reviewed journal 

publications as listed on my CV (and not including “gray literature” such as book 

chapters, encyclopedia pieces, reports, conference proceedings, letters to editors, opinion 

pieces). I published with 10 co-authors prior to 1993 based on my undergraduate 

research in solid state physics. These publications are unrelated to climate research, and 

are not included. 

 So let us consider just my climate-related papers (i.e., post 1993), as Wegman 

purports to do. In climate research, I had 14 co-authors through the year 1999. I had 

101 co-authors through the end of 2005. So Wegman’s calculations, based on 42 coauthors, are off-base by more than a factor of two. Wegman also appears to have made 

even more fundamental errors in his review of the science (a point I address below). 

 But I believe the question goes to how influential I was in the field, in a relative 

sense, at the time of publication of my ’98 and ’99 studies. After all, Wegman claims 

that there is, in essence, an almost sinister conspiracy of like-minded climate scientists 

who act as a cartel to control the published literature in climate studies. And his “proof” 

is the fact that I have published with many prominent scientists who, in Wegman’s view, 

would be unwilling to criticize my 1998 and 1999 work even if it were seriously flawed. 

But this theory does not wash. Apart from the fact that even my closest collaborators are 

perfectly willing to criticize my work when they think it is flawed, Wegman’s math just 

does not support his theory. As indicated above, the vast majority (86%) of my coauthorships occurred after my 1998/1999 studies. So Wegman’s effort to suggest that I 

was influential in the field at the time these studies were published, or in the aftermath of 

their publication, cannot be squared with the data, and is, in fact, nothing short of absurd. 

Question No. 4. Does the scientific community rely exclusively or primarily on the 

peer review process conducted before an article is published to test the robustness 

and validity of new scientific discoveries or theories? Or does the development of 

science depend on an iterative process that involves not only peer review before 

publication, but also review and competing research and analysis by other scientists 

after publication? 

 

Answer: 

 This question raises an important issue that was unfortunately not adequately aired 

at the hearing. Dr. Wegman and others have expressed the view that the scientific 

community somehow places exclusive reliance on the peer review process as the 

determinant of scientific truth. But the peer review process is hardly the only, let alone 

most important, way that the scientific community tests the accuracy and reliability of 

scientific papers. Indeed, Wegman’s contention reflects a fundamental lack of 

understanding of the basic principles that govern the scientific discipline. Science 

progresses through an open, self-correcting process whereby scientists place their ideas in 

the marketplace, typically by publishing articles in peer review journals. The peer review 

process ensures only that basic mistakes are not made, that the article acknowledges the 

existing literature on the subject, and that it contributes in some way to the exploration of 

important scientific issues. But peer review does not and cannot vouch for the accuracy 
768

of the paper. That is the function of the scientific process, by which other scientists test 

out and question the work of their peers. Some ideas stand the test of time; others do not. 

Copernicus was proven right over time; Ptolemy’s conception that the Earth forms the 

center of the universe was proven wrong. Much of Einstein’s work has stood up to 

reevaluation, but some of his theories have been proven to be incorrect as well. 

 It is relevant in this context to again emphasize that the key conclusion that my 

colleagues and I drew tentatively in our work in the late ‘90s --- that late 20th century 

Northern Hemisphere average warmth was likely unprecedented in at least the past 1000 

years --- has held up for more than a decade, after dozens of independent studies have 

reexamined that claim. So it has passed this important test of time. The peer-review 

process is simply a quality control process to make sure that claims, theories, and ideas 

that are self-evidently flawed from the beginning do not clutter the pages of the legitimate 

peer-reviewed scientific journals, that is, to ensure that published papers have potential

merit. Peer review is a simple first step at quality control. It does not, nor should it, be 

considered evidence that the conclusions of a particular published paper are accurate or 

not. No single paper should ever be used to establish the validity of a particular 

hypothesis or conclusion. The accuracy of claims, hypotheses, conclusions, indeed 

theories, can only be established by examining the collective body of peer-reviewed 

research to date on any particular topic, and the overall thrust of that body of research. 

Indeed, the importance of broad-based scientific assessments (such as those provided by 

the Intergovernmental Panel on Climate Change or “IPCC”) is to evaluate the entire body 

of peer-reviewed literature on a particular topic and to determine the consensus, if there is 

one, that emerges in that body of literature. 

