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CLIMATE HISTORY AND THE SCIENCE UNDERLYING FATE, TRANSPORT, AND HEALTH EFFECTS OF MERCURY EMISSIONS

HEARING

BEFORE THE

COMMITTEE ON

ENVIRONMENT AND PUBLIC WORKS

UNITED STATES SENATE

ONE HUNDRED EIGHTH CONGRESS

FIRST SESSION

JULY 29, 2003

Printed for the use of the Committee on Environment and Public Works

(
COMMITTEE ON ENVIRONMENT AND PUBLIC WORKS

ONE HUNDRED EIGHTH CONGRESS

FIRST SESSION

JAMES M. INHOFE, Oklahoma, Chairman

JOHN W. WARNER, Virginia

CHRISTOPHER S. BOND, Missouri

GEORGE V. VOINOVICH, Ohio

MICHAEL D. CRAPO, Idaho

LINCOLN CHAFEE, Rhode Island

JOHN CORNYN, Texas

LISA MURKOWSKI, Alaska

CRAIG THOMAS, Wyoming

WAYNE ALLARD, Colorado

JAMES M. JEFFORDS, Vermont

MAX BAUCUS, Montana

HARRY REID, Nevada

BOB GRAHAM, Florida

JOSEPH I. LIEBERMAN, Connecticut

BARBARA BOXER, California

RON WYDEN, Oregon

THOMAS R. CARPER, Delaware

HILLARY RODHAM CLINTON, New York

ANDREW WHEELER, Majority Staff Director

KEN CONNOLLY, Minority Staff Director

(II)
(III)

CONTENTS

Page

JULY 29, 2003

OPENING STATEMENTS

Allard, Hon. Wayne, U.S. Senator from the State of Colorado, prepared statement ...................................................................................................................... 11

Cornyn, Hon. Jon, U.S. Senator from the State of Texas, prepared statement . 58

Inhofe, Hon. James M., U.S. Senator from the State of Oklahoma .................... 1

Jeffords, Hon. James M., U.S. Senator from the State of Vermont, prepared

statement .............................................................................................................. 7

Voinovich, Hon. George V., U.S. Senator from the State of Ohio ........................ 3

WITNESSES

Legates, David R., director, Center for Climatic Research, University of Delaware ....................................................................................................................... 12

Prepared statement .......................................................................................... 209

Levin, Leonard, program manager, Electric Power Research Institute .............. 40

Prepared statement .......................................................................................... 211

Mann, Michael E., assistant professor, University of Virginia, Department

of Environmental Sciences .................................................................................. 9

Prepared statement .......................................................................................... 173

Responses to additional questions from:

Senator Inhofe ........................................................................................... 178

Senator Jeffords ......................................................................................... 194

Myers, Gary, professor of Neurology and Pediatrics, Department of Neurology,

University of Rochester Medical Center ............................................................ 44

Prepared statement .......................................................................................... 299

Rice, Deborah C., toxicologist, Bureau of Remediation and Waste Management, Maine Department of Environmental Protection ................................... 42

Prepared statement .......................................................................................... 283

Responses to additional questions from Senator Jeffords ............................. 284

Soon, Willie, astrophysicist, Harvard-Smithsonian Center for Astrophysics ..... 6

Prepared statement .......................................................................................... 58

Responses to additional questions from Senator Jeffords ............................. 155

ADDITIONAL MATERIAL

Articles:

Climate Research, Vol. 23:89–110, 2003, Proxy Climatic and Environmental Changes of the Past 1000 years ...................................................... 127–148

Energy & Environment Vol. 14, Nos. 2 and 3, 2003, Reconstructing

Climatic and Environmental Changes of the Past 1000 Years: A Reappraisal....................................................................................................... 60–126

Geophysical Research Letters, Vol. 31, Estimation and Representation

of Long-term (>40 year) Trends of Northern-Hemisphere-gridded Surface Temperature: A Note of Caution ...................................................... 149–154

Original Contributions, Effects of Prenatal and Postnatal Methylmercury

Exposure From Fish Consumption on Neurodevelopment..................... 302–308

Personal Health, Tip the Scale in Favor of Fish: The Healthful Benefits

Await .............................................................................................................. 321

Risk Analysis, Vol. 23, No. 1, 2003, Methods and Rationale for Derivation

of a Reference Dose for Methylmercury by the U.S. EPA ......................... 290–298
Page

IV

—Continued

The Atlanta Journal-Constitution, June 6, 2003, Clear Skies Mercury

Curb Put in Doubt ........................................................................................ 317

The Lancet, Prenatal Methylmercury Exposure from Ocean Fish Consumption in the Seychelles Child Development Study........................... 309–316

The New York Times, July 29, 2003, Does Mercury Matter? Experts

Debate the Big Fish Question ...................................................................... 319

The Philadelphia Inquirer, March 7, 2003, Mercury Rising ......................... 318

Chart, National Mean Mercury Concentration in Tissues of Selected Fish

Species (all sample types) .................................................................................... 289

Letter, to Senator Inhofe, from John Christy ........................................................ 323

Report, EPRI, May 2003, A Framework for Assessing the Cost-Effectiveness

of Electric Power Sector Mercury Control Policies ........................................ 217–282
(1)

CLIMATE HISTORY AND THE SCIENCE UNDERLYING FATE, TRANSPORT, AND HEALTH

EFFECTS OF MERCURY EMISSIONS

TUESDAY, JULY 29, 2003

U.S. SENATE,

COMMITTEE ON ENVIRONMENT AND PUBLIC WORKS,

Washington, DC.

The committee met, pursuant to notice, at 9 o’clock a.m. in room

406, Senate Dirksen Building, Hon. James M. Inhofe (chairman of

the committee) presiding.

Present: Senators Inhofe, Allard, Carper, Clinton, Cornyn, Jeffords, Thomas and Voinovich.

OPENING STATEMENT OF HON. JAMES M. INHOFE,

U.S. SENATOR FROM THE STATE OF OKLAHOMA

Senator INHOFE. The meeting will come to order.

We have a policy that we announced when I became chairman

of the committee that we will start on time, whether anyone is here

or not here, members, witnesses or others. So I appreciate all of

you being punctual in spite of the fact that the Senators are not.

One of my primary objectives as chairman of the committee is to

improve the way in which science is used. I think that when I became chairman of this committee, I announced three very outrageous things that we were going to do in this committee that

have not been done before. No. 1, we are going to try to base our

decisions, things that we do, on sound science. No. 2, we are going

to be looking at the costs of some of these regulations, some of

these policies that we have, and determine what they are going to

be. And No. 3, we are going to try to reprogram the attitudes of

the bureaucracy so that they are here not to rule, but to serve.

Good public policy decisions depend on what is real or probable,

not simply on what serves our respective political agendas. When

science is debated openly and honestly, public policy can be debated

on firmer grounds. Scientific inquiry cannot be censored. Scientific

debate must be open. It must be unbiased. It must stress facts

rather than political agendas.

Before us today, we have two researchers who have published

what I consider to be a credible, well-documented, and scientifically

defensible study examining the history of climate change. Furthermore, these are top fields of inquiry in the Nation’s energy environment debate and really the entire world’s energy environment debate. We can all agree that the implications of this science are

global, not only in terms of the environmental impacts, but also en-
2

ergy impacts, global trade impacts, and quite frankly, no less than

global governance impacts.

We could also all agree that as a result of the import and impact

of these issues, it is absolutely crucial that we get this science

right. False or incomplete or misconstrued data are simply not an

acceptable basis for policymaking decisions in which the Congress

of the United States is involved. Such data would violate the Data

Quality Act, which we passed on a bipartisan basis here in the

Senate and which we have bipartisanly embraced. If we need more

data to satisfy our standards, then so be it.

This Administration is prepared to do so in an aggressive strategy that the climate change strategic plan outlines. The 1000-year

climate study that the Harvard-Smithsonian Center for Astrophysics has compiled is a powerful new work of science. It has received much attention, and rightfully so. I would add at this time,

it did not receive much attention from some of the liberal media

who just did not want to believe that any of the facts that were

disclosed were accurate.

I think the same can be said in terms of work that has recently

received attention of the hockey stick study. In many important

ways, the Harvard-Smithsonian Center’s work shifts the paradigm

away from the previous hockey stick study. The powerful new findings of this most comprehensive study shiver the timbers of the

adrift Chicken Little crowd.

I look forward to determining whose data is most comprehensive,

uses the most proxies, maintains the regional effects, avoids losing

specificity through averaging statistics, considers more studies, and

most accurately reflects the realities of the Little Ice Age, reflects

the realities of the Medieval Warming Period, and more.

Mercury presents a different set of issues. That would be our second panel. It is well-established that high levels of exposure to

methyl-mercury before birth can lead to neuro-development problems. But what about mercury consumed through fish, the most

common form of prenatal exposure? Mercury makes its way into

fish through various ways, but primarily though deposition from

air emissions, with 80 percent of emissions deposited either regionally or globally, not locally. Global mercury emissions are about

5,000 tons a year. About half of those are man-made emissions.

In the United States, a little more than 100 tons are emitted

from non-power plant sources. Industry is making great strides in

reducing these emissions. I would like to submit for the record this

EPA document available on their Web site which indicates that

when rules now on the books are fully implemented at non-power

plant, nationwide emissions will be cut by nearly 50 percent. Power

plants emit about 50 tons of mercury annually, about 1 percent of

the worldwide emissions.

In setting policy, key questions need to be answered, such as how

would controls change this deposition; what portion of mercury exposure can not be controlled; and what are the health impacts of

prenatal exposure. We will hear testimony today that indicates any

changes to mercury exposure in fish would be minimal under even

the most stringent proposal to regulate mercury. Today, we will

also hear testimony that the most recent and comprehensive study
3

to date found no evidence that prenatal mercury exposure from

ocean fish presents a neurological risk.

So we have diverse opinions that will be discussed today, and

that is the reason for this hearing, to wade through that so that

those on the panel that will be making policy decisions will understand. I think it is no secret that we are not scientists up here, so

we look at things logically.

With that, I would recognize one of my colleagues here that I

have a great deal of respect for. Senator Voinovich and I started

out together as we were mayors of cities almost 25 years ago. I consider him to be one of the real experts in the area of air. In fact,

I can remember calling him in as an expert when he was Governor

of Ohio and we were holding these hearings and I was chairman

at that time of the Clean Air Subcommittee. I would recognize Senator Voinovich for any comments he would like to make or opening

statements.

OPENING STATEMENT OF HON. GEORGE V. VOINOVICH,

U.S. SENATOR FROM THE STATE OF OHIO

Senator VOINOVICH. Thank you, Mr. Chairman.

I want to congratulate you for the very comprehensive floor

speech that you gave yesterday on the issue of climate change.

Senator INHOFE. I guess I should apologize. It was 12,000 words

and I know you were anxious to get some floor time, so I appreciate

your patience.

Senator VOINOVICH. Your words were much more scientifically

based than mine.

[Laughter.]

Senator VOINOVICH. The two issues that we are going to explore

at the hearing today, the science of mercury and the science of climate change, are both important and timely. I commend you for

holding this hearing.

I think I do not have to remind you that we have had hearings

on climate change now during the last 4 or 5 years. I think I had

a couple when I was chairman of even the Transportation Infrastructure Committee. Senator Lieberman had hearings over in

Governmental Affairs when he was chairman of the committee a

year or so ago. So it is not a subject that is brand new to this committee.

I have stated time and time again here in the committee and on

the floor that we must recognize that energy policy and environmental policy are two sides of the same coin, and the Senate has

responsibility to harmonize these policies. We have an obligation

here in the committee to ensure that legislation that we consider

will protect our environment. We also have an obligation to ensure

that any legislation we consider takes into account its potential impact on our economy and we have a moral obligation to ensure that

we consider a bill’s particular impact on the poor and the elderly

who must survive on fixed incomes.

When the Senate takes up consideration of climate change and

multi-pollutant legislation, we must keep that moral obligation in

mind. We must ensure that we do not pass legislation that will significantly drive up the cost of electricity and home heating for

those who can least afford them.
4

Several members of this committee have introduced pieces of legislation this year to reduce power plant emissions, including mercury, and address the issue of carbon emissions and climate change

by capping carbon. Examples include Jeffords-Lieberman four-P

bill, the Carper four-P bill, and the McCain-Lieberman climate

change bill, which I understand will likely be offered as an amendment to the energy bill, just this week we are going to be considering it.

These bills will establish a nationwide cap on carbon emissions

and their passage would force the utility sector, that is now using

coal to generate over half of our Nation’s electricity. To rely solely

on natural gas for generation, we will have fuel switching—capping

carbon equals fuel switching equals no-coal—to rely on natural gas

regeneration despite the fact we have over a 250-year supply of domestic coal and are currently in the grips of a natural gas crisis

in this country.

This crisis is a result of environmental policies that have driven

up the use of natural gas in electricity generation significantly,

while domestic supplies of natural gas have fallen, partly because

we cannot do the exploration that we need to do for natural gas.

The result is predictable: tightening supplies of natural gas,

higher natural gas prices, and higher electricity prices. Home heating prices are up dramatically, forcing folks on low and fixed incomes to choose between heating their homes and paying for other

necessities such as food or medicine. The language that has been

offered by Senators Jeffords, McCain, Lieberman and Carper if enacted will force our utilities to fuel switch to natural gas; will significantly raise energy prices; and will cause thousands of jobs to

be lost, particularly in manufacturing States like my State of Ohio,

which is already under duress in terms of manufacturing.

During the debate last year on the Jeffords-Lieberman four-P

bill, I put together a white paper that discussed the impact that

the bill would have if it were enacted. The numbers are staggering:

an overall reduction in GDP of $150 billion by 2020, the loss of over

900,000 jobs by 2020, and a decline in national household earnings

of $550 annually.

The cost of climate-change language such as the McCainLieberman bill could come without any benefits to our air quality

or public health. Not even the most ardent supporter, and I hope

this comes up, of carbon regulation will claim that there are demonstrable health benefits from carbon regulation. Yet the Energy

Information Administration estimates that the passage of the

McCain-Lieberman bill, if enacted, will raise petroleum product

prices by 31 percent, raise natural gas prices by 79 percent, raise

electricity prices by 46 percent, and reduce GDP by up to $93 billion by 2025.

Carbon caps and unrealistic mercury caps means fuel switching,

again. The fuel switching means the end of manufacturing in my

State, enormous burdens on the least of our brethren. It means

moving jobs and production overseas, where there are less stringent environmental programs. And will actually, if you really think

about it, increase global levels of pollution.

The question we face in this committee is whether we should do

something reasonable to improve our understanding of the issues
5

surrounding carbon emissions and climate change, and attempt to

reduce atmospheric concentration of carbon and mercury emissions

without harming our economy, or rush into short-sighted policy

that will cap carbon and mercury at unreasonable levels, shut

down our economy, cut thousands of jobs, and move manufacturing

overseas.

In a recent column, former Secretary of Energy James Schlesinger commented that:

‘‘In climate change, we have only a limited grasp of the overall forces at work.

Uncertainties have continued to abound and must be reduced. In any approach

to policy formation, this is very important, under conditions of such uncertainty

should be taken only on an exploratory or a sequential basis. A premature commitment to a fixed policy could only proceed with fear and trembling.’’

I would like to have that column inserted in the record, Mr.

Chairman.

Senator INHOFE. Without objection, so ordered.

Senator VOINOVICH. As I mentioned previously once or twice, I

am working with Chairman Inhofe and the Administration on moving Clear Skies forward, which I intend to mark up in my subcommittee this fall. I am currently working with business and environmental groups to find a bipartisan compromise on dealing with

carbon and global warming, with an emphasis on sound science,

carbon sequestration, development of clean coal technologies, and

a responsible approach that focuses more on consensus rather than

politics.

We need more Senators to focus on moving forward in a responsible way and move away from harshly ideological positions that

advance nothing other than the agenda of some environmental

groups that have made carbon cap a political litmus test.

I thank the chairman for holding this important hearing and I

look forward to hearing the testimony from our witnesses.

Senator INHOFE. That is an excellent opening statement, Senator

Voinovich. I go back to one of your first sentences when you talked

about the number of hearings we have had. We have to keep in

mind that each new hearing has new data. For example, the 1,000-

year Harvard-Smithsonian was not even out until March of this

year. So there are new things that are coming along and I see a

new trend-line which I discussed on the House of the Senate yesterday. So this will be a very valuable hearing.

Senator Cornyn, would you have any opening statement to

make?

Senator CORNYN. I would like to reserve any statement until

later, Mr. Chairman.

Senator INHOFE. Yes, that is fine. First, I would like to ask the

first panel to come up. Dr. Legates, Dr. Willie Soon and Dr. Mann,

would you three come up? First of all, we are honored to have who

I consider three very excellent and professional scientific witnesses

here today. Normally, we restrict the opening statements to 5 minutes, but it would be fine if you want to go about 7 minutes because I know you have come a long way and what we are dealing

with here is probably one of the most significant things facing

America, facing our economy, facing our environment today.

So I would introduce all three. Dr. David Legates is the director

of the Center for Climatic Research at the University of Delaware.
6

Dr. Willie Soon is the astrophysicist at Harvard-Smithsonian Center for Astrophysics, and Dr. Michael Mann is assistant professor

at the University of Virginia Department of Environmental

Sciences. I will first ask Dr. Willie Soon to give his opening statement.

STATEMENT OF WILLIE SOON, ASTROPHYSICIST, HARVARDSMITHSONIAN CENTER FOR ASTROPHYSICS

Dr. SOON. Mr. Chairman, distinguished Senators, my fellow panelists, Dr. Mann and Dr. Legates, and members of the audience,

my name is Willie Soon. About a month or two ago, I became a

very proud and grateful U.S. citizen. I just cannot believe where I

am sitting today.

I am an astrophysicist with the Harvard-Smithsonian Center for

Astrophysics in Cambridge, Massachusetts. My training is in atmospherics and space physics. My research interests for the past

10 years include changes in the sun and their possible impact on

climate.

I am here today to testify that the climate of the 20th century

is neither unusual nor the most extreme. Around 1,000 years ago,

the temperature over many parts of the world was warm. A widespread cooling then set in for several centuries, followed by a recovery to 20th century warming.

My colleague and I collected the information on climate by proxy.

We studied environmental indicators of local climate change going

back some 1,000 years from many locations around the world.

Based on work of approximately 1,000 researchers and hundreds of

peer-reviewed papers, we conclude the following three points about

climate history of the last 1,000 years.

On a location-by-location basis, point No. 1, there was warming

from 800 to 1300 A.D., all about 1,000 years ago, over many parts

of the world. This period is called the Medieval Warm Period. Following the warming of 1,000 years ago was a general cooling from

about 1300 to 1900 A.D. This period is called the Little Ice Age.

Point No. 2, there is no convincing evidence from local proxy to

suggest that the 20th century had higher temperatures or more extreme climate than the warm period 1,000 years ago.

Point No. 3, local and regional, rather than global average

changes are the most relevant and practical measure of climate

changes and its impact. Much of the climate proxy results using

our work are new. Most papers were published in the scientific literature in the recent 5 to 10 years. There are two points to note

about our methods. First, we keep the local or regional information

contained in each climate proxy. This is important for studying geographical patterns of climate, which does not change everywhere at

the same time.

Second, climate is more than just temperature, so we keep the

climate information like rainfall, expansion or contraction of forests, all advances or retreats of glaciers, et cetera. Our approach

makes use of the richness of information in climate proxies, which

map out local environmental and climate properties, rather than

just temperature alone.

The entirety of climate proxies over the last 1,000 years shows

that over many areas of the world, there has been and continues
7

to be large local climatic changes. Those changes provide important

changes for the computer simulations of climate. The full models

which explore the Earth region by region can be tested against the

natural patterns of change over the last 1,000 years that are detailed by the climate proxies.

Having computer simulation, we produced past patterns of climate which has been influenced predominantly by natural factors

and is key to making an accurate forecast that includes all potential human-made warming and cooling effects.

In summary, based on expert conclusions from climate proxies in

several hundred peer-reviewed papers by over 1,000 researchers

from around the world, we find the following. No. 1, from one location to another, large natural swings in climate have occurred over

the last 1,000 years. Those patterns have not always been synchronous.

No. 2, there was widespread warmth about 1,000 years ago, followed by widespread cooling ending by the beginning of the 20th

century.

No. 3, the local and regional climate proxies cannot confirm that

the 20th century is the warmest or most extreme over much of the

world, compared especially to the Medieval Warm Period approximately 1,000 years ago.

This is all for my oral remarks and I thank you for the opportunity to be here.

Senator INHOFE. Dr. Soon, we appreciate that excellent opening

statement. You did not even take all of your time. That is very unusual.

At this time, Dr. Mann if you don’t mind, I would like to interrupt your testimony. We have been joined by the Ranking Minority

Member, Senator Jeffords. Senator Jeffords, do you have an opening statement you would like to make at this time?

Senator JEFFORDS. I would ask unanimous consent that it be

made as part of the record and would prefer listening to the witnesses.

[The prepared statement of Senator Jeffords follows:]

STATEMENT OF HON. JAMES JEFFORDS, U.S. SENATOR FROM THE STATE OF VERMONT

We’re here today to discuss two very important topics—climate change and mercury pollution. As most of you know, I am the author of ambitious legislation—the

Clean Power Act of 2003—which addresses these environmental problems, as well

as ozone, acid rain, and human health damage from fine particulate matter.

Unfortunately, we aren’t here today to talk about moving forward to find innovative solutions to these real world problems. Instead, today’s hearing will largely be

a mirror or the reverse of the robust and growing consensus in the mainstream scientific community on climate and mercury pollution.

The disappointing result will be more delay. Delay on the part of Congress, and

even worse, the ongoing backsliding on the part of the Administration, means that

we fail to act responsibly as a society to protect future generations. That means increasingly greater risks of global warming and mercury poisoning.

There is no doubt that the scientific process must inform policymakers as new information comes in. Unfortunately, there is no new information to be found here

today that would dissuade us from acting quickly and responsibly to reduce greenhouse gas and mercury emissions. In today’s discussion of a literature survey of climate research, the skeptics are trotting out an argument that is several years old

and already discarded by their peers.

It is abundantly clear that now is the time to act.
8

• The National Academy of Sciences has said, ‘‘Despite the uncertainties, there

is general agreement that the observed warming is real and particularly strong

within the past 20 years.’’

• NOAA currently says that,

‘‘The climatic record over the last thousand years clearly shows that global

temperatures increased significantly in the 20th Century, and that this warming was likely to have been unprecedented in the last 1200 years.’’

• EPA’s website says that, ‘‘There is new and stronger evidence that most of the

warming over the last 50 years is attributable to human activities.’’

One would have to be madder than a March hare to fail to see the need to act.

Yet, the Administration’s new research plan falls squarely into hare territory—denying the reality staring them in the face.

I want to show you the latest odds on warming. MIT says that there is a one in

five chance that the temperature of the earth will warm by approximately 4 or 5

degrees over the course of this century, assuming there is no action to reduce emissions.

As my dear departed friend, Senator John Chafee, said in 1989:

‘‘It is clear that we are facing a serious threat. The scientists are telling us

that if we continue to stroll along as if everything is fine, we will transform

Earth into a planet that will not be able to support life as we now know it.’’

While mercury contamination does not have the same dramatic effect on earth’s

systems, it is still a dangerous global and local pollutant because it is bio-accumulative and toxic to human health.

Long ago, Congress decided that toxic air emissions should be reduced and took

very aggressive steps in 1990 to make that happen, especially if they fall into the

Great Lakes and other great waters like Lake Champlain. Unfortunately, the Agency has fallen significantly behind in complying with the Clean Air Act’s schedule.

A settlement agreement mandates controlling toxic air pollutants from utilities by

2008.

In 1998, related to the controversy around EPA’s late reports to Congress on utility air toxics, Congress directed the National Academy of Sciences (NAS) to recommend an appropriate reference dose for mercury exposure. In 2000, the NAS reported that EPA’s reference dose was scientifically sound and adequate to protect

most Americans. That NAS review considered all health effects studies, including

the Seychelles study that we’ll discuss today.

We know that mercury is a potent toxic. It affects the human brain, spinal cord,

kidneys, liver and the heart. It affects the ability to feel, see, taste and move. We

know that mercury can affect fetal development, preventing the brain and nervous

system from developing normally. Long term exposure to mercury can result in stupor, coma and personality changes.

‘‘Mad as a Hatter’’ is the phrase that was used in the 1800’s to describe the employees of the felt hat industry whose constant exposure to mercury changed their

behavior. Fortunately, Americans exposure from commercial and recreational fish

consumption is substantially less than that, though dozens of health warnings are

posted nationwide.

But, it’s crazy for anyone to suggest that we should not reduce mercury emissions

significantly, since we know its health effects and we have the technologies to control it.

We should have a hearing on how to export those control technologies and Congress should urge the Administration to negotiate binding global reductions in mercury, as the Senate did last year in the Energy bill for greenhouse gas emissions.

At a minimum, we should pass four-pollutant legislation now that gets reductions

faster and deeper than required by the current Clean Air Act. I’m sad to say that

there have been no negotiations on that front since I initiated some in early 2002.

And the Administration has done nothing to reduce these emissions with its abundant authority in the Act.

We can’t afford to leave these problems to future generations to solve. We can’t

let our children and grandchildren wake up to find that our delays have cost them

dearly in terms of health and the global and local environment. It’s time to act responsibly.

Finally, I ask that material from the journal EOS, the NOAA website, the Atlanta

Journal Constitution, the National Center for Atmospheric Research, and the American Geophysical Union be included in the hearing record.
9

Senator JEFFORDS. I might point out, we have got to do something about this traffic out there.

[Laughter.]

Senator INHOFE. Well, the name of our subcommittee is Transportation and Infrastructure, so maybe we can do something about

the traffic out there.

Senator JEFFORDS. I hope so.

Senator INHOFE. Dr. Mann, you are recognized.

STATEMENT OF MICHAEL E. MANN, ASSISTANT PROFESSOR,

UNIVERSITY OF VIRGINIA, DEPARTMENT OF ENVIRONMENTAL SCIENCES

Dr. MANN. Senators, my name is Michael Mann. I am a professor

in the Department of Environmental Sciences at the University of

Virginia. My research involves the study of climate variability and

its causes. I was a lead author of the IPCC Third Scientific Assessment report. I am current organizing committee chair for the National Academy of Sciences’ Frontiers of Science, and have served

as a committee member or adviser for other National Academy of

Sciences’ panels.

I have served as editor for the Journal of Climate of the American Meteorological Society for 3 years and I am a member of the

advisory panel for the NOAA Climate Change Data and Detection

Program. I am a member of numerous other international and U.S.

scientific working groups, panels and steering committees. I have

coauthored more than 60 peer-reviewed publications on diverse topics within the fields of climatology and paleoclimatology.

Honors I have received include selection in 2002 as one of the 50

leading visionaries in science and technology by Scientific American magazine, and the outstanding scientific publication award of

NOAA for 2000.

In my testimony here today, I will explain, No. 1, how mainstream climate researchers have come to the conclusion that late

20th century warmth is unprecedented in a very long-term context

and that this warmth is likely related to the activity of human

beings; and No. 2, why a pair of recent articles challenging these

conclusions by astronomer Willie Soon and his coauthors are fundamentally unsound.

It is the consensus of the climate research community that the

anomalous warmth of the late 20th century cannot be explained by

natural factors, but instead indicates significant anthropogenic,

that is human influences. This conclusion is embraced by the position statement on climate change and greenhouse gases of the

American Geophysical Union, by the 2001 report of the IPCC, the

Intergovernmental Panel on Climate Change, and by a National

Academy of Sciences’ report that was solicited by the Bush Administration in 2001.

More than a dozen independent research groups have now reconstructed the average temperature of the northern hemisphere in

past centuries, both by employing natural archives of past climate

information or proxy indicators such as tree rings, corals, ice cores,

lake sediments and historical documents, and through the use of

climate model simulations. If I can have the first exhibit here, as

shown in this exhibit, the various proxy reconstructions agree with
10

each other, as well as with the model simulations, all of which are

shown, within the estimated uncertainties. That is the gray-shaded

region.

The proxy reconstructions, taking into account these uncertainties, indicate that the warming of the northern hemisphere during

the late 20th century, that is the northern hemisphere, not the

globe, as I have sometimes heard my study incorrectly referred to,

the northern hemisphere during the late 20th century, that is the

end of the red curve, is unprecedented over at least the past millennium and it now appears based on peer-reviewed research, probably the past two millennia.

The model simulations demonstrate that it is not possible to explain the anomalous late-20th century warmth without the contribution from anthropogenic influences. These are the consensus

conclusions of the legitimate community of climate and paleoclimate researchers investigating such issues.

Astronomers Soon and Baliunas have attempted to challenge the

scientific consensus based on two recent papers, henceforth collectively referred to as SB, that completely misrepresent the past

work of other legitimate climate researchers and are deeply flawed

for the following reasons. No. 1, SB make the fundamental error

of citing evidence of either wet or dry conditions as being in support of an exceptional Medieval Warm Period. Such an ill-defined

criterion could be used to define any period of climate as either

warm or cold. It is pure nonsense.

Experienced paleoclimate researchers know that they must first

establish the existence of a temperature signal in a proxy record

before using it to try to reconstruct past temperature patterns. If

I can have exhibit two, this exhibit shows a map of the locations

of a set of records over the globe that have been rigorously analyzed by my colleagues and I for their reliability as long-term temperature indicators. I will refer back to that graphic shortly.

No. 2, it is essential to distinguish between regional temperature

changes and truly hemispheric or global changes. Average global or

hemispheric temperature variations tend to be far smaller in their

magnitude than those for particular regions. This is due to a tendency for the cancellation of simultaneous warm and cold conditions

in different regions, something that anybody who follows the

weather is familiar with, in fact.

As shown by exhibit three, if I can have that up here as well

now, thank you, this exhibit plots the estimated temperature for

various locations shown in the previously displayed map. As you

can see, the specific periods of relative cold and warm, blue and

red, differ greatly from region to region. Climatologists, of course,

know this. What makes the late 20th century unique is the simultaneous warmth indicated by nearly all the long-term records. It is

this simultaneous warmth that leads to the anomalous late-20th

century warmth evident for northern hemisphere average temperatures.

The approach taken by SB does not take into account whether

warming or cooling in different regions is actually coincident, despite what they might try to tell you here today.

No. 3, as it is only the past few decades during which northern

hemisphere temperatures have exceeded the bounds of natural var-
11

iability, any analysis such as SB that compares past temperatures

only to early or mid-20th century conditions; you repeatedly hear

Dr. Soon refer to the 20th century; climatologists do not consider

that a meaningful baseline because there has been a dramatic

warming during the 20th century and the early 20th century and

the late 20th century are almost as different as the late 20th century and any other period during the past 1,000 years at least. So

a study that refers only to early or mid-20th century conditions or

generic 20th century conditions and does not specifically address

the late 20th century, cannot address the issue of whether or not

late-20th century warmth is anomalous in a long-term context.

To summarize, late-20th century warming is unprecedented in

modern climate history at hemispheric scales. A flawed recent

claim to the contrary by scientists lacking expertise in paleoclimatology is not taken seriously by the scientific community.

The anomalous recent warmth is almost certainly associated

with human activity and this is the robust consensus view of the

legitimate climate research community.

Thank you.

Senator INHOFE. Thank you, Dr. Mann.

Dr. Legates.

First, I would ask Senator Allard, did you want to make an opening statement?

Senator ALLARD. Mr. Chairman, I do have an opening statement

and in deference to the panel and you I would just like to have it

put in the record. If you would do that, then I would be happy.

Senator INHOFE. Without objection.

[The prepared statement of Senator Allard follows:]

STATEMENT OF HON. WAYNE ALLARD, U.S. SENATOR FROM THE STATE OF COLORADO

Mr. Chairman, I want to thank you for holding this important hearing today.

As a veterinarian, I have some scientific training in my background. I strongly

believe that we should use scientific principals as a guidepost when formulating any

regulation. This scientific guidepost approach is particularly important when looking

at regulations with the implications and magnitude of regulations on climate change

and mercury control.

Climate change has been an ongoing discussion for many years. However, during

the 1970’s the concerns were exactly opposite of what they are now. Then we were

told that there was a threat of massive global cooling. Headlines screamed that we

were in danger of entering another ice age. Now we are told that massive warming

trends are going to cause overheating across the globe. We need answers, not rhetoric.

All of the witnesses here today have a great deal of experience. All of the witnesses here have spent many years analyzing data related to the areas of their expertise. But, I am concerned that, at times, data may be reviewed selectively and

in isolation. I am also concerned that emphasis may fall on a limited number of

studies. In science we have all learned that the only way to solidly prove a theory

is by conducting tests, studies or experiments that repeatedly arrive at the same

result. We cannot simply ignore the studies that do not have the outcome we are

looking for. This applies whether we are looking at climate change, mercury or any

other issue.

I want to spend most of my time and attention today on potential mercury regulations. While today’s hearing is intended to focus on science, I would also like to

touch on the impact that potential regulations will have on the economy of my state

and the west. As many of you know, western coal differs from other types of coal

in several ways. The higher chlorine content in western coal makes it more difficult

to remove mercury when burning it. And, while western coal does contain mercury,

when it is burned it gives off mercury in the elemental form. It is my understanding

that this is not the type of mercury that deposits in the ecosystem to potentially

be absorbed by the environment.
12

The economies of Colorado, and the entire west, will be impacted by harsh regulations placed on their coal. Economies undoubtedly will be damaged by the decrease

in use of coal mined in the West. In addition, while jobs are being lost due to the

subsequent inability to fully utilize western coal supplies, if power can no longer be

generated by using coal mined in the west, other less efficient coal types will have

to be transported across long distances. This additional expenditure will add to the

price of electricity generation, driving up electricity costs and further damaging an

economy that will already be struggling.

This is why it is so important to me that we be cautious when dealing with situations such as these and why we should place strong emphasis on the use of sound

science. Our regulations must be thoughtful reflections of what we know—they

should not be reflexive or reactive attempts to legislate a cure before we know what

the disease is.

Again, Mr. Chairman, thank you for holding this hearing. I look forward to hearing the witness testimony and discussions to come.

Senator INHOFE. That being the case, let’s dispense with any further opening statements.

Dr. Legates, thank you very much for being here. You are recognized.

STATEMENT OF DAVID R. LEGATES, DIRECTOR, CENTER FOR

CLIMATIC RESEARCH, UNIVERSITY OF DELAWARE

Dr. LEGATES. Thank you. Mr. Chairman, Distinguished Senators,

Doctors Mann and Soon, and members of the audience, I would like

to thank the committee for inviting my commentary on this important topic of climate history and its implications. My research interests have focused on hydroclimatology. That is the study of

water in the atmosphere and on the land, and as well as on the

application of statistical methodology in climatological research.

I am familiar with the testimony presented here by Dr. Soon. My

contributions to Dr. Soon’s research stem from my grappling with

the striking disagreement between the longstanding historical

record and the time series recently presented by Dr. Mann and his

colleagues. It also stems from my own experiences in compiling and

merging global estimates of air temperature and precipitation from

a variety of disparate sources.

My Ph.D. dissertation resulted in the compilation of high-resolution climatologies of global air temperature and precipitation. From

that experience, I have become acutely aware of the issues associated with merging data from a variety of sources and containing

various biases and uncertainties. By its very nature, climatological

data exhibit a number of spatial and temporal biases that must be

taken into account. Instrumental records exist only for the last century or so, and thus proxy records can only be used to glean information about the climate for earlier time periods. But it must be

noted that proxy records are not observations and strong caveats

must be considered when they are used. It, too, must be noted that

observational data are not without bias either.

Much research has described both the written and oral histories

of the climate, as well as the proxy climate records. It is recognized

that such records are not without their biases. For example, trees

respond not to just air temperature fluctuations, but to the entire

hydrologic cycle, including water supply, precipitation, and demand, which is only in part driven by air temperature.

Nevertheless, such accounts indicate that the climate of the last

millennium has been characterized by considerable variability and

that extended periods of cold and warmth existed. It has been gen-
13

erally agreed that during the early periods of the last millennium,

air temperatures were warmer and that temperatures became cooler toward the middle of the millennium. This gave rise to the terms

the Medieval Warm Period and the Little Ice Age, respectively.

However, as these periods were not always consistently warm or

cold, nor were the extremes geographically commensurate in time,

such terms must be used with care.

In a change from its earlier reports, however, the Third Assessment Report of the Intergovernmental Panel on Climate Change,

and now the U.S. National Assessment of Climate Change, both indicate that hemispheric and global air temperatures followed a

curve developed by Dr. Mann and his colleagues in 1999. This

curve exhibits two notable features, and I will point back to Dr.

Mann’s exhibit one that he showed a moment ago. First is a relatively flat and somewhat decreasing trend in air temperature that

extends from 1000 A.D. to about 1900 A.D. This feature is an

outlier that is in contravention to thousands of authors in the peerreviewed literature.

This is followed by an abrupt rise in the air temperature during

the 1900’s that culminates in 1998 with the highest temperature

on the graph. Virtually no uncertainty is assigned to the instrumental record of the last century. This conclusion reached by the

IPCC and the National Assessment is that the 1990’s was the

warmest decade, with 1998 being the warmest year of the last millennium.

Despite the large uncertainty, the surprising lack of significant

temperature variations in the record gives the impression that climate remained relatively unchanged throughout most of the last

millennium, at least until human influences began to cause an abrupt increase in temperatures during the last century. Such characterization is a scientific outlier. Interestingly, Mann et al replace

the proxy data for the 1900’s by the instrumental record and

present it with no uncertainty characterization. This, too, yields the

false impression that the instrumental record is consistent with the

proxy data and that it is error-free. It is neither.

The instrumental record contains numerous uncertainties, resulting from measurement errors, a lack of coverage over the world’s

oceans, and underrepresentation of mountainous and polar regions,

as well as undeveloped nations and the presence of urbanization effects resulting from the growth of cities. As I stated before, the

proxy records only in part reflect temperature. Therefore, a simultaneous presentation of the proxy and instrumental record is the

scientific equivalent to calling apples and oranges the same fruit.

Even if a modest uncertainty of plus or minus one-tenth of a degree Celsius were imposed on the instrumental record, the claim of

the 1990’s being the warmest decade would immediately become

questionable, as the uncertainty window would overlap with the

uncertainty associated with earlier time periods. Note, too, that if

the satellite temperature record, where little warming has been observed over the last 20 years, had been inserted instead of the instrumental record, it would be impossible to argue that the 1990’s

was the warmest decade. Such a cavalier treatment of scientific

data can create scientific outliers, such as the Mann et al curve.
14

So we are left to question why the Mann et all curve seems to

be at variance with the previous historical characterization of climatic variability. Investigating more than several hundred studies

that have developed proxy records, we came to the conclusion that

nearly all of these records show considerable fluctuations in air

temperature over the last millennium. Please note that we did not

reanalyze the proxy data. The original analysis from the various

experts was left intact, as it formed a voluminous refereed scientific literature. Most records show the coldest period is commensurate with at least a portion of what is termed the Little Ice Age,

and the warmest conditions at concomitant with at least a portion

of what is termed the Medieval Warm Period.

Our conclusion is entirely consistent with conclusions reached by

Drs. Bradley and Jones and not all locations on the globe experience cold or warm conditions. Moreover, we chose not to append

the instrumental record, but to compare apples with apples and determine if the proxy records themselves indeed confirm the claim

of the 1990’s being the warmest decade of the last millennium.

That claim is not borne out by the individual proxy records.

However, the IPCC report in the chapter with Dr. Mann as the

lead author and his colleagues as contributing authors, also concludes that the research ‘‘support the idea that the 15th to 19th

centuries were the coldest of the millennium over the northern

hemisphere overall.’’ Moreover, the IPCC report also concludes that

the Mann and Jones research shows temperatures from the 11th

to 14th centuries to be ‘‘warmer than those from the 15th to 19th

centuries.’’ This again is entirely consistent with our findings and

in contravention of their own error assessment.

Where we differ with Dr. Mann and his colleagues is in the construction of the hemisphere average time series and their assertion

that the 1990’s was the warmest decade of the last millennium.

Reasons why the Mann et al curve fails to retain the fidelity of the

individual proxy records are detailed statistical issues into which

I will not delve. But a real difference of opinion focuses solely on

the Mann et al curve, and how it is an outlier compared to the balance of evidence on millennial climate change. In a very real sense,

this is a fundamental issue that scientists must address before the

Mann et al curve can be taken as fact.

In closing, let me state that climate is simply more than annually averaged global air temperature. Too much focus, I believe, has

been placed on defining air temperature time series and such emphasis obscures the true issue in understanding climate change

and variability. If we are truly to understand climate and its impacts and driving forces, we must push beyond the tendency to distill climate to a single annual number. Proxy records which provide

our only possible link to the past are incomplete at best. But when

these voluminous records are carefully and individually examined,

one reaches the inescapable conclusion that climate variability has

been a natural occurrence and especially so over the last millennium.

Given the uncertainties and biases associated with the proxy and

instrumental records——

Senator INHOFE. Dr. Legates, we are going to have to cut it off.

You have exceeded your time and I am sure you will have an op-
15

portunity to finish your thoughts during the question and answer

period.

Dr. LEGATES. Thank you for the privilege.

Senator INHOFE. We are going to, if it is all right, use 5 minutes

and maybe try to get a few rounds here. Is that acceptable? These

will be 5 minute rounds for questioning. I will start.

First of all, Senator Thomas joined us. Thank you for coming,

Senator Thomas.

I will address my first question to Dr. Legates. In my speech on

the Senate floor yesterday, I noted your comments regarding—can

you find that chart of those comments?—the comments regarding

Dr. Mann’s work as shown on the chart. I have a small copy of this.

No, that is not it. It is this chart right here. OK.

First of all, this is a comparison. As I mentioned in my opening

statement, we sit up here as non-scientists so we try to look at

these things and see what is logical, how we should weigh and

compare diverse opinions. Now, the first thing I noticed was that

Dr. Mann, yours I believe was in the area of the timeframe of

1999——

Dr. MANN. Excuse me. That is incorrect.

Senator INHOFE [continuing]. And Dr. Soon, you are 2003. So I

think that the timing would mean something because I know that

this is not a static target. This is a moving target.

May I first ask Dr. Legates, do you stand by the statements that

are made on this chart up here, on the contrasting methods that

were used?

Dr. LEGATES. I have not had a chance to actually look at the

chart before now.

Senator INHOFE. Is this the one that he had here? OK, let’s put

that up. All right, then, this statement here,

‘‘Although Mann’s work is now widely used as proof of anthropogenic global

warming. We have become concerned that such analysis is in direct contradiction to most of the research and written histories available. My paper shows

this contradiction and argues that the results of Mann are out of step with the

preponderance of the evidence.’’

I am not Tim Russert, but do you stand by these statements?

Dr. LEGATES. I do stand by them, sir.

Senator INHOFE. All right. I note that you are an expert in statistical techniques. In my speech on the Senate floor yesterday, I

noted that even assuming all of the science used by the political

left, come the end of 50 years hence, the Kyoto Protocol would have

no measurable affect on temperature. Do you agree with that?

Dr. LEGATES. Yes, generally.

Senator INHOFE. And if the Kyoto Protocol forces harsher mandates, does it follow that the weaker legislative proposals that are

out there right now before us in the Senate would have likewise

no measurable effect?

Dr. LEGATES. That is likely true.

Senator INHOFE. All right. Let’s see. Dr. Mann, since you have

characterized your colleagues there in several different ways as

nonsense, illegitimate, and inexperienced, let me ask you if you

would use the same characterization of another person that I

quoted on the floor yesterday. I would like to call your attention

to the recent op/ed in the Washington Post by Dr. James Schles-
16

inger, who was Energy Secretary under President Carter. In it, he

wrote, ‘‘There is an idea among the public that the science is settled. That remains far from the truth.’’ He has also acknowledged

the Medieval Warming Period and the Little Ice Age. Do you question the scientific integrity of Dr. Schlesinger?

Dr. MANN. I do not think I have questioned scientific integrity.

I have questioned scientific expertise in the case of Drs. Willie Soon

and David Legates with regard to issues of paleoclimate. As far as

Schlesinger is concerned, I am not familiar with any peer-reviewed

work that he has submitted to the scientific literature, so I would

not be able to evaluate his comments in a similar way. If I could

clarify one——

Senator INHOFE. OK. Well, you can’t because there isn’t time. I

am going to stay within my timeframe and I want to get to questions so others will have plenty of opportunity to respond to questions I am sure.

Dr. Soon, how many studies did you examine in total and how

many were appropriate for the criteria you established?

Dr. SOON. Senator, the number is roughly in the order of, if you

speak in terms of the peer-reviewed literature, I would say several

hundred. And the number of people involved in these paleoclimatic

research would be at least 1,000. Of course, I have to emphasize

I am not a paleoclimate scientist, but all of us are ruled by one

simple goal, to understand the nature of how climate works. The

basis to get to the goal is to figure out the exact expressions of the

physical laws.

The short answer is there is a huge number of literature that we

consulted that feed the criteria. This is why we wrote it as a scientific paper.

Senator INHOFE. I was trying to get to the 240 proxies that were

used and the number used.

Dr. SOON. Yes, we listed about 240 proxy studies in our papers.

Senator INHOFE. Last, I would say, do you have more data in

your study than Dr. Mann did in his 1999 work? And is your data

newer?

Dr. SOON. Yes. I would emphasize that most of the proxy records

come from the most recent 5 years.

Senator INHOFE. Thank you, Dr. Soon.

Senator Jeffords.

Senator JEFFORDS. Dr. Mann, would you care to respond?

Dr. MANN. Yes, first of all I wanted to clarify a misstatement

earlier on the part of Senator Inhofe. The results that I showed in

my first graphic which demonstrate that it is a clear consensus of

the climate research community that a number of different estimates, not just ours, but at least 12 different estimates of the history of the northern hemisphere average temperature for the past

1,000 years give essentially the same result, within the uncertainties. We published a paper just a month ago demonstrating that

that is a robust result of a large number of mainstream researchers

in the climate research community.

Phil Jones and I also have a paper in press in the Journal of

Geophysical Research letters, which demonstrates those results further. So in fact, the latest word and the word of the mainstream
17

climate research community is the one that I have given you earlier.

Now, as far as the issue of data, how much data was used, there

are a number of misstatements that have been made about our

study. One of them is with regard to how much data we used. We

used literally hundreds of proxy records. We often represented

those proxy records, as statistical climatologists often do, in what

we call a state space. We represented them in terms of a smaller

number of variables to capture the leading patterns of variability

in the data. But we used hundreds of proxy indicators, more in fact

than Dr. Soon referred to. In fact, we actually analyzed climate

proxy records. Dr. Soon did not.

Senator JEFFORDS. Dr. Soon, in a 2001 article in Capitalism magazine, you said that because of the pattern of frequent and rapid

changes in climate throughout the holocene period, we should not

view the warming of the last 100 years as a unique event or as an

indication of manmade emissions’ effect on the climate.

But according to NOAA’s Web site ‘‘upon close examination of

these warm periods,’’ including all the ones that you cited in your

past and most recent article,

‘‘It became apparent that these periods are not similar to the 20th century

warming for two specific reasons. One, the periods of hypothesized past warming do not appear to be global in extent or, two, the period of warmth can be

explained by known natural climate forcing conditions that are uniquely different than those of the past 100 years.’’

Why didn’t either of your articles make an impact on the state

of the science or NOAA’s position?

Dr. SOON. Thank you for your question, Senator. As you may be

aware, my paper just got published this year, January 2003 and

April 2003, so it is all fairly recent. I have just written up this

paper very recently, so I do not know what impact it will have on

any general community, but I do know all my works are done consulting works from all major paleoclimatologists in the field, including Dr. Mann and his esteemed colleagues.

As to the comments about the Capitalism magazine, I am not

aware of that particular magazine. I do not know whether I submitted anything to this journal or this magazine. I do stand by the

statement that it is important to look at the local and regional

change before one takes global averages because climate tends to

vary in very large swings in different parts of the world. That really is the essence of climate change and one ought to be really looking very carefully at the local and regional change first, and also

one should not look strictly at only the temperature parameter, as

Dr. Mann has claimed to have done. That I think is very important

to take into account.

Senator JEFFORDS. Dr. Mann, could you comment?

Dr. MANN. Yes. Both of those statements are completely incorrect. If Dr. Soon had actually read any of the papers that we have

published over the past 5 years or so, he would be aware of the fact

that we use statistical techniques to reconstruct global patterns of

surface temperature. We average those spatial patterns to estimate

a northern hemisphere mean temperature, just as scientists today

seek to estimate the northern hemisphere average temperature

from a global network of thermometer measurements. We use pre-
18

cisely the same approach based on proxy reconstructions of spatial

patterns of surface temperature.

So what Dr. Soon has said is completely inaccurate. The first line

on that contrasting methods table up there is also completely inaccurate.

In terms of variables other than temperature, my colleagues and

I have published several papers reconstructing continental drought

over North America and reconstructed sea-level pressure patterns.

We have looked at just about every variable that climatologists are

interested in from the point of view of paleoclimate indicators. I

think Dr. Soon needs to review my work more carefully.

Senator INHOFE. Thank you, Senator Jeffords.

Senator Allard.

Senator ALLARD. Thank you, Mr. Chairman.

In my mind, I do not think there is any question that the climate

has shown a period of warming here. The question that I bring up

and where I see the debate is, what is causing it and whether it

is the changes that are happening and whether they are significant

or not.

I also wonder what your thinking this world might look like

1,000 years from now, looking at the data that we have now. I wondered if maybe each one of you would just give me a brief response

as to what you think of what we are seeing today may look like

projected out over 1,000 years from now. I will start with Dr. Soon.

Dr. SOON. The factors causing climate change are extremely complicated. As I emphasized already, I am very much interested to

learn how the climate changes on a local or regional scale first before I can speak in terms of global climate. After all, local and regional climate are indeed the most relevant climatic factors that

human activities are being influenced by or the reverse way.

As to the factors of climate change, I believe that it is extremely

difficult yet still to confirm the facts of being, let’s say, even the

late 20th century has anything to do with CO2. We do know that

the CO2 is rising, but at the same time we know that climate depends on many other factors. It could be doing it internally all by

itself because of ocean current movements. It could be done, for example, by variability imposed externally from the sun, variable outputs. Our sun is a variable star. That is a very well known fact.

These are the kinds of factors one has to look very comprehensively at. Additional important factors of human activity would include land use changes. Those are very well known factors that one

has to keep a good record, or time history, to really understand

what are the causes of the change.

I don’t think I should speculate anything about futures. It is always very dangerous to talk about the future of any climate.

Senator ALLARD. Dr. Mann.

Dr. MANN. Yes. Well, I certainly agree with your statement that

one of the key issues is what we call the detection or the attribution of human influence on climate, not just how has climate

changed over the past 100 years or past 1,000 years, but can we

actually determine the causal agents of change.

There has been a solid decade of research into precisely that

question by, again, the mainstream climate research community in

addressing the issue of the relative role of natural factors, as well
19

as anthropogenic factors. That includes the role of the sun, the role

of human land use changes, and the role of human greenhouse gas

increases. The model estimates are typically consistent with what

we have seen in the observations earlier.

As far as the next 1,000 years, that is not a particular area of

expertise of mine, but I am familiar with what the mainstream climate research community has to say about that. The latest modelbased projections indicate a mean global temperature increase of

anywhere between .6 and 2.2 degrees Centigrade. That is one degree to four degrees Fahrenheit relative to 1990 levels by the mid21st century under most scenarios of future anthropogenic changes.

While these estimates are uncertain, even the lower value would

take us well beyond any previous levels of warmth seen over at

least the past couple of millennia. The magnitude of warmth, but

perhaps more importantly the unprecedented rate of warming, is

cause for concern.

Senator ALLARD. Dr. Legates.

Dr. LEGATES. Yes. I agree, too, that attribution is one of our important concerns. As a climatologist, I am very much interested in

trying to figure out what drives climate. We know that a variety

of factors exist. These include solar forcing functions; these include

carbon dioxide in the atmosphere; these include biases associated

with observational methods; these also include such things as land

use changes. For example, if we change the albedo or reflected

amount solar radiation, that too will change the surface temperature.

So it is really a difficult condition to try to balance all of these

possible combinations and to try to take a very short instrumental

record and discern to what extent that record is being driven by a

variety of different combinations.

My conclusion probably in this case to directly answer your question is that the temperature likely would rise slightly, again due

to carbon dioxide, but it would be much more responsive to solar

output. If the sun should quiet down, for example, I would expect

we would go into a cooling period.

Senator ALLARD. I guess the question that I would have, now,

you know you have increased CO2. So how is the environment in

the Earth going to respond to increased CO2? Have any of you

talked to a botanist or anything to give you some idea of what happens when CO2 increases in the atmosphere? Plants utilize CO2,

extract oxygen. We inhale oxygen and extract CO2. Will plants be

more prosperous with more CO2? How does that impact the plant

life? Can that then come back on the cycle and some century later

mean more O2 and less CO2?

