U.S. Climate Change Science Program

Synthesis and Assessment Product 2.2

November 2007

The First State of the

Carbon Cycle Report (SOCCR)

The North American Carbon 

Budget and Implications for 

the Global Carbon Cycle
FEDERAL EXECUTIVE TEAM

Acting Director, Climate Change Science Program: ............................................William J. Brennan

Director, Climate Change Science Program Office:.............................................Peter A. Schultz

Lead Agency Principal Representative to CCSP;

NOAA Acting Deputy Under Secretary of Commerce

for Oceans and Atmosphere: .................................................................................Mary M. Glackin

Chair, Synthesis and Assessment Product Advisory Group, 

Associate Director, EPA National Center for Environmental Assessment: .........Michael W. Slimak

Synthesis and Assessment Product Coordinator, 

Climate Change Science Program Office: ............................................................Fabien J.G. Laurier

Agency Executive Committee (AEC) and Carbon Cycle Interagency Working 

Group (CCIWG) members who facilitated the development of this report:

Lead Agency Coordinator for SAP 2.2; member AEC.........................................Krisa M. Arzayus, NOAA

Chair, AEC; member CCIWG...............................................................................Diane E. Wickland, NASA

Member AEC; Co-Chair, CCIWG ........................................................................Roger C. Dahlman, DOE

Member AEC; Co-Chair, CCIWG ........................................................................Edwin J. Sheffner, NASA

Member AEC and CCIWG....................................................................................James H. Butler, NOAA

Member AEC and CCIWG....................................................................................David Hofmann, NOAA

Member AEC and CCIWG ...................................................................................Patricia Jellison, USGS

Member AEC and CCIWG....................................................................................Fredric Lipschultz, NSF

Member AEC and CCIWG....................................................................................Allen M. Solomon, USDA

Member CCIWG....................................................................................................Paula Bontempi, NASA

Member CCIWG....................................................................................................Nancy Cavallaro, USDA

Member CCIWG....................................................................................................William Emanuel, NASA

Member CCIWG....................................................................................................Roger Hanson, CCSPO

Member CCIWG....................................................................................................Carolyn G. Olson, USDA

Member CCIWG....................................................................................................Kathy Tedesco, NOAA

Member CCIWG....................................................................................................Luis Tupas, USDA

Member CCIWG....................................................................................................Charlie Walthall, USDA

PRODUCTION TEAM

Technical Advisor: David J. Dokken

Graphic Design Lead Sara W. Veasey, NOAA

Graphic Design Co-Lead Deborah B. Riddle, NOAA

Graphic Design Jamie P. Payne, ORNL

Graphic Design Brandon Farrar, STG, Inc.

Graphic Design Glenn M. Hyatt, NOAA

Graphic Design Deborah Misch, STG, Inc.

Copy Editor Lead Anne Markel, STG, Inc.

Copy Editor Walter Koncinski, ORNL 

Copy Editor Deborah Counce, ORNL

Scientific Editor Anne Waple, STG, Inc.

Logistical and Data Management Support Sherry B. Wright, ORNL

Other Technical Support Mieke van der Wansem, Consensus 

Building Institute, Inc.

Ona Ferguson, Consensus Building 

Institute, Inc.

Dan Wei, The Pennsylvania State 

University

This Synthesis and Assessment Product described in the U.S. Climate Change Science Program (CCSP) Strategic Plan, was prepared in accordance 

with Section 515 of the Treasury and General Government Appropriations Act for Fiscal Year 2001 (Public Law 106-554) and the information quality 

act guidelines issued by the Department of Commerce and NOAA pursuant to Section 515 <http://www.cio.noaa.gov/itmanagement/infoq.htm>. The 

CCSP Interagency Committee relies on Department of Commerce and NOAA certifications regarding compliance with Section 515 and Department 

guidelines as the basis for determining that this product conforms with Section 515. For purposes of compliance with Section 515, this CCSP Synthesis 

and Assessment Product is an “interpreted product” as that term is used in NOAA guidelines and is classified as “highly influential.” This document 

does not express any regulatory policies of the United States or any of its agencies, or provide recommendations for regulatory action.
Synthesis and Assessment Product 2.2

Report by the U.S. Climate Change Science Program

and the Subcommittee on Global Change Research

EDITED BY THE SCIENTIFIC COORDINATION TEAM:

Anthony W. King (Lead), Lisa Dilling (Co-Lead),

Gregory P. Zimmerman (Project Coordinator), David M. Fairman, 

Richard A. Houghton, Gregg Marland, Adam Z. Rose, and Thomas J. Wilbanks

The First State of the

Carbon Cycle Report (SOCCR)

The North American Carbon 

Budget and Implications for 

the Global Carbon Cycle
November 2007

Members of Congress:

On behalf of the National Science and Technology Council, the U.S. Climate Change Science 

Program (CCSP) is pleased to transmit to the President and the Congress this report, North 

American Carbon Budget and Implications for the Global Carbon Cycle, as part of a series of 

Synthesis and Assessment Products produced by the CCSP. This series of 21 reports is aimed 

at providing current evaluations of climate change science to inform public debate, policy, and 

operational decisions. These reports are also intended to inform CCSP’s consideration of future 

program priorities. 

CCSP’s guiding vision is to provide the Nation and the global community with the sciencebased knowledge to manage the risks and opportunities of change in the climate and related 

environmental systems. The Synthesis and Assessment Products are important steps toward that 

vision, helping translate CCSP’s extensive observational and research base into informational 

tools directly addressing key questions that are being asked of the research community.

This product will contribute to and enhance the understanding of the North American carbon 

budget and the implications for the global carbon cycle. It was developed with broad scientific 

input and in accordance with the Guidelines for Producing CCSP Synthesis and Assessment 

Products, Section 515 of the Treasury and General Government Appropriations Act for Fiscal 

Year 2001 (Public Law 106-554), and the Information Quality Act guidelines issued by the 

Department of Commerce and the National Oceanic and Atmospheric Administration pursuant to 

Section 515. 

We commend the report’s authors for both the thorough nature of their work and their adherence 

to an inclusive review process.

Samuel W. Bodman

Secretary of Energy

Vice Chair, Committee on Climate 

Change Science and Technology 

Integration

Carlos M. Gutierrez

Secretary of Commerce

Chair, Committee on Climate Change 

Science and Technology Integration

John H. Marburger III

Director, Office of Science and 

Technology Policy

Executive Director, Committee 

on Climate Change Science and 

Technology Integration
 TABLE OF CONTENTS

Abstract .............................................................................................................. VII

Preface/Motivation for Report.........................................................................XIII

Executive Summary...............................................................................................1

PART I: THE CARBON CYCLE IN

NORTH AMERICA

1...........................................................................................................................15

What Is the Carbon Cycle and Why Care?

2...........................................................................................................................21

The Carbon Cycle of North America in a Global Context

3...........................................................................................................................29

The North American Carbon Budget Past and Present

4...........................................................................................................................37

What Are the Options That Could Significantly Affect the North American 

Carbon Cycle?

5...........................................................................................................................49

How Can We Improve the Usefulness of Carbon Science for Decision Making?

PART II: ENERGY, INDUSTRY AND WASTE 

MANAGEMENT ACTIVITIES

Overview............................................................................................................57

An Introduction to CO2 Emissions From Fossil Fuels

6...........................................................................................................................65

Energy Extraction and Conversion

7...........................................................................................................................73

Transportation

8...........................................................................................................................85

Industry and Waste Management

9...........................................................................................................................95

Buildings
II 

TABLE OF CONTENTS

PART III: LAND AND WATER SYSTEMS

Overview..........................................................................................................103

The Carbon Cycle in Land and Water Systems

10.....................................................................................................................107

Agricultural and Grazing Lands

11.....................................................................................................................117

North American Forests

12.....................................................................................................................127

Carbon Cycles in the Permafrost Regions of North America

13.....................................................................................................................139

Wetlands

14.....................................................................................................................149

Human Settlements and the North American Carbon Cycle

15 ...................................................................................................................157

Coastal Oceans

Supporting Materials

Appendix A .................................................................................................167

Historical Overview of the Development of United States, Canadian, and Mexican 

Ecosystem Sources and Sinks for Atmospheric Carbon

(Supplemental to Chapter 3)

Appendix B.................................................................................................169

Eddy-Covariance Measurements Now Confirm Estimates of Carbon Sinks From 

Forest Inventories

(Supplemental to Chapter 3)

Appendix C.................................................................................................171

Industry and Waste Management - Supplemental Material

(Supplemental to Chapter 8)
III

Appendix D.................................................................................................173

Ecosystem Carbon Fluxes

(Supplemental to Chapter 11)

Appendix E..................................................................................................175

Principles of Forest Management for Enhancing Carbon Sequestration

(Supplemental to Chapter 11)

Appendix F..................................................................................................177

Wetlands - Supplemental Materials

(Supplemental to Chapter 13)

Appendix G.................................................................................................193

New pCO2 Database for Coastal Ocean Waters Surrounding North America

(Supplemental to Chapter 15)

Glossary of Terms ..................................................................................195

Acronyms and Abbreviations ........................................................197

References ...................................................................................................199 
IV

AUTHOR TEAM FOR THIS REPORT

Preface Anthony W. King, ORNL; Lisa Dilling, Univ. Colo./NCAR; Gregory P. Zimmerman, 

ORNL; David M. Fairman, Consensus Building Inst., Inc.; Richard A. Houghton, Woods 

Hole Research Center; Gregg Marland, ORNL and Mid Sweden Univ. (Östersund); Adam 

Z. Rose, The Pa. State Univ. and Univ. Southern Calif.; Thomas J. Wilbanks, ORNL 

Executive Summary Anthony W. King, ORNL; Lisa Dilling, Univ. Colo./NCAR; Gregory P. Zimmerman, 

ORNL; David M. Fairman, Consensus Building Inst., Inc.; Richard A. Houghton, 

Woods Hole Research Center; Gregg Marland, ORNL and Mid Sweden Univ. (Östersund); 

Adam Z. Rose, The Pa. State Univ. and Univ. Southern Calif.; Thomas J. Wilbanks, ORNL

Chapter 1 Anthony W. King, ORNL; Lisa Dilling, Univ. Colo./NCAR; Gregory P. Zimmerman, 

ORNL; David M. Fairman, Consensus Building Inst., Inc.; Richard A. Houghton,

Woods Hole Research Center; Gregg Marland, ORNL and Mid Sweden Univ. 

(Östersund); Adam Z. Rose, The Pa. State Univ. and Univ. Southern Calif.; Thomas J. 

Wilbanks, ORNL

Chapter 2 Coordinating Lead Author: Christopher B. Field, Carnegie Inst.

Lead Authors: Jorge Sarmiento, Princeton Univ.; Burke Hales, Oreg. State Univ.

Chapter 3 Coordinating Lead Author: Stephen Pacala, Princeton Univ.

Lead Authors: Richard A. Birdsey, USDA Forest Service; Scott D. Bridgham, Univ. 

Oreg.; Richard T. Conant, Colo. State Univ.; Kenneth Davis, The Pa. State Univ.; Burke 

Hales, Oreg. State Univ.; Richard A. Houghton, Woods Hole Research Center; Jennifer 

C. Jenkins, Univ. Vt.; Mark Johnston, Saskatchewan Research Council; Gregg Marland, 

ORNL and Mid Sweden Univ. (Östersund); Keith Paustian, Colo. State Univ; 

Contributing Authors: John Caspersen, Univ. Toronto; Robert Socolow, Princeton Univ.; 

Richard S. J. Tol, Hamburg Univ.

Chapter 4 Coordinating Lead Author: Erik Haites, Margaree Consultants, Inc.

Lead Authors: Ken Caldeira, Carnegie Inst.; Patricia Romero Lankao, NCAR and UAMXochimilco; Adam Z. Rose, The Pa. State Univ. and Univ. Southern Calif.; Thomas J. 

Wilbanks, ORNL

Contributing Authors: Skip Laitner, U.S. EPA; Richard Ready, The Pa. State Univ.; 

Roger Sedjo, Resources for the Future

Chapter 5 Coordinating Lead Authors: Lisa Dilling, Univ. Colo./NCAR; Ronald Mitchell, Univ. 

Oreg.

Lead Author: David M. Fairman, Consensus Building Inst., Inc.

Contributing Authors: Myanna Lahsen, IGBP (Brazil) and Univ. Colo.; Susanne Moser, 

NCAR; Anthony Patt, Boston Univ./IIASA; Chris Potter, NASA; Charles Rice, Kans. State 

Univ.; Stacy VanDeveer, Univ. N.H.

Part II Overview Coordinating Lead Author: Gregg Marland, ORNL and Mid Sweden Univ. 

(Östersund)

Contributing Authors: Robert J. Andres, Univ. N. Dak.; T.J. Blasing, ORNL; 

Thomas A. Boden, ORNL; Christine T. Broniak, Oreg. State Univ.; Jay S. Gregg, 

Univ. Md.; London M. Losey, Univ. N. Dak.; Karen Treanton, IEA (Paris)

Chapter 6 Lead Author: Thomas J. Wilbanks, ORNL

Contributing Authors: Marilyn Brown, Ga. Inst. Tech.; Ken Caldeira, Carnegie Inst.; 

William Fulkerson, Univ. Tenn.; Erik Haites, Margaree Consultants, Inc; Stephen Pacala, 

Princeton Univ.; David M. Fairman, Consensus Building Inst., Inc.

Chapter 7 Lead Author: David L. Greene, ORNL

Chapter 8 Lead Author: John Nyboer, Simon Fraser Univ.

Contributing Authors: Mark Jaccard, Simon Fraser Univ.; Ernst Worrell, LBNL

IV
Chapter 9 Lead Author: James E. McMahon, LBNL

Contributing Authors: Michael A. McNeil, LBNL; Itha Sánchez Ramos, Instituto de 

Investigaciones Eléctricas (Mexico)

Part III Overview Lead Author: Richard A. Houghton, Woods Hole Research Center

Chapter 10 Lead Authors: Richard T. Conant, Colo. State Univ.; Keith Paustian, Colo. State Univ.

Contributing Authors: Felipe García-Oliva, UNAM; H. Henry Janzen, Agriculture and 

Agri-Food Canada; Victor J. Jaramillo, UNAM; Donald E. Johnson, Colo. State Univ. 

(deceased); Suren N. Kulshreshtha, Univ. Saskatchewan

Chapter 11 Lead Authors: Richard A. Birdsey, USDA Forest Service; Jennifer C. Jenkins, Univ. Vt.; 

Mark Johnston, Saskatchewan Research Council; Elisabeth Huber-Sannwald, Instituto 

Potosino de Investigación Científica y Tecnológica

Contributing Authors: Brian Amiro, Univ. Manitoba; Ben de Jong, ECOSUR; Jorge D. 

Etchevers Barra, Colegio de Postgraduado; Nancy French, Altarum Inst.; Felipe GarcíaOliva, UNAM; Mark Harmon, Oreg. State Univ.; Linda S. Heath, USDA Forest Service; 

Victor J. Jaramillo, UNAM; Kurt Johnsen, USDA Forest Service; Beverly E. Law, Oreg. 

State Univ.; Erika Marín-Spiotta, Univ. Calif. Berkeley; Omar Masera, UNAM; Ronald 

Neilson, USDA Forest Service; Yude Pan, USDA Forest Service; Kurt S. Pregitzer, Mich. 

Tech. Univ.

Chapter 12 Lead Author: Charles Tarnocai, Agriculture and Agri-Food Canada

Contributing Authors: Chien-Lu Ping, Univ. Alaska; John Kimble, USDA NRCS 

(retired)

Chapter 13 Lead Author: Scott D. Bridgham, Univ. Oreg.

Contributing Authors: J. Patrick Megonigal, Smithsonian Environmental Research 

Center; Jason K. Keller, Smithsonian Environmental Research Center; Norman B. Bliss, 

SAIC, USGS Center for Earth Resources Observation and Science; Carl Trettin, USDA 

Forest Service

Chapter 14 Lead Author: Diane E. Pataki, Univ. Calif., Irvine

Contributing Authors: Alan S. Fung, Dalhousie Univ.; David J. Nowak, USDA 

Forest Service; E. Gregory McPherson, USDA Forest Service; Richard V. Pouyat, USDA 

Forest Service; Nancy Golubiewski, Landcare Research; Christopher Kennedy, Univ. 

Toronto; Patricia Romero Lankao, NCAR and UAM-Xochimilco; Ralph Alig, USDA 

Forest Service

Chapter 15 Lead Authors: Francisco P. Chavez, MBARI; Taro Takahashi, Columbia Univ.

Contributing Authors: Wei-Jun Cai, Univ. Ga.; Gernot Friederich, MBARI; Burke Hales, 

Oreg. State Univ.; Rik Wanninkhof, NOAA; Richard A. Feely, NOAA

Appendix A See Chapter 3 Author List

Appendix B See Chapter 3 Author List

Appendix C See Chapter 8 Author List

Appendix D See Chapter 11 Author List

Appendix E See Chapter 11 Author List

Appendix F See Chapter 13 Author List

Appendix G See Chapter 15 Author List

AUTHOR TEAM (CONTINUED)
VI 

VI

The idea for a State of the Carbon Cycle Report (SOCCR) was first 

developed by the Carbon Cycle Interagency Working Group (CCIWG) 

of the U.S. Climate Change Science Program in consultation with its 

Carbon Cycle Science Steering Group. A subcommittee of the CCIWG, 

the Agency Executive Committee (AEC) facilitated the development of 

this report. The AEC included representatives of the lead and supporting 

agencies assigned to Synthesis and Assessment Product 2.2 (SAP 2.2) 

and the assigned Lead Agency Coordinator for SAP 2.2. Funding for the 

preparation and production of SAP 2.2 was provided by NASA, NOAA, DOE, and NSF. The peer review 

was led by NOAA, in collaboration with the Agency Executive Committee. Additionally, USDA and 

USGS contributed by supporting several of their scientists’ participation on the Scientific Coordination 

Team and as chapter authors.

This report has been peer reviewed in draft form by individuals chosen for their diverse perspectives 

and technical expertise. The expert review and selection of reviewers followed the OMB’s Information 

Quality Bulletin for Peer Review. The purpose of this independent review is to provide candid and critical 

comments that will assist the Climate Change Science Program in manuscript, and responses to the peer 

review comments are publicly available at: www.climatescience.gov/Library/sap/sap2-2/default.php.

The AEC and the Scientific Coordination Team thank the following individuals for their peer review of 

this report: Dr. Dominique Blain, Environment Canada; Dr. James G. Bockheim, Professor, University 

of Wisconsin; Dr. Richard A. Bourbonniere, Environment Canada; Dr. Josep Canadell, CSIRO 

Division of Marine and Atmospheric Research; Dr. Robert Dickinson, Georgia Institute of Technology; 

Dr. Phillip M. Dougherty, MeadWestvaco; Dr. George C. Eads, CRI International; William L. Fang, 

Edison Electric Institute; Dr. Christoph Gerbig, Max-Planck-Institute for Biogeochemistry; Dr. Patrick 

Gonzalez, The Nature Conservancy; Dr. Kevin Gurney, Purdue University; Dr. Richard A. Jahnke, 

Skidaway Institute of Oceanography; Dr. Dale W. Johnson, University of Nevada; John Kinsman, 

Edison Electric Institute; Dr. Christopher J. Kucharik, University of Wisconsin-Madison; Dr. Corinne 

Le Quere, University of East Anglia; Dr. Ingeborg Levin, University of Heidelberg; Dr. Alan A. 

Lucier, National Council for Air and Stream Improvement, Inc.; Dr. Loren Lutzenhiser, Portland State 

University; Susann Nordrum, Chevron Energy Technology Company; Naomi Pena, Pew Center on 

Global Climate Change; Dr. Michael Raupach, CSIRO Marine and Atmospheric Research; Dr. Jeffrey 

Richey, University of Washington; Dr. Jonathan Rubin, University of Maine; Dr. David Schimel, 

National Center for Atmospheric Research; Dr. Joshua Schimel, University of California Santa Barbara; 

Dr. Lee Schipper, World Resources Institute; Jeffrey B. Tschirley, Food and Agriculture Organization 

of the United Nations; Dr. John R. Trabalka, SENES Oak Ridge Inc., Center for Risk Analysis; Dr. 

Susan M. Wachter, University of Pennsylvania; and Dr. Douglas W.R. Wallace, Leibniz-Institut für 

Meereswissenschaften.

The Scientific Coordination Team would also like to thank all of the many individuals from the public, 

private, and non-profit sectors who participated in the development of this report by providing feedback, 

attending workshops, being interviewed about the initial outline, and providing comments during the 

public comment period. Their time and thoughtful participation was invaluable to the editors and authors 

in crafting a document that aims to be broadly useful for decision making. The public review comments, 

draft manuscript, and response to public comments are publicly available at: 

www.climatescience.gov/Library/sap/sap2-2/default.php.

ACKNOWLEDGEMENT

VI 
VII ABSTRACT

North America is currently a net source of carbon dioxide to the atmosphere, contributing to the global 

buildup of greenhouse gases in the atmosphere and associated changes in the Earth’s climate. In 2003, North 

America emitted nearly two billion metric tons of carbon to the atmosphere as carbon dioxide. North 

America’s fossil-fuel emissions in 2003 (1856 million metric tons of carbon ± 10% with 95% certainty) were 

27% of global emissions. Approximately 85% of those emissions were from the United States, 9% from 

Canada, and 6% from Mexico. The combustion of fossil fuels for commercial energy (primarily electricity) is 

the single largest contributor, accounting for approximately 42% of North American fossil emissions in 2003. 

Transportation is the second largest, accounting for 31% of total emissions.

There are also globally important carbon sinks in North America. In 2003, growing vegetation in North 

America removed approximately 500 million tons of carbon per year (± 50%) from the atmosphere and 

stored it as plant material and soil organic matter. This land sink is equivalent to approximately 30% of the 

fossil-fuel emissions from North America. The imbalance between the fossil-fuel source and the sink on land 

is a net release to the atmosphere of 1350 million metric tons of carbon per year(± 25%).