Question No. 5. Should all scientific papers be withheld from publication until the 

results are independently replicated? 

 

Answer: 

 This question also raises an important issue that was not adequately aired at the 

hearing. Once again, Dr. Wegman and others suggested at the hearing that scientific 

papers be shelved for the time it takes for the results to be verified independently. This 

view is misguided, and, if followed, would seriously undermine the development of 

scientific knowledge. It takes considerable time to replicate a study. Meanwhile, 

important findings that ought to be disseminated widely to the scientific community 

would be unavailable to other scholars. Such a requirement would dangerously slow the 

progress of science. 

 As I explained above, in my view development of scientific knowledge can take 

place only through an open, self-correcting process whereby scientists put out ideas, other 

scientists test them, and those ideas which stand up to future tests survive while those that 

do not are ultimately rejected. It is important in this context that ideas with potential 

merit be placed in the scientific discourse in a timely manner, so that they can be 

followed up in a timely manner by the entire scientific community and not just a few 

researchers engaged in replication, and the scientific process can proceed at an 

appropriate pace. Were the suggested requirement to be followed where all papers 

required independent replication before publication, this would bog down the scientific 

process to a near standstill. 

In data-poor areas of science such as paleoclimatology, the added benefit of new data is 

much more valuable than the pure replication of a past study. “Replication” in a pure 

sense provides very poor value for money. A good example would be the now- famous 

GRIP and GISP2 ice cores from Greenland. These are two different Greenland ice cores 

that were drilled at two nearby but distinct locations by two different (one U.S. and one 

European) teams. Had the total available funding simply been used for both teams to 

drill cores at the same site, and thereby replicate each other’s work, only the technical 
769

accuracy of the coring would have been validated. Instead, the reproduction of a record 

that was nearby but separate gave both support to the main results, but also allowed the 

groups to discover a mix-up in dating prior to 100,000 years ago in one of the two cores. 

So drilling two different ice cores, rather than drilling from the same source twice, proved 

to be a far more valuable use of the available funding and resources. 

 The proponents of this idea also ignore the near-impossibility of its implementation. 

How would scientists be persuaded to replicate the unpublished work of others? What 

would their incentives be to conduct this work quickly, especially if it meant sacrificing 

the time researchers would prefer to spend on their own work? Would every study be 

subject to replication? Or only important studies? And who would decide which studies 

required replication prior to publication? Who would pay for these replications? Would 

the government pay for them? Is Congress prepared to double the size of research 

budgets for all of the major scientific funding agencies (e.g. NSF, NIH, NOAA, etc.)? 

And these practical problems are only the tip of the iceberg. 

 My essential plea here is that Congress should not fix that which is not broken. 

Since Copernicus’ time the scientific process has successfully weeded out the wheat from 

the chaff. It would be dangerous for Congress or any government body to tamper with 

that process. 

 There is another element of this question which raises a deeply troubling matter with 

regard to Dr. Wegman’s failure to subject his work to peer review, and Wegman’s 

apparent refusal to let other scientists try to replicate his work. Professor David Ritson, 

Emeritus Professor of Physics, Stanford University, has found error in the way that Dr. 

Wegman models the “persistence” of climate proxy data. Interestingly, this is the same 

error Steven McIntyre committed in his work, which was recently refuted in the paper by 

Wahl and Ammann, which was in turn vetted by Dr. Douglass Nychka, an eminent 

statistician. Dr. Ritson has determined that that the calculations that underlie the 

conclusions that Dr. Wegman advanced in his report are likely flawed. Although Dr. 

Ritson has been unable to reproduce, even qualitatively, the results claimed by Dr. 

Wegman, he has been able to isolate the likely source of Wegman’s errors. What is so 

troubling is that Dr. Wegman and his co-authors have ignored repeated collegial inquiries 

by Dr. Ritson and apparently are refusing to provide any basic details about the 

calculations for the report (see Attachments 3 and 4 to this Response). It would appear 

that Dr. Wegman has completely failed to live up to the very standards he has publicly 

demanded of others. 