So I am wondering if any of you have reviewed some of these cycles with botanists and see if they have any scientific data on how

plants respond to CO2 when that is the sole factor. I am not sure

I have ever seen a study. There is moisture and other things that

affect plant growth, but just CO2 by itself. Have any of you seen

any scientific studies in that regard?

Dr. SOON. I have seen that. In fact, I have written a small paper

that has a small section regarding that.

Senator ALLARD. And what was their conclusion?
20

Dr. SOON. The conclusion is that in general, of course, under enrichment of the CO2 in the free air, that yes, plant growth will be

enhanced. For example, as indicated by your chart, the crop yield

can increase by 30 percent or higher for a doubling of CO2, depending on the actual constraints in the field, like types of crops, how

wet or how dry, etc. All of these examples are very well known and

well verified in the field of botany.

Senator ALLARD. My time has run out. Would the other two

agree with what he said?

Dr. MANN. Not quite.

Senator ALLARD. What is your modification?

Dr. MANN. In fact, a number of studies have been done, what are

called ‘‘FACE’’ experiments. They are open canopy experiments in

which CO2 is elevated in the forest and scientists examine the

changes in the behavior of that forest. What scientists at Duke

University are finding is that while there is a tendency for an uptake of CO2 by the plants in the near term, what happens is eventually those plants will die. They will rot. When that happens, this

happens on generational time scales.

Senator ALLARD. Just CO2 being the variable and not moisture

and anything else?

Dr. MANN. Just CO2. The CO2 will go back into the atmosphere

because the plants that take it up——

Senator ALLARD. Do they have an explanation of why the rot occurred?

Dr. MANN. Well, just when things die, they will rot and they will

give up their CO2 back to the atmosphere eventually.

Senator ALLARD. Well, that really does not get to the point I was

trying to make.

Doctor.

Dr. LEGATES. To follow on that, enhanced CO2 and dying plants

would also provide the ability for more plants to therefore grow in

its place. In particular, one of the people on our study, Dr. Sherwood Idso, has done a lot of this study with carbon dioxide and enhanced where you can control the amount of water and energy

available to plants associated with lowered CO2 and higher CO2. Senator ALLARD. So your conclusion is that CO2 increases plant

growth?

Dr. LEGATES. Yes.

Senator ALLARD. OK.

Thank you, Mr. Chairman.

Senator INHOFE. Thank you, Senator Allard.

Senator Carper, we were going to go by the early bird rule. Is

it all right if Senator Thomas goes ahead of you here?

Senator CARPER. Sure.

Senator INHOFE. Senator Thomas.

Senator THOMAS. Thank you. I am a little confused about where

we even ask the questions. Obviously, there is a difference of view.

We are expected to make some policy decisions based on what we

ought to be doing with regard to these kinds of things, but yet

there does not seem to be a basis for that kind of a decision. Where

would you suggest we get the information that is the best information we could get to make policy decisions for the future? Would

each of you like to comment shortly on that?
21

Dr. MANN. Sure. I guess I would reiterate the comments that I

made earlier, that in a National Academy of Sciences study that

was commissioned by the Bush Administration in 2001, the National Academy of Sciences in essence stated their agreement with

the major scientific findings of the Intergovernmental Panel on Climate Change, the IPCC, which is the United Nations panel of scientists, thousands of scientists from around the world who put together a report on the state of our knowledge about all of these

things—climate change scenarios, our uncertainty about various attributes of the climate system. The conclusions that I stated earlier

are the consensus conclusions of the IPCC.

Senator THOMAS. That is where you would go.

Dr. MANN. That is where they have gone, yes.

Dr. LEGATES. I would generally argue the IPCC is a bit of a political document to the extent to which it does present some biased

science. There is a lot of good science in there, but a lot of the conclusions are sort of not borne out by the facts. Having been president of the Climate Specialty Group of the Association of American

Geographers, which is probably the largest group of climatologists

available, I know from talking to rank-and-file members that they

generally—my impression is that most climatologists agree it takes

a rather strong viewpoint.

So I have real serious concerns that it really represents a consensus, and in particular when, for example, in this discussion

when we change dramatically what a lot of people have held true,

that is the Little Ice Age, Medieval Warming and so forth, and replace it with a flat curve very quickly, I do not think we have given

it enough time to really decide if in fact that is an appropriate

change in paradigm.

Dr. SOON. Although I am not able to comment on anything on

public policies, I am certainly able to testify that the science is

completely unsettled. There are just so many things that we do not

know about how the climate really works and what are the factors

that cause it to change, to really jump to the conclusion that it will

all be CO2. Senator THOMAS. Thank you. That helps a lot.

[Laughter.]

Senator INHOFE. You still have some time remaining. Did you

have an opportunity to see the chart up here that Dr. John Reilly,

MIT Joint Program on Science Policy and Global Change? On the

floor yesterday, I talked at some length on this. There seems to be

a lot of consensus that there are some very positive benefits.

Senator THOMAS. It is really interesting, you know, in Schlesinger’s thing it indicates that the temperature after 1940 dropped

until 1977. So that makes you wonder what we ought to do. The

rise in temperature during the 20th century occurred between 1900

and 1940. So now we are faced with making policy decisions where

there is no real evidence that the things that the greenhouse gases

measurable by the U.N. is the basis for doing these things.

I know in science everyone has little different ideas, but I do

think we are going to have to, Mr. Chairman, as you pointed out

yesterday, either take it a little more slowly in terms of policy, or

we are not going to have something more basic to base it on than

we have now in order to make significant policy changes.
22

Thank you.

Senator INHOFE. Thank you, Senator Thomas.

Senator Carper.

Senator CARPER. Thank you, Mr. Chairman. I want to welcome

our witnesses this morning. Dr. Legates, it is great to have a fighting Blue Hen here from the University of Delaware. We are delighted that you are here. Dr. Mann, thanks for coming up, and Dr.

Soon, welcome. We thank you for your time and your interest and

your expertise on these issues, and your willingness to help us on

some tough public policy issues that we face.

Dr. Mann, I would start off if I could and direct a question to

you. I understand we have had thermometers for less than 200

years, and yet we are trying to evaluate changes in temperature

today in this century and the last century with those that occurred

500 or 1,000 or 2,000 years ago. I understand that we use proxies

for thermometers, if you will, and for those kinds of changes in

temperature.

I wonder if you could help me and maybe the committee better

understand how we compare today’s temperature measurements to

the proxies of the past. Are there potential risks with relying on

some of those proxies?

Dr. MANN. Absolutely. We have to use them carefully when we

try to reconstruct the past temperature history. So when I say we

have to use them carefully, it means some of the things that I discussed in my testimony earlier, that we need to actually verify that

if we are using a proxy record to reconstruct past temperature patterns, that proxy record is indeed reflective of temperature

changes. That is something that typically paleoclimate scientists

first check to make sure that the data they are using are appropriate for the task at hand. Of course, we have done that in our

work. I did not see evidence that Soon and colleagues have done

that.

First of all, we next have to synthesize the information. There

have been some misleading statements made here earlier on the

part of the other testifiers with regard to local versus regional or

global climate changes. Of course, we have to assimilate the information from the local scale to the larger scales, just as we do with

any global estimate of quantity. So we take the regional information; we piece together what the regional patterns of change have

been, which may amount to warming in certain areas and cooling

in other areas. Only when we have reconstructed the true global

or hemispheric regional patterns of change can we actually estimate the northern hemisphere average, for example.

A number of techniques have been developed in the climate research community for performing this kind of estimate. My colleagues and I have described various statistical approaches in the

detailed climate literature. Some of the estimates are based on fairly sophisticated techniques. Some of them are based on fairly elementary techniques. Yet all of the results that have been published

in the mainstream climate research community using different

techniques and different assortments of proxy data have given, as

I showed earlier in my graph, the same basic result within the uncertainties. That has not changed. An article that appeared last

month in the American Geophysical Union, which is actually the
23

largest professional association of climatologists, showed that indeed that is the consensus viewpoint of the climate research community.

Senator CARPER. Thank you.

Dr. Legates, if I could ask a question of you, please. Have you

or anyone of your colleagues, at the University of Delaware, to your

knowledge studied the historical climate and temperature records

in our part of the country, in Delaware, the Delmarva Peninsula,

or the mid-Atlantic region?

Dr. LEGATES. We do not have anybody on staff presently that

does paleoclimatology. One of the basic understandings that you

must come up with when you study climate is that you must understand various things of hydroclimatology, physic climatology,

and that includes paleoclimate study. So you must be at least

versed in these things if you are not necessarily a paleoclimatologist.

We do have Dr. Brian Hanson at the University of Delaware who

has looked at glacier movements over long time periods, as well as

Dr. Fritz Nelson who has looked at changes associated with permafrost locations.

Senator CARPER. If someone were to do a study for our part of

the country, what do you think they might find?

Dr. LEGATES. A study regarding?

Senator CARPER. Historical climate and temperature changes.

Dr. LEGATES. Over the East Coast of the United States? Most of

the assessments indicated that generally the East Coast has gone

through a variety of changes over long time periods. Historically,

we have had a condition where in the 1960’s, for example, we had

conditions where there was much more snowfall. We have had a lot

of variability associated with air temperature rising and falling

over the local conditions. Variability is usually the characteristic of

climate over the near-term as well.

Senator CARPER. OK. Dr. Soon, if I could ask you and maybe Dr.

Legates the same question, the following question. That question

is, do you believe that it is possible to emit unlimited amounts of

CO2 into our atmosphere without having any impact on climate or

temperature?

Dr. SOON. I do not know how to precisely answer the question.

If you fill up every single molecule of the air with CO2, that would

be poisonous, of course. I do not know the answer to the question,

but I do like to add about the evidence available on climate change.

Senator CARPER. Before you do that, let me direct, if I could, the

same question to Dr. Legates. I do appreciate your candor. It is not

everyday that we find that here in this hall.

Dr. LEGATES. Generally, what we have found is that as carbon

dioxide has increased, the temperature has followed, where in some

cases historically the temperature has gone up and the carbon dioxide has fallen. So generally from a purely physical point of view,

if you do increase the carbon dioxide, you should wind up with

some trapping of gases, and hence wind up with a slightly increased temperature.

The question is, there is a lot of additional feedbacks associated

with it. For example, warmer surface temperature leads to more instability or rising air which leads to more cloudiness. Clouds can
24

warm at night, but also reflect energy in the daylight. So you have

these odd playbacks into the climate system which make it very

difficult to say that if I hold everything else constant and change

one variable, what will happen. Well, in reality, it is impossible to

hold everything constant because it is a very intricate and interwoven system that one change does have feedbacks across the entire spectrum.

Senator CARPER. Thanks. I think my time has expired, Mr.

Chairman. Is that correct?

Senator INHOFE. Yes. Thank you, Senator Carper.

Senator CARPER. Thank you.

Senator INHOFE. We will have another round here. In fact, I will

start off with another round. Let’s start with Dr. Legates. Dr.

Legates, was the temperature warmer 4,000 to 7,000 years ago

than it is today?

Dr. LEGATES. My understand was during about 4,000 to 7,000

years ago, in a period referred to as the climatic optimum, which

sort of led to enhanced agriculture and led to development of civilization, generally the idea is that warmer temperatures lead to

more enhanced human activity; colder temperatures tend to inhibit. Again, as we get back 4,000 to 7,000 years ago, it becomes,

the error bars are getting wide as well. But the general consensus

is that temperatures were a bit warmer during that time period.

Senator INHOFE. OK. Senator Thomas had something about, he

had alluded to 1940. Yesterday when I was giving my talk and

doing the research for that, it was my understanding that the

amount of CO2 emitted since the 1940’s increased by about 80 percent. Yet that precipitated a period of time from about 1940 to 1975

of a cooling-off period. Is that correct?

Dr. LEGATES. That is correct. It is sort of a perplexing issue in

the time series record that from 1940 to 1970 approximately, while

carbon dioxide was in fact increasing, global temperatures appear

to be decreasing.

Senator INHOFE. Dr. Mann, you have I might say impugned the

integrity of your colleagues and a few other people during your

presentation today. The Wharton Econometric Forecasting Associates did a study as to the effect of regulating CO2 and what would

happen. American consumers would face higher food, medical and

housing costs; for food, an increase of 11 percent; medicine, an increase of 14 percent; and housing, an increase of 7 percent. At the

same time, the average household of four would see its real income

drop by $2,700 in 2010.

Under Kyoto, the energy and electricity prices would nearly double and gasoline prices would go up an additional 65 cents a gallon.

I guess I would ask at this point, what is your opinion of the Wharton study?

Dr. MANN. OK. First, I would respectfully take issue with your

statement that I have impugned the integrity of the other two testifiers here. I have questioned their, and I think rightfully, their

qualifications to state the conclusions that they have stated. I provided some evidence of that.

Senator INHOFE. Well, ‘‘illegitimate, inexperienced, nonsense’’——

Dr. MANN. Those are words that I used. Correct.

Senator INHOFE [continuing]. That is a matter of interpretation.
25

Go ahead.

Dr. MANN. I would furthermore point out that the very models

that I have referred to track the actual instrumental warming and

the slight cooling in the northern hemisphere. There was no cooling

of the globe from 1940 to 1970, the northern hemisphere——

Senator INHOFE. OK. The question I am asking you is about

WEFA.

Dr. MANN. I am not a specialist in public policy and I do not believe it would be useful for me to testify on that.

Senator INHOFE. Dr. Legates, have you looked at the report that

Wharton came out with concerning the possible effects, economic

results of this?

Dr. LEGATES. Again, I am not a public policy expert either, and

so the economic impacts are not something which I would be qualified to testify on.

Senator INHOFE. OK, Dr. Legates, do you think you have more

data than Dr. Mann?

Dr. LEGATES. I think we have looked at a large variety of time

series. We have looked at essentially a large body of literature that

existed both prior to Dr. Mann’s analysis and since Dr. Mann’s

analysis, in attempting to figure out why his curve does not reflect

the individual observations. It is one issue associated with when

you put together data sets, to make sure that the composite sort

of resembles the individual components.

Senator INHOFE. OK. The timeline, Dr. Mann, is something I

have been concerned with, and those of us up here are listening to

you and listening to all three of you and trying to analyze perhaps

some of the data that you use and the conclusions you came to,

having been 4 or 5 years back, compared to a study that was done

referring to Smithsonian-Harvard, the 1,000-year study that was

just completed, or at least given to us in March of this year. I

would like to have each of you look at the chart up here and just

give us a response as to what you feel in terms of the data that

both sides are using today.

Dr. MANN. I guess you referred to me first?

Senator INHOFE. That is fine. Yes.

Dr. MANN. OK. Well, I think we have pretty much demonstrated

that just about everything there is incorrect. In a peer-reviewed

publication that was again published in the Journal Eos of the

American Geophysical Union about a month ago, that article was

cosigned by 12 of the leading United States and British climatologists and paleoclimatologists. We are already on record as pretty

much pointing out that there is very little that is valid in any of

the statements in that table. So I think I will just leave it at that.

Senator INHOFE. Do the other two of you agree with that?

Dr. LEGATES. If I may add, the Eos piece was actually not a refereed article. It is an Eos Forum piece, which by definition is an

opinion piece by scientists for publication in Eos. That is what is

contained on the AGU Web site for Eos Forum.

Senator INHOFE. All right. Let me ask one last question here. Dr.

James Hansen of NASA, considered the father of global warming

theory, said that the Kyoto Protocol ‘‘will have little affect on global

temperatures in the 21st century.’’ In a rather stunning followup,

Hansen said it would take 30 Kyotos, let me repeat that, 30 Kyotos
26

to reduce warming to an acceptable level. If one Kyoto devastates

the American economy, very much by the findings of Wharton,

what would 30 Kyotos do? Is Dr. Hansen one of the most respected

scientists in your field or is he way off base?

Dr. MANN. Dr. Hansen is certainly one of the most respected scientists in my field and I personally have great scientific respect for

him. I think that his conclusions have been grossly taken out of

context. His point is simply that Kyoto would, and this is his point,

these are not my opinions, would do very little to ameliorate the

warming over the next century for two reasons.

No. 1, there is something that scientists call the commitment to

warming. Once we put CO2 into the atmosphere, it takes many decades, on orders of decades to maybe centuries for it fully to equilibrate with the ocean and the atmosphere. So some of that CO2 is

taken up by the ocean. So the effect of it is delayed. So cutting back

on CO2 now may not affect global temperatures for 50 years, but

50 years later it is going to come back to roost.

Senator INHOFE. All right, that was a rather long answer, so let

me just, with the indulgence of my fellow Senators here, I just

want to ask one last question. I quoted Dr. Frederick Seitz, the

past president of the National Academy of Sciences yesterday, and

professor emeritus at Rockefeller University, who compiled an Oregon petition which says there is no convincing scientific evidence

that human release of carbon dioxide, methane and other greenhouse gases is causing, or will in the foreseeable future cause catastrophic heating of the Earth’s atmosphere and disruption of the

Earth’s climate.

Moreover, there is substantial scientific evidence that increases

in atmospheric carbon dioxide produce many beneficial effects upon

the natural plant and animal environments of the Earth. Do each

of the three of you agree or disagree with his statement?

Dr. SOON. I agree.

Dr. MANN. I find little in there to agree with.

Dr. LEGATES. I would tend to agree.

Senator INHOFE. All right.

Senator Jeffords.

Senator JEFFORDS. As you may know, this is to all of you, the

editor-in-chief of the magazine Climate Research resigned the position yesterday over problems with Dr. Soon’s paper. In an e-mail

sent to my staff, he said,

‘‘My view, which is shared by many, but not all editors and review editors

of Climate Research, is that the review of the Soon et al paper failed to detect

significant methodological flaws in the paper. The critique published in the Eos

journal by Mann et al is valid. The paper should not have been published in

this forum, not because of the eventual conclusion, but because of the insufficient evidence to draw this conclusion.’’

What methodological flaws does he mean?

Dr. Mann.

Dr. MANN. Well, I have tried to outline the most severe of those

methodological flaws. I believe it is the mainstream view of just

about every scientist in my field that I have talked to that there

is little that is valid in that paper. They got just about everything

wrong. They did not select the proxies properly. They did not actually analyze any data. They did not produce a reconstruction. They
27

did not produce uncertainties in a reconstruction. They did not

compare to the proper baseline of the late-20th century in trying

to make conclusions about modern warmth.

So I think it is the collective view of our entire research community that that is one of the most flawed papers that has appeared

in the putative peer-reviewed research in recent years.

Senator JEFFORDS. Dr. Soon, do any scientists besides your coauthors support using wetness or dryness as indicators of past temperatures, instead of actual temperatures or proxy data that reflects temperatures?

Dr. SOON. As we explain clearly in our paper, and as it has been

highly mischaracterized by my fellow colleague here, Dr. Mann, we

certainly agree when we speak in term of the Medieval Warm Period, temperature is one of the important parameters. As we emphasize and specify in our papers that climate is not temperature

alone. One has to look in terms of the water cycle, in terms of even

the air cycles, in terms of the vegetation changes. These are the

kind of details that we did not make any presumptions, but simply

want to look at the patterns of change geographically all over the

world, and see how complete the datas are, and then begin to start

to see how do we assemble all such information.

Senator JEFFORDS. This is for the whole panel. I would like to

know whether the unusual melting of Greenland ice sheets shown

in this picture over the years 2001, 2002 and 2003, has been

matched in the long-term climate history any other time? And according to NASA, by the end of the year 2002 season, the total area

of surface melt in the Greenland ice sheet had broken all known

records. By the end of that summer ‘‘Sea ice levels in the Arctic

were the lowest in decades and possibly the lowest in several centuries.’’

NASA says this warming is happening faster and earlier than in

previous periods. What is happening now and what is going to happen if this continues?

Dr. Mann.

Dr. MANN. Well, this is, of course, one particular region, one potentially isolated region, Greenland, in which there is evidence of

mass oblation of ice. But if we look at what is going on the world

over, mountain glaciers in the tropics throughout the world, glaciers in both the northern hemisphere and the southern hemisphere, what is seen is that glacial retreat during the late 20th

century is unprecedented on similar time scales to the time scales

I have spoken of before, the past 1,000 to 2,000 years.

I believe Professor Lonnie Thompson of Ohio State University

has testified in this Senate before with regard to the dramatic evidence of worldwide glacier retreat. So that is a cause for concern.

It is a harbinger of the warming because in fact the warming that

is shown in those glacier retreats is actually warming that we are

already committed to for decades to come.

Dr. LEGATES. Historically, it has been demonstrated in the refereed literature that much of this glacial retreat actually began in

the late 1800’s, before much of the carbon dioxide came into the atmosphere. This is very much consistent with the demise of the Little Ice Age and longer time-scale variations. Therefore, it is very

difficult to say that these kind of events are directly attributable
28

to human impacts on the climate, when they in fact pre-date

human impacts on the climate.

Senator JEFFORDS. Dr. Soon.

Dr. SOON. My only comment regarding that kind of chart or the

claim that it has never happened before is that to think about the

available, detailed observation that we have. We do not really have

any satellite record longer than 20 to 30 years, so the statement

that it has never happened before I think is dangerously inaccurate.

Senator JEFFORDS. Dr. Mann.

Dr. MANN. Yes. It is unfortunate to hear comments about the

supposed inconsistencies of the satellite record voiced here, years

after that has pretty much been debunked in the peer-reviewed literature, in Nature and Science. Both journals have in recent years

published several rigorously peer-reviewed articles indicating that

in fact the original statement that the satellite record showed cooling was flawed because the original author, John Christy, did not

take into account a drift in the orbit of that satellite, which actually leads to a bias in the temperatures from the satellite.

Christy and colleagues have claimed to have gone back and fixed

that problem, but just about every scientist who has looked at it

says that their fix is not correct. If you fix it correctly, then the satellite record actually agrees with the surface record, indicating fairly dramatic rates of warming in the past two decades.

Senator JEFFORDS. I have one last question, Dr. Mann. What are

the implications of your peer-reviewed work for future manmade

warming?

Dr. MANN. As I said before, there have been a number of modeling simulations that have shown a fairly good match to our reconstruction and that of several independent research groups who

have also produced these reconstructions of northern hemisphere

temperature. So to the extent that the models match that record

of the past 1,000 years when they are forced with various estimates

of natural changes in the system, it gives us reason to trust what

the models say about the future. As I testified before, the models

tell us that we are likely to see a one degree to four degree Fahrenheit warming by the mid-20th century, given most predicted scenarios of continued anthropogenic influence on the climate.

Dr. LEGATES. If I may add something, one of the things I have

heard is that science has been debunked and, for example, we

pointed to Dr. Christy’s curve up here and said that because one

paper has been written, that curve is now called into question. We

have talked about—you mentioned von Storch’s resignation from

Climate Research because apparently he has admitted that this

paper never should have been published.

I want to point out that science debate goes on and on. In particular, Dr. Christy has had some very important contributions to

indicate that his curve is not incorrect. That is part of scientific debate. Furthermore, I will say with respect to Climate Research,

Otto Kinne, who is director of Inter-Research, the parent organization of Climate Research, asked Chris de Freitas who was the editor who served on the Soon and Baliunus papers, and I can relay

this because I am a review editor of Climate Research so I am familiar with what has been taking place.
29

There were several people complaining that Chris de Freitas

should be removed simply because he published the Soon and

Baliunus paper. That question was brought to Otto Kinne. He

asked for Chris de Freitas to provide him with the reviews, the

changed manuscripts and so forth. He provided a letter in late

June to all of us in which he said,

‘‘I have reviewed the evidence and I have indicated that the reviews, four for

each manuscript, in fact there was a second or an earlier Soon and Baliunus

article on another topic that was also called into question by these people leveling charges.’’

Essentially what he concluded was that the reviewers provided

good and appropriate comments; that Doctors Soon and Baliunus

provided an appropriate dressing or incorporation of these concerns; and that Chris de Freitas had in fact provided analysis appropriately.

Toward that end, Dr. von Storch was approached. Climate Research was putting in an editorial stating essentially this article

should never have been published. Otto Kinne was informed and

he has asked him not to submit that because it is not founded, and

as a result Dr. von Storch, I now understand, has said he would

resign.

Senator JEFFORDS. Dr. Mann.

Dr. MANN. Yes, just a very short comment. It is unprecedented

in my career as a scientist to hear of a publisher of a journal going

in and telling the editor-in-chief that he cannot publish an editorial. I find that shocking and a bit distressing. I do not know

what the circumstances are behind it, but it is disturbing.

Dr. LEGATES. It is also unprecedented to find an editor being attacked, and this has also happened with the editorial staff of Energy and Environment, which is the other paper, to find an editor

attacked for simply publishing an article that has been peer-reviewed and approved by reviewers.

Senator INHOFE. All right. The time has expired. We are 4 minutes over.

Senator JEFFORDS. I think that my witness should have the last

word on my question, if I could. Dr. Mann, do you have any response to that?

Dr. MANN. Actually, my understanding is that Chris de Freitas,

the individual in question, frequently publishes op/ed pieces in

newspapers in New Zealand attacking IPCC and attacking Kyoto

and attacking the work of mainstream climatologists in this area.

So this is a fairly unusual editor that we are talking about.

Senator INHOFE. All right, thank you.

Senator Clinton has joined us. Senator Clinton would you like to

have your round now?

Senator CLINTON. Thank you very much, Mr. Chairman. I thank

you for this hearing. I understand that the questioning and the testimony has been somewhat lively, if not controversial and contested. The bottom line for me is whether we are doing what we

need to do to ensure the best possible climatology outcome for future generations. I would stipulate that the Earth’s climate has

changed through the millennia. There is no doubt about that. I

have read enough to know that we have had ice ages and we have

had floods and we have had volcanoes. We have had lots of natu-
30

rally occurring events which have affected our climate. We have El

Nin ̃ o and his spouse, El Nin ̃ a. We have all of that. That is not debatable.

The issue is whether the introduction and acceleration of anthropogenic activity primarily related to the burning of fossil fuels is

putting into place conditions that will make it difficult, if not impossible for the Earth to regain its balance, that will support the

conditions of life that we have inherited and are blessed with.

I know these debates have political implications because heaven

forbid that we would tell somebody in the private sector not to do

something, or that we might have to make sacrifices in the quality

of our life for future generations. I think that it is not useful to

carry out this kind of argumentation when it is clear that by the

very nature of human development and industrialization, we have

changed what is in the atmosphere, what is in the earth, what is

in the waters.

That does not mean there was no change before we came along,

and certainly in the last century that change has accelerated because the quality of life has improved, we have created chemicals

that were never known in nature before. We have done a lot of

things.

But I think that our goal should be to try to figure out how to

do no harm or do the least amount of harm, and to ask ourselves,

what are we willing to perhaps sacrifice to make sure that we are

not contributing to irreversible changes. I know that academia is

probably the most political environment in America. I was once on

a staff of a law school. It was more difficult than any politics I had

ever been involved in beforehand. I know that people have very

strong opinions and hold on to them.

From my perspective, I just want to believe that I am making a

contribution to ensuring that the quality of life for future generations is not demonstrably diminished. I would feel terrible if I participated, either as a willing actor or a bystander, in this potential

undermining of our Earth’s sustainability.

So Dr. Mann let me ask you, what was the Earth’s climate like

the last time that there was atmospheric concentration of carbon

dioxide at today’s levels of 370 parts per million?

Dr. MANN. Thank you, Senator, that is an excellent question. We

have to go back fairly far into the past to find CO2 levels approaching the CO2 levels today. Ice core studies that have been done over

the past decade or so have told us that today’s CO2 level is unprecedented now in at least four glacial or inter-glacial cycles. That is

more than 400,000 years.

In fact, now as we look back from other evidence that is a bit

more tentative, it appears that modern CO2 levels probably have

not been observed in 10 million to 20 million years. So we have to

go back to the time of the dinosaurs, probably, to find CO2 levels

that we know were significantly higher than CO2 levels today.

Some people will say, ‘‘Well look that was a great time.’’ The dinosaurs were roaming near the poles. It was warm near the north

pole. There were palm trees in the poles. Isn’t that what we want?

Well, that was a change that occurred on time-scales of tens of millions of years. What we are observing right now is a similar change

that is occurring on time-scales of decades.
31

Senator CLINTON. Thank you. Thank you, Dr. Mann.

Senator INHOFE. Senator Clinton, if you would like to have some

more time, since we are on the second round now, feel free to take

another couple of minutes.

Senator CLINTON. Thank you very much, Mr. Chairman.

I guess that is, for me, the dilemma, because I certainly understand the testimony of the other two witnesses, and I read with

great interest former Secretary Schlesinger’s op/ed. I know that

there are those, who are in a minority, let’s at least admit that,

who are in a minority, but who certainly have a very strongly held

set of beliefs, and I respect that.

But I do believe that the compression of time in which these

changes are occurring is extraordinarily significant. We can go back

and look at the Earth’s natural 125,000-year cycle, but I do not

think we want to risk the enormous changes that could occur. I do

not think we have a million or 10 million years or even 100,000 to

experiment.

I think that the challenge confronting us is not to put our heads

in the sand and let the academic argument take place, but figure

out how in a sensible, prudent manner we could ameliorate these

changes significantly enough so that if Dr. Soon and Dr. Legates

are right, no harm done. If Dr. Mann is right, we will have saved

ourselves a lot of potential damage and difficulty.

So I hope that we could put our heads together. I commend my

two colleagues, both Senator Jeffords and Senator Carper, who

have very sensible legislative answers to trying to get a handle on

this. As I have said in this committee before, I stand ready to figure out ways to hold harmless our industrial base and others. I

think it is a significant enough political, economic and moral challenge that if there are ways to make it financially possible for companies to do what needs to be done with respect to carbon dioxide

and other atmospheric pollutants that have accelerated their presence in our atmosphere so dramatically in the last 100 years, I

think we should do that.

This is not just a private sector problem. We all have benefited

from the increasing use of fossil fuels, for example. Our standard

of living is dramatically better. One of our problems is what is

going to happen if China and India get a standard of living anywhere comparable to ours, and then begin to really—and I see Dr.

Soon nodding—I mean really dump into the atmosphere untold

amounts of new pollutants of whatever kind, leading certainly with

carbon dioxide.

So this is a problem we need to get ahead of, and it is not a problem that the United States alone should be responsible for. It is not

a problem that the private sector alone should be responsible for.

But I believe, just as a prior generation of decisionmakers really

put a lot of work into the law of the oceans and trying to figure

out how we could protect our oceans, we need to do the same on

the atmospheric level. There has got to be a way that we can come

together on this big challenge.

So Mr. Chairman, I appreciate your continuing attention to this.

I, for one, stand ready to work with you and our other colleagues

because I just think this is too risky a proposition not to act on,

given the weight of opinion, even with the dissenters, who I think
32

do rightly point out the incredible natural cycle, but we are now

so influencing that natural cycle, I do not know if we have the time

to contemplate the balance once again regaining itself in our wonderfully regenerating Earth.

Senator INHOFE. Thank you, Senator Clinton.

Senator Carper.

Senator CARPER. Thanks, Mr. Chairman. I just want to followup.

Senator Clinton was kind in her comments on the legislation, the

one that Senator Jeffords has introduced and second on legislation

I have introduced along with Senators Judd Gregg, Lincoln Chafee

and Lamar Alexander.

Are any of you familiar with that legislation? Would you like to

become familiar over the next 5 minutes?

[Laughter.]

Dr. SOON. No, we will stick to science. Politics is too complicated.

Senator CARPER. All right. That may be the best approach.

We are trying to figure out if there is a reasonable middle ground

on this issue. I am part of a group that Buddy MacKay, a former

colleague of mine from Florida, calls the flaming moderates or

flaming centrists. We can spend a whole lot of time discussing the

impact of Kyoto caps, or we can focus on what steps we actually

need to take.

The approach that Senators Gregg and Chafee and Alexander

and myself have taken, at least with respect to four pollutants, we

say unlike the President’s proposal where he only addresses sulfur

dioxide and nitrogen oxide and mercury, and does not address CO2, as you know, because he thinks we need to study it a bit more. Our

approach says that there ought to be caps on CO2; that they should

be phased in; that we should use a cap and trade system; we

should give utilities the opportunity to buy credit for levels of CO2

emissions that they maintain at high levels; and they should be

able to contract with, among others, farmers and those who would

be forced out of lands to change their planning patterns or change

their animal feedlot operations in order to be able to sequester

some of the CO2 that occurs in our planet.

We have something called new source review. The President

would eliminate it entirely. I think in Senator Jeffords’ approach,

it is pretty much left alone. There is a good argument that says

that utilities under current law, if they make some kind of minor

adjustment and minor investment in their plant, that they have to

make a huge investment with respect to the environmental controls. As a result, it keeps them from making even common sense

kinds of investments in their plants—sort of the laws of unintended consequences. That is sort of the approach that we have

taken.

Now that you know all about it, if you were in our shoes, what

kind of an approach would you take? Let me just start with our

University of Delaware colleague here, Dr. Legates.

Dr. LEGATES. Generally, I favor no regrets policies, where they

have other applications as well. But again, getting into the politics

and the non-science aspects of what to do is out of my area of expertise. I may have my own beliefs, but they are no more important

or less important than the average person. I would rather not testify to those here.
33

Senator CARPER. If you were convinced, and some of my colleagues have heard me talk about Dr. Thompson before, I don’t

know that they testified before this committee, but Doctors Knoll

and Thompson spend their lives going around the world and they

chart the disappearance of snow caps in some of the tallest mountains. I first met them here in Delaware about 5 or 6 years ago to

receive an award for their research.

But they tell us that the snow caps around some of the tallest

mountains in the world, the Himalayas and others, are not just disappearing, they will be gone, and they will be gone in our lifetime.

When I heard them speak and talk about their work and what they

were charting and finding, it got my attention. When you hear

that, Dr. Legates and Dr. Soon, how does it affect you?

Dr. SOON. As a scientist, I am still questioning the actual evidence. The fact is that meltings may be recorded for certain glaciers. But among the things that we know is that there are about

160,000 glaciers around the Earth, but only 40 to 50 glaciers have

been measured for 10 years or longer to tell us how much the ice

has accumulated or has ablated.

Some of the specific melting examples, like Kilimanjaro, that Dr.

Lonnie Thompson has looked at, or some places in Peru may be

true. But the quality of the data records is really telling us that

we do not have enough strong evidence to suggest that all the ice

will disappear quickly and completely, or that all of it is unprecedented. Climate change is part of nature. As I tried to emphasize

in my research by looking carefully into all the climate proxies,

there are large local swings in the climatic changes.

Senator CARPER. Dr. Soon, what would it take to convince you

that this is a problem we need to deal with?

Dr. SOON. As to some of the glaciers disappearing now in some

parts of the mountains, I do not consider that to be either a problem or strong evidence——

Senator CARPER. No, no, the big issue. What would it take with

respect to the concerns about global warming fed by CO2 accumulation, what would it take to convince you that this is a problem we

need to do something about?

Dr. SOON. OK. Scientifically, I would go by this very simple test.

The simple test should be that the warming should be occurring

first at the troposphere, the layer of air about four kilometers

above us. That is a key part of the atmosphere that one should expect the CO2 greenhouse effect to work its way downward toward

the surface. I would urge, of course, very seriously that we do not

lose sight in all these debates about science, we must sustain a certain kind of level of observational effort to keep track of data so

that while we are arguing around what to do, that one has some

records about any level of change that may occur.

So what it would take is that the CO2 warming should happen

at the layer of air four kilometers first. I would require it be

strongly sustained for maybe 20 years or so. Then I would really

believe that we have clear CO2 fingerprints somewhere.

Senator CARPER. Mr. Chairman, I know my time has expired.

Could I just ask that same question of Dr. Legates? What would

it take to convince you?
34

Dr. LEGATES. Proof. Generally the problem we have seen in the

record is that there is an awful lot of variability and there are

things where changes occur, for example, between 1940 and 1970

where the temperature decreased, even though carbon dioxide was

increasing. That sort of indicates to me that carbon dioxide may

not be the biggest player in the game. Solar variability is likely to

be the bigger player, changes in solar output. After all, if the sun

goes out, our temperature drops considerably. We know historically

that as the sun fluctuates in terms of its output, the climate does

respond.

So there are a lot of other factors involved and I am not entirely

convinced, based upon the proof, that carbon dioxide is a driving

force. It is a contributory force in a small case, but not driving

enough, because we wind up making policies potentially that can

lead us to try to keep back the ocean, if you will. You cannot stop

the waves from coming in.

Senator CARPER. Dr. Mann.

Dr. MANN. Two quick points. First of all, it grates on me to hear

this argument about cooling from 1940 to 1970 continually cited

here as evidence against anthropogenic climate change. That cooling was almost certainly anthropogenic and there has been a decade of research demonstrating that, anthropogenic sulphate

aerosols, which have a cooling effect on the climate. What is happening now is that the much greater effect of increasing greenhouse gas concentrations is overtaking that small cooling effect of

sulphate aerosols, also an anthropogenic influence, but not the one

that is going to take us to doubled levels of CO2 in the next century.

One quick other comment, if I could. Lonnie Thompson’s work,

which is some of the best work in our field, it is not like he has

been looking for ice cores that are melting. He is actually looking

for ice cores that are not melting because he wants to get long

records. So if there is any belief that there might be some bias in

the glaciers that he has gone to, if anything it is the opposite. He

is looking for long records, so that makes it that much more impressive that they are all melting.

Senator CARPER. Thank you.

Senator INHOFE. Senator Allard.

Senator ALLARD. Thank you, Mr. Chairman.

What agency do you think we probably have the most expertise

in as far as climatology change and what is happening with global

climate? Would that be the agency on the National Oceanographic

and Atmospheric Science, would that probably be where we would

have most of our experts? If not, which agency do you think we

would have most of our experts as far as the government is concerned? To any member of the panel, I would like to know whether

any of you concur or not.

Dr. MANN. Well, I think that the different agencies specialize in

different areas of the climate change research question, if you will.

NOAA’s specialty is in looking at climate variability, particularly

with regard to oceanic variability. So they emphasize that area of

the research. A lot of the peer-reviewed research, for example Lonnie Thompson’s work that we just spoke of, is funded by the Na-
35

tional Science Foundation in large part. There are other organizations.

Senator ALLARD. The Foundation, is that an agency of the Federal Government?

Dr. MANN. Well, not directly.

Senator ALLARD. The question is, what is an agency of the Federal Government? The only one that I could think of was NOAA,

but are there other agencies?

Dr. LEGATES. NASA does a lot of research, satellite-related efforts trying to estimate climate trends, incorporating satellite

measurements as well.

Dr. MANN. As well as the Department of Energy and EPA.

Senator ALLARD. Yes, the Department of Energy.

Dr. LEGATES. The Department of Interior as well.

Senator ALLARD. OK. But we do not have any, say, each agency

would have their own area of interest, but it seems to me that we

need to look at global warming from a total perspective and I am

trying to figure out if there is an agency that does that. I have

talked to people within NOAA. There are arguments going on within that agency on the very topic that we are talking about here.

There is absolutely no consensus within the agency, and I am trying to figure out if there is an agency out here that is taking on

an overall view. I guess really there is not. We are just going to

have to rely on the science community somehow or the other pulling all these views out from these various agencies. They look at

the atmosphere, like you say, NASA looks at the stratosphere and

higher up where your satellites are.

Dr. LEGATES. On the surface, too.

Senator ALLARD. We need somebody that looks at the effect on

plant life, animal life, the total cycle; oxygen, CO2 and all that before you reach conclusions. I am just wondering who pulls all this

together so that we can come up with a total picture of what is

happening as far as changes to this Earth is concerned, because it

is more than just one science.

Dr. Mann.

Dr. MANN. There is a program, the U.S. Global Change Research

Program, which seeks to coordinate the various agencies on issues

of fundamental importance in the research of climate variability

and climate change. So I think that is their role.

Senator ALLARD. OK. I want to get back a little bit to the absorption of sunlight, for example, on the Earth’s surface. It seems to

me, and I don’t know how accurate this is. I want to check this out

because it has been suggested to me by a number of people, that

our absorptive surface on the Earth has increased. We still have

the same amount of surface, but for example you have pavement

in urban areas. We know that pavement is absorptive. Has that

had an impact on global warming?

Dr. MANN. Most definitely.

Senator ALLARD. In your view?

Dr. MANN. Yes, your statement is correct. The main increase in

the absorption by the Earth’s surface is due to the melting of snow

and ice. That has certainly had a very large influence on the warming, but it is part of the warming.
36

Senator ALLARD. So you do not think the construction of—we

have more pavement than we did two centuries ago or a century

ago.

Dr. MANN. Most models suggest that that is a cooling.

Senator ALLARD. Is there enough of that that we have more

fields probably because of agriculture throughout the world, just

not the United States. This is all over the world.

Dr. MANN. Yes. Most estimates suggest that there is a small cooling of the Earth’s surface due to those changes.

Senator ALLARD. Would you all agree to that?

Dr. LEGATES. The pavements are associated with the urbanization effect, which is part of the problem associated with where we

have observational measurements. Generally where you have a decrease in the light and heat exchange that is evaporation of water

taking place because we have removed trees; the fact that you have

darker surfaces; you have canyon-like effects. All of these lead to

warmer temperatures in the city. The urban heat ion effect is welldocumented and that is where virtually all of our observations are

located.

But there are also changes in land surface effects by the fact that

we are removing vegetation and replacing it with grasslands, for

example, deforestation, de-vegetation. A lot of these are on very

large-scales too, and they do change the color and character of the

Earth’s surface and hence the absorptive characteristic.

A lot of the cryosphere, a lot of the ice and snow is temporally

variable. We have a growing area and decreasing area, so that does

integrate itself out over time to some extent.

Senator ALLARD. Does the absorptive surface of the Earth’s surface have an impact on whether we have a warmer temperature or

not today?

Dr. LEGATES. Yes, absolutely.

Dr. SOON. Oh certainly, yes.

Senator ALLARD. I am a little bit confused of what the final view

is. Do we increase temperature or do we cool the temperature?

Dr. MANN. Can I comment?

Senator ALLARD. Yes. You said that it cooled.

Dr. MANN. Yes, the effects that——

Senator ALLARD. OK, now, I would like to hear from——

Dr. Mann [continuing]. That is not the whole story. What he said

is correct, but the effect that is dominant in models in about three

or four different studies published in the past 2 years on precisely

this question is actually the change in absorption by the land surface due to deforestation and other agricultural changes. That leads

to an overall cooling of the globe, even in the face of other possible

effects of warming.

Senator ALLARD. Would you agree with that?

Dr. LEGATES. Not necessarily. In particular, you are changing a

characteristic, but you are also changing the other interactions.

You are changing the vegetation and you are changing the evaporative characteristics.

Senator ALLARD. But your bottom line is that you think that,

with increased absorptive rate on the Earth’s surface, it has a cooling or a warming effect?
37

Dr. LEGATES. If you increase the absorption rate on the Earth’s

surface, you will have to have a net warming effect.

Dr. SOON. You have to have a warming.

Senator ALLARD. You have a warming.

I mean, to me this is a fairly fundamental concept, and here we

are, we have disagreement at this table about that.

Dr. SOON. I don’t think Dr. Mann is listening to your question.

Senator ALLARD. To me, from my practical experience, it seems

to me that there is a warming effect. When I walk out on a pavement with my bare feet, they get burnt. If I walk on grass, my feet

feel a lot cooler. I just look at it from a practical aspect. So Dr.

Mann, would you explain to me why there is a difference in what

you say and what I am feeling physically when I walk on the surface of the Earth?

Dr. MANN. Sure. When you are walking, you are only covering

a pretty small fraction of the surface area of the Earth. The effect

that you are talking about, for example, the urban heat island effect of blacktop and its tendency to absorb heat, that is overwhelmed by larger-scale changes that we do not necessarily see because they are not where we are walking around. Large areas of

the surface area of the Earth are being changed in terms of their

vegetation characteristics. That has a net cooling. The answer on

that is clear in the peer-reviewed research.

Senator ALLARD. The reason I bring this up is that in the State

of Colorado we have a lot of variation. We go from 3,000 to over

14,000 feet and we have a lot of different ecological systems in Colorado, depending on altitude and moisture and everything.

We have a weather reporting station in a rural area, in the

plains of Colorado, and the data that I am getting from them, there

is no indication of change as far as temperature is concerned. Yet

as we move into the more urban areas, then we get weather stations that are indicating a higher temperature. So I am wondering

worldwide, with the urbanization of the world, is there a possibility

that we could be dealing with some temperature changes that are

a result of the absorptive surface on the Earth like urbanization,

you mentioned urbanization, we have a lot more than we used to

have. Doesn’t this have an impact on temperature?

Dr. LEGATES. Yes, definitely. Essentially, I do not think Dr.

Mann answered the question appropriately in that your basic question was, if we absorb more radiation at the surface, will the temperature not go up? That is correct. The temperature will go up.

In a sense, that is physics.

Senator ALLARD. Would you agree with that, Dr. Mann?

Dr. MANN. No. He has gotten about three different things wrong

here.

Senator ALLARD. No, listen.

Dr. MANN. His first statement is wrong.

Senator ALLARD. I understand your statement. You are taking a

broader atmospheric picture. You are taking a total picture. But

the statement he made at this point, would you agree with that?

Dr. MANN. No. It is not correct.

Senator ALLARD. You would not agree?
38

Dr. MANN. The statement that he made was that there is an

urban heat bias in the estimate of the surface temperature changes

of the Earth.

Senator ALLARD. I did not hear him say that.

Dr. MANN. He said that earlier when he talked about urban heat

bias.

Senator ALLARD. I am talking about the comment that he just

made. Would you repeat the comment, Dr. Legates?

Dr. LEGATES. I essentially said the basic physics is that if you

make the Earth’s surface darker, you will absorb more energy, you

will reflect less energy, as a result the surface temperature should

increase.

Senator ALLARD. Would you agree with that scientific fact?

Dr. MANN. That statement would be in the first chapter of most

textbooks. Yes.

Senator ALLARD. Dr. Soon, I did not mean to ignore you. You

wanted to say something?

Dr. SOON. I tried to just emphasize that that is all you are asking.

Senator ALLARD. Yes.

Dr. SOON. If you increase absorptivity of the surfaces by changing it through any means, then more heat will be retained.

Senator ALLARD. I think part of the problem that we are running

into here on the testimony is that we are not talking on the same

terms. I think that we have to be very careful when we review the

record and when we are listening to the witnesses here, Mr. Chairman, that we understand that we are all talking on the same terms

in making the same point. I think the committee gets confused

when we start talking from different terms and different perspectives.

I am just trying to simplify this argument down. I guess what

I am coming to is that, as I have stated earlier, it is easy for me

to believe that there is a trend in warming. The bottom line is

what is causing it and what is going to be the long-term effects

with this.

To me, the science is not entirely clear on that, and I do not see

that that is being entirely clear on this panel because when I asked

that question earlier, nobody gave me a specific on what they saw

the effects were going to be. Maybe Dr. Mann did, and said that

there was going to be warming. But most scientists when I talk to

them just won’t give me what they think the Earth is going to look

like 1,000 years from now, or they will not necessarily step right

out and say what are the causes of it because there are an awful

lot of variables. I am not sure that scientists understand all those

variables.

Dr. LEGATES. I think that is the issue. It is so uncertain and

there are so many things that go into the mix, that to say fairly

definitively it will be such in the future is very difficult to say.

Dr. SOON. We have to keep emphasizing that CO2 is not the only

player, the only factor. It is just highly short-sighted to just look

at CO2 as just one sole cause of change for every other change that

we see or any variations that we manage to record.

Senator ALLARD. Yes. And when we talk about greenhouse gases,

I think there is a tendency for us to think just in terms of CO2.
39

Dr. SOON. Right.

Senator ALLARD. But isn’t water vapor? Water vapor is a big part

of greenhouse gases.

Dr. SOON. That would be the area of expertise by Professor David

Legates. He studied that for almost 20 years.

Senator ALLARD. I do not know as we understand all of the aspects of each one of those fractionated, if we were to pull out each

CO2 or put out water vapor. What other gases do we have out

there? Those are the main ones.

Dr. MANN. The other two have commented. May I comment as

well?

Senator ALLARD. Let me finish my point. What are the greenhouse gases that we have?

Dr. MANN. I will speak to that.

Dr. SOON. Methane.

Senator ALLARD. Oh, methane. OK. We have methane. But the

main ones are water vapor and CO2. Water vapor being the largest,

right?

Dr. SOON. Yes.

Dr. MANN. Can I comment on that?

Senator ALLARD. Dr. Mann.

Dr. MANN. Yes. There are trace gases like methane, carbon dioxide, chlorofluorocarbons, which we can actually control.

Senator ALLARD. Well, carbon dioxide is a very small part of

greenhouse gases? Is that what you are saying?

Dr. MANN. No. There are several different greenhouse gases that

we have to keep in mind, and it would be short-sighted to only talk

about carbon dioxide. That is absolutely true.

Senator ALLARD. Right.

Dr. MANN. It is extremely misleading, however, when scientists

cite the role of water vapor as a greenhouse gas. The concentration

of water vapor in the atmosphere cannot be controlled by us directly, unlike the other trace gases. It is fixed by the surface temperature of the Earth itself. This is actually another chapter one

textbook-type of result that we know to be true in the scientific

community.

So we cannot change that freely. We can only change the other

trace gases. When we do change those, we warm the Earth. We

evaporate more water vapor and that gives us what we call a positive feedback that actually exaggerates the problem. But the water

vapor itself cannot be the source of the problem.

Dr. SOON. It is really also scientifically inaccurate to say that we

can really control CO2. The global carbon cycle—we do not understand it well enough to really match or account for the CO2 that

we emitted. How much of it is really going into the ocean? How

much of it has really gone into the forest? We do not have actually

a full control of those parameters, as Dr. Mann would like to state

on the record.

Senator ALLARD. Dr. Legates, do you have any comment?

Dr. LEGATES. Generally, the idea is that water vapor is the most

important greenhouse gas. Period. That is Chapter One of any introductory text. The issue is, then, if we are associating with the

effects of carbon dioxide and methane, which by the way has actually started to decrease over time, what we have found out is that
40

in particular we are dealing with with small matters where the

bigger issues are not controllable.

Again, the sun is the biggest game in town and it is not controllable. At least I do not know that we can turn off the sun or control

its output.

Senator ALLARD. OK. Senator Carper I think has a few questions.

Senator INHOFE. We have a serious problem here now, I am sorry

to say, and that is that we are 30 minutes past our first panel and

we are going to have to cut it off right now.

Senator ALLARD. OK, Mr. Chairman.

Senator INHOFE. I am very, very sorry. Thank you very much. I

appreciate the fact that you are here.

We would call our next panel up. I apologize to the next panel

because of the length of the first panel, we will have to cut this one

short.

Dr. Leonard Levin is the program manager, Electric Power Research Institute; Dr. Gary Myers, professor of neurology and pediatrics, University of Rochester Medical Center; and Dr. Deborah

Rice, the toxicologist, Maine Department of Environmental Protection, Bureau of Remediation and Waste Management.

I would like to ask each of you to confine your opening comments

to 5 minutes, if you would. Your entire statement will be made a

part of the record. We would start, Dr. Levin, with you.

STATEMENT OF LEONARD LEVIN, PROGRAM MANAGER,

ELECTRIC POWER RESEARCH INSTITUTE

Dr. LEVIN. Thank you, Mr. Chairman, members of the committee.

I am Dr. Leonard Levin. I have come to discuss recent findings

on mercury in the human environment. I serve as technical leader

at EPRI, which is a nonprofit collaborative research organization.

My remarks today represent my synthesis of research findings and

are not an official statement of EPRI position.

It is a privilege to provide the committee this testimony on the

science of mercury. I would like to address three key questions:

sources of mercury; its deposition from the atmosphere to the

Earth’s surface; its potential accumulation in fish.

Where does mercury in the U.S. environment originate? Mercury

is clearly a global issue. Recent estimates are that 2,340 tons of industry-related mercury are emitted globally. Over half of these

originated from Asian sources. Of the global total, the United

States is estimated to emit roughly 166 tons in total; U.S. utilities

about 46 tons. In addition, it is estimated that another 1,300 tons

of mercury emanates from land-based natural sources around the

globe, and another 1,100 or so tons comes from the world’s oceans.

Recent findings from the joint United States and Canadian

METAALICUS field experiment show that a fairly small amount of

deposited mercury, no more than 20 percent or so, re-admits to the

atmosphere, even over a 2-year period. The implications are that

mercury may be less mobile in the environment than we previously

thought.

Studies by EPRI have shown that much of the mercury depositing in the United States may originate on other continents. Model
41

results show that for three-quarters of the continental U.S. land

area, more than 60 percent of the mercury received comes from

outside the country. Only 8 percent of U.S. territory receives twothirds or more of its mercury from U.S. sources.

To check this with data, aircraft measurements were carried out

by EPRI and the National Center for Atmospheric Research in

Boulder, Colorado. Mercury and winds from the Shanghai, China

region were tracked over the Pacific for 400 miles toward the

United States. A second set of flights from Monterey, CA found

that same plume from China crossing the California coast and entering U.S. territory. One implication is that there may be a management floor for U.S. mercury, a level below which the amount of

mercury depositing to the surface cannot be reduced by domestic

action alone.