Approximately 50% of North America’s terrestrial sink is due to the regrowth of forests in the United States 

on former agricultural land that was last cultivated decades ago, and on timberland recovering from harvest. 

Other sinks are relatively small and not well quantified with uncertainties of 100% or more. The future of the 

North American terrestrial sink is also highly uncertain. The contribution of forest regrowth is expected to 

decline as the maturing forests grow more slowly and take up less carbon dioxide from the atmosphere. But, 

how regrowing forests and other sinks will respond to changes in climate and carbon dioxide concentration 

in the atmosphere is highly uncertain.

The large difference between current sources and sinks and the expectation that the difference could become 

larger if the growth of fossil-fuel emissions continues and land sinks decline suggest that addressing imbalances 

in the North American carbon budget will likely require actions focused on reducing fossil-fuel emissions. 

Options to enhance sinks (growing forests or sequestering carbon in agricultural soils) can contribute, but 

enhancing sinks alone is likely insufficient to deal with either the current or future imbalance. Options to 

reduce emissions include efficiency improvement, fuel switching, and technologies such as carbon capture 

and geological storage. Implementing these options will likely require an array of policy instruments at local, 

regional, national, and international levels, ranging from the encouragement of voluntary actions to economic 

incentives, tradable emissions permits, and regulations. Meeting the demand for information by decision 

makers will likely require new modes of research characterized by close collaboration between scientists 

and carbon management stakeholders.

VII
The U.S. Climate Change Science Program Preface

VIII 

RECOMMENDED CITATIONS

For the Report as a whole:

CCSP, 2007. The First State of the Carbon Cycle Report (SOCCR): The North American Carbon Budget and Implications 

for the Global Carbon Cycle. A Report by the U.S. Climate Change Science Program and the Subcommittee on Global 

Change Research [King, A.W., L. Dilling, G.P. Zimmerman, D.M. Fairman, R.A. Houghton, G. Marland, A.Z. Rose, and 

T.J. Wilbanks (eds.)]. National Oceanic and Atmospheric Administration, National Climatic Data Center, Asheville, NC, 

USA, 242 pp.

For the Preface:

King, A.W., L. Dilling, G.P. Zimmerman, D.M. Fairman, R.A. Houghton, G. Marland, A.Z. Rose, and T.J. Wilbanks, 2007: 

Preface. In: The First State of the Carbon Cycle Report (SOCCR): The North American Carbon Budget and Implications 

for the Global Carbon Cycle. A Report by the U.S. Climate Change Science Program and the Subcommittee on Global 

Change Research [King, A.W., L. Dilling, G.P. Zimmerman, D.M. Fairman, R.A. Houghton, G. Marland, A.Z. Rose, and 

T.J. Wilbanks (eds.)]. National Oceanic and Atmospheric Administration, National Climatic Data Center, Asheville, NC, 

USA, pp. XIII-XVIII.

For the Executive Summary:

King, A.W., L. Dilling, G.P. Zimmerman, D.M. Fairman, R.A. Houghton, G. Marland, A.Z. Rose, and T.J. Wilbanks, 2007: 

Executive Summary. In: The First State of the Carbon Cycle Report (SOCCR): The North American Carbon Budget and 

Implications for the Global Carbon Cycle. A Report by the U.S. Climate Change Science Program and the Subcommittee 

on Global Change Research [King, A.W., L. Dilling, G.P. Zimmerman, D.M. Fairman, R.A. Houghton, G. Marland, 

A.Z. Rose, and T.J. Wilbanks (eds.)]. National Oceanic and Atmospheric Administration, National Climatic Data Center, 

Asheville, NC, USA, pp. 1-14.

For Chapter 1:

King, A.W., L. Dilling, G.P. Zimmerman, D.M. Fairman, R.A. Houghton, G. Marland, A.Z. Rose, and T.J. Wilbanks, 2007: 

What Is the Carbon Cycle and Why Care? In: The First State of the Carbon Cycle Report (SOCCR): The North American 

Carbon Budget and Implications for the Global Carbon Cycle. A Report by the U.S. Climate Change Science Program and 

the Subcommittee on Global Change Research [King, A.W., L. Dilling, G.P. Zimmerman, D.M. Fairman, R.A. Houghton, 

G. Marland, A.Z. Rose, and T.J. Wilbanks (eds.)]. National Oceanic and Atmospheric Administration, National Climatic 

Data Center, Asheville, NC, USA, pp. 15-20.

For Chapter 2:

Field, C.B., J. Sarmiento, and B. Hales, 2007: The Carbon Cycle of North America in a Global Context. In: The First State 

of the Carbon Cycle Report (SOCCR): The North American Carbon Budget and Implications for the Global Carbon Cycle. 

A Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research [King, A.W., 

L. Dilling, G.P. Zimmerman, D.M. Fairman, R.A. Houghton, G. Marland, A.Z. Rose, and T.J. Wilbanks (eds.)]. National 

Oceanic and Atmospheric Administration, National Climatic Data Center, Asheville, NC, USA, pp. 21-28.

For Chapter 3:

Pacala, S., R.A. Birdsey, S.D. Bridgham, R.T. Conant, K. Davis, B. Hales, R.A. Houghton, J.C. Jenkins, M. Johnston, G. 

Marland, and K. Paustian, 2007: The North American Carbon Budget Past and Present. In: The First State of the Carbon 

Cycle Report (SOCCR): The North American Carbon Budget and Implications for the Global Carbon Cycle. A Report by 

the U.S. Climate Change Science Program and the Subcommittee on Global Change Research [King, A.W., L. Dilling, 

G.P. Zimmerman, D.M. Fairman, R.A. Houghton, G. Marland, A.Z. Rose, and T.J. Wilbanks (eds.)]. National Oceanic and 

Atmospheric Administration, National Climatic Data Center, Asheville, NC, USA, pp. 29-36.

For Chapter 4:

Haites, E., K. Caldeira, P. Romero Lankao, A.Z. Rose, T.J. Wilbanks, S. Laitner, R. Ready, and R. Sedjo, 2007: What Are 

the Options That Could Significantly Affect the North American Carbon Cycle? In: The First State of the Carbon Cycle 

Report (SOCCR): The North American Carbon Budget and Implications for the Global Carbon Cycle. A Report by the 

U.S. Climate Change Science Program and the Subcommittee on Global Change Research [King, A.W., L. Dilling, G.P. 
IX

The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

Zimmerman, D.M. Fairman, R.A. Houghton, G. Marland, A.Z. Rose, and T.J. Wilbanks (eds.)]. National Oceanic and 

Atmospheric Administration, National Climatic Data Center, Asheville, NC, USA, pp. 37-48.

For Chapter 5:

Dilling, L., R. Mitchell, D.M. Fairman, M. Lahsen, S. Moser, A. Patt, C. Potter, C. Rice, and S. VanDeveer, 2007: How 

Can We Improve the Usefulness of Carbon Science for Decision Making? In: The First State of the Carbon Cycle Report 

(SOCCR): The North American Carbon Budget and Implications for the Global Carbon Cycle. A Report by the U.S. 

Climate Change Science Program and the Subcommittee on Global Change Research [King, A.W., L. Dilling, G.P. 

Zimmerman, D.M. Fairman, R.A. Houghton, G. Marland, A.Z. Rose, and T.J. Wilbanks (eds.)]. National Oceanic and 

Atmospheric Administration, National Climatic Data Center, Asheville, NC, USA, pp. 49-56.

For Part II Overview:

Marland, G., R.J. Andres, T.J. Blasing, T.A. Boden, C.T. Broniak, J.S. Gregg, L.M. Losey, and K. Treanton, 2007: Energy, 

Industry, and Waste Management Activities: An Introduction to CO2 Emissions From Fossil Fuels. In: The First State of 

the Carbon Cycle Report (SOCCR): The North American Carbon Budget and Implications for the Global Carbon Cycle. 

A Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research [King, A.W., 

L. Dilling, G.P. Zimmerman, D.M. Fairman, R.A. Houghton, G. Marland, A.Z. Rose, and T.J. Wilbanks (eds.)]. National 

Oceanic and Atmospheric Administration, National Climatic Data Center, Asheville, NC, USA, pp. 57-64.

For Chapter 6:

Wilbanks, T.J., M. Brown, K. Caldeira, W. Fulkerson, E. Haites, S. Pacala, and D.M. Fairman, 2007: Energy Extraction 

and Conversion. In: The First State of the Carbon Cycle Report (SOCCR): The North American Carbon Budget and 

Implications for the Global Carbon Cycle. A Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research [King, A.W., L. Dilling, G.P. Zimmerman, D.M. Fairman, R.A. Houghton, G. Marland, 

A.Z. Rose, and T.J. Wilbanks (eds.)]. National Oceanic and Atmospheric Administration, National Climatic Data Center, 

Asheville, NC, USA, pp. 65-72.

For Chapter 7:

Greene, D.L., 2007: Transportation. In: The First State of the Carbon Cycle Report (SOCCR): The North American 

Carbon Budget and Implications for the Global Carbon Cycle. A Report by the U.S. Climate Change Science Program and 

the Subcommittee on Global Change Research [King, A.W., L. Dilling, G.P. Zimmerman, D.M. Fairman, R.A. Houghton, 

G. Marland, A.Z. Rose, and T.J. Wilbanks (eds.)]. National Oceanic and Atmospheric Administration, National Climatic 

Data Center, Asheville, NC, USA, pp. 73-84.

For Chapter 8:

Nyboer, J., M. Jaccard, and E. Worrell, 2007: Industry and Waste Management. In: The First State of the Carbon Cycle 

Report (SOCCR): The North American Carbon Budget and Implications for the Global Carbon Cycle. A Report by the 

U.S. Climate Change Science Program and the Subcommittee on Global Change Research [King, A.W., L. Dilling, G.P. 

Zimmerman, D.M. Fairman, R.A. Houghton, G. Marland, A.Z. Rose, and T.J. Wilbanks (eds.)]. National Oceanic and 

Atmospheric Administration, National Climatic Data Center, Asheville, NC, USA, pp. 85-94.

For Chapter 9:

McMahon, J.E., M.A. McNeil, and I.S. Ramos, 2007: Buildings. In: The First State of the Carbon Cycle Report (SOCCR): 

The North American Carbon Budget and Implications for the Global Carbon Cycle. A Report by the U.S. Climate 

Change Science Program and the Subcommittee on Global Change Research [King, A.W., L. Dilling, G.P. Zimmerman, 

D.M. Fairman, R.A. Houghton, G. Marland, A.Z. Rose, and T.J. Wilbanks (eds.)]. National Oceanic and Atmospheric 

Administration, National Climatic Data Center, Asheville, NC, USA, pp. 95-102.

For Part III Overview:

Houghton, R.A., 2007: The Carbon Cycle in Land and Water Systems. In: The First State of the Carbon Cycle Report 

(SOCCR): The North American Carbon Budget and Implications for the Global Carbon Cycle. A Report by the U.S. 

Climate Change Science Program and the Subcommittee on Global Change Research [King, A.W., L. Dilling, G.P. 

Zimmerman, D.M. Fairman, R.A. Houghton, G. Marland, A.Z. Rose, and T.J. Wilbanks (eds.)]. National Oceanic and 

Atmospheric Administration, National Climatic Data Center, Asheville, NC, USA, pp. 103-106.
The U.S. Climate Change Science Program Preface

For Chapter 10:

Conant, R.T., K. Paustian, F. Garcia-Oliva, H.H. Janzen, V.J. Jaramillo, D.E. Johnson, and S.N. Kulshreshtha, 2007: 

Agricultural and Grazing Lands. In: The First State of the Carbon Cycle Report (SOCCR): The North American Carbon 

Budget and Implications for the Global Carbon Cycle. A Report by the U.S. Climate Change Science Program and the 

Subcommittee on Global Change Research [King, A.W., L. Dilling, G.P. Zimmerman, D.M. Fairman, R.A. Houghton, G. 

Marland, A.Z. Rose, and T.J. Wilbanks (eds.)]. National Oceanic and Atmospheric Administration, National Climatic Data 

Center, Asheville, NC, USA, pp. 107-116.

For Chapter 11:

Birdsey, R.A., J.C. Jenkins, M. Johnston, E. Huber-Sannwald, B. Amero, B. de Jong, J.D.E. Barra, N. French, F. GarciaOliva, M. Harmon, L.S. Heath, V.J. Jaramillo, K. Johnsen, B.E. Law, E. Marín-Spiotta, O. Masera, R. Neilson, Y. Pan, 

and K.S. Pregitzer, 2007: North American Forests. In: The First State of the Carbon Cycle Report (SOCCR): The North 

American Carbon Budget and Implications for the Global Carbon Cycle. A Report by the U.S. Climate Change Science 

Program and the Subcommittee on Global Change Research [King, A.W., L. Dilling, G.P. Zimmerman, D.M. Fairman, 

R.A. Houghton, G. Marland, A.Z. Rose, and T.J. Wilbanks (eds.)]. National Oceanic and Atmospheric Administration, 

National Climatic Data Center, Asheville, NC, USA, pp. 117-126.

For Chapter 12:

Tarnocai, C., C.-L. Ping, and J. Kimble, 2007: Carbon Cycles in the Permafrost Region of North America. In: The First 

State of the Carbon Cycle Report (SOCCR): The North American Carbon Budget and Implications for the Global Carbon 

Cycle. A Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research [King, 

A.W., L. Dilling, G.P. Zimmerman, D.M. Fairman, R.A. Houghton, G. Marland, A.Z. Rose, and T.J. Wilbanks (eds.)]. 

National Oceanic and Atmospheric Administration, National Climatic Data Center, Asheville, NC, USA, pp. 127-138.

For Chapter 13:

Bridgham, S.D., J.P. Megonigal, J.K. Keller, N.B. Bliss, and C. Trettin, 2007: Wetlands. In: The First State of the Carbon 

Cycle Report (SOCCR): The North American Carbon Budget and Implications for the Global Carbon Cycle. A Report by 

the U.S. Climate Change Science Program and the Subcommittee on Global Change Research [King, A.W., L. Dilling, 

G.P. Zimmerman, D.M. Fairman, R.A. Houghton, G. Marland, A.Z. Rose, and T.J. Wilbanks (eds.)]. National Oceanic and 

Atmospheric Administration, National Climatic Data Center, Asheville, NC, USA, pp. 139-148.

For Chapter 14:

Pataki, D.E., A.S. Fung, D.J. Nowak, E.G. McPherson, R.V. Pouyat, N. Golubiewski, C. Kennedy, P. Romero Lankao, 

and R. Alig, 2007: Human Settlements and the North American Carbon Cycle. In: The First State of the Carbon Cycle 

Report (SOCCR): The North American Carbon Budget and Implications for the Global Carbon Cycle. A Report by the 

U.S. Climate Change Science Program and the Subcommittee on Global Change Research [King, A.W., L. Dilling, G.P. 

Zimmerman, D.M. Fairman, R.A. Houghton, G. Marland, A.Z. Rose, and T.J. Wilbanks (eds.)]. National Oceanic and 

Atmospheric Administration, National Climatic Data Center, Asheville, NC, USA, pp. 149-156.

For Chapter 15:

Chavez, F.P., T. Takahashi, W.-J. Cai, G. Friederich, B. Hales, R. Wanninkhof, and R.A. Feely, 2007: Coastal Oceans. In: 

The First State of the Carbon Cycle Report (SOCCR): The North American Carbon Budget and Implications for the Global 

Carbon Cycle. A Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research 

[King, A.W., L. Dilling, G.P. Zimmerman, D.M. Fairman, R.A. Houghton, G. Marland, A.Z. Rose, and T.J. Wilbanks (eds.)]. 

National Oceanic and Atmospheric Administration, National Climatic Data Center, Asheville, NC, USA, pp. 157-166.

For Appendix A

Pacala, S., R.A. Birdsey, S.D. Bridgham, R.T. Conant, K. Davis, B. Hales, R.A. Houghton, J.C. Jenkins, M. Johnston, 

G. Marland, and K. Paustian, 2007: Historical Overview of the Development of United States, Canadian, and Mexican 

Ecosystem Sources and Sinks for Atmosperic Carbon. In: The First State of the Carbon Cycle Report (SOCCR): The North 

American Carbon Budget and Implications for the Global Carbon Cycle. A Report by the U.S. Climate Change Science 

Program and the Subcommittee on Global Change Research [King, A.W., L. Dilling, G.P. Zimmerman, D.M. Fairman, 

R.A. Houghton, G. Marland, A.Z. Rose, and T.J. Wilbanks (eds.)]. National Oceanic and Atmospheric Administration, 

National Climatic Data Center, Asheville, NC, USA, pp. 167-168.
XI

The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

For Appendix B

Pacala, S., R.A. Birdsey, S.D. Bridgham, R.T. Conant, K. Davis, B. Hales, R.A. Houghton, J.C. Jenkins, M. Johnston, G. 

Marland, and K. Paustian, 2007: Eddy-Covariance Measurements Now Confirm Estimates of Carbon Sinks From Forest 

Inventories. In: The First State of the Carbon Cycle Report (SOCCR): The North American Carbon Budget and Implications 

for the Global Carbon Cycle. A Report by the U.S. Climate Change Science Program and the Subcommittee on Global 

Change Research [King, A.W., L. Dilling, G.P. Zimmerman, D.M. Fairman, R.A. Houghton, G. Marland, A.Z. Rose, and 

T.J. Wilbanks (eds.)]. National Oceanic and Atmospheric Administration, National Climatic Data Center, Asheville, NC, 

USA, pp. 169-170.

For Appendix C

Nyboer, J., M. Jaccard, and E. Worrell, 2007: Industry and Waste Management - Supplemental Material. In: The First State 

of the Carbon Cycle Report (SOCCR): The North American Carbon Budget and Implications for the Global Carbon Cycle. 

A Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research [King, A.W., 

L. Dilling, G.P. Zimmerman, D.M. Fairman, R.A. Houghton, G. Marland, A.Z. Rose, and T.J. Wilbanks (eds.)]. National 

Oceanic and Atmospheric Administration, National Climatic Data Center, Asheville, NC, USA, pp. 171-172.

For Appendix D

Birdsey, R.A., J.C. Jenkins, M. Johnston, E. Huber-Sannwald, B. Amero, B. de Jong, J.D.E. Barra, N. French, F. GarciaOliva, M. Harmon, L.S. Heath, V.J. Jaramillo, K. Johnsen, B.E. Law, E. Marín-Spiotta, O. Masera, R. Neilson, Y. Pan, 

and K.S. Pregitzer, 2007: Ecosystem Carbon Fluxes. In: The First State of the Carbon Cycle Report (SOCCR): The North 

American Carbon Budget and Implications for the Global Carbon Cycle. A Report by the U.S. Climate Change Science 

Program and the Subcommittee on Global Change Research [King, A.W., L. Dilling, G.P. Zimmerman, D.M. Fairman, R.A. 

Houghton, G. Marland, A.Z. Rose, and T.J. Wilbanks (eds.)]. National Oceanic and Atmospheric Administration, National 

Climatic Data Center, Asheville, NC, USA, pp. 173-174.

For Appendix E

Birdsey, R.A., J.C. Jenkins, M. Johnston, E. Huber-Sannwald, B. Amero, B. de Jong, J.D.E. Barra, N. French, F. GarciaOliva, M. Harmon, L.S. Heath, V.J. Jaramillo, K. Johnsen, B.E. Law, E. Marín-Spiotta, O. Masera, R. Neilson, Y. Pan, 

and K.S. Pregitzer, 2007: Principles of Forest Management for Enhancing Carbon Sequestration. In: The First State of 

the Carbon Cycle Report (SOCCR): The North American Carbon Budget and Implications for the Global Carbon Cycle. 

A Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research [King, A.W., 

L. Dilling, G.P. Zimmerman, D.M. Fairman, R.A. Houghton, G. Marland, A.Z. Rose, and T.J. Wilbanks (eds.)]. National 

Oceanic and Atmospheric Administration, National Climatic Data Center, Asheville, NC, USA, pp. 175-176.

For Appendix F

Bridgham, S.D., J.P. Megonigal, J.K. Keller, N.B. Bliss, and C. Trettin, 2007: Wetlands - Supplemental Materials. In: The 

First State of the Carbon Cycle Report (SOCCR): The North American Carbon Budget and Implications for the Global 

Carbon Cycle. A Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research 

[King, A.W., L. Dilling, G.P. Zimmerman, D.M. Fairman, R.A. Houghton, G. Marland, A.Z. Rose, and T.J. Wilbanks 

(eds.)]. National Oceanic and Atmospheric Administration, National Climatic Data Center, Asheville, NC, USA, pp. 177-

192.

For Appendix G

Chavez, F.P., T. Takahashi, W.-J. Cai, G. Friederich, B. Hales, R. Wanninkhof, and R.A. Feely, 2007: New pCO2 Database 

for Coastal Ocean Waters Surrounding North America. In: The First State of the Carbon Cycle Report (SOCCR): The 

North American Carbon Budget and Implications for the Global Carbon Cycle. A Report by the U.S. Climate Change 

Science Program and the Subcommittee on Global Change Research [King, A.W., L. Dilling, G.P. Zimmerman, D.M. 

Fairman, R.A. Houghton, G. Marland, A.Z. Rose, and T.J. Wilbanks (eds.)]. National Oceanic and Atmospheric 

Administration, National Climatic Data Center, Asheville, NC, USA, pp. 193-194.
The U.S. Climate Change Science Program

XII 
XIII

The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

PREFACE

A primary objective of the U.S. Climate Change Science Program (CCSP) is to provide the best possible 

scientific information to support public discussion, 

as well as government and private sector decision 

making, on key climate-related issues. To help meet 

this objective, the CCSP has identified an initial set 

of 21 Synthesis and Assessment Products (SAPs) that 

address its highest priority research, observation, and 

decision support needs.

This report—CCSP SAP 2.2—addresses Goal 2 of 

the CCSP Strategic Plan: Improve quantification 

of the forces bringing about changes in the Earth’s 

climate and related systems. The report provides a 

synthesis and integration of the current knowledge 

of the North American carbon budget and its context 

within the global carbon cycle. In a format useful to 

decision makers, it (1) summarizes our knowledge 

of carbon cycle properties and changes relevant 

to the contributions of and impacts1 upon North 

America and the rest of the world, and (2) provides 

scientific information for decision support focused 

on key issues for carbon management and policy. 