 Moreover, the errors that Dr. Ritson has identified in Dr. Wegman’s calculations 

appear so basic that they would almost certainly have been detected in a standard peer 

review. In other words, had Dr. Wegman’s report been properly peer-reviewed in a 

rigorous process where peer-reviewers were selected anonymously, it likely would not 

have seen the light of day. Dr. Wegman has thus unwittingly provided us with a prime 

example of the importance of the peer review process as a basic first step in quality 

control. 
770

RESPONSE FOR THE RECORD OF DR. JOHN R. CHRISTY, PROFESSOR AND DIRECTOR, EARTH 

SYSTEM SCIENCE CENTER, NSSTC, UNIVERSITY OF ALABAMA IN HUNTSVILLE

28 August 2006 

Hon. Ed Whitfield 

Chairman 

Subcommittee on Oversight and Investigations 

Committee on Energy and Commerce 

2125 Rayburn House Office Building 

Washington DC 20515-6115 

Dear Rep. Whitfield, 

Thank you for the opportunity to appear before your Subcommittee to address issues of 

global climate change. I especially thank you for the opportunity to clarify some of the 

material that was entered into the official record which appeared to contradict my 

testimony. I assure you that what I presented was accurate as to my experiences and 

understanding of climate change in general and dataset construction in particular. 

I will be happy and available to answer any further questions regarding my appearance. 

Sincerely, 

John R. Christy 

Director, Earth System Science Center 

Alabama State Climatologist 

University of Alabama in Huntsville 
771

Questions from Rep. Whitfield for John R. Christy 

(1) During the hearing, Mr. Waxman introduced into the hearing record a letter 

from Frank J. Wentz regarding your sharing of code with Remote Sensing Systems 

9RSS). Please explain your interactions with RSS (and Mr. Wentz) and subsequent 

interactions with Dr. Mann, as mentioned in your testimony. 

(1) Answer 

In the Hearing before the Subcommittee on Oversight and Investigations of the 

House Committee on Energy and Commerce on 27 July 2006, I testified about our 

cooperation with Remote Sensing Systems (RSS) regarding sharing of satellite data and 

code. 

Mr. Waxman introduced into the record a letter from Mr. Frank Wentz of RSS 

which included an email from me to Mr. Wentz, over 4 years old, implying an apparent 

lack of cooperation. The problems here are (a) that this March 2002 email to Mr. Wentz 

from me was simply the first in a long series of emails in which we indeed cooperated, 

and (b) that this exchange related to a different dataset than the one I was speaking of in 

my testimony. The following discussion describes the way these two datasets were 

examined by RSS. 

Mid-Tropospheric (MT) Temperature Product 

Another RSS Scientist, Dr. Carl Mears (not Dr. Mann), began constructing an MT 

product from the raw microwave digital counts in early 2002, following much of our 

published methodology. There were some discrepancies between our two results. Mr. 

Wentz asked for the code with which we constructed our MT data so as to resolve these 

differences. As stated in my first email on the subject, shared by Mr. Waxman in Mr. 

Wentz’s letter, I declined to send the code for the reasons given. However, there were 

many further exchanges of information (in terms of the Hearing language: there were 

discussions about the “algorithms”) to the point that RSS understood the three main 

differences between our two datasets. Mr. Wentz’s description of “trial and error” in his 

letter in this process left out the important point that we were in constant communication 

on the details and subtleties of the dataset construction process. 

During this time, we discussed at great length matters concerning (1) the 

methodology of calculating the strength of the target-temperature effect, (2) the 

methodology of determining intersatellite biases and to a lesser extent (3) the adjustments 

for the satellites’ east-west drifting (diurnal effect.) 

At a conference in Asheville NC, (Oct. 2003) Dr. Mears presented a talk entitled 

“Understanding the difference between the UAH and RSS retrievals of satellite-based 

tropospheric temperature estimate” and stated he was satisfied as to having understood 

the main reasons for the differences between our two datasets. Indeed in this 

presentation, Dr. Mears used some of the adjustment files we had provided to them to 

help answer questions of how our adjustment process worked (i.e. diurnal drift files.) He 

also displayed our target factor calculations, again provided to RSS, along with a detailed 

description of their computation. It was clear we had provided information to understand 

the discrepancies. 

RSS was also able to publish these findings and results (Mears et al. 2003). I was a 

reviewer of that paper and recommended publication. In my view, this closed the episode 

on this dataset. 