Second, what are the primary sources of mercury in fish in the

environment? Global mercury emissions appear to have peaked in

the 1980’s and declined or held steady since then. Professor Francois Morel of Princeton University, and colleagues, recently analyzed specific tuna for mercury, comparing recent catches with

those from the 1970’s. Despite changes in mercury emissions over

those 30 years, mercury levels in tuna did not change between the

samples. One conclusion they reached is that the mercury in such

marine fish is not coming from emission sources on land, but from

natural submarine sources of mercury. Again, this implies there

may be a management floor for mercury in marine fish, which

make up most of the U.S. fish diet.

Third, how can potential mercury reductions change mercury

deposition? EPRI recently completed work to assess what might

ensue in the atmosphere and in U.S. fish if further mercury emission reductions are carried out in the United States. The approach

linked models of atmospheric mercury chemistry and physics with

Federal data on mercury in fish in the U.S. diet, along with a

model of costs that would be needed to attain a given reduction

level. There are currently about 179 tons of mercury depositing

each year in the United States from all sources, global and domestic. Current U.S. utility emissions of mercury are about 46 tons per

year.

EPRI examined one proposed management scenario that cut

these utility emissions from 46 tons to 25 tons per year. The analysis showed that this emissions cut of 47 percent resulted in an average 3 percent decline in mercury deposition in the United States.

Some isolated locations making up less than one one-hundredth of

the U.S. land area experienced drops of up to 30 percent. The economic model showed that costs to attain these lower levels would

be between $2 billion and $5 billion per year for 12 years. This

demonstrated U.S. mercury patterns may be relatively insensitive

to the effects of this single category of sources.

In addition, most of the fish consumed in the United States are

ocean fish which would be only slightly impacted by a reduction of

24 tons of mercury per year solely in the United States, out of

2,300 tons globally. Wild freshwater fish within the United States

might show a greater reduction in mercury content, but they make

up a very small part of the U.S. diet, compared to ocean or farmraised fish.
42

These deposition changes were translated into how much less

mercury might enter the U.S. diet via these three categories of fish.

We found that less than one-tenth of 1 percent fewer children

would be born at-risk due to their mother’s taking in mercury at

lower levels from fish consumed in the diet.

So to summarize, a drop of nearly half in utility mercury emissions resulted in an average drop of 3 percent in mercury depositing to the ground, and a drop of less than one-tenth of a percent

in the number of children at risk. These recent findings are a small

part of the massive international research effort to understand

mercury and its impacts. EPRI and others, including U.S. EPA and

the Department of Energy, are jointly racing to clarify the complex

interactions of mercury with natural systems, an important part of

its cycling, and its impacts on human health. With improved understanding, informed decisions can be made on the best ways to

manage mercury.

Thank you for this opportunity to deliver these comments to the

committee.

Senator INHOFE. Thank you, Dr. Levin.

Dr. Rice.

STATEMENT OF DEBORAH C. RICE, TOXICOLOGIST, BUREAU

OF REMEDIATION AND WASTE MANAGEMENT, MAINE DEPARTMENT OF ENVIRONMENTAL PROTECTION

Dr. RICE. I would like to thank the committee for this opportunity to present information on the adverse health consequences

of exposure to methyl-mercury in the United States.

I am a neurotoxicologist who has worked on the neurotoxicity of

methyl-mercury for over two decades and have published over 100

papers on the neurotoxicity of environmental chemicals. Until 3

months ago, I was a senior toxicologist at the Environmental Protection Agency. I am a coauthor of the document that reviewed the

scientific evidence on the health effects of methyl-mercury for EPA.

This document included the derivation of the acceptable daily intake level for methyl-mercury.

I would like to focus on four points. No. 1, there is unequivocal

evidence that methyl-mercury harms the developing human brain.

No. 2, EPA used analyses of three large studies in its derivation

of an acceptable daily intake, including the studies in the

Seychelles Islands which found no adverse effects. No. 3, 8 percent

of women of childbearing age have levels of methyl-mercury in

their bodies above this acceptable level, and studies have documented cardiovascular disease in men at low levels of methyl-mercury, suggesting that an additional potentially large segment of the

population is at risk.

Studies performed around the world have documented harmful

effects of environmental methyl-mercury exposure on children’s

mental development. Three major studies were analyzed by the National Research Council panel in their expert review: In the Faroe

Islands in the North Atlantic, and the Seychelles Islands in the Indian Ocean, and in New Zealand. Two of these major studies, as

well as six smaller studies, identified impairment associated with

methyl-mercury exposure. The Seychelles Island study is anomalous in finding no effects. Adverse effects include decreased IQ and
43

deficits in memory, language processing, attention and fine motor

coordination.

The NRC modeled the relationship between the amount of methyl-mercury in the mother’s body and the performance of the child,

and calculated the level associated with the doubling of the number

of children that would perform in the abnormally low range. The

NRC panel did this for each study separately and for all of the

three studies combined, including the negative Seychelles study.

EPA used the NRC analyses in deriving its acceptable daily intake level of methyl-mercury. EPA performed the relevant calculations based on each of the two positive studies, as well as the integrative analysis of all three studies. The acceptable level is the

same whether it is based on the integrative analysis of all three

studies, or on the Faroe Islands study alone.

The acceptable level would be lower if only the New Zealand

study were considered. Only if the negative Seychelles study alone

were used, while ignoring the values calculated for the Faroe Islands and New Zealand studies, would the acceptable intake level

be higher than the current value. EPA believed that to do so would

be scientifically unsound and would provide insufficient protection

to Americans.

Data from a survey representing the U.S. population collected

over the last 2 years revealed that about 8 percent of women of

childbearing age had blood concentration of methyl-mercury above

the level that EPA believes is safe. This translates into over

300,000 newborns at risk for adverse effects on intelligence and

memory, ability to pay attention, language skills and other abilities

that are required to be successful in our highly technological society.

There is an additional concern regarding the potential for harm

as a result of environmental methyl-mercury exposure. Three studies found a relationship between increased methyl-mercury levels

and atherosclerosis, heart attacks and death, and it is unknown

whether there is a level of mercury that will not produce harm. It

is important to understand that the cardiovascular effects associated with methyl-mercury may put an additional very large portion

of the population at risk.

In summary, there are four points that I would like the committee to keep in mind. First, at least eight studies based on populations around the globe found an association between methyl-mercury levels and impaired neuropsychological function in children.

The Seychelles Islands study is anomalous in finding no effects.

Second, both the NRC and the EPA included the Seychelles Islands

study in their analysis. The only way that the acceptable intake of

methyl-mercury could be higher would be to ignore the two major

positive studies, as well as six smaller studies and rely solely on

the one study that showed no effects.

Third, there is a substantial percentage of women of reproductive

age in the United States with levels of methyl-mercury in their

bodies above what EPA considers safe. As a result, over 300,000

newborns each year are exposed to potentially harmful levels of

methyl-mercury. Fourth, increased exposure to methyl-mercury

may result in cardiovascular disease and even death in men from
44

heart attack, suggesting an additional large segment of the population is at risk.

Additional information has been provided to the committee.

Thank you for your time and attention.

Senator INHOFE. Thank you, Dr. Rice.

Dr. Myers.

STATEMENT OF GARY MYERS, PROFESSOR OF NEUROLOGY

AND PEDIATRICS, DEPARTMENT OF NEUROLOGY, UNIVERSITY OF ROCHESTER MEDICAL CENTER

Dr. MYERS. Thank you for the opportunity to present the views

of our research group on the health effects of methyl-mercury exposure. My name is Gary Myers. I am a pediatric neurologist and a

professor at the University of Rochester in New York, and just one

member of a large international team that has been studying the

human health effects of methyl-mercury for nearly 30 years. For 20

of those years, our group has specifically studied the effects of prenatal methyl-mercury exposure.

In 1971 and 1972, there was an epidemic of methyl-mercury poisoning in Iraq. The source of exposure, unlike in Japan, was maternal consumption of sea grain coated with a methyl-mercury fungicide. We looked at a number of children in that study and measured the exposure of the fetus using the maternal hair as the biomarker. It is the only biomarker that has been correlated with

brain levels. We concluded that there was a possibility that exposure as low as 10 parts per million in maternal hair might be associated with adverse effects on the fetus. This value is over 10 times

the average in the United States and five times the average in

Japan, but individuals consuming large quantities of fish can easily

achieve this level.

The hypothesis of our study in the Seychelles was that methylmercury from fish consumption might affect child development. In

fact, we all thought it would. Since millions of people around the

world consume fish as their primary source of protein, we thought

it was only reasonable to investigate the question directly. We selected the Seychelles because of two reasons. First, they eat large

amounts of fish. The average mother eats 10 times as much as

women here in the United States.

Second, the fish in Seychelles has an average mercury content of

about 0.3 parts per million, which is approximately the same as

commercial fish here in the United States. The Seychelles study is

a collaborative study which was begun under the auspices of the

WHO and has been carried out by a U.S.-led team of international

researchers from the University of Rochester, Cornell University

and the Ministries of Health and Education in Seychelles. The

funding has come from the National Institutes of Environmental

Health Sciences, with some minor funding from the Food and Drug

Administration and the governments of Seychelles and Sweden.

The Seychelles was chosen for a number of reasons, primarily because there was no overt mercury pollution and many of the factors

that complicate epidemiological studies of low-level exposures were

simply not present. There was universal free and readily available

health care in Seychelles. Prenatal care is nearly 100 percent. The

birthrate is high and the general health of the mothers and chil-
45

dren is very good. In addition, education is free, universal, and it

starts at age 31⁄2.

Before starting the study, we carefully controlled for a number

of things. To minimize the possibility of bias, a number of decisions

were made. First, no one in Seychelles, including any of the researchers who visit the island, would know the level of exposure of

any child or mother unless our results indicated that children were

indeed at risk. Second, because of the known problems with developmental delay in certain disorders, those children would be excluded from the study. Third, the tests administered would include

all of the tests that have been used in other studies, plus other

things that we thought might detect subtle changes.

Fourth, we would do this testing at specific age windows. Fifth,

we would adjust for multiple confounding factors, things that are

actually known to affect child development such as socioeconomic

status, the mother’s intelligence, and birth weight. And sixth, we

established a data analysis plan before the data were collected to

minimize the possibility that the data would just be repeatedly

analyzed until the anticipated effect was in fact determined.

We have now carried out five evaluations of the children over 9

years. The study has focused on prenatal exposure. The exposure

of both mothers and children has been in the range of concern,

from 1 to 27 parts per million. We have done extensive testing with

over 57 primary endpoints determined so far. The study has found

three statistical associations with prenatal methyl-mercury exposure. One was adverse; one was beneficial; and one was indeterminate. These results might be expected to occur by chance and do

not support the hypothesis that adverse developmental effects result from prenatal methyl-mercury exposure in the range commonly achieved by consuming large amounts of fish.

The findings from our research have been published in the

world’s leading medical journals, including the Journal of the

American Medical Association, the Lancet, and a soon-to-be-published review in the New England Journal of Medicine. We do not

believe that there is presently good scientific evidence that moderate fish consumption is harmful to the fetus. In the words of Dr.

Lyketsos, a distinguished researcher from Johns Hopkins, who

wrote the editorial with our Lancet articles:

‘‘On balance, the evidence suggests that methyl-mercury exposure from fish

consumption during pregnancy of the levels seen in most parts of the world does

not have measurable cognitive or behavioral effects in later childhood. However,

fish is an important source of protein in many countries and large numbers of

mothers around the world rely on fish for proper nutrition. Good maternal nutrition is essential to the baby’s health.’’

Thank you.

Senator INHOFE. Thank you, Dr. Myers.

We are going to try to adhere to a 5-minute round of questioning.

Let me just share with you, which I think you already know, you

folks are looking at the medical effects of mercury. We also up here

have to consider the economic effects—the problems that are out

there. Right now on the Senate floor, they are debating the energy

bill. We have an energy crisis in this country, and if cofire should

go out, and that could happen from either CO2 or mercury, it would

be a very serious crisis. I think anticipating that this will happen,
46

several people have moved off-shore, moved to other places. So that

is something that is really, I guess you would say our major, at

least one of my major concerns.

Now, just for all of the witnesses, you stated that the U.S. utility

mercury emissions are 46 tons a year. Tell us what happens to this

mercury. Help us visualize where does it come from; where does it

go; how much is deposited in the United States; how does this compare with the amount that is deposited in the United States from

global sources.

Would you like to start, Dr. Rice?

Dr. RICE. That is really not my area of expertise, so I cannot

speak to it.

Senator INHOFE. All right.

Dr. Myers.

Dr. MYERS. It is not my area of expertise.

Senator INHOFE. Come on, Dr. Levin.

Dr. LEVIN. All right.

[Laughter.]

Dr. LEVIN. Utility mercury of the various sources of mercury is

probably the best-studied category, partially because there are

more individual sources than there are of many of the other categories. We believe that roughly half on average coming out from

utilities is made up of the divalent form of mercury, which is about

a million times or so more soluble in water than the elemental

form, which is the silvery liquid that you probably remember from

high school chemistry. So of this mercury emitting from all utilities

in the United States, roughly half of it is more highly water soluble

and the other half will tend to go into regional and global circulation.

We calculate that about 70 percent or so of the mercury emitted

from utilities leaves the United States, and the other 30 percent or

so deposits within the United States across the country. These are

somewhat similar to the numbers that EPA is deriving as well.

Some of this mercury that deposits to the surface will wind up in

receiving waters, and a very small fraction of it, probably less than

1 percent, will eventually be turned into the organic form by bacterial action. It is that organic form that has the potential to reach

humans through accumulation in some fish.

Again this does not happen in all waterways and with all fish

species. It tends to happen in waterways that have full food webs

that go to high-level fish that grow quite large, and it is larger,

older fish that tend to accumulate more mercury.

Of the exposure in the community in the United States, almost

all of it is through intake from fish and the mercury in those fish,

although the levels taken in can vary from very little or almost

none, to amounts of concern. There is almost no exposure by inhalation. That is a very small part of the exposure.

So our concern is to follow this mercury from its sources through

to where it winds up in fish and eventually may be consumed by

humans. That is the trick, scientifically.

Senator INHOFE. Thank you, Dr. Levin.

Dr. Rice, the American Heart Association and the World Health

Organization recommend that fish should be a part of everyone’s

diet, concluding that the benefits of eating fish outweigh the risks
47

of adverse effects, which as you state in your testimony are potential risks. Since eating fish offers substantial health benefits,

shouldn’t the EPA’s referenced dose be revised to take this into account, or does it?

Dr. RICE. Well, I agree totally, and I have to say that I am no

longer with EPA so I am not speaking as a representative of the

agency. I need to make that clear. So some of these opinions will

be those of the agency when I left, and some will be mine.

But the scientific community at large and the EPA and me personally recognize that fish is a good source of protein. It also confers cardio-protective effects. There are also omega-three fatty acids

in fish that are essential when the fetus is building its brain. There

is new evidence that eating fish also may be beneficial to the mental development or the mental function of the elderly. I suspect

that it is probably important for all of us.

So the dichotomy is not eat fish/don’t eat fish. The important

thing to be able to do is to come out with some recommendations

to the community that allow people to eat fish, but not to eat fish

that has increased levels of methyl-mercury. So EPA thinks that,

I was part of that EPA panel, so when I was part of that EPA

panel we firmly believe that the RFD should not be any higher,

and in the light of some evidence that we were not able to analyze

at the time, might even should be lower than it is presently.

So it is not a question of increasing the reference dose. It is a

question of making sure that the American public can eat fish that

does not have undue levels of methyl-mercury in them.

Senator INHOFE. Thank you very much.

Dr. Myers, in selecting the Seychelles as a location for your research, what other locations did you consider other than the

Seychelles Islands?

Dr. MYERS. We started studies on the coast of South America

and looked also at the Maldive Islands as another possibility.

Senator INHOFE. Yes. I kind of wanted to get to the Faroe Islands. Did you consider them for your research?

Dr. MYERS. We did not consider the Faroes in our research.

Senator INHOFE. It is my understanding that, and for those of us

who are not scientists here, that some of the problems, let’s take

the Faroe Islands and see if I have this right, that there is an inordinate amount of whale meat that is consumed there and there are

PCBs in there. I do not know whether you can distinguish between

the harm of one or the other, but is this a factor that should be

considered?

It is my understanding, and I won’t say this right, but there are

different levels of mercury that are found. One is from the primary

fish, and the other is from whales that eat other fish, so it has a

multiplying effect. Is this taken into consideration?

Dr. RICE. The Faroe Islands study and the Seychelles Islands together have been reviewed by at least two very distinguished peerreview panels. That issue, the issue of the pattern of intake of

methyl-mercury and potential co-exposure for PCBs has been discussed extensively by the scientific community.

The Faroe Islands’ population does eat whale meat. They may

eat a large whale dinner occasionally. They also tend to dry the

whale meat, and so they snack on it in addition to eating a so-
48

called bolus dose, what we call a bolus dose. So they have a low

level of methyl-mercury intake which may be occasionally punctuated with a higher intake level. The source of methyl-mercury

does not matter, whether it is through fish or through whale. So

the fact that it is whale meat per se is not really relevant.

None of the panels, including the National Research Council

panel, could come to any kind of conclusion about the importance

of the pattern of intake, because the data just are not available.

There just are not scientific data that speak directly to that. But

what the Faroe Islands investigators have done because this was

raised as a concern and because they have hair, and they had hair

from their population that was stored, they were able to go back

and do segmental analysis, so that you cut the hair up into tiny

little pieces and look at mercury levels across the length of the

hair.

What they did was they eliminated the mothers that had the

most variable hair levels that might suggest that there was this

bolus exposure of these particular women and these particular

fetuses. What they found was that the effect was actually stronger

when they eliminated these women, which makes a certain amount

of sense because you are decreasing variability when you do that.

Senator INHOFE. Thank you, Dr. Rice.

Senator Jeffords.

Senator JEFFORDS. Thank you all for your testimony on this very

important and timely topic.

Some of you have seen this morning’s New York Times full-page

article on mercury and its health effects. This helps to set a context

for our discussion.

Dr. Rice, what exactly is a reference dose level and what does it

mean in terms of the so-called safe levels of fish consumption? Does

EPA reference dose level include a built-in tenfold safety threshold?

Dr. RICE. The reference dose is designed to be a daily intake

level that a person could consume over the course of their lifetime

without deleterious effects. So it is designed to be the amount of

mercury you could eat every day in your life and not harm yourself.

Now, when EPA did its calculation, it is important to understand

that when the National Academy of Sciences modeled a number of

endpoints for each of the studies, and those were the Faroe Islands

study, the New Zealand Study, both of which found effects, as well

as the Seychelles study which did not, they identified not a no-effect level. They identified a very specific effect level. That effect

level is associated with a doubling of the number of children that

would perform in the abnormal range, in other words, the lowest

5 percent of the population. So this is in no way a no-effect level.

To that, the EPA applied a tenfold so-called uncertainty factor.

The point of that was to take into account things that we did not

know, data that we did not have, as well as the pharmacodynamic

and the pharmacokinetic variability. Now, there were actually data

that was again modeled by the NAS and reviewed by the NAS, that

says that the pharmacokinetic variability, in other words the woman’s ability to get rid of methyl-mercury from her body, differs by

a factor of three. So that already takes up half of the uncertainty

factor.
49

But in addition to that, it is important to understand that when

the Faroe Islands folks analyzed their data, they eliminated mothers with mercury levels above 10 ppm in their hair, which was

really right about at the effect level that the NAS identified. The

effects were just about as strong even below 10 ppms. So again,

that is very strong evidence that there is not a factor of 10 safety.

In addition to that, when the NAS modeled their data, it turned

out that both of the New Zealand study and the Faroe Islands

study not only was there no evidence that there was a threshold,

in other words a level below which there were no effects, but in fact

the curve was actually steeper at the lower levels. The NAS used

a straight line when they modeled the data because they were uncomfortable about using curves that were steeper at the lower end

than they were at the higher end, but subsequent to that there

have been studies come out with regard to lead exposure, for example. There are now several studies where that has also been found

for lead exposure.

So this may in fact be a very real effect. So not only is there not

a safety factor of 10. There might be virtually no safety factor at

all.

In addition to that, something that EPA recognized at the time,

but we were not able to quantitate because we did not have the

data, but it has now been quantitated, we assumed that the relationship between the mother’s blood level of methyl-mercury and

the fetus’ blood level of methyl-mercury were the same, because of

course we have the body burden; we have cord blood in the fetus,

we have to get back to intake by the mother. We know now that

in fact the ratio is more like 1.7, and for some mothers it is as

much as over 3.

So if we were to recalculate the reference dose just based on this

new information, it would decrease from 0.1 to 0.06.

Senator JEFFORDS. Dr. Rice and Dr. Myers, would you recommend that Members of Congress and regulatory agencies base

their decisions on whether and how much to reduce human-made

mercury emissions on the findings from any one study?

Dr. MYERS. Our group has been involved in the science of studying whether you could find effects at low levels, and we have not

been involved in policy. There is a general scientific principle, I

think it is important to look at multiple different studies. However,

these studies are complicated and one has to look at what kind of

studies you are dealing with. Some are simply descriptive. They

take a group of people and describe something. It is a basic epidemiological principle that you cannot assign causation from a descriptive study.

So one has to look at the studies that are larger and follow children over time, and control for a lot of confounding factors which

complicate these type of studies very much actually. The Seychelles

study in fact is not a negative study, as has been stated. We did,

in fact, find associations with things that are known to affect child

development, such as socioeconomic status, maternal intelligence,

the home environment and other things. What we did not find was

an adverse association with prenatal methyl-mercury exposure in

the Seychelles.

Senator JEFFORDS. Dr. Rice.
50

Dr. RICE. I agree with Dr. Myers. These studies are very complex. I think that that is even more reason not to rely on one study

while eliminating other studies for consideration.

Again, these studies have been peer-reviewed numerous times.

The Seychelles Islands study and the Faroe Islands study have

been reviewed now by several panels. They are both thought to be

very high quality, very well-designed and well-executed studies.

The NAS, as well as the previous panel, talked at great length

about what might account for the differences between these studies. We really do not know what accounts for the differences between these studies. The NAS modeled three studies. The New

Zealand study was also a positive study.

The National Academy of Sciences and the EPA agreed with

them that it was not scientifically justifiable for protection of the

health of the American public to rely on the negative study and exclude the two positive studies. I said at least a couple of times in

my testimony that what the NAS did to try to address that was

to do an integrative analysis that included all three studies, including the Seychelles Islands study, and modeled it statistically.

When EPA then took those analyses and derived, what we did

was we derived a series of reference doses, kind of sample reference

doses, that were based on a number of endpoints from both the

New Zealand study and the Faroe study, as well as the integrative

analysis of all three studies. The integrative analysis of all three

studies also yields a reference dose of 0.1. So that made me personally very comfortable that we were doing the right thing scientifically in our derivation of the reference dose.

Senator INHOFE. These are supposed to be 5-minute rounds and

it has been 8 minutes, so we will recognize Senator Allard.

Senator ALLARD. Dr. Rice and Dr. Myers, you have in your comments talked about methyl-mercury as being the toxic compound as

far as human health is concerned. Are there other mercurial compounds that are toxic to humans?

Dr. RICE. Yes. All forms of mercury are toxic to humans.

Senator ALLARD. Including the elemental form?

Dr. RICE. Yes.

Senator ALLARD. OK.

Dr. RICE. But in terms of environmental exposure, it is really the

methyl-mercury form that we are worried about because that is the

form that gets into the food chain and is concentrated and accumulated up the food chain. That is what people actually end up being

exposed to.

Senator ALLARD. OK. Thanks for clarifying that. I appreciate

that. So this gets into the environment and consequently in the fish

or food chain or whatever. Is the starting point always bacteria operating on the elemental form of mercury? Or is it these various

compounds that bacteria operate on and then end up being assimilated into the food chain? How does that happen?

Dr. RICE. In most circumstances, it is the inorganic form, not the

elemental mercury, but the inorganic form that is available to be

taken up by various microorganisms.

Senator ALLARD. How do we get to that organic form, the methylmercury? How do we get there?
51

Dr. RICE. The microorganisms actually put a methyl group on as

part of their metabolic processes.

Senator ALLARD. Do they get that from elementary mercury? Is

that the origin, or is it various compounds of mercury?

Dr. RICE. Yes, it is just straight mercury. Now, in the Japanese

outbreak, it was actually methyl-mercury that was put into the

water, but that is a relatively unusual situation.

Senator ALLARD. I see. OK, so my understanding, Dr. Levin, is

that a lot of the mercury that is introduced into the environment

of this country does not originate within the borders of this country. Is that correct? The suggestion is that a lot of the sources of

mercury that come across that we may pick up in the soil is actually carried over by wind and what not from the Asian countries.

Is that correct?

Dr. LEVIN. That is correct, Senator, as far as the modeling shows,

and that is consistent with work that EPRI has done, EPA and others have also done in the modeling.

Senator ALLARD. Is this the elemental mercury that is being

brought over?

Dr. LEVIN. It is elemental, or the elemental form. It is also the

inorganic form or the form that can be combined into salts.

Senator ALLARD. Now, the inorganic form is not processed into

the food chain? Did I understand that correctly?

Dr. LEVIN. It is the inorganic form that is processed into the food

chain.

Senator ALLARD. Yes, it is the organic form.

Dr. LEVIN. The two forms that are emitted from combustion

sources are the elemental form, the chemicals found on the periodic

chart.

Senator ALLARD. Right.

Dr. LEVIN. And the inorganic form, which combines with, for example, chlorine, to form the pure chloride, or is the form also found

in minerals. Those two forms that wind up in the proper aquatic

environments, it is the inorganic form that may be methylated and

turned into the organic form.

Senator ALLARD. Right.

Dr. LEVIN. But it has to go from elemental to inorganic before

the methylation can occur.

Senator ALLARD. But my question is, is that the type of mercury

that is being brought in from Asia, what form of mercury is that?

Dr. LEVIN. Because of its long-range transport, it is primarily the

elemental form, but the atmospheric chemistry of mercury changes

that progressively into the inorganic form, which is the form that

readily deploys.

Senator ALLARD. Now, can the inorganic form be transferred into

methyl-mercury?

Dr. LEVIN. Yes, sir. That is the form.

Senator ALLARD. So all those type of compounds get acted on by

bacteria and then that is how that gets into the food chain.

Dr. RICE. The elemental form and the inorganic form are converted back and forth.

Senator ALLARD. I see.

Dr. RICE. So it does not make any difference whether it reaches

the North American shores as elemental mercury or inorganic mer-
52

cury. Once it is deposited into the soil or the river, it is going to

become inorganic mercury that then becomes available to be able

to be turned into methyl-mercury.

Senator ALLARD. OK, thank you.

Now, here is the question, and I would like to have all of you respond to this. In your opinion, would a decrease in U.S. anthropogenic mercury emissions have an effect on global mercury levels?

And part of the rest of the question is, apparently there is a high

percentage of mercury present in the United States from outside

our borders, so what effects can we expect from a decrease in our

emissions? We have a couple of questions there and I would like

to have all of you respond to those if you would.

Dr. RICE. There is no question that there is a global cycling of

mercury. A lot of the mercury in the United States comes in from

someplace else, comes in from the West, but some of it may have

in fact originated in the United States originally. This stuff really

does circle the globe. So just because it is coming in from the West

does not mean it wasn’t ours to start with.

Senator ALLARD. We do not know how much starts here.

Dr. RICE. No, we do not, and I am not a modeler so I really cannot speak to that. But what I do know is that there is local deposition. In other words, the mercury that is released from power

plants in the Midwest ends up downwind. I just moved to Maine,

and Maine is the so-called tailpipe for that local deposition, for that

local emission. There is a percentage of it, and Dr. Levin can tell

you what the percentage is better than I can, that is locally deposited. I think it is something like 30 percent.

Getting rid of those local sources would certainly at least help

the Northeastern United States. Originally, the modeling, it was

thought that this would take a long, long time. There are newer

data now where small studies have actually been done that suggest

that it might not be as grim as we originally thought; that these

local changes can take place in a relatively shorter time, over the

course of several years, rather than decades and decades as we

originally may have feared.

Senator ALLARD. Dr. Myers, do you have a comment on that?

Dr. MYERS. It is outside of my area of expertise.

Senator ALLARD. Dr. Levin.

Dr. LEVIN. Dr. Rice is primarily correct on that. The deposition

within the United States makes up about 30 percent of U.S. emissions. The rest of the emission go globally. Our modeling considered the fate of U.S. emissions and accounted for the amount that

basically circles the globe and comes down after one trip around

the world.

It is also correct that there is local deposition that in some cases

may be significant near particular groupings of sources. I indicated

that in my testimony, that although the average change in deposition for the scenario was 3 percent, there were some small areas

where it was as much as 10 times that on a percentage basis.

So it calls for more detailed studies and particularly more looking at the science of tracking mercury found in fish back to its

sources scientifically, that is, figuring out where it came from.

Senator ALLARD. Thank you, Mr. Chairman. I believe my time

has expired.
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Senator INHOFE. Yes, thank you.

Senator Carper.

Senator CARPER. Thank you, Mr. Chairman.

To our witnesses, again thank you for joining us. Thank you for

your patience in bearing with us.

Dr. Rice, did I understand you to say you have concluded two

decades of work at EPA?

Dr. RICE. Well actually most of it was not at EPA. I was at

Health Canada for 22 years. I am American, but I graduated from

the University of Rochester, got my Ph.D. from the University of

Rochester so I have known Dr. Myers for many years. Then I went

up there to work at Health Canada.

Senator CARPER. I see. Thank you for your service at EPA, and

thank you all for real interesting testimony today.

Sometimes these are fairly technical issues. What is helpful for

me as I listen to the comments of each of your testimonies and your

responses to our questions is to look for threads of consensus; not

to focus so much on where you disagree, but to find some areas

where you agree. I would just ask each of you to take a minute or

two and just to talk about some of the areas where you think you

agree, and which might be helpful to us as we wrestle with whether to craft legislation, enact legislation along the lines that Senator

Jeffords has introduced, I have introduced, or the President has

proposed.

Can you help me with that? Dr. Levin, why don’t you go first.

Dr. LEVIN. Thank you, Senator. We agree that mercury is a highly toxic compound. Its presence in the U.S. diet may in some instances cause concerns for development of children neurologically.

We agree that there may be other effects that have to be looked

for in terms of the health effects.

We also agree that the science of mercury is still emerging; that

the linkage between health effects in particular areas, or for that

matter in entire regions of the United States, and the sources of

mercury is a critical question that would shape a wise course toward management decisionmaking. The work that I have been describing today is a step in doing that. The work that has been described by the other two witnesses today on health effects is a critical part of that linkage.

Bringing this source-receptor issue together with the health effects on a specific geographic basis and among specific populations

within the United States is a key part in answering the management questions.

Senator CARPER. Thank you.

Dr. Myers, would you take a shot at my question please?

Dr. MYERS. I think we all agree that mercury is poisonous, every

form. In high enough amounts, it is not only damaging to human

health, but fatal generally. We all agree that it is worthwhile

cleaning up the environment, I think. The question resolves at

what level and at what cost. I think we all agree that these studies

are extremely difficult to carry out and they are equally difficult to

interpret because there are so many details to them. So it is so

easy to end up with a bias either knowingly or unknowingly, generally I think unknowingly, that the interpretation of the details

becomes incredibly important in these studies.
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Senator CARPER. Thank you.

Dr. Rice.

Dr. RICE. I agree that we all know that methyl-mercury is toxic

at high levels. There is absolutely no question about that. I agree

with Dr. Myers that it is incredibly difficult to interpret these studies very often. They are very complex studies. There are a lot of

variables, many of which we do not know. Epidemiology is an extremely blunt instrument. So that is why I think that it is important to look at the weight of evidence. There are a number of studies in humans that have documented effects of methyl-mercury at

relatively low body burdens. In addition to that, there is a huge

animal literature documenting effects and looking at the mechanisms of effects.

We do not know why one study may be positive, whereas another

may be negative. So we really have to go with the evidence as a

whole.

Senator CARPER. And maybe cite your most serious area of disagreement among you as panelists.

Dr. LEVIN. I would say disagreement probably rests in the question of the direction of research overall on the mercury issue, and

how far that should continue.

Senator CARPER. Dr. Myers.

Dr. MYERS. I think the most serious area of disagreement is in

the interpretation of the studies. We think that the Faroe Islands

research is outstanding research. They have done a wonderful job.

They have a great design. We are just not sure that they have been

able to tease out from the mixture of chemicals present in whales

a methyl-mercury component to it. That requires a lot of faith in

their statistics and the details of the studies.

In the case of the New Zealand study, most people discounted the

New Zealand study for many years. It was only when it was reanalyzed in the late 1990’s that people began to start thinking of it in

other terms. So I think our biggest disagreement is in the interpretation of it.

In addition, I think the weight of hundreds of small poorly done

studies in difficult places such as the Amazon would never outweigh a really good study done looking at fish consumption.

Senator CARPER. Dr. Rice.

Dr. RICE. I guess everything that Gary Myers just said is my biggest point of disagreement. All of the smaller studies are not poorly

done. Some of them are well done. The Faroe Islands study and the

Seychelles study have been extensively reviewed. They are both

considered to be very, very good studies.

The National Academy of Sciences looked at the issue of PCB coexposure very, very carefully and asked the investigators to go

back and do a number of additional analyses. Their conclusion was

that the effects seem to be independent of each other. These are

both neurotoxicants. Although they both had effects in the study,

the NAS conclusion was that they were independent.

Again, I think that we have go with a preponderance of evidence

and not on just one study, no matter how well it has been done.

Senator CARPER. Mr. Chairman, I think this panel has been especially helpful to me. We thank you very, very much for your contributions today. Thank you.
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Senator INHOFE. Thank you, Senator Carper.

Senator Clinton.

Senator CLINTON. Thank you, Mr. Chairman. I, too, want to

thank the panel and welcome Dr. Myers from the University of

Rochester, and Dr. Rice, your connection with Rochester, we will

claim that as well.

I want to pick up where Dr. Rice just concluded. We have set up

a system of evidence in our legal system that looks at the preponderance of evidence; that looks at a reasonable person standard. I

share Dr. Rice’s concern that we are not adequately responding to

the evidence we already have, which I think the preponderance of

it, certainly based on the review by the National Academy of

Sciences, suggests that we have a problem with the transmission

mostly in utero by mother to child that leads to neurological problems that in turn lead to poor school performance.

The 2000 report of the National Academy of Sciences found, I believe, that about 60,000 children might be born in the United

States each year with this level of exposure that could affect school

performance, but in your testimony you claim that more recent results from the CDC’s National Health and Nutrition Examination

Survey translate into over 300,000 newborns per year. Is that correct?

Dr. RICE. Yes. When the NAS did their analysis, the NHANES

data was not available. The NHANES just started taking mercury

blood and hair levels a couple of years ago, so those data have really become available since the NAS. They state that their 60,000

children was an estimate. It is actually about 320,000 children.

Based on actual data that is representative of the U.S. population,

it is above the EPA’s reference dose.

Senator CLINTON. To me, this is truly alarming, that we have actual blood, hair sample, other kinds of physical examination which

demonstrates that hundreds of thousands of our children are born

each year potentially at risk for adverse affects on intelligence,

memory, ability to pay attention, ability to use language and other

skills.

Mr. Chairman, we are facing an increasing number of children

in our school systems with learning disabilities. There are not any

easy answers as to why the numbers of children with such learning

disabilities has increased. Senator Jeffords has been a champion of

making sure that all children are given an adequate education. In

New York alone, we have 260,000 learning-disabled children. That

is 50 percent of our special ed population. We spend $43 billion

each year—$43 billion—on special ed programs for individuals with

developmental disabilities between three and twenty-one.

Of course, not all special ed needs are the direct result of methylmercury exposure, but if it is demonstrably shown as we now have

with evidence from the CDC’s annual survey that we have levels

of methyl-mercury in our children’s bodies that is above what the

EPA has determined to be healthy, and in fact some of us think

the EPA standard is too low, but nevertheless if it meets that

standard, then I would argue we have got to figure out how to address this environmental health challenge in a very short order.

I have been working with a number of colleagues to try to address the better data collection and environmental health tracking
56

that they need in the Individuals With Disabilities Act, and I think

similarly on the scientific side with respect to better research and

better analysis. But it is troubling to me that we are looking at a

problem where the preponderance of the evidence I think is clear,

where we know that there is a transmission, whether it is 60,000,

150,000, 300,000-plus children, and it needs some more effective response.

I wanted to ask you, Dr. Rice, now that you are in Maine, from

the State perspective, how closely do you work with the State

health department on environmental health issues? Do you exchange information with the State health department and even

with the State education department about some of the work that

you are doing?

Dr. RICE. I actually knew the State toxicologist for Maine quite

well before I went up there, so I do interact with the health department. The methyl-mercury issue is very important to Maine. Maine

has a very good program for trying to get rid of methyl-mercury

from dental amalgams, from thermometers, from the kinds of

things that can be controlled; to not put mercury in landfills because Maine understands that we are at the end of the pipeline for

methyl-mercury deposition. Maine has a terrible problem with fish

advisories. There are a lot of places where fish cannot be eaten in

Maine because of the deposition of methyl-mercury.

So I do work closely with the folks over there, and in fact my way

here was paid by the air office, the Maine air office because the

State of Maine is so very concerned about this issue. Maine is rural

and it is poor, and it cannot really absorb the consequences of these

kinds of additional exposures on the health of the people of Maine.

Senator CLINTON. Similarly, new science is demonstrating that

we need lower standards for lead, based on what we are now determining. A lot of that groundbreaking work was done at the University of Rochester about lead exposures and the impacts of lead exposure. We can take each of these chemicals or compounds piece

by piece, but I think that certainly when it comes to mercury and

lead and their impacts on children’s development, it is not something I feel comfortable studying and waiting too much longer on,

particularly because there are so many indirect costs. I know that

Dr. Levin’s work looked at some of the risks and cost-benefits, but

people do not seem to factor in this special education population

that has been growing.

Dr. RICE. If I may make a comment, I think your analogy is an

apt one, and I think it is a very informative one. In 1985, there was

a report to Congress on the cost-benefits of lead, of keeping lead

out of gasoline, in fact. The benefits based on not only special education and things like lower birth weight with respect to lead, but

also just the economic consequences of lowering the IQ of workers

amounted to billions and billions of dollars a year in 1985 dollars

or 1994 dollars. So as this effort goes forward in terms of figuring

out how much it is going to cost to reduce mercury emissions, this

other side of the equation, how much it is going to cost not to,

needs to be kept very, very well in mind.

Senator CLINTON. Thank you, Dr. Rice.

Senator INHOFE. Thank you, Senator Clinton.

I thank the panel very much for their testimony.
57

Senator JEFFORDS. I had a couple more questions.

Senator INHOFE. Well, all right. It has to end at 12 o’clock. Go

ahead.

Senator JEFFORDS. Dr. Levin, before setting a mercury max

standard, would you agree that it makes sense for EPA to conduct

a full modeling analysis of all available technology options and

their emissions reduction potential, including the most stringent

options?

Dr. LEVIN. Yes, Senator. I think it is important for EPA to carry

out a parallel study as EPRI has done, and to make that study

public, as we have as well. I am not aware yet that they have actually done any modeling of a max standard since there has been no

official proposal of one yet.

Senator JEFFORDS. Dr. Myers, I believe your testimony is that

the fish consumed with an average mercury content of 0.3 parts

per million has about the same mercury concentration as commercial fish in the United States. What are the concentration in noncommercial fish?

Dr. MYERS. Are you talking about the United States or the

Seychelles?

Senator JEFFORDS. In the United States.

Dr. MYERS. Well, all fish has some mercury in it. Most of the

commercial fish in the United States, I understand, has less than

1⁄2 part per million, but some of the fish, I am not sure what the

non-commercial ones are, but it can go up to over two or three

parts per million in some freshwater fish.

Senator JEFFORDS. Dr. Rice and Dr. Myers, can you characterize

the body burden of the pollutants like mercury in American children compared to the levels found in the Seychelles children?

Dr. MYERS. The average hair level in the mothers in Seychelles

is 6.9 in the group we were studying. The average in the United

States is less than one part per million. The average in Japan is

somewhere around two parts per million.

Senator JEFFORDS. Dr. Rice, any comment?

Dr. RICE. No. That is correct, but I think it is important to understand that the NHANES data did identify some women, a very

small percentage of women with higher hair mercury levels. I think

it is important also to understand that the NHANES data are designed to be representative of the U.S. population as a whole, so

that women who may eat more fish and may be at more risk for

increased body burdens of methyl-mercury, such as immigrant populations or populations of people who are subsistence anglers and

who eat inland fish. This is not captured. These populations are not

captured by the NHANES data and I think that this needs to be

kept in mind.

Senator JEFFORDS. I have some further questions I would like to

submit.

Senator INHOFE. That would be perfectly appropriate. I appreciate it very much, and I appreciate the panel coming and also your

patience from the long first session.

We are now adjourned.

[Whereupon, at 12 o’clock p.m. the committee was adjourned, to

reconvene at the call of the chair.]

[Additional statements submitted for the record follow:]
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STATEMENT OF HON. JON CORNYN, U.S. SENATOR FROM THE STATE OF TEXAS

Mr. Chairman, I commend you for holding this important hearing examining what

is known about the science of climate change, mercury and the potential health effects of mercury emissions from power plants.

Given the timing of the energy debate on the Floor and this Committee’s ongoing

consideration of the Clear Skies Act, this is a very timely and important topic and

I commend the Chairman for setting time aside to focus on the issue. I realize our

focus today in regards to climate change is on the science, principally on temperature change. Two very different trains of thought are about to be presented to us

today and I think this is positive and encourages a good, healthy debate. The question that this panel has to wrestle with is moving ahead with a greenhouse gas policy that may or may not be based on sound science. I am concerned about the costs

in moving forward when there is a large body of science out there that says there

isn’t a problem.

To shift our focus just a bit, an issue of particular concern to me is the available

technology to control greenhouse gas emissions, specifically CO2. I am fairly certain

that some of my colleagues agree with the line of thought about to be outlined by

Dr. Mann, and this could very well lead this committee to a debate imposing mandatory controls on CO2. If this turns out to be the case it is imperative that this

Committee determine whether or not the technology is currently available to accomplish CO2 reductions that are effective enough to solve the ‘‘problems’’ thought to

be faced. I realize this is a topic for another hearing, but one that causes me concern.

In regards to mercury, in the 1990 amendments to the Clean Air Act, Congress

specifically requested that EPA conduct an analysis of the health effects of mercury

emissions from power plants and report back. EPA did conduct that study in 1997

and concluded that there was a ‘‘plausible link’’ between mercury emission and potential health effects, but was unable to quantify the link.

Six years have passed since EPA’s 1997 study. Unfortunately, we still have not

received any clarification from the EPA as to the magnitude of the health risks

posed by power plant emissions, even though we are currently on the verge of

spending billions of dollars to reduce those emissions.

I suspect that one of the reasons for this lack of information is that we are dealing

with a global problem. Many people today may find it surprising to learn that most

of the mercury that is deposited in the United States originates from outside our

borders. In fact, for most of the country, over 60–80 percent of the mercury deposited in the United States comes from emission sources located in another country.

Additionally, natural sources of mercury, such as forest fires and vegetation burning, account for over half of the world’s mercury emissions.

What this means is that we have control over only a very small portion of total

mercury emissions. Of the 5500 tons of mercury emitted globally, the U.S. accounts

for only about 155 tons, or 3 percent of global emissions. U.S. power plant emissions

which are estimated to be 48 tons per year, represent less than 1 percent of total

global emissions. Given how small this fraction is, it is both reasonable and prudent

to ask what impact controls on power plants will have on actual public health.

While EPA has unfortunately not provided us with any data on that question as

of yet, Leonard Levin from the Electric Power Industry has. According to his very

detailed analysis, control programs to reduce mercury emissions from power plants

are likely to have less than a 1-percent impact on public exposure in this country.

In fact, he estimates an impact of less than 0.3 percent. I do not know if this number is correct, but I think his very detailed analysis deserves comment from EPA,

especially given that this was exactly the kind of information Congress sought in

1990 when it amended the Act.

I look forward to hearing Dr. Levin’s testimony, as well as Dr. Rice’s and Dr.

Myers’. Your collective input is critical to this committee as we continue to debate

the Clear Skies initiative.

I yield back the balance of my time.

STATEMENT OF DR. WILLIE SOON, HARVARD-SMITHSONIAN CENTER

FOR ASTROPHYSICS

Distinguished Senators, panelists, and audience: My name is Willie Soon. I am

an astrophysicist with the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts. My training is in atmospheric and space physics and my sustained research interests for the past 10 years include changes in the Sun and their

possible impact on climate.
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This very rich area of scientific research, though still far from having definitive

answers, has seen exciting and important progress from our increasing technical

ability to measure, quantify, and interpret the changes in the Sun which could be

linked to changes of the Earth’s climate.

Today I focus on my latest research conclusions regarding climate change over

roughly the last 1000 years, especially the geographical pattern of those changes.

My scientific study is only possible because of the careful research produced by

nearly one thousand scientists around the world. Their expertise covers a very wide

range, including physical, chemical, biological, and geological sciences.

Together with several colleagues whose names are listed in the two scientific papers that I am submitting today for the record of this testimony, we have synthesized the results from several hundred studies of proxy records of climate, including much new work that has appeared in the scientific literature in the last 5 to

10 years.

Climate proxies are indirect climate sensors based on information from tree rings,

ice and seafloor sediment cores, corals, glaciers and other natural evidence. They

also include important cultural and documentary records.

It is important to recognize that these climate proxies are not temperature readings, but some proxies may be calibrated to give temperature changes. One example

is the measurement of the flow of heat in boreholes drilled through rocks or ice,

yielding century-scale temperature changes over several millennia. On the other

hand, some proxies are sensitive to local rainfall as well as temperature, as in the

case of annual tree growth in the southwest United States. Any given proxy may

respond to temperature differently from other proxies, depending on, for instance,

the type of proxy, location, or season.

For all those reasons, it remains a big challenge to produce an accurate global

temperature record over the past 1000 years from the diverse set of climate proxies.

But within the limits and lessons learned from our research papers, we can offer

three conclusions:

First, local and regional, rather than ‘‘global’’, changes are the most relevant and

practical measure of climate change and impact. This is because truly global averages rarely are available from the distant past, before modern satellite measurements, and because such averages can hide the significant changes that can occur

over large parts of the Earth.

Second, on a location by location basis, there was a widespread Medieval Warm

Period between approximately 800 and 1300 A.D. This Medieval Warm Period was

followed by a widespread colder period, called the Little Ice Age, that lasted from

approximately 1300 to 1900 A.D.

Third, there is no convincing evidence from each of the individual climate proxies

to suggest that higher temperatures occurred in the 20th century than in the Medieval Warm Period. Nor is there any convincing evidence to suggest that either the

rate of increase or the duration of warming during the 20th century were greater

than in the Medieval Warm Period.

The fact that local and regional climate has been varying with significant swings

in amplitude over many locations provides important challenges for computer simulation of climate. The full models that explore the Earth region by region can test

for the natural patterns of change over the last 1,000 years through the use of the

climate proxies we just discussed. In that way, the effects of human-caused climate

change can be weighed against observed natural variability in the climate system.

Having computer simulations reproduce past climate, which has been influenced

predominantly by natural factors, is key to making an accurate forecast that includes all potential human-made warming and cooling effects.

Further research could yield a deeper, quantitative improvement to our knowledge of local and regional climate variability during the past 1000 years. As we

could be inspired by Mr. Thomas Jefferson who remarked:

‘‘It is a common opinion that the climates of the several states of our union

have undergone a sensible change since the dates of their first settlements; that

the degrees of both cold & heat are moderated. The same opinion prevails as

to Europe; if facts gleaned from history give reasons to believe that, since the

times of Augustus Caesar, the climate of Italy, for example, has changed regularly at the rate of 1 [degree] of Fahrenheit’s thermometer for every century.

May we not hope that the methods invented in latter times for measuring with

accuracy the degrees of heat and cold, and the observations which have been

& will be made and preserved, will at length ascertain this curious fact in physical history?’’—Marginal notes from Thomas Jefferson’s Monticello Weather

Diary (January 1, 1810 to December 31, 1816).

I strongly believe that the time for research in paleoclimatology to fulfill this important role is now.
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1Which was awarded the 1989 nation-wide IEEE Nuclear and Plasma Sciences Society Graduate Scholastic Award and the 1991’s Rockwell Dennis Hunt Scholastic Award for ‘‘the most representative PhD thesis work’’ at the University of Southern California.

RESPONSE BY DR. WILLIE SOON TO ADDITIONAL QUESTIONS FROM SENATOR JEFFORDS

Question 1. In testimony, you said that you did not know whether you submitted

something for publication to Capitalism magazine. Here is the title and web address: ‘‘Global Warming Speculation vs. Science: Just Ask the Experts’’ by Sallie

Baliunas & Willie Soon (Capitalism Magazine—August 22, 2002) http://

capmag.com/article.asp?ID=1816. Did you submit or approve submission of this article for publication?

Response. With the benefit of your reminder, I hereby confirm that the above

mentioned article in Capitalism Magazine was taken from the original article ‘‘Just

Ask the Experts’’ by Baliunas and Soon originally published by the

TechCentralStation.com at the link: http://www.techcentralstation.com/

072302B.html. I did not submit the article to Capitalism Magazine.

Question 2. In your testimony you indicated that your training is in ‘‘atmospherics.’’ Could you please explain this term more fully, and indicate your formal

training in paleoclimatic studies and analysis?

Response. My PhD thesis1 was on collisional-radiative properties of high-temperature, partially ionized nitrogen, oxygen, helium and hydrogen plasmas at conditions

relevant to the Earth’s atmosphere. This is why I mentioned that I had formal

training in ‘‘atmospheric and space physics’’ in my oral remarks. If necessary, please

consult my thesis advisor, Professor Joseph Kunc at kunc@usc.edu for further details about my educational background.

I would add that the quality of knowledge about climate science or any other subject of interest must be judged on its own merits, and does not and must not be

determined by invoking the amount of formal schooling or consensus viewpoints

adopted by particular interest groups.

My research interests and learning about paleoclimatology has been obtained

mainly through the following individuals and sources:

(1) Professor Eric Posmentier (Eric.S.Posmentier@Dartmouth.EDU), who is also

my colleague.

(2) Professor David Legates (legates@UDel.Edu), who is also my colleague.

(3) Participation, both as a student and as lecturer, in numerous national and

international workshops, conferences and summer schools including (a) the 1993’s

NATO Advanced Research workshop on ‘‘Solar engine and its influence on terrestrial atmosphere and climate’’, (b) the 1994’s NASA-NOAA Summer School on Processes of Global Change, (c) the 1996’s (French) CNRS ‘‘Chaos et Fractales dans

l’activite Solaire’’, (d) the 2000’s ‘‘1st Solar and Space Weather Euroconference: The

Solar Cycle and Terrestrial Climate,’’ and other specialized meetings.

(4) Many other scientists also have been helpful in my eager learning of the subject: the late Professor Jean Grove (Girton College, Cambridge University), Professor

Jim Kennett (University of California Santa Barbara), Professor David J. A. Evans

(University of Glasgow), Professor Lowell Stott (University of Southern California),

Professor Hong-Chun Li (University of Southern California), Professor Reid Bryson

(University of Wisconsin), Professor Henri Grissino-Mayer (University of Kentucky),

Professor Emi Ito (University of Minnesota), Dr. ShaoPeng Huang (University of

Michigan), Dr. Zhonghui Liu (Brown University), Dr. Ming Tang (Institute of Geology and Geophysics, Chinese Academy of Sciences), Dr. Yang Bao (Cold and Arid

Regions Environmental and Engineering Research Institute, Chinese Academy of

Sciences), and Professor Bin Wang (University of Hawaii).

Question 3. Do you maintain that the proxy-based temperature reconstructions of

the Mann and colleagues do not extend into the latter half of the 20th century?

Response. The proxy-based temperature reconstructions for the Northern Hemisphere by Mann et al. (1998, Nature, vol. 392, 779–782) and Mann et al. (1999, Geophysical Research Letters, vol. 26, 759–762) extend from 1400–1980 and 1000–1980,

respectively. So it is true that those proxy-based temperature series did not cover

the 1981–2000 interval of the late 20th century.

Here is what close colleagues and co-authors (Bradley and Hughes) of Professor

Mann admitted in their independent (i.e., without Prof. Mann as co-author) and updated publication, ‘‘A caveat to [our] conclusion [about northern hemisphere temperature change over the last 1000 years] is that the current proxy-based reconstructions do not extend to the end of the 20th century, but are patched on to the instrumental record of the last 2–3 decades [emphasis added]. This is necessary because

many paleo data sets were collected in the 1960’s and 1970’s, and have not been
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up-dated [NOTE: this statement by Bradley et al. (2003) referred primarily to the

tree-ring data base from the International Tree-Ring Data base.], so a direct proxybased comparison of the 1990’s with earlier periods is not yet possible.’’ [p. 116 of

Bradley et al., 2003, In: Alverson, K., R.S. Bradley and T.F. Pedersen (eds.)