Consequently, this report is aimed at both the decision-maker audience and to the expert scientific and 

stakeholder communities.

Background

This report addresses carbon emissions; natural 

reservoirs and sequestration (absorption and storage); rates of transfer; the consequences of changes 

in carbon cycling on land and the ocean; effects of 

1 The term “impacts” as used in this report refers to specific 

effects of changes in the carbon cycle, such as acidification 

of the ocean, the effect of increased CO2 on plant growth 

and survival, and changes in concentrations of carbon in the 

atmosphere. The term is not used as a shortened version of 

“climate impacts,” as was adopted for the Strategic Plan for 

the U.S. Climate Change Science Program.

Report Motivation and Guidance for Using 

This Synthesis/Assessment Report

Authors: Anthony W. King, ORNL; Lisa Dilling, Univ. Colo./NCAR; Gregory P. Zimmerman, 

ORNL; David M. Fairman, Consensus Building Inst., Inc.; Richard A. Houghton, Woods Hole 

Research Center; Gregg Marland, ORNL and Mid Sweden Univ. (Östersund); Adam Z. Rose, 

The Pa. State Univ. and Univ. Southern Calif.; Thomas J. Wilbanks, ORNL 

purposeful carbon management; effects of agriculture, forestry, and natural resource management on 

the carbon cycle; and the socio-economic drivers 

and consequences of changes in the carbon cycle. 

It covers North America’s land, atmosphere, inland 

waters, and coastal oceans, where “North America” 

is defined as Canada, the United States of America 

(excluding Hawaii), and Mexico. Coastal oceans are 

defined as coastal waters less than 100 km from the 

North American coastline, where surface water concentrations of carbon dioxide (CO2) are influenced by 

coastal processes. The report focuses on the current 

carbon budget for North America defined by the 

availability of most recent published data circa 2003. 

Historical trends and processes from 1750 (beginning 

of the Industrial Revolution) and 1850 (expanding 

use of fossil fuels in the Industrial Revolution) to 

present are included where appropriate and needed 

to explain the current carbon budget. Near term (to 

2020), mid term (2020-2040), and long-term (2040-

2100) projections of current trends are considered 

where available (published) and appropriate. The 

report includes an analysis of North America’s carbon budget that documents the state of knowledge 

and quantifies the best estimates (i.e., consensus, 

accepted, official) and uncertainties. This analysis 

provides a baseline against which future results from 

the North American Carbon Program (NACP) www.

nacarbon.org/nacp/about.html can be compared.

The focus of this report follows the Prospectus

developed by the Climate Change Science Program 

and posted on its website at www.climatescience.

gov. The audience for SAP 2.2 includes scientists, 

decision makers in the public sector (e.g., national, 

provincial, state, and local governments), the private 

sector (carbon-related industry, including energy, 

transportation, agriculture, and forestry sectors; and 

XIII
The U.S. Climate Change Science Program Preface

XIV 

climate policy and carbon management interest groups), 

the international community, and the general public. This 

broad audience is indicative of the diversity of stakeholder 

groups interested in knowledge of carbon cycling in North 

America and of how such knowledge might be used to influence or make decisions. Not all the scientific information 

needs of this broad audience can be met in this first SAP, 

but the scientific information provided herein is designed 

to be understandable by all. The primary users of SAP 2.2 

are likely to be officials involved in formulating climate 

policy, individuals responsible for managing carbon in the 

environment, and scientists involved in assessing the state 

of knowledge concerning carbon cycling and the carbon 

budget of North America.

It is envisioned that SAP 2.2 will be used (1) as a state-of-theart assessment of our knowledge of carbon cycle properties 

and changes relevant to the contributions of and carbonspecific impacts upon North America in the context of the 

rest of the world; (2) as a contribution to relevant national 

and international assessments; (3) to provide the scientific 

basis for decision support that will guide management and 

policy decisions that affect carbon fluxes, emissions, and 

sequestration; (4) as a means of informing policymakers and 

the public concerning the general state of our knowledge 

of the global carbon cycle with respect to the contributions 

of and impacts on North America; and (5) to inform future 

efforts for carbon science to support decision making. For 

example, well-quantified regional and continental-scale 

carbon source and sink estimates, error terms, and associated uncertainties will be available for use in climate 

policy formulation and by resource managers interested in 

quantifying carbon emissions reductions or carbon uptake 

and storage. This report is also intended for senior managers 

and members of the general public who desire to improve 

their overall understanding of North America’s role in the 

global carbon budget and to gain perspective on what is and 

is not known.

The questions addressed by this report include: 

• What is the carbon cycle and why should we care? 

• How do North American carbon sources and sinks relate 

to the global carbon cycle? 

• What are the primary carbon sources and sinks in North 

America, and how are they changing and why? 

• What are the direct, non-climatic effects of increasing 

atmospheric CO2 or other changes in the carbon cycle 

on the land and oceans of North America?

• What options can be implemented in North America that 

could significantly affect the North American and global 

carbon cycles (e.g., North American sinks and global 

atmospheric concentrations of CO2)?

• How can we improve the usefulness of carbon science 

for decision making? 

• What additional knowledge is needed for effective carbon 

management? 

Suggestions for Reading, Using, and Navigating 

This Report

The above questions provide the basis for the five chapters in 

Part I of this SAP. These five chapters focus on integrating 

and synthesizing information presented in Parts II and III 

of this report in combination with additional peer-reviewed 

published information from outside the report. The report’s 

assessment of the North American carbon budget is, for 

example, presented in Chapter 3. The Executive Summary

further distills and synthesizes information from across 

the report to address the questions above, which structure 

the report.

Part II of the report focuses on the energy- and industrialrelated components of the North American carbon cycle 

and discusses the carbon emissions and other aspects of 

(a) energy extraction and conversion, (b) the transportation sector, (c) industry and waste management, and (d) the 

buildings sector. Part III provides information about land 

and water systems, including human settlements, and their 

roles in the carbon cycle. Both Parts II and III are introduced 

by an Overview of the subject matter and information in the 

chapters of the respective sections. 

A reader interested in cross-sector integration and synthesis 

at the national and continental scale might, therefore, first 

read the Executive Summary followed by reading Chapters 

1 through 5, referring to Chapters 6-15 and the Overviews of 

Parts II and III for more expanded discussion of information 

specific to individual sectors or ecosystems. Conversely, if 

a reader is more interested in sectoral-specific information, 

he or she might want to peruse the appropriate chapters in 

Part II as a first step. Chapter 1 is intended as a background 

“primer” for those less familiar with concepts of carbon cycling and its importance in considerations of climate change. 

Those familiar with those issues might choose to skip that 

chapter or use it for a quick review.

Definitions and Conventions

Throughout this report, quantification of carbon sources 

and sinks follows the following convention. Sources, such 

as fossil-fuel emissions, that add carbon to the atmosphere 

are indicated with positive numbers. Sinks, such as forest 

growth, that remove carbon from the atmosphere are indicated with negative numbers. The difference between a 

source and a sink is net exchange with the atmosphere, and 

may be either positive or negative (i.e., a source or sink), 

depending on which is larger. Sources and sinks, unless 

otherwise indicated, are given in units of million metric 
XV

The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

tons of carbon per year (Mt C per year). 

Additional definitions of terms, acronyms, and units are provided in the Glossary and Acronyms section of this report. 

The Treatment of Uncertainty in This Report 

Communicating confidence in the findings of scientific 

syntheses and assessments, including the characterization 

of certainty in numbers reported by those assessments, is 

an important part of making scientific assessments useful 

to decision makers and other stakeholders. That communication is sometimes challenged by nuanced differences 

among participants in their understanding of terms such 

as uncertainty or confidence. The challenge is heightened 

when attempting to integrate and synthesize analyses from 

a broad spectrum of sectors and disciplines, each with its 

own methods, conventions, and sometimes language for 

addressing and communicating “uncertainty.”

Variability in physical processes (e.g., carbon sequestration 

by woody vegetation) in time and space, measurement error, and sampling error (itself intimately linked to temporal and spatial variability) all contribute to uncertainty in 

quantifying elements of the North American carbon budget. 

Uncertainties may be compounded by the use of “expansion 

factors”—the analytical models used to interpolate and 

extrapolate local measurements to represent larger areas. 

Methods for translating from the readily measurable to quantities that are difficult or costly to measure (such as the use 

of allometric relationships to estimate whole tree biomass 

from measurements of stem diameter and tree height) can 

also compound uncertainty. The magnitudes of these and 

other sources of uncertainty vary across sectors and elements of the carbon cycle. Consequently, so do the emphases 

and methods for dealing with uncertainty vary across the 

different disciplines that study these elements. There is no 

single applicable quantitative method for integrating these 

variable sources and methods. There exist, of course, statistical techniques, such as the meta-analysis widely used 

in epidemiology and biomedical clinical trials to combine 

results from previous separate but related studies. But only 

rarely, even within a sector or discipline, are the statistical 

pre-requisites of meta-analysis met by the diverse studies 

of carbon cycle elements.

To address this challenge, and to provide for synthesis across 

and comparability among carbon cycle elements, a convention has been adopted for characterizing uncertainty in the 

report’s synthetic findings and results (for example, in the 

synthesized carbon budget for North America of Chapter 3 

and in the Executive Summary). Uncertainty is characterized using asterisks to represent the five categories described 

in the accompanying text box.

Unless otherwise noted, values presented as “y ± x%” should 

be interpreted to mean that the authors are 95% certain the 

actual value is between y – x% and y + x%. Where appropriate, the absolute range is sometimes reported rather 

than the relative range: y ± z, where z = y × x% ÷ 100. The 

system of asterisks is used as shorthand for the categories 

in tables and text.

These are informed categorizations. They reflect expert 

judgment, using all known published descriptions of uncertainty surrounding the “best available” or “most likely” 

estimate. There is always a chance, something like 1 in 20, 

that the actual value lies outside the range surrounding the 

best/most likely estimate, but it is much more likely that the 

actual value is in that range. Some things are known well, 

and one can be highly (95%) certain that the actual value 

is within ± 10% of the estimate. Some things are known 

less well, perhaps there are fewer studies, a broader, more 

variable range of estimates from different studies, or more 

variability or measurement and sampling error reported by 

individual studies, and one can only be highly certain that 

the actual value is captured by the estimate by increasing the 

relative range around the estimate to say ± 25 or 50%. With 

very few and variable or conflicting studies, there is very 

little certainty and confidence in the estimate, the relative 

range of likely values is large and uncertainty is characterized as being greater than 100%.

The 95% boundary was 

chosen to communicate 

the extremely high certainty or confidence that 

the actual value was in 

the reported range, and the 

low likelihood that it was 

outside that range. However, this characterization 

is not a statistical property 

of the estimate, and should 

not be confused with 95% 

confidence intervals based 

CCSP SAP 2.2 Uncertainty Conventions

***** = 95% certain that the actual value is within 10% of the estimate reported, 

  = 95% certain that the estimate is within 25%, 

** * = 95% certain that the estimate is within 50%, 

** = 95% certain that the estimate is within 100%, and

* = uncertainty greater than 100%.

† = The magnitude and/or range of uncertainty for the given numerical 

 value(s) is not provided in the references cited.
The U.S. Climate Change Science Program Preface

XVI 

on parametric statistical estimation of the standard error of 

the mean.

The authors have used this system for categorizing uncertainty only where they have synthesized diverse published 

information and compared across this diversity. When citing 

an existing published estimate, authors were encouraged 

to include the reported characterizations of uncertainty, 

whether quantitative or qualitative. Chapters in this report, 

especially those of Parts II and III, therefore, include several different ways of characterizing uncertainty: simple 

ranges, standard deviations, standard error, and confidence 

intervals. 

In all cases, the form and character of the uncertainty being expressed should be clear either from the context of the 

text or as described in a footnote. There are circumstances 

in which no characterization of the uncertainty of data or 

information is shown, such as when a number is taken from 

a published source that itself did not include a characterization of uncertainty. In these cases, the authors have not 

provided a characterization of uncertainty, and the reader 

should assume that no characterization of uncertainty was 

available to the authors. 

The Treatment of Greenhouse Gases in 

This Report 

Atmospheric CO2 is recognized as the largest single humanmediated agent of climate change. While CO2’s importance 

as a greenhouse gas is a primary motivator for understanding 

how carbon cycles through the atmosphere and other parts 

of the Earth system, this report is about the carbon cycle 

and carbon budgets, and not about greenhouse gases. Accordingly, this report focuses on the North American carbon 

budget as it influences, and is influenced by, concentrations 

of atmospheric CO2. Methane (CH4) is also an important 

greenhouse gas and a potential contributor to human-caused 

climate change. However, CH4 and other non-CO2 carbon 

gases are not typically included in global carbon budgets 

because their sources and sinks are not well understood. For 

this reason, and to manage scope and focus, we too follow 

that convention, and this report is limited primarily to carbon 

and CO2. There is significant discussion of CH4 in individual 

chapters where appropriate (e.g., Chapter 8 on industry and 

waste management, Chapter 10 on agricultural and grazing 

lands, and Chapter 13 on wetlands), but the report’s coverage 

of CH4 is not comprehensive. We made no effort towards an 

across-sector, continental-scale synthesis and assessment of 

CH4 as part of the North American carbon budget. Similarly, 

we provide no comprehensive treatment of black carbon, 

isoprene, or other volatile organic carbon compounds that 

represent a small fraction of global or continental carbon 

budgets. We make no consideration of nitrous oxide (N2O) 

or other non-carbon greenhouse gases. 

The Treatment of Emissions Data Sources in 

This Report 

Part II of this report (Chapters 6 through 9) discusses patterns and trends of CO2 emissions by sector (the transportation sector, for example). Estimating emissions by sector 

brings special challenges in defining sectors and assembling 

the requisite data. Readers will find that there is consistency 

and coherence within each of the report’s chapters but will 

encounter differences across chapters. Different experts 

and different disciplines with different perspectives on the 

carbon cycle use different sector boundaries, different data 

sources, different conversion factors, etc. Different analysts 

and literature sources will use data for different base years 

and may treat, for example, electricity and biomass fuels differently. The national reports of the United States, Canada, 

and Mexico do not cover the same time periods nor do they 

present data in the same way. In this report, the chapter authors have chosen the system boundaries and data they find 

most useful for their sectors and perspectives, even though 

it makes for some differences across chapters. However, the 

database of the International Energy Agency (IEA; www.

iea.org) allows for summary of CO2 emissions for the three 

countries defined as North America in this report according 

to sectors that closely correspond to the sectoral division of 

Chapters 6 through 9 (See the Part II Overview). Similarly, 

the database of the Energy Information Administration 

(EIA; www.eia.doe.gov) provides total global and North 

American fossil-fuel emissions (by country) as a reference 

against which the relative size and contribution of sector 

emissions and carbon sinks can be compared (Chapters 2 

and 3).

The Synthesis and Assessment Product Team 

A full list of the Authorship Team (in addition to the list of 

lead authors provided at the beginning of each chapter) is 

provided on page iv of this report. The Scientific Coordination Team, as described below, reviewed the scientific/tech-
XVII

The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

nical input and managed the formatting, editing, assembly, 

and preparation of the report. 

The SAP 2.2 Prospectus identified a Scientific Coordination Team responsible for organizing and outlining this SAP 

and for its final content and submission. The Coordination 

Team was also responsible for identifying chapter authors, 

coordinating all of the inputs to this report, and leading the 

overall synthesis and integration of this report. The Coordination Team provided oversight and editorial review of 

individual chapters and, with the assistance of the respective 

chapter authors, prepared the Part II Overview and Part III 

Overview, as well as the Abstract and the Executive Summary for this report. The “Key Findings” accompanying 

Chapters 2–15 were developed in collaboration between 

the Scientific Coordination Team and the respective chapter 

authors. These findings were compiled and edited for length, 

style, and consistency by the Coordination Team as part of 

the synthesis and integration across the report. Therefore, 

any error or misrepresentation in the “Key Findings” is the 

responsibility of the Scientific Coordination Team, and not 

of the chapter authors. 

The members of the Coordination Team and their roles 

are:

• Dr. Anthony W. King, Overall Lead

• Dr. Lisa Dilling, Co-Lead, Stakeholder Interaction 

Lead

• Dr. David M. Fairman, Stakeholder Interaction

• Dr. Richard A. Houghton, Scientific Content (Land 

Use)

• Dr. Gregg Marland, Scientific Content (Emissions)

• Dr. Adam Z. Rose, Scientific Content (Economics)

• Dr. Thomas J. Wilbanks, Scientific Content (Human 

Dimensions)

The activities of the Scientific Coordination Team

were managed by:

• Mr. Gregory P. Zimmerman, Project Coordinator

The Scientific Coordination Team recruited one or more scientific experts to be responsible for writing each individual 

chapter of SAP 2.2. This person (or persons) was designated 

as either the Coordinating Lead author or the Lead Chapter 

author. For the individual chapters in Part I, the respective 

Coordinating Lead author had responsibility for orchestrating the preparation of the chapter. For each chapter in Parts 

II and III, the respective Lead Author had that responsibility. 

These Coordinating Lead authors and Lead Chapter authors 

are recognized leaders in their fields, drawn from the wide 

and diverse scientific community of North America and the 

world, as well as other qualified stakeholder groups. Their 

qualifications include the quality and relevance of current 

publications in the peer-reviewed literature pertaining to 

their chapter topics, past or present positions of leadership 

in the topic fields, and other documented experience and 

knowledge of high relevance. Each Coordinating Lead 

author and Lead Chapter author was responsible for the 

review and synthesis of current knowledge and production 

of text for his/her respective chapter. The Coordinating 

Lead authors and Lead Chapter Authors were responsible 

for recruiting well-qualified contributing authors in their 

areas of expertise and responsibility. The Coordinating Lead 

authors and Lead Chapter Authors, along with the Scientific 

Coordination Team, were also responsible for ensuring that 

scientific expert, stakeholder, and public review comments 

on their chapters are reflected in this report.

Stakeholder Involvement Process

Research suggests that in order for an assessment to be useful for decision making, it must be not only scientifically 

accurate and rigorous, but also relevant to the near-term 

concerns of decision makers and their constituencies (“stakeholders”). It must also be created in a way that stakeholders 

perceive as fair and unbiased; this last point is especially 

important when the assessment deals with a controversial 

public issue.

To make the SAP 2.2 as useful for decision making as 

possible, we dedicated significant effort and resources to 

developing a stakeholder engagement process. Because the 

North American carbon cycle involves a vast array of interactions between human activities and the environment, and 

because changes in the carbon cycle may have far-reaching 

economic, social, and political implications, the stakeholders for this report arguably include the entire population of 

the continent.

To focus the stakeholder engagement process, the Coordination Team sought to identify and involve representatives 

of government (national and subnational) with current or 

potential responsibility for carbon management, businesses 

with a substantial interest in carbon management, and environmental groups active in carbon cycle issues, along with 

academic and consulting experts in carbon cycle issues. We 

were partially successful in our efforts to involve a broad 

and representative group of stakeholders. Our extensive 

outreach efforts generated public comments from only a limited number of individuals, and attendance at our individual 

workshops was not equally balanced across all stakeholder 

groups. We did, however, succeed in generating participation 

and public comment from all the major stakeholder groups. 

What the process lacked in numbers, it arguably made up for 

in the quality of interaction and feedback received.

The stakeholder engagement process involved a combination of interviews, workshops, and online communication 

tools such as a website and email. Stakeholders’ interests 
The U.S. Climate Change Science Program Preface

XVIII 

were considered and represented at all stages. However, 

the responsibility for content of the report rested with the 

authors themselves. 

We began involving stakeholders early in the process, at 

a point where they might have significant opportunity to 

provide input into the shape and overall structure of the 

report. Our first activity was to conduct a “rapid stakeholder 

assessment” which consisted of approximately 30 phone 

interviews with stakeholders from government, academia, 

business, and environmental groups. During this assessment, we asked stakeholders about their impressions of 

our tentative outline for the report, and for suggestions on 

chapter authors. 

We then conducted the first of our stakeholder workshops, 

also focusing on the draft outline and asking how we might 

make the report as useful as possible to a wide range of 

stakeholders. At this workshop, we significantly changed 

the structure of the report based on valuable input from 

the group assembled. After the workshop, we then posted 

our draft outline online, and provided an open comment 

period for anyone to send in comments, which were also 

considered in constructing the next draft and formal SAP 

2.2 Prospectus outline. We also created an online email 

listserv early in the process, which now has over 350 members subscribed. Our second workshop occurred mid-way 

through the process, when the authors had created an early 

draft of their chapters. At the workshop, stakeholders and 

authors met together, so that input and feedback could be 

direct and interactive. Through the Climate Change Program Office, we then received feedback on a peer-reviewed 

draft through a formal public comment process. Finally, we 

conducted a third stakeholder workshop during the public 

comment process, in order to have one more opportunity 

for direct dialogue on the document. We also maintained a 

public website from the start of the process with our names 

and contact information, and communicated via email and 

phone with stakeholders. The website can be accessed at 

http://cdiac.ornl.gov/SOCCR.
EXECUTIVE SUMMARY

The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

Lead Author: Scientific Coordination Team

Scientific Coordination Team Members: Anthony W. King 

(Lead), ORNL; Lisa Dilling (Co-Lead), Univ. Colo./NCAR; Gregory 

P. Zimmerman (Project Coordinator), ORNL; David M. Fairman, 

Consensus Building Inst., Inc.; Richard A. Houghton, Woods Hole 

Research Center; Gregg Marland, ORNL; Adam Z. Rose, The Pa. State 

Univ. and Univ. Southern Calif.; Thomas J. Wilbanks, ORNL

Abstract 

North America is currently a net source of CO2 to the atmosphere, 

contributing to the global buildup of greenhouse gases in the atmosphere and associated changes in the Earth’s climate. In 2003, North 

America emitted nearly two billion metric tons of carbon to the 

atmosphere as CO2. North America’s fossil-fuel emissions in 2003 

(1856 million metric tons of carbon ±10% with 95% certainty) were 

27% of global emissions. Approximately 85% of those emissions were 

from the United States, 9% from Canada, and 6% from Mexico. The 

combustion of fossil fuels for commercial energy (primarily electricity) is the single largest contributor, accounting for 

approximately 42% of North American fossil emissions in 2003. Transportation is the second largest, accounting for 

31% of total emissions.