Lower Tropospheric (LT) Temperature Product 

In 2005, Dr. Mears also led in the development of a different temperature product, 

LT, which UAH had been producing since 1992. He addressed the issues of hot target 
772

calibration coefficients and intersatellite biases to his satisfaction but was unable to 

replicate our diurnal effect. He asked for more information and we supplied the 

appropriate section of the code and intermediate adjustment files so he could test the code 

against the output. With these in hand he was able to discover the artifact in the algebra 

which created the error most visible in the tropics. 

That we supplied these items is inarguable as the paper published by Mears and 

Wentz (2005) in Science displays the UAH adjustment files. Additionally, even though 

we did not know the outcome of their study at the time, I granted permission to publish 

our files as shown by this following exchange between Dr. Mears and myself on 13 May 

2005 in which he responds to me for being open in this way. 

13 May 2005 8:41 p.m. 

Hi Carl: 

Anyway, something jogged my memory this morning that you had asked about 

using the UAH diurnal adjustments in a paper, and I didn't respond with a firm 

answer. Sorry. I think it would be fine to use and critique ... that's sort of what 

science is all about. 

[John Christy] 

13 May 2005 1:58 p.m. 

Hi John 

Thanks for permission -- I strongly approve of your view of science expressed 

[above]. I think that things that aren't nutty or poorly explained should be 

published in the open literature without too much fuss, so that they can then be 

commented on..... Of course, different people have different opinions about 

what constitutes nutty. 

You[r] global diurnal effect agree[s] pretty much with mine, but it's the 

*opposite* sign. The real difference is in the tropics. I suspect the same 

calculation for 20S to 20N will show a much larger effect. With the modelbased diurnal correction, the big disagreement with the surface in the tropics 

goes away. 

[Carl Mears Remote Sensing System] 

So, the apparent contradiction between my testimony and the letter from Mr. Wentz 

sprang from a misunderstanding of how two different datasets were being addressed. 

One (MT) was solved without sharing the specific code but for which we did supply 

ancillary data files and considerable information. The other (LT) needed parts of the 

code to resolve the discrepancy. In the Hearing, Mr. Waxman dealt with the former 

while I dealt with the latter. In both cases, however, UAH did cooperate with RSS. 

Mears, C.A., M.C. Schabel, and F.J. Wentz, 2003: A reanalysis of the MSU channel 2 

tropospheric temperature record. J. Climate, 16, 3650-3664. 

Mears, C.A. and F.J. Wentz, 2005: The effect of diurnal correction on satellite-derived 

lower tropospheric temperature. Science, 309, 1538-1551. 
773

(2) As you were a member of the National Research Council panel that recently 

issued the report on millennial temperature reconstructions: 

(a) Where in the report did the panel describe “plausible” as suggesting 

roughly a 2/3rds probability of being correct. 

(b) In the report, did the panel attach probability estimates to the term 

“plausible”? 

(c) Why did the panel choose to use the term “plausible,” as opposed for 

example to terms such as “likely”, to describe confidence in millennial 

temperature reconstructions? 

(2a) Answer 

The report did not intend for “plausible” to be equated with “2/3rds” probability of 

being correct. My view ,as a panel member, is that “plausible” was chosen to indicate a 

lack of quantifiability in describing confidence in pre-1600 temperatures. 

(2b) Answer 

“Plausible” was chosen precisely because it implied that probability estimates could 

not be assigned to pre-1600 temperature estimates due to (a) the limited amount of proxy 

information available and (b) the unknown confidence with which these proxy records 

may determine temperature. The current proxies are mostly consistent with the notion 

that pre-1600 temperatures were cooler than late 20th century temperatures, but the 

evidence is still too meager and uncertain. 

(2c) Answer 

As a member of the IPCC 2001 Lead Author team I outlined in my testimony why 

the word “likely” was chosen in that document. “Likely” in the IPCC 2001 terminology 

had an estimated likelihood defined as being at least 2/3rds probable. The NRC panel 

chose “plausible” for reasons given in (2b) above. My view of the NRC report is that our 

IPCC statement was inadequate in that the IPCC should have separated the last 

millennium into two periods with higher than “likely” confidence for post-1600 and 

lower than “likely” confidence for pre-1600 estimates. 

(3) When considering the panel’s findings that it is “plausible” that recent decades 

were the warmest in a millennium, is it correct to interpret that to mean the panel’s 

consensus view was that plausible means roughly 2/3rds probability of being 

correct, as was suggested in the news reports following the press conference 

releasing the report? 