Paleoclimate, Global Change and the Future. Springer Verlag, Berlin, 105–149]

Agreeing with discussion on p. 260–261 of Soon et al. (2003), Bradley et al. (2003)

cautioned that ‘‘in the case of tree rings from some areas in high latitudes, the

decadal time-scale climatic relationships prevalent for most of this century appear

to have changed in recent decades, possibly because increasing aridity &/or

snowcover changes at high latitudes may have already transferred the ecological responses of trees to climate (cf. Jacoby and D’Arrigo 1995; Briffa et al. 1998). For

example, near the northern tree limit in Siberia, this changing relationship can be

accounted for by a century-long trend to greater winter snowfall. This has led to delayed snowmelt and thawing of the active layer in this region of extensive permafrost, resulting in later onset of the growing season (Vaganov et al. 1999). It is not

yet known how widely this explanation might apply to the other regions where partial decoupling has been observed, but regardless of the cause, it raises the question

as to whether there might have been periods in the past when the tree ring-climate

response changes, and what impact such changes might have on paleotemperature

reconstructions based largely on tree ring data.’’ (p. 116–117).

Bradley et al. (2003) also worried that ‘‘Paleoclimate research has had a strong

northern hemisphere, extra-tropical focus (but even there the record is poorly known

in many areas before the 17th century). There are very few high resolution

paleoclimatic records from the tropics, or from the extra-tropical southern hemisphere, which leaves many questions (such as the nature of climate in Medieval

times) unanswered.’’ (p. 141). Bradley et al. continued ‘‘All large-scale paleotemperature reconstructions suffer from a lack of data at low latitudes. In fact, most

‘‘northern hemisphere’’ reconstructions do not include data from the southern half

of the region (i.e. [missing comma] areas south of 30N). Furthermore, there are so

few data sets from southern hemisphere that it is not yet possible to reconstruct

a meaningful ‘‘global’’ record of temperature variability beyond the period of instrumental records. For the northern hemisphere records, it must be recognized that the

errors estimated for the reconstructions of Mann et al. (1999) and Briffa et al. (2001)

are minimum estimates, based on the statistical uncertainties inherent in the methods used. These can be reduced by the use of additional data (with better spatial

representation) that incorporate stronger temperature signals. However, there will

always be additional uncertainties that relate to issues such as the constancy of the

proxy-climate function over time, and the extent to which modern climate modes

(i.e., those that occurred during the calibration interval) represent the full range of

climate variability in the past [i.e., similar unresolved research questions had been

raised in p. 239–242 and p. 258–264 of Soon et al. 2003]. There is evidence that in

recent decades some high latitude trees no longer capture low frequency variability

as well as in earlier decades of the 20th century (as discussed below in Section 6.8)

which leads to concerns over the extent to which this may have also been true in

the more distant past. If this was a problem (and currently we are not certain of

that) it could result in an inaccurate representation of low frequency temperature

changes in the past. Similarly, if former climates were characterized by modes of

variability not seen in the calibration period, it is unlikely that the methods now

in use would reconstruct those intervals accurately. It may be possible to constrain

these uncertainties through a range of regional studies (for example, to examine

modes of past variability) and by calibration over different time intervals, but not

all uncertainty can be eliminated and so current margins of error must be considered as minimum estimates [meaning the actual range of error is larger than shown

in Mann et al. 1999 or the IPCC TAR’s charts].’’ (p. 114–115).

It is also very important to heed warnings and cautions from other serious researchers about not over stating the true confidence of a reconstructed climatic result based on indirect proxies. Esper et al. (2003, Climate Dynamics, vol. 21, 699–

706) modestly apprised of the current situation in reconstructing long-term climatic

information from tree rings: ‘‘Although these long-term trends agree well with ECS

[i.e., Esper, Cook, Schweingruber in 2002, Science, vol. 295, 2250–2253], the amplitude of the multi-centennial scale variations is, however, not understood. This is because (1) no single multi-centennial scale chronology could be built that is not systematically biased in the low frequency domain, and (2) no evidence exists that

would support an estimation of the biases either in the LTM [Long-term mean

standardization] nor in the RCS [Regional curve standardization] multi-centennial

chronologies. Consequently, we also avoided providing formal climate calibration

and verification statistics of the chronologies. Note also that the climate signal of

the chronologies’ low frequency component could not be statistically verified anyway.
157

This is because the high autocorrelations, when comparing lower frequency trends,

significantly reduce the degrees of freedom valid for correlation analyses. We believe

that a formal calibration/verification/transfer function approach would leave the impression that the long-term climate history for the Tien Shan [i.e., the location of

Esper and five colleagues’ study] is entirely understood, which is not the case. Further research is needed to estimate the amplitude of temperature variation in the

Alai Range [south of Kirghizia] over the last millennium.’’ (p. 705)

Question 4. Do you claim that the Mann study does not reconstruct regional patterns of temperature change in past centuries?

Response. In Soon et al. (2003, Energy & Environment, vol. 14, 233–296), I and

my colleagues cautioned that the regional temperature patterns resulted from Mann

and colleagues’ methodology are too severely restricted by the calibration particular,

we are concerned that the regional (and hence larger spatial-scale averages) variability of temperature on multidecadal and centennial time scales deduced from such

a method will be underestimated.

Recently, the methodology of Mann et al. (1998) has been seriously challenged by

McIntyre and McKitrick (2003, Energy & Environment, vol. 14, 751–771) in that

‘‘poor data handling, obsolete data and incorrect calculation of principal components’’ were shown as the errors and defects of Mann et al’s. paper. The exchange

between Mann and colleagues and McIntyre and McKitrick is ongoing, but the use

of obsolete data is a clear case of misrepresentation of regional basis of change in

Mann et al’s work. Further problems in Mann et al. (1998) are outlined under Question No. 13 below. Additional documentation (including responses by Prof. Mann

and his colleagues) and updates can be found in http://www.uoguelph.ca/rmckitri/

research/trc.html.

Question 5. Do you maintain that the Mann study extrapolated global temperature estimates from the northern hemisphere?

Response. I have not seen any global temperature curves presented in the two

earlier studies by Mann et al. (1998 and 1999). But please consider the deep concerns about the lack of proxy data especially over the tropics (30N to 30S) and the

southern hemisphere raised by Soon et al. (2003) and even in the independent paper

by Professor Mann’s close colleagues and co-authors (Bradley and Hughes), i.e., in

Bradley et al. (2003), discussed under Question No. 3 above.

‘‘Global’’ temperature estimates, based on indirect climate proxies, from 200–1980

were shown in Mann and Jones (2003, Geophysical Research Letters, vol. 30 (15),

1820) as Figure 2c. But I am unsure if the temperature series presented by Mann

and Jones (2003) could adequately represents the variability over the whole globe

since it was openly admitted that the proxies used covered only 8 ‘‘distinct regions’’

in the Northern Hemisphere and 5 for the Southern Hemisphere (see the coverage

of proxies shown in Figure 1 of Mann and Jones, 2003).

More importantly, Soon et al. (2004, Geophysical Research Letters, vol. 31,

L03209) showed that the 40-year smoothed instrumental temperature trend for the

Northern Hemisphere shown as Figure 2a of Mann and Jones (2003) has a physically implausible high value at year 2000 (see more discussion in Question No. 6

below). We caution that the extremely rapid rate of warming trend of 1 to 2.5° C

per decade implied by the published results by Mann and his colleagues over the

last one to 2 years [comparing Mann and Jones (2003) with both Mann (2002,

Science, vol. 297, 1481–1482) and Mann et al. (2003, Eos, 84(27), 256–257)], is most

likely due to the artifacts of methodology and their procedure of trend smoothing.

I am submitting the pdf file (SLB-GRL04-NHtempTrend.pdf) of Soon et al. (2004)

for the record of the committee.

Question 6. Do you maintain that historical and instrumental temperature records

that are available indicate colder northern hemisphere temperature conditions than

the Mann et al northern hemisphere temperature reconstruction in the past centuries?

Response. I am not sure about the meaning of this question. But when contrasted

with borehole-based reconstruction, the Northern Hemisphere terrestrial temperatures produced by Mann et al. (1998, 1999) over the last 500 years may have been

too warm by about 0.4〉° C during the 17th–18th century (see Huang et al. 2000, Nature, vol. 403, 756–758). Recent attempts by Mann et al. (2003, Journal of Geophysical Research, vol. 108. (D7), 4203) and Mann and Schmidt (2003, Geophysical

Research Letters, vol. 30 (12), 1607) to rejustify and defend the Mann et al. (1998,

1999) results have been shown to be either flawed or invalid by Chapman et al.

(2004, Geophysical Research Letters, vol. 31, L07205) and by Pollack and Smerdon

(2003, Geophysical Research Abstract of EGS, vol. 6, 06345). The eventual fact will

no doubt emerge with increased understanding, but Chapman et al. (2004) warned
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that ‘‘A second misleading analysis made by Mann and Schmidt [2003] concerns use

of end-points in reaching a numerical conclusion. . . . It is based on using end

points in computing changes in an oscillating time series, and is just bad science.’’

With regard to instrumental thermometer data of the past 100–150 years, it is

important to note that Soon et al. (2004) has recently shown that the 40-year

smoothed Northern Hemisphere temperature trend shown in Mann and Jones

(2003) has a physically implausible high value at the year 2000 endpoint especially

when studied in context with previous published results by Mann et al. (2003, Eos, vol. 84 (27), 256–257) and Mann (2002, Science, vol. 297, 1481–1482). This important updated information, admittedly with the benefit of hindsight, together with

the works by Chapman et al. (2004) and McIntyre and McKitrick (2003), showed

clearly that the Northern Hemisphere temperature trends, either proxy-based or instrumental, derived by Mann et al. (1998, 1999) and Mann and Jones (2003) are not

reliable.

Question 7. Is it your understanding that during the mid-Holocene optimum period (the period from 4000–7000 B.C.) that annual mean global temperatures were

more than a degree C warmer than the present day?

Response. Again, I am not sure if there are sufficient proxy data that would allow

a meaningful quantitative estimate of annual mean global temperatures back six to

nine thousand years. But in a new paper for the Quaternary Science Reviews, Darrell Kaufman and 29 co-authors (2004, Quaternary Science Reviews, vol. 23, 529–

560) found that indeed there are clear evidence for warmer than present conditions

during the Holocene at 120 out of 140 sites they compiled across the Western Hemisphere of the Arctic. Kaufman et al. (2004) estimated that, at the 16 terrestrial sites

where quantitative data are available, the local Holocene Thermal Maximum summer temperatures were about 1.6±0.8° C higher than the average of the 20th century. The coarse temperature map sketched on the NOAA’s Paleoclimatology web

site: http://www.ngdc.noaa.gov/paleo/globalwarming/images/polarbigb.gif suggests that the summer temperatures 6000 years ago may have been 2 to 4° C warmer than present in the other sector (Eastern Hemisphere) of the Arctic.

Question 8. As a climatologist, can you explain what kind of quantitative analysis

it takes to determine whether or not the last 50 years has been unusually warm

compared to the last 1000 years?

Response. The theoretical requirement is fairly simple: (a) find local and regional

proxies that are sensitive to variations of temperature on timescales of decade, several decades and century; (b) have sufficient spatial coverage of these local and regional proxies. Then one would be able to compare the last 50 years of the 1000-

year record with the previous 950 years.

Soon et al. (2003) had indeed initiated an independent effort in this direction and

concluded that a truly global or hemispheric averaged temperature record for the

past 1000 years is not yet forthcoming because of the large and disparate range of

the indirect local and regional proxies to temperature such that a robust ability of

different proxies in capturing all the necessary scales of variability cannot yet be

confirmed. The main problem I foresee in having any definitive answers for now is

related to the fact that the statistical association of each proxy to climatic variables

like temperature can itself be variable and changing depending on the location and

time interval. But I am not sure if the sole focus on temperature as the measure

of ‘‘climate’’ is sensible if not unnecessarily narrow.

In Soon et al. (2003), we consider climate to be more than just temperature so

we did not narrowly restrict ourselves to only temperature-sensitive proxies. For example, in addition to temperature, we are equally concerned about expansion and

reduction of forested and desert-prone areas, tree-line growth limit, sea ice changes,

balances of ice accumulation and ablation in mountain glaciers and so on. When

studying the ice balance for a glacier, it is important to insist that although glaciers

are very important indicators of climate change over a rather long time-scale, they

are not simply thermometers as often confused by heated discussion pointing to evidence for global warming by carbon dioxide (see additional discussion on factors, especially atmospheric carbon dioxide, in determining Earth’s climate and its change

under Questions No. 19, 20, 25, 30 and 35 below). Examples include statements by

Will Stefen, director of the International Geosphere-Biosphere Program, ‘‘Tropical

glaciers are a bellweather of human influence on the Earth system’’ (quoted in the

article ‘‘The melting snows of Kilimanjaro’’ by Irion, 2001, Science, vol. 291, 1690–

1691) or by Professor Lonnie Thompson, Ohio State University,

‘‘We have long predicted that the first signs of changes caused by global

warming would appear at the few fragile, high-altitude ice caps and glaciers

within the tropics . . . [t]hese findings confirm those predictions. We need to

take the first steps to reduce carbon dioxide emissions. We are currently doing
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nothing. In fact, as a result of energy crisis in California—and probably in the

rest of the country by this summer—we will be investing even more in fuelburning power plants. That will put more power in the grid but, at the same

times it will add carbon dioxide to the atmosphere, amplifying the problem’’

(quoted in Ohio State University’s press release, http://www.acs.ohio-state.edu/

units/research/archive/glacgone.htm).

A clarification about the physical understanding of modern glacier retreats and

climate change, especially those on Kilimanjaro, is necessary and has been forthcoming with important research progress. First, Molg et al. (2003, Journal of Geophysical Research, vol. 108 (D23), 4731) recently concluded that their study:

‘‘highlights that modern glacier retreat on Kilimanjaro is much more complex

than simply attributable to ‘global warming only’, a finding that conforms with

the general character of glacier retreat in the global tropic [Kaser, 1999]: a process driven by a complex combination of changes in several different climatic parameters . . . with humidity-related variables dominating this combination.’’

In another new paper for the International Journal of Climatology, Kaser et al.

(2004, International Journal of Climatology, ‘‘Modern glacier retreat on Kilimanjaro

as evidence of climate change: Observations and facts’’, vol. 24, 329–339; available

from http://geowww.uibk.ac.at/glacio/LITERATUR/index.html) provided clear answers that neither added longwave radiation from a direct addition of atmospheric

CO2 nor atmospheric temperature were the key variables for the observed changes,

as revealed in this long but highly informative passage:

‘‘Since the scientific exploration of Kilimanjaro began in 1887, when Hans

Meyer first ascended the mountain (not to the top at this time, but to the crater

rim), a central theme of published research has been the drastic recession of

Kilimanjaro’s glaciers (e.g., Meyer, 1891, 1900; Klute, 1920; Gilman, 1923;

Jager, 1931; Geilinger, 1936; Hunt, 1947; Spink, 1949; Humphries, 1959;

Downie and Wilkinson, 1972; Hastenrath, 1984; Osmastion, 1989; Hastenrath

and Greischar, 1997). Early reports describe the formation of notches, splitting

up and disconnection of ice bodies, and measurements of glacier snout retreat

on single glaciers, while later books and papers advance to reconstructing glacier surface areas. . . . Today, as in the past, Kilimanjaro’s glaciers are markedly characterized by features such as penitentes, cliffs (Figure 3a/b) [not reproduced here], and sharp edges, all resulting from strong differential ablation.

These features illustrate the absolute predominance [emphasis added] of incoming shortwave radiation and latent heat flux in providing the energy for ablation (Kraus, 1972). A positive heat flux from either longwave radiation or sensible heat flux, if available, would round-off and destroy the observed features

within a very short time ranging from hours to days. On the other hand, if destroyed, the features could only be sculptured again under very particular circumstances and over a long time. Thus, the existence of these features indicates

that the present summit glaciers are not experiencing ablation due to sensible

heat (i.e., from positive air temperature). Additional support for this is provided

by the Northern Icefield air temperature recorded from February 2000 to July

2002, which never exceeded ¥1.6° C, and by the presence of permafrost at 4,700

m below Arrow Glacier on the western slope . . .’’

Kaser et al. (2004) continue with this ‘‘synopsis of interpretations and facts’’:

‘‘A synopsis of (i) proxy data indicating changes in East African climate since

ca. 1850, (ii) 20th century instrumental data (temperature and precipitation),

and (iii) the observations and interpretations made during two periods of

fieldwork (June 2001 and July 2002) strongly support the following scenario.

Retreat from a maximum extent of Kilimanjaro’s glaciers started shortly before

Hans Meyer and Ludwig Purtscheller visited the summit for the first time in

1889, caused by an abrupt climate change to markedly drier conditions around

1880. Intensified dry seasons accelerated ablation on the respectively illuminated vertical walls left in the hole on top by Reusch Crater as a result of volcanic activity [emphasis added]. The development of vertical features may also

have started on the outer margins of the plateau glaciers before 1900, primarily

as the formation of notches, as explicitly reported following field research in

1898 and 1912 (Meyer, 1900; Klute, 1920). A current example of such a notch

development is the hole in the Northern Icefield (see Figure 2). Once started,

the lateral retreat was unstoppable, maintained by solar radiation despite less

negative mass balance conditions on horizontal glacier surfaces, and will come

to an end only when the glaciers on the summit plateau have disappeared. This

is most probable within next decades, if the trend revealed in Figure 1 continues. Positive air temperatures have not contributed to the recession process
160

on the summit so far. The rather independent slope glaciers have retreated far

above the elevation of their thermal readiness, responding to dry conditions. If

present precipitation regime persists, these glaciers will most probably survive

in positions and extents not much different from today. This is supported by the

area determinations in Thompson’s et al. (2002) map, which indicate that slope

glaciers retreated more from 1912 to 1952 than since then. From a hydrological

point of view, melt water from Kibo’s glaciers has been of little importance to

the lowland in modern times. Most glacier ablation is due to sublimation, and

where ice does melt it immediately evaporates into the atmosphere. Absolutely

no signs of runoff can be found on the summit plateau, and only very small rivers discharge from the slope glaciers. Rainfall reaches a maximum amount at

about 2,500 m a.s.l. [above sea level] (Coutts, 1969), which primarily feeds the

springs at low elevation on the mountain; one estimate attributes 95 percent

of such water to a forest origin (Lambrechts et al., 2002). The scenario presented offers a concept that implies climatological processes other than increased air temperature [emphasis added] govern glacier retreat on Kilimanjaro

in a direct manner. However, it does not rule out that these processes may be

linked to temperature variations in other tropical regions, e.g., in the Indian

Ocean (Latif et al., 1999; Black et al., 2003).’’

Lindzen (2002, Geophysical Research Letter, vol. 29, paper 2001GL014360) further added that ‘‘Recent papers show that deep ocean temperatures have increased

somewhat since 1950, and that the increase is compatible with predictions from coupled GCMs [General Circulation Models]. The inference presented is that this degree of compatibility constitutes a significant test of the models. . . . [But] it would

appear from the present simple model (which is similar to what the IPCC uses to

evaluate scenarios) that the ocean temperature change largely reflects only the fact

that surface temperature change is made to correspond to observations, and says

almost nothing about model climate sensitivity. . . . It must be added that we are

dealing with observed surface warming that has been going on for over a century.

The oceanic temperature change [at depth of 475 m or so] over the period reflects

earlier temperature change at the surface. How early depends on the rate at which

surface signals penetrate the ocean.’’ In other words, the recently noted warming

of the deeper ocean is not a proof of global surface and atmospheric warming by

increasing CO2 in the air because the parameters of climate sensitivity and rate of

ocean heat uptake are not sufficiently well quantified. In addition, if the earlier oceanic surface temperature warming mentioned by Lindzen were indeed initiated and

occurred substantially long ago, then there would be no association of that change

to man-made CO2 forcing.

Question 9. The IPCC has found that the late 20th century is the warmest period

in the last 1000 years, for average temperature in the northern hemisphere. Does

your paper provide a quantitative analysis of average temperatures for the northern

hemisphere for this specific time period—that is, for the later half of the 20th century?

Response. It should be understood that (1) the conclusion of the IPCC Working

Group I’s Third Assessment Report (2001; TAR), (2) the evidence shown in Figure

1b of the Summary for Policymaker, (3) Figure 5 of the Technical Summary, and

(4) Figure 2.20 in Chapter 2 of TAR were all derived directly from the conclusion

in Mann et al. (1999) and Figure 3a of Mann et al. (1999). Therefore all comments

and criticisms presented in this Q&A about Mann et al. (1999) apply to the IPCC

TAR’s conclusion. In addition, Soon et al. (2004) recently cautioned that the 40-year

smoothed northern hemisphere temperature trend shown in Figure 2.21 of TAR

(2001) cannot be replicated according to the methodology described in the caption

of Figure 2.21. The failure in replication introduces a significant worry about the

actual quality of scientific efforts behind the production of Figure 2.21 in TAR

(2001).

The answer to the second part of your direct question is no. Here are the related

reasons why a confident estimate of the averaged northern hemisphere temperature

for the full 1000 years (including the full 20th century) is not yet possible, despite

what had been claimed by Mann et al. (1999). First, several authors, including those

detailed in section 5.1 of Soon et al. (2003) and those pointed out in Question No.

6, had shown that the 1000-year series of mathematical temperature derived by

Mann et al. (1999) has significantly underestimated the multidecadal and centennial

scale changes. Second, the focus of Soon et al. (2003) is to derive understanding of

climatic change on local and regional spatial scales, instead of over the whole northern hemisphere per se, because those are the most relevant measures, in practical

sense, of change. In addition, we provided the first-order attempt to collect all available climate proxies relevant for local and regional climatic changes, but not re-
161

stricted to temperature alone. But more pertinent to your question is the fact discussed in Soon et al. (2003) that different proxies respond with differing sensitivities

to different climatic variables, seasons, plus spatial and temporal scales, so that a

convenient derivation of a self-consistent northern hemisphere averaged annual

mean temperature for the full 1000 years, desirable as the result may be, is not yet

possible.

Question 10. Does your paper provide any quantitative analysis of temperature

records specifically for the last 50 years of the 20th century?

Response. Soon et al. (2003) considered all available proxy records with no particular prejudice. If the individual proxy record covers up to the last 50 years of the

20th century, then quantitative comparisons are performed, mostly according to the

statements from the original authors. Please consider some of the detailed quantitative discussion in section 4 of Soon et al. (2003) and the qualitative results compiled in Table 1 of that paper.

Question 11. In an article in the Atlanta Journal Constitution (June 1, 2003), you

were quoted as acknowledging during a question period at a previous Senate luncheon that your research does not provide a comprehensive picture of the Earth’s temperature record and that you questioned whether that is even possible, and that you

did not, ‘‘. . . see how Mann and the others could ‘calibrate’ the various proxy

records for comparison.’’ How then does your analysis provide a comprehensive picture of Earth’s temperature record or have any bearing on the finding by the IPCC,

that the late 20th century is the warmest in the last 1000 years?

Response. Thank you for referencing the article. I must first state on the record

that contrary to the claim in this Atlanta Journal Constitution (June 1, 2003) article

http://www.ajc.com/business/content/business/0603/01warming.html, the writer,

never, as claimed, conducted a telephone interview with me. No such conversation

took place and I am rather shocked by this false claim. This fact has gone uncorrected until now.

The strengths and weaknesses of my research works are fully discussed in Soon

et al. (2003). The paper documented detailed local and regional changes in several

climatic variables to try to obtain a broader understanding of climate variability. We

concluded that:

‘‘Because the nature of the various proxy climate indicators are so different,

the results cannot be combined into a simple hemispheric or global quantitative

composite. However, considered as an ensemble of individual observations, an

assemblage of the local representations of climate establishes the reality of both

the Little Ice Age and the Medieval Warm Period as climatic anomalies with

worldwide imprints, extending earlier results by Bryson et al. (1963), Lamb

(1965), and numerous other research efforts. Furthermore, these individual

proxies are used to determine whether the 20th century is the warmest century

of the 2nd Millennium at a variety of globally dispersed locations. Many records

reveal that the 20th century is likely not the warmest nor a uniquely extreme

climatic period of the last millennium, although it is clear that human activity

has significantly impacted some local environments.’’

The question on the difficult problem of calibrating proxies of differing types and

sensitivities to climatic variables is discussed in Soon et al. (2003) and some criticisms on the weaknesses of the reconstruction by Mann et al. (1999) or the related

IPCC TAR’s conclusion are listed especially under Questions No. 6 and 9.

Question 12. Do you believe that appropriate statistical methods do not exist for

calibrating statistical predictors, including climate proxy records, against a target

variable, such as the modern instrumental temperature record?

Response. True progress in the field of paleoclimatology will certainly involve a

better and more robust means of interpreting and quantifying the variations and

changes seen in each high-resolution proxy record. The issue is not merely a problem awaiting solution through appropriate statistical methods like the EOF methodology adopted by Mann et al. (1998, 1999). On pp. 241–242 of Soon et al. (2003),

we briefly outlined our straight-forward approach and contrasted it to the one used

by Mann and colleagues that does not necessarily lead to results with physical

meaning and reality.

Question 13. In determining whether the temperature of the ‘‘Medieval Warm Period’’ was warmer than the 20th century, does your study analyze whether a 50-

year period is either warmer or wetter or drier than the 20th century? If so, why

is it appropriate to use indicators of drought and precipitation directly to draw inferences of past temperatures? Please list peer-reviewed works that specifically support

the use of these indicators for inferring past temperature.
162

Response. The detailed discussion behind our usage of the term ‘‘Medieval Warm

Period’’ or ‘‘Little Ice Age’’ was described in Soon et al. (2003). We are mindful that

the two terms should definitely include physical criteria and evidence from the thermal field. But we emphasize that great bias would result if those thermal anomalies

were dissociated from hydrological, cryospheric, chemical, and biological factors of

change. So indeed our description of a Medieval Climatic Anomaly (see a similar

sentiment later reported by Bradley et al. 2003, Science, vol. 302, 404–405) in Soon

et al. (2003) includes a warmer time that contains both drought or flooding conditions depending on the locations.

With regard to the last part of your question, I would answer by detailing only

one example—Mann et al (1998). This influential study used both direct precipitation measurements and precipitation proxies as temperature indicators. This study

was indeed applied by the IPCC TAR (2001). These include historical precipitation

measurements in 11 grid cells, two coral proxies (reported in Mann et al. [1998] as

precipitation proxies; see http://www.ngdc.noaa.gov/paleo/ei/data—supp.html for

this and following references), two ice core proxies, 3 reconstructions of spring precipitation in southeast United States by Stahle and Cleaveland from tree ring data,

12 principal component series for tree rings in southwestern United States and

Mexico reported as precipitation proxies by Stahle and Cleaveland (and Mann et al.

1998) and one tree ring series in Java—making a total of 31 precipitation series

used as proxies in temperature reconstruction by Mann et al. (1998). In this peerreviewed article, for the precipitation data in a grid cell in New England, the researchers apparently used historical data from Paris, France (please see Figure 2

of McIntyre and McKitrick, 2003 and their discussion on pp. 758–759). For a grid

cell near Washington DC, the researchers used historical data from Toulouse,

France. For a grid cell in Spain, the researchers used precipitation data from Marseilles, France. Of the 11 precipitation series used in Mann et al. (1998), only one

series (Madras, India) is correctly located. The precipitation data used by these authors cannot be identified in the source cited in paper Mann et al. (1998). While precipitation data and precipitation-related proxies can be instructive in providing information on past distribution of moisture and circulation patterns (and thus temperature), it is important to correctly identify the series used and important not to

use data from the wrong continent for historical reconstructions.

Question 14. Do you maintain that any two 50-year periods that occur within a

multi-century interval can be considered ’coincident’ from a climatic point of view?

Response. The question raised here about the connection of any two 50-year periods in any two regions to be related from climatic point of view is both important

and interesting. But the answer will be strongly dependent on the nature of forcings

and feedbacks involved. If longer-term cryospheric or oceanic processes are involved

then the answer would be yes.

Question 15. Do your two recent studies employ an analysis (that is, a statistical

or analytical operation performed upon numerical data) of a single proxy climate

record?

Response. The meaning of this question is not entirely clear to me. But I would

say yes under the context of what is being said.

Question 16. Has your study produced a quantitative reconstruction of past temperature patterns? Do you have a measure of uncertainty or verification in your description of past temperatures?

Response. The results and conclusion of Soon et al. (2003) are best judged by the

paper itself. Quantitative assessments of local and regional changes through the climatic proxies are discussed in section 4 of that paper as well as some qualitative

picture described in Figures 1, 2 and 3 of that paper. Again, Soon et al. (2003) did

not tried to distill all the collected proxies down to produce a strict temperatureonly result since we are interested in a broader understanding of climate variability.

Part of the answers given under Questions No. 9 and 11 can help elaborate what

was done by Soon et al. (2003). I would also like to direct your attention to the two

warnings listed under Question No. 3 by Bradley et al. (2003) and Esper et al.

(2003) concerning any undue, over confidence in promoting quantitative certainties

in the reconstruction of past temperatures through highly imprecise black boxes of

indirect proxies.

Question 17. Your study indicates that you have compiled the results of hundreds

of previous paleo-climate studies. Have you verified your interpretation of the hundreds of studies with any of the authors/scientists involved in those studies? If so,

how many?

Response. Specific authors and scientists that provided help in our work were listed in the acknowledgement section (p. 272) of Soon et al. (2003). We have also re-
163

ceived generous help and comments from several scientists who are certainly highly

qualified in terms of paleoclimatic studies. But the ultimate quality and soundness

of our research shall always be our own responsibility.

In the September 5, 2003 Chronicle for Higher Education article (by Richard

Monastersky), there were indeed two very serious accusations that suggested that

Soon et al. (2003) had misrepresented or abused the conclusions by two original authors whose work we had cited. Our corrections and explanations to these unfortunately false claims can be studied from the documentation listed in the URL http:/

/cfa-www.harvard.edu/∼wsoon/ChronicleHigherEducation03-d (read especially

Sep12-lettoCHE3.doc and Sep12-lettoCHE4.doc).

Question 18. What was earth’s climate like the last time that atmospheric concentrations of carbon dioxide were at today’s levels or about 370 parts per million

(ppm) and what were conditions like when concentration were at 500 ppm, which

will occur around 2060 or so?

Response. Co-answer to this question is listed under Question No. 19 below.

Question 19. Please describe any known geologic precedent for large increases of

atmospheric CO2 without simultaneous changes in other components of the carbon

cycle and the climate system.

Response. My July 29, 2003 testimony was about the climate history of the past

1000 years detailed in Soon et al. (2003) rather than any potential (causal or otherwise) relationship between atmospheric carbon dioxide and climate. The fact remains that the inner working of the global carbon cycle and the course of future

energy use are not sufficiently understood or known to warrant any confident prediction of atmospheric CO2 concentration at year 2060. Please consider co-answer

to this question under Question No. 25 below.

However, it is abundantly obvious that atmospheric CO2 is not necessarily an important driver of climate change. It is indeed a puzzle that despite the relative low

level of atmospheric CO2 of no more than 300 ppm in the past 320–420 thousand

years (Kawamura et al., 2003, Tellus, vol. 55B, 126–137) compared to the high levels

of 330–370 ppm since the 1960’s there is the clear suggestion of significantly warmer temperatures at both Vostok and Dome Fuji, East Antarctica, during the

interglacials at stage 9.3 (about 330 thousand years before present; warmer by

about 6° C) and stage 5.5 (about 135 thousand years before present; warmer by

about 4.5° C) than the most recent 1000 years (see Watanabe et al., 2003, Nature,

vol. 422, 509–512; further detailed discussion on environmental changes in

Antartica over the past 1000 years or so, including the most recent 50 years can

be found in section 4.3.4 or pp. 256–257 of Soon et al. 2003).

But there are important concerns about the retrieval of information on atmospheric CO2 levels from ice cores. Jaworowski and colleagues (1992, The Science of

the Total Environment, vol. 114, 227–284) explained that:

‘‘Ice is not a rigid material suitable for preserving the original chemical and

isotopic composition of atmospheric gas inclusion. Carbon dioxide in ice is

trapped mechanically and by dissolution in liquid water. A host of physicochemical processes redistribute CO2 and other air gases between gaseous, liquid

and solid phases, in the ice sheets in situ, and during drilling, transport and

storage of the ice cores. This leads to changes in the isotopic and molecular composition of trapped air. The presence of liquid water in ice at low temperatures

[‘even below—70° C’] is probably the most important factor in the physico-chemical changes. The permeable ice sheet with its capillary liquid network acts as

a giant sieve which redistributes elements, isotopes and micro-particles. Carbon

dioxide in glaciers is contained: (1) in interstitial air in firn; (2) in air bubbles

in ice; (3) in clathrates; (4) as a solid solution in ice crystals; (5) dissolved in

intercrystalline veins and films of liquid brine; and (6) in dissolved and particulate carbonates. Most of the CO2 is contained in ice crystals and liquids, and

less in air bubbles. In the ice cores it is also present in the secondary gas cavities, cracks, and in the traces of drilling fluids.

The concentration of CO2 in air recovered from the whole ice is usually much

higher than that in atmospheric air. This is due to the higher solubility of this

gas in cold water, which is 73.5- and 35-times higher than that of nitrogen and

oxygen, respectively. The composition of other atmospheric gases (N2, O2, Ar)

is also different in ice and in air inclusions than in the atmosphere. Argon–39

and 85Kr data indicate that 36–100 percent of air recovered from deep Antarctic ice cores is contaminated by recent atmospheric air during field and laboratory processing. Until about 1985, CO2 concentrations in gas recovered from

primary air bubbles and from secondary gas cavities in pre-industrial and ancient ice were often reported to be much higher than in the present atmosphere.

After 1985, only concentrations below the current atmospheric level were pub-
164

lished. Our conclusion is that both these high and low CO2 values do not represent real atmospheric content of CO2. Recently reported concentrations of CO2 in primary and secondary gas inclusions from deep cores, covering about the last 160,000 years, are much below

the current atmospheric level, although several times during this period the

surface temperature was 2–4.5° C higher than now. If these low concentrations

of CO2 represented real atmospheric levels, this would mean (1) that CO2 had

not influenced past climatic changes, and (2) that climatic changes did not influence atmospheric CO2 levels.’’ (p. 272–273)

Additional historical evidence reveals natural occurrences of large, abrupt climatic

changes that are not uncommon and they occurred without any known causal ties

to large radiative forcing change. Phase differences between atmospheric CO2 and

proxy temperature in historical records are often not fully resolved; but atmospheric

CO2 has shown the tendency to follow rather than lead temperature and biosphere

changes (see e.g., Dettinger and Ghil, 1998, Tellus, vol. 50B, 1–24; Fischer et al., 1999, Science, vol. 283, 1712–1714; Indermuhle et al., 1999, Nature, vol. 398, 121–

126).

In addition, there have been geological times of global cooling with rising CO2

(during the middle Miocene about 12.5–14 million years before present [Myr BP],

for example, with a rapid expansion of the East Antarctic Ice Sheet and with a reduction in chemical weathering rates), while there have been times of global warming with low levels of atmospheric CO2 (such as during the Miocene Climate Optimum about 14.5–17 Myr BP as noted by Panagi et al., 1999, Paleocenoragphy, vol.

14, 273–292). A new study of atmospheric carbon dioxide over the last 500 million

years (Rothman, 2002, Proceedings of the (US) National Academy of Sciences, vol.

99, 4167–4171) concluded that, ‘‘CO2 levels have mostly decreased for the last 175

Myr. Prior to that point [CO2 levels] appear to have fluctuated from about two to

four times modern levels with a dominant period of about 100 Myr. . . . The resulting signal exhibits no systematic correspondence with geologic record of climatic

variations at tectonic time scales.’’

Question 20. According to a study published in Science magazine, [B. D. Santer,

M. F. Wehner, T. M. L. Wigley, R. Sausen, G. A. Meehl, K. E. Taylor, C. Amman,

W. M. Washington, J. S. Boyle, and W. Bruggemann Science 2003 July 25; 301:

479–483], manmade emissions are partly to blame for pushing outward the boundary between the lower atmosphere and the upper atmosphere. How does that fit

with the long-term climate history and what are the implications?

Response. It should first be noted that Pielke and Chase (2004, Science, vol. 303,

1771b; and see p. 1771c by Santer et al. and additional counter-reply by Pielke and

Chase, with input from John Christy and Anthony Reale, available as paper 278b

at http://blue.atmos.colostate.edu/publications/reviewedpublications.shtml) had

criticized and challenged Santer et al.’s claim and conclusion that,

‘‘[o]ur results are relevant to the issue of whether the ‘real-world’ troposphere

has warmed during the satellite era. . . . The direct evidence is that in the ALL

experiment [i.e., climate model results that included changes in well-mixed

greenhouse gases, direct scattering effects of sulfate aerosols, tropospheric and

stratospheric ozone, solar total irradiance and volcanic aerosols; see more discussion below], the troposphere warms by 0.07° C/decade over 1979–1999. This

warming is predominantly due to increases in well-mixed greenhouse gases.

. . . Over 1979–1999, roughly 30 percent of the increase in tropopause height

in ALL is explained by greenhouse gas-induced warming of the troposphere.

Anthropogenically driven tropospheric warming is therefore an important factor

in explaining modeled changes in tropopause height.’’

In contrast, Pielke and Chase (2004) offered the observed evidence and concluded

that

‘‘[g]lobally averaged tropospheric temperature trends are statistically indistinguishable from zero. Thus, the elevation of the globally averaged tropopause report in [Santer et al., 2003] cannot be attributed to any detectable tropospheric

warming over this period.’’ In addition, ‘‘the climate system is much more complex than defined by tropospheric temperature and tropopause changes. Linear

trend analysis [in Santer et al., 2003] is of limited significance. Changes in global heat storage provide a more appropriate metric to monitor global warming

than temperature alone.’’

Soon and Baliunas (2003, Progress in Physical Geography, vol. 27, 448–455) had

also previously outlined the incorrect fingerprint of CO2 forcing observed in even the

best and sophisticated version of climate models thus far. A more general and comprehensive discussion about the fundamental difficulties on modeling the effects of
165

carbon dioxide using current generation of climate models is given in Soon et al.

(2001, Climate Research, vol. 18, 259–271). Thus, the new paper by Santer et al.

(2003) does not supercede or overcome the difficulties with respect to General Circulation Climate Models raised in Soon and Baliunas (2003).

Both the meaning and strength of the model-dependent results shown in Santer

et al. (2003) remain doubtful and weak for several additional reasons.

First, Figure 2 of Santer et al. (2003) itself confirmed that the modeled changes

in tropopause height are caused mainly by large stratospheric cooling related to

changes in stratospheric ozone (they admitted so even though their note No. 35 indicates that their numerical experiments did not separate tropospheric and stratospheric ozone changes) rather than by the well-mixed greenhouse gases that are

supposed to be the subject of concern. Second, the model experiments of Santer et

al. (2003) did not include changes in stratospheric water vapor which is known to

be a significant factor for the observed stratospheric cooling (see e.g., Forster and

Shine, 1999, Geophysical Research Letters, vol. 26, 3309–3312). Third, the failure to

account for stratospheric water vapor contradicted the documented significant increases of stratospheric water vapor in the past half-century from a variety of instrumentations (e.g., Smith et al, 2000, Geophysical Research Letters, vol. 27, 1687–

1690; Rosenlof et al., 2001, Geophysical Research Letters, vol. 28, 1195–1198; though

Randel et al. [2004, Journal of the Atmospheric Sciences, submitted] recently noted

that unusually low water vapor has been observed in the lower stratosphere for

2001–2003). Fourth, the model experiments by Santer et al. (2003) had clearly neglected (see note No. 18 of that paper) the role of the Sun’s ultraviolet radiation that

is not only known to be variable (e.g., Fontenla et al. 1999, The Astrophysical Journal, vol. 518, 480–499; White et al., 2000, Space Science Reviews, vol. 94, 67–74)

but also known to exert important influence on both the chemistry and thermal

properties in the stratosphere and troposphere (e.g., Larkin et al., 2000, Space

Science Reviews, vol. 94, 199–214).

Finally, the physical representation of aerosol forcing (which should not be restricted to sulfate alone) in Santer et al. (2003) is clearly not comprehensive and

at best highly selective. Early on, Russell et al. (2000, Journal of Geophysical Research, vol. 105, 14891–14898) cautioned that

‘‘[o]ne danger of adding aerosols of unknown strength and location is that they

can be tuned to give more accurate comparisons with current observations but

cover up model deficiencies.’’

Anderson et al. (2003, Science, vol. 300, 1103–1104 and see also exchanges in

Crutzen et al., 2003, vol. 303, 1679–1681) recently cautioned that:

‘‘we argue that the magnitude and uncertainty of aerosol forcing may affect the

magnitude and uncertainty of total forcing [i.e., ‘the global mean sum of all industrial-era forcings’] to a degree that has not been adequately considered in

climate studies to date. Inferences about the causes of surface warming over the

industrial period and about climate sensitivity may therefore be in error. . . .

Unfortunately, virtually all climate model studies that have included anthropogenic aerosol forcing as a driver of climate change (diagnosis, attribution, and

projection studies; denoted ‘applications’ in the figure) have used only aerosol

forcing values that are consistent with the inverse approach. If such studies

were conducted with the larger range of aerosol forcings determined from the

forward calculations, the results would differ greatly. The forward calculations

raise the possibility that total forcing from preindustrial times to the present

. . . has been small or even negative. If this is correct, it would imply that climate sensitivity and/or natural variability (that is, variability not forced by anthropogenic emissions) is much larger than climate models currently indicate.

. . . In addressing the critical question of how the climate system will respond

to this [anthropogenic greenhouse gases’] positive forcing, researchers must seek

to resolve the present disparity between forward and inverse calculations. Until

this is achieved, the possibility that most of the warming to date is due to natural variability, as well as the possibility of high climate sensitivity, must be

kept open. [emphasis added]’’

To further understand the complexity of calculating aerosol forcing, Jacobson

(2001, Journal of Geophysical Research, vol. 106, 1551–1568) has to account for a

total of 47 species ‘‘containing natural and/or anthropogenic sulfate, nitrate, chloride, carbonate, ammonium, sodium, calcium, magnesium, potassium, black carbon,

organic matter, silica, ferrous oxide, and aluminium oxide’’ in his recent estimate

of only the global direct radiative forcing by aerosols. (Jacobson [2001] found that

the global direct radiative forcing by anthropogenic aerosols is only ¥0.12 W/m2

while the forcing by combined natural and anthropogenic sources is ¥1.4 W/m2.)

There are also the indirect aerosol effects. Temperature or temperature change is
166

clearly not the only practical measure of effects by aerosols. Haywood and Boucher

(2000, Reviews of Geophysics, vol. 38, 513–543) stressed the fact that the indirect

radiative forcing effect of the modification of cloud albedo by aerosols could range

from ¥0.3 to ¥1.8 W/m2, while the additional aerosol influences on cloud liquid

water content (hence, precipitation efficiency), cloud thickness and cloud lifetime are

still highly uncertain and difficult to quantify (see e.g., Rotstayn and Liu, 2003,

Journal of Climate, vol. 16, 3476–3481). This is why one can easily appreciate the

difficulties faced by Santer et al. (2003) because climate forcing by aerosols is not

only known within a wide range of uncertainties but also to a large degree of unknown.

Therefore, I conclude that in addition to the fundamental issues related to climate

model representation of physical processes, papers like Santer et al. (2003) have also

failed the basic requirement for internal consistencies in the accounting for potentially relevant climatic forcing factors and feedbacks. This is why I cannot comment

on the implication of this particular study and the meaning of the study for longterm climate history.

Question 21. In your testimony, you discussed there being ‘‘warming’’ and ‘‘cooling’’ for different periods. If you did not construct an integral across the hemisphere

or a real timeline, don’t your findings really just say there were some warm periods

and cool periods, and therefore cannot speak to the issue of the rate of warming

or cooling?

Response. I am not sure about the meaning of this question and the quotes. My

oral remark was merely referring to ‘‘making an accurate forecast that includes all

potential human-made warming and cooling effects.’’ The detailed discussion about

the climatic and environmental changes for the past 1000 years as deduced from

the collection of proxies I had studied was given in Soon et al. (2003). I can certainly

speak to the rate of warming or cooling at any given location or region when the

available proxy, with sufficient temporal resolution, is known or proven to be temperature sensitive.

Question 22. Is there any indication that regional climate variations are any larger or smaller at present than over the last 1000 years (with 2003, for example, perhaps being a case with large regional variations from the normal)?

Response. I would not recommend considering the pattern of change from a single

year, i.e., 2003, and called it a climate change. But the fact is that in Soon et al.

(2003) we had carefully studied individual proxy records from various locations and

regions. As an example, the 2000-year bottom-sediment record from Moon Lake,

North Dakota, shows there is perhaps a distinct shift in the mode of hydrologic variability in the Northern Great Plain region starting around 1200 AD with the more

recent period being more variable from the past. But, as indicated in the chart

below, the author of this paper also noted that the severe droughts of the 1890’s

and 1930’s around this area are ‘‘eclipsed by more extensive droughts before the beginning of the instrumental period.’’

Question 23. In your oral presentation, you talked about ‘‘[h]aving computer simulation.’’ Could you please explain what you [as in your original] computer simulation or modeling to which you are referring, and, (a) Has this model gone through

the appropriate set of model intercomparison studies like the various othe global

models? (b) What forcings have been used to drive it? (c) How does it develop regional climate variations, and are these comparable to observations? and, (d) How

does it perform over the 20th century, for example?
167

Response. I apologize for any potential confusions.

In my oral remark, I said,

‘‘The entirety of climate proxies over the last 1,000 years shows that over

many areas of the world there has been, and continues to be, large climate

changes. Those changes provide challenges for the computer simulations of climate. The full models, which explore the Earth region by region, can be tested

against the natural patterns of change over the last 1,000 years that are detailed by the climate proxies. Having computer simulations reproduce past patterns of climate, which has been influenced predominantly by natural factors,

is key to making an accurate forecast that includes all potential human-made

warming and cooling factors.’’

So in the context of what I said, this question is clearly misdirected by someone

who did not understand my remark. I was speaking on the potential application of

works like Soon et al. (2003) for improving our ability to calculate with confidence

the potential effects from man-made factors by first and foremost having a climate

model that can at least reproduce some of the observed local and regional changes

of the past.

Personally, I am also conducting my research through the help of several climate

models (both simple and complex types) appropriate for my interests and I would

certainly apply what I found in Soon et al. (2003) to my own future studies using

climate models. Any additional comments will be beyond the simple context of my

oral testimony. But, it may be useful to take note of the comments by Green (2002,

Weather, vol. 57, 431–439):

‘‘It has always worried me that simple models of climate do not seem to work

very well. Experts on numerical models say that this is because the atmosphere

is very complicated, and that large numerical models and computers are needed

to understand it. I worry because I do not know what they have hidden in those

models and the programs they use. I wonder what I can compare their models

with. Not with each other because they belong to a sort of club, where to have

a model that disagrees with everyone else’s puts you outside. That is not a bad

system, unless of course they are all wrong. Another curiosity of complicated

models is that their findings are rarely used to improve the model that preceded

them. I would have expected that the more complex model would show where

the simpler one had got it wrong, and allow it to be corrected for that misrepresentation.’’

Question 24. Based on the various comments of your scientific colleagues regarding your paper, including the methodological flaws pointed out in that paper by the

former editor-in-chief of Climate Research, are you planning any reworking of your

study or any further studies in the paleoclimatic area?

Response. The use of a phrase like ‘‘methodological flaws’’ is a very convenient attempt to dismiss the weight of scientific evidence presented in Soon et al. (2003) but

unfortunately without any clear nor confirmable basis. Thus far, the only formal

criticism of Soon et al. (2003) was by Mann et al. (2003, Eos, vol. 84(27), 256–257)

and we had provided our response to that criticism in Soon et al. (2003b, Eos, vol.

84(44), 473–476). My research interest and work to fully discern and quantitatively

describe the local and regional patterns of climate variability over the past 1000

years or so will certainly continue despite this mis-characterization.

It should however not be left unnoticed that several very serious problems in

Mann et al. (1998, 1999), Mann and Schmidt (2003) and Mann and Jones (2003) had

been found recently. Those unresolved anomalies are outlined in my answers to your

Questions No. 3, 4, 5, 6, 9 and 13. A careful reworking with a fully open access to

all data as well as a fully disclosed transparency of the actual methodologies and

detailed applications will be the next important step for paleoclimate reconstruction

research.

Question 25. You indicated that there would likely be relatively small climatic response to even substantial increases in the CO2 concentration. Do you disagree with

the radiation calculations that have been done and the trapped energy that they calculate, as per the peer-reviewed literature? If so, please explain.

Response. First, please consider the above discussion on climate forcing factors

and climate response sensitivities under Question No. 20 as part of the answers to

this question.

Second, I do not believe that I had made any strong claim, one way or another,

about the CO2 forcing and potential response in any specific quantitative term during my testimony (since factually no one can). I do want to comment, as in my response under Question No. 19, that CO2, as a minor greenhouse gas, is not a determinant of Earth’s climate and therefore not entirely obvious a driver of its change.
168

2 A more pedagogical discussion of the greenhouse effect is given by Lindzen and Emanuel

(2002) in Encyclopedia of Global Change, Environmental Change and Human Society, Volume

1, Andrew S. Goudie, editor in chief, p. 562–566, Oxford University Press, New York, 710 pp.

Most calculations in peer-reviewed literature (or not) that focus on the CO2 factor

indeed would only like us to believe that CO2, especially under the realm of radiative forcing, is the predominant factor for driving anomalous climate responses,

while the unavoidable and very difficult core subject about the actual dynamical

state of Earth’s ‘‘mean’’ climate is ignored.

Third, some 10 years ago, Lindzen (1994, Annual Review in Fluid Mechanics, vol.

26, 353–378) pointed out a rather serious internal inconsistency regarding the role

of water vapor and clouds when the physics of greenhouse effect is normally evaluated even among expert scientists or expert sources of information. (See e.g., the

comment ‘‘without [the greenhouse effect], the planet would be 65 degrees colder’’

by Jerry Mahlman in the February 2004 issue of Crisis Magazine, http://

www.crisismagazine.com/february2004/feature1.htm) and the description of Greenhouse Effect in the EPA’s ‘‘global warming for kids’’ webpage: http://www.epa.gov/

globalwarming/kids/greenhouse.html.) Lindzen notes the ‘‘artificial inevitability’’ for

the predominance of CO2 radiative forcing as a climatic factor in the following passage.

‘‘In most popular depictions of the greenhouse effect, it is noted that in the

absence of greenhouse gases, the Earth’s mean temperature would be 255 K

[about 0°F], and that the presence of infrared absorbing gases elevates this to

288 K [59°F]. In order to illustrate this, only radiative heat transfer is included

in the schematic illustrations of the effect (Houghton et al. 1990, 1992) [IPCC

reports]; this lends an artificial inevitability to the picture. Several points

should be made concerning this picture: 1. The most important greenhouse gas

is water vapor, and the next most important greenhouse substance consists in

clouds; CO2 is a distant third (Goody & Yung 1989). 2. In considering an atmosphere without greenhouse substances (in order to get 255 K), clouds are retained for their visible reflectivity while ignored for their infrared properties.

More logically, one might assume that the elimination of water would also lead

to the absence of clouds, leading to a temperature of about 274 K [or 278 K depending on what value of the solar irradiation factor is used] rather than 255

K. 3. Pure radiative heat transfer leads to a surface temperature of about 350

K rather than 288 K. The latter temperature is only achieved by including a

convective adjustment that consists simply in adjusting vertical temperature

gradient so as to avoid convective instability while maintaining a consistent radiative heat flux. . . . ‘‘ (p. 359–361)2

Hu et al. (2000, Geophysical Research Letters, vol. 27, 3513–3516) added that as

the sophistication of parameterization of atmospheric convection increases, there is

a tendency for climate model sensitivity to variation in atmospheric CO2 concentration to decrease considerably. In Hu et al. (2000)’s study, the change is from a decrease in the averaged tropical warming of 3.3 to 1.6° C for a doubling of CO2 that

is primarily associated the corresponding decrease in the calculated total atmospheric column increase in water vapor from 29 percent to 14 percent.

Question 26. If you accept those radiation calculations as valid, please explain

why you seem to believe that the energy trapped by the greenhouse gases will have

a small effect whereas you seem to believe that small changes in solar energy will

have very large climatic effects?

Response. In addition to my answers under Questions No. 19, 20 and 25 above,

I would like to point out that the Sun’s radiation is not only variable but it varies

in the ultraviolet part of the electromagnetic spectrum often by factors of 10 or

more. The question about the relative effects of anthropogenic greenhouse gases and

the Sun’s radiation in terms of radiative forcing is certainly of interest but it does

not add much to my current research quest to understand the Earth’s mean climatic

state and its nonlinear manifestations.

Question 27. Please explain why you think the physically based climate models

seem to quite satisfactorily represent the seasonal cycles of the climate at various

latitudes based on the varying distributions of solar and infrared energy, but then

would be so far off in calculating the climatic response for much smaller perturbations to solar radiation and greenhouse gases?