There are also globally important carbon sinks in North America. In 2003, growing vegetation in North America removed 

approximately 500 million tons of carbon per year (±50%) from the atmosphere and stored it as plant material and soil 

organic matter. This land sink is equivalent to approximately 30% of the fossil-fuel emissions from North America. The 

imbalance between the fossil-fuel source and the sink on land is a net release to the atmosphere of 1350 million metric 

tons of carbon per year (± 25%).

Approximately 50% of North America’s terrestrial sink is due to the regrowth of forests in the United States on former 

agricultural land that was last cultivated decades ago, and on timberland recovering from harvest. Other sinks are relatively small and not well quantified with uncertainties of 100% or more. The future of the North American terrestrial 

sink is also highly uncertain. The contribution of forest regrowth is expected to decline as the maturing forests grow 

more slowly and take up less CO2 from the atmosphere. But this expectation is surrounded by uncertainty because 

how regrowing forests and other sinks will respond to changes in climate and CO2 concentration in the atmosphere is 

highly uncertain.

The large difference between current sources and sinks and the expectation that the difference could become larger 

if the growth of fossil-fuel emissions continues and land sinks decline suggest that addressing imbalances in the North 

American carbon budget will likely require actions focused 

on reducing fossil-fuel emissions. Options to enhance sinks 

(growing forests or sequestering carbon in agricultural soils) 

can contribute, but enhancing sinks alone is likely insufficient 

to deal with either the current or future imbalance. Options to reduce emissions include efficiency improvement, 

fuel switching, and technologies such as carbon capture and 

geological storage. Implementing these options will likely 

require an array of policy instruments at local, regional, national, and international levels, ranging from the encouragement of voluntary actions to economic incentives, tradable 

emissions permits, and regulations. Meeting the demand 

for information by decision makers will likely require new 

modes of research characterized by close collaboration 

between scientists and carbon management stakeholders.
The U.S. Climate Change Science Program Executive Summary

ES.1 Synthesis and assessment

of the North American carbon

budget

Understanding the North American carbon budget, both 

sources and sinks, is critical to the United States Climate 

Change Science Program goal of providing the best possible 

scientific information to support public discussion, as well 

as government and private sector decision making, on key 

climate-related issues. In response, this report provides 

a synthesis, integration, and assessment of the current 

knowledge of the North American carbon budget and its 

context within the global carbon cycle. The report focuses on 

the carbon cycle as it influences the concentration of carbon 

dioxide (CO2) in the 

atmosphere. Methane 

(CH4), nitrous oxide, 

and other greenhouse 

gases are also relevant 

to climate issues, but 

their consideration is 

beyond the scope and 

mandate of this report.

The report is organized as a response to questions relevant 

to carbon management and to a broad range of stakeholders charged with understanding and managing energy and 

land use. The questions were identified through early and 

continuing dialogue with these stakeholders, including scientists; decision makers in the public and private sectors, 

including national and sub-national government; carbon-related industries, such as energy, transportation, agriculture, 

and forestry; and climate policy and carbon management 

interest groups.

The questions and the answers provided by this report are 

summarized below. The reader is referred to the indicated 

chapters for further, more detailed, discussion. Unless otherwise referenced, all values, statements of findings and 

conclusions are taken from the 

chapters of this report where 

the attribution and citation of 

the primary sources can be 

found.

ES.2 What is the carbon cycle and

why should we care?

The carbon cycle, described in Chapters 1 and 2, is the 

combination of many different physical, chemical, and 

biological processes that transfer carbon between the major 

storage pools (known as reservoirs): the atmosphere, plants, 

soils, freshwater systems, oceans, and geological sediments. 

Hundreds of millions of years ago, and over millions of 

years, this carbon cycle was responsible for the formation of 

coal, petroleum, and natural gas, the fossil fuels that are the 

primary sources of energy for our modern societies.

Humans have altered the Earth’s carbon budget. Today, the 

cycling of carbon among atmosphere, land, and freshwater 

and marine environments is in rapid transition and out of 

balance. Over tens of years, the combustion of fossil fuels 

is releasing into the atmosphere quantities of carbon that 

were accumulated in the Earth system over millions of 

years. Furthermore, tropical forests that once held large 

quantities of carbon are being converted to agricultural 

lands, releasing additional carbon to the atmosphere as a 

result. Both the fossil-fuel and land-use related releases are 

sources of carbon to the atmosphere. The combined rate of 

release is far larger than can be balanced by the biological 

and geological processes that naturally remove CO2 from the 

atmosphere and store it in terrestrial and marine environments as part of the Earth’s carbon cycle. These processes 

are known as sinks. Therefore, much of the CO2 released 

through human activity has “piled up” in the atmosphere, 

resulting in a dramatic increase in the atmospheric concentration of CO2. The concentration increased by 31% between 

1850 and 2003, and the present concentration is higher than 

at any time in the past 420,000 years. Because CO2 is an 

important greenhouse gas, the imbalance between sources 

and sinks and the subsequent increase in concentration in 

the atmosphere is very likely causing changes in Earth’s 

climate (IPCC, 2007). 

Furthermore, these trends in fossil-fuel use and tropical 

deforestation are accelerating. The magnitude of the changes 

raises concerns about the future behavior of the carbon cycle. 

Will the carbon cycle continue to function as it has in recent 

history, or will a CO2-caused warming result in a weakening of the ability of sinks to take up CO2, leading to further 

warming? Drought, for example, may reduce forest growth. 

Warming can release carbon stored in soil, and warming and 

drought may increase forest fires. Conversely, will elevated 

concentrations of CO2 in the atmosphere stimulate plant 

growth as it is known to do in laboratory and field experiments and thus strengthen global or regional sinks?

The question is complicated because CO2 is not the only 

substance in the atmosphere that affects the Earth’s surface 

temperature and climate. Other greenhouse gases include 

CH4, nitrous oxide, the halocarbons, and ozone, and all of 

these gases, together with water vapor, aerosols, solar radiation, and properties of the Earth’s surface, are involved in 

the evolution of climate change. Carbon dioxide, alone, is 

responsible for approximately 55-60% of the change in the 

Earth’s radiation balance due to increases in well-mixed atmospheric greenhouse gases and CH4 for about another 20% 

(values are for the late 1990s; with a relative uncertainty of 

The rate of CO2 released to the 

atmosphere is far larger than can 

be balanced by the biological and 

geological processes that naturally 

remove CO2 from the atmosphere 

and store it in terrestrial and 

marine environments.

Trends in fossil-fuel use 

and tropical deforestation 

are accelerating.
The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

10%; IPCC, 2001). These two gases are the primary gases 

of the carbon cycle, with CO2 being particularly important. 

Furthermore, the consequences of increasing atmospheric 

CO2 extend beyond climate change alone. The accumulation 

of carbon in the oceans as a result of more than a century of 

fossil-fuel use and deforestation has increased the acidity 

of the surface waters, with serious consequences for corals 

and other marine organisms that build their skeletons and 

shells from calcium carbonate.

Inevitably, the decision to influence or control atmospheric 

concentrations of CO2 as a means to prevent, minimize, or 

forestall future climate change, or to avoid damage to marine 

ecosystems from ocean acidification, will require management of the carbon cycle. That management involves both 

reducing sources of CO2 to the atmosphere and enhancing 

sinks for carbon on land or in the oceans. Strategies may 

involve both short- and long-term solutions. Short-term solutions may help to slow the rate at which carbon accumulates 

in the atmosphere while longer-term solutions are developed. 

In any case, formulation of options by decision makers and 

successful management of the Earth’s carbon budget as part 

of a portfolio of climate-change mitigation and adaptation 

strategies will require solid scientific understanding of the 

carbon cycle.

Understanding the current carbon cycle may not be enough, 

however. The concept of managing the carbon cycle carries 

with it the assumption that the carbon cycle will continue 

to operate as it has in recent centuries. A major concern 

is that the carbon cycle, itself, is vulnerable to land-use or 

climate change that could bring about additional releases 

of carbon to the atmosphere from either land or the oceans. 

Over recent decades both terrestrial ecosystems and the 

oceans have been natural sinks for carbon. If either, or both, 

of those sinks were to become sources, slowing or reversing 

the accumulation of carbon in the atmosphere could become 

much more difficult. Thus, understanding the current global 

carbon cycle is necessary for managing carbon, but is not 

sufficient. Projections of the future behavior of the carbon 

cycle in response to human activity and to climate and other 

environmental change are also important to understanding 

system vulnerabilities.

Perhaps even more 

importantly, effective 

management of the 

carbon cycle requires 

more than basic understanding of the current 

or future carbon cycle. 

It also requires costeffective, feasible, and 

politically palatable options for carbon management. Just 

as carbon cycle knowledge must be assessed and evaluated, 

so must management options and tradeoffs. See Chapter 1 

for further discussion of why the general public, as well as 

individuals and institutions interested in carbon management, should care about the carbon cycle.

ES.3 How do North American

carbon sources and sinks relate

to the global carbon cycle?

In 2004, North America was responsible for approximately 

25% of the CO2 emissions produced globally by fossil-fuel 

combustion (Chapter 2 this report). The United States, 

the world’s largest emitter of CO2, accounted for 86% of 

the North American total in 2004 (85% in 2003). In 2003, 

Canada accounted for 9% and Mexico for 6%, of the total. 

Among all countries, the United States, Canada, and Mexico 

ranked, respectively, as the first, seventh, and eleventh largest emitters of CO2 from fossil fuels in 2003 (Marland et 

al., 2006). The United States ranked eleventh in per capita

emissions (5.43 tons carbon per year) in 2003; Canada ranked 

thirteenth (4.88 tons carbon per year); and Mexico eightyninth (1.10 tons carbon per year). Per capita emissions 

of the United States 

and Canada were, respectively, 4.8 and 4.3 

times the global per 

capita emissions of 1.14 

tons carbon per year. 

Mexico’s per capita

emissions were slightly below the global value. Combined, 

these three countries contributed almost one third (32%) of 

the cumulative global fossil-fuel CO2 emissions between 

A major concern is that the carbon 

cycle, itself, is vulnerable to landuse or climate change that could 

bring about additional releases 

of carbon to the atmosphere 

from either land or the oceans.

In 2004, North America was 

responsible for approximately 25% 

of the CO2 emissions produced 

globally by fossil-fuel combustion.
The U.S. Climate Change Science Program Executive Summary



1751 and 2002. Emissions from parts of Asia are increasing 

at a growing rate and may surpass those of North America 

in the near future, but North America is incontrovertibly a 

major source of atmospheric CO2, historically, at present, 

and in the immediate future.

The contribution of North American carbon sinks to the 

global carbon budget is less clear. The global terrestrial sink 

is quite uncertain, averaging somewhere in the range of 0 to 

3800 million tons of carbon per year during the 1980s, and 

in the range of 1000 to 3600 million tons of carbon per year 

in the 1990s (IPCC, 2000). This report estimates a North 

American sink of approximately 500 million tons of carbon 

per year for 2003, with 95% certainty that the actual value 

is within plus or minus 50% of that estimate, or between 

250 and 750 million tons carbon per year (Chapter 3 this 

report) (see the Text Box on Treatment of Uncertainty). 

Assuming a global terrestrial sink of approximately two billion tons of carbon per year (as inferred by the atmospheric 

analyses for the 1990s), the North American terrestrial sink 

reported here of approximately 500 million tons of carbon 

per year suggests that the North American sink is perhaps 

Sources of uncertainty vary widely across the many sectors and elements of the North American carbon cycle. 

The attention to uncertainty and the methods for dealing with uncertainty also vary across the disciplines that 

study these elements and across individual studies and publications. There is no single applicable quantitative 

method for integrating these variable sources, methods, and characterizations.

To provide for synthesis across and comparability among carbon cycle elements, the following convention has 

been adopted for characterizing uncertainty in the report’s synthetic findings and results (for example, in the 

synthesized carbon budget for North America of Chapter 3 and in the Executive Summary). Uncertainty is 

characterized using five categories: 

(1) ***** = 95% certain that the actual value is within 10% of the estimate reported, 

(2)   = 95% certain that the estimate is within 25%, 

(3) ** * = 95% certain that the estimate is within 50%, 

(4) ** = 95% certain that the estimate is within 100%, and 

(5) * = uncertainty greater than 100%.

Unless otherwise noted, values presented as “y ± x%” should be interpreted to mean that the authors are 95% 

certain the actual value is between y – x% and y + x%. Where appropriate, the absolute range is sometimes 

reported rather than the relative range: y ± z, where z = y × x% ÷ 100. The system of asterisks is used as shorthand for the categories in tables and text.

These are informed categorizations. They reflect expert judgment, using all known published descriptions of uncertainty surrounding the “best available” or “most likely” estimate. The 95% boundary was chosen to communicate the high degree of certainty that the actual value was in the reported range and the low likelihood (1/20) 

that it was outside that range. This characterization is not, however, a statistical property of the estimate, and 

should not be confused with statistically defined 95% confidence intervals.

The authors of this report have used this system for categorizing uncertainty only where they have synthesized 

diverse published information and compared across this diversity. When citing an existing published estimate, 

authors were encouraged to include the characterizations of uncertainty reported by those publications (e.g., 

ranges, standard error, or confidence intervals). There are circumstances in which no characterization of the 

uncertainty of data or information is shown, such as when a number is taken from a published source that itself 

did not include a characterization of uncertainty. In these cases, the authors have not provided a characterization of uncertainty, and the reader should assume that no characterization of uncertainty was available to the 

authors. Additional discussion of sources of uncertainty and their treatment in this report can be found in the 

Preface under “The Treatment of Uncertainty in this Report.”

BOX ES.1: Treatment of Uncertainty
The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

Figure ES.1 North American carbon sources and sinks (million tons of carbon per year) 

in 2003. Height of a bar indicates a best estimate for net carbon exchange between the 

atmosphere and the indicated element of the North American carbon budget. Sources 

add CO2 to the atmosphere; sinks remove it. Error bars indicate the uncertainty in that 

estimate, and define the range of values that include the actual value with 95% certainty. 

See Chapter 3 and Chapters 6-15 of this report for details and discussion of these sources 

and sinks. 

25% of the global sink. In contrast, previous analyses using 

global models of CO2 transport in the atmosphere estimate 

a North American sink for 1991-2000 of approximately one 

billion tons of carbon per year, or approximately 50% of a 

global sink of roughly two billion tons of carbon per year 

(Chapter 2 this report). The North American sink estimate 

of this report is derived from studies using ground-based 

inventories, and the difference between estimates is likely 

influenced by the methodology employed and the period of 

the analysis (Chapters 2 and 3 this report). Developments in 

the use of atmospheric models to estimate terrestrial sinks 

concurrent with the production and publication of this report 

will continue to refine and improve those estimates.

The global terrestrial sink is predominantly in northern 

lands, most likely as a consequence of forest regrowing on 

abandoned agricultural land in northern temperate regions 

(e.g., the eastern United States) and patterns of forest fire 

and recovery in the boreal forests of Canada and Eurasia. 

The sink north of 30 ̊ N alone is estimated to be 600 to 2300 

million tons of carbon per year for the 1980s (IPCC, 2001). 

Thus, the sink of approximately 500 million tons of carbon 

per year in North America is consistent with the fraction of 

northern land area in North America (37%), as opposed to 

Eurasia (63%). Rates of forest clearing in the tropics, including those of Mexico, currently exceed rates of recovery, and 

thus tropical regions dominated by rainforests or other forest 

types are currently a source of carbon to the atmosphere.

It is clear that the global carbon cycle of the 21st century 

will continue to be influenced by large fossil-fuel emissions 

from North America, and that the North American carbon 

budget will continue to be dominated by the fossil-fuel 

sources. The future trajectory of carbon sinks in North America and their 

contribution to the global terrestrial 

sink is less certain, in part because 

the role of regrowing forests is likely 

to decline as the forests mature, 

and in part because the response 

of forests and other ecosystems to 

future climate change and increases 

in atmospheric CO2 concentrations 

is uncertain. The variation among 

model projections and scenarios of 

where and how future climate will 

change contribute to that uncertainty. 

Additionally, response to a particular 

future change will likely vary among 

ecosystems and the response will 

depend on a variety of incompletely 

understood environmental factors.

ES.4 What are the

primary carbon sources and sinks

in North America, and how and

why are they changing?

ES.4.1 The Sources

The primary source of human-caused carbon emissions in 

North America that contributes to the increase of CO2 in the 

atmosphere is the release of CO2 during the combustion of 

fossil fuels (Figure ES.1) (Chapter 3 this report). Fossil-fuel 

carbon emissions in the United States, Canada, and Mexico 

totaled approximately 1900 million tons of carbon in 2003 

(with 95% confidence that the actual value lies within 10% 

of that estimate1) and have increased at an average rate 

of approximately 1% per year for the last 30 years. The 

United States was responsible for approximately 85% of 

North America’s fossil-fuel emissions in 2003, Canada for 

9%, and Mexico 6% (Table ES.1). The overall 1% growth 

in United States’ emissions masks faster than 1% growth 

in some sectors (e.g., transportation) and slower growth in 

others (e.g., increased 

manufacturing energy 

efficiency).

Total United States’ 

emissions have grown 

at close to the North 

American average rate 

of about 1.0% per year over the past 30 years, but United 

States’ per capita emissions have been roughly constant, 

while the carbon intensity (carbon emitted/dollar of real [inflation adjusted] GDP) of the United States’ economy has de1

 See Text Box ES.1 for a discussion of numerical data and 

estimates.

Fossil-fuel carbon emissions in 

the United States, Canada, and 

Mexico have increased at an 

average rate of approximately 1% 

per year for the last 30 years.
The U.S. Climate Change Science Program Executive Summary

Table ES.1 North American annual net carbon emissions (source = positive) or uptake (land sink = negative) (million tons carbon per year) by country. See Table 3.1, Chapter 3 of this report for references 

to sources of data.

Uncertainty:

*****(95% confidence within 10%)

 (95% confidence within 25%)

** *(95% confidence within 50%)

**(95% confidence within 100%)

*(95% confidence bounds >100%)

ND = No data available

a Coastal waters within 100 km of the North American coastline, defined by the region in which the surface water 

concentration of CO2 is inflluenced by coastal processes, may be a source of 19 million tons of carbon per year but with 95% 

confidence bounds greater than 100% (i.e., they may be a small sink). See discussion of coastal ocean sources and sinks in 

Chapters 3 and 15 of this report, and their distribution by ocean region rather than country in Chapter 15 of this report. 

Source (positive) or Sink (negative) United States Canada Mexico North America

Fossil source (positive)

Fossil fuel (oil, gas,coal)

1582*****

(681, 328, 573)

164*****

(75, 48, 40)

110*****

(71, 29, 11)

1856*****

(828,405,624)

Non-fossil carbon sink (negative) or source 

(positive)

Forest -256*** -28** +52** -233***

Wood products -57*** -11*** ND -68***

Woody encroachment -120* ND ND -120*

Agricultural soils -8*** -2*** ND -10***

Wetlands -23* -23* -4* -49*

Rivers and lakes -25** ND ND -25*

Coastal oceans a

Total carbon source or sink -489*** -64** 48* -505***

Net carbon source (positive) 1093  100** * 158*** 1351 

creased at a rate of about 2% per year (Chapter 3 this report). 

The decline in the carbon intensity of the United States’ 

economy was caused both by increased energy efficiency, 

particularly in the manufacturing sector, and structural 

changes in the economy with growing contributions from 

sectors such as services with lower energy consumption and 

carbon intensity. The service sector is likely to continue to 

grow. Accordingly, carbon emissions will likely continue to 

grow more slowly than GDP (Chapter 3 this report).

The extraction of fossil-fuels and other primary energy 

sources and their conversion to energy commodities and services, including electricity generation, is 

the single largest contributor to the North 

American fossil-fuel 

source, accounting for 

approximately 42% of 

North American fossil 

emissions in 2003 (Chapter 6 this report). Electricity generation is responsible for the largest share of those emissions: 

approximately 94% in the United States in 2004, 65% in 

Canada in 2003, and 67% in Mexico in 1998. Again, United 

States’ emissions dominate. United States’ emissions from 

electricity generation are approximately 17 times larger than 

those of Canada and 23 times those of Mexico, reflecting 

in part the relatively greater population of the United States 

in both cases and its much higher level of development than 

Mexico. On a per capita basis, the emissions from electricity 

generation are 2.14 tons of carbon for the United States in 

2004, 1.15 tons of carbon for Canada in 2003, and 0.28 tons 

of carbon for Mexico in 1998 (note these are the latest years 

for which data are available).

More than half of electricity produced in North America 

(67% in the United States) is consumed in buildings, making 

that single use one of the largest factors in North American emissions (Chapter 9 this report). In fact, in 2003 the 

CO2 emissions from United States’ buildings alone were 

The extraction of fossil-fuels 

and their conversion to energy 

commodities and services, including 

electricity generation, is the single 

largest contributor to the North 

American fossil-fuel source.
The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

greater than total CO2 emissions of any country in the 

world, except China. Energy use in buildings in the United 

States and Canada (including the use of natural gas, wood, 

and other fuels as well as electricity) has increased by 

30% since 1990, corresponding to an annual growth rate 

of 2.1%. In the United States, the major drivers of energy 

consumption in the buildings sector are growth in commercial floor space and increase in the size of the average 

home. Carbon emissions from buildings are expected to 

grow with population and income. Furthermore, the shift 

from family to single-occupant households means that the 

number of households will increase faster than population 

growth—each household with its own heating and cooling 

systems and electrical appliances. Certain electrical appliances (such as air-conditioning equipment) once considered 

a luxury are now becoming commonplace. Technology- and 

market-driven improvements in the efficiency of appliances 

are expected to continue, but the improvements will probably 

not be sufficient to curtail emissions growth in the buildings 

sector without government intervention.

The transportation sector of North America accounted 

for 31% of total North American emissions in 2003, most 

(87%) of it from the United States (Chapter 7 this report). 