(3) Answer 

I was disturbed when reading the press reports that implied the panel had endorsed 

with “likely” confidence statements about the pre-1600 temperatures. The panel did not 

conclude that there was a 2/3rds probability that late 20th century warmth was greater 

than at anytime prior to 1600. As noted above, there are indications that such is the case, 

but the data do not allow statements of quantifiable confidence to be made at this point. 

(4) In your testimony, you mention your recent study relating to California regional 

temperature trends and human influences on those trends (Christy et al. 2006a). 

Please describe the purpose and conclusions of that study. 
774

(4) Answer 

As a native of Fresno and an avid weather observer since being a teenager there, I 

had an abiding interest in determining the extent of temperature changes in the Valley. 

This eventually led to a study funded by the National Science Foundation. The first part 

of the study was a data gathering effort in which every available long-term dataset for the 

Valley and nearby Sierras was acquired, many by manual digitization from paper records. 

The second part was the development of a means to merge all of these data into a 

regional time series of temperature for daytime and nighttime temperatures separately, for 

each season separately and for the Valley and Sierras separately. 

We discovered that Valley nighttime temperatures were rising rapidly while daytime 

temperatures were generally falling slightly. In the Sierras however, there were no real 

significant trends, with perhaps a suggestion of nighttime cooling in summer and fall. 

This result suggests that the significant changes in the land surface of the Valley 

(irrigation and perhaps urbanization) are causing the changes in the Valley. The fact 

there were no long-term changes in the Sierras for this period suggests that the enhanced 

greenhouse effect has not been a significant factor in Central California in terms of 

temperature changes. (For regions this small, one must always consider the natural 

variations of climate as also being an issue with which to deal, but such variations should 

have affected both Valley and Sierra in the same way.) 

(5) Please explain why the measurement of average global (or average hemispheric) 

temperature change does or does not represent an adequate metric for 

understanding or predicting the risks of potential climate change impacts. 

(5) Answer 

Thermometers near the surface will respond to all of the forcing processes that act 

upon them. Thus, surface temperature over land will show responses to changes such as 

urbanization and other land-use changes in addition to that of atmospheric forcing from 

aerosols or greenhouse gases. As a result, it is difficult to extract out the impacts of one 

particular forcing on surface temperature with high confidence. 

Daily temperature is commonly reported as two values, the maximum and 

minimum, from which the daily average is calculated. Maximum temperature is more 

relevant for climate change as it occurs when the surface and upper atmosphere are more 

closely connected through vertical mixing and thus will give a better idea of what the 

general climate system as a whole is doing. Minimum temperature is more closely 

related to a shallow layer near the ground and is thus impacted more by urbanization, 

aerosol pollution and other land-use changes. Thus, daily average temperature is partially 

dependent on processes that impact minima. 

Theoretically, the temperature of the ocean surface is a better quantity to measure in 

terms of observing a variable that has a more direct relationship to a forcing such as 

greenhouse gases. However, there are large areas of the ocean that have never been 

systematically observed over long-periods, and the manner by which ocean temperatures 

have been taken and the associated biases contain a certain level of uncertainty, 

especially in the earliest years. 

Surface temperature is one metric for assessing climate variations and change, but is 

less informative than others. Indeed the ability of model simulations to depict surface 

temperature distributions is quite primitive at this stage. Focusing on the global average

surface temperature also circumvents the fact that the spatial distribution of those changes 

is more important than the overall average in terms of risk and impact. For example, our 

work in California, the SE USA and preliminary work in East Africa indicate models are 
775

not able to replicate what the observations since 1900 have shown, though for the global 

average they are not in great error. Additionally, the lowest layer (or boundary layer) of 

the atmosphere in which these surface thermometers are positioned, is an extremely 

complicated part of the climate system which is not well-represented in climate models. 

Average surface temperature, while valuable in local terms to humans who live on the 

surface, is a rather limited and complicated variable, compounding its lack of utility in 

providing a high level of understanding about greenhouse-gas induced climate change. 

A much more fundamental measurement needed to assess how various forcing 

mechanisms are affecting the planet is the heat content, which is essentially the number 

of joules of energy in the system. So, by counting the number of joules of energy in the 

deep atmosphere, ocean (mainly upper ocean), and other components such as ice caps, 

one has access to a better metric for understanding how much extra energy is (or is not) 

being trapped in the climate system. Knowing the number of joules, however, is still a 

step removed from knowing whether particular components of the Earth (and human) 

system might be at “risk” for a significant impact. 