Response. As indicated below, the first part of this sentence about a satisfactory

representation of seasonal cycles of climate by computer climate models is not any

assured statement of fact. This is why the followup question cannot be logically answered.
169

For example, E. K. Schneider (2002, Journal of Climate, vol. 15, 449–469) noted

that:

‘‘[a]t this writing, physically consistent and even flux-corrected coupled atmosphere-ocean general circulation models (CGCMs) have difficulty in producing a

realistic simulation of the equatorial Pacific SST [sea surface temperature], including annual mean, annual cycle, and interannual variability. Not only do the

CGCM simulations have significant errors, but also there is little agreement

among models.’’

In a systematic comparison of the performance of 23 dynamical ocean-atmosphere

models, Davey et al. (2002, Climate Dynamics, vol. 18, 403–420) found that ‘‘no single model is consistent with the observed behavior in the tropical ocean regions . . .

as the model biases are large and gross errors are readily apparent.’’ Without flux

adjustment, most models produced annual mean equatorial sea surface temperature

in the central Pacific that are too cold by 2–3° C. All GCMs except one simulated

the wrong sign of the east-west SST gradient in the equatorial Atlantic. The GCMs

also incorrectly simulated the seasonal climatology in all ocean sections and its

interannual variability in the Pacific ocean.

Question 28. In regard to your answers to the previous questions, to what extent

is your indication of a larger climate sensitivity for solar than greenhouse gases due

to quantitative analysis of the physics and to what extent due to your analysis of

statistical correlations? Is this greater responsiveness for solar evident in the baseline climate system, or just for perturbations, and could you please explain?

Response. Please see my answers to Questions No. 26 above and 30 below.

Question 29. Please explain why you seem to accept that solar variations, volcanic

eruptions, land cover change, and perhaps other forcings can have a significant climatic influence, but changes in CO2 do not or cannot have a comparable influence?

Response. Please see my answers to Question No. 30.

Question 30. Could you please clarify why it is that you think the best way to

get an indication of how much the climate will change due to global-scale changes

in greenhouse gases or in solar radiation is to look at the regional level rather than

the global scale? How would you propose to distinguish a natural variation from a

climate change at the local to regional level?

Response. Questions No. 28, 29 and 30 seem to be based on the unreasonable presumptions that some special insights about the effects of solar irradiation or land

cover changes or even volcanic eruptions must be invoked or answered in order to

challenge the role of carbon dioxide forcing in the climate system. That presumption

is illogical. My basic view and research interest about carbon dioxide and the ongoing search for the right tool for modeling aspects of the Earth’s climate system can

be briefly summarized by my answers to Questions No. 19, 25, 26, 27 and perhaps

20.

As to your specific question on distinguishing a natural variation (either internally generated or externally introduced by solar variation or volcanic eruption)

from a climate change by anthropogenic factors like land cover changes or carbon

dioxide at the local to regional level, there is possibly a somewhat surprising answer. If one wish to single out the potential effects of man-made carbon dioxide

against other natural and anthropogenic factors as hinted by your question, then

the answer is clear—the CO2 effect is expected to be small in the sense that its potential signals will be likely be overwhelmed when compared with expected effects

by other factors. It is a scientific fact that the signal of CO2 on the climate may

be expected only over a very long time baseline and over a rather large areal extent.

For example, Zhao and Dirmeyer (2003, COLA Technical Report No. 150; available

at http://grads.iges.org/pubs/tech.html), in their modeling experiments that attempt to account for the realistic effects of land cover changes, sea surface temperature changes and for the role of added atmospheric CO2, found that

‘‘[w]hen observed CO2 concentrations are specified in the model across the 18-

year period, . . . we do not find a substantially larger warming trend than in

CTL [with no change in CO2 concentration], although some small increase is

found. The weak impact of atmospheric CO2 changes may be due to the small

changes in specified CO2 during the model simulation compared to the doubling

CO2 simulation, or the short length of the integrations. It is clear that the relatively strong SST [sea surface temperature] influence in this climate model is

the driver of the [observed] warming.’’

Please also consider the point made by Lindzen (2002) under Question No. 8 above

concerning the difficulties in linking the observed warming trend of the deep ocean

(without challenging the quality and error of those deep ocean temperature data)
170

to anthropogenic CO2 forcing. Finally, I wish to note that Mickley et al. (2004, Journal of Geophysical Research, vol. 109, D05106) managed to use climate model simulations results to demonstrate ‘‘the limitations in the use of radiative forcing as

a measure of relative importance of greenhouse gases to climate change. . . . While

on a global scale CO2 appears to be a more effective ‘global warmer’ than tropospheric ozone per unit forcing, regional sensitivities to increase ozone may lead to

strong climate responses on a regional scale.’’

Question 31. How does your recent article relate to your assignments at the Harvard Smithsonian Observatory? Is paleoclimate part of the task of this observatory?

Response. The publications of Soon et al. (2003) or Soon et al. (2004) are possible

because of research grants that I and my collaborators obtained through competitive

proposals to several research funding sources. I am a trust-fund employee at the

Harvard-Smithsonian Center for Astrophysics and the support of my position and

research work here is mainly through my own research initiative and proposal application. The scientific learning about paleoclimatic reconstruction presented in

Soon et al. (2003) is related to my research interest in the mechanisms of sun-climate relation, especially for relevant physical pathways and processes on

multidecadal and centennial time scales. Additional fruit of my independent research and labor in the area of sun-climate physics, funded or unfunded, is exemplified by the March 2004 book ‘‘The Maunder Minimum and The Variable Sun-Earth

Connection’’ (see http://www.wspc.com/books/physics/5199.html) by W. Soon and

S. Yaskell (published by World Scientific Publishing Company). It might also be instructive to note that paleoclimate researchers have been speculating about longterm variability of the sun as the cause of centennial- to millennial-scale variability

seen in their proxy records.

Question 32. In your testimony, you said that ‘‘climate change is part of nature.’’

Please describe what you meant, since obviously, climate change have occurred due,

in part, to changes in various forcings, such as solar, continental drift, atmospheric

composition, asteroid impacts, etc. rather than being just completely random events.

Could you provide estimates of how large you consider future forcings might be and

how big the climate change they might cause could be?

Response. In this occasion, I am referring to the fact that any change or variability in climate is most likely a rule, rather than the exception, of the climate system. But I was not speaking about or trying to imply the factors of change, either

naturally produced or man-made. I apologize for any potential confusion. It is certainly reasonable to suggest that those climatic changes may arise from ‘‘forcings’’

but it would be unwise to rule out internally generated manifestations of climatic

variables that could be purely stochastic in origin. I would strongly recommend the

pedagogical discussion by Professor Carl Wunsch of MIT in Wunsch (1992, Oceanography, vol. 5, 99–106) and Wunsch (2004, ‘‘Quantitative estimate of the

Milankovitch-forced contribution to observed Quaternary climate change’’, working

manuscript downloadable from http://puddle.mit.edu/∼cwunsch/).

I cannot speculate on future climate forcings and resultant climatic changes because I found no basis for doing so.

Question 33. Please provide a comparable estimate, with some supporting examples from the past, of how big you think the decadal (or 50-year if you prefer)

change in the hemispheric/global climate could be due to natural variability? If you

prefer to focus on the regional scale change, could you provide an indication of any

expected change in the degree of regional variability about the hemispheric and

global values, and what the mechanism for this might be?

Response. This question seems a related question trying to get at a quantitative

comparison of how large natural climate variability on regional or hemispheric scale

can be under the shadow of expected future changes. Again, with no intention to

devalue this interesting question, I do not have sufficient knowledge nor ability to

venture such an estimate. In fact, I would go so far to say that if the estimates of

variability for both the past and future are known within a reasonable range of uncertainties, then the actual scientific research program to address questions about

the role of added carbon dioxide no longer require further funding or execution since

we have obtained all the relevant answers. But you may have judged from my answers given throughout this Q&A that much remains to be quantified and understood and the hard scientific research must continue.

Question 34. Please explain the scientific basis for your testimony that ‘‘one

should expect the CO2 greenhouse effect to work its way downward toward the surface.’’

Response. Co-answer to this question is given under Question No. 35.
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3Such a study should also be consistently challenged by the discussion under question No.

20 about the adequacy of studying responses from a combination of incomp;ete forcings—

through my primary purpose here is to illustrate the theoretical expectation of CO2 forcing deriving from state-of-the-art climate models.

Question 35. Do you believe that there is greater greenhouse trapping of energy

in the troposphere than at the surface and that the atmosphere has a low heat capacity? If so, how big is this temperature difference?

Response. It is broadly agreed and assumed that carbon dioxide, when released

into the air, has a tendency to get mixed up quickly and so is distributed widely

through out the whole column of the atmosphere. The air near the surface is already

dense and moist, so addition of more carbon dioxide will introduce very little imbalance of radiation energy budget there. In contrast adding more carbon dioxide to

the thinner and drier air of the troposphere will cause a chain of noticeable effects.

First, the presence of more carbon dioxide in the uppermost part of the atmosphere

will cause more infrared radiation to escape into space because there are more carbon dioxide molecules to channel this infrared radiation upward and outward

unhindered. Part of that infrared radiation is also being emitted downward to the

lower parts of the atmosphere and the surface where it is reabsorbed by carbon dioxide and the thicker air there. The layer of air at the lower and middle troposphere, being more in direct contact with this down-welling radiation, is expected

to heat more than air near the surface. Thus, adding more carbon dioxide to the

atmosphere should cause more warming of the air around the height of two to seven

kilometers. (Please consider for example the discussion by Kaser et al. (2004) under

Question No. 8 about the ineffectiveness of an added longwave radiation from a direct addition of atmospheric CO2 or atmospheric temperature change in explaining

the modern retreat of glaciers at Kilimanjaro.) In other words, the clearest impact

of the carbon dioxide greenhouse effect should manifest itself in the lower- and midtroposphere rather than near the earth’s surface. Here, I am mostly speaking on the

basis of expectation from pure radiative forcing considerations.

Such a qualitative description is not complete, even though that is roughly what

was modeled in the most sophisticated general circulation models (see e.g., Chase

et al., 2004, Climate Research, vol. 25, 185–190), because it misses the key roles of

atmospheric convection and waves as well as all the important hydrologic processes

(please see e.g., Neelin et al., 2003, Geophysical Research Letters, vol. 30 (no. 24),

2275 and consider additional remarks about water vapor and atmospheric convection under Question No. 25 as well as discussion on climate forcing factors and climate response sensitivities under Question No. 20). Some theoretical proposals expect a warming of the surface relative to the low- and mid-troposphere because of

nonlinear climate dynamics (Corti et al., 1999, Nature, 398, 799–802). That expectation is because of the differential surface response with the pattern of Cold Ocean

and Warm Land (COWL) that becomes increasingly unimportant with distance

away from the surface (rather than just the difference in heat capacity mentioned

in your question) [see Soon et al., 2001 for additional discussion]. Nevertheless, no

GCM has yet incorporated such an idea into an operationally robust simulation of

the climate system response to greenhouse effects from added CO2. In the latest

‘‘global warming’’ work, Neelin et al. (2003), for example, still distinctly differentiate

between mechanisms for tropical precipitation that are initiated through CO2 warming of the troposphere and through El Nin ̃ o warming rooted in oceanic surface temperature and subsurface thermocline dynamics. (Further note that their model experiments [see Figure 2b+2c and 10b+10c of Chou and Neelin, 2004, ‘‘Mechanisms

of global warming impacts on regional tropical precipitation’’ in preparation for

Journal of Climate; available at http://www.atmos.ucla.edu/?csi/REF/] also clearly

shown that the troposphere warmed significantly more than surface with the doubling of atmospheric CO2 as discussed by Chase et al. 2004 below.)

But it is worth noticing that the current global observation shows that, at least

over the 1979–2003 interval, the lower tropospheric temperatures are not warming

as fast as the surface temperatures (see Christy et al. 2003, Journal of Atmospheric

and Oceanic Technology, vol. 20, 613–629; for additional confidence on the results

derived by the University of Alabama-Huntsville group, please see Christy and Norris, 2004, Geophysical Research Letters, vol. 31, L06211). This observed fact is in

contradiction to the accelerated warming of the mid and upper troposphere relative

to surface simulated in current models (Chase et al. 2004). Chase et al. (2004) arrives at the following conclusions, upon examining results from 4 climate models in

both unforced scenarios and scenarios forced with increased atmospheric greenhouse

gases and the direct aerosol effect3:
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• ‘‘Model simulations of the period representative of the greenhouse-gas and

aerosol forcing for 1979–2000 generally show a greatly accelerated and detectable warming at 500 mb relative to the surface (a 0.06° C decade¥1increase).

• Considering all possible simulated 22 yr trends under anthropogenic forcing, a strong surface warming was highly likely to be accompanied by accelerated warming at 500 mb [i.e., 987 out of 1018 periods or 97 percent of the cases

had a larger warming at 500 mb than at the surface] with no change in likelihood as forcings increased over time.

• In simulated periods where the surface warmed more quickly than 500 mb,

there was never a case [emphasis added] in which the 500 mb temperature did

not also warm at a large fraction of the surface warming. A 30 percent acceleration at the surface was the maximum simulated as compared with an observed

acceleration factor of at least 400 percent the mid-troposphere trend.

• In cases where there was a strong surface warming and the surface

warmed more quickly than at 500 mb in the forced experiments, there was

never a case in which the 500 mb-level temperatures did not register a statistically significant (p< 0.1) trend (i.e., a trend detectable with a simple linear regression model). The minimum p value of approximately 0.08 occurred in the

single case in which the significance was not greater than 99 percent.

• It was more likely that surface warmed relative to the mid-troposphere

under control simulations than under forced simulations.

• At no time, in any model realization, forced or unforced, did any model simulate the presently observed situation of a large and highly significant surface

warming accompanied with no warming whatsoever aloft.’’ (p. 189)

Question 36. The grants that are described as supporting your analysis seem to

have much more to do with the sun or unrelated pattern recognition that with climate history (Air Force Office of Scientific Research-Grant AF49620–02–1–0194;

American Petroleum Institute-Grants 01–0000–4579 and 2002–100413; NASA-Grant

NAG–7635; and NOAA-Grant NA96GP0448). Could you please describe how much

funding you received and used in support of this study, all of the sources and the

duration of that funding, and the relevance of those grant topics to the article?

Response. All sources of funding for my and my colleagues’ research efforts that

resulted in the publication of Soon and Baliunas (2003) and Soon et al. (2003) were

openly acknowledged. In other words, all sources of funding were disclosed in the

manuscripts when they were submitted for publication; all sources of funding were

also disclosed to readers in the printed journal articles. I am not the principal investigator for some of the grants we received (e.g., the NOAA grant was awarded to

Professor David Legates), so I am not in the privilege position to provide exact

quantitative numbers. But throughout the 2001–2003 research interval in which our

work was carried out, the funding we received from the American Petroleum Institute was a small fraction of the funding we received from governmental research

grants.

The primary theme of my research interest is on physical mechanisms of the sunclimate relationship. This is why researching into the detailed patterns of local and

regional climate variability as published in Soon et al. (2003) is directly relevant to

that goal. Please also consider my research position listed under Question No. 31

above.

Question 37. Have you been hired by or employed by or received grants from organizations that have taken advocacy positions with respect to the Kyoto Protocol, the

U.N. Framework Convention on Climate Change, or legislation before the U.S. Congress that would affect greenhouse gas emissions? If so, please identify those organizations.

Response. I have not knowingly been hired by, nor employed by, nor received

grants from any such organizations described in this question.

Question 38. Please describe the peer review process that took place with respect

to your nearly identical articles published both in Climate Research and in Energy

and Environment, including the number of reviewers and the general content of the

reviewers’ suggested edits, criticisms or improvements.

Response. The Climate Research paper (Soon and Baliunas, 2003, Climate Research, vol. 23, 89–110) was submitted for publication and went through a routine

peer-review process and was eventually approved for publication. The main content

of the review was to propose: (a) reorganizing of materials including elimination of

discussions on ENSO and GCMs; (b) removing ‘‘tone’’ problems by eliminating criticisms of previous EOF and superposition analyses; (c) reducing quotes especially

those by Hubert Horace Lamb to improve readability; and (d) reviewing changes in

each region with same thoroughness. The July 3, 2003’s email (as Attachment I
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below) from the director of Inter-Research, Otto Kinne, who publishes Climate Research is enclosed below to confirm that the review process was fairly rigorous and

all parties involved had carried out their roles and duties in this time-honored system properly.

The extended and more complete paper by Soon et al. (2003, Energy & Environment, vol. 14, 233–296) was submitted to Energy & Environment for consideration

together with the accepted Climate Research manuscript. Energy & Environment’s

editorial decision was to send our manuscript for review, and after acceptance, include in its editorial in Energy & Environment, volume 14, issues 2&3, a footnote

referring to the Climate Research paper.

Finally, we wish to correct that the false impression introduced by Professor

Mann both during the testimony and in public media that his attack on the papers

by Soon and Baliunas (2003) and Soon et al. (2003), in a FORUM article in the

American Geophysical Union Eos newspaper (Mann et al., 2003, Eos, vol. 84, 256–

258), were either rigorously peer-reviewed or represented widespread view of the

community. Contrary to Professor Mann’s public statements, a FORUM article in

Eos is said to be only stating ‘‘a personal point of view’’ (http://www.agu.org/pubs/

eos—guidelines.html#authors). Whatever peer-reviewing that was done did not include soliciting comments from the authors of the papers being criticized. We first

learned of this FORUM article from the AGU’s press release No. 03–19 ‘‘Leading

Climate Scientists Reaffirm View that Late 20th Century Warming Was Unusual

and Resulted From Human Activity’’ (http://www.agu.org/sci—soc/prrl/

prrl0319.html). See Soon et al. (2003b, Eos, vol. 84 (44), 473–476) for our own response to the Mann et al. FORUM article.

STATEMENT OF PROFESSOR MICHAEL E. MANN, DEPARTMENT OF ENVIRONMENTAL

SERVICES, UNIVERSITY OF VIRGINIA

My name is Michael Mann. I am a professor in the Department of Environmental

Sciences at the University of Virginia. My research involves the use of climate models, the analysis of empirical climate data, and statistical methods for comparing observations and model predictions. One area of active current research of mine involves the analysis of climate ‘‘proxy’’ records (that is, natural archives of information which record past climate conditions by their biological, physical, or chemical

nature). These data are used to reconstruct patterns of climate variability prior to

the period of the past century or so during which widespread instrumental climate

records are available. A primary focus of this research is deducing the long-term behavior of the climate system and the roles of various potential agents of climate

change, both natural and human.

I was a Lead Author of the ‘‘Observed Climate Variability and Change’’ chapter

of the Intergovernmental Panel on Climate Change (IPCC) Third Scientific Assessment Report and a scientific contributor for several other chapters of the report. I

am the current organizing committee chair for the National Academy of Sciences

‘Frontiers of Science’ and have served as a committee member or advisor for other

National Academy of Sciences panels related to climate change. I have served as

editor for the ‘Journal of Climate’ of the American Meteorological Society. I’m a

member of the advisory panel for the National Oceanographic and Atmospheric Administrations’ Climate Change Data and Detection Program, and a member of numerous other international and U.S. scientific working groups, panels and steering

committees. I have co-authored more than 60 peer-reviewed articles and book chapters on diverse topics within the fields of climatology and paleoclimatology. Honors

I have received include selection in 2002 as one of the 50 leading visionaries in

Science and Technology by Scientific American magazine, the outstanding scientific

publication award for 2000 from the National Oceanographic and Atmospheric Administration, and citation by the Institute for Scientific Information (ISI) for notable

recognition of my peer-reviewed research by fellow scientists.

In my testimony here today, I will explain: (1) How mainstream climate researchers have come to the conclusion that late-20th century warmth is unprecedented in

a very long-term context, and that this warmth is likely related to the activity of

human beings. (2) Why a pair of recent articles challenging these conclusions by astronomer Willie Soon and his co-authors are fundamentally unsound.

CLIMATE HISTORY AND ITS IMPLICATIONS

Evidence from paleoclimatic sources overwhelmingly supports the conclusion that

late-20th century hemispheric-scale warmth was unprecedented over at least the

past millennium and probably the past two millennia or longer.
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Modeling and statistical studies indicate that such anomalous warmth cannot be

explained by natural factors but, instead, requires significant anthropogenic (that is,

‘human’) influences during the 20th century. Such a conclusion is the indisputable

consensus of the community of scientists actively involved in the research of climate

variability and its causes. This conclusion is embraced by the position statement on

‘‘Climate Change and Greenhouse Gases’’ of the American Geophysical Union (AGU)

which states that there is a compelling basis for concern over future climate

changes, including increases in global-mean surface temperatures, due to increased

concentrations of greenhouse gases, primarily from fossil-fuel burning. This is also

the conclusions of the 2001 report of the Intergovernmental Panel on Climate

Change (IPCC), affirmed by a National Academy of Sciences report solicited by the

Bush administration in 2001 which stated, ‘‘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.’’

THE MAINSTREAM SCIENTIFIC VIEWPOINT

Human beings have influenced modern climate through changes in greenhouse

gas concentrations, the production of industrial aerosols, and altered patterns of

land-use. By studying both the record of ancient climate variability and the factors

that may have influenced it, we can establish how and why the climate system varied naturally, prior to any large-scale anthropogenic impacts. Large changes in climate certainly occurred in the distant past. If we look 60 million years back in time,

Dinosaurs were roaming the polar regions of the earth, and the globe was almost

certainly warmer than today. Carbon dioxide levels were probably about double

their current level, and had slowly attained such high levels due to changes in the

arrangements of the continents (‘plate tectonics’) which influence the outgassing of

carbon dioxide from the solid earth and thus, atmospheric greenhouse gas concentrations. These changes occur on timescales of tens of millions of years. 10,000

years ago, large ice sheets existed over North America due to natural changes that

occur in the earth’s orbit on timescales of tens of thousands of years. Trying to study

distant past climates for insights into modern natural climate variability is hampered by the fact that the basic external constraints on the system (the continental

arrangement, the geometry of the earth’s astronomical orbit, the presence of continental ice sheets—what we call the ‘boundary conditions’) were significantly different from today. Focusing on the evolution of climate in the centuries leading up

to the 20th century provides a perspective on the natural variability of the climate

prior to the period during which large-scale human influence is likely to have occurred, yet modern enough that the basic boundary conditions on the climate system

were otherwise the same. This provides us, in essence, a ‘control’ for diagnosing

whether or not recent climate changes are indeed unusual.

Instrumental data for use in computing global mean surface temperatures are

only available for about the past 150 years. Estimates of surface temperature

changes prior to the 20th century must make use of historical documents and natural archives or ‘‘proxy’’ indicators, such as tree rings, corals, ice cores and lake

sediments, to reconstruct the patterns of past climate change. Due to the paucity

of data in the Southern Hemisphere, recent studies have emphasized the reconstruction of Northern Hemisphere rather than global mean temperatures. A number of

independent reconstructions of the average temperature of the Northern Hemisphere support the conclusion that the hemispheric warmth of the late 20th century

(i.e., the past few decades) is likely unprecedented over at least the past millennium. Preliminary evidence suggests that such a conclusion may well hold for at

least the past two millennia, though more work, requiring the development of a

more complete set of reliable proxy records spanning the past few millennia, are

necessary to further decrease the uncertainties. Climate model simulations employing estimates of natural and anthropogenic radiative forcing changes agree well

with the proxy-based reconstructions (Figure 1). The simulations, moreover, show

that it is not possible to explain the anomalous late 20th century warmth without

the contribution from anthropogenic influences. Such consensus findings are expressed in the recently published article co-authored by myself and 12 other leading

climate scientists from the United States and Britain that appeared recently in the

journal ‘Eos’, the official transactions of the American Geophysical Union, the largest professional society in the field.

FLAWS IN A RECENT STUDY DISPUTING THE SCIENTIFIC CONCENSUS

Two deeply flawed (and nearly identical) recent papers by astronomers Soon and

Baliunas (one of them with some additional co-authors—both henceforth referred to
175

as ‘SB’) have been used to challenge the scientific consensus. I outline the 3 most

basic problems with their papers here:

(1) In drawing conclusions regarding past regional temperature changes from

proxy records, it is essential to assess to make sure that the proxy data are indicators of temperature and not precipitation or drought. SB make this fundamental

error when they cite evidence of either ‘warm’, ‘wet’, or ‘dry’ regional conditions as

being in support of an exceptional ‘Medieval Warm Period’ or ‘MWP’. Their criterion,

ad absurdum, could be used to define any period of climate as ‘warm’ or ‘cold’. Experienced paleoclimate researchers know that they must first establish the existence

of a temperature signal in a proxy record before using it to evaluate past temperature changes (Figure A1).

(2) It is essential to distinguish between regional temperature changes and truly

hemispheric or global changes. SB do not make this essential distinction. The

wavelike character of weather (i.e., the day-to-day wiggles of the Jet Stream) ensures that certain regions tend to warm when other regions cool. This past winter

is a case in point. January was about 2° C below normal on the east coast of the

U.S., but about 4° C above normal over much of the west. Utah, Nevada and parts

of California and Alaska had the warmest January on record (the change in location

of the Iditarod dog sled race was a casualty of the Alaskan winter warmth!). The

average temperature over the entire U.S. was about 1° C above normal, much less

warm than for the western U.S., and of the opposite sign of the eastern U.S.

In a similar manner, average global or hemispheric temperature variations on

longer timescales tend to be much smaller in magnitude than those for particular

regions, due to the tendency for a cancellation of warm and cold conditions in different regions. While relative warmth during the 10th–12th centuries, and cool conditions during the 15th-early 20th centuries are evident from reconstructions and

model simulations of the average temperature of the Northern Hemisphere (Figure

1), the specific periods of cold and warmth naturally differ from region to region

(Figure A2). The notion of an unusually cold 17th century ‘Little Ice Age’, for example, arose in a European historical context. What makes the late 20th century

unique is the simultaneous warmth indicated by nearly all long-term records (Figure A2), leading to the anomalous warmth evident during this period in Northern

Hemisphere average temperatures (Figure 1).

(3) It is essential, in forming a climate reconstruction, to carefully define a base

period for modern conditions against which past conditions may be quantitatively

compared. The concensus conclusion that late–20th century mean warmth likely exceeds that of any time during the past millennium for the Northern Hemisphere,
176

is based on a careful comparison of temperatures during the most recent decades

with reconstructions of past temperatures, taking into account the uncertainties in

those reconstructions. As it is only the past few decades during which Northern

Hemisphere temperatures have exceeded the bounds of natural variability, any

analysis such as SB that compares past temperatures only to early or mid-20th century conditions, or interprets past temperatures using proxy information not capable

of resolving decadal trends cannot address the issue of whether or not late-20th century warmth is anomalous in a long-term context.

CONCLUSIONS

The concentration of greenhouse gases in the atmosphere is higher than at any

time in at least the last 400,000 years, and, it increasingly now appears, probably

many millions of years. This increase is undeniably due to the activity of human

beings through fossil fuel burning. Late 20th century warming is unprecedented in

modern climate history at hemispheric scales. This is almost certainly a result of

the dramatic increase in greenhouse gas concentrations due human activity. The latest model-based projections indicate a global mean temperature increase of 0.6 to

2.2° C (1° C to 4°F) relative to 1990 levels by the mid-20th century. While these estimates are uncertain, even the lower value would take us well beyond any previous

levels of warmth seen over at least the past couple millennia. The magnitude of

warmth, but perhaps more importantly, the unprecedented rate of this warming, is

cause for concern.
177
178

RESPONSE BY MICHAEL MANN TO ADDITIONAL QUESTIONS BY SENATOR INHOFE

Question 1. You have used the term ‘‘climate scientist’’ to distinguish certain individuals. What, in your view, does it take for one to earn the title ‘‘climate scientist’’?

What specific credentials, or the lack thereof, would lead you to refuse to recognize

someone as a ‘‘climates scientist’’?

Response. The term ‘‘climate scientist’’ is used, in my experience, to describe an

individual with specific training in oceanographic, atmospheric, and coupled oceanatmosphere processes relevant to understanding climate variability and the behavior of the climate system. An individual might obtain this training through either

an advanced degree in those areas of study, or through years of research in those

areas associated with numerous publications in the peer-reviewed climate literature

such as ‘‘Journal of Geophysical Research—Atmospheres’’, ‘‘Journal of Geophysical

Research-Oceans’’, ‘‘Climate Dynamics’’, ‘‘The Holocene’’, ‘‘Geophysical Research Letters’’, ‘‘Paleoceanography’’ (or publication of climate papers in leading international

science journals such as ‘‘Nature’’ and ‘‘Science’’). I would not, for example, consider

scientists with advanced degrees in Astronomy, Astrophysics, or Physics who have

published primarily in those areas, as ‘‘climate scientists’’—nor do I believe would

most of my colleagues in the climate research community. In addition to training

and publishing in a field, leading scientists would normally be expected to be actively interacting and collaborating in studies with colleagues and ensuring their

understanding of cutting edge science through attendance and active participation

in meetings convened by the leading professional societies and organizations.

Question 2. Your work and testimony contends that the Little Ice Age was not

global, but restricted to only portions of Europe. A forthcoming article by Shindell

et al. (Shindell, D.T. et al., 2003: Volcanic and solar forcing of climate change during

the pre-industrial era. Journal of Climate, in press), however, indicates the Little

Ice Age could have resulted from a combination of solar and volcanic forcing. Do you

agree with these conclusions from Shindell et al.? If so, how can solar and volcanic

forcings generate climatic effects that are not observed across the entire hemisphere?

Response. The statement is incorrect. I never testified that the ‘‘Little Ice Age was

. . . restricted to only portions of Europe’’.

It should first be noted that many paleoclimatologists have questioned the utility

of terms such as ‘‘Little Ice Age’’ and ‘‘Medieval Warm Period’’ which provide misleading descriptions of past climate changes in many regions. There is a complex

pattern of climate variability in past centuries, and the lack of evidence for synchronous temperature variations worldwide in past centuries [e.g. Bradley, R.S., and

P.D. Jones, ‘‘Little Ice Age’’ summer temperature variations: their nature and relevance to recent global warming trends, The Holocene, 3, 367–376, 1993; Hughes,

M.K., and H.F. Diaz, Was there a ‘medieval warm period’, and if so, where and

when, Climatic Change, 26, 109–142, 1994]. The cited paper by Shindell et al (2003),

of which I am a co-author, is fully consistent with such findings. The paper, rather

than demonstrating globally uniform patterns of warming or cooling in past centuries, shows that surface temperature changes were dominated by regional overprints associated with the response of the ‘‘North Atlantic Oscillation’’ atmospheric

circulation pattern to radiative forcing. This response leads to a pattern of cooling

during the 17th/18th centuries in certain regions (not just Europe, but many regions

throughout the Northern Hemisphere extratropics) and warming in other regions.

The paper shows that this pattern of warming and cooling closely resembles the pattern of surface temperature change during that interval reconstructed by Mann and

colleagues (MBH98). It is worth noting, moreover, that the tropical Pacific seems to

have been in a warmer, rather than a ‘‘colder’’ state, during the conventionally defined ‘‘Little Ice Age’’ [Cobb, K.M., Charles, C.D., Edwards, R.L., Cheng, H., &

Kastner, M. El Nin ̃ o-Southern Oscillation and tropical Pacific climate during the

last millennium, Nature 424, 271–276 (2003). Climate dynamists understand the

importance of such phenomena in understanding the highly variable pattern of surface temperature changes in past centuries, and rarely, if ever, argue for the existence of globally uniform or synchronous temperature change in past centuries. The

response of the climate to solar and volcanic radiative forcing is known to involves

dynamical responses associated with regionally differentiated temperature trends

that overprint far smaller global mean responses. This contrasts strongly with the

response of the climate to anthropogenic climate forcing, for which the integrated

global mean radiative forcing is considerably greater, and the associated large-scale

warming typically rises above the regional variability.

Question 3. That same paper finds ‘‘long-term regional response to solar forcing

[that] greatly exceeds unforced variability . . . and produces climateanomalies simi-
179

lar to those seen during the Little Ice Age. Thus, longterm regional changes during

the pre-industrial [era] appear to havebeen dominated by solar forcing.’’ You further

state that ‘‘For the few centuries prior to the industrial era, however, externally

driven climate change is thought to have been forced primarily by only two factors:

variation in solar output and volcanic eruptions . . . These forcings likely played

a large role in the so-called Medieval Warm Period (MWP) and Little Ice Age (LIA)

epochs of the last millennium, which saw significant climate changes on at least regional scales . . .’’ You then define ‘‘regional’’ ‘‘to mean continental in scale . . .’’

Do you claim that total solar irradiance change is the only solar forcing mechanism

that has any significant climate effect? List your formal training in, plus courses

you have taught, in solar physics. Do you agree with the paper’s claim that the

MWP and LIA exist on regional scales, in accordance with climate experts like R.

Bryson and H.H. Lamb, starting with their work in the 1960’s, and recently updated

in summary in Soon et al. (2003)?

Response. Expertise in ‘‘solar physics’’ is not the expertise required to evaluate

what is happening to the Earth’s climate—what matters are the changes in solar

radiation at the top of the atmosphere and then down through it. As is made clear

in our paper, we are considering not only ‘‘total solar irradiance’’ but also its spectral distribution. Indeed, because much of the change in solar radiation occurs in

UV wavelengths, induced changes in stratospheric ozone can be lead to significant

changes in atmospheric circulation in the troposphere. The model simulations indicate that such atmospheric circulation changes can, acting with other factors, lead

to regional variations in the climate such as were observed over the last millennium. As a co-author of this paper, I of course, agree with its findings. However,

the inference that this paper confirms the work of Soon et al. (2003) is very mistaken.

With respect to my training, teaching, I would encourage that my Curriculum

Vitae, which I have provided separately, be included in the record to be compared

to those of the other witnesses with respect to relevant expertise and standing in

the climate research community.

Question 4. In your testimony, you stated that you hold the ‘‘mainstream’’ view

with respect to climate theory of air temperature trends over the past two millennia.

Provide supporting citations in the refereed scientific literature that are not authored or co-authored by you or your colleagues, collaborators, students or former

students, or associates (i.e., Phil Jones, Ray Bradley, Malcolm Hughes), where others hold this Emainstream1 view.

Response. The statement once again mischaracterizes my comments. As there is

only one reconstruction of Northern Hemisphere annual mean temperature over the

past two millennia, published only recently by Phil Jones and myself, it is hardly

meaningful to discuss whether ‘‘other studies’’ support this finding. The peer-review

and publication process typically unfolds on timescales of a year or longer, not

months. Any careful reading of my comments would reveal that I was not referring

to this one specific reconstruction in the comments I made characterizing what I believe to be the mainstream viewpoint of the climate research community. This review, as discussed in my testimony, refers rather to the widespread evidence that

late 20th century warmth is unprecedented in a long-term context, anywhere from

the past several centuries to nearly the past two millennia, depending on the timeframe of the particular study.

Second, the description of ‘‘collaborators, associates, former students’’, depending

on how interpreted, is so broad a category as to include just about every leading

scientist in the field. The following publications all come to the same conclusion that

late 20th century Northern Hemisphere warmth is anomalous in a long-term context:

• Bauer, E., Claussen, M., Brovkin, V., Assessing climate forcings of the earth

system for the past millennium, Geophys. Res. Lett., 30 (6), 1276, doi: 10.1029/

2002GL016639, 2003.

• Bertrand C., Loutre M.F., Crucifix M., Berger A., Climate of the Last millennium: a sensitivity study. Tellus, 54(A), 221–244, 2002.

• Bradley, R.S., and P.D. Jones, ‘‘Little Ice Age’’ summer temperature variations:

their nature and relevance to recent global warming trends, The Holocene, 3 (4),

367–376, 1993.

• Bradley, R.S., Briffa, K.R., Crowley, T.J., Hughes, M.K., Jones, P.D, Mann,

M.E., Scope of Medieval Warming, Science, 292, 2011–2012, 2001.

• Bradley, R.S., M.K.Hughes and H.F. Diaz., Climate in Medieval Time. Science,

302, 404–405, 2003.

• Pollack, H.N., S. Huang, and P.-Y. Shen, Climate Change Record in Subsurface

Temperatures: A Global Perspective, Science, 282, 279–281, 1998.
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• Briffa, K.R., T.J. Osborn, F.H. Schweingruber, I.C. Harris, P.D. Jones, S.G.

Shiyatov, S.G. and E.A. Vaganov, Low-frequency temperature variations from a

northern tree-ring density network. J. Geophys. Res., 106, 2929–2941, 2001.

• Crowley, T.J., Causes of Climate Change Over the Past 1000 Years, Science,

289, 270–277, 2000.

• Crowley, T.J., and T. Lowery, How Warm Was the Medieval Warm Period,

Ambio, 29, 51–54, 2000.

• Gerber, S., F. Joos, P. Bru ̈ gger, T. F. Stocker, M. E. Mann, S. Sitch, and M.

Scholze, Constraining temperature variations over the last millennium by comparing simulated and observed atmospheric CO2, Climate Dynamics, 20, 281–299,

2003.

• Hegerl, G.C., T.J. Crowley, S.K. Baum, K-Y. Kim, and W. T. Hyde, Detection

of volcanic, solar and greenhouse gas signals in paleo-reconstructions of Northern

Hemispheric temperature. Geophys. Res. Lett., 30 (5), doi: 10.1029/2002GL016635,

2003.

• Huang, S., H. N.Pollack and P.-Y. Shen, Temperature Trends Over the Past

Five Centuries Reconstructed from Borehole Temperature, Nature 403, 756–758,

2000.

• Jones, P.D., M. New, D.E. Parker, S. Martin, and I.G. Rigor, 1999: Surface air

temperature and its changes over the past 150 years. Reviews of Geophysics 37,

173–199.

• Jones, P.D., T.J. Osborn, and K.B. Briffa, The Evolution of Climate Over the

Last Millennium, Science, 292, 662–667, 2001.

• Overpeck, J., K. Hughen, D. Hardy, R. Bradley, R. Case, M. Douglas, B. Finney,

K. Gajewski, G. Jacoby, A. Jennings, S. Lamoureux, A. Lasca, G.M.J. Moore, M.

Retelle, S. Smith, A. Wolfe, and G. Zielinski, Arctic Environmental Change of the

Last Four Centuries, Science, 278, 1251–1256, 1997.

• Pollack, H.N., S. Huang, and P.-Y. Shen, Climate Change Record in Subsurface

Temperatures: A Global Perspective, Science, 282, 279–281, 1998.

Question 5. Your work has been characterized as ‘‘global’’ in several venues, including the National Assessment. Is that a fair characterization, or are those

sources confused by your use of Northern and Southern Hemisphere proxies in your

Northern Hemisphere reconstruction? Can you explain why the National Assessment did not include error bars on your temperature reconstruction?

Response. The proxy records on which our work is based represent conditions over

much of the Northern Hemisphere and a small fraction of the Southern Hemisphere.

While in any given year there can be some difference in the anomalies in the two

hemispheres, the instrumental record indicates that over periods of a few decades

or more, the anomalies in the two hemispheres are quite similar because of the thermodynamic and dynamic coupling between them. Thus, the major features of the

temperature record, and in particular the unusual 20th century warming, are similar in the two hemispheres and thus global features. It was this aspect of the record

to which the text of the National Assessment report refers in presenting the overall

significance of our study, and the report is correct in suggesting that the 20th century warming is global in nature. The caption for Figure 2 of Chapter 1 in the Foundation report (page 22 and page 544) states that ‘‘Although this record comes mostly

from the Northern Hemisphere, it is likely to be a good approximation to the global

anomaly based on comparisons of recent patterns of temperature fluctuations.’’ This

accurately reflects the situation. In the Overview report (page 13), although the figure title says ‘‘Global CO2 and Temperature Change,’’ the caption next to the figure

says ‘‘Records of Northern Hemisphere surface temperatures, CO2 concentrations,

and carbon emissions show a close correlation. Temperature change: reconstruction

of annual-average Northern Hemisphere surface air temperatures derived from historical records, tree rings, and corals (blue), and air temperatures directly measured

(purple).’’ This quite clearly makes the point this is mainly a Northern Hemisphere

temperature record.

With respect to the question about the presentation of the figure, it is misleading

to imply that the term ‘‘error bars’’ indicates that the central line is off by this

amount—rather the limits mean that there is only 1 chance in 20 that the actual

value is outside this range. That is, what we are showing is the likely range within

which the anomaly lies, with there being a 95 percent chance the value is within

this range. The line that we present in many of our figures, and that was presented

in the National Assessment report, is the most likely value within this range (rather

a natural choice to display in explaining a complex issue to the public). In looking

at the National Assessment report, the caption for Figure 2 of Chapter 1 in the

Foundation report (page 22 and page 544) states that ‘‘The error bars for the estimate of the annual-average anomaly increase somewhat going back in time, with
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one standard deviation being about 0.25°F (0.15° C).’’ Quite clearly, the reader interested in investigating the accuracy of the records would followup by reading the

original reference, which is cited in the text.

In that I was not involved in the National Assessment report, the questioner

should consult the authors of that report for any further information or questions.

Question 6. You testified that the late 20th century warming is likely caused

byman-made CO2 forcing on climate; what is your scientific proof for thatclaim

Please detail how you removed the potential effects from other factors including

those of sulfate aerosols, tropospheric and stratospheric ozone, volcanic dust veiling,

black soot, solar particleand wave length-dependent variability, sea ice, land use,

vegetation andother greenhouse gases?

Response. The question inconsistently equates my statement of a ‘‘likely’’ causal

relationship with the standard of ‘‘scientific proof’’. Scientists do not speak in terms

of ‘‘proof’’. We speak in terms of likelihoods and the strength of evidence in support

of a particular hypothesis.

A large number of peer-reviewed scientific studies have been published in the

leading scientific journals such as Nature and Science in the past two decades elucidating the role of natural and anthropogenic factors in observed climate changes.

Physically based models have been developed and validated against observations,

and these models reproduce complex climate phenomena such as El Nin ̃ o. These

same models have been driven with the primary ‘‘external’’ factors that are believed

to govern climate variations on timescales of decades and centuries. These external

factors include natural factors, such as the modest estimated variations in radiative

output of the Sun, which varies by a fraction of a percent over time, variations in

the frequency and intensity of explosive volcanic eruptions, which have a severalyear cooling effect on the climate through the injection of reflective volcanic aerosols

into the stratosphere, and very small changes in the Earth’s orbit relative to the

Sun that occur on multi-century timescales. These external factors also include the

‘‘anthropogenic’’ influences of increased greenhouse gas concentrations due to fossil

fuel burning, changes in the reflective properties of the land surface due to human

land use alterations, and the regional cooling effect of anthropogenic sulphate

aerosols in certain industrial regions. When driven with these factors, these climate

models have demonstrated a striking ability to reproduce observed global and hemispheric temperature trends during the 20th century, as well as longer-term trends

in past centuries as reconstructed from proxy data. Such results have been demonstrated in the following peer-reviewed scientific articles: • Wigley, T.M.L., R.L. Smith, and B.D. Santer, Anthropogenic Influence on the

Autocorrelation Structure of Hemisoheric-Mean Temperatures, Science, 282, 1676–

1680, 1998. • Tett, S.F.B., P.A. Scott, M.R. Allen, W.J. Ingram, and J.F.B. Mitchell, Causes

of Twentieth-Century Temperature Change Near the Earth’s Surface, Nature, 399,

569–572, 1999.

• Hegerl, G.C., P.A. Scott, M.R. Allen, J.F.B. Mitchell, S.F.B. Tett, and U.

Cubasch, Optimal detection and aftribution of climate change: sensitivity of results

to climate model differences, Climate Dynamics, 16, 737–754, 2000.

• Crowley, T.J., Causes of Climate Change Over the Past 1000 Years, Science,

289, 270–277, 2000.

• Stott, P.A., S.F.B. Tett, G.S. Jones, M.R. Allen, J.F.B. Mitchell, and G.J. Jenkins, External Control of 20th Century Temperature by Natural and Anthropogenic

Forcings, Science, 290, 2133–2137, 2001.

• Stott, P.A., S.F.B. Tett, G.S. Jones, M.R. Allen, W.J. Ingram, and J.F.B. Mitchell, Attribution of twentieth century temperature change to natural and anthropogenic causes, Climate Dynamics, 17, 11–21, 2001.

These conclusions, furthermore, were endorsed by the 2001 IPCC scientific working group report (Chapter 12), and the followup National Academy of Sciences report that endorsed most of the key IPCC conclusions.

Question 7. A number of expert studies have produced individual proxy records

that show the existence of a local Medieval Warm Period or Little Ice Age. Such

studies cover a large portion of the globe. How do you reconcile your hemispheric

reconstruction with these individual proxy records?

Response. It is unclear to me what precisely the questioner means by ‘‘a number

of expert studies’’ or how he defines the ‘‘existence’’ of a ‘‘Medieval Warm Period’’

or ‘‘Little Ice Age’’. As discussed in my response to question 2, the regionally and

temporally variable nature of climate changes in past centuries makes such

descriptors of past climate change naive and often useless as a characterization of

past changes. A sampling of some of the longest, high-quality best term proxy temperature estimates over the globe was provided in Figure 2 of the article: Mann,
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M.E., Ammann, C.M., Bradley, R.S., Briffa, K.R., Crowley, T.J., Hughes, M.K.,

Jones, P.D., Oppenheimer, M., Osborn, T.J., Overpeck, J. T., Rutherford, S.,

Trenberth, K.E., Wigley, T.M.L., On Past Temperatures and Anomalous Late 20th

Century Warmth, Eos, 84, 256–258, 2003. This figure demonstrates the lack of evidence for any periods in earlier centuries that are comparable in terms of evidence

for sychronous warmth to the late 20th century. This same conclusion was also demonstrated by the recent article in Science: Bradley, R.S., M.K. Hughes and H.F.

Diaz., Climate in Medieval Time. Science, 302, 404–405, 2003.

Question 8. Do you claim 22 proxies to be a sufficient sample of observations for

reconstructing a Northern Hemisphere temperature? If not, why did you consider

it sufficient for the 1400–1450 interval in your 1998 Nature paper? If you do, there

are 29 proxies that continue to 1984 in the data base you used for your 1998 paper.

Why then did you terminate your temperature reconstruction at 1980? What efforts

have you made to extend the proxy re-constructions up to the present?

Response. The question is wrongly premised. The Mann et al (1998) study made

use of almost 100 proxy series over the interval AD 1400–1450. The question appears to confuse the number of proxy series that was used, with the number of statistical indicators that were used to represent these proxy data. For example, the

70 series that make up the North American International Tree Ring Data Base date

back to 1400, were represented in terms of their leading patterns of variance

through a procedure known as ‘‘Principal Component Analysis’’. These patterns represented, however, a much larger number of underlying data. Most of the proxy

records used in that analysis ended by 1980, limiting the useful upper limit to the

calibration period used. A more recent paper (in press) extends proxy-based hemispheric temperature reconstructions through the mid-1990’s, demonstrating the ability of the reconstruction to capture the accelerated warming evident in the instrumental record since 1980.

Question 9. What are the patterns of temperature change in all proxies after

1980?

Response. It is unclear what is meant by the question. Every proxy series which

extends past 1980 exhibits its own particular pattern. A recent paper (in press), as

referred to in Question No. 8, demonstrates that a composite of proxy temperature

indicators with reliable low-frequency variability that are available through the

mid-1990’s capture the accelerated warming after 1980.

All of the data used in our study have been available since July 2002 on the public ftp site: ftp://holocene.evsc.virginia.edu/pub/MBH98/.

Question 10. Do you have any external (not derived by you) method or data to

provide verification of your temperature reconstruction Please explain.

Response. We used the method of cross-validation to independently demonstrate

the statistical reliability of our reconstructions. This is detailed in MBH98 and

MBH99. We did not derive the method of cross-validation—it is a well established

statistical procedure, detailed in many introductory level statistics textbooks.

Question 11. Are you aware of any errors in your data compilation for MBH98

or MBH99? If so, what are they?

Response. We are not aware of any errors. We are, however, aware of recent spurious claims of such errors by the authors of an article published in the social

science journal ‘‘Energy and Environment’’. These claims have already been widely

discredited by a cursory analysis of the paper, and a manuscript detailing the numerous fundamental errors made in the Energy and Environment paper has been

submitted to the peer-reviewed literature. We would be happy to provide a copy of

the paper to be made part of the official Senate record once it is published.

Question 12. Are you aware of any errors in any calculations that you made in

MBH98 or MBH99? If so, what are the errors?

Response. See response to question 11.

Question 13. Vegetation grows as a result of a number of factors, including energy

input, moisture supply, fire frequencies, and species competition. Do you claim it is

possible to accurately remove the effects of these factors from your tree ring proxy

datasets to produce a resulting time-series represents fluctuations in only air temperature? What is the magnitude of the error introduced in developing a procedure

to remove these other effects? Please detail the analyses and list peer-reviewed

works that specifically outline techniques to remove the effect of these other indicators for inferring past temperatures.

Response. One of the co-authors of MBH98 (Malcolm Hughes) is among the

world’s foremost experts in dendroclimatology, so the team of MBH98 hardly needs

to be informed of the processes that influence tree growth. The method of MBH98
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does not ‘‘remove’’ various factors from tree ring proxy information (which would be

a most unwise approach!) but, rather, uses multivariate statistical methods similar

to those commonly used in climate and paleoclimate field reconstruction [see e.g.

Cook, E.R., K.R. Briffa, and P.D. Jones, Spatial Regression Methods in

Dendroclimatology: A Review and Comparison of Two Techniques, International

Journal of Climatology, 14, 379–402, 1994; Smith, T.M., R.W. Reynolds, R.E.

Livezey, and D.C. Stokes, Reconstruction of Historical Sea Surface Temperatures

Using Empirical Orthogonal Functions, Journal of Climate, 9, 1403–1420, 1996;

Kaplan, A., Y. Kushnir, M.A. Cane, and M.B. Blumenthal, Reduced space optimal

analysis for historical data sets: 136 years of Atlantic sea surface temperatures,

Journal of Geophysical Research, 102, 27835–27860, 1997] to separate the information in the data that can meaningfully be related to surface temperature variations

from that related to other influences.

Question 14. Define the difference between variability and error in a statistical

analysis. In EOF analyses, is the variation of the first principal component indicative of the uncertainty associated with the data? Why or why not?

Response. Variability in an estimated quantity can be thought of as representing

both ‘signal’ (the physical quantity one is interested in and ‘noise’ (everything else).

The definition of noise and signal depends on a number of assumptions regarding

the nature of the process that generated the times series of interest and the specification of the statistical model for the data in question. Uncertainty, which is associated with the partitioning of data variance into ‘‘noise and signal’’, as defined

above, depends on such detailed considerations. There are no general statistical

principles that I am familiar with that relate uncertainty, thusly defined, to the

first, or any other, principal component of a dataset containing both signal and noise

contributions. Uncertainty is typically diagnosed by the analysis of residual variance

from a statistical model based on a combined calibration/cross-validation procedure.

Introductory text books such as ‘‘Statistical Methods in the Atmospheric Sciences’’

(D. Wilks, Academic Press) deal with this topic in detail.

Question 15. Specifically, how do you construct regional patterns of temperature

changes in past centuries when data are limited, either spatially, temporally, or

both?

Response. Our methods are described in detail in the following peer-reviewed scientific publications, which I would like to have made part of the official Senate

record: • Mann, M.E., Jones, P.D., Global Surface Temperatures over the Past two Millennia, Geophysical Research Letters, 30 (15), 1820, 10.1029/2003GL017814, 2003. • D’Arrigo, R.D., Cook, E.R., Mann, M.E., Jacoby, G.C., Tree-ring reconstructions

of temperature and sea level pressure variability associated with the warm-season

Arctic Oscillation since AD 1650, Geophysical Research Letters, 30 (11), 1549, doi:

10.1029/2003GL017250, 2003.

• Mann, M.E., Rutherford, S., Bradley, R.S., Hughes, M.K., Keimig, F.T., Optimal

Surface Temperature Reconstructions Using Terrestrial Borehole Data, Journal of

Geophysical Research, 108 (D7), 4203, doi: 10.1029/2002JD002532, 2003.

• Rutherford, S., Mann, M.E., Delworth, T.L., Stouffer, R., Climate Field Reconstruction Under Stationary and Nonstationary Forcing, Journal of Climate, 16, 462–

479, 2003.

• Mann, M.E., Large-scale climate variability and connections with the Middle

East in past centuries, Climatic Change, 55, 287–314, 2002.

• Cook, E.R., D’Arrigo, R.D., Mann, M.E., A Well-Verified, Multi-Proxy Reconstruction of the Winter North Atlantic Oscillation Since AD 1400, Journal of Climate, 15, 1754–1764, 2002.

• Mann, M.E., Rutherford, S., Climate Reconstruction Using ‘Pseudoproxies’, Geophysical Research Letters, 29 (10), 1501, doi: 10.1029/2001GL014554, 2002.

• Mann, M.E., Large-scale Temperature Patterns in Past Centuries: Implications

for North American Climate Change, Human and Ecological Risk Assessment, 7

1247–1254, 2001.