The growth in transportation and associated CO2 emissions 

has been steady during the past forty years and has been 

most rapid in Mexico, the country most dependent upon 

road transport. The growth of transportation is driven by 

population, per capita income, and economic output, and 

energy use in transportation is expected to increase by 46% 

in North America between 2003 and 2025. If the mix of 

fuels is assumed to remain the same, CO2 emissions would 

increase from 587 million tons of carbon in 2003 to 859 

million tons of carbon in 2025.

Emissions from North American industry (not including fossil-fuel mining and processing or electricity 

generation) are a relatively small (12%) and declining 

component of North America’s emissions (Chapter 8 this 

report). Emissions decreased nearly 11% between 1990 

and 2002, while energy consumption in the United States 

and Canada increased by 8-10% during that period. In 

both countries, a shift in production toward less energyintensive industries and dissemination of more energy 

efficient equipment has kept the rate of growth in energy 

demand lower than the rate of growth of industrial GDP. 

Emission reductions in industry have also resulted from 

the voluntary, proactive initiatives of both individual 

corporations and trade associations in response to climate 

change issues (Chapter 4 this report).

The remaining portion (approximately 15%) of North 

American fossil-fuel emissions includes those from other 

sectors. This includes natural gas and other non-electrical 

fossil energy used in residential and commercial buildings 

and fuels used in agriculture.

ES.4.2 The Sinks

Approximately 30% of North American fossil-fuel emissions 

are offset by a sink of approximately 500±250 million tons of 

carbon per year. The uncertainty in the North American sink 

of ±50% is substantially larger than the ±10% uncertainty 

in the emissions source. The total sink is a combination of 

many factors, including forest regrowth, fire suppression, 

and agricultural soil conservation (Figure ES.1, Chapter 3, 

Part III: Chapters 10-15 this report). The sink is currently 

about 490 million tons of carbon per year in the United 

States and approximately 60 million tons of carbon per year 

in Canada. Mexican ecosystems are a net source of about 50 

million tons of carbon per year, mostly as a consequence of 

ongoing deforestation. The coastal ocean surrounding North 

America is perhaps an additional small net source of carbon 

to the atmosphere of approximately 20 million tons of carbon 

per year. The coastal ocean is, however, highly variable, and 

that number is highly uncertain with variability (standard 

deviation) of greater than 100%. North America’s coastal 

waters could be a small sink and in some places are. How 

much the coastal carbon exchange with the atmosphere is 

influenced by humans is also unknown.

The primary carbon sink in North America (approximately 

50% of the total) is in the forests of the United States and 

Canada (Table ES.1). These forests are still growing (accumulating carbon) after their re-colonization of farmland 100 

or more years ago. Forest regrowth takes carbon out of the 

atmosphere and stores most of it in above-ground vegetation 
The U.S. Climate Change Science Program Executive Summary

(wood), with as much 

as a third of it in soils. 

The suppression of forest fires also increases 

net accumulation of 

carbon in forests. As 

the recovering forests 

mature, however, the rate of net carbon uptake (the sink) 

declines. In Canada, the estimated forest sink declined by 

nearly a third between 1990 and 2004, but with high yearto year variability. Over that period, the annual changes in 

above-ground carbon stored in managed Canadian forests 

varied from between a sink of approximately 50 million tons 

of carbon per year to a source of approximately 40 million 

tons of carbon per year. Years when the forests were a source 

were generally years with high forest fire activity.

Woody encroachment, 

the invasion of woody 

plants into grasslands 

or of trees into shrublands, is a potentially 

large, but highly uncertain carbon sink. It 

is caused by a combination of fire suppression 

and grazing. Fire inside 

the United States has 

been reduced by more than 95% from the pre-settlement 

levels, and this reduction favors shrubs and trees in competition with grasses. The sink may be as large as 20% of 

the North American sink, but it may also be negligible. The 

uncertainty of this estimate is greater than 100%. If that 

highly uncertain sink is excluded (see Overview of Part III 

this report), the estimate of the North American sink falls to 

385 million tons of carbon per year or approximately 20% of 

fossil-fuel emissions in 2003. Woody encroachment might 

actually be a source, maybe even a relatively large one. 

The state of the science is such that we simply don’t know 

(Chapter 3 and Part III Overview this report).

Wood products are thought to account for about 13% of the 

total North American sink. The uncertainty in this sink is 

±50%. Wood products are a sink because they are increasing, 

both in use (e.g., furniture, house frames, etc.) and in landfills. The wetland sink, about 9% of the North American sink 

but with an uncertainty of greater than 100%, is in both the 

peats of Canada’s extensive frozen (permafrost) and unfrozen wetlands and the mineral soils of Canadian and United 

States’ wetlands. Drainage of peatlands in the United States 

has released carbon to the atmosphere, and the very large 

volume of carbon in North American wetlands (the single 

largest carbon reservoir of any North American ecosystem) 

is vulnerable to release in response to both climate change 

and the further drainage of wetlands for development. Either 

change might shift the current modest sink to a potentially 

large source, although many aspects of wetlands and their 

future behavior are poorly known.

Two processes determine the carbon balance of agricultural 

lands: management and changes in environmental factors. 

The effects of management (e.g., cultivation, conservation 

tillage) are reasonably well known and have been responsible 

for historic losses of carbon in Canada and the United States 

(and current losses in Mexico), albeit with some increased 

carbon uptake and storage in recent years. Agricultural lands 

in North America are nearly neutral with respect to carbon, 

with mineral soils absorbing carbon and organic soils releasing it. The balance of these sinks and sources is a net sink 

of 10±5 million tons of carbon per year (Table ES.1). The 

effects of climate on this balance are not well known.

Soil erosion leads to the accumulation of carbon containing sediments in streams, rivers, and lakes (both natural 

and man-made). This represents a carbon sink, estimated 

at approximately 25 million tons of carbon per year for the 

United States. We know of no similar analysis for Canada or 

Mexico. The result is a highly uncertain estimate for North 

America known to no better than the estimate for the United 

States alone, plus or minus more than 100%.

The very large volume of carbon 

in North American wetlands (the 

single largest carbon reservoir of 

any North American ecosystem) 

is vulnerable to release in 

response to both climate change 

and the further drainage of 

wetlands for development.

The primary carbon sink in North 

America (approximately 50% 

of the total) is in the forests of 

the United States and Canada.
The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

The density and development patterns of human settlements 

are drivers of fossil-fuel emissions, especially in the important residential and transportation sectors. Conversion of 

agricultural and wildlands to cities and other human settlements reduces carbon stocks, while the growth of urban 

and suburban trees increases them. The growth of urban 

trees in North America produces a sink of approximately 

16 to 49 million tons of carbon per year, which is 1 to 3% of 

North American fossil-fuel emissions in 2003. Settlements 

in North America are thus almost certainly a net source of 

atmospheric CO2.

ES.5 What are the direct, nonclimatic effects of increasing

atmospheric carbon dioxide or

other changes in the carbon

cycle on the land and oceans of

North America?

The potential impacts of increasing concentrations of atmospheric CO2 (and other greenhouse gases) on the Earth’s 

climate are well documented (IPCC, 2007) and are the 

dominant reason for societal interest in the carbon cycle. 

However, the consequences of a carbon cycle imbalance 

and the buildup of CO2 in the atmosphere extend beyond 

climate change alone. Ocean acidification and “CO2 fertilization” of land plants are foremost among these direct, 

non-climatic effects.

The uptake of carbon by the world’s oceans as a result of 

human activity over the last century has made them more 

acidic (Chapters 1 and 2 this report). This acidification 

negatively impacts corals and other marine organisms that 

build their skeletons and shells from calcium carbonate. 

Future changes could dramatically alter the composition of 

ocean ecosystems of North America and elsewhere, possibly 

eliminating coral reefs by 2100.

Rates of photosynthesis 

of many plant species 

often increase in response to elevated concentrations of CO2, thus 

potentially increasing 

plant growth and even 

agricultural crop yields in the future (Chapters 2, 3, 10-13 

this report). There is, however, continuing scientific debate 

about whether such “CO2 fertilization” will continue into 

the future with prolonged exposure to elevated CO2, and 

whether the fertilization of photosynthesis will translate into 

increased plant growth and net uptake and storage of carbon 

by terrestrial ecosystems. Recent studies provide many conflicting results. Experimental treatment with elevated CO2

can lead to consistent increases in plant growth. On the other 

hand, it can also have little effect on plant growth, with an 

initial stimulation of photosynthesis but limited long-term 

effects on carbon accumulation in the plants. Moreover, it is 

unclear how plants and ecosystem might respond simultaneously to both “CO2 fertilization” and climate change. While 

there is some experimental evidence that plants may use less 

water when exposed to elevated CO2, extended deep drought 

or other unfavorable climatic conditions could reduce the 

positive effects of elevated CO2 on plant growth. Thus, it is 

far from clear that elevated concentrations of atmospheric 

CO2 have led to terrestrial carbon uptake and storage or 

will do so over large areas in the future. Moreover, elevated 

carbon dioxide is known to increase CH4 emissions from 

wetlands, further increasing the uncertainty in how plant 

response to elevated CO2 will affect the global atmosphere 

and climate.

The carbon cycle also intersects with a number of critical 

Earth system processes, including the cycling of both water 

and nitrogen. Virtually any change in the lands or waters of 

North America as part 

of purposeful carbon 

management will consequently affect these 

other processes and 

cycles. Some interactions may be beneficial. 

For example, an increase in organic carbon in soils is likely 

to increase the availability of nitrogen for plant growth 

The growth of urban trees in 

North America produces a 

sink of approximately 1 to 3 

percent of North American 

fossil-fuel emissions in 2003.

The carbon cycle also intersects 

with a number of critical Earth 

system processes, including the 

cycling of both water and nitrogen.
The U.S. Climate Change Science Program Executive Summary

10 

and enhance the water-holding capacity of the soil. Other 

interactions, such as nutrient limitation, fire, insect attack, 

increased respiration from warming, may be detrimental. 

However, very little is known about the complex web of interactions between carbon and other systems at continental 

scales, or the effect of management on these interactions.

ES.6 What potential management

options in North America could

significantly affect the North

American and global carbon

cycles (e.g., North American sinks

and global atmospheric carbon

dioxide concentrations)?

Addressing imbalances in the North American and global 

carbon cycles requires a mix of options, no single option being sufficient, focused on reducing carbon emissions (Chapter 4 this report). Options focused on enhancing carbon sinks 

in soils and vegetation in North America can contribute 

as well, but the potential 

of these options alone is 

insufficient to deal with 

the magnitude of current 

imbalances in the North 

American carbon budget 

and their contributions to 

the global imbalance.

Currently, options for reducing carbon emissions include:

Reducing emissions from the transportation sector 

through efficiency improvement, higher prices for 

carbon-based fuels, liquid fuels derived from vegetation (ethanol from corn or other biomass feedstock, for 

example), and in the longer run (after 2025), hydrogen 

generated from non-fossil sources of energy;

Reducing the carbon emissions associated with energy 

use in buildings through efficiency improvements and 

energy-saving passive design measures;

Reducing emissions from the industrial sector through 

efficiency improvement, fuel-switching, and innovative 

process designs;

Reducing emissions from energy extraction and conversion through efficiency improvement, fuel-switching, 

technological change (including carbon sequestration 

and capture and storage), and reduced demands due to 

increased end-use efficiency; and 

Capturing the CO2 emitted from fossil-fired generating 

units and injecting it into a suitable geological formation or deep in the sea for long-term storage (carbon 

capture and storage).

Options for managing terrestrial carbon stocks include:

Maintaining existing terrestrial carbon stocks in vegeta-

•

•

•

•

•

•

tion and soils and in wood products;

Reducing carbon loss associated with land management 

practices, including those of agriculture (e.g., reduced 

tillage in expanding croplands) and forest harvest (e.g., 

minimizing soil disturbance); and

Increasing terrestrial carbon sequestration through afforestation, reforestation, planting of urban “forests,” 

reduced tillage in established crop lands, and similar 

practices.

In many cases, significant progress with such options would 

require a combination of technology research and development, policy interventions, and information and education 

programs.

Opinions differ about the relative mitigation impact of emission reduction versus carbon sequestration. Assumptions 

about the cost of mitigation and the policy instruments used 

to promote mitigation significantly affect assessments of 

mitigation potential. For example, appropriately designed 

carbon emission cap and trading policies could achieve a 

given level of carbon emissions reduction at lower cost than 

some other policy instruments by providing incentives to 

use the least-cost combination of mitigation/sequestration 

alternatives.

However, the evaluation of any policy instrument should 

consider technical, institutional, and socioeconomic constraints that would affect its implementation, such as the 

ability of sources to monitor their actual emissions and the 

constitutional authority of national and/or provincial/state 

governments to impose emissions taxes, regulate emissions, 

and/or regulate efficiency standards. Also, practically every 

policy (except cost-saving energy conservation options), no 

matter what instrument is used to implement it, has a cost in 

terms of utilization of resources and ensuing price increases 

that leads to reductions in output, income, employment, or 

other measures of economic well-being. These costs must 

be weighed against the benefits (or avoided costs) of reducing carbon emissions. In addition to the standard reduction 

in damages noted above, many options and measures that 

reduce emissions and increase sequestration also have significant co-benefits in terms of economic efficiency (where 

market failures are being corrected, as in many cases of 

energy conservation), environmental management, and 

energy security.

The design of carbon management systems must also consider unintended consequences involving other greenhouse 

gases. For instance, carbon sequestration strategies such as 

reduced tillage can increase emissions of CH4 and nitrous 

oxide, which are also greenhouse gases. Strategies for dealing with climate change will have to consider these other 

gases as well as other components of the climate systems, 

•

•

Addressing imbalances in the 

North American and global 

carbon cycles requires a 

mix of options focused on 

reducing carbon emissions.
11

The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

such as small airborne particles and the physical aspects of 

plant communities.

Direct reductions of carbon emissions from fossil-fuel 

use are considered “permanent” reductions, while carbon 

sequestration in plants or soils is a “non-permanent” reduction, in that carbon stored through conservation practices 

could potentially be re-emitted if management practices 

revert back to the previous state or otherwise change. This 

permanence issue applies to all forms of carbon sinks. For 

example, the carbon sink associated with forest regrowth 

could be slowed or reversed from sink to source if the forests 

are burnt in wildfires or forest harvest and management 

practices change.

Changes in land management (e.g., tillage reduction, pasture 

improvement, afforestation) will stimulate the uptake and 

sequestration of carbon for only a finite period. Over time, 

the processes of carbon gain and loss from vegetation and 

soil come into a new balance with the change in land use 

and land management. The amount of carbon stored in the 

plants and soil will tend to level off at a new maximum with 

the altered processes of uptake balanced by altered processes 

of release, after which there is no further accumulation 

(sequestration) of carbon. For example, following changes 

in tillage to promote carbon absorption in agricultural soils 

(Chapter 10 this report) the amount of carbon in the soil will 

tend to reach a new constant level after 15–30 years. The 

sink declines, then disappears, or nearly so, as the amount 

of carbon being added to the soil is balanced by losses. The 

same pattern is observed as forests are planted, as they regrow on abandoned farmland or as they recover from fire, 

harvest, or other disturbance. It takes significantly longer 

for forests to reach a new balance of uptake and release with 

many forests sequestering significant amounts of carbon 125 

years after establishment, but as forests mature, the rate of 

sequestration declines and in old growth forests processes 

of carbon uptake are very nearly balanced by processes of 

release (Chapters 3 and 11 this report).

Mitigation actions in one area (e.g., geographic region, 

production system) can inadvertently result in additional 

emissions elsewhere. This phenomenon, commonly referred 

to as leakage, can occur when a policy of emission reduction 

by one country shifts emission-intensive industry or energy 

production toward other countries, increasing their emissions and thus reducing the overall benefit. Similarly, leakage can be a concern for sequestration and storage of carbon 

in forests. Reducing harvest rates in one area, for example, 

can stimulate increased cutting and reduction in stored 

carbon in other areas. Leakage may be of minor concern for 

agricultural carbon storage, since most practices would have 

little or no effect on the supply and demand of agricultural 

commodities. Chapter 4 further compares measures taken 

to reduce emissions 

with those taken to 

sequester carbon.

Options and measures 

can be implemented 

in a variety of ways at 

a variety of scales, not 

only at international 

or national levels. For example, a number of municipalities, 

state governments, and private firms in North America have 

made commitments to voluntary greenhouse gas emission 

reductions. For cities, one focus has been the Cities for 

Climate Protection program of International Governments 

for Local Sustainability (formerly ICLEI). For some states 

and provinces, the Regional Greenhouse Gas (Cap and 

Trade) Initiative is nearing implementation. For industry, 

one focus has been membership in the Pew Center and in 

the Environmental Protection Agency (EPA) Climate Leaders Program.

ES. 7 How can we improve the

usefulness of carbon science for

decision making?

Effective carbon management requires that relevant, appropriate science be communicated to the wide variety of 

people whose decisions affect carbon cycling (Chapter 5 this 

report). Because the field is relatively new and the demand 

for policy-relevant information has been limited, carbon 

cycle science has rarely been organized or conducted to 

inform carbon management. To generate information that 

can systematically inform carbon management decisions, 

scientists and decision makers should clarify what information would be most relevant in specific sectors 

and arenas for carbon 

management, adjust 

research priorities as 

necessary, and develop 

mechanisms that enhance the credibility 

and legitimacy of the 

information being generated.

In the United States, the federal carbon science enterprise 

does not yet have many mechanisms to assess emerging 

demands for carbon information across scales and sectors. 

Federally funded carbon science has focused predominantly 

on basic research to reduce uncertainties about the carbon 

cycle. Initiatives are now underway to promote coordinated, 

interdisciplinary research that is strategically prioritized to 

address societal needs. The need for this type of research 

is increasing. Interest in carbon management across sectors 

Many options and measures 

that reduce emissions and 

increase sequestration also have 

significant co-benefits in terms of 

economic efficiency, environmental 

management, and energy security.

A number of municipalities, 

state governments, and private 

firms in North America 

have made commitments 

to voluntary greenhouse 

gas emission reductions.
The U.S. Climate Change Science Program Executive Summary

12 

suggests that there may be substantial demand for information in the energy, transportation, agriculture, forestry, and 

industrial sectors, at scales ranging from local to global.

To ensure that carbon science is as useful as possible for 

decision making, carbon scientists and carbon managers 

need to create new forums and institutions for communication and coordination. Research suggests that in order to 

make a significant contribution to management, scientific 

and technical information intended for decision making must 

be perceived not only as credible (worth believing), but also 

as salient (relevant to decision making on high priority issues) and legitimate (conducted in a way that stakeholders 

believe is fair, unbiased, and respectful of divergent views 

and interests). To generate information that meets these tests, 

carbon stakeholders and scientists need to collaborate to 

develop research questions, design research strategies, and 

review, interpret, and disseminate results. Transparency and 

balanced participation are important for guarding against 

politicization and enhancing usability.

To make carbon cycle science more useful to decision makers in the United 

States and elsewhere in 

North America, leaders 

in the carbon science community might consider the 

following steps:

Identify specific categories of decision makers for 

whom carbon cycle science is likely to be salient, focusing on policy makers and private sector managers 

in carbon-intensive sectors (energy, transport, manufacturing, agriculture, and forestry);

Identify and evaluate existing information about carbon 

impacts of decisions and actions in these arenas, and 

assess the need and demand for additional information. 

In some cases, demand may need to be nurtured and 

fostered through a two-way interactive process;

Encourage scientists and research programs to experiment with new and different ways of making carbon 

cycle science more salient, credible, and legitimate to 

carbon managers;

Involve not just physical or biological disciplines in 

scientific efforts to produce useable science, but also 

social scientists, economists, and communication experts; and

Consider initiating participatory pilot research projects 

and identifying existing “boundary organizations” (or 

establishing new ones) to bridge carbon management 

and carbon science.

•

•

•

•

•

ES.8 What additional knowledge

is needed for effective carbon

management?

Scientists and carbon managers need to improve their 

joint understanding of the top priority questions facing 

carbon-related decision-making. Priority needs specific to 

individual ecosystem or sectors are described in Chapters 

6-15 of this report. To further prioritize those needs across 

disciplines and sectors, scientists need to collaborate more 

effectively with decision makers in undertaking research and 

interpreting results in order to answer those questions. More 

deliberative processes of consultation with potential carbon 

managers at all scales can be initiated at various stages of 

the research process. This might include workshops, focus 

groups, working panels, and citizen advisory groups. Research on the effective production of science that can be 

used for decision making suggests that ongoing, iterative 

processes that involve decision makers are more effective 

than those that do not (Chapter 5 this report).

In the light of changing views on the impacts of CO2 released to the atmosphere, research and development will 

likely focus on the extraction of energy while preventing 

CO2 release. Fossil fuels might well remain economically 

competitive and socially desirable as a source of energy in 

some circumstances, even when one includes the extra cost 

of capturing the CO2 and preventing its atmospheric release 

Initiatives are now underway 

to promote coordinated, 

interdisciplinary research 

that is strategically prioritized 

to address societal needs.
13

The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

when converting these fuels into non-carbon secondary 

forms of energy like electricity, hydrogen, or heat. Research 

and development needs in the energy and conversion arena 

include clarifying potentials for carbon capture and storage, 

exploring how to make renewable energy affordable at large 

scales of deployment, examining societal concerns about 

nuclear energy, and learning more about policy options for 

distributed energy and energy transitions. There is also need 

for better understanding of the public acceptability of policy 

incentives for reducing dependence on carbon intensive 

energy sources.

In the transportation sector, improved data on Mexican 

greenhouse gas emissions and trends is needed, as well as on 

the potential for mitigating transportation-related emissions 

in North America. Advances in transportation mitigation 

technologies and policies are also needed. In the industry and 

waste management sectors, work on materials substitution 

and energy efficient technologies in production processes 

holds promise for greater emissions reductions. Needs for 

the building sector include: further understanding the total 

societal costs of CO2 as an externality of buildings costs, 

economic and market analyses of various reduced emission 

features at various time scales of availability, and construction of cost curves for emission reduction options.