It is a very subjective task to address the idea of “risk” of potential impacts of a 

changing climate (either natural or human-induced) from surface temperature 

considerations, and as important, the possible impact of specific policies. The various 

processes that affect surface temperature render it a less-than-optimal gauge of humaninduced climate change impacts, even if concentrating on the better measure - daily 

maximum temperature. Thus, it is even more difficult to assign an observed change in 

surface temperature to a particular cause. 

Questions from Rep. Supak for John R. Christy 

(1) In your written testimony, you stated that the poor of the world are more 

vulnerable to the impacts of poverty, water and air pollution, and political 

strife (sic) than to whatever the climate does. You also made a plea that 

the poor of the world not be denied the use of energy. A recent article in 

the Washington Post recorded the tremendous cost of subsistence farmers 

and urban dwellers in Peru because of the melting of the glaciers that has 

caused a water crisis. The loss of glacial ice in the Himalayas will affect 

300 million people relying on snowmelt for the water supply. (See 

attached, “On the roof of Peru, Omens in the Ice; Retreat of Once-Mighty 

Glacier signals Water Crisis, Mirroring Worldwide Trend,” July 29, 2006, 

A1.) 

(a) Is it your position that nothing should be done in the developed 

world to control its fossil fuel energy use while we wait for 

development to reach these poor people who are directly 

suffering today from the effects of climate change? 

(b) What do you propose to protect the poor people of the world 

today from the effects of climate change, particularly as it relates 

to their water supply and ability to raise crops to feed their 

families?

This is an important issue to me and I will strive to provide a policy-relevant answer. 

Thank you for addressing an issue that has considerable import to millions. 

The questions above are introduced with a Washington Post news article describing 

the apparent plight of Peruvians who depend on annual snow/glacial melting for a portion 

of their water needs. These types of articles generally present dramatic assertions and 

tend to highlight whatever is alarmist and attention-grabbing. After all, the ability of the 
776

media to survive is dependent on how many people’s attention may be grabbed. 

Assertions are not science. Science is numbers (as Lord Kelvin said.) 

Tropical glaciers have been advancing and retreating for thousands of years, and are 

not exceptionally good indicators of temperature. (Note for example: Scientists Unravel 

Mystery of Growing Glaciers, 24 Aug 2006, Guardian Unlimited, describing the growth 

of glaciers in the western Himalaya, Karakoram and Hindu Kush mountains.) In Fig. 6.1 

of the NRC Surface Temperature Reconstruction Report (2006 of which I was a coauthor), ice cores of three glaciers are shown for South America and three for the Tibetan 

Plateau. Two of the 6 show an increase in the proxy temperature since 1000 A.D. while 

the other 4 show level or declining trends. In particular, the glacier identified in the Post

article (Quelccaya) shows a long decline (cooling) to about 1800 with a rise to about 

1950 and fairly level since then which doesn’t match human-induced climate change 

theories well at all. Dr. Lonnie Thompson, who studies this glacier more than anyone, 

indicated to me that he believed this glacier was about 1,500 years old. Thus, it appears 

that these glaciers advance and retreat on many time scales and should not be depended 

upon for the long term. This is what the numbers suggest. 

A society which depends on the annual melting of “glacial” ice is therefore 

dependent on an erratic system. The following letter to the editor addresses the problems 

of the Peruvian water situation, noting that ineffective water management rather than 

global warming is the problem. 

Peru Shows Why Water Privatization Is Needed 

Washington Post 

Sunday, August 6, 2006; B06 

Doug Struck reported on the water crisis in Lima, Peru, and on the role that 

accelerated glacier melting has played in recent years ["On the Roof of Peru, 

Omens in the Ice," front page, July 29]. But more than a billion people 

throughout the developing world lack access to clean water, and that is largely 

due to the dismal performance of the public sector, which is in charge of 97 

percent of formal water distribution in poor countries. Water shortages are even 

common in Cherrapunji, India, which has been described as the wettest place on 

Earth. 

In Lima, a quarter of the city's 8 million people don't have piped water. The 

article quotes an engineer at Peru's public monopoly who suggests that if the 

utility did connect those 2 million people, there would not be enough water to 

serve them. The article does not mention that some 40 percent of the water 

piped through the public utility is lost to leakages and otherwise unaccounted 

for. 