• Mann, M.E., Climate During the Past Millennium, Weather (invited contribution), 56, 91–101, 2001.

• Cullen, H., D’Arrigo, R., Cook, E., Mann, M.E., Multiproxy-based reconstructions of the North Atlantic Oscillation over the past three centuries, Paleoceanography, 15, 27–39, 2001.

• Mann, M.E., Gille, E., Bradley, R.S., Hughes, M.K., Overpeck, J.T., Keimig,

F.T., Gross, W., Global Temperature Patterns in Past Centuries: An interactive

presentation, Earth Interactions, 4–4, 1–29, 2000.

• Delworth, T.L., Mann, M.E., Observed and Simulated Multidecadal Variability

in the Northern Hemisphere, Climate Dynamics 16, 661–676, 2000.
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• Mann, M.E., Bradley, R.S. and Hughes, M.K., Northern Hemisphere Temperatures During the Past Millennium: Inferences, Uncertainties, and Limitations, Geophysical Research Letters, 26, 759–762, 1999.

• Mann, M.E., Bradley, R.S., and Hughes, M.K., Global-Scale Temperature Patterns and Climate Forcing Over the Past Six Centuries, Nature, 392, 779–787, 1998.

Question 16. Do you claim that the instrumental temperature record is known

without error? If not, what error and uncertainty would you associate with the annual Northern Hemisphere averaged air temperature for 1900? For 1950? For 2000?

How were these estimates incorporated into your analysis?

Response. The claim made by Dr. Legates in his testimony that we present the

instrumental record without uncertainty is incorrect. If Legates, for example, were

familiar with studies of the instrumental surface temperature record, he would understand that the uncertainties in this record during the 20th century are small

compared to the uncertainties shown for our reconstruction [see e.g. Figure 2.1b in

Folland, C.K., Karl, T.R., Christy, J.R., Clarke, R. A., Gruza, G.V., Jouzel, J., Mann,

M.E., Oerlemans, J., Salinger, M.J., Wang, S.-W., Observed Climate Variability and

Change, in Climate Change 2001: The Scientific Basis, Houghton, J.T., et al. (eds.),

Cambridge Univ. Press, Cambridge, 99–181, 2001.]. Furthermore, all scientists with

a proper training in statistics know that uncertainties add ‘‘in quadrature’’. In other

words, you have to square them before adding them. This means that the relatively

small uncertainty in the instrumental record makes a relatively small contribution

to the total uncertainty. Legates claimed in his testimony that including the uncertainty in the instrumental record, which he estimates as 0.1oC would change the

conclusions expressed by us and other mainstream climate scientists that the 1990’s

are the warmest decade in at least the past 1000 years within estimated uncertainties. This claim is very misleading for several reasons, First, the standard error in

Northern Hemisphere mean annual temperatures during the 1990’s is far smaller

than the amount cited by Legates [see again Folland et al, 2001 cited above]. Even

more problematic, however, Legates claim indicates a fundamental misunderstanding of the statistical concepts of standard error and uncertainty. The shaded

region shown along with the Mann et al reconstruction (and other similar plots

shown in recent articles such as the aforementioned ‘‘Eos’’ article, and the IPCC report) indicates two standard error intervals. The decade of the 1990’s is roughly two

standard errors warmer (i.e., about 0.4oC)] than any decade prior to the 20th century in the reconstruction. Based on a one-sided test for anomalous warmth, this

translates to a roughly 97.5 percent level of significance. Modifying the uncertainties

to include the small additional contribution due to uncertainties in the instrumental

record itself would modify this only slightly, and would not lower the significance

level below the 95 percent level. Though there is no such thing as an absolute estimate of uncertainty, despite Legate’s implications to the contrary, a 95 percent confidence is often adopted as an appropriate criterion for significance. Legates’ statement that including instrumental contributions to the uncertainty would change the

conclusions is thus clearly false.

Question 17. Assuming a proxy record extended back to 1000 A.D., what specifically would be required to disqualify this proxy record from your analyses? Provide

supporting evidence where others have disqualified such records from temperature

analyses on these criteria.

Response. It is unclear what type of ‘‘analyses’’ are being referred to here. I have

used a variety of different statistical methods and data in various published studies

describing paleoclimate reconstruction, so the question as worded is implicitly

vague. In any case, our approaches do not ‘‘disqualify’’ proxy data. They use objective statistical criteria to evaluate the strength of the signal available for reconstruction of the particular climate field or index (be it related to surface temperature, atmospheric circulation, drought, or other variables) to be reconstructed. Such

statistical approaches, and the related approaches used by other climate researchers, are described in the various publications listed above in the response to Questions No. 13 and 15.

Question 18. Have you made available via FTP the coefficients developed to relate

proxies to principal components? If not, would you make those coefficients available

at NGDC/paleo?

Response. The question is based on two false premises. The first involves a naive

view of what is required and expected of scientific researchers. It is unprecedented

in my experience for any scientist to post in the public domain every single computational aspect of a complicated analysis. The methods of our study were adequately described in our paper and supplementary information, and the data used

were made available in the public domain. Indeed, we made far more of our results,
185

data, and methodological details available in the public domain than is provided in

most similar scientific studies. The scientific funding agencies (DOE, NSF, and

NOAA) would have informed us if we had not followed the appropriate protocols in

the provision of data and results.

The second false premise is a technical one. A proper understanding of the methodology employed by MBH98 would reveal that there is no one fixed set of ‘‘coefficients’’ that relate a particular proxy record to a particular principal components.

The relationship is determined based on time-dependent inverse problem for which

the weights on different records are not fixed over time, as described in our published articles.

Question 19. Have you made available via FTP any specialized computer studies,

such as Matlab scripts, in connection with your temperature reconstruction? If not,

would you make any such scripts used in developing the temperature reconstructions in MBH98 and MBH99 available through NGDC/paleo?

Response. The methodologies have been described, and other climate researchers

have independently, successfully implemented the methodology, e.g.: Zorita, E., F.

Gonzalez-Rouco, and S. Legutke, Testing the Mann et al. (1998) Approach to

Paleoclimate Reconstructions in the Context in a 1000-Yr Control Simulation with

the ECHO-G Coupled Climate Model, Journal of Climate, 16, 1378–1390, 2003.

Question 20. Do you claim your method of reconstructing past temperature from

proxies is the only correct one? If not, please submit some published papers that

use methods you consider to be correct as well. If you do consider yours the only

correct method, can you provide a list of names of scientists whom you have contacted to tell them they are using the wrong methods in their work?

Response. The question is based on the false premise that my colleagues and I

use any one particular ‘‘method’’ of reconstructing past temperatures from proxy

data. In fact, I have published on the application of at least five fundamentally independent methods for using proxy data to reconstruct past climate patterns in the

peer-reviewed literature. Examples of the applications of different methods can be

found in the following peer-reviewed scientific publications:

• Zhang, Z., Mann, M.E., Cook, E.R., Alternative Methods of Proxy-Based Climate

Field Reconstruction: Application to the Reconstruction of Summer Drought Over

the Conterminous United States back to 1700 From Drought-Sensitive Tree Ring

Data, Holocene, in press, 2003.

• Mann, M.E., Jones, P.D., Global Surface Temperatures over the Past two Millennia, Geophysical Research Letters, 30 (15), 1820, 10.1029/2003GL017814, 2003.

• Mann, M.E., Rutherford, S., Bradley, R.S., Hughes, M.K., Keimig, F.T., Optimal

Surface Temperature Reconstructions Using Terrestrial Borehole Data, Journal of

Geophysical Research, 108 (D7), 4203, doi: 10.1029/2002JD002532, 2003.

• D’Arrigo, R.D., Cook, E.R., Mann, M.E., Jacoby, G.C., Tree-ring reconstructions

of temperature and sea level pressure variability associated with the warm-season

Arctic Oscillation since AD 1650, Geophysical Research Letters, 30 (11), 1549, doi:

10.1029/2003GL017250, 2003.

• Mann, M.E., Bradley, R.S., and Hughes, M.K., Global-Scale Temperature Patterns and Climate Forcing Over the Past Six Centuries, Nature, 392, 779–787, 1998

On occasion, there are approaches used that are not adequate. For example, the

approach of simply counting papers and not properly defining what constitutes an

anomaly, as was the case for the paper by Soon et al. (2003), is most decidedly not

adequate. Also, the analysis approach used by McIntyre and McItrick (2003) in

which the authors attempted to reproduce the results of the previous study of

MBH98 based on an analysis which used neither the same data (the authors eliminated the majority of data used by MBH98 for the first two centuries of the reconstruction) , or method as the original authors, was woefully inadequate. In fact, this

latter study was described as ‘‘seriously flawed’’ and ‘‘silly’’ in a recent article in

USA Today (‘‘Global Warming Debate Heats Up Capitol Hill’’, 11/19/03). When deeply flawed studies such as this are published, I am interested in determining what

errors have been made and, if necessary as in this latter case, promptly submitting

a rebuttal to the peer-reviewed scientific literature to ensure that the scientific community is not misled by the use of inadequate approaches. To my knowledge, I am

not considered to be shy in offering criticism where criticism is due.

Question 21. If there are other acceptable methods, did you try any of them on

your data set prior to its publication to see what the results would be? If so would

you please submit the results. If not, have you done so since? Why do you claim

your multi-proxy results represent a ‘‘robust consensus,’’ as you said in your Eos

publication, if you have not verified that its results would also be obtained using

other acceptable methods?
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Response. As demonstrated both in the Eos article, and the various references

provided in my response to Question 4, about a dozen different recent estimates

based on a variety of data and approaches, published by different groups, yield statistically indistinguishable histories of Northern Hemisphere mean temperature

changes in past centuries. I define such a result as characterizing a ‘‘consensus’’.

Question 22. Did you at any time prior to publication compute the analysis up to

1984 or later? What were the results? If you did not, even though you had sufficient

data, why not? If you did but you did not use those results, explain why. If the results were different, where did you publish a discussion of those differences? If they

were the same, why did you delete them? Why, in other words, did you throw out

data for the period of maximum interest?

Response. Most of the proxy records used in MBH98 and MBH99 ended by 1980,

limiting the useful upper limit to the calibration period used. A more recent paper

(in press) extends proxy-based hemispheric temperature reconstructions through the

mid-1990’s, demonstrating the ability of the reconstruction to capture the accelerated warming evident in the instrumental record since 1980. We would be happy

to provide a copy of this paper to be made part of the official Senate record when

it is formally published.

Question 23. On your web site http://www.ngdc.noaa.gov/paleo/ei/data—

supp.html where you explain the assembling of the data base for your 1980 paper

you say: ‘‘Small gaps have been interpolated. If records terminates lightly before the

end of the 1902–1980 training interval, they are extended by persistence to 1980.’’

Does this mean you made up some observations to fill in blank spots in the data

records? Have you ever provided a complete public listing of all the data you made

up? Please provide such a listing now. Of the 112 proxies, in how many of them

did you fill gaps? Why in some of them but not others? What is the longest interval

of time over which you filled in missing observations?

Response. Extension of missing values by ‘persistence’ of the final available value

is a typical statistical approach to estimating small amounts of unavailable data at

the end of a time series (see e.g. the textbook by Wilks, referred to in the response

to Question No. 14). The fact that this approach was used to infill a modest number

of missing observations between 1972 and 1980 was described in the Nature supplementary information. All of the data used in our study have been available since

July 2002 on the public ftp site: ftp://holocene.evsc.virginia.edu/pub/MBH98/.

Question 24. What was the effect on your results of filling in the missing data?

Did you run your analysis without it? Please submit the results when the filled-in

data are dropped from the analysis. If it changes your results, where is that discussed If it makes no difference, why did you do it?

Response. The use of infilled data has essentially no effect on the reconstruction,

as demonstrated by the fact that the same result is achieved if a 1902–1971 calibration period (which predates the use of any infilled proxy data) is used instead of

a 1902–1980 calibration period. It is advisable to use the full 1902–1980 calibration

interval, however, because the increased statistical constraint provided by the

lengthening of the calibration period more than offsets the impact of the use of a

modest amount of in-filled data in a small number of series.

Question 25. Do you agree that statistical methods based on linear extrapolation

from data representing the far extreme of the line are associated with an added

error/uncertainty? If so, how was this incorporated into the assessment of the error/

uncertainty in your temperature reconstructions? Please provide citations from your

publications. If not, please explain why the uncertainty envelope of a linear regression grows larger as a function of the distance from the mean of the data used to

fit the parameters and why this was not included in your research.

Response. The so-called ‘‘leverage effect’’ which the question appears to refer to,

is taken into account through consideration of the spectrum of the calibration residuals, allowing for resolution of any enhancement of uncertainty as a function of

frequency (see MBH99). Alternatively, the uncertainties can be evaluated from an

independent sample (i.e., cross-validation, rather than calibration, residuals) that

eliminates any influence of calibration period leverage in the estimation of uncertainties. Both approaches give similar results [e.g. Rutherford, S., Mann, M.E.,

Osborn, T.J., Bradley, R.S., Briffa, K.R., Hughes, M.K., Jones, P.D., Proxy-based

Northern Hemisphere Surface Temperature Reconstructions: Sensitivity to Methodology, Predictor Network, Target Season and Target Domain, Journal of Climate,

submitted, 2003].

Question 26. Please describe the peer review process that took place with respect

to your Forum article that appeared in EOS on July 8, 2003. If, according to the
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AGU, the EOS Forum contains articles stating a personal point of view on a topic

related to geophysical research or the relationship of the geophysical sciences to society, how can you claim that your article is peer reviewed?

Response. The article was independently reviewed and evaluated for suitability

for publication by an editor who has expertise in the particular subject area. The

associated process is correctly described as ‘‘peer review’’. Appropriate to the relatively short and non-technical nature of Eos ‘‘Forum’’ pieces, the associated peer

review process is not as extensive as that employed for articles in the more technical

literature such as Geophysical Research Letters, or Journal of Geophysical Research.

I would suggest that the questioner contact representatives at AGU for more details

on the peer-review process employed for their different journals and paper categories.

Question 27. Do you claim that producing estimates of past climate states is an

exact science If so, explain why different authors can get such significantly different

results when investigating and reconstructing past temperature, and detail the errors that other authors must have made. If not, explain how there can be, as you

put it in your EOS article, a ‘‘robust consensus’’ regarding the correct estimate of

the climate state of the past millennium.

Response. The term ‘‘exact science’’ is generally not used, or considered meaningful or appropriate by scientists, as science almost always involves the testing of

hypotheses based on the use of intrinsically uncertain data or observations. Consistent with this fundamental aspect of nearly all scientific endeavors, my colleagues

and I, and other researchers in the paleoclimate community, typically interpret the

results of paleoclimate reconstructions within the context of sometimes substantial

associated uncertainties. When a large number of estimates agree with each other

within estimated uncertainties, and those uncertainties are modest enough to still

allow for non-trivial conclusions (for example, that late 20th century warmth is

anomalous in a long-term context), those conclusions can be considered as both ‘‘robust’’ and a ‘‘consensus’’.

Question 28. Please describe the peer review process that took place with respect

to your 1999 Geophysical Research Letters paper. What were the criticisms or improvements suggested by the referees? Why was no reference made to the anomalous global warming caused by the very strong El Nin ̃ o event of 1997–98 in your

paper? Is this 1999 paper continuation of your 1998 paper in Nature where you

stopped your reconstruction at AD 1400?

Response. The comments of reviewers on a manuscript are considered a confidential matter, involving the editor, reviewers, and authors. Providing these comments

for public record would be ethically questionable, and probably violates the confidentiality policies of the associated journals. Minor suggestions were made by the reviewers and editor, and addressed to their satisfaction prior to the acceptance and

publication of the paper.

Question 29. In Mann and Jones 2003 Geophysical Research Letters, did you

change your methodology in the reconstruction of the hemispheric or global scale

temperature from your prior publications? If so, why did you, and what is the rationale for the change of approach?

Response. The question is wrongly premised, as it presumes, through the use of

the language ‘‘change your methodology’’ that scientists only have one particular

methodological approach that can be applied to a problem at hand. As discussed in

my answer to question 20, my research has involved the use of a variety of different

methods for reconstructing past climate patterns from proxy data. The paper by

Mann and Jones (2003), for example, uses a coarser resolution proxy dataset than

MBH98/MBH99 and a compositing methodology that allows for the reconstruction

of decadal, but not annual, changes, and the reconstruction of hemispheric mean,

but not spatially resolved, patterns of temperature in past centuries. In doing so,

the study was able to make use of a more restricted set of temperature records

available over a longer timeframe than those used in previous high-resolution proxy

reconstructions of hemispheric temperature change.

Question 30. Did IPCC carry out any independent programs to verify the calculations that you made in MBH98 or MBH99? If so, please provide copies of the reports

resulting from such studies.

Response. It is distinctly against the mission of the IPCC to ‘‘carry out independent programs’’, so the premise of the question is false. However, the IPCC’s author team did engage in a lively interchanges about the quality and overall consistency of all of the papers as the chapter was drafted and revised in the course of

review.
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Question 31. Did IPCC carry out any independent quality control on the data that

you used in MBH98 and MBH99? If so, please provide copies of the reports resulting

from such studies.

Response. The IPCC doesn’t ‘‘carry out studies’’, so the premise of the question

is false. The IPCC instead depends that the normal scientific peer-review process,

especially when done in a leading journal, has ensured an acceptable level of quality. In addition, the IPCC does check to see if any criticisms have been raised

postreview in comments and response to the journal articles.

Question 32. Did IPCC carry out any studies to validate the statistical procedures

and methodologies used in MBH98 and MBH99? If so, please provide copies of the

reports resulting from such studies.

Response. The IPCC doesn’t ‘‘carry out studies’’, so the premise of the question

is false. Instead, as indicated above, the IPCC relies on earlier stages of review to

cover such matters.

Question 33. Has any organization other than IPCC or your associates carried out

any independent programs to verify the calculations that you made in MBH98 or

MBH99? If so, please provide copies of the reports resulting from such studies.

Response. I know of no ‘‘organizations’’ that carry out ‘‘independent programs’’ to

verify calculations of individual co-authors. If the question is, have other scientists

reproduced the basic results of MBH98 and MBH99, the answer is yes. Numerous

other groups (see the dozen or so independent estimates of various groups shown

in Figure 1 of: Mann, M.E., Ammann, C.M., Bradley, R.S., Briffa, K.R., Crowley,

T.J., Hughes, M.K., Jones, P.D., Oppenheimer, M., Osborn, T.J., Overpeck, J.T.,

Rutherford, S., Trenberth, K.E., Wigley, T.M.L., On Past Temperatures and Anomalous Late 20th Century Warmth, Eos, 84, 256–258, 2003) have produced reconstructions that are remarkably similar to those of MBH98 based on a variety of data and

methods. Refer back to my answer to question 4 for further details. I would like to

see each of these papers made an official part of the Senate record.

Question 34. Has any organization other than IPCC conducted independent quality control on the data that you used in MBH98 and MBH99? If so, please provide

copies of the reports resulting from such studies.

Response. The IPCC doesn’t ‘‘carry out studies’’, so the premise of the question

is false. The data used by MBH98 (and MBH99) were produced by other researchers, not Mann and colleagues. It is thus not clear what kind of ‘‘independent quality

control’’ is being referred to here. However, it is fair to say that each of these papers

has been subject to rigorous peer review in a leading scientific journal, which is considered by scientists to be an independent quality control process. We are aware of

no criticisms of the datasets in the peer-reviewed scientific literature.

Question 35. Has any organization other than IPCC carried out any studies to

validate the statistical procedures and methodologies used in MBH98 and MBH99?

If so, please provide copies of the reports resulting from such studies.

Response. The IPCC doesn’t ‘‘carry out studies’’, so the premise of the question

is false. If the question were asked: Have other independent groups tested the methodology of Mann et al (1998) in a publication in the peer-reviewed climate literature,

the answer would be ‘‘yes’’. I would refer the questioner to the following paper:

Zorita, E., F. Gonzalez-Rouco, and S. Legutke, Testing the Mann et al. (1998) Approach to Paleoclimate Reconstructions in the Context in a 1000-Yr Control Simulation with the ECHO-G Coupled Climate Model, Journal of Climate, 16, 1378–1390,

2003.

The paper arrives at the conclusion that the methodology of MBH98 performs well

with networks of data comparable to those used by MBH98.

Question 36. Have you ever received any communications that suggested that

there might be computational errors in MBH98 or MBH99? Please provide such

communications together with any responses.

Response. I receive many emails, often from list-serves of self-professed ‘‘climate

skeptics’’ making numerous spurious claims against my work and that of many of

my colleagues. I have received no correspondence providing credible evidence of any

errors in our work. Nor has any such credible evidence been published in the peerreviewed scientific literature.

Question 37. Did the peer reviewers for Nature in MBH98 carry out any independent quality control or validation studies? If so, please provide copies of such reports.

Response. Neither I, nor authors of peer-reviewed journal articles in general, are

made privy to the detailed analyses that peer reviewers may or may not have performed in the process of reviewing a manuscript. Authors only receive the comments
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that were selected to be made available to them by the reviewer and editor. This

question is thus impossible to answer. Numerous other groups (see the dozen or so

independent estimates of various groups shown in Figure 1 of: Mann, M.E.,

Ammann, C.M., Bradley, R.S., Briffa, K.R., Crowley, T.J., Hughes, M.K., Jones,

P.D., Oppenheimer, M., Osborn, T.J., Overpeck, J.T., Rutherford, S., Trenberth,

K.E., Wigley, T.M.L., On Past Temperatures and Anomalous Late 20th Century

Warmth, Eos, 84, 256–258, 2003) have produced reconstructions that are remarkably similar to those of MBH98 based on a variety of data and methods. See my

answer to Question No. 4.

Question 38. 38. Did the peer reviewers for Geophysical Research Letters in

MBH99 carry out any independent quality control or validation studies? If so, please

provide copies of such reports.

Response. See response to Question No. 37.

Question 39. How many people have requested the underlying digital information

in MBH98? Please provide dates of such requests and dates of your reply.

Response. My collaborators and I have not kept a specific record. The data has

been provided to any scientific groups that have requested it, and has been made

available on an open access basis through a public ftp site: ftp://holocene.evsc.virginia.edu/pub/MBH98/, since July 2002.

Question 40. Were you one of the primary or lead authors of IPCC/TAR chapter

2?

Response. The convening lead authors of chapter 2 of the IPCC TAR were Dr.

Chris Folland and Thomas Karl. I was one of eight additional co-authors contributing to chapter 2.

Question 41. In your capacity as IPCC/TAR author, did you prepare any drafts

that referred to your own papers? Please provide all drafts that you prepared for

IPCC.

Response. I contributed to numerous sections of the chapter and provided contributions that referenced the work of the leading paleoclimatologists, which includes me and many of my colleagues. Those interested in drafts of IPCC chapters

should inquire of the appropriate IPCC working group. I am not in possession of

such drafts, and even if I were, I would not be at liberty to distribute the various

drafts of the chapters of the report.

Question 42. Was any language from your drafts referring to your own reports ultimately used by IPCC/TAR? Please provide highlighted versions from IPCC.

Response. The wording of the question is unclear. If the question is, did I, in my

contributions to the chapter, provide summaries that included references to my own

work as well as that of other scientists, the answer is of course yes. Since each of

the authors was asked to contribute sections related to their particular areas of expertise, and since the IPCC authors were chosen from among the leading scientists

in the world, it would be distinctly odd if it were not the case that most authors

referred to their work, as well as that of others, in their contributions.

Question 43. Did IPCC/TAR have any policies governing how lead authors used

their own work? Did IPCC/TAR have any quality control procedures in the event

that a lead author used his own work? Please provide a short summary of your understanding of such procedures.

Response. I am not a spokesperson for the IPCC. However, it is my understanding

that the IPCC carries out a process for developing its summarization of the understanding of science that leads to one of the most rigorously peer-reviewed scientific

documents in existence. Individual technical chapters are prepared by expert scientific teams that consider the full range of published papers in a subject area. This

expert author team then solicits an initial peer review from a large number of other

scientists in the field, drawing on those representing the full range of expert science.

The reports next go through a much wider review that is open to literally thousands

of scientists around the world. Finally countries, NGO’s, and professional groups

(such as business groups) are provided the opportunity to send in review comments.

(and in the case of the U.S. government review, an invitation to submit comments

to be considered to be forwarded to the IPCC is published in the Federal Register,

enabling all to participate in this review). With the comments available at each

stage of the review process, the authors consider each comment and document their

response. The meticulousness and fairness of the revision process by the authors in

response to reviewer comments is evaluated by an independent pair of ‘‘review editors’’ who are themselves top international climate scientists who are not authors

of the report itself. The National Academy of Sciences, at President George W.

Bush’s request, and other national academies around the world have independently
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reviewed the process and the validity of the scientific findings of the IPCC and endorsed them.

Question 44. Did MBH98 and MBH99 use any proxy series, which were either unpublished or which resulted from unpublished calculations, which you carried out?

If so, please identify, and detail how you verified those unpublished results.

Response. MBH98 and MBH99, as many studies, made use of newly available

data that had not yet been published by the original authors providing those data,

and thus was provided to Mann and colleagues on a provisional basis that they not

release the data until the authors had a chance to publish the records themselves.

After all of the data used had been published, the full dataset used by MBH98 and

MBH99 was made available in the public domain on the public website: ftp://holocene.evsc.virginia.edu/pub/MBH98/

Question 45. Despite solar variability over the last two millennia, your analysis

concludes the Northern Hemisphere average temperature has remained virtually

constant. What mechanism or mechanisms are responsible for negating the influence of the sun? Do climate models (GCMs) exhibit the same lack of response to

solar forcing that your analysis implies? If not, why are model simulations at variance with your conclusions and how does that limit their applicability for future climate scenario assessments?

Response. The question is falsely premised on several levels. No reasonable description of the reconstructions that we or others have produced of temperature

variations in past centuries would characterize them as ‘‘virtually constant’’. The reconstructions performed by my group and others indicate an amplitude of variability

that consistent with expectations from models driven with estimates of past radiative forcing including solar and radiative forcing, and allowing for the added role

of internal unforced variability [see e.g. Crowley, T.J., Causes of Climate Change

Over the Past 1000 Years, Science, 289, 270–277, 2000]. Indeed, it has been shown

that the model-predicted pattern of surface temperature response to solar forcing in

past centuries closely resembles that estimated from the temperature reconstructions that my colleagues and I have performed [Shindell, D.T., Schmidt, G.A., Mann,

M.E., Rind, D., Waple, A., Solar forcing of regional climate change during the Maunder Minimum, Science, 294, 2149–2152, 2001; Waple, A., Mann, M.E., Bradley, R.S.,

Long-term Patterns of Solar Irradiance Forcing in Model Experiments and Proxybased Surface Temperature Reconstructions, Climate Dynamics, 18, 563–578, 2002;

Shindell, D.T., Schmidt, G.A., Miller, R., Mann, M.E., Volcanic and Solar forcing of

Climate Change During the Pre-Industrial era, Journal of Climate, in press, 2003].

Question 46. How did the temperatures of the mid-Holocene Optimum Period

(6000 to 9000 BP) compare with those observed today? Was it a global or a local

phenomenon? What was or were the cause or causes of any temperature anomalies

in that period? What is the cause of the 104 to 105 year timescale changes in deuterium, oxygen isotope, etc., concentrations in ice core records? Are such changes global or local?

Response. Paleoclimate experts have established that mid-Holocene warmth centered roughly 5000 years ago was restricted to high latitudes and certain seasons

(summer in the Northern Hemisphere and winter in the southern hemisphere). Because much of the early paleoclimate evidence that was available (for example, fossil

pollen assemblages) came from the Northern Hemisphere extratropics, and is largely reflective of summer conditions, decades ago some scientists believed that this

was a time of globally warmer conditions. It is now well known that this is not the

case. More abundant evidence now demonstrates, for example, that the tropical regions were cooler over much of the year. All of these changes are consistent with

the expected response of surface temperatures to the known changes in the Earth’s

orbital geometry relative to the Sun during that time period and associated climate

feedbacks, as detailed in peer-reviewed scientific publications [e.g., Hewitt, C.D., A

Fully Coupled GCM Simulation of the Climate of the Mid-Holocene, Geophysical Research Letters, 25 (3), 361–364, 1998; Ganopolski, A., C. Kubatzki, M. Claussen, V.

Brovkin, and V. Petoukhov, The Influence of Vegetation-Atmosphere-Ocean Interaction on Climate During the Mid-Holocene, Science, 280, 1916–1919, 1998].

Climate model simulations indicate quite good agreement with paleoclimate evidence now available. These models calculate that global annual average temperatures were probably about the same or a few tenths of a degree C cooler than today

(the late 20th century) during this time period [Ganopolski, A., C. Kubatzki, M.

Claussen, V. Brovkin, and V. Petoukhov, The Influence of Vegetation-AtmosphereOcean Interaction on Climate During the Mid-Holocene, Science, 280, 1916–1919,

1998; Kitoh, A., and S. Murakami, Tropical Pacific Climate at the mid-Holocene and

the Last Glacial Maximum simulated by a coupled oceanatmosphere general circula-
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tion model, Paleooceanography, 17 (3), (19)1–13, 2002.]. That’s a far cry from the

very out-of-date claim made by Dr. Legates in his testimony. Dr. Legates’ comments

regarding climate changes over the past 1000 years reflect a similar lack of familiarity with a whole body of paleoclimate research, especially with the new insights

gained through the augmented research program, during the past decade.

Question 47. It has been observed that in the past, carbon dioxide concentrations

have sometimes lagged air temperature trends; that is, changes in air temperature

have subsequently sometimes resulted in changes in carbon dioxide concentrations.

Do you agree with those results from expert researchers? Why or why not?

Response. The question mis-characterizes the evidence that has been provided by

paleoclimate researchers. The studies that the questioner appears to be alluding to,

demonstrate a phase relationship between ice core CO2 estimates and *local* temperature variations at the site of the ice core. Furthermore these local temperature

estimates are indirectly inferred from oxygen isotopes, based on quite uncertain assumptions regarding oxygen isotope paleothermometary and neglecting possible biases due to the variable seasonality of local accumulation. As local temperature

variations at the site of the ice core have an unknown relationship with global mean

temperature variations (which are far more dominated by lower latitudes which occupy the majority of the Earth’s surface area), the phase relationships between past

CO2 and global mean temperature variations are not known. In spite of these qualifications, it is not at all implausible that the geologic record indicates that at some

times the CO2 increase may lag the initial temperature increase; such a situation

would be expected, for example, if the change in climate was initiated by a change

in the orbital geometry that affected the distribution of solar radiation, and then

the slow warming drove CO2 from the warming ocean into the atmosphere. It is because of the many possibilities for how different processes can interact that it is essential to not simply base a conclusion on an apparent correlation without evaluating the underlying physical mechanisms for that particular period.

Question 48. Are there any time periods for which atmospheric CO2 content has

changed without a concomitant change in global air temperature? Are there periods

when the atmospheric CO2 content was relatively high butglobal air temperatures

relatively low?

Response. In his testimony, Dr. Legates indicated that there were historical cases

where the temperature has gone up, but that CO2 has fallen. It may well be the

case that this has happened in the past. However, it is hardly surprising, and certainly not inconsistent with our established understanding of the various factors

that influence surface temperatures. The warming response to increased greenhouse

gas concentrations lags the actual increase in greenhouse gas concentrations in the

atmosphere potentially by several decades, due to the sluggish response of the

oceans, which have an enormous thermal capacity compared to the atmosphere, to

increased surface radiative forcing. So warming is not expected to be contemporaneous with changes in CO2, but instead, to lag it by several decades. However,

greenhouse gases are certainly not the only factor affecting the average surface temperature of the Earth. There are other anthropogenic factors, such as increased

sulphate aerosols, which can have a cooling effect on the climate, and natural factors, such as volcanic activity, modest natural variations in solar output, and internal dynamics associated with climate events such as El Nin ̃ o, which also influence

the average surface temperature of the globe. At any particular time, these other

factors may outweigh the warming effect due to increased greenhouse gases. For example, the relative lack of warming during the period 1940–1970 appears to be related to a combination of such factors, as discussed in my response to an earlier

question. But while these other factors tend to cancel over time, the increased

greenhouse gases lead to a systematic warming that will not cancel out over a very

long time period. It is for precisely this reason that late 20th century warming now

appears to have risen above the range of the natural variability of past centuries.

Question 49. Two independent and nearly direct measures of surface temperature

(deep borehole reconstructions) over the past several millennia have been published

for Greenland (Dahl-Jensen et al 1998) and the Middle Urals (Demeshko and

Shchapov 2001). The local surface temperature at these locations is highly correlated with global temperature on 10-year time scales and longer (r2 > 50 percent

10 yr with agreement increasing for longer averaging periods). Both reconstructions

independently show their local surface temperatures were at least a1 ° C warmer

for century-scale mean temperatures around A.D. 900 than the latter half of the

20th century, translating into a global anomaly of at least +0.2° C relative to today.

This further implies that even higher global temperature anomalies for shorter

periods, such as half-century or decadal periods, were observed about 1000 years
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ago. Why do these two robust measures of local and global approximations differ

greatly from Mann et al. 1999?

Response. The question is wrongly premised on multiple levels. First, the correlations cited are completely wrong. No citation to the peer-reviewed literature is provided, so it is difficult to determinate how these numbers were arrived at. I therefore proceeded to analyzed the appropriate surface air temperature gridpoint data

from the Climatic Research Unit of the University of East Anglia myself. I found

that only after 1922 is there adequate coverage (>50 percent areal coverage) to estimate a meaningful Greenland areal-mean temperature. For the period back to 1922,

the linear correlation between the Greenland and Northern Hemisphere mean temperature is r= ¥0.06 (negative!), nor is there a significant correlation at decadal or

longer timescales. In fact, the trends in the two series during the latter 20th century

are of opposite sign. So the numbers cited are completely spurious.

It is in fact well known by the climate community that there are fundamental

physical reasons why temperatures in Greenland are, in general, poorly correlated

with Northern Hemisphere mean temperature. Owing to the strong overprint of

processes, such as the North Atlantic Oscillation, and changes in coupled ocean-atmosphere processes in the North Atlantic that impart a large regional overprint of

temperature variation in this region, both negative and positive correlations with

Northern Hemisphere mean temperature can be found, depending on the time period and region of Greenland analyzed.

The Dahl Jensen et al Greenland borehole data may indeed be useful temperature

proxy data for the regions they represent, and they have been used in reconstructions of Northern Hemisphere mean temperature, with caveats due to their extremely low temporal resolution (see Mann and Jones, 2003). While the two Greenland borehole records show significantly different histories over the past 1000 years

(which is expected since temperature trends vary markedly depending on the region

of Greenland in question), one of the two records does correlate well with the instrumental Greenland record over the period of mutual overlap. Its shows the mid-20th

century warm peak, followed by the latter 20th century cooling peak, just as the

instrumental Greenland annual mean temperature record does. However, instrumental Northern Hemisphere mean temperature has, in contrast, warmed markedly

during the latter 20th century.

The Greenland borehole temperature reconstruction may tell us something about

temperatures in Greenland over the past few millennia even though the two different Greenland borehole records show some differences between them. But these

results are unlikely to tell us much, if anything, about Northern Hemisphere mean

temperature trends. Indeed, Dahl-Jensen et al have never, to my knowledge,

claimed in their studies that that temperature variations in the two regions of

Greenland reconstructed (which themselves show significantly different histories

over the past 1000 years) are representative of Northern Hemisphere mean temperatures, and I would be surprised if the authors were comfortable in having their

data represented as such.

Question 50. In your view what should the Federal Government do in response

of rising concentrations of CO2? What would be the climate impact of this effort?

Response. In my view, the Congress and the Federal Government should be taking the scientific findings of the mainstream research community very seriously and

should stop focusing so much attention on the poorly conducted and distracting

nitpicking of the various contrarian scientists. The IPCC assessments represent the

most authoritative reviews of the science and have been unanimously endorsed by

all of the participating nations of the world—it is time to pay attention to their findings. Exactly what steps should be taken and how fast this should be done are policy questions that members of this body should be responsibly and thoughtfully addressing. The long residence timescales of anthropogenic greenhouses gases, and the

lags in the response of the climate system (e.g. sea level rise) to already realized

increases in greenhouse gas concentrations dictate, however, that there are potentially significant costs to delayed action.

Question 51. Approximately what percentage of the temperature increase in the

observational record over the last 100 years would you attribute to anthropogenic

causes? What percentage would you attribute to increased urbanization? What percentage would you attribute to non-urbanized land use changes? What percentage

would you attribute to natural (solar, volcanic, etc.) variability? What percentage

would you attribute to ‘‘internal’’ climate variability? What percentage would you

say results from other or unexplained sources? Give estimates for the years

1900,1940, 1980 and 2000.

Response. A cursory review of the available evidence (see e.g. Figure 2.1 of chapter 2 of the 2001 IPCC Scientific Working Group report) indicates the following ap-
193

proximate attributes in the observed record of global mean temperature changes

over the past 100 years: a warming of approximately 0.3° C to 1940, a statistically

insignificant change (given the uncertainties) from 1940 to the mid-1970’s, and then

an additional warming of approximately 0.5° C from 1970 to 2000. This pattern of

behavior is reproduced closely by models driven with estimates of both natural and

anthropogenic forcing of the climate during the 20th century. The period of relative

stasis in global mean temperatures from 1940 to 1970, in these model simulations,

appears to result from the cooling impact of anthropogenic aerosols (for which there

was a large increase during that time period) as well as a potential cooling contribution from explosive volcanic eruptions that occurred during that period, which tended to offset the warming influence of increased greenhouse gas concentrations during that time period (e.g. the 1957 eruption). However, much of the overall warming

of the globe during the 20th century (which is between 0.6° C and 1.0° C depending

on the precise instrumental data set used, and the precise endpoints of the interval

examined) is clearly a result of increased greenhouse gas concentrations, as established in these simulations, consistent with the conclusions of the IPCC Third Assessment Report that most of the warming of the past 50 years is attributable to

human influences.

Question 52. What was the earth’s climate like the last time the atmospheric concentration of carbon dioxide was near today’s level of about 370 parts per million

(ppm) and what were past conditions like when concentrations were at 550 ppm?

Detail the factors that cause the global carbon cycle to produce these high levels

of atmospheric carbon dioxide.

Response. It is not precisely known what the ‘‘earth’s climate’’ was like the last

time carbon dioxide levels were near 370 ppm (let alone 550 ppm) because the available paleoclimate evidence available this long ago are quite uncertain and incomplete. That having been said, it is believed, based on the available proxy information

and faunal/floral evidence, that global temperatures were probably several degrees

higher than they are today when CO2 concentrations neared 550 pm, roughly consistent with model simulation results. One probably has to go back roughly 40–50

million years ago (see chapter 3 of the 2001 IPCC working group 1 report) to find

a time when CO2 concentrations were in the range of 550 ppm (i.e., roughly double

their pre-industrial concentration) and approximately 80 million years ago (i.e., the

mid-Cretaceous period when Dinosaurs roamed the polar regions) to find a time

when CO2 levels were in excess of 1200 ppm (a level that will be reached, at current

rates of CO2 increase, within 1 to 11⁄2 centuries). Proxy evidence available for this

period, tenuous though it is, suggests deep ocean temperatures 8–12° C warmer

than present. State of the art climate model simulations performed by Bette OttoBleisner and colleagues using the National Center for Atmospheric Research

(NCAR) global climate model, which incorporate such CO2 levels (and the continental configuration corresponding to the mid-Cretaceous period), indicate significantly warmer sea surface temperatures, with tropical sea surface temperatures approximately 4° C warmer and polar sea surface temperatures approximately 6–14° C

warmer than present. The simulations indicate an absence of perennial sea ice at

even the most polar latitudes.

Question 53. In your vitae, you indicate that you serve on the panel for NOAA’s

Climate Change Data and Detection (CCDD) program, while at the same time, you

also have received large grants from this program. Please explain your role on the

panel, how grant submissions are evaluated, and why there is no conflict of interest

or impropriety associated with members of a panel receiving large grants from the

program for which they serve.

Response. I am not a spokesperson for NOAA, and would suggest that the questioner contact the appropriate NOAA agency officials for further information on

their conflict of interest and disclosure policies. That notwithstanding, however, I

would note the following points. Government funding agencies seek to draw upon

the leading experts of the field in their panels. Inevitably, this means that specific

science programs within NSF and NOAA invite to their review panels scientists who

typically submit proposals themselves to those panels. Scientists are also asked to

disclose any conflicts of interest they might have in reviewing a proposal, and are

asked to recuse themselves from any participation in discussions related to proposals that they might have even peripheral involvement with. In my involvement

in both NSF and NOAA panel reviews, I have on many occasions recused myself

from reviewing or discussing a proposal based on such considerations.

Question 54. Do you receive any income or reimbursement (travel, speaking fees,

etc.) from any sources, which have taken advocacy positions with respect to the

Kyoto Protocol, the U.N. Framework Convention on Climate Change, or legislation
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before the U.S. Congress that would affect greenhouse gas emissions? If so, please

identify those sources and the approximate amount of money that they represent.

Response. All income or travel expense reimbursement funds that I have received

to my recollection have come from academic institutions, government funding agencies such as NSF, NOAA, NASA, DOE, and scientific organizations such as the

American Geophysical Union and University Corporation for Atmospheric Research

(UCAR). I am not familiar with any advocacy positions that have been taken by any

of these institutions or organizations regarding the U.N. Framework Convention on

Climate change, or legislation before the U.S. Congress that would affect greenhouse

gas emissions.

RESPONSES BY MICHAEL MANN TO ADDITIONAL QUESTIONS FROM SENATOR JEFFORDS

Question 1. Is it your understanding that during the mid-Holocene optimum period (the period from 4000–7000 B.C.) that annual mean global temperatures were

more than a degree C warmer than the present day?

Response. This is an oft-repeated but patently false claim. Dr. Legates, who has

no established expertise in the relevant field of paleoclimatology, indeed asserts that

temperatures were warmer at this time. In fact, not only is that not the consensus

of the paleoclimate research community, but just the opposite is believed to be true

of global annual mean temperatures at this time. Paleoclimate experts know that

the mid-Holocene warmth centered roughly 5000 years ago was restricted to high

latitudes and certain seasons (summer in the Northern Hemisphere and winter in

the southern hemisphere). Because much of the early paleoclimate evidence that

was available (for example, fossil pollen assemblages) came from the Northern

Hemisphere extratropics, and is largely reflective of summer conditions, decades ago

some scientists believed that this was a time of globally warmer conditions. It is

now well known that this is not the case. More abundant evidence now demonstrates, for example, that the tropical regions were cooler over much of the year.

All of these changes are consistent with the expected response of surface temperatures to the known changes in the Earth’s orbital geometry relative to the Sun during that time period and associated climate feedbacks, as detailed in peer-reviewed

scientific publications [e.g., Hewitt, C.D., A Fully Coupled GCM Simulation of the

Climate of the Mid-Holocene, Geophysical Research Letters, 25 (3), 361–364, 1998;

Ganopolski, A., C. Kubatzki, M. Claussen, V. Brovkin, and V. Petoukhov, The Influence of Vegetation-Atmosphere-Ocean Interaction on Climate During the Mid-Holocene, Science, 280, 1916–1919, 1998].

Climate model simulations indicate quite good agreement with paleoclimate evidence now available. These models calculate that global annual average temperatures were probably a few tenths of a degree C cooler than today during this time

period [Kitoh, A., and S. Murakami, Tropical Pacific Climate at the mid-Holocene

and the Last Glacial Maximum simulated by a coupled ocean-atmosphere general

circulation model, Paleooceanography, 17 (3), (19)1–13, 2002.]. That’s a far cry from

the very out-of-date claim made by Legates. Legates’ comments regarding climate

changes over the past 1000 years reflect a similar lack of familiarity with a whole

body of paleoclimate research, especially with the new insights gained through the

augmented research program, during the past decade.

Question 2. Why only focus on the past 1000 or 2000 years and not further back?

Response. Large changes in climate certainly occurred in the distant past. If we

look million years back in time, dinosaurs were roaming the polar regions of the

Earth, and the globe was several degrees wanner than today. Carbon dioxide levels

were probably several times their current level, slowly having attained such high

levels due to changes in the arrangements of the continents (‘plate tectonics’) which

influence the volcanic outgassing of carbon dioxide from the solid Earth. These

changes occurred on timescales of tens of millions of years. Going back 10,000 years

ago, large ice sheets existed over North America due to natural changes that occur

in the Earth’s orbit around the Sun on timescales of tens of thousands of years. Trying to study distant past climates for insights into modern natural climate variability is hampered by the fact that the basic external constraints on the system (the

continental arrangement, the geometry of the Earth’s astronomical orbit, the presence of continental ice sheets—what we call the ‘boundary conditions’) were significantly, different from today. Focusing on the evolution of climate in the centuries

leading up to the 20th century (i.e., the past 1000 to 2000 years) provides a perspective on the natural variability of the climate prior to the period during which largescale human influence is likely to have occurred, yet modern enough that the basic

boundary conditions on the climate system were otherwise the same. This provides

us, in essence, ‘control’ for diagnosing whether or not recent changes in climate are
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indeed unusual. Moreover, only during the past 1000–2000 years do we have adequate networks of proxy climate data with the required (annual) resolution in time

to compare and validate against modern instrumental records; Reliable quantitative

reconstructions of large-scale surface temperature patterns further back in time are

thus not, at present, possible.

Question 3. One of the Northern Hemisphere temperature reconstructions in your

Figure 1 (the green curve from a paper by Esper and colleagues from Science in

2001) shows larger swings in past centuries, marginally outside the uncertainty

bounds of the other reconstructions and model simulations. Does this indicate internal inconsistency in our knowledge?

Response. There is no inconsistency. Esper et al noted, in their paper, that their

estimate, unlike that of my colleagues and mine (the Mann/Bradley/Hughes or

‘‘MBH’’ reconstruction), was not representative of the entire Northern Hemisphere.

They explicitly noted this in their paper, where they pointed out the likely reason

for differences is that the MBH reconstruction represents the full Northern Hemisphere (tropics, subtropics, and extratropics) while the Esper et al reconstruction

only represents the restricted extratropical continents. In fact, in a Science article

that appeared in the same issue as the Esper et al paper [Briffa, K.R. and T.J.

Osborn, Science, Blowing Hot and Cold, 295, 2227–2228, 2002] Briffa and Osborn

noted that much of the difference was due to an arguably inappropriate scaling that

Esper et al used, and an inappropriate comparison of summer vs. annual temperatures; ‘‘when we regressed the record of Esper et al. against non-smoothed data (see

the figure), this difference (with MBHJ was reduced to about 0.4° C. Recalibrating

both curves against year-by-year warm season temperatures reduces this difference

further to about 0.35° C.’’

As shown in the ‘‘Eos’’article discussed in my testimony, which represents a consensus of the leading researchers in the field [Mann, ME, Ammann, C.M., Bradley,

R.S., Briffa; K.R., Crowley, T.J., Hughes, M.K.; Jones, P.D., Oppenheimer, M.,

Osbom, T.J., Overpeck, J.T., Rutherford, S., Trenberth, K.E., Wigley, T.M.L., On

Past Temperatures and Anomalous Late 20th Century Warmth, Eos, 84, 256–258,

2003], a proper scaling of Esper et al record prior to comparison with other estimates, shows it only marginally outside the error estimates of the MBH reconstruction and the many other estimates that are in agreement with it. As noted in two

articles in Science that shortly followed the Esper et al paper [Mann, M.E., Hughes,

M.K., Tree-Ring Chronologies and Climate Variability, Science, 296, 848, 2002;

Mann, ME, The Value of Multiple Proxies, Science, 297, 1481–1482, 2002], it is likely that the emphasis of the Esper et al reconstruction on only the summer season

and the extratropical continental regions, provides a biased estimate of the true pattern of annual, hemisphere-wide temperatures in past centuries, explaining the

small differences between this estimate and other estimates. This conclusion has

been verified in recent modeling studies [Shindell, D.T., Schmidt, G.A., Miller, R.,

Mann, M.E., Volcanic and Solar forcing of Climate Change During the Pre-Industrial era, Journal of Climate, in press, 2003 ]. It is thus clearly disingenuous when

contrarians make the argument that the Esper et al result is in conflict with the

mainstream conclusions of the climate research community with regard to the history of Northern Hemisphere mean annual temperature variations over the past

millennium as embodied, for example, in the Eos article.

Question 4. As climatologist, can you explain what kind of quantitative analysis

it takes to determine whether or not the last 50 years has been unusually warm

compared to the last 1000 years?

Response. Well, such an analysis requires the careful use of proxy data, because

we don’t have widespread instrumental temperature records prior to the mid-19th

century. By ‘careful use’: I mean that one must first establish that the records actually resolve the changes of the past 50 years. This typically requires annually resolved proxy records or the very circumspect use of records with decadal resolution.

One must not, as in the Soon and Baliunas’ studies, use records that do not resolve

the trends of the past few decades. One must also establish the existence of an actual temperature signal in the available proxy data before using them to reconstruct

past temperature patterns, and one must properly synthesize regional data, which

typically all show different tendencies at any given time, into an estimate of the average temperature over the entire hemisphere or globe. There area number of ways

of performing such a synthesis, from the sophisticated pattern reconstruction approaches my colleagues and I have described in the technical literature, to the relatively straightforward compositing approach that many other paleoclimatologists,

(including myself) have also used. In all cases, the estimates based on the proxy

data must be calibrated against modern instrumental temperature measurements,

to allow, for a quantitative estimate of past temperatures. The estimate must then
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be independently verified or, what we call, ‘cross-validated,’ by showing that it independently reproduces earlier instrumental data that were not used to calibrate the

estimates. Finally, uncertainties must be diagnosed based on how well the reconstruction describes actual available instrumental measurements. Once such steps

have been taken, it is possible to compare the recent instrumental record to the reconstruction within the context of the uncertainties of the reconstruction. This latter

comparison allows us to gauge whether or not late 20th century temperatures are

anomalous or not in a long-term context. The conclusion from legitimate such studies that late 20th century warmth is indeed anomalous in a millennial or longerterm context has been shown to be quite robust with respect to the details of the

data set used, or the methodology used (as shown in exhibit 1 in my testimony, the

first figure of the ‘‘Eos’’ piece). It is noteworthy that the Soon and Baliunas paper

satisfies none of the required standards for a ‘careful use of proxy data’ specified

above.

Question 5. Do you claim that appropriate statistical methods do not exist for calibrating statistical predictors, including climate proxy records, against a target variable, such as the modern instrumental temperature record?

Response. No. The statement belies a centuries-old field of statistics known as

‘‘multivariate linear regression’’ in which a set of candidate ‘‘predictors’’ (such as

proxy data) are statistically related to a target variable or ‘‘predictand’’ (such as the

instrumental temperature record) during a common interval of overlap (e.g., the

20th century). If done properly, this statistical method isolates the temperature information that is contained within the proxy data, and uses that information to reconstruct past temperature patterns from the proxy data. It is also well known to

those properly trained in statistics that the ‘‘regression model’’ must be independently ‘‘validated’’ by showing that it successfully reproduces independent data (e.g.

longer-term instrumental temperature records) that were not used in constructing

the statistical model itself. The estimates by Mann and colleagues embrace each of

these fundamental statistical principles.

Legates in his testimony seemed to claim that a composite estimate (e.g. of Northern Hemisphere mean temperature) should somehow resemble each of the individual predictors (e.g. the various regional temperature estimates). Such a result is,

in general, a statistical impossibility. There is a basic theorem in statistics known

as the ‘‘central limit theorem’’ which indicates a general tendency for a composite

(i.e. average) of a large number of different individual estimates to cancel out in

terms of the pattern variation and amplitude of variability evident in the individual

estimates. If Legates were indeed (as he claims to be) familiar with the instrumental surface temperature record, he would know, for example, that individual instrumental thermometer records available for particular locations over the globe

during the 20th century show very little in common with the ‘composite’ series constructed by averaging all of the individual records into a hemispheric or global estimates. Because season-to-season and year-to year fluctuations in the climate at regional scales often result from shifts in the atmospheric circulation, not every location experiences the same variation in any given year; for example, this summer,

the western United States and Europe are anomalously warm, while the East Coast

is anomalously cool. The average series reflects a tendency for a cancellation of the

various ‘‘ups’’ and ‘‘downs’’ in the different individual series that often occur at different times. This is simply a statement about the instrumental record itself, and

requires no use of proxy data at all. It is discouraging that Legates and colleagues

haven’t performed even such simple analyses with available instrumental data that

would expose the fundamental flaws in their supposed ‘statistical’ reasoning.

In this context, it should be noted that Legates testimony seriously misrepresents

the statistical analyses used by Mann and co-workers. In his testimony, Legates

claimed that my collaborators and I replaced the proxy data for the 1900’s by the

instrumental. The assertion is simply factually incorrect. Any reader of our published work knows full well that our proxy-based temperature reconstruction extends well into the late 20th century, through 1980 (the vast majority of published

high-resolution climate proxy data are not available at later times than this). It is

shown in our work that the reconstruction independently reproduces estimates from

the instrumental surface temperature data record back through the mid-19th century and, in certain regions, back through the mid-18th century (i.e., our regression

model is ‘‘validated’’ in the manner discussed above). Our Northern Hemisphere average temperature series reconstructed from proxy data is shown to agree with the

instrumental Northern Hemisphere average record over the entire interval available

for comparison (1856–1980). This successful validation of the reconstruction, furthermore, allows us to compare the proxy-based reconstruction to the entire instru-
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mental record (available through 1999 at the time of our publication), taking into

account the uncertainties in the reconstruction.