Turning to the ecosystem arena, the synthesis and assessment of this report provides a baseline against which future 

results from the North American Carbon Program (NACP) 

can be compared. The report also highlights key uncertainties in North American sources and sinks. For example, in 

the agricultural and grazing land sectors, inventories still 

carry a great deal of uncertainty, especially in the arena of 

woody encroachment. If such inventories are to be the basis 

for future decision making, reducing such uncertainties may 

be a useful investment. Quantitative estimates of land-use change 

and the impact of various management practices are also highly 

uncertain, as are the interactions 

among CO2, CH4, and nitrous oxide 

as greenhouse gas emissions. If 

carbon accounting becomes a critical feature of carbon management, 

improved data are needed on the 

relationship of forest management 

practices to carbon storage, as well 

as inexpensive tools and techniques 

for monitoring. An assessment of 

agroforestry practices in Mexico 

as well as in temperate landscapes 

would also be helpful. Importantly, 

there is a need for multi-criteria 

analysis of various uses of landscapes—tradeoffs between carbon storage and other uses of 

the land must be considered. If markets emerge more fully 

for trading carbon credits, the development of such decision 

support tools will likely be encouraged.

Soils in the permafrost region store vast amounts of carbon 

and are currently a small sink. There is, however, little 

certainty about how these soils will respond to changes 

brought about by climate. While these regions are likely 

not subject to management options, improved information 

on carbon storage and the trajectory of these reservoirs may 

provide additional insight into the likelihood of release of 

large amounts of carbon to the atmosphere that may affect 

global decision making. Similarly, there is great uncertainty 

in the response of the carbon pools of wetlands to climate 

changes, and very little data on freshwater mineral soils and 

estuarine carbon both in Canada and Mexico.

With respect to human settlements, additional studies of 

the carbon balance of settlements of varying densities, 

geographical location, and patterns of development are 

needed to quantify the potential impacts of various policy 

and planning alternatives on net greenhouse gas emissions. 

In coastal regions, additional information on carbon fluxes 

will help to constrain continental carbon balance estimates 

should information on that scale become useful for decision 

making. Research on ocean carbon uptake and storage is also 

needed in order to fully inform decision making on options 

for carbon management.

With respect to carbon management, there is a need for more 

insight into how incentives to reduce emissions affect the 

behavior of households and businesses, the influence of reducing uncertainty on the willingness of decision makers to 

make commitments, the affect of increased R&D spending 
The U.S. Climate Change Science Program Executive Summary

14 

on technological innovation, the socioeconomic distribution of mitigation/sequestration costs and benefits, and the 

manner in which mitigation costs and policy instrument 

design affect the macroeconomy. Improvements in decision analysis in the face of irreducible uncertainty would 

be helpful as well.

Finally, CH4 is second only to CO2 as an important humancaused greenhouse gas. Methane sources and sinks are, 

however, not nearly as well understood as those for CO2,

and the consideration of CH4 as part of the North American 

carbon budget is consequently well beyond the scope of this 

report. Research to better understand CH4 sources and sinks 

and better integrate CH4 into understanding of the carbon 

cycle could improve knowledge of how carbon management 

might influence both CO2 and CH4 in the atmosphere.
What Is the Carbon Cycle and Why 

Care?

CHAPTER

1

15

Author Team: Anthony W. King, ORNL; Lisa Dilling, Univ. Colo./

NCAR; Gregory P. Zimmerman, ORNL; David M. Fairman, Consensus 

Building Inst., Inc.; Richard A. Houghton, Woods Hole Research 

Center; Gregg Marland, ORNL and Mid Sweden Univ. (Östersund); 

Adam Z. Rose, The Pa. State Univ. and Univ. Southern Calif.; Thomas J. 

Wilbanks, ORNL

The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

1.1 WHY A REPORT ON THE CARBON 

CYCLE?

The concept of a carbon cycle is probably unfamiliar to 

most people other than scientists and some decision makers in the public and private sectors. More familiar is the 

water cycle, where precipitation falls on the earth to supply 

water bodies and evaporation returns water vapor to the 

clouds, which then renew the cycle through precipitation. 

In an analogous way, carbon—a fundamental requirement 

for life on Earth—cycles through exchanges among stores 

(or reservoirs) of carbon on and near the Earth’s surface 

(mainly in plants and soils), in the atmosphere (mainly as 

gases), and in water and sediments in the ocean. Stated in 

oversimplified terms, plants take up carbon dioxide (CO2) 

from the atmosphere through photosynthesis and create 

sugars and other carbohydrates, which animals and humans 

use for food, shelter, and energy to sustain life. Emissions 

from plants, other natural systems, and human activities 

return carbon to the atmosphere, which renews the cycle 

(Figure 1.1).

All of the components of this cycle—the atmosphere, the 

terrestrial vegetation, soils, freshwater lakes and rivers, the 

ocean, and geological sediments—are reservoirs (stores) of 

carbon. As carbon cycles through the system, it is exchanged 

between reservoirs, transferred from one to the next, with 

exchanges often in both directions. The carbon budget is an 

accounting of the balance of exchanges of carbon among the 

reservoirs: how much carbon is stored in a reservoir at a particular time, how much is coming in from other reservoirs, 

and how much is going out. When the inputs to a reservoir 

(the sources) exceed the outputs (the sinks), the amount of 

carbon in the reservoir is increased. The myriad physical, 

chemical, and biological processes that transfer carbon 

among reservoirs, and transform carbon among its various 

molecular forms during those transfers, are responsible for 

the cycling of carbon through reservoirs. That cycling determines the balance of the carbon budget observed at any 

particular time. Quantifying the carbon budget over time 

can reveal whether the budget is or is not in balance (carbon 

accumulating in a reservoir would indicate an imbalance). If 

found to be out of balance, this quantification can provide 

understanding about why such a condition exists (for example, which sources exceed which sinks over what periods) 

(Sabine et al., 2004, Chapter 2 this report). If the imbalance 

is deemed undesirable, the understanding of source and 

sinks can provide clues into how it might be managed (for 

example, which sinks are large relative to sources and might, 

if managed, provide leverage on changes in a reservoir) (Caldeira et al., 2004; Chapter 4 this report). The global carbon 

budget is currently out of balance, with carbon accumulating 

in the form of CO2 and methane (CH4) in the atmosphere 

since the preindustrial era (circa 1750). Human use of coal, 

petroleum, and natural gas, combined with agriculture and 

other land-use change is primarily responsible. Documented 

by the Intergovernmental Panel on Climate 

Change for the 1990s 

(IPCC, 2001, p. 4), 

these trends continue 

in the early twenty-first 

century (Keeling and 

Whorf, 2005; Marland 

et al., 2006).

The history of the Earth’s carbon balance as reflected in 

changes in atmospheric CO2 concentration can be reconstructed from geological records, geochemical reconstructions, measurements on air bubbles trapped in glacial ice, 

and in recent decades, direct measurements of the atmosphere. Over the millennia, tens and hundreds of millions of 

The global carbon budget is 

currently out of balance, with 

carbon accumulating in the form 

of CO2 and methane (CH4) 

in the atmosphere since the 

preindustrial era (circa 1750).
The U.S. Climate Change Science Program Chapter 1

16 

years ago, vast quantities of carbon were stored in residues 

from dead plant and animal life that sank into the earth 

and became fossilized. On these time scales, small imbalances in the carbon cycle and geological processes, acting 

over millions of years, produced large but slow changes 

in atmospheric CO2 concentrations of greater than 3000 

parts per million (ppm) over periods of 150-200 million 

years (Prentice et al., 2001). By perhaps 20 million year 

ago, atmospheric CO2 concentrations were less than 300 

ppm (Prentice et al., 2001). Subsequently, imbalances in the 

carbon cycle linked with climate variations, especially the 

large glacial-interglacial cycles of the last 420,000 years, 

resulted in changes of approximately 100 ppm over periods 

of 50-75 thousand years (Prentice et al., 2001; Sabine et al., 

2004). During the current interglacial climate, for at least the 

last 11,000 years, variations in atmospheric CO2, also likely 

climate driven, were less than 20 ppm (Joos and Prentice, 

2004). For 800-1000 years prior to the Industrial Revolution 

of the 1700s and 1800s, atmospheric CO2 concentrations 

varied by less than 10 ppm (Prentice et al., 2001).

With the advent of the steam engine, the internal combustion 

engine, and other technological and economic elements of 

the Industrial Revolution, human societies found that the 

fossilized carbon formed hundreds of millions of years ago 

had great value as energy sources for economic growth. The 

1800s and 1900s saw a dramatic rise in the combustion of 

these “fossil fuels” (e.g., coal, petroleum, and natural gas), 

releasing into the atmosphere, over decades, quantities of 

carbon that had been stored in the Earth system over millennia. These fossil-fuel emissions combined with and soon 

exceeded (circa 1910) the CO2 emissions from burning and 

decomposition of dead plant material that accompanied 

clearing of forests for agricultural land use (Houghton, 

2003).

It is not surprising, then, that measurements of CO2 in 

the Earth’s atmosphere have shown a steady increase in 

concentration over the twentieth century (Keeling and 

Whorf, 2005). The global CO2 concentration has increased 

by approximately 100 ppm over the past 200 years, from a 

preindustrial concentration of 280 ± 10 ppm (Prentice et al., 

2001) to a concentration (measured at Mauna Loa, Hawaii) of 

369 ppm in 2000 and 377 ppm in 2004 (Keeling and Whorf, 

2005). Methane shows a similar pattern, with relatively stable concentrations prior to about 1800 followed by a rapid increase (Ehhalt et al., 2001). Roughly, 20% of CH4 emissions 

are from gas released in the extraction and transportation 

of fossil fuels; the rest is from biological sources including 

expanding rice and cattle production (Prinn, 2004). Such 

large increases in atmospheric carbon over such a short 

period of time relative to historical variations, together with 

patterns of human activity that will likely continue into the 

twenty-first century, such as trends in fossil-fuel use and 

Figure 1.1 The Earth’s carbon cycle. Carbon cycles 

through pools or reservoirs of carbon on land, in the ocean, 

and in sedimentary rock formations over daily, seasonal, 

annual, millennial, and geological time scales. See the accompanying text box. Figure adapted from http://www.esd.

ornl.gov/iab/iab2-2.htm.

BOX 1.1: The Earth’s Carbon Cycle

The burning of fossil fuels transfers carbon from 

geological reservoirs of coal, oil, and gas and releases 

carbon dioxide (CO2) into the atmosphere. Tropical 

deforestation and other changes in land use also release 

carbon to the atmosphere as vegetation is burned 

and dead material decays. Photosynthesis transfers 

CO2 from the atmosphere and the carbon is stored 

in wood and other plant tissues. The respiration that 

accompanies plant metabolism transfers some of the 

carbon back to the atmosphere as CO2. When plants 

die, their decay also releases CO2 to the atmosphere. 

A fraction of the dead organic material is resistant to 

decay and that carbon accumulates in the soil. Chemical 

and physical processes are responsible for the exchange 

of CO2 across the sea surface. The small difference 

between the flux into and out of the surface ocean is 

responsible for net uptake of CO2 by the ocean. Phytoplankton, small plants floating in the surface ocean, 

use carbon dissolved in the water to build tissue and 

calcium carbonate shells. When they die, they begin 

to sink and decay. As they decay, most of the carbon 

is redissolved into the surface water, but a fraction 

sinks into the deeper ocean, the so-called “biological pump”, eventually reaching the ocean sediments. 

Currents within the ocean also circulate carbon from 

surface waters to the deep ocean and back. Carbon 

accumulated in soils and ocean sediments millions of 

years of ago was slowly transformed to produce the 

geological reservoirs of today’s fossil fuels. For a more 

detailed, quantitative description, see Prentice et al. 

(2001), Houghton (2003), Sundquist and Visser (2003), 

Sabine et al. (2004), and Chapter 2 of this report.
17

The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

tropical deforestation, raises concerns about imbalances in 

the carbon cycle and their implications.

1.2 The Carbon Cycle and Climate

Change

Most of the carbon in the Earth’s atmosphere is in the form 

of CO2 and CH4. Both CO2 and CH4 are important “greenhouse gases.” Along with water vapor and other “radiatively 

active” gases in the atmosphere, they absorb heat radiated 

from the Earth’s surface, heat that would otherwise be lost 

into space. As a result, these gases help to warm the Earth’s 

atmosphere. Rising concentrations of atmospheric CO2 and 

other greenhouse gases can alter the Earth’s radiant energy 

balance. The Earth’s energy budget determines the global 

circulation of heat and water through the atmosphere and 

the patterns of temperature and precipitation we experience 

as weather and climate. Thus the human disturbance of the 

Earth’s global carbon cycle during the industrial era and the 

resulting imbalance in the Earth’s carbon budget and buildup 

of atmospheric CO2 have consequences for climate and 

climate change. According to the IPCC, CO2 is the largest 

single forcing agent of climate change (IPCC, 2001)1. 

In addition to the relationship between climate change and 

atmospheric CO2 as a greenhouse gas, research is beginning 

to reveal the feedbacks between a changing carbon cycle 

and changing climate, and the associated implications for 

future climate change. Simulations with climate models that 

include an interactive global carbon cycle indicate a positive feedback between climate change and atmospheric CO2

concentrations. The magnitude of the feedback varies considerably among models; but in all cases, future atmospheric 

CO2 concentrations are higher and temperature increases are 

larger in the coupled climate-carbon cycle simulations than 

in simulations without the coupling and feedback between 

climate change and changes in the carbon cycle (Friedlingstein et al., 2006). The research is in its early stages, but 

8 of the 11 models, in a recent comparison among models 

(Friedlingstein et al., 2006), attributed most of the feedback 

to changes in land carbon, with the majority locating those 

changes in the tropics. Differences among models in almost 

every aspect of plant and soil response to climate were 

responsible for the differences in model results, including 

1

 Methane is also an important contributor (IPCC, 2001). However, 

CH4 and other non-CO2 carbon gases are not typically included in 

global carbon budgets because their sources and sinks are not well 

understood (Sabine et al., 2004). For this reason, and to manage 

scope and focus, we too follow that convention and this report is 

limited primarily to the carbon cycle and carbon budget of North 

America as it influences and is influenced by atmospheric CO2. 

Methane is discussed in individual chapters where appropriate, but 

the report makes no effort to provide a comprehensive synthesis and 

assessment of CH4 as part of the North American carbon budget. 

Similarly we provide no comprehensive treatment of black carbon, 

isoprene, or other volatile organic carbon compounds that represent 

a small fraction of global or continental carbon budgets.

plant growth in response to atmospheric CO2 concentrations 

and climate and accelerated decomposition of dead organic 

matter in response to warmer temperatures.

Changes in temperature, precipitation, and other climate 

variables also contribute to year-to-year changes in carbon 

cycling. Nearly all of the biological, chemical, and physical processes responsible for exchange of carbon between 

atmosphere, land, and ocean are influenced to some degree 

by climate variables, and both ocean-atmosphere and landatmosphere exchanges (sources and sinks) show year-to-year 

variation attributable to variability in climate (Prentice et 

al., 2001; Schaefer et al., 2002; Houghton, 2003; Sabine et 

al., 2004; Greenblatt and Sarmiento, 2004; Chapter 2 this 

report). This variability is believed to be responsible for the 

large year-to-year differences in the accumulation of CO2 in 

the atmosphere; annual changes differ by as much as 3000 

to 4000 million metric 

tons of carbon (Mt C) 

per year (Prentice et 

al., 2001; Houghton, 

2003). Both land and 

ocean show changes, 

for example, in apparent response to climate 

conditions linked to El 

Niño events, although 

the variability in the net 

land-atmosphere exchange is larger (Prentice et al., 2001; 

Houghton, 2003; Sabine et al., 2004). Figure 1.2 illustrates 

this variability, showing for North America year-to-year 

variation in satellite observations of the annual net transfer 

of carbon from the atmosphere to plants. Variability of this 

sort, in both land and ocean, contributes uncertainty to carbon budgeting and may appear as “noise” when attempting 

to detect “signals” of longer-term climate relevant trends 

(Sabine et al., 2004) or, eventually, signals of effective 

carbon management.

Many of the currently proposed options to prevent, minimize, or forestall future climate change will likely require 

management of the carbon cycle and concentrations of CO2

in the atmosphere. That management includes both reducing sources, such as the combustion of fossil fuels, and 

enhancing sinks, such as uptake and storage (sequestration) 

in vegetation and soils. In either case, the formulation of options by decision makers and successful management of the 

Earth’s carbon budget requires solid scientific understanding 

of the carbon cycle and the “ability to account for all carbon 

stocks, fluxes, and changes and to distinguish the effects 

of human actions from those of natural system variability” 

(CCSP, 2003).

The human disturbance of the 

Earth’s global carbon cycle during 

the industrial era and the resulting 

imbalance in the Earth’s carbon 

budget and buildup of atmospheric 

CO2 have consequences for 

climate and climate change. 
The U.S. Climate Change Science Program Chapter 1

18 

So, why care about the carbon cycle? In short, because people care about the potential consequences of global climate 

change, they also, necessarily, care about the carbon cycle 

and the balance between carbon sources and sinks, natural 

and human, which determine the budget imbalance and accumulation of carbon in the atmosphere as CO2.

1.3 Other Implications of an

Imbalance in the Carbon Budget

The consequences of an unbalanced carbon budget with 

carbon accumulating in the atmosphere as CO2 and CH4

are not completely understood, but it is known that they 

extend beyond climate change alone. Experimental studies, for example, show that for many plant species, rates of 

photosynthesis often increase in response to elevated concentrations of CO2 thus potentially increasing plant growth 

and even agricultural crop yields in the future. There is, 

however, considerable uncertainty about whether such “CO2

fertilization” will continue into the future with prolonged 

exposure to elevated CO2; and, of course, its potential beneficial effects on plants presume climatic conditions that are 

also favorable to plant and crop growth.

It is also increasingly evident that atmospheric CO2 concentrations are responsible for increased acidity of the surface 

ocean (Caldeira and Wickett, 2003), with potentially dire 

future consequences for corals and other marine organisms 

that build their skeletons and shells from calcium carbonate. Ocean acidification is a powerful reason, in addition 

to climate change, to care about the carbon cycle and the 

accumulation of CO2 in the atmosphere (Orr et al., 2005).

1.4 Why the Carbon Budget of

North America?

The continent of North America has been identified as both 

a significant source and a significant sink of atmospheric 

CO2 (IPCC, 2001; Pacala et al., 2001; Goodale et al., 2002; 

Gurney et al., 2002; EIA, 2005). More than a quarter (27%) 

of global carbon emissions, from the combination of fossilfuel burning and cement manufacturing, are attributable 

to North America (United States, Canada, and Mexico) 

(Marland et al., 2003). North American plants remove CO2

from the atmosphere and store it as carbon in plant biomass 

and soil organic matter, mitigating to some degree the human-caused (anthropogenic) sources. The magnitude of 

the “North American sink” has been previously estimated 

at anywhere from less than 100 Mt C per year to slightly 

more than 2000 Mt C per year (Turner et al., 1995; Fan et 

al., 1998), with a value near 350 to 750 Mt C per year most 

likely (Houghton et al., 1999; Goodale et al., 2002; Gurney 

et al., 2002). The North American sink 

is thus, a substantial, if highly uncertain, fraction, from 15% to essentially 

100%, of the extra-tropical Northern 

Hemisphere terrestrial sink estimated 

to be in the range of 600 to 2300 Mt 

C per year during the 1980s (Prentice 

et al., 2001). It is also a reasonably 

large fraction (perhaps near 30%) of 

the global terrestrial sink estimated at 

1900 Mt C per year for the 1980s (but 

with a range of uncertainty from a large 

sink of 3800 Mt C per year to a small 

source of 300 Mt C per year (Prentice 

et al., 2001). The global terrestrial sink 

absorbs approximately one quarter of 

the carbon added to the atmosphere by 

human activities, but with uncertainties 

linked to the uncertainties in the size of 

that sink. Global atmospheric carbon 

concentrations would be substantially 

higher than they are without the partially mitigating influence of the sink 

in North America. However, estimates 

of that sink vary widely, and it needs to 

be better quantified.

Figure 1.2 Variability in net primary production (NPP) for North America from 2000-2005. 

Values are the deviation from 6-year average annual NPP estimated by the MOD17 1-km resolution data product from the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the 

National Aeronautics and Space Administration (NASA) Terra and Aqua satellites. Blue indicates 

regions where that year’s NPP, the net carbon fixed by vegetation from the atmosphere, was 

greater than average; red indicates where annual NPP was less than the average. See Running 

et al. (2004) for further information on the MODIS NPP product. Figure courtesy of Dr. Steven 

W. Running, University of Montana.
19

The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

Some mechanisms that might be responsible for the North 

American terrestrial sink are reasonably well known. These 

mechanisms include, but are not limited to, the regrowth 

of forests following abandonment of agriculture, changes 

in fire and other disturbance regimes, historical climate 

change, and fertilization of ecosystem production by nitrogen deposition and elevated atmospheric CO2 (Dilling et 

al., 2003; Foley et al., 2004). Recent studies have indicated 

that some of these processes are likely more important than 

others for the current North American carbon sink, with 

regrowth of forests on former agricultural land generally 

considered to be a major contributor, and with, perhaps, 

a significant contribution from enhanced plant growth in 

response to higher concentrations of atmospheric CO2 (CO2 

fertilization) (Caspersen et al., 2000; Schimel et al., 2000; 

Houghton, 2002). But significant uncertainties remain 

(Caspersen et al., 2000; Schimel et al., 2000; Houghton, 

2002), with some arguing that even the experimental evidence for CO2 fertilization is equivocal at the larger spatial 

scales necessary for a significant terrestrial sink (e.g., Nowak 

et al., 2004; Friedlingstein et al., 2006). The future of the 

current North American terrestrial sink is highly uncertain, 

and it depends on which mechanisms are the dominant drivers now and in the future.

Estimates of coastal carbon cycling and input of carbon from 

the land are equally uncertain (Liu et al., 2000). Coastal 

processes are also difficult to parameterize in global carbon 

cycle models, which are often used to derive best-guess estimates for regional carbon budgets (Liu et al., 2000). It is 

very important to quantify carbon fluxes in coastal margins 

of the area adjacent to the North American continent, lest 

regional budgets of carbon on land be misattributed.