Peru's public water utility has failed to serve a huge percentage of the 

population for decades. Privatization would increase access to water, reduce 

death and diseases, and introduce accountability and rational pricing, as 

countless cases of successful water privatization around the world have shown. 

The first to benefit would be Lima's poor, who currently pay exorbitant blackmarket prices for water. 

IAN VÁSQUEZ 

Director 

Project on Global Economic Liberty 
777

Cato Institute 

Washington 

The main problem in poor agricultural societies like Peru is that the country's 

institutions and regulations encourage wasteful water usage in rural areas that particularly 

harm the poor. Agricultural productivity is mainly undermined by major factors (lack of 

property rights, closed economies, civil wars, state marketing boards, erratic 

macroeconomic policy, low growth, bad infrastructure, etc.) that have nothing 

whatsoever to do with global warming. In areas like Peru where glacier melting seems to 

have reduced water supply, it would be far cheaper to pay for a range of solutions (a 

system of dams and irrigation, relocation of some vulnerable citizens, etc.) than it would 

to implement alternatives that would reduce growth in both rich and poor countries and in 

the end have no impact on the problem. So the better approach is to encourage locallyfocused solutions at a far smaller cost than top-down energy suppression measures which 

in reality will not impact the climate. 

In summary, alarmist articles, such as was as attached with these questions, are not 

designed to give hard scientific information from which policy can be made. The real 

issues in this arena often boil down to how public water management entities have failed 

to store, allocate and distribute water effectively, efficiently and sustainably. 

(1a) Answer 

As indicated in my testimony, it is my view that people should be given greater 

access to energy produced by the most efficient and clean means possible because energy 

provides longer and better lives. At present, much of the poor’s energy is produced from 

biomass burning (wood, dung) which destroys habitat and fouls the air with toxic smoke. 

In that context, energy from fossil fuels can be an environmental and humanitarian step 

forward. Though expensive and intermittent, other sources, such as solar or wind, could 

help fill part of the gap. However, cost, reliability and base-load power requirements are 

three factors that must be considered and which tend to work against solar and wind. 

I do not subscribe to the notion that climate change (about which we can do 

anything about) is causing these people serious problems today. Tropical glaciers are 

known to have advanced and retreated many times in the past. People who are dependent 

on a particular status quo of a dynamical system like mountain glaciers are operating in a 

belief-system that the actual climate cannot guarantee. The present retreat of several of 

the glaciers in this part of the tropics leads one to hope these people can adapt to such 

variability. (But note above the growth of glaciers in South Asia.) Their water still falls 

as rain and snow, and capturing that water for dry spells is a prudent plan to pursue. The 

issue of water policy goes far beyond Peru and the impacts of climate change (see 

below). 

(1b) Answer 

Let me first say that the future distribution and quantity of rainfall is unknown. 

Rainfall patterns have been notoriously variable over the centuries as evidenced by paleoclimate research during the period when no human-influence on climate was possible. 

Additionally, rainfall in general is more important than temperature for sustaining life. 

Climate models are unable to confidently predict where the rain may increase, 

decrease or stay the same. Further, efforts to “control” climate change are misguided as 

we have no way to confidently determine how a particular policy for controlling 

greenhouse gases will impact precipitation. 

Water policy is a vast and complex issue with climate variability being only one 

component. The political aspects of water availability are significant and the growth of 
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water-dependent systems (human and agricultural) in desert areas is going to be a 

challenge to sustain whatever the climate does (see introductory comments to these 

answers). In the U.S. for example, we know that creating the availability and 

performance of an acre-foot of fresh water in California (where over 80% goes to 

irrigation) costs about 15 times that of creating the same acre-foot in Alabama. Where 

then should the country invest its funds for the most benefit, both financially and 

environmentally? 

The policy-relevant issues for a political body are to determine (1) where and how 

much water there is, (2) who owns the water and therefore who controls its use, (3) what 

uses are sustainable environmentally, financially and politically, (4) what infrastructure 

may be built to use the available water efficiently, confidently and sustainably, and (5) 

what incentives are available to pay for (4). 

I suspect water will become more and more commoditized in the future, so that 

some investment will come from the commercial sector to store and distribute water. 