Legates further claim that we present the instrumental record without uncertainty is disingenuous. If Legates, for example, were familiar with studies of the instrumental surface temperature record, he would understand that the uncertainties

in this record using the 20th century are minimal compared to the uncertainties

shown for our reconstruction [see e.g. Figure 2.1b in Folland, C.K., Karl, T.R.,

Christy, J.R., Clarke, R. A.,Gruza, G.V., Jouzel, J., Mann, M.E., Oerlemans, J., Salinger, M.J.;, Wang, S.-W., Observed Climate Variability arid: Change, in Climate

Change 2001: The Scientific Basis, Houghton, J.T., et al. (eds.), Cambridge Univ.

Press, Cambridge, 99–181, 2001.]. Furthermore, all scientists with a proper training

in statistics know that uncertainties add ‘‘in quadrature’’, In other words, you have

to square them before adding them. This means that the relatively small uncertainty in the instrumental record makes a relatively small contribution to the total

uncertainty. Legates claimed in his testimony that including the uncertainty in the

instrumental record, which he estimates as 0.1° C would change the conclusions expressed by us and other mainstream climate scientists that the 1990’s are the

warmest decade in at least the past 1000 years within estimated uncertainties. This

claim is very misleading for several reasons, First, the standard error in Northern

Hemisphere mean annual temperatures during the 1990’s is far smaller than the

amount cited, by Legates [see again Folland et al, 2001 cited above]. Even more

problematic, however, Legates claim indicates a fundamental misunderstanding of

the statistical concepts of standard error and uncertainty,. The shaded region shown

along with the Mann et al reconstruction (and other similar plots shown in recent

articles such as the aforementioned ‘‘Eos’’ article, and the IPCC report) indicate two

standard error intervals. The decade of the 1990’s is roughly two standard errors

warmer (i.e., about 0.4° C) than any decade prior to the 20th century in the reconstruction. Based on a one-sided test for anomalous warmth, this translates to a

roughly 97.5 percent level of significance. Modifying the uncertainties to include the

small additional contribution due to uncertainties in the instrumental record itself

would modify this only slightly, and would not lower the significance level below the

95 percent level. Though there is no such thing as an absolute estimate of uncertainty, despite Legate’s implications to the contrary, a 95 percent confidence is often

adopted as an appropriate criterion for significance. Legates statement that including instrumental contributions to the uncertainty would change the conclusions is

thus clearly false.

Question 6. In determining whether the temperature of the ‘‘Medieval Warm Period’’ was warmer than the 20th century, does your work analyze whether a 50-year

period is either warmer or wetter or drier than the 20th century? Is it appropriate

to use indicators of drought and precipitation directly to draw inferences of past

temperatures?

Response. No, the work of me and my colleagues does not follow the flawed approach used by Soon and Baliunas. It is fundamentally unsound to infer past temperature changes directly from records of drought or precipitation. The analysis

methods used by my various collaborators and I (e.g. the 13 authors of the recent

article in Eos) employ standard statistical methods for identifying the surface temperature signal contained in proxy climate records, and using only that temperature

signal in reconstructing past temperature patterns. By contrast, Soon and Baliunas

simply infer evidence for warm ‘‘Medieval Warm Period’’ or cold ‘‘Little Ice Age’’ conditions from the relative changes in proxy records often reflective of changes in precipitation or drought, rather than temperature. It is difficult to imagine amore basic

mistake than misinterpreting hydrological evidence in terms of temperature evidence. This fundamental shortcoming in their approach is identified in the Eos article referred to in my testimony that was written by 13 leading climate and

paleoclimate scientists. Incidentally, the Eos piece was peer-reviewed, despite the

claim by Legates otherwise in his testimony—an associate editor with training in

the particular field corresponding to the submitted piece (‘‘Atmospheric Science’’ in

this case); reviews the content of Eos forum pieces prior to acceptance.

Question 7. Can you compare the quantitative analysis that supports your conclusion that the climate is warming faster in recent years than at any time in the recent past with the analysis done in the Soon literature review?

Response. Technically speaking, there is no actual ‘‘analysis’’ in the Soon and

Baliunas review, in that they don’t appear to have performed a single numerical or

statistical operation upon a single time series at all. They do not provide any quantitative estimates of temperature changes, let alone any estimate of uncertainties,

Instead, they claim to interpret the results of past studies mainly by counting the

number of studies coming to some conclusion; no matter how they got there and
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whether there have been later interpretations. Science requires analysis—not just

counting studies. Climate scientists whose records they analyzed have gone on

record as indicating that Soon and Baliunas misinterpreted their studies (e.g., the

article by David Appell in the August 2003 issue of Scientific American) and numerous climate scientists have indicated (see same article) that Soon and Baliunas misinterpreted evidence of drought or precipitation as evidence of temperature changes,

did not use records that resolve the climate changes of the late 20th century, and

did not take into account whether or not variations in different regions were coincident or not. Soon and Baliunas also neglect undeniable evidence of substantial

warming of hemispheric and global surface temperatures during the past few decades. So the Soon and Baliunas analysis fails just about every meaningful criterion

that might be applied to determining the validity of an analysis that purports to

evaluate current warming in the context of past temperature trends. This deeply

flawed study thus contrasts sharply with other rigorous quantitative studies (as discussed in the Eos article) performed by numerous other scientists with appropriate

training in the fields of climatology and paleoclimatology, which use proper statistical methods for inferring past temperature changes from proxy data, provide uncertainty estimates, and employ appropriate comparisons of current and past trends.

Question 8. What was the earth’s climate like the last time that atmospheric concentrations of carbon dioxide were at today’s levels or about 370 parts per million

(ppm) and what were conditions like when concentrations were at 550 ppm, which

will occur around 2060 or so?

Response. We have to go back far into the past to find carbon dioxide levels approaching today’s levels. Ice core studies indicate that modern carbon dioxide levels

are unprecedented for at least four glacial/inter-glacial cycles: in other words, for

more than 400,000 years. Other evidence suggests that carbon dioxide levels are

now higher than they have been for at least 10 million years. One probably has to

go back roughly 40–50 million years ago (see chapter 3 of the 2001 IPCC working

group 1 report) to find CO2 concentrations were in the range of 550 ppm (i.e., roughly double their preindustrial concentration) and approximately 80 million years ago

(i.e., the mid-Cretaceous period when Dinosaurs roamed the polar regions) to find

CO2 levels in excess of 1200 ppm (a level that will be reached, at current rates of

CO2 increase, within one to one-and-a-half centuries). Proxy evidence available for

this period, tenuous though it is, suggests deep ocean temperatures 8–12° C warmer

than present. State of the art climate model simulations performed by Bette OttoBleisner and colleagues using the National Center for Atmospheric Research

(NCAR) global climate model, which incorporate such CO2 levels (and the continental configuration corresponding to the mid-Cretaceous period), indicate significantly warmer sea surface temperatures, with tropical sea surface temperatures approximately 4° C warmer and polar sea surface temperatures approximately 6–14° C

warmer than present. The simulations indicate an absence of perennial sea ice at

even the most polar latitudes.

Question 9. Are you aware of any scientists beside the authors of the Soon et al

article who support using ‘‘wetness’’ or ‘‘dryness’’ as indicators of past temperatures,

instead of actual temperatures or proxy data that reflects temperatures?

Response. I am not aware of any other scientist who has made the mistake of interpreting paleoclimatic information in this way. As discussed above, trained

paleoclimatologists typically use statistical methods to identify the strength of the

temperature signal in a proxy record prior to using it in reconstructing past temperature patterns.

Question 10. Is there any known geologic precedent for large increases of atmospheric CO2 without simultaneous changes in other components of the carbon cycle

and the climate system?

Response. There is not, to my knowledge, such an example. As discussed above,

the geological record shows a clear relationship between periods of high CO2 and

relatively high global mean temperatures. The study of the relationship between

changes in CO2 and climate in the paleoclimate record is sometimes complicated by

the fact that these relationships can be relatively complex during rapid transitions

between glacial and interglacial climates such as those that occurred with the coming and going of ice ages that occurs on a roughly 100 thousand year timescale over

the past nearly one million years. However, one can turn to periods of time when

the climate and CO2 were not varying rapidly, and thus the climate was approximately in an ‘‘equilibrium’’ state, for insights into the relationship between CO2 and

climate, A perfect such example is the height of the last ice age, the so-called ‘‘Last

Glacial Maximum’’ or ‘‘LGM’’ centered roughly 25 thousand years ago. At this time,

CO2 was substantially lower than today (just below 200 ppm) and global mean sur-
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face temperatures were several degrees (about 4C or so) cooler than today. Such relationships between past CO2 changes and global temperature changes typically,

suggest a ‘‘sensitivity’’ of the climate system to enhanced CO2 of 1, 5 to 4.5 C warming for each doubling of CO2 concentrations from their pre-industrial levels, similar

to the range of sensitivities found in various climate models.

Question 11. According to a study published in Science magazine recently [B. D.

Santer; M. F. Wehner, T. M. L. Wigley, R. Sausen; G. A. Meehl, K. E. Taylor, C.

Ammann, J. Arblaster, W. M. Washington, J. S. Boyle, and W. Bru ̈ ggemann Science

2003 July 25; 301; 479–483], manmade emissions are partly to blame for pushing

outward the boundary between the lower atmosphere and the upper atmosphere.

How does that fit with the long-term climate history and what are the implications?

Response. This is yet another independent piece of evidence confirming a detectable anthropogenic influence on climate during the late 20th century. This evidence

is consistent with evidence for unprecedented surface warming during the past few

decades—warming that indeed appears unprecedented for as long as we have

records (i.e., for at least a thousand, and probably two thousand years). These

changes, moreover, are consistent with predictions from climate models driven by

known anthropogenic (human) forcing of the climate.

Question 12. At this hearing, there were a number of calls for ‘‘sound science.’’

Could you please explain what it is about the IPCC process that justifies respecting

the IPCC results as the very soundest representation of the science of climate

change?

Response. The IPCC carries out a process for developing its summarization of the

understanding of science that leads to one of the most rigorously peer-reviewed scientific documents in existence, Individual technical chapters are prepared by expert

scientific teams that consider the full range of published papers in a subject area.

This expert author team then solicits an initial peer review from a large number

of other scientists in the field, drawing on those with the full range of views. The

reports next go through a much wider review that is open to literally thousands of

scientists around the world. Finally countries, NGOs, and professional groups (such

as business groups) are provided the opportunity to send in review comments. At

each stage, authors consider each comment and document their response. The meticulousness and fairness of the revision process by the authors in response to reviewer comments is evaluated by an independent pair of ‘‘review editors’’ who are

themselves top international climate scientists who are not authors of the report

itself. The National Academy of Sciences, at President George W. Bush’s request,

and other national academies around the world have independently reviewed the

process and the validity of the scientific findings of the IPCC and endorsed them.

To question the IPCC and the IPCC process, as does Dr. Legates thus not only does

a disservice to thousands of the world’s top scientists; but to the exceptional care

and rigor of the process that has led to the unanimous adoption of all of the IPCC’s

assessments by representatives of the over 150 nations that participate in the IPCC

process. The documents are very finely honed and carefully phrased. The scientific

studies of those such as or, Legates are considered, as are their review comments,

and it is terribly disingenuous, not to mention totally unacceptable to the international community, after all of the care and consideration put into these efforts to

try to so cavalierly dismiss them.

In his testimony Legate’s alleges that the IPCC report misrepresents what is

known about climate change in past centuries and that it somehow replaces conventional wisdom with dramatically new conclusions. One must conclude that Legates

either did not read the report, or if he did, he did not understand what he read;

for if he had he would certainly have to recognize factually incorrect nature of his

comments. The IPCC chapter dealing with paleoclimatic evidence discussed the full

range of regional evidence described in the peer-reviewed as well as evidence from

hemispheric composites that average the information from different regions. The

paper by Soon and Baliunas is a dramatic throwback to the State of our knowledge

many decades ago, while the IPCC report provides a far more upto-date assessment

of all of the available knowledge regarding past climate change. The Soon and

Baliunas papers provide a glaring example of the very ‘‘unsound’’ science that Senator Inhofe claims to be concerned about, as numerous mainstream climate researchers have now opined in the media, and in the peer-reviewed scientific literature.

Question 13. In your opinion, how do the processes used by the IPCC and the National Academy of Sciences compare to the process used in the publication of the

Soon and Baliunas paper and other papers by so-called ‘‘contrarians’’? In the next

IPCC assessment, would you expect that the Soon and Baliunas paper will be con-
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sidered and cited, putting it into the context of other papers and findings and explaining why it has differences or similarities?

Response. As discussed above, the IPCC is one of most rigorously peer-reviewed

scientific documents in existence. By contrast, the contrarians rarely publish in the

peer-reviewed literature and when they do, it is not uncommon to discover, as in

the case of the Soon and Baliunas paper, irregularities in the peer-review process.

Publisher Otto Kinne indeed indicated that the review process at Climate Research

‘‘failed to detect methodological flaws’’ in the Soon and Baliunas paper. I would indeed expect that in the next IPCC assessment, the Soon and Baliunas paper will

be discussed and evaluated in the context of other available evidence and in the context of how it is faring in the literature when the IPCC review takes place (e.g.,

if there are as many criticisms about their work as at present, and they have not

been seriously addressed by more careful followup studies by the authors. I would

think their conclusions will be rejected as scientifically unsound. I would not presume to know in detail what the result of the assessment will be, but I believe it

fair to assume that the rigorous review provided by the IPCC assessment process

will not fail to identify the methodological flaws that appear to have slipped through

the cracks in their publication in the journal ‘‘Climate Research’’.

Question 14. Could you explain the IPCC’s lexicon for indicating relative levels of

confidence and how you would suggest this relates to the information being ‘‘real’’

and ‘‘probable’’? When IPCC says something is ‘‘very likely,’’ just what do they

mean?

Response. To avoid the type of misunderstanding that often results from when scientists seek to convey scientific results to a non-technical audience, the IPCC specifically sought to employ a lexicon in which terms such as ‘‘likely’’ or ‘‘probable’’

or ‘‘very likely’’ had specific statistical meanings attached to them. A fairly conservative standard was typically employed in this process. Consider the conclusion in

the IPCC report that the 1990’s are the warmest decade in at least the past 1000

years for the Northern hemisphere average temperature. This conclusion is based

on the fact that the average warmth of the 1990’s exceeds that for any reconstructed

decade in the reconstructed Northern Hemisphere series. To be more specific, the

1990’s warmth exceeds any past decade by two standard errors. This corresponds

to a roughly 97.5 percent probability based on standard statistical assumptions.

Probabilities of 90 percent–99 percent are termed ‘‘very likely’’ in lexicon typically

adopted by the IPCC report. However, this conclusion was offered as only ‘‘likely’’

(corresponding to a 66 percent–90 percent level of probability) rather than the more

stringent ‘‘very likely’’ because it was based on only a small number of independent

studies at the time. Since that time, of course, several more studies have affirmed

this conclusion, and one might imagine that a more stringent conclusion will be offered in the future. This example nonetheless illustrates the manner by which IPCC

adopted conservative standards in their use of terms such as ‘‘likely’’ or ‘‘very likely’’. It is instructive to contrast that standard with the one taken in the Soon and

Baliunas paper. The Soon and Baliunas paper does not provide a quantitative estimate of any quantity (such as average Northern Hemisphere temperature), or any

assessment of uncertainty. It is thus not possible for the authors to attach any

meaningful statement of likelihood or probability to any of their conclusions. They

thus provide no basis for judging the validity of any of the claims made in their

paper, in striking contrast to the rigorous standards adopted by IPCC, and by the

work of my collaborators and me.

Question 15. In his questioning, Senator Inhofe cited results regarding the potential costs of implementing the Kyoto Protocol from the Wharton Econometric Forecasting Association (WEFA). I realize that you are not an economist, but would you

please comment as a scientist on the following two points:

(a) Senator Inhofe cited economic projections (e.g., 14 percent increase in medical

costs; real income drop of $2,700 per household) going out a decade or so into the

future and without any indication of uncertainty on these estimates implying an accuracy of two-significant figures. Senator Voinovich cited numbers to similar

claimed accuracy going out 20–25 years; again without any indication of uncertainty. Could you please comment on what you think are the relative strengths and

weaknesses of making climate projections based on use of physical laws versus economic extrapolations and what sorts of relative uncertainty should likely be associated with each type of estimate so that they can be interpreted in a comparative

way by decisionmakers?

Response. Indeed, it is somewhat remarkable that politicians who reject the validity, for example, of climate model simulations, which are based on solution of the

laws of physics, can so uncritically accept precise economic projections based on economic forecasts based on untestable and unverifiable assumptions governing human
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decisionmaking, and speculative future scenarios that depend on the unfolding of

the political process. Specific numbers of ‘‘14 percent’’ or ‘‘$2,700’’ are of course entirely dependent on the assumptions that go into such forecasts. Because assumptions about future economic growth and about future government policies are necessarily uncertain, estimates of changes in costs or income from such models must

also be quite uncertain, and so should have large uncertainties (or ranges) associated with them. The faith expressed in such poorly constrained economics estimates

by the same individuals who express strong skepticism of results from far more

physically based and testable climate simulation models, strikes me as a remarkable

inconsistency.

(b) Because you may be familiar with the 1997 study by the World Resources Institute entitled ‘‘The costs of climate protection: A guide for the perplexed,’’ which

explains the important role of assumptions in leading to very different cost estimates from even one economic model, much less among different models, could you

explain in a comparative fashion how robust the findings regarding the ‘‘hockey

stick’’ behavior of the climate in the various studies carried out: by you and fellow

investigators may be to variations in the assumptions made. It’s clear that varying

the assumptions among reasonable possibilities in the economic models can change

what is calculated to be a few percent impact on the economy to a small gain; would

changes in the assumptions you are making change the indication of strong anthropogenic warming to an indication of human-induced cooling?

Response. The millennial temperature reconstruction (or ‘‘hockey stick’’ as it was

termed by former GFDL head Dr. Jerry Mahlman) is based on a rigorously validated statistical model with demonstrated predictive skill based on comparisons

with independent data. The primary conclusions drawn from the reconstruction (e.g.

the anomalous nature of late 20th century warmth) are based on a conservative appraisal of the uncertainties in the reconstruction, and are not strongly dependent

on the assumptions made. The same—conclusions have been affirmed now by several other independent empirical and-model-based estimates. As discussed above,

this contrasts with economic predictions which are necessarily far more sensitive to

the assumptions that go into them.

Question 16. In his opening statement, Senator Inhofe concluded that the Soon

and Baliunas paper is ‘‘credible; well-documented; and scientifically defensible.’’ By

contrast, your testimony indicated that the experts in the field do not consider this

to be the case. Does one have to be an expert in the field to understand the apparent problems with this paper? If not, could you summarize in terms for non-scientists what the key problems with the paper are?

Response. The mainstream scientific research community has indeed rejected the

approach, interpretation, and conclusions advanced by Soon and Baliunas as fundamentally unsound. The major flaws in the analysis, as described in earlier comments in more detail, are basic enough that they can be understood by a non-specialist. In short, the analysis by Soon and Baliunas is unsound because (a) they inappropriately interpreted indicators of past precipitation as evidence of past temperature changes, (b) they did not use an approach which takes into account the

simultaneity and lack of simultaneity of variations in different regions, and (c) they

did not employ a proper standard for evaluating recent changes (i.e., changes during

the past few decades) in the context of past variations. Indeed, they also misinterpreted past published work, and did not provide any quantitative estimates, let

alone estimates of uncertainty. It is difficult to find anything of scientific merit at

all in their published work.

Question 17. As I understand it, the data that both you and Soon and Baliunas

draw from is the same, and it is not a question of the data being the problem. Instead, it is apparently the processing of the data that you are indicating has been

done in a substandard way by Soon and Baliunas. Is this correct?

Response. Keep in mind that Soon and Baliunas, unlike my collaborators and I,

don’t actually analyze any data at all. They simply claim to have ‘interpreted’ past

studies (often incorrectly). Soon and Baliunas refer to a number of proxy data studies that describe data which we employed in our analysis. There are also many

proxy data that we used in our study that the Soon and Baliunas do not discuss.

However, as alluded to in the question, the real issue isn’t what data were used.

Numerous independent now-published studies employing widely different assemblages of proxy climate data sets have demonstrated (e.g, as in the Eos article discussed earlier) a similar pattern of past variations in hemispheric mean temperature. The real issue with Soon and Baliunas is indeed not the set of studies that

they claim to have interpreted, but rather the approach that they took to interpreting those studies. As indicated in previous comments, Soon and Baliunas, unlike

mainstream climate researchers, did not employ a method for isolating the actual
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temperature signal in the proxy records before using the records to draw conclusions

regarding past temperature changes. Unlike mainstream researchers, they did not

aggregate information in a way that addresses whether or not variations in different

regions are simultaneous. Unlike mainstream researchers, they did not analyze the

actual modern (late 20th century) warmth in the context of past variations. And finally, they did not even produce a quantitative estimate of past temperature variations, let alone an estimate of uncertainty.

Question 18. The Soon et al literature review has been described as shifting the

paradigm away from the ‘‘hockey stick’’ description of global warming. It seems that

that review simply attempted to revive an older theory of climate change that has

been discarded by NOAA, the USGCRP, the NAS, the IPCC, etc. Please comment.

Response. The mainstream scientific community has clearly and decisively rejected the Soon and Baliunas papers as scientifically unsound which undermines

any claims made by industry-funded special interest groups or politicians, that the

papers provide any valid scientific conclusions, let alone the basis for a shift of the

‘‘paradigm’’. Indeed, the Soon and Baliunas papers simply promote a number of

long-discredited myths which have been replaced, in recent decades by far more rigorous and quantitative analyses as described by the IPCC, USGCRP, NAS, and

other mainstream scientific organizations and funding agencies. In short, the Soon

& Baliunas papers simply repackage myths that were discredited more than a decade ago.

Question 19. In an opinion-editorial by former Secretary of Energy James Schlesinger, he suggested that ‘‘we have only a limited grasp of the overall forces at work,

. . .’’ in terms of global climate change. Could you please summarize for us what

the scientific community considers the key forces at work over the past 1000 years,

how well these estimates are understood, and whether there is a general consistency

or inconsistency between the various forcings and the climate estimates that you

and colleagues have developed for the last 1000 years?

Response. Mr. Schlesinger’s assertions entirely mischaracterize the nature of our

scientific knowledge, which has advanced tremendously during the past several decades. In fact, a very large number of peer-reviewed scientific studies have been published in the leading scientific, journals such as Nature and Science in the past two

decades elucidating the role of natural and anthropogenic factors in observed climate changes. Physically based models have been developed and validated against

observations, and these models reproduce complex climate phenomena such as El

Nin ̃ o. These same models have been driven with the primary ‘‘external’’ factors that

are believed to govern climate variations on timescales of decades and centuries.

These external factors include natural factors, such as the modest estimated variations in radiative output of the Sun, which varies by a fraction of a percent over

time, variations in the frequency and intensity of explosive volcanic eruptions, which

have a several-year cooling effect on the climate through the injection of reflective

volcanic aerosols into the stratosphere, and very small changes in the Earth’s orbit

relative to the Sun that occur on multi-century timescales. These external factors

also include the ‘‘anthropogenic’’ influences of increased greenhouse gas concentrations due to fossil fuel burning, changes in the reflective properties of the land surface due to human land use alterations, and the regional cooling effect of anthropogenic sulphate aerosols in certain industrial regions. When driven with these factors, these climate models have demonstrated a striking ability to reproduce observed global and hemispheric temperature trends during the 20th century, as well

as longer-term trends in past centuries as reconstructed from proxy data. Such results are nicely summarized in the 2001 IPCC scientific working group report. Mr.

Schlesinger would have benefited from a reading of this report, or the follow-up National Academy of Sciences report that endorsed the key IPCC conclusions, prior to

writing his oped piece, which reflects a decades-old understanding of the State of

the science.

Question 20. In Dr. Soon’s testimony, he speaks about there being ‘‘warming’’ and

‘‘cooling’’ for different periods. If he did not construct an integral across the hemisphere or a real timeline; can he say anything other than that there were some

warm periods and cool periods?

Response. Aside from not adequately distinguishing temperature changes from

hydrological changes, Dr. Soon and his collaborators indeed did not even attempt

to estimate contemporaneous patterns of past temperature change, let alone an integral across the hemispheric domain to assess hemispheric mean temperature

changes. It is unclear what, if any, meaningful conclusions can be drawn from the

Soon and Baliunas study.
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Question 21. Dr. Soon indicates that ‘‘local and regional, rather than global average changes are the most relevant and practical measure of climate change and its

impact.’’ Could you please comment on this, including the relative likelihood of identifying a signal of climate change amidst the local fluctuations? In what sense might

local changes be the most practical measure? In that the primary forcings of the climate are global in scale, does it not make most sense to first determine how the

large-scale rather than the regional climate might be affected?

Response. Dr. Soon’s comments are truly misguided. Firstly, the surface temperature reconstructions published by my colleagues and I explicitly resolve regional patterns of surface temperature, so it is entirely unclear why Dr. Soon believes that

we don’t address regional climate changes. Had Dr. Soon understood our papers, he

would be aware that we do. However, unlike the study that Dr. Soon published, our

reconstructions explicitly take into account the issue of the relative timing and simultaneity of surface temperature changes in different regions. Only through doing

this it possible to form an integrated measure of temperature changes such as hemispheric mean temperature. Scientists with training in climatology, statistics; and

other areas of research required in the study of paleoclimate reconstruction know

that the signal-to-noise ratio of any surface response to global radiative climate forcing increases as the scale of spatial averaging increases, In discussions of climate

change it is thus the integral of the surface temperature field over an entire hemisphere or globe, which constitutes the most useful single variable for detecting, and

attributing causal factors to observed changes. The spatial signature of the surface

temperature signal (both with respect to position on the surface of the Earth, and

altitude in the atmosphere) can nonetheless help to distinguish one source of climate forcing (e.g. solar) from another (e.g. enhanced greenhouse gases). My colleagues and I have indeed used the spatial patterns of surface temperature changes

in past centuries to identify the role of natural external forcing of climate [Shindell,

D.T., Schmidt, G.A., Mann, M.E, Rind, D., Waple, A., Solar forcing of regional climate change during the Maunder Minimum, Science, 294, 2149–2152, 2001; Waple,

A., Mann, M.E., Bradley, R.S., Long-term Patterns of Solar Irradiance Forcing in

Model Experiments and Proxy-based Surface Temperature Reconstructions, Climate

Dynamics, 18, 563–578, 2002; Shindell, D.T., Schmidt, G.A., Miller, R., Mann, M.E.,

Volcanic and Solar forcing of Climate Change During the Pre-Industrial era, Journal of Climate, in press, 2003]. Both Dr. Soon and Dr. Legates advocate in their testimony a primary role of solar forcing in recent climate change, though they provide

no quantitative justification for this assertion at all. In fact, nearly a dozen detailed

‘‘detection’’ and ‘‘attribution’’ studies published during the past decade by leading

climate researchers in the premier international scientific peer-reviewed journals

such as Science and Nature, have shown that the vertical and horizontal pattern

of observed warming is inconsistent with the response of the climate to solar forcing,

but is consistent, with the response of the climate to anthropogenic forcing. Thus

a prudent use of spatial information, as described in various studies by leading climatologists, including my collaborators and I, can potentially help elucidate the

roles of natural and anthropogenic factors. However, Dr. Soon’s studies are deficient

in their use of any such information, and provide no insights into the factors governing past climate change.

Question 22. This year, the western United States is anomalously hot and dry.

The eastern United States is wetter than it has been since approximately 1891 and

cool. Europe is hotter and drier than it has been in about 150 years. If we assume

for the moment that these types of anomalies would persist for 50 years, are these

the types of anomalies that Soon and Baliunas would consider as being indicative

of there being an equivalent to the Medieval Warming in the western United States

and Europe while at the same time there is the equivalent of the Little Ice Age in

eastern North America? How would your type of approach vary in its analysis of

the year 2003 compared to the apparently contradictory results that Soon and

Baliunas would have?

Response. Indeed, as my colleagues and I discussed in our peer-reviewed articles

in ‘‘Eos’’ and more recently ‘‘Geophysical Research Letters’’ [Mann, M.E., Jones, P.D.,

Global Surface Temperatures over the Past two Millennia, Geophysical Research

Letters, 30 (15), 1820, doi: 10.1029/2003GL017814, 2003] the Soon and Baliunas approach is indeed internally contradictory in that it would separately identify anomalies for even a given year, such as 2003, as simultaneously supportive of conditions

they would classify as associated with a ‘‘Little Ice Age’’ and a ‘‘Medieval Warm Period’’ anomaly. As outlined in the question, this year’s pattern of climate anomalies

is a perfect example. Trained climatologists and paleoclimatologists know that one

must independently evaluate precipitation or drought information from temperature

information in reconstructing past climate patterns. For example, colleagues of mine
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and I have developed reconstructions of patterns of drought over the continental

U.S. in past centuries from droughtsensitive tree-ring data [Cook, E.R., D.M. Meko,

D.W. Stahle, and M.K. Cleaveland, Drought Reconstructions for the Continental

United States, Journal of Climate, 12, 1145–1162, 1999; Zhang, Z., Mann, M.E.,

Cook, E.R., Alternative Methods of Proxy-Based Climate Field Reconstruction: Application to the Reconstruction of Summer Drought Over the Conterminous United

States back to 1700 From Drought-Sensitive Tree Ring Data, Holocene, in press,

2003]. The drought reconstructions display a quite different pattern of behavior over

time from reconstructions of Northern Hemisphere mean temperatures, just as patterns of drought over the continental U.S. during the 20th century as recorded from

instrumental data show relatively little in common with instrumental Northern

Hemisphere mean temperature estimates (for example, the most prominent drought

episode was the ‘dust bowl’ of the 1930’s, while the most prominent anomaly in the

Northern Hemisphere temperature record is the late 20th century warming).

Drought and temperature are essentially independent climate variables. The papers

by Soon and Baliunas seem not to recognize this fundamental fact. Finally, there

is an irony in the testimonies of Soon and Legates in that they seem to be criticizing

my colleagues and me for supposedly only focusing on the reconstruction of temperature patterns, when in fact we, and not they, have published work reconstructing

past patterns of drought, precipitation, and atmospheric circulation from proxy climate data. However, we have made careful use of the information contained in

proxy data in independently reconstructing patterns of temperature and patterns of

drought. By contrast, Soon and colleagues hopelessly convolute such information in

their interpretations of past climate trends.

Question 23. Could you provide a more detailed explanation for the apparent

Northern Hemisphere, cooling from the 1940’s to 1970’s? What is the general expectation of what would have happened to the climate in the absence of any human

influences, so just continuing on from the trend for the last 1000 years prior to

human intervention?

Response. In fact, this issue has been studied by quite a number of climate scientists for well over a decade. As I mentioned in my testimony, a statistically significant cooling trend from 1940’s to the 1970’s is not evident for the globe, but only,

for the Northern Hemisphere. Dr Legates testimony on this matter is incorrect in

that regard. The observed record of global-mean temperature changes over the past

100 years indicates a warming to about 1940; little change from 1940 to the mid1970’s, and then further warming, Legates implies in his comments that these

changes are inconsistent with our current understanding of the factors governing

climate change. This is also incorrect. In order to understand these observed

changes it is necessary to consider all likely causal factors, both anthropogenic and

natural, Anthropogenic factors include the warming effects of greenhouse gases and

the cooling effects of sulfate aerosols. Natural factors include changes. in the output

of the Sun and the effects of explosive volcanic eruptions (such as the El Chichon

eruption in 1982 and the Mt. Pinatubo eruption in 1991). and internal variability

associated with natural climate oscillations in the ocean circulation and various

modes of coupled ocean-atmosphere variability (such as El Nin ̃ o). When all of these

factors are considered, models give an expected pattern of 20th century temperature

changes that is in remarkable agreement with the observations—and the models

clearly show the three phases noted above. In particular, the leveling off of the

warming trend over 1940–1975 turns out to be explained largely by the relatively

rapid increase in cooling effects of sulfate aerosols as the world emerged from the

Depression and WWII (and perhaps a small contribution from natural, internal variations in ocean currents). This cooling temporarily offset the warming due to increasing concentrations of greenhouse gases. This was first pointed out in a paper

by Dr. Tom Wigley of the National Center for Atmospheric Research (NCAR) in Nature in 1989 and has been verified by numerous additional studies since. This agreement between models and observations shows quite clearly that human factors have

been the dominant cause of global-scale climate change over the past 50 years, contrary to the repeated assertions by Soon and Legates that they are a manifestation

of natural climate variability. In the absence of anthropogenic factors, model simulations indicate that natural factors alone would have lead to a slight cooling trend

of global temperatures over the 20th century [Crowley, T.J., Causes of Climate

Change Over the Past 1000 Years, Science, 289, 270–277, 2000], in stark contrast

to the dramatic warming that has been observed.

Question 24. It was suggested at the hearing that increased CO2 could enhance

plant life, and that since plants produce oxygen, this could lead to more O2 and less

CO2. Could you please comment on the likelihood of this and how large the percent-
205

age changes could possibly be, recognizing that as the CO2 decreased, this would

presumably mean the plants would do less well and conditions would cool?

Response. Those suggestions (for example, Legates testimony with regard to the

role of the ‘CO2 fertilization’ effect) represent a misunderstanding of the factors governing carbon cycle dynamics and their interaction with climate. In fact, careful

studies that have been performed with coupled climate/terrestrial carbon cycle models that take into account the internal coupled interactions between climate and carbon dioxide, accounting for multiple potential factors such as (a) the potential ‘CO2

fertilization’ effect in which productivity of plants increases in a higher CO2 environment, (b) the impact of climate on productivity in which higher surface temperatures favor enhanced plant growth, and (c) the feedback of CO2 back on surface temperature alluded to in the question [see chapter 3 of the 2001 IPCC working group

1 report]. Such studies show that changes in surface temperature, through their impact on biological productivity, have led to, at most, changes of 5 to 10 ppm in

CO2—levels over the past 1000 years [see Gerber, S, Joos, F., Bruegger, P.P., Stocker, T.F., Mann, M.E.; Sitch, S., Constraining Temperature Variations over the last

Millennium by Comparing Simulated and Observed Atmospheric CO2; Climate Dynamics, 20, 281–299,2003]. Such changes are minimal in comparison with the dramatic increases in CO2 concentrations of more than 80 ppm associated with human

activity, suggesting that the ‘CO2 fertilization’ effect advanced by Legates in his testimony in reality has a minimal role, at best, in the modern changes taking place

in CO2 concentrations and climate.

Question 25. Could you please clarify your remarks regarding the FACE experiments? When you say that increased CO2 leads to more uptake and that they will

rot, do you mean that all plants will grow and eventually die and decay, and that

increased CO2 really only ties up a bit more carbon in the process?

Response. The sequence of questions and time allotted did not allow me to adequately explain this basic, but important point. The point I was making in my testimony is that the supposed increase in the terrestrial carbon reservoir due to enhanced plant growth that is argued to occur in a higher CO2 concentration atmosphere (the so-called ‘CO2 fertilization’ effect) is not a long-term, sustained effect, It

is only a short-term effect that lasts only over the generational timescales of forest

stands. Any depletion of the atmospheric carbon reservoir due to enhanced growth

or productivity of plants argued to arise from higher CO2 concentrations is short

lived, because the plant or tree eventually dies and gives its carbon back to the atmosphere either through microbial activity (rotting) or burning. In other words,

when plants, with any potential additional organic carbon storage that might arise

from enhanced biological activity eventually die, they don’t simply pile up in place

with their carbon reservoir intact (which is what is implicitly assumed by those who

argue that ‘CO2 fertilization’ represents a potential long-term offset to anthropogenic

CO2 increases).

Instead, this carbon is acted upon by biological, chemical, or physical processes

which serve to add the carbon back to the atmosphere. Thus, the so-called ‘‘CO2 fertilization’’ effect, cannot serve as a permanent offset to anthropogenic increases in

the atmospheric carbon budget (i.e., atmospheric CO2 concentrations), as implied by

Legates in his testimony. It may simply act to slow, slightly, the rate of CO2 increase in the atmosphere by slightly increasing the storage rate (but not the residence time) of carbon in the terrestrial biosphere.

Another way to estimate the potential influence is by considering the total

amounts of carbon presently stored in vegetation. Present, about 600 billion tons of

carbon are tied up in the aboveground vegetation. About 2–3 times this much is tied

up in roots and below ground carbon, which is a more difficult carbon pool to augment. By comparison, scenarios for fossil fuel emissions for the 21st century range

from about 600 billion tons (if we can keep total global emissions at current levels,

which implies controls well beyond the Kyoto Protocol calls for) to over 2500 billion

tons if the world increases its reliance on combustion of coal as economic growth

and population increase dramatically. These numbers clearly indicate that sequestering a significant fraction of projected emissions in vegetation is likely to be very

difficult, especially as forests are cleared to make way for agriculture and communities. While there are possibilities of storage in wells and deep in the ocean, stabilizing the atmospheric CO2 concentration would require gathering up the equivalent

of 1 to 2 times the world’s existing above ground vegetation and putting it down

abandoned oil wells or deep in the ocean. While CO2 fertilization will help to increase above ground vegetation a bit, storing more than a few tens of percent of the

existing carbon would be quite surprising, and this is likely to be more like a few

percent of global carbon emissions projected for the 21st century.
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Question 26. Senator Thomas stated that ‘‘[t}he rise in temperature during the

20th century occurred between 1900 and 1940.’’ Could you please provide an indication of how much change occurred during this period based on internationally accepted observations, and compare this to the total change during the 20th century?

Also please comment on whether it is scientifically representative to calculate a

change starting with a cold period due to volcanic eruptions and end it during a period devoid of volcanic eruptions and then compare it to the century long period,

which had major volcanic eruptions in both the first and last decades of the century.

Response. A cursory review of the actual evidence (see e.g. Figure 2.1 of chapter

2 of the 2001 IPCC Scientific Working Group report) indicates the following approximate attributes in the observed record of global-mean temperature changes over the

past 100 years: a warming of approximately 0.3° C to 1940, a statistically insignificant change (given the uncertainties) from 1940 to the mid-1970’s, and then an additional warming of approximately 0.5° C from 1970 to 2000. Senator Thomas’ claim

is thus clearly mistaken. As discussed in my answer to an earlier question, this pattern of behavior is reproduced closely by models driven with estimates of both natural and anthropogenic forcing of the climate during the 20th century. The period

of relative stasis in global mean temperatures from 1940 to 1970, in these model

simulations, appears to result from the cooling impact of anthropogenic aerosols (for

which there was a large increase during that time period) as well as a cooling contribution from explosive volcanic eruptions that occurred during that period, which

tended to offset the warming influence of increased greenhouse gas concentrations

during that time period. However, much of the overall warming of the globe during

the 20th century (which is between 0.6° C and 1.0° C depending on the precise instrumental data set used, and the precise endpoints of the interval examined) is

clearly a result of increased greenhouse gas concentrations, as established in these

simulations.

Question 27. Senator Thomas stated that ‘‘there is no real evidence’’ that the

greenhouse gases are affecting the climate. Could you please summarize the available evidence explaining their probable effect? Please include in your answer a specific example of a proxy indicator such as tree rings and explain the various subtleties in deriving a temperature.

Response. As discussed in my answers to previous questions, the fact that increased greenhouse gas concentrations have a role in 20th century warming is no

longer considered as being in doubt by mainstream researchers. Even noted

contrarians such as Patrick Michaels of the Cato Institute now agree with this conclusion. The only room for legitimate scientific debate concerns the relative role of

greenhouse gas concentrations vs. other factors, and the rate of future warming that

may occur. Evidence establishing the role of anthropogenic greenhouse gas increases

in 20th, century warming includes the agreement with the full spatial (horizontal

and vertical) pattern of warming with predictions from model simulations, and the

fact that only model simulations which include anthropogenic forcing can match the

observations, as discussed earlier. Evidence for an anthropogenic influence on climate also comes from evidence of the anomalous nature of late 20th century warmth

in a very long-term context (i.e., in at least the past millennium, and potentially

the past several millennia or longer). One such source of evidence for this conclusion

comes from proxy climate records (such as tree rings, corals, and ice cores) that can

be used to reconstruct long-term temperature patterns based on a careful consideration of the temperature signal in those data, as discussed in my response to earlier

questions. But other evidence of anomalous late 20th century warmth comes from

indications of unprecedented melting of mountain glaciers the world over (including

meltback in the Alps so dramatic that it recently revealed the now-famous ‘‘Ice

Man’’ who had been trapped in ice for more than 5000 years), and evidence of unusual phenological changes (e.g. the timing of flowering of plants) during the late

20th century.

Question 28. Senator Carper asked the other two witnesses if they thought it ‘‘possible to emit unlimited amounts of CO2 into our atmosphere without having any impact on climate or temperature?’’ What is your expectation of what would occur?

That is, how much change in the CO2 concentration would cause how much of a response?

Response. The response of global mean surface temperature to increased CO2 varies roughly as the logarithm of the CO2 concentration (meaning that increments in

temperature scale with the percentage change in CO2 rather than the change in

amount itself). This is a very well known, and long established result that follows

both from basic theoretical considerations of radiative transfer theory, and is embodied in experiments using global climate models with varying levels of CO2 concentrations. The statistical relationship between estimated concentrations of CO2
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and the admittedly crude estimates of global mean temperatures at various periods

in the geological past or during past glacial intervals, conform relatively well to this

theoretical relationship within estimated uncertainties [see e.g. the textbook,

‘‘Earth’s Climate Past and Future’’, by W.F. Ruddiman (WR Freeman and Co),

2001]. I was extremely surprised when Dr. Soon indicated that he did not know how

to answer Senator Carper’s question, suggesting that he is not familiar with this

fairly basic scientific knowledge.

This result implies, in the absence of any other factors, a linear increase in temperature over time in response to an exponential increase in CO2 (which is not a

bad description of the character of the CO2 trend associated with exponentially increasing anthropogenic activity over the past two centuries). Climate models tell us

that the ‘‘slope’’ of that linear increase is between 1.5° C to 4.5° C for each doubling

of the CO2 concentration. In this context, the testimony Dr. Legates that an arbitrary increase in greenhouse gases would lead only to a ‘‘slight’’ increase in

termperature, seems especially disingenuous. Dr. Legates seems to be suggesting

that the warming would be small despite the magnitude of the CO2 increase. Yet,

both model-based studies and analyses of how climates changes in the past may

have been influenced by changes in atmospheric composition suggest that a 1.5° C

to 4.5° C increase in temperature is likely for each doubling of the CO2 concentration. Thus, a quadrupling of the CO2 concentration, which is plausible if the world

chooses to derive most of its future energy from coal, would be expected to be associated with a roughly 3° C to 9° C increase in global mean temperature. Does Dr,

Legates consider this a ‘‘slightly’’ increased temperature?

Question 29. In his testimony, Dr. Legates indicated that there were historical

cases where the temperature has gone up; but the CO2 has fallen. Do you agree

there were such periods and how would you explain this?

Response. It is certainly the case that this has happened in the past. However,

it is hardly surprising, and certainly not inconsistent with our established understanding of the various factors that influence surface temperatures. The warming

response to increased greenhouse gas concentrations lags the actual increase in

greenhouse gas concentrations in the atmosphere potentially by several decades, due

to the sluggish response of the oceans, which have an enormous thermal capacity

compared to the atmosphere, to increased surface radiative forcing. So warming is

not expected to be contemporaneous with changes in CO2, but instead, to lag it by

several decades. In addition, greenhouse gases are certainly not the only factor affecting the average surface temperature of the Earth. There are other anthropogenic

factors, such as increased sulphate aerosols, which can have a cooling effect on the

climate, and natural factors, such as volcanic activity, modest natural variations in

solar output, and internal dynamics associated with climate events such as El Nin ̃ o,

which also influence the average surface temperature of the globe. At any particular

time, these other factors may outweigh the warming effect due to increased greenhouse gases. For example, the relative lack of warming during the period 1940–1970

appears to be related to a combination of such factors, as discussed in my response

to an earlier question. But while these other factors tend to cancel over time, the

increased greenhouse gases lead to a systematic warming that will not cancel out

over time. It is for precisely this reason that late 20th century warming now appears to have risen above the range of the natural variability of past centuries.

There are two myths commonly perpetuated by climate change contrarians with

regard to the relationship between historical CO2 and temperature variations that

are worth addressing in particular:

(1) Contrarians sometimes argue that the fact that the seasonal cycle in atmospheric CO2, which is opposite of the seasonal cycle in temperature in the Northern

Hemisphere (maximum atmospheric CO2 levels over the course of the year occur

during the Northern Hemisphere winter) implies a negative feedback of temperature on CO2 concentration. Such an argument is based on a most profound misunderstanding of the basic principles governing atmospheric chemistry. Properly

trained atmospheric chemists know that the seasonal cycle in global atmospheric

CO2 concentration is governed by the breathing of the terrestrial biosphere, which

exhibits a hemispheric (and thus seasonal) asymmetry: there is a net uptake of atmospheric CO2 (and thus a drawdown of atmospheric CO2 concentrations) by terrestrial plants during the Northern Hemisphere summer growing season, owing to the

vastly greater proportion of land in the Northern Hemisphere. This simple fact, and

nothing else, dictates the relationship between Northern Hemisphere surface temperatures and CO2 concentrations on seasonal timescales.

(2) Contrarians sometimes argue that the relationship between atmospheric CO2

concentrations and temperature variations associated with glacial/interglacial variations over the past several hundred thousand years, as deduced from ice core
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measurements shows that CO2 is an effect, rather than cause, of climate variability.

This reasoning is unsound for at least two fundamental reasons:

(a) Detailed measurements show that global atmospheric CO2 concentrations lead

estimated polar temperature variations (as deduced from ice core oxygen isotope ratios) during the long phase of increased glaciation, consistent with greenhouse gas

forcing of the atmosphere. There is some evidence that CO2 concentrations, however,

lag estimated polar temperature variations during the rapid phase of deglaciation

(melting of the terrestrial ice sheets at the termination of an ice age). This observation is the basis of the flawed argument summarized below. During this more rapid

‘deglacial’ phase, the climate system if far from being in an equilibrium state, and

the dynamics of the climate system must be considered as representative of the a

coupled interaction between surface temperature, atmospheric CO2, ocean circulation, and glacial mass. It is well known by glaciologists who study this problem that

the relationship between CO2 and temperatures in such a scenario cannot be interpreted in terms of a simple causeeffect relationship.

(b) Even during the rapid deglaciation, the oxygen isotopes from the ice cores only

provide an estimate of surface temperature variations in the proximity of the ice

core (and a very imperfect one, owing to possible seasonal deposition biases and

non-temperature influences on isotope fractionation). They certainly do not provide

an estimate of hemispheric, let alone global, temperature variations. Thus, a comparison of ice core estimates of CO2 and oxygen o18 ratios cannot be used to confidently infer the relationship between CO2 concentrations and global mean temperatures

Question 30. During the hearing, there was some contention over the issue of the

effect of surface cover changes and urban influences on the climate? Could you

please restate your position on the likely sign and magnitude of the influence of

both factors?

Response. Unfortunately misleading comments by Soon and Legates, and the complexity of the issues involved, made it difficult for me to convey, in the brief time

allotted, the established science dealing with the various influences on Earth’s surface radiation balance and changes therein in recent decades. Legates in his testimony confused and misstated the nature of both natural and anthropogenic influences on the Earth’s surface energy budget and on the measurement of surface temperatures from surface-based stations. There are several different issues involved

here, which I will attempt to clarify one at a time below:

(1) The claim made by Legates that the location of thermometer measurements

in urban centers biases estimates of global mean temperature from the available

meteorological observations would be correct were this effect not already carefully

accounted for. In particular, possible urban heat island effects on global temperature

estimates have been studiously accounted for in estimates that have been produced

for more than a decade, See e.g. the 2001 IPCC report. This is unrelated to the issue

of the influence of land-use changes on the surface radiation budget, though Legates

testimony blurs the distinction between the two issues:

(2) The implication by Legates that land-use changes (such as urbanization) are

the dominant influence on changes in the absorptive properties of the Earth as a

whole in recent decades is completely wrong for at least two reasons:

(a) The primary factor impacting changes in the absorption of solar insolation by

the Earth’s surface in modern decades is the decrease in reflective snow and ice

cover due to the warming of the Earth’s surface. This represents a well-known positive feedback (the ‘ice-albedo’ feedback) associated with global warming in which

warming leads to melting of snow and ice, which decreases the reflective properties

of the surface, increasing surface absorption of radiation, and: thus increased the

surface temperatures themselves. This crucial positive feedback, which enhances the

impact of greenhouse gas concentrations on the warming of the surface, is fully accounted for in the climate model simulations that I have referred to above and in

my testimony.

(b) While urbanization, as suggested by Legates, may lead to increased absorption

of solar insolation in some urban areas, this is the more minor of the human land

use changes impacting climate. There are far more extensive regions of the Earth

where other changes in land use, such as conversion of forested land to agricultural

land, have, instead, increased the reflective properties of the Earth’s surface

[Ramankutty, N., and J. A. Foley Estimating historical changes in global land cover:

croplands from 1700 to 992, Global Biogeochemical Cycles, 13, 997–1027, 1999.],

tending to cool the surface, as I explained in my testimony. Scientists who have

studied the influences of these effects have found that the latter cooling effect is the

dominant of these two anthropogenic land-use influences on the Earth’s surface

properties. Thus, climate model simulations investigating the influence of land-use
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changes on hemispheric or global mean temperatures indicate that they have imposed a modest cooling influence [Govindasamy, B., P.B. Duffy, and K. Caldeira,

Land use changes and Northern Hemisphere cooling, Geophysical Research Letters, 28, 291–294, 2001; Bauer, E, M. Claussen, and V. Brovkin, Assessing climate

forcings of the Earth system for the past millennium, Geophys. Res. Lett., 30, doi:

10.1029/2002GL016639, 2003] that partially offsets even greater warming that

would have been realized during the 20th century due to anthropogenic greenhouse

gas influences, Evidence, therefore, does not support the case, as argued by Legates,

that the full range of human land use changes have had a net warming effect on

the climate. They have had a modest cooling influence on the climate.

Question 31. Do you receive any income from any sources which have taken advocacy positions with respect to the Kyoto Protocol, the U.N. Framework Convention

on Climate Change, or legislation before the U.S. Congress that would affect greenhouse gas emissions? If so, please identify those sources and the relevant advocacy

position taken.

Response. I do not, nor have I ever, received any such income.

STATEMENT OF DAVID R. LEGATES, DIRECTOR, CENTER FOR CLIMATIC RESEARCH, UNIVERSITY OF DELAWARE

Distinguished Senators, panelists, and members of the audience: I would like to

thank the Committee for inviting my commentary on this important topic of climate

history and its implications. My name is David R. Legates and I am an Associate

Professor and Director of the Center for Climatic Research at the University of

Delaware in Newark, Delaware. My research interests have focused on

hydroclimatology—the study of water in the atmosphere and on the land—and on

the application of statistical methods in climatological research.

I am familiar with the testimony presented here by Dr. Soon. I agree with his

statements and I will not reiterate his arguments. My contributions to Dr. Soon’s

research stemmed from my grappling with the apparent technology between the

long-standing historical record and the time-series recently presented by Dr. Mann

and his colleagues. It also stems from my own experiences in compiling and merging

global estimates of air temperature and precipitation from a variety of disparate

sources.

My Ph.D. dissertation resulted in the compilation of high-resolution climatologies

of global air temperature and precipitation. From that experience, I have become

acutely aware of the issues associated with merging data from a variety of sources

and containing various biases and uncertainties. By its very nature, climatological

data exhibit a number of spatial and temporal biases that must be taken into account. Instrumental records exist only for the last century or so and thus proxy

records can only be used to glean information about the climate for earlier time periods. But it must be noted that proxy records are not observations and strong caveats must be considered when they are used. It too must be noted that observational

data are not without bias either.

THE HISTORICAL RECORD OF THE LAST MILLENNIUM

Much research has described both the written and oral histories of the climate

as well as the proxy climate records (e.g., ice cores, tree rings, and sedimentations)

that have been derived for the last millennium. It is recognized that such records

are not without their biases—for example, historical accounts often are tainted with

the preconceived beliefs and limited experiences of explorers and historians while

trees and vegetation respond not just to air temperature fluctuations, but to the entire hydrologic cycle of water supply (precipitation) and demand (which is, in part,

driven by air temperature). Nevertheless, such accounts indicate that the climate

of the last millennium has been characterized by considerable variability and that

extended periods of cold and warmth existed. It has been generally agreed that during the early periods of the last millennium, air temperatures were warmer and

that temperatures became cooler toward the middle of the millennium. This gave

rise to the terms the ‘‘Medieval Warm Period’’ and the ‘‘Little Ice Age’’, respectively.