North America is a major player in the global carbon cycle, 

in terms of both sources and sinks. Accordingly, understanding the carbon budget of North America is a necessary 

part of understanding the global carbon cycle. Such understanding is helpful 

for successful carbon 

management strategies 

to mitigate fossil-fuel 

emissions or stabilize 

concentrations of greenhouse gases in the atmosphere. Moreover, a large North 

American terrestrial sink generated by “natural” processes 

is an ecosystem service that would be valued at billions 

of dollars if purchased or realized through direct human 

economic and technological intervention. Its existence will 

likely influence carbon-management decision making, and 

it is important that its magnitude and its dynamics be well 

understood (Kirschbaum and Cowie, 2004; Canadell et al., 

2007).

It is particularly important to understand the likely future 

behavior of carbon in North America, including terrestrial 

and oceanic sources and sinks. Decisions made about future carbon management with expectations of the future 

behavior of the carbon cycle that proved to be significantly 

in error, could be costly. For example, future climate-carbon 

feedbacks could change the strength of terrestrial sinks and 

put further pressure on emission reductions to achieve atmospheric stabilization targets (Jones et al., 2006; Canadell 

et al., 2007). The future cannot be known, 

but understanding the 

current and historical 

carbon cycle will increase confidence in 

projections for appropriate consideration by 

decision makers.

1.5 CARBON CYCLE SCIENCE IN 

SUPPORT OF CARBON MANAGEMENT 

DECISIONS

Beyond understanding the science of the North 

American carbon budget and its drivers, increasing attention is now being given to deliberate 

management strategies for carbon (DOE, 1997, 

Hoffert et al., 2002; Dilling et al., 2003). Carbon 

management is now being considered at a variety 

of scales in North America. There are tremendous opportunities for carbon cycle science to 

improve decision making in this arena, whether 

in reducing carbon emissions from the use of fossil fuels, or in managing terrestrial carbon sinks. 

Many decisions in government, business, and everyday life are connected with the carbon cycle. 

They can relate to driving forces behind changes 

in the carbon cycle (such as consumption of fossil 

More than a quarter (27%) of 

global carbon emissions are 

attributable to North America.

North America is a major player 

in the global carbon cycle, in 

terms of both sources and sinks.
The U.S. Climate Change Science Program Chapter 1

20 

fuels) and strategies for managing them, and/or impacts of 

changes in the carbon cycle (such as climate change or ocean 

acidification) and responses to reduce their severity. Carbon 

cycle science can help to inform these decisions by providing timely and reliable information about facts, processes, 

relationships, and levels of confidence.

In seeking ways to use scientific information more effectively in decision making, we must pay particular attention to the 

importance of developing constructive scientist–stakeholder 

interactions. Studies of these interactions all indicate that 

neither scientific research nor assessments can be assumed 

to be relevant to the needs of decision makers if conducted 

in isolation from the context of those users’ needs (Cash and 

Clark, 2001; Cash et al., 2003; Dilling et al., 2003; Parson, 

2003). Carbon cycle science’s support of decision making 

is more likely to be effective if the science connected with 

communication structures is considered by both scientists 

and users to be legitimate and credible. Well-designed 

scientific assessments can be one of these effective communication media.

The climate and carbon research community of North 

America, and a diverse range of stakeholders, recognize the 

need for an integrated synthesis and assessment focused on 

North America to (a) summarize what is known and what 

is known to be unknown, documenting the maturity as 

well as the uncertainty of this knowledge; (b) convey this 

information to scientists and to the larger community; and 

(c) ensure that our studies are addressing the questions of 

concern to society and decision-making communities. As 

the most comprehensive synthesis to date of carbon cycle 

knowledge and trends for North America, incorporating 

stakeholder interactions throughout its production2

, this 

report, the First State of the Carbon Cycle Report (SOCCR), 

focused on The North American Carbon Budget and Implications for the Global Carbon Cycle is intended as a step 

in that direction.

2

 A discussion of stakeholder participation in the production of this 

report can be found in the Preface of this report.
The Carbon Cycle of North America in a 

Global Context

CHAPTER

2

21

Coordinating Lead Author: Christopher B. Field, Carnegie Inst.

Lead Authors: Jorge Sarmiento, Princeton Univ.; Burke Hales, Oreg. 

State Univ.

The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

KEY FINDINGS

Human activity over the last two centuries, including combustion of fossil fuel and clearing of forests, has 

led to a dramatic increase in the concentration of atmospheric carbon dioxide. Global atmospheric carbon 

dioxide concentrations have risen by 31% since 1850 and are now higher than they have been for at least 

420,000 years.

North America is responsible for approximately 25% of the emissions produced globally in 2004 by fossil-fuel 

combustion, with the United States accounting for 86% of the North American total.

Human-caused emissions (a carbon source) dominate the carbon budget of North America. Largely unmanaged, unintentional processes capture a fraction of this carbon in plants, soils, and other sinks. Currently, these 

sinks (970 ± 360 million metric tons of carbon (Mt C) per year, based on atmospheric inversion studies, 

or 530 ± 265 Mt C per year, based on the inventories used in this report) capture approximately 30-50% 

of the North American emissions, 7-13% 

of global fossil-fuel emissions, and 30-50% 

of the global terrestrial sink inferred from 

global budget analyses and atmospheric inversions.

While the future trajectory of carbon sinks 

in North America is uncertain (substantial 

climate change could convert current sinks 

into sources), it is clear that the carbon 

cycle of the next few decades will be dominated by the large sources from fossil-fuel 

emissions.

Because North American carbon emissions 

are at least a quarter of global emissions, 

a reduction in North American emissions 

would have global consequences.

•

•

•

•

•
The U.S. Climate Change Science Program Chapter 2

22 

2.1 THE GLOBAL CARBON CYCLE

The modern global carbon cycle is a collection of many different kinds of processes, with diverse drivers and dynamics, 

that transfer carbon among major pools in rocks, fossil fuels, 

the atmosphere, the oceans, and plants and soils on land (Sabine et al., 2004b) (Figure 2.1). During the last two centuries, 

human actions, especially the combustion of fossil fuel and 

the clearing of forests, have altered the global carbon cycle 

in important ways. Specifically, these actions have led to 

a rapid, dramatic increase in the concentration of carbon 

dioxide (CO2) in the atmosphere (Figure 2.2), changing the 

radiation balance of the Earth (Hansen et al., 2005), and very 

likely causing much of the warming observed over the last 50 

years (Hegerl et al., 2007). The cause of the recent increase 

in atmospheric CO2 is confirmed beyond a reasonable doubt 

(Prentice, 2001). This does not imply, however, that the other 

components of the carbon cycle have remained unchanged 

during this period. In fact, the background, or unmanaged 

parts, of the carbon cycle have changed dramatically over 

the past two centuries. The consequence of these changes 

is that only about 40% ± 15%1 of the CO2 emitted to the 

atmosphere from fossil-fuel combustion and forest clearing 

has remained there (Sabine et al., 2004b). In essence, human 

actions have received a large subsidy from the unmanaged 

parts of the carbon cycle. This subsidy has sequestered, or 

hidden from the atmosphere, approximately 279 ± 160 billion 

tons (gigatons [Gt]) of carbon2.

1

 Most of the uncertainty in this number is due to the approximately 

100% uncertainty in carbon lost from forest clearing. This includes 

uncertainties in areas deforested, in conditions at the time of 

deforestation, and in the fate following deforestation (Houghton, 

1999). Except where otherwise noted, the uncertainty bounds on 

the numbers in this chapter are expert assessments by the authors of 

the cited literature, based on synthesizing a wide range of empirical 

and modeling studies. The details of the approaches to assessing 

uncertainty are discussed in the literature cited. 2

 Unless specified otherwise, throughout this chapter, the pools and 

fluxes in the carbon cycle are presented in Gt C [1 Gt = 1 billion tons 

or 1 × 1015 g]. The mass of CO2 is greater than the mass of carbon by 

the ratio of their molecular weights, 44/12 or 3.67 times; 1 km3

 of coal 

contains approximately 1 Gt C.

Figure 2.1 Schematic representation of the components of the global carbon cycle. The three panels show (a) the overall 

cycle, (b) the details of the ocean cycle, and (c) the details of the land cycle. For all panels, carbon stocks are in brackets, 

and fluxes have no brackets. Stocks and fluxes prior to human-influence are in black. Human-induced perturbations are 

in red. For stocks, the human-induced perturbations are the cumulative total through 2003. H uman-caused fluxes are 

means for the 1990s (the most recent available data for some fluxes). Redrawn from Sabine et al. (2004b) with updates 

through 2003 as discussed in the text.
23

The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

The recent subsidy, or sequestration, of carbon by the unmanaged parts of the carbon cycle, makes them critical for an 

accurate understanding of climate change. Future increases 

in carbon uptake in the unmanaged parts of the cycle could 

moderate the risks from climate change, while decreases or 

transitions from uptake to release could amplify the risks, 

perhaps dramatically.

In addition to its role in the climate, the carbon cycle intersects with a number of critical Earth system processes. 

Because plant growth is essentially the removal of CO2 from 

the air through photosynthesis, agriculture and forestry 

contribute important fluxes. Wildfire is a major release 

of carbon from plants and soils to the atmosphere (Sabine 

et al., 2004b). The increasing concentration of CO2 in the 

atmosphere has already made the world’s oceans more acid 

(Caldeira and Wickett, 2003). Future changes could dramatically alter the composition of ocean ecosystems (Feely et 

al., 2004; Orr et al., 2005).

2.1.1 The Unmanaged Global Carbon Cycle

The modern background, or unmanaged, carbon cycle 

includes the processes that occur in the absence of human 

actions. However, these processes are currently so altered by 

human influences on the carbon cycle that it is not appropriate to label them natural. This background part of the carbon 

cycle is dominated by two pairs of gigantic fluxes with annual uptake and release that are close to balanced (Sabine 

et al., 2004b) (Figure 2.1). The first of these comprises the 

terrestrial carbon cycle: plant growth on 

land annually fixes about 57 ± 9 Gt of atmospheric carbon, approximately ten times 

the annual emission from fossil-fuel combustion, into carbohydrates. Respiration by 

land plants, animals, and microorganisms, 

which provides the energy for growth, activity, and reproduction, returns a slightly 

smaller amount to the atmosphere. Part of 

the difference between photosynthesis and 

respiration is burned in wildfires, and part 

is stored as plant material or soil organic 

carbon. The second comprises the ocean 

carbon cycle: about 92 Gt of atmospheric 

carbon dissolves annually in the oceans, 

and about 90 Gt per year moves from the 

oceans to the atmosphere (While the gross 

fluxes have a substantial uncertainty, the 

difference is known to within ± 0.2 Gt)3

. 

These air-sea fluxes are driven by cycling 

within the oceans that governs exchanges 

between pools of dissolved CO2, bicarbonate (HCO3), carbonate (CO3), organic matter, and calcium carbonate (CaCO3).

Before the beginning of the 

industrial revolution, carbon 

uptake and release through these 

two pairs of large fluxes were 

almost balanced, with carbon 

uptake on land of approximately 

0.45 ± 0.18 Gt C per year transferred to the oceans by rivers 

and released from the oceans 

to the atmosphere (Jacobson et 

al., 2007). As a consequence, 

the level of CO2 in the atmosphere varied by less than 25 

parts per million (ppm) in the 10,000 years prior to 1850 

(Joos and Prentice, 2004). However, atmospheric CO2 was 

not always so stable. During the preceding 420,000 years, 

atmospheric CO2 was 180-200 ppm during the ice ages 

and approximately 275 ppm during interglacial periods 

(Petit et al., 1999). The lower ice-age concentrations in the 

atmosphere most likely reflect a transfer of carbon from 

the atmosphere to the oceans, possibly driven by changes 

in ocean circulation and sea-ice cover (Sigman and Boyle, 

2000; Keeling and Stephens, 2001). Enhanced biological 

activity in the oceans, stimulated by increased delivery of 

iron-rich terrestrial dust, may have also contributed to this 

increased uptake (Martin, 1990).

3

 This uncertainty is one-half the range among the subset of the 

19 Ocean Carbon-Cycle Model Intercomparison Project (OCMIP) 

models that are consistent with the available 14C and CFC-11 data 

(Matsumoto et al., 2004).

The increasing 

concentration of CO2

in the atmosphere has 

already made the world’s 

oceans more acid. Future 

changes could dramatically 

alter the composition 

of ocean ecosystems.

Figure 2.2 Atmospheric CO2 concentration from 1750 to 2005. The 

data prior to 1957 (red circles) are from the Siple ice core (Friedli et 

al., 1986). The data since 1957 (blue circles) are from continuous atmospheric sampling at the Mauna Loa Observatory (Hawaii) (Keeling et al., 

1976; Thoning et al., 1989) (with updates available at http://cdiac.ornl.

gov/trends/co2/sio-mlo.htm).
The U.S. Climate Change Science Program Chapter 2

24 

In the distant past, the global 

carbon cycle was out of balance in a different way. Fossil fuels are the product of 

prehistorically stored plant 

growth, especially 354 to 

290 million years ago in the 

Carboniferous period. During this time, luxuriant plant 

growth and geological activity combined to bury a small 

fraction of each year’s growth. Over millions of years, this 

gradual burial led to the accumulation of vast stocks of fossil fuel. The total accumulation of fossil fuels is uncertain, 

but probably in the range of 6000 ± 3000 Gt (Sabine et al., 

2004b). This burial of carbon also led to a near doubling of 

atmospheric oxygen (Falkowski et al., 2005).

2.1.2 Human-induced Perturbations 

to the Carbon Cycle

Since the beginning of the industrial revolution, there has 

been a massive release of carbon from fossil-fuel combustion and deforestation. Cumulative carbon emissions from 

fossil-fuel combustion, natural gas flaring, and cement 

manufacturing from 1751 through 2003 are 304 ± 30 Gt 

(Marland and Rotty, 1984; Andres et al., 1999)4

. Land-use 

change from 1850 to 2003, mostly from forest clearing, 

added another 162±160 Gt (DeFries et al., 1999; Houghton, 

1999)5. The rate of fossil-fuel consumption in any recent year 

would have required, for its production, more than 400 times 

the current global primary production (total plant growth) 

of the land and oceans combined (Dukes, 2003). This has 

led to a rapid increase in the concentration of CO2 in the 

atmosphere since the mid-1800s, with atmospheric CO2

rising by 31% (i.e., from 287 ppm to 375 ppm in 2003; the 

increase from the mid-1700s was 35%).

In 2004, the three major countries of North America (Canada, 

Mexico, and the United States) together accounted for carbon 

emissions from fossil-fuel combustion of approximately 

1.88 ± 0.2 Gt C, (about 25%) of the global total6. The United 

States, the world’s largest emitter of CO2, was responsible 

for 86% of the North American total. Per capita emissions in 

2004 were 5.5 ± 0.5 metric tons in the United States, 4.9 ± 0.5 

metric tons in Canada, and 1.0 ± 0.1 metric tons in Mexico. 

Per capita emissions in the United States were nearly 5 

times the world average, 2.5 times the per capita emissions 

for Western Europe, and more than 8 times the average for 

Asia and Oceania (DOE EIA, 2006). The world’s largest 

4

 Updates through 2003 available at http://cdiac.ornl.gov/trends/mis/

tre_glob.html.

5

 Updates through 2000 online at http://cdiac.ornl.gov/trends/landuse/

houghton/houghton.html. The total through 2003 was extrapolated 

based on the assumption that the annual fluxes in 2001-2003 were the 

same as in 2000.

6

 Uncertainties in national and per capita emissions are based on data 

reported by individual countries.

countries, China and India, 

have total carbon emissions 

from fossil-fuel 

c o m b u s t i o n 

and the flaring 

of natural gas 

that are growing rapidly. The 

2004 total for 

China was 80% 

of that in the United States, and the total for India was 18% 

of that in the United States. Per capita emissions for China 

and India in 2004 were 18% and 5%, respectively, of the 

United States rate (DOE EIA, 2006).

2.2 ASSESSING GLOBAL AND REGIONAL 

CARBON BUDGETS

Changes in the carbon content of the oceans and plants 

and soils on land can be evaluated with at least five different approaches—flux measurements, inventories, inverse 

estimates based on atmospheric CO2, process models, and 

calculation as a residual. The first method, direct measurement of carbon flux, is well developed over land for 

measurements over the spatial scale of up to 1 km2, using 

the eddy flux technique (Wofsy et al., 1993; Baldocchi and 

Valentini, 2004). Although eddy flux measurements are now 

collected at more than 100 networked sites, spatial scaling 

presents formidable challenges due to spatial heterogeneity. 

To date, estimates of continental-scale fluxes based on eddy 

flux must be regarded as preliminary. Over the oceans, eddy 

flux is possible (McGillis, 2001), but estimates based on 

air-sea CO2 concentration difference are more widely used 

(Takahashi et al., 1997). 

Inventories, based on measuring trees on land (Birdsey and 

Heath, 1995) or carbon in ocean-water samples (Takahashi et 

al., 2002; Sabine et al., 2004a) can provide useful constraints 

on changes in the size of carbon pools, though their utility 

for quantifying short-term changes is limited. Inventories 

were the foundation of the recent conclusion that 118 ± 19 Gt 

of human-caused carbon entered the oceans through 1994 

(Sabine et al., 2004a) and that forests in the mid latitudes 

of the Northern Hemisphere absorbed and stored 0.6 to 0.7 

Gt C per year in the 1990s (Goodale et al., 2002). Changes 

in the atmospheric inventory of oxygen (O2) (Keeling et al., 

1996) and carbon-13 (13C) in CO2 (Siegenthaler and Oeschger, 1987) provide a basis for partitioning CO2 flux into land 

and ocean components.

Process models and inverse estimates based on atmospheric 

CO2 (or CO2 in combination with 13C or O2) also provide usePer capita emissions in the 

United States were nearly 5 

times the world average, 2.5 

times the per capita emissions 

for Western Europe, and 

more than 8 times the 

average for Asia and Oceania. 
25

The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

ful constraints on carbon stocks and fluxes. Process models 

build from understanding the underlying principles of atmosphere/ocean or atmosphere/ecosystem carbon exchange to 

make estimates over scales of space and time that are relevant to the global carbon cycle. For the oceans, calibration 

against observations with tracers (e.g., carbon-14 [14C] and 

chlorofluorocarbons) (Broecker et al., 1980) tends to nudge 

a wide range of models toward similar results. Sophisticated 

models with detailed treatment of the ocean circulation, 

chemistry, and biology all reach about the same estimate 

for the current ocean carbon sink, 1.5 to 1.8 Gt C per year 

(Greenblatt and Sarmiento, 2004) and are in quantitative 

agreement with data-inventory approaches. Models of the 

land carbon cycle take a variety of approaches. They differ 

substantially in the data used as constraints, in the processes 

simulated, and in the level of detail (Cramer et al., 1999; 

Cramer et al., 2001). Models that take advantage of satellite 

data have the potential for comprehensive coverage at high 

spatial resolution (Running et al., 2004), but only over the 

time domain with available satellite data. Flux components 

related to human activities, deforestation, for example, have 

been modeled based on historical land use (Houghton et al., 

1999). At present, model estimates are uncertain enough that 

they are often used most effectively in concert with other 

kinds of estimates (e.g., Peylin et al., 2005).

Inverse estimates based on atmospheric gases (CO2, 13C in 

CO2, or O2) infer surface fluxes based on the spatial and 

temporal pattern of atmospheric gas concentration, coupled 

with information on atmospheric transport (Newsam and 

Enting, 1988). The atmospheric concentration of CO2 is now 

measured with high precision at approximately 100 sites 

worldwide, with many of the stations added in the last decade 

(Masarie and Tans, 1995). The 13C in CO2 and high-precision 

O2 are measured at far fewer sites. The basic approach is a 

linear Bayesian inversion (Tarantola, 1987; Enting, 2002), 

with many variations in the time scale of the analysis, the 

number of regions used, and the transport model. Inversions 

have more power to resolve year-to-year differences than 

mean fluxes (Rodenbeck et al., 2003; Baker et al., 2006). 

Limitations in the accuracy of atmospheric inversions come 

from the limited density of concentration measurements 

(especially in the tropics), uncertainty in the transport, and 

errors in the inversion process (Baker et al., 2006). Recent 

studies that use a number of sets of CO2 monitoring stations 

(Rodenbeck et al., 2003), models (Gurney et al., 2003; Law et 

al., 2003; Gurney et al., 2004; Baker et al., 2006), temporal 

scales, and spatial regions (Pacala et al., 2001), highlight 

the sources of the uncertainties and appropriate steps for 

managing them.

A final approach to assessing large-scale CO2 fluxes is 

solving as a residual. At the global scale, the net flux to or 

from the land is often calculated as the residual left after 

accounting for fossil-fuel emissions, atmospheric increase, 

and ocean uptake (Post et al., 1990). Increasingly, the need to 

treat the land as a residual is receding, as the other methods 

improve. Still, the existence of constraints at the level of 

the overall budget provides an important connection with 

reality.

2.3 RECENT DYNAMICS OF THE 

UNMANAGED CARBON CYCLE

Of the approximately 466 ± 160 Gt C added to the atmosphere by human actions through 2003, only about 187 ± 5 

Gt remain. The “missing carbon” must be stored, at least 

temporarily, in the oceans and in ecosystems on land. Based 

on a recent ocean inventory, 118 ± 19 Gt of the missing 

carbon was in the oceans, as of 1994 (Sabine et al., 2004a). 

Extending this calculation, based on recent sinks (Takahashi 

et al., 2002; Gloor et al., 2003; Gurney et al., 2003; Matear 

and McNeil, 2003; Matsumoto et al., 2004), leads to an 

estimate of 137 ± 24 Gt C through 2003. This leaves about 

142 ± 160 Gt that must be stored on land (with most of the 

uncertainty due to the uncertainty in emissions from land 

use). Identifying the processes responsible for the uptake 

on land, their spatial distribution, and their likely future 

trajectory has been one of the major goals of carbon cycle 

science over the last decade.