How governments, especially poor governments, take advantage of such investments to 

provide clean water for human consumption (and a great leap forward in health care) will 

be done on a country-by-country basis, but I cannot predict how effective that process 

will be. U.S. policymakers could facilitate the reduction of water crises by helping 

governments answer these 5 questions. 

(2) Your published work on satellite-derived lower tropospheric temperature 

data was used for several years as evidence that there is no global 

warming, since it appeared to show that the temperatures in the tropics 

were actually cooling. In 2005, Dr. Carl Mears and Dr. Frank Wentz of 

Remote Sensing Systems in Santa Rosa, California, published an article in 

Science magazine showing that, because of orbital drift and decay that was 

not controlled for in your study, the temperature measurements were 

gradually taken later and later in the day when temperatures were cooling. 

The article also found a mathematical error in your work. When 

corrected, the data pointed to an increase in tropical temperatures, not a 

decrease. 

Is you original work still being used as evidence that there is no global warming? 

Have you corrected this work? 

There are a number of issues intermingled in these comments and questions that 

need clarification. Beginning in June 1998 and for every month since then, the 

University of Alabama in Huntsville (UAH) global temperature measurements reported 

positive global trends for all versions of the lower tropospheric (LT) temperature dataset. 

The tropical trends were not different from a zero trend when Mears and Wentz began 

looking at the methodology of our version 5.1 (v5.1). As noted in my testimony they 

discovered an artifact of our adjustments for satellite drift which created a cooling error 

in the tropics for LT. (We produce other temperature products which used the same 

methodology to account for this drift but which were not affected by this artifact.) 

A fair bit of confusion arose when Mears and Wentz published the discovery of this 

error in August 2005 and in the same publication introduced a new LT dataset of their 

own. The implication of this publication was that the error they found was the difference 

between our old dataset and their new dataset which was significant, about 0.10 

°C/decade. In other words, the impression given in the article was that their new dataset 

represented a corrected version of our old dataset. Unfortunately, this was not the case. 

The actual impact of the error in UAH’s v5.1 was not addressed in their paper. As Roy 

Spencer and I published in Science magazine later in 2005, the effect of that error was 

small, +0.035 °C/decade (at that time from +0.090 to +0.125 °C/decade), being within 
779

our originally published error margin assigned to v5.1. In the tropics, the effect was to 

increase the trend from +0.00 to +0.05 °C/decade. 

We corrected the error in May 2005 and with the publication of Mears and Wentz 

put the data on a public website in August 2005, though it was provided to several 

scientists before that date. This new version, v5.2, has been publicly available since that 

time. So there are two LT datasets with somewhat differing trends, UAH’s and RSS’s. 

Of interest to the committee is the fact I will have two papers to be published shortly 

which indicate UAH v5.2 is highly consistent with independent temperature 

measurements of the LT layer. These papers show that it is very likely that the tropical 

atmosphere is warming at a rate equal to or less than that of the surface, a characteristic 

no climate model that we have examined replicates. Thus, there is evidence that the 

theoretical ideas of how the large-scale atmosphere should be responding to the enhanced 

greenhouse effect, as embodied in climate models, still have shortcomings. 

As to the first question, we provide only the latest version of our data to the public. 

And, since 1998 any version of our lower tropospheric dataset would have shown a 

positive global trend. Thus, if someone is using UAH data to claim no global warming, I 

would speculate they are likely using pre-1998 data or are somehow altering the data to 

make that conclusion. I don’t know of any current claims to that effect, and UAH has 

been forthright in reporting positive trends (and the likelihood that at least part of that 

positive trend is due to enhanced greenhouse gases) these past 8 years. 

In answering the second question, the discussion above describes the events that led 

to the correction of the drift error and UAH’s corrected data have been publicly available 

since August 2005. However, one should be aware that datasets are always subject to 

revision, and we look forward to v6.0 of our current dataset, though there will be little 

change in the outcome relative to v5.2. 
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RESPONSE FOR THE RECORD OF DR. RALPH J. CICERONE, PRESIDENT, NATIONAL ACADEMY 

OF SCIENCES
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RESPONSE FOR THE RECORD OF MR. STEPHEN MCINTYRE, TORONTO, ONTARIO, CANADA
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RESPONSE FOR THE RECORD OF DR. EDWARD J. WEGMAN, DIRECTOR, CENTER FOR 

COMPUTATIONAL STATISTICS
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