However, as these periods were not always consistently warm or cold nor were the

extremes geographically commensurate in time, such terms must be used with care.

A BIASED RECORD PRESENTED BY THE IPCC AND NATIONAL ASSESSMENT

In a change from its earlier report, however, the Third Assessment Report of the

Intergovernmental Panel on Climate Change (IPCC), and now the U.S. National Assessment of Climate Change, both indicate that hemispheric or global air tempera-
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tures followed a curve developed by Dr. Mann and his colleagues in 1999. This curve

exhibits two notable features. First is a relatively flat and somewhat decreasing

trend in air temperature that extends from 1000AD to about 1900AD and is associated with a relatively high degree of uncertainty. This is followed by an abrupt rise

in air temperature during the 1900’s that culminates in 1998 with the highest temperature on the graph. Virtually no uncertainty is shown for the data of the last

century. The conclusion reached by the IPCC and the National Assessment is that

the 1990’s are the warmest decade with 1998 being the warmest year of the last

millennium.

Despite the large uncertainty, the surprising lack of variability in the record gives

the impression that climate remained relatively unchanged through most of the last

millennium—at least until human influences began to cause an abrupt increase in

temperatures during the last century. Interestingly, Mann et al. replace the proxy

data for the 1900’s by the instrumental record and no uncertainty characterization

is provided. This too yields a false impression that the instrumental record is consistent with the proxy data and that it is ‘error free’. It is neither. The instrumental

record contains numerous uncertainties, resulting from a lack of coverage over the

world’s oceans, an under-representation of mountainous and polar regions as well

as under-developed nations, and the presence of urbanization effects resulting from

the growth of cities. Even if a modest uncertainty of a ±0.1° C were imposed on the

instrumental record, the claim of the 1990’s being the warmest decade would immediately become questionable, as the uncertainty window would overlap with the uncertainty associated with earlier time periods. Note that if the satellite temperature

record—where little warming has been observed over the last 20 years—had been

inserted instead of the instrumental record, it would be impossible to argue that the

1990’s are the warmest decade.

RATIONALE FOR THE SOON et al. investigation

So we were left to question why the Mann et al. curve seems to be at variance

with the previous historical characterization of climatic variability. Investigating

more than several hundred studies that have developed proxy records, we came to

the conclusion that nearly all of these records show considerable fluctuations in air

temperature over the last millennium. Please note that we did not reanalyze the

proxy data—the original analysis from the various researchers was left intact. Most

records show the coldest period is commensurate with at least a portion of what is

termed the ‘‘Little Ice Age’’ and the warmest conditions are concomitant with at

least a portion of what is termed the ‘‘Medieval Warm Period’’.

But our conclusion is entirely consistent with conclusions reached by Drs. Bradley

and Jones that not all locations on the globe experienced cold or warm conditions

simultaneously. Moreover, we chose not to append the instrumental record, but to

compare apples-with-apples and determine if the proxy records themselves indeed

confirm the claim of the 1990’s being the warmest decade of the last millennium.

That claim is not borne out by the individual proxy records.

However, the IPCC report, in the chapter with Dr. Mann as a lead author and

his colleagues as contributing authors, also concludes that research by Drs. Mann,

Jones, and their colleagues ‘‘support the idea that the 15th to 19th centuries were

the coldest of the millennium over the Northern Hemisphere overall.’’ Moreover, the

IPCC report also concludes that the Mann and Jones research ‘‘show[s] temperatures from the 11th to 14th centuries to be about 0.2° C warmer than those from

the 15th to 19th centuries.’’ This again is entirely consistent with our findings.

Where we differ with Dr. Mann and his colleagues is in their construction of the

hemispheric averaged time-series, their assertion that the 1990’s are the warmest

decade of the last millennium, and that human influences appear to be the only significant factor on globally averaged air temperature. Reasons why the Mann et al.

curve fails to retain the fidelity of the individual proxy records are detailed statistical issues into which I will not delve. But our real difference of opinion focuses

solely on the Mann et al. curve and how we have concluded it misrepresents the

individual proxy records. In a very real sense, this is an important issue that scientists must address before the Mann et al. curve is taken as fact.

Our work has been met with much consternation from a variety of sources and

we welcome healthy scientific debate. After all, it is disagreements among scientists

that often lead to new theories and discoveries. However, I am aware that the editors of the two journals that published the Soon et al. articles have been vilified and

the discussion has even gone so far as to suggest that Drs. Soon and Baliunas be

barred from publishing in the journal Climate Research. Such tactics have no place

in scientific debate and they inhibit the free exchange of ideas that is the hallmark

of scientific inquiry.
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1 Christian Seigneur, C., K. Vijayaraghavan, K. Lohman, Pr. Karamchandani, C. Scott, Global

Source Attribution for Mercury Deposition in the United States, submitted to Environ. Sci.

Technol., 2003. 2 Jozef M. Pacyna, Elisabeth G. Pacyna, Frits Steenhuisen and Simon Wilson, Mapping 1995

global anthropogenic emissions of mercury, Atmospheric Environment 37 (S1) (2003) pp. 109–

117. 3 Environment Canada, The Grasshopper Effect and Tracking Hazardous Air Pollutants, The

Science and the Environment Bulletin, May/June 1998.

CLIMATE IS MORE THAN MEAN GLOBAL AIR TEMPERATURE

In closing, let me state that climate is more than simply annually-averaged global

air temperature. Too much focus has been placed on divining air temperature timeseries and such emphasis obscures the true issue in understanding climate change

and variability. If we are truly to understand climate and its impacts and driving

forces, we must push beyond the tendency to distill it to a single annual number.

Proxy records, which provide our only possible link to the past, are incomplete at

best. But when these records are carefully and individually examined, one reaches

the conclusion that climate variability has been a natural occurrence, and especially

so over the last millennium. And given the uncertainties in the proxy and instrumental records, an assertion of any decade as being the warmest in the last millennium is premature.

I’m sorry that a discussion that is best conducted among scientists has made its

way to a U.S. Senate committee. But hopefully a healthy scientific debate will not

be compromised and we can push on toward a better understanding of climate

change.

I again thank you for the privilege of speaking before you today.

PREPARED STATEMENT OF LEONARD LEVIN, PH.D., TECHNICAL LEADER, EPRI,

PALO ALTO, CALIFORNIA

I am Leonard Levin, technical leader at EPRI, which is a non-profit, collaborative

organization conducting energy-related R&D in the public interest. Our members

are public and private organizations in the electricity and energy fields, and we now

serve more than 1000 energy and governmental organizations in more than 40 countries. These remarks constitute a synthesis of current research on environmental

mercury, and are not a representation of official EPRI position.

INTRODUCTION

As a global pollutant, the impact of mercury on the human environment is a critical issue that EPRI and the scientific community have been examining for many

years. As the scientific understanding of where mercury originates nationally and

globally, combined with the new health data, continues to be refined, it can help

inform decisions regarding its management. I would like to address three key questions where new findings have emerged. First, where does mercury found in the

U.S. environment originate? Second, how much has mercury in fish changed in the

last few decades? And third, how do potential mercury management steps change

the amount of mercury depositing to the earth’s surface in the U.S.?

WHERE DOES MERCURY IN THE U.S. ENVIRONMENT ORIGINATE?

Mercury is clearly a global issue. Recent estimates are that, in 1998, some 2340

tons of mercury were emitted globally through industrial activity; of these, more

than half, or 1230 tons, came from Asian countries, primarily China1. These findings are similar to those of other global inventories2. In addition, it is estimated

that another 1300 tons of mercury emanates from land-based natural sources globally, including abandoned mining sites and exposed geological formations. Another

1100 tons or so issues from the world’s oceans, representing both new mercury emitted by undersea vents and volcanoes, and mercury cycled through the ocean from

the atmosphere previously. Recent findings from the large United States-Canadian

METAALICUS field study in Ontario, Canada showed that a fairly small amount

of deposited mercury, no more than 20 percent or so, re-emits to the atmosphere,

even over a 2-year period. The implications of this are profound: mercury may be

less mobile in the environment than we previously thought; once it is removed from

the atmosphere, it may play less of a role in the so-called ‘‘grasshopper effect3 ’’

where persistent global pollutants are believed to successively deposit and re-emit

for many years and over thousands of miles.
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4 Engstrom, D.R., E.B. Swain, Recent Declines in Atmospheric Mercury Deposition in the

Upper Midwest, Environ. Sci. Technol. 1997, 31, 960–967. 5Kraepiel, A.M.L., K. Keller, H.B. Chin, E.G. Malcolm, F.M.M. Morel, Sources and Variations

of Mercury in Tuna, Meeting of American Society for Limnology and Oceanography, Salt Lake

City, Utah: January 2003. 6Slemr, F., E-G. Brunke, R. Ebinghaus, C. Temme, J. Munthe, I. Wangberg, W. Schroeder,

A. Stgeffen, T. Berg, Worldwide trend of atmospheric mercury since 1977, Geophys. Res. Ltrs.,

30 (10), 23–1 to 23–4 7 Richardson G. M., R. Garrett, I. Mitchell, M. Mah-Paulson, T. Hackbarth, Critical Review

On Natural Global And Regional Emissions Of Six Trace Metals To The Atmosphere, International Lead Zinc Research Organization, International Copper Association, Nickel Producers

Environmental Research Association. 8 EPRI Technical Report 1005224, ‘‘A Framework for Assessing the Cost-Effectiveness of Electric Power Sector Mercury Control Policies,’’ EPRI, Palo Alto, CA, May 2003.

Recent studies by EPRI have shown that the mercury depositing into the U.S.

from the atmosphere may originate at very distant points. Model assessments show

that, for 3⁄4 of the area of the continental United States, more than 60 percent of

the mercury received originates outside U.S. borders, from other countries or even

other continents. Only 8 percent of U.S. territory receives 2⁄3 or more of its mercury

from U.S. domestic sources, and less than 1 percent of U.S. territory gets 80 percent

or more of its mercury from sources within the U.S. One implication of this dichotomy between mercury sources and the U.S. areas impacted is that there may be a

‘‘management floor’’ for U.S. mercury, a level below which the amount of mercury

depositing to the surface cannot be reduced.

Additional evidence for the external origins of much of the mercury in the U.S.

environment was gathered over the last 2 years by aircraft experiments carried out

by EPRI, the National Center for Atmospheric Research, and a number of U.S.,

Asian, and Australian investigators. One set of flights measured significant mercury

in winds entering the Pacific Ocean from Shanghai; China; researchers tracked the

Chinese mercury plume over the Pacific for 400 miles toward America. A second set

of flights from Monterey, California, found that same plume from China crossing the

California coast, and a second, higher plume of enriched mercury originating in Central Asia also moving into the U.S. The global nature of mercury in the U.S. has

been clearly demonstrated.

WHAT ARE THE PRIMARY SOURCES OF MERCURY IN FISH AND THE ENVIRONMENT?

For much of the twentieth century, mercury was an essential part of industrial

products, such as batteries and switches, or a key ingredient in such other products

as house paints. These industrial uses of the element declined significantly in the

latter half of the century, and are now less than 10 percent of their use of fifty years

ago.4 Professor Francois Morel of Princeton University and colleagues recently analyzed newly caught Pacific tuna for mercury5, and compared those results to the

mercury content of similar tuna caught in the 1970’s. Despite changes in mercury

emissions to the atmosphere in those thirty years6, and a matching increase in the

mercury depositing; from the atmosphere to rivers and oceans below, Prof Morel

found that mercury levels in tuna have not changed over that time. One conclusion

is that the mercury taken up by such marine fish as tuna is not coming from

sources on land, such as utility power plants, but from natural submarine sources

of mercury, including deep sea volcanoes and ocean floor vents. The implications are

that changes in mercury sources on the continents will not affect the mercury levels

found in open ocean foodfish like tuna.

An estimate in 2001 by scientists of the Geological Survey of Canada and others7

estimated that geological emissions of mercury, as well as emissions from inactive

industrial sites on land, are five to seven times as large as had been estimated earlier. Recent measurements in the stratosphere by EPRI researchers show a rapid

removal of mercury in the upper atmosphere, allowing for additional sources at the

surface while still maintaining the measured rates of deposition and removal needed

for a global balance of sources and sinks. As a result, it is now possible to attribute

a greater fraction of the mercury entering U.S. waters to background natural

sources rather than industrial emissions from the U.S. or elsewhere globally.

HOW COULD POTENTIAL MERCURY REDUCTIONS CHANGE MERCURY DEPOSITION?

EPRI recently completed work to assess the consequences, of further mercury

emissions reductions for mercury in the atmosphere, U.S. waterways, and fish8. The

approach used linked models of atmospheric mercury chemistry and physics with

analyses of Federal data on mercury in fish in the U.S. diet, along with a model

of costs needed to attain a given reduction level.
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Current U.S. utility emissions of mercury are about 46 tons per year. At the same

time, a total of about 179 tons of mercury deposit each year in the U.S., from all

sources global and domestic. One proposed management scenario examined cutting

these utility emissions by 47 percent, to 24 tons per year. The analysis showed that

this cut results in an average 3 percent drop in mercury deposition into the U.S.

Some isolated areas totaling about 1 percent of U.S. land area experience drops of

up to 30 percent in mercury deposited. The cost model used in association with

these calculations showed utility costs to reach these emission control levels would

amount to between $2 billion and $5 billion per year over 12 years. This demonstrated that U.S. mercury patterns are relatively insensitive to the effects of this

single category of sources.

In addition, most of the fish consumed in the U.S. comes from ocean sources,

which would be only marginally affected by a global reduction of 24 tons of mercury

per year due solely to U.S. controls. Wild fresh water fish in the U.S. would be expected to show a greater reduction in mercury content, but are a relatively small

part of the U.S. diet compared to ocean or farmed fish. When these changes were

translated into how much less mercury enters the U.S. diet, we found that 0.064

percent fewer children would be born ‘‘at risk’’ due to their mothers taking in less

mercury from consumed fish. These results were based on the Federal dietary fish

consumption data. So, a drop of nearly half in utility mercury emissions results in

a drop of 3 percent (on average) in mercury depositing to the ground, and a drop

of less than one-tenth of a percent in the number of children ‘‘at risk.’’

DECISIONMAKING UNDER UNCERTAINTY

These recent findings on mercury sources, dynamics, and management are a small

part of the massive international research effort to understand mercury and its impacts on the human environment. EPRI and others, including the U.S. Environmental Protection Agency and the U.S. Department of Energy, are racing to clarify

the complex interactions of mercury with geochemical and biological systems, vital

to understanding mercury’s route to human exposure and potential health effects.

With this improved understanding, informed decisions can be made on the best

ways to manage mercury.

Thank you for the opportunity to deliver these remarks to the Committee.
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STATEMENT OF DEBORAH C. RICE, PH.D., MAINE DEPARTMENT OF

ENVIRONMENTAL PROTECTION, AUGUSTA, MAINE

I would like to thank the Committee for this opportunity to present information

on the adverse health consequences of exposure to methylmercury in the United

States. Until 3 months ago, I was a senior toxicologist in the National Center for

Environmental Assessment in the Office of Research and Development at the Environmental Protection Agency. I am a co-author of the document that reviewed the

scientific evidence on the health effects of methylmercury for EPA, and which included the derivation of the acceptable daily intake level for methylmercury.

I would like to focus my presentation on four points that are key to understanding

the health-related consequences of environmental mercury exposure. One: there is

unequivocal evidence that methylmercury harms the developing human brain. Two:

the Environmental Protection Agency used analyses of three large studies in its derivation of an acceptable daily intake level, including the study in the Seychelles Islands which found no adverse effects. Three: 8 percent of women of child-bearing

age in the United States have levels of methylmercury in their bodies above this

acceptable level. And four: cardiovascular disease in men related to low levels of

methylmercury has been documented, suggesting that a potentially large segment

of the population may be at risk for adverse health effects.

The adverse health consequences to the nervous system of methylmercury exposure in humans were recognized in the 1950’s with the tragic episode of poisoning

in Minamata Bay in Japan, in which it also became clear that the fetus was more

sensitive to the neurotoxic effects of methylmercury than was the adult. A similar

pattern of damage was apparent in subsequent episodes of poisoning in Japan and

Iraq. These observations focused the research community on the question of whether

exposure to concentrations of methylmercury present in the environment might be

producing neurotoxic effects that were not clinically apparent.

As a result, over half a dozen studies have been performed around the world to

explore the effects of environmental methylmercury intake on the development of

the child. Studies in the Philippines (Ramirez et al., 2003), the Canadian Arctic

(McKeown-Eyssen et al., 1983), Ecuador (Counter et al., 1998), Brazil (Grandjean et

al., 1999), French Guiana (Cordier et al., 1999) and Madeira (Murata et al., 1999)

all found adverse effects related to the methylmercury levels in the children’s bodies. These included auditory and visual effects, memory deficits, deficits in

visuospatial ability, and changes in motor function.

In addition to the above studies, there have been three major longitudinal studies

on the effects of exposure to the mother on the neuropsychological function of the

child: in the Faroe Islands in the North Atlantic (Grandjean et al., 1997), in the

Seychelles Islands in the Indian Ocean (Myers et al., 1995), and in New Zealand

(Kjellstrom et al., 1989). Two of these studies identified adverse effects associated

with methylmercury exposure, whereas the Seychelles Islands study did not. Impairment included decreased IQ and deficits in memory, language processing, attention, and fine motor coordination. A National Research Council (NRC) National

Academy of Sciences panel evaluated all three studies in their expert review, concluding that all three studies were well designed and executed (NRC, 2000). They

modeled the relationship between the amount of methylmercury in the mother’s

body and the performance of the child on a number of neuropsychological tests.

From this analysis, they calculated a defined adverse effect level from several types

of behavior in each of the three studies. These adverse effect levels represent a doubling of the number of children that would perform in the abnormally low range of

function. The National Academy of Sciences panel also calculated an overall adverse

effect level of methylmercury in the mother’s body for all three of the studies combined, including the negative Seychelles study. Thus the results of all three studies

were included in a quantitative manner by the NRC.

The Environmental Protection Agency (EPA) used the analyses of the NRC in the

derivation of the reference dose, or RfD, for methylmercury. The RfD is a daily intake level designed to be without deleterious effects over a lifetime. The EPA divided the defined deleterious effect levels calculated by the NRC by a factor of 10

in its RfD derivation. There are two points that need to be made in this regard.

First, the factor of 10 does not represent a safety factor of 10, since the starting

point was a level that doubled the number of low-performing children. Second, the

EPA performed the relevant calculations for a number of measurements for each of

the two studies that found deleterious effects as well as the integrative analysis that

included all three studies modeled by the NRC, including the negative Seychelles

study. The RfD is 0.10 μg/kg/day based on the Faroe Islands study alone or the integrative analysis of all three studies. The RfD would be lower than 0.10 μg/kg/day

if only the New Zealand study had been considered. Only if the negative Seychelles
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Islands study were used exclusively for the derivation of the RfD, while ignoring the

values calculated for the Faroe Islands and New Zealand studies, would the RfD be

higher than the current value of 0.10 μg/kg/day. EPA believes that to do so would

be scientifically unsound, and would provide insufficient protection to the U.S. population.

A substantial portion of U.S. women of reproductive age have methylmercury in

their bodies that is above the level that corresponds to the EPA’s RfD. Data collected over the last 2 years as part of the National Health and Nutritional Examination Survey (NHANES 99+) designed to represent the U.S. population (CDC, Web)

revealed that about 8 percent of women of child-bearing age had blood levels of

methylmercury above the level that the U.S. EPA believes is ‘‘safe’’ (Schober et al.,

2003). This translates into over 300,000 newborns per year potentially at risk for

adverse effects on intelligence and memory, ability to pay attention, ability to use

language, and other skills that are important for success in our highly technological

society.

I would like to further comment here on the use of a factor of 10 by EPA to derive

the allowable daily intake level (RfD) for methylmercury from the defined effect levels calculated by the National Research Council. The RfD corresponds to roughly 1

part per million (ppm) of methylmercury in maternal hair, from the defined effect

level of about 11 ppm calculated by the NRC. But we know that there is no evidence

of a threshold below which there are no adverse effects down to about 2–3 ppm in

hair, the lowest levels in the Faroe Islands study. In fact, there is evidence from

both the Faroe Islands (Budtz-Jorgensen et al., 2000) and New Zealand (Louise

Ryan, Harvard University, personal communication) studies that the change in adverse effect in the child as a function of maternal methylmercury level may be

greater at lower maternal methylmercury levels than at higher ones. Therefore, the

so-called safety factor almost certainly is less than 10, and may be closer to nonexistent. Babies born to women above the RfD may be at actual risk, and not exposed to a level 10 times below a risk level.

There is an additional concern regarding the potential for adverse health consequences as a result of environmental exposure to methylmercury. Several years

ago, a study in Finnish men who ate fish found an association between increased

methylmercury levels in hair and atherosclerosis, heart attacks, and death (Salonen

et al., 1995, 2000). Two new studies in the U.S. and Europe found similar associations between increased methylmercury levels in the bodies of men and cardiovascular disease (Guallar et al., 2002; Yoshizawa et al., 2002). Effects have been

identified at hair mercury levels below 3 ppm. It is not known whether there is a

level of methylmercury exposure that will not cause adverse effects. It is important

to understand that the cardiovascular effects associated with methylmercury may

put an additional, very large proportion of the population at risk for adverse health

consequences as a result of exposure to methylmercury from environmental sources.

In summary, there are four points that I would like the Committee to keep in

mind. First, at least eight studies have found an association between methylmercury

levels and impaired neuropsychological performance in the child. The Seychelles Islands study is anomalous in not finding associations between methylmercury exposure and adverse effects. Second, both the National Research Council and the Environmental Protection Agency included the Seychelles Islands study in their analyses. The only way the acceptable level of methylmercury could be higher would be

to ignore the two major positive studies that were modeled by the NRC, as well as

six smaller studies, and rely solely on the single study showing no negative effects

of methylmercury. Third, there is a substantial percentage of women of reproductive

age in the United States with levels of methylmercury in their bodies above what

EPA considers a safe level. As a result of this, over 300,000 newborns each year

are exposed to methylmercury above levels U.S. EPA believes to be ‘‘safe’’. Fourth,

increased exposure to methylmercury may result in atherosclerosis, heart attack,

and even death from heart attack in men, suggesting that an additional large segment of the population may be at risk as a result of environmental methylmercury

exposure.

Thank you for your time and attention.

RESPONSES BY DEBORAH RICE TO ADDITIONAL QUESTIONS FROM SENATOR JEFFORDS

Question 1. In testimony, you indicated that ‘‘there might be virtually no safety

factor at all’’ with respect to the effect level for mercury exposure. Does that mean

that the reference dose should be lowered further? If so, what would be a safer and

more protective reference dose?
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Response. The current reference dose (RfD) is based on a cord blood mercury concentration associated with a defined risk: a doubling of the number of children performing in the abnormally low range. A total uncertainty factor of 10 was applied

to account for inter-individual variability. There are several decisions made by EPA

that, if different, would have resulted in a lower RfD.

(a) It was assumed that the ratio of cord-to-maternal blood mercury was one. Subsequent analyses of 10 studies revealed that cord blood has more mercury compared

to maternal blood. The average ratio is 1.7:1.0, with the upper 5 percent of women

having a ratio of 3.3:1.0. Based on just the average ratio, if no other decisions were

changed, the RfD would be reduced from 1.0 μg/kg/day to 0.6 μg/kg/day.

(b) As was recommended by the NAS expert committee, EPA assumed that there

was a linear relationship between adverse effects on a number of neuropsychological

endpoints and the level of mercury in cord blood or maternal hair. In fact, the data

from the Faroe Island study best fit a supra-linear model: i.e., the slope was actually

greater at lower body burdens (see figure below). It turns out that this was also true

for the New Zealand study. Recently, a study was published reporting a supra-linear

shape to the relationship between adverse behavioral performance and blood lead

levels in children. So this phenomenon, while somewhat counter-intuitive, may be

real. Using the ‘‘best fit’’ model rather than forcing a linear relationship would result in a lower estimate of the defined adverse starting point (a doubling of the

number of children performing in the abnormally low range), and thereby a lower

RfD.

(c) EPA used a total uncertainty factor (UF) of 10 to derive the RfD, which is designed to provide a margin of safety against adverse effects. EPA typically applies

an UF of 10 for inter-individual variability if the starting point is a no-observableadverse-effect-level (NOAEL). If the starting point is the lowest level that has been

demonstrated to produce an effect, with a NOAEL not identified, the EPA applies

an additional UF, usually 10. In the case of methylmercury, even though the starting point was a level associated with an effect, only a total factor of 10 was applied,

rather than the more typical 100. In addition, the UF of 10 for inter-individual variability is presumed to account for differences in both metabolism and response of

the target organ (sensitivity) between individuals. The variability in metabolism of

methylmercury between women has been demonstrated to be about 3. The variation

in cord-maternal blood levels between women may be also about 3. These would be

multiplied together to equal about 10. That allows no room for any variation in response of the fetal brain to methylmercury, which is undoubtedly not the case.

Therefore a total UF of 10 is almost certainly inadequate to protect the most sensitive portion of the population.

The issue of whether the reference dose should be lowered, and if so, the appropriate value, requires thorough evaluation by a group of expert risk assessors and

other scientists. Any new evaluation of the RfD should also include evaluation of

the levels of methylmercury that produce adverse cardiovascular effects documented

in several studies of adult males. It is currently unknown whether these effects

occur at lower or higher levels than those that produce developmental neurotoxicity.

Question 2. What is a reasonable estimate of the approximate average mercury

concentrations in non-commercial fish in the U.S.?
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Response. EPA keeps an extensive data base of fish tissue contaminant levels

from inland water bodies compiled by individual states (http://www.epa.gov/ost/fish/

mercurydata.html). Data for average levels of mercury for 1987–2000 are in the attached figure. Average tissue levels vary significantly depending on species, such

that deriving an ‘‘average’’ for all species is not particularly informative. Averages

for different species range from 0.1 ppm for herring and whitefish to 0.9 ppm for

bowfin. As can be seen from the figure, the average level for many species is below

the 0.3 ppm level recommended by EPA (Water Quality Criterion for the Protection

of Human Health: Methylmercury, OST, Office of Water, 2001, EPA–823-R–01–001).

Approximately one third of species have average concentrations above this. Even for

species with averages below 0.3 ppm, some samples will exceed this level. For species with averages about 0.5 ppm, more than half the samples will exceed the EPA

recommended limit, whereas half the samples will exceed the 0.5 ppm action limit

set by many European countries and Canada. Ocean fish and sharks can have levels

that are considerably higher. For example, blue marlin average 3.08 ppm, with the

highest level for an individual at 6.8 ppm (Florida Marine Research Institute Technical Reports’ Mercury Levels in Marine and Estuarine Fishes of Florida. 1989–

2001: FMRI Technical Report TR–9, Second Edition, Revised, 2003). Sharks such as

white shark averaged over 5 ppm, with the highest value for a shark at 10 ppm

(ibid.) These are non-commercial sport-caught species.

Question 3. You indicated that the NHANES data does not adequately capture the

individuals or subpopulations that are likely to be the most exposed to non-commercial fish mercury concentrations above the reference dose. Are you aware of any

work underway to collect this kind of data and hopefully protect these people from

overexposure?

Response. There have been a number of relatively small studies focusing on fish

intake by groups that consume large amounts of fish, specifically sports fishers and

subsistence fishing communities. Most of these efforts have been by individual

states or tribes. EPA is developing a data base of these studies, most of which are

unpublished and not in the public domain, a project which I managed before leaving

the agency. The data base currently includes about 70 studies (contact project officer

Cheryl Itkin, EPA/ORD/National Center for Environmental Assessment, Washington, D.C. at itkin.cheryl@epa.gov).

There are also several published studies: Bellanger, T.M., Caesar, E.M.,

Trachtman, L. 2000. Blood mercury levels and fish consumption. J. La. Med. Soc,

152:64–73; Burge, P., Evans, S. 1994. Mercury contamination in Arkansas gamefish.

A public health perspective. J. Ark. Med. Soc. 90:542–544; Hightower, J.M., Moore,

D. 2003. Mercury levels in high-end consumers offish. Environ. Health Perspect.

111:604–608; and Knobeloch, L.M., Ziamik, M., Anderson, H.A., Dodson, V.N. 1995.

Imported seabass as a source of mercury exposure: A Wisconsin case study. Environ.

Health Perspect. 103:604–606.

Protecting individuals who may be at greater risk from over-exposure to

methylmercury presents significant challenges. Forty states have fish advisories for

inland waters, based largely on levels of mercury in fish. Some states have levels

that are specific to particular water bodies, others have statewide advisories for all

water bodies. Advisories typically are set with regard to species of fish, designating

them as e.g. ‘‘no restriction’’, ‘‘eat no more than once a week’’, or ‘‘eat no more than

once a month’’. If a person eats a fish from one restricted category they are meant

not to eat fish from another restricted category in that month. Signs are posted by

some states at specific water bodies, and most if not all states distribute literature

related to fish advisories with fishing licenses. Some tribes have also performed significant outreach related to issues of contaminants in wild foods. Immigrant communities are often the most difficult to inform, as a result of language and cultural

barriers. Minnesota, for example, has made a substantial effort to work with immigrant communities, publishing appropriate information in relevant languages, as

well as performing extensive outreach activities. A few other states have made efforts in this regard as well. Some communities rely on fish as a significant protein

source for both cultural and economic reasons. It is unfortunate indeed that these

communities are risking adverse health outcomes by consuming what should be a

very healthful food.

Question 4. Please describe the purposes and intended uses of the various Federal

agencies’ exposure limits for methyl mercury.

Response. EPA, FDA, and ATSDR have set exposure limits for methylmercury.

The reference dose (RfD) set by EPA is designed to represent an ‘‘estimate of a daily

exposure to the human population (including sensitive subgroups) that is likely to

be without appreciable risk of deleterious [non-cancer] effects during a lifetime’’

(http://www.epa.gov/iris/index.html).
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The minimal risk level (MRL) of ATSDR is ‘‘an estimate of the daily human exposure to a hazardous substance that is likely to be without appreciable risk of adverse noncancer health effects over a specified duration of exposure’’. MRLs may be

derived for acute (1–14 days), intermediate (15–364 days) or chronic durations (over

364 days). ATSDR states that ‘‘[t]hese substance-specific estimates, which are intended to serve as screening levels, are used by ATSDR health assessors and other

responders to identify health effects that may be of concern at hazardous waste

sites. It is important to note that MRLs are not intended to define clean-up or action

levels for ATSDR or other Agencies.’’ [bold original] (http://www.atsdr.cdc.gov/

mrls.html) It is critical to understand that ATSDR is involved in clean-up activities.

The MRLs are designed to identify chemicals that are important for clean-up decisions. They are not intended as health-protective levels for the general population,

or for a lifetime.

The FDA acceptable daily intakes (ADI) is ‘‘the amount of a substance that can

be consumed daily over a long period of time without appreciable risk’’ (http://

www.fda.gov; http://www.cfsan.fda.gov/-acrobat/hgstud16.pdf). For contaminants in

food, FDA uses the ADI to derive an Action Level, ‘‘which defines the maximum allowable concentration of the contaminant in commercial food.’’ In other words, the

Action Level is supposed to be health-based.

The RfD and the ADI are designed to protect the general population from adverse

effects from contaminants in food over a lifetime of exposure, including protection

of sensitive populations. In contrast, the MRL is designed for a different purpose:

identifying contaminants that may be important in making decisions regarding

clean-up of contaminated sites.

The exposure limits from U.S. agencies are as follows:

EPA RfD: 0.1 μg/kg/day

ATSDR MRL: 0.3 μg/kg/day

FDA ADI: 0.4 μg/kg/day

Question 5. What is the preferred measurement methodology for most reliably determining and predicting the effect on children’s developmental health of methyl

mercury exposure?

Response. There has been considerable discussion within the academic and regulatory communities regarding what might be a ‘‘best’’ test or test battery for determining adverse neuropsychological function in children exposed to methylmercury.

There are two basic strategies that have been used to assess methylmercury

neurotoxicity. The first is the use of standard clinical instruments such as measures

of IQ. These have the advantage of being standardized for the population, as well

as assessing a wide range of functional domains. However, because they may be

measuring a number of functions that are not affected in addition to those that are,

the results can be ‘‘diluted’’, and therefore these tests may be less sensitive than

a more focused approach. The second approach is to choose domain-specific tests

based on the known effects of higher levels of the toxic chemical, if such effects are

known. This strategy has the advantage of being potentially more sensitive than

using broad-based clinical instruments. On the other hand, using domainspecific

tasks runs the risk of looking at the wrong functions.

The investigators of the Faroe Islands study used a number of domain-specific

tasks, based on the effects of high-level methylmercury exposure as well as the

pathological changes in specific brain areas produced by methylmercury. The Faroe

Island study found deficits in these’ tasks. The investigators of the Seychelles study

used standard clinical instruments that assessed a little bit of a lot of functions,

which were standardized for a U.S. population rather than the Seychellois population. They found no effect of methylmercury. In contrast, the investigators of the

New Zealand study, also using standard clinical instruments, did identify mercuryrelated deficits.

The consensus of the research community seems to be that a combination of both

approaches should be used, The standard clinical instruments (e.g. full-scale IQ) are

comprised of subscales (e.g. verbal, visuospatial) that can be used to explore more

specific functional domains. Researchers should also use what is known about the

behavioral and neuropathological effects of methylmercury to design domainspecific

tests, with the hope that these will be maximally sensitive. To date, deficits in memory, language processing, visuospatial ability, motor function, and attention have

been identified to be adversely affected by in utero methylmercury exposure. Hearing may also be adversely affected. New studies, or continued testing of current cohorts, should build on this knowledge to hone in even further on specific behavioral

functions.
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Question 6. In 1974, the FDA established a mercury action limit of .5 parts per

million in fish. This was changed in 1979 to 1 part per million. What was the basis

for this change?

Response. FDA set an action level of 0.5 ppm for mercury in fish in 1969,’ in response to the recognition. of the devastating consequences of fetal exposure to

methylmercury in the poisoning episodes in Minamata and Niigata, Japan. This

level was reaffirmed in 1974, citing concerns about damage to the fetus at lower exposures than are harmful to the adult. The level was changed in 1979 as a result

of a lawsuit by the fishing industry that resulted in a court ruling based on socioeconomic impacts presented by the National Marine Fisheries Service (NMFS). They

argued that raising the action level would expand the number of fisheries available

for exploitation and expand the profits of the fishing industry (Fed. Reg. 3990, 3992,

1979). The notice was a withdrawal of the proposed rulemaking and terminated a

rulemaking procedure to codify the (then) existing action level limiting the amount

of unavoidable mercury residues permitted in fish and shellfish of 0.5 ppm. The FR

notice also indicates that ‘‘[t]he Food and Drug Administration will continue to monitor mercury levels in fish so that if there is any change in mercury residue levels

as a result of raising the action level, or if there is any other change in the information regarding mercury in fish, the action level can be revised accordingly.’’ Thus,

the action limit is not health-based, but was established for economic considerations.

Question 7. What, if anything, should consumers of fish in the Great Lakes region

and other areas that are downwind of major mercury emission sources such as coalfired power plants, chlor-alkali manufacturing facilities and; waste incinerators, be

advised to do with respect to limiting their methyl mercury exposure?

Response. Unfortunately, the majority of inland lakes and rivers are contaminated

with mercury. Methylmercury is created from mercury by microorganisms in the

water. Methylmercury is bioconcentrated as it is passed up the food chain, with

older and larger fish at the top of the food chain containing more methylmercury

than smaller fish or fish that are lower on the food chain. Methylmercury exposure

in humans is exclusively from eating contaminated fish. Forty states have explicit

fish advisories as a result of mercury contamination for consumption of fish based

on species, size, and in some states specific water bodies. There were 2,242

advisories in 2000, up 8 percent o from 1999 and up 149 percent from 1993. By far

the greatest number of fish advisories for mercury are around the Great Lakes and

in the Northeastern states. Consumers are advised to carefully follow State fishing

advisories for inland fish. There is an increasing recognition that commercial and/

or ocean fish may represent a significant source of methylmercury exposure. Currently, FDA advises pregnant women, nursing mothers and young children against

eating any shark, swordfish, tilefish, or king mackerel. Recent data indicate that

canned white (albacore) tuna may have substantial levels of methylmercury, and so

should be consumed seldom, especially by children. Other species such as fresh tuna

and halibut may also have significant levels of methylmercury. Intake of purchased

fish that are potentially high in methylmercury should be included by individuals

in determining safe fish intake over a specific time period. In other words, consumers need to have detailed information on fish species from both commercial and

non-commercial sources to keep track of their potential methylmercury intake.

This is an unsatisfactory solution, since fish should be a very healthful food.

Moreover, sport fishing is an important economic resource in many areas, and some

individuals rely on fishing for a substantial portion of their protein, particularly in

certain immigrant communities. The ultimate solution is of course to decrease environmental deposition of mercury.
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STATEMENT OF DR. GARY MYERS, PEDIATRIC NEUROLOGIST

AND PROFESSOR, UNIVERSITY OF ROCHESTER

Thank you for the opportunity to present the views of our research group on the

health effects of methylmercury (MeHg) exposure. My name is Gary Myers. I am

a pediatric neurologist and professor at the University of Rochester in Rochester,

New York and one member of a large team that has been studying the human

health effects of MeHg for nearly 30 years. For nearly 20 years our group has specifically studied the effects of prenatal MeHg exposure from fish consumption on

child development.

MERCURY POISONINGS

In the 1950’s, massive industrial pollution for over two decades in Japan resulted

in high levels of MeHg in ocean fish. Several thousand cases of human poisoning

from consuming the contaminated fish were reported. The precise level of human

exposure causing these health problems was never determined, but was thought to

be high. During that epidemic pregnant women who themselves had minimal or no

clinical symptoms of MeHg poisoning delivered babies with severe brain damage

manifested by cerebral palsy, seizures and severe mental retardation. This suggested that MeHg crosses the placenta from the mother to the fetus and that the

developing nervous system is especially sensitive to its toxic effects.

In 1971–1972 there was an epidemic of MeHg poisoning in Iraq. Unlike the Japanese poisonings, the source of exposure in Iraq was maternal consumption of seed

grain coated with a MeHg fungicide. Our research team studied the children of

about 80 women who were pregnant during this outbreak. We measured mercury

exposure to the fetus using maternal hair, the biomarker that best corresponds to

MeHg brain level, and examined the children. We concluded that there was a possibility that exposure as low as 10 ppm in maternal hair might be associated with

adverse effects on the fetus, although there was considerable uncertainty in this estimate. This value is over 10 times the average in the United States, but individuals

consuming large quantities of fish can achieve this level.

MERCURY FOUND NATURALLY IN THE ENVIRONMENT

Mercury is a natural element in the earth’s crust. In aquatic environments, bacteria can convert inorganic mercury to MeHg. Once MeHg enters the food chain, it

is bioaccummulated and bioconcentrated. All fish contain small amounts, and predatory fish or mammals such as whales have larger amounts. Most commercial oceanic

fish in the United States has < 0.5 ppm MeHg in the muscle, but some freshwater

fish have > 1 ppm. In comparison, contaminated fish in Japan that caused poisoning

had up to 40 ppm.

Everyone who consumes fish is exposed to MeHg, and regular fish consumption

can lead to hair mercury levels as high as 10 ppm or more. The average hair mercury level in the United States is < 1 ppm. If MeHg does affect the developing brain

at such low levels, mothers who consume large amounts of fish would be exposing

their babies to this risk.

The hypothesis of our study in the Seychelles was that prenatal MeHg from fish

consumption might affect child development. Since millions of people around the

world consume fish as their primary source of protein, we decided to investigate the

question directly. We initiated the Seychelles Child Development Study in 1983 and

began enrolling subjects in a pilot study in 1987. We selected the Seychelles as a

sentinel population for the United States for two reasons. First, they consume large

amounts of fish. The average mother in our main cohort ate fish with 12 meals per

week or over 10 times that of U.S. women. Second, the fish consumed in Seychelles

(average mercury content 0.3 ppm) has approximately the same mercury concentration as commercial fish in the United States.

THE SEYCHELLES CHILD DEVELOPMENT STUDY (SCDS)

The SCDS is a collaborative study carried on by researchers at the University of

Rochester Medical Center in Rochester, NY and the Ministries of Health and Education in the Republic of the Seychelles. Funding has come from the National Institute of Environmental Health Sciences, the Food and Drug Administration, and the

governments of Seychelles and Sweden. The Republic of the Seychelles is an island

Nation in the Indian Ocean off the East Coast of Africa.

Our original hypothesis was that prenatal MeHg exposure at levels achieved by

regular maternal consumption of fish would be associated with adverse effects on

child development that could be detected by clinical examination, or by the use of
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developmental tests that have previously been used to study the effects of environmental exposures on child development.

The Seychelles was chosen partly because there is no mercury pollution and many

factors that complicate epidemiological studies of low-level exposure are not present.

Health care is free, universal and readily available. Prenatal care is nearly 100 percent, the birth rate is high, and the general health of mothers and children is good.

Education is free, universal, and starts at age 3.5 years. There is limited emigration

and both the people and the government were cooperative and supportive.

Before starting a carefully controlled main study, we carried out a pilot study. We

expected to find only subtle effects on children at these levels of exposure. Consequently, it was important to minimize any possibility of bias, so a number of decisions were made before the study began. First, no one in Seychelles including researchers visiting the island would know the exposure level of any child or mother,

unless our results indicated that children were at risk from prenatal mercury exposure. Second, children with a known cause of developmental delay (meningitis, very

low birth weight, or brain trauma) would not be studied. Third, the tests administered would include tests previously reported to show associations with MeHg exposure, tests used with other toxic exposures, and other tests that might detect subtle

changes. Fourth, all testing would be performed within specific age windows to minimize the effect of age on test interpretation. Fifth, results would be adjusted for

multiple confounding factors (covariates), including things like socioeconomic status,

maternal intelligence and birth weight, which are known to have independent effects on child development and if not accounted for, could bias the results. Sixth,

the data analysis plan would be determined before the data were collected to minimize the possibility that the data would be repeatedly analyzed until the anticipated

effect was eventually found.

In 1989–90, we enrolled over 700 mothers and children in the SCDS main study.

These children were evaluated on five occasions (6, 19, 29, 66 and 107 months of

age) during the past 9 years. When the children were about 4 years old their homes

were visited and evaluated. The study focused on prenatal exposure. This was measured in the mothers’ hair growing during pregnancy. Postnatal exposure was also

periodically measured in the children’s hair. The exposure of both mothers and children ranged from 1 to 27 ppm, the range of concern. The testing was extensive with

over 57 endpoints being evaluated to date.

Through 107 months (9 years) and over 57 primary endpoints, the study has

found only three statistical associations with prenatal MeHg exposure. One of these

associations was adverse, one was beneficial and one was indeterminate. These results might be expected to occur by chance and do not support the hypothesis that

adverse developmental effects result from prenatal MeHg exposure in the range

commonly achieved by consuming large amounts of fish. The test results do show

associations with factors known to affect child development such as maternal IQ

and home environment so there is evidence that the tests are functioning well.

OUR INTERPRETATION OF THE FINDINGS

We do not believe that there is presently good scientific evidence that moderate

fish consumption is harmful to the fetus. However, fish is an important source of

protein in many countries and large numbers of mothers around the world rely on

fish for proper nutrition. Good maternal nutrition is essential to the baby’s health.

Additionally, there is increasing evidence that the nutrients in fish are important

for brain development and perhaps for cardiac and brain function in older individuals.

The SCDS is ongoing and we will continue to report our results. Presently we are

examining a new cohort to determine specific nutrients that might influence the effects of MeHg.

Appendix—Not read before the committee, but included in the handout.

Because of the public health importance of the question being studied by the

SCDS, the potential exists for differing opinions of scientific findings to become

highly politicized. The SCDS has received only one published criticism (JAMA,

280:737, 1998), but other points have been raised at conferences. These questions

are addressed here individually.

• Why did the SCDS measure mercury in the hair rather than in the cord blood?

Hair mercury was used because it is the standard measure used in nearly all other

studies of this question. Mercury is thought to enter the hair and brain in a similar

fashion. Hair was also chosen because hair has been shown to follow blood concentrations longitudinally, and samples of hair can recapitulate the entire period of

exposure, in this case the period of gestation. As part of our research we have shown

that hair levels reflect levels in the target tissue, brain. Measuring mercury in blood
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requires correction for the red blood cell volume (hematocrit) since the mercury is

primarily in red blood cells and reflects only very recent exposure. It can also vary

if recent meals with high mercury content are consumed.

• Did the SCDS use subjects whose mercury values were too low to detect an association? No, the study’s goal was to see if the children of women who consume

fish regularly were at risk for adverse developmental effects from MeHg. Women in

Seychelles eat fish daily and represent a sentinel population with MeHg levels 10

times higher than U.S. women. Because of higher levels of exposure, their children

should be more likely to show adverse effects if they are present. These children

show no adverse effects through 9 years of age suggesting that eating ocean fish,

when there is no local pollution, is safe. However, we cannot rule out an adverse

effect above 12–15 ppm since we had too few cases to substantiate a statistical association if one really existed.

• Did the SCDS use the best tests available to detect developmental problems?

Yes, the SCDS used many of the same neurodevelopmental and neuropsychological

tests used in other developmental studies. These tests are deemed to be excellent

measures for determining development at the ages studied. The tests examined specific domains of children’s learning and were increasingly sophisticated as the children become older.

• Did the SCDS find expected associations between development and birth

weight, socioeconomic factors, and other covariates? Yes, expected relationships with

many covariates such as maternal IQ, family socioeconomic status and the home environment were found, indicating that our tests were sensitive to developmental differences.

• Did the removal of statistical outliers in the analysis bias the study? No. It is

standard practice among statisticians to remove statistical outliers. Outliers are values that are inconsistent with the statistical model employed to analyze the data.

Every statistical analysis depends on a model, and every statistical model makes assumptions about the statistical (distributional) properties of the data that must be

satisfied if the results of the analysis are to be interpreted correctly. Sound statistical practice requires that the necessary assumptions be checked as part of the statistical analysis. Examination of outliers constitutes one of these checks. Statistical

outliers are defined by the difference between the actual test score for a child and

the value predicted by the statistical model. Small numbers of such outliers occurred in test scores for children with widely varying MeHg exposures. The results

of all analysis were examined both before as well as after the removal of outliers.

For analyses in the main study the removal of statistical outliers did not change

the conclusions.

• What about the Faroe Islands study where prenatal MeHg exposure was reported to adversely affect developmental outcomes? There are substantial differences between the Faroe Islands and Seychelles studies. The exposure in the

Faroe Islands is from consuming whale meat and there is also concomitant exposure

to PCBs and other neurotoxins. There are also differences in the measurement of

exposure and the approach to statistical analysis. The Faroe Islands study reported

associations between cord blood mercury levels and several tests. After statistical

analysis they attributed the associations to prenatal MeHg exposure. Scientific studies are frequently open to different interpretations and some scientists do not agree

with the researchers’ interpretation. We believe the Seychelles study of individuals

consuming fish more closely approximates the U.S. situation.

• Are the children in Seychelles too developmentally robust to find the effects of

MeHg if they are present? No, the children in Seychelles tested similar to U.S. children on nearly all measures apart from motor skills where they were more advanced. There is no reason to think that they are too robust to show the effects of

prenatal MeHg exposure if any are present.

• Are children in Seychelles exposed to PCBs or other food-born toxins that might

have confounded the results? No, sea mammals are not consumed in Seychelles and

measured PCBs in the children’s blood were low.

• Should data from the Seychelles be considered interim? Maybe. Among developmental studies, a 9-year followup is considered very long and should be adequate

to identify associations with most toxic exposures. However, very subtle effects can

be more readily tested in older individuals and there is evidence from experimental

animals that some effects of early mercury exposure may not appear until the animal ages.
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August 18, 2003.

Hon. JAMES M. INHOFE, Chairman,

Committee on Environment and Public Works,

U.S. Senate,

Washington, DC.

DEAR MR. CHAIRMAN: Thank you for offering me the opportunity to respond to

certain comments that were made in the EPW committee hearing on Tuesday, July

29, of this year. I hope I can clear up any confusion that might have been caused

by incomplete, misleading or erroneous testimony that day.

The testimony in question by Dr. Michael Mann stated:

‘‘It’s unfortunate to hear comments about the supposed inconsistencies of the

satellite record voiced here years after that has been pretty much debunked in

the peer-reviewed literature in Nature and Science. Both journals have, in recent years, published . . . articles indicating that in fact, the original statement

that the satellite record showed cooling was flawed because . . . the original author, John Christy, did not take into account a drift in the orbit of that satellite,

which actually leads to a bias in the temperatures . . . Christy and colleagues

have claimed to have gone back and fixed that problem. But just about every

scientist who has looked at it says that this fix isn’t correct and that if you fix

it correctly then the satellite record actually agrees with the surface record, indicating fairly dramatic rates of warming in the past two decades.’’

Virtually all of this testimony is misleading or incorrect. I will touch on the major

problems, point-by-point, and I will try to be brief.

1. Certainly no one has ‘‘debunked’’ the accuracy of the global climate dataset that

we built at The University of Alabama in Huntsville (UAH) using readings taken

by microwave sensors aboard NOAA satellites. This dataset has been thoroughly

and rigorously evaluated, and has been published in a series of peer-reviewed papers beginning in Science (March 1990). The most recent version of the dataset was

published in May 2003 in the Journal of Atmospheric and Oceanic Technology after

undergoing a strenuous peer review process.

2. We, and others, are constantly scrutinizing our techniques to find ways to better analyze the data. In every case except one we discovered needed improvements

ourselves, developed a method for correcting the error, and published both the error

and the correction in peer-reviewed journals. When Wentz, et al. (1998) published

their research on the effects of orbital decay (the one exception) they explained an

effect we immediately recognized, but which was partially counterbalanced by other

factors we ourselves discovered. Since that time we have applied the corrections for

both orbital decay and other factors, and have published the corrected data in peerreviewed journals.

3. The UAH satellite record does not show cooling in the lower troposphere and

hasn’t shown a long-term cooling trend since the period ending in January 1998. I

cannot say where this chronic cooling misconception originated. Our long-term data

show a relatively modest warming in the troposphere at the rate of 0.133° Fahrenheit per decade (or 1.33° Fahrenheit per century) for the period of November 1978

to July 2003.

4. There is no credible version of the satellite dataset that ‘‘actually agrees’’ with

the surface temperature record for the past 25 years, nor one that shows ‘‘fairly dramatic rates of warming.’’ The as-yet-unexplained differences between the surface

and satellite data are at the heart of the controversy over the accuracy of the satellite data.

While much of the surface data remains uncalibrated and uncorroborated, we

have evaluated our UAH satellite data against independent, globally-distributed atmospheric data from the U.S. and the U.K. (Hadley Centre) as shown in the figure

(enclosure 1). We published the results of those comparisons in numerous peer-reviewed studies (enclosure 2). In each case we found excellent consistency between

the satellite data and the atmospheric data. One should note that such independent

corroboration has not been performed on the other satellite temperature datasets alluded to in the quoted testimony.

This consistency between two independent datasets gathered using very different

techniques gives us a high level of confidence that the UAH satellite dataset provides a reliable measure of global atmospheric temperatures over more than 90 percent of the globe. (By comparison, one of the most often quoted surface temperature

datasets achieves partial-global coverage only by claiming that certain isolated thermometer sites provide representative temperatures for an area roughly equaling

two-thirds of the contiguous 48 states, an area that would reach from about Brownsville, Texas, to Grand Forks, North Dakota.)
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5. A final point relates to numerous comments elsewhere in the testimony in

which an appeal to a nebulous ‘‘mainstream climate community’’ was made to support what was stated. First, the notion that ‘‘thousands’’ of climate scientists agreed

on the IPCC 2001 text is an illusion. I was a lead author of IPCC 2001, as was Dr.

Mann. There were 841 lead authors and contributors, the majority of whom were

not climatologists and who provided input in the area in which they have expertise

only to their tiny portion of the 800+ page document. These 841 were not asked to

approve nor where they given the opportunity to give a stamp of approval on what

was finally published.

Although I might be outside the ‘‘mainstream,’’ according to Dr. Mann’s perspective, I have never thought a scientist’s goal was to achieve membership in the

‘‘mainstream.’’ My goal is to produce the most reliable climate datasets for use in

scientific research. Whether they show warming or cooling is less important to me

than their reliability and accuracy. That these datasets have been published in numerous peer-reviewed venues is testimony to accomplishing this goal and, by inference, would place me inside the mainstream climate community. In addition to

being an IPCC lead author, significant achievement awards from NASA and the

American Meteorological Society along with my recent election as a Fellow of the

AMS are evidence of my impact on the community of scientists.

I hope this clears up any confusion you or your committee members might have

had about the UAH global temperature data. If you or any of your committee members have any questions, I will be delighted to answer them to the best of my ability.

Thank you again for offering me this opportunity. I remain,

Sincerely,

JOHN CHRISTY, PH.D.

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