Much of the recent research on the global carbon cycle has 

focused on annual fluxes and their spatial and temporal 

variation. The temporal and spatial patterns of carbon 

flux provide a pathway to understanding the underlying 

mechanisms. Based on several different approaches, carbon 
The U.S. Climate Change Science Program Chapter 2

26 

uptake by the oceans averaged 1.7 ± 0.2 Gt C per year7 for 

the period from 1992-1996 (Takahashi et al., 2002; Gloor 

et al., 2003; Gurney et al., 2003; Matear and McNeil, 2003; 

Matsumoto et al., 2004). The total human-caused flux is this 

amount, plus 0.45 Gt per year of preindustrial outgasing, 

for a total of 2.2 ± 0.4 Gt per year. This rate represents an 

integral over high-latitude areas, which are gaining carbon, 

and the tropics, which are losing carbon (Takahashi et al., 

2002; Gurney et al., 2003; Gurney et al., 2004; Jacobson 

et al., 2007). Interannual variability in the ocean sink for 

CO2, though substantial (Greenblatt and Sarmiento, 2004), 

is much smaller than interannual variability on the land 

(Baker et al., 2006).

In the 1990s, carbon releases from land-use change were 

more than balanced by ecosystem uptake, leading to a net 

sink on land (without accounting for fossil-fuel emissions) 

of 1.1 ± 1.5 Gt C per year (Schimel et al., 2001; Sabine et al., 

2004b). The dominant sources of recent interannual variation in the net land flux were El 

Niño and the eruption of Mount 

Pinatubo in 1991 (Bousquet 

et al., 2000; Rodenbeck et al., 

2003; Baker et al., 2006), with 

most of the year-to-year variation in the tropics (Figure 2.3). 

Fire likely plays a large role in 

this variability (van der Werf et 

al., 2004).

7

 This uncertainty is one-half the range among the subset of the 19 

Ocean Carbon-Cycle Model Intercomparison Project (OCMIP) models 

that are consistent with the available 14C and CFC-11 data (Matsumoto

et al., 2004). 

On a time scale of thousands of years, the ocean will be the 

sink for more than 90% of the carbon released to the atmosphere by human activities (Archer et al., 1998). The rate 

of CO2 uptake by the oceans is, however, limited. Carbon 

dioxide enters the oceans by dissolving in seawater. The rate 

of this process is determined by the concentration difference 

between the atmosphere and the surface waters and by an 

air-sea exchange coefficient related to wave action, wind, 

and turbulence (Le Quéré and Metzl, 2004). Because the 

surface waters represent a small volume with limited capacity to store CO2, the major control on ocean uptake is at the 

level of moving carbon from the surface to intermediate and 

deep waters. Important contributions to this transport come 

from the large-scale circulation of the oceans, especially the 

sinking of cold water in the Southern Ocean and, to a lesser 

extent, the North Atlantic.

On land, numerous processes contribute to carbon storage and carbon loss. Some of these are directly influenced 

through human actions (e.g., the planting of forests, conversion to no-till agriculture, or the burying of organic wastes 

in landfills). The human imprint on others is indirect. This 

category includes ecosystem responses to climate change 

(e.g., warming and changes in precipitation), changes in 

the composition of the atmosphere (e.g., increased CO2 and 

increased tropospheric ozone), and delayed consequences 

of past actions (e.g., regrowth of forests after earlier harvesting). Early analyses of the global carbon budget (e.g., 

Bacastow and Keeling, 1973) typically assigned all of the 

net flux on land to a single mechanism, fertilization of plant 

growth by increased atmospheric CO2. Recent evidence 

emphasizes the diversity of mechanisms.

In the 1990s, carbon 

releases from land-use 

change were more than 

balanced by ecosystem 

uptake, leading to a net sink 

on land (without accounting 

for fossil-fuel emissions).

Figure 2.3 The 13-model mean CO2 flux interannual variability (Gt C per year) for several continents (solid lines) 

and ocean basins (dashed lines). In each panel, the dark inner band is the 1σ intermodel spread, the lighter adjacent 

band is the 1σ estimation uncertainty on interannual variability, and the outer band (visible only for the land) is the 

root sum of squares of the two uncertainty components. (a) North Pacific and North America, (b) Atlantic north of 

15oN and Eurasia, (c) Australasia and Tropical Pacific, (d) Africa, and (e) South America (note the different scales for 

Africa and South America) (Baker et al., 2006).
27

The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

2.3.1 The Carbon Cycle of North America

The land area of North America is a large source of carbon, 

but the residual (without emissions from fossil-fuel combustion) is, by most estimates, currently a sink for carbon. This 

conclusion for the continental scale is based mainly on the 

results of atmospheric inversions. Several studies address the 

carbon balance of particular ecosystem types (e.g., forests 

[Kurz and Apps, 1999; Goodale et al., 2002; Chen et al., 

2003]). Pacala and colleagues (2001) used a combination of 

atmospheric and land-based techniques to estimate that the 

48 contiguous United States are currently a carbon sink of 

0.3 to 0.6 Gt C per year. This estimate and a discussion of 

the processes responsible for recent sinks in North America 

are updated in Chapter 3 of this report. Based on inversions 

using 13 atmospheric transport models, North America was 

a carbon sink of 0.97 ± 0.36 Gt C per year from 1991-2000 

(Baker et al., 2006)8

. Over the area of North America, this 

amounts to an annual carbon sink of 39.6 g C per square 

meter per year, similar to the sink inferred for all northern 

lands (North America, Europe, Boreal Asia, and Temperate Asia) of 32.5 g C per square meter per year (Baker et 

al., 2006).

Very little of the current carbon sink in North America 

is a consequence of deliberate action to absorb and store 

(sequester) carbon. Some is a collateral benefit of steps to 

improve land management, for increasing soil fertility, im8

 This uncertainty is a sample standard deviation across monthly 

output from 13 models.

proving wildlife habitat, 

etc. Much of the current 

sink is unintentional, a 

consequence of historical changes in technologies and preferences in 

agriculture, transportation, and urban design.

2.4 CARBON CYCLE OF THE FUTURE

The future trajectory of carbon sinks in North America is 

very uncertain. Several trends will play a role in determining 

the sign and magnitude of future changes. One important 

controller is the magnitude of future climate changes. If 

the climate warms significantly, much of the United States 

could experience drought-related decreases in plant growth 

and an increase in the risk of wildfire (Bachelet et al., 2003), 

especially if the warming is not associated with substantial 

increases in precipitation. Exactly this pattern—substantial 

warming with little or no change in precipitation—characterizes North America in many of the newer climate 

simulations (Rousteenoja et al., 2003). If North American 

ecosystems are sensitive to elevated CO2, nitrogen deposition, or warming, plant growth could increase (Schimel et 

al., 2000). The empirical literature on CO2 and nitrogen 

deposition is mixed, with some reports of substantial growth 

enhancement (Norby et al., 2005) and others reporting small 

or modest effects (Oren et al., 2001; Shaw et al., 2002; Heath 

et al., 2005).

Overall, the carbon budget of North America is dominated 

by carbon releases from the combustion of fossil fuels. Recent sinks, largely from carbon uptake in plants and soils, 

may approach 50% of the recent fossil-fuel source (Baker 

et al., 2006). Most of this uptake appears to be a rebound, 

as natural and managed ecosystems recover from past 

disturbances. Little evidence supports the idea that these 

ecosystem sinks will increase in the future. Substantial 

climate change could convert current sinks into sources 

(Gruber et al., 2004).

In the future, trends in the North American energy economy 

may intersect with trends in the natural carbon cycle. A 

large-scale investment in afforestation could offset substantial future emissions (Graham, 2003). However, costs 

of this kind of effort 

would include loss of 

the new-forested area 

from its previous 

uses (including grazing or agriculture), 

the energy costs of 

managing the new 

The land area of North America 

is a large source of carbon, but 

the residual (without emissions 

from fossil-fuel combustion) 

is, by most estimates, 

currently a sink for carbon.

Very little of the current carbon sink 

in North America is a consequence 

of deliberate action to absorb 

and store (sequester) carbon.
The U.S. Climate Change Science Program Chapter 2

28 

forests, and any increases in emissions of non-CO2 greenhouse gases from the new forests. Large-scale investments 

in biomass energy (energy produced from vegetative matter) 

would have similar costs but would result in offsetting emissions from fossil-fuel combustion, rather than sequestration 

(Giampietro et al., 1997). The relative costs and benefits of 

investments in afforestation and biomass energy will require 

careful analysis (Kirschbaum, 2003). Investments in other 

energy technologies, including wind and solar, will require 

some land area, but the impacts on the natural carbon cycle 

are unlikely to be significant or widespread (Hoffert et al., 

2002; Pacala and Socolow, 2004).

Like the present, the carbon cycle of North America during 

the next several decades will be dominated by fossil-fuel 

emissions. Deliberate geological sequestration may become 

an increasingly important component of the budget sheet. 

Still, progress in controlling the net release to the atmosphere must be centered on the production and consumption 

of energy rather than the processes of the unmanaged carbon 

cycle. North America has many opportunities to decrease 

emissions (Chapter 4 

this report). Nothing 

about the status of the 

unmanaged carbon 

cycle provides a justification for assuming 

that it can compensate 

for emissions from fossil-fuel combustion. 

Nothing about the status of the 

unmanaged carbon cycle provides 

a justification for assuming that 

it can compensate for emissions 

from fossil-fuel combustion.
The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

CHAPTER

3

29

The North American Carbon Budget Past 

and Present

Coordinating Lead Author: Stephen Pacala, Princeton Univ.

Lead Authors: Richard A. Birdsey, USDA Forest Service; Scott D. 

Bridgham, Univ. Oreg.; Richard T. Conant, Colo. State Univ.; Kenneth 

Davis, The Pa. State Univ.; Burke Hales, Oreg. State Univ.; Richard A. 

Houghton, Woods Hole Research Center; Jennifer C. Jenkins, Univ. 

Vt.; Mark Johnston, Saskatchewan Research Council; Gregg Marland, 

ORNL and Mid Sweden Univ. (Östersund); Keith Paustian, Colo. State 

Univ.

Contributing Authors: John Caspersen, Univ. Toronto; Robert 

Socolow, Princeton Univ.; Richard S. J. Tol, Hamburg Univ.

KEY FINDINGS

Fossil-fuel carbon emissions in the United States, Canada, and Mexico totaled 1856 million tons per year in 

2003 (plus or minus 10%). This represents 27% of global fossil-fuel emissions.

Approximately 30% of North American fossil-fuel emissions are offset by a natural sink estimated at 505 

million tons of carbon per year (plus or minus 50%) for the period including 2003 caused by a variety of 

factors, including forest regrowth, wildfire suppression, and agricultural soil conservation.

In 2003, North America emitted a net of 1351 million tons of carbon per year (plus or minus 25%) to the 

atmosphere.

North American carbon dioxide emissions from fossil fuel have increased at an average rate of approximately 

1% per year for the last 30 years.

Growth in emissions accompanies the historical growth in the industrial economy and Gross Domestic 

Product (GDP) of North America. However, at least in the United States and Canada, the rate of emissions 

growth is less than the growth in GDP, reflecting a decrease in the carbon intensity of these economies.

Fossil-fuel emissions from North America are expected to continue to grow, but more slowly than GDP.

Historically, the plants and soils of the United States and Canada were sources for atmospheric carbon 

dioxide, primarily as a consequence of the expansion of croplands into forests and grasslands. In recent 

decades these regions have shifted from source to sink as forests recover from agricultural abandonment, 

fire suppression is practiced, and logging is reduced, and as a result, these regions are now accumulating 

carbon. In Mexico, emissions of carbon continue to increase due to net deforestation.

The future of the North American carbon sink is highly uncertain. The contribution of recovering forests 

to this sink is likely to decline as these forests mature, but we do not know how much of the sink is due to 

fertilization of the ecosystems by nitrogen in air pollution and by increasing carbon dioxide concentrations 

in the atmosphere, nor do we understand the impact of ozone in the lower atmosphere or how the sink 

will change as the climate changes. Increases in decomposition and wildfire caused by climate change could, 

in principle, convert the sink into a source.

The current magnitude of the North American sink offers the possibility that significant mitigation of fossilfuel emissions could be accomplished by managing forests, rangelands, and croplands to increase the carbon 

stored in them. However, the range of uncertainty in these estimates is at least as large as the estimated 

values themselves.

Current trends towards lower carbon intensity of United States’ and Canadian economies increase the 

likelihood that a portfolio of carbon management technologies will be able to reduce the 1% annual growth 

in fossil-fuel emissions. This same portfolio might be insufficient if carbon emissions were to begin rising at 

the approximately 3% growth rate of GDP.

•

•

•

•

•

•

•

•

•

•
The U.S. Climate Change Science Program Chapter 3

30 

3.1 FOSSIL FUEL

Fossil-fuel carbon emissions in the United States, 

Canada, and Mexico totaled 1856 million metric 

tons of carbon (Mt C) per year in 2003 and have 

increased at an average rate of approximately 

1% per year for the last 30 years (United States 

= 1582, Canada = 164, Mexico = 110 Mt C per 

year, see Figure 3.1)1. This represents 27% of 

global emissions, from a continent with 7% of 

the global population and 25% of global GDP 

(EIA, 2005).

The United States is the world’s largest emitter in 

absolute terms (EIA, 2005). The United States’ 

per capita emissions are also among the largest 

in the world (5.4 t C per year), but the carbon intensity of its economy (emissions per unit GDP) 

at 0.15 metric tons of emitted carbon per dollar of GDP is 

close to the world’s average of 0.14 t C/$ (EIA, 2005). Total 

United States’ emissions have grown at close to the North 

American average rate of about 1.0% per year over the past 

30 years, but the United States’ per capita emissions have 

been roughly constant, while the carbon intensity of the 

United States’ economy has decreased at a rate of about 2% 

per year (see Figures 3.1 to 3.4).

Absolute emissions grew at 1% per year even though per 

capita emissions were roughly constant 

simply because of population growth at an 

average rate of 1%. The constancy of United 

States’ per capita values masks faster than 

1% growth in some sectors (e.g., transportation) that was balanced by slower growth 

in others (e.g., increased manufacturing energy efficiency) (Figures 3.2, 3.3, and 3.4).

Historical decreases in United States’ carbon intensity began early in the twentieth 

century and continue despite the approximate stabilization of per capita emissions 

(Figure 3.2). Why has the United States’ 

carbon intensity declined? This question 

is the subject of extensive literature on 

the so-called structural decomposition of 

the energy system and on the relationship 

between GDP and the environment (i.e., 

Environmental Kuznets Curves; Grossman 

and Krueger, 1995; Selden and Song, 1994). 

See, for example, Greening et al. (1997, 

1998), Casler and Rose (1998), Golove and 

Schipper (1998), Rothman (1998), Suri and 

1

 Uncertainty estimates for the numerical data presented in this 

chapter can be found in Tables 3.1 through 3.3.

Chapman (1998), Greening et al. (1999), Ang and Zhang 

(2000), Greening et al. (2001), Davis et al. (2002), Kahn 

(2003), Greening (2004), Lindmark (2004), Aldy (2005), 

and Lenzen et al. (2006).

Possible causes of the decline in United States’ carbon intensity include: structural changes in the economy, technological improvements in energy efficiency, behavioral changes 

by consumers and producers, the growth of renewable and 

nuclear energy, and the displacement of oil consumption 

Figure 3.2 The historical relationship between United States’ per capita GDP and 

United States’ carbon intensity (green symbols, kg CO2 emitted per 1995 dollar 

of GDP) and per capita carbon emissions (blue symbols, kg CO2 per person). Each 

symbol shows a different year and each of the two time series progresses roughly 

chronologically from left (early) to right (late) and ends in 2002. Source: Maddison 

(2003), Marland et al. (2005). Thus, the blue square farthest to the right shows 

United States’ per capita CO2 emissions in 2002. The square second farthest to 

the right shows per capita emissions in 2001. The third farthest to the right shows 

2000, and so on. Note that per capita emissions have been roughly constant over 

the last 30 years (squares corresponding to per capita GDP greater than approximately $16,000).

Figure 3.1 Historical carbon emissions from fossil fuel in the United States, 

Canada, and Mexico. Data from the U.S. Energy Information Administration 

(EIA, 2005).
31

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

by gas and/or of coal consumption by oil and gas (if we 

produce the same amount of energy from coal, oil, and gas, 

then the emissions from oil are only 80% of those from coal, 

and from gas only 75% of those from oil) (Casler and Rose, 

1998; Ang and Zhang, 2000). The last two items on this 

list are not dominant causes because we observe that both 

primary energy consumption and carbon emissions grew 

at close to 1% per year over the past 30 years (EIA, 2005). 

At least in the United States, there has been no significant 

decarbonization of the energy system during this period. 

However, all of the other items on the list play a significant 

role. The economy has grown at an annual rate of 2.8% over 

the last three decades because of 3.6% growth in the service 

sector; manufacturing grew at only 1.5% per year (Figure 

3.3). Because the service sector has much lower carbon intensity than manufacturing, this faster growth of services 

reduces the country’s carbon intensity. If all of the growth 

in the service sector had been in manufacturing from 1971 

to 2001, then the emissions would have grown at 2% per 

year instead of 1% (here we equate the manufacturing sector 

in Figure 3.3 with the industrial sector in Figure 3.4). So, 

structural change is at least one-half of the answer. Because 

the service sector is likely to continue to grow more rapidly 

than other sectors of the economy, we expect that carbon 

emissions will continue to grow more slowly than GDP. 

This is important because it implies considerable elasticity 

in the relationship between emissions growth and economic 

growth. It also widens the range of policy options that are 

now technologically possible. For example, a portfolio of 

current technologies able to convert the 1% annual growth 

in emissions into a 1% annual decline, might be insufficient 

if carbon emissions were to begin rising at the ~3% growth 

rate of GDP (Pacala and Socolow, 2004).

However, note that industrial emissions are approximately 

constant (Figure 3.4) despite 1.5% economic growth in manufacturing (Figure 3.3). This decrease in carbon intensity 

is caused both by within-sector structural shifts (i.e., from 

heavy to light manufacturing) and by technological improvements (See Part II of this report). 

Emissions from the residential sector are growing at roughly the same rate as the population 

(Figure 3.4; 30-year average of 1.0% per year), 

while emissions from transportation are growing 

faster than the population, but slower than GDP 

(Figure 3.4; 30-year average of 1.4% per year). 

The difference between the 3% growth rate of 

GDP and the 1.6% growth in emissions from 

transportation is not primarily due to technological improvement 

b e c a u s e 

c a r b o n 

emissions 

per mile traveled have 

been level or increasing 

over the period (Chapter 7 this report).

3.2 CARBON SINKS2

Approximately 30% of North American fossil-fuel emissions 

are offset by a natural sink estimated at 505 Mt C per year 

caused by a variety of factors, including forest regrowth, 

fire suppression, and agricultural soil conservation. The 

sink absorbs 489 Mt C per year in the United States and 64 

Mt C per year in Canada. Mexican ecosystems create a net 

source of 48 Mt C per year. Rivers and international trade 

also export a net of 161 Mt C per year that was captured from 

the atmosphere by the continent’s ecosystems, and so North 

America absorbs 666 Mt C per year of atmospheric CO2 (666 

= 505 + 161). Because most of these net exports will return 

2

 See Tables 3.1 and 3.2 for estimates, citations, and uncertainty of 

estimates

We expect that carbon emissions 

will continue to grow more slowly 

than GDP. This is important 

because it widens the range 

of policy options that are now 

technologically possible.

Figure 3.4 Historical United States’ carbon emissions divided 

among the residential, services, manufacturing, and transportation 

sectors. Source: EIA (2005).

Figure 3.3 Historical United States’ GDP divided among the manufacturing, 

services, and agricultural sectors. Source: Mitchell (1998), WRI (2005). 
The U.S. Climate Change Science Program Chapter 3

32 

to the atmosphere elsewhere within 1 year (e.g. carbon in 

exported grain will be eaten, metabolized, and exhaled as 

CO2), the net North American sink is rightly thought of as 

505 Mt C per year even though the continent absorbs a net 

of 666 Mt C per year. Moreover, coastal waters may be small 

net emitters to the atmosphere at the continental scale (19 

Mt C per year), but this flux is highly uncertain (Chapter 

15 this report). The portion of the coastal flux caused by 

human activity is thought to be close to zero, so coastal 

sea-air exchanges should be excluded from the continental 

carbon sink.

As reported in Chapter 2, the sink in the United States is 

approximately 40% (plus or minus 20%) the size of the 

global carbon sink, while the sink in Canada is about 7% 

(plus or minus 7%) the size of the global sink. The source in 

Mexico reduces the global sink by ~4% (plus or minus more 

than 4%). The reason for the disproportionate importance of 

United States’ sinks is probably the unique land-use history 

of the country (summary in Appendix A). During European 

settlement, large amounts 

of carbon were released 

from the harvest of virgin 

forests and the plowing 

of virgin soils to create 

agricultural lands. The 

abandonment of many of 

the formerly agricultural 

lands in the east and the 

regrowth of forest is a 

unique event globally and 

is responsible for about 

one-half of the United 

States’ sink (Houghton 

et al., 2000). Most of the 

United States’ sink thus 

represents a one-time 

recapture of some of the 

carbon that was released 

to the atmosphere during 

settlement. In contrast, 

Mexican ecosystems, 

like those of many tropical nations, are still a net 

carbon source because 

of ongoing deforestation 

(Masera et al., 1997).

The non-fossil fluxes in 

Tables 3.1 and 3.2 are 

derived exclusively from 

inventory methods in 

which the total amount 

of carbon in a pool (i.e., 

living forest trees plus forest soils) is measured on two occasions. The difference between the two measurements shows 

if the pool is gaining (sink) or losing (source) carbon. Carbon 

inventories are straightforward in principle, but of uneven 

quality in practice. For example, we know the carbon in living trees in the United States relatively accurately because 

the U.S. Forest Service Forest Inventory program measures 

trees systematically in more than 200,000 locations. However, we must extrapolate from a few measurements of forest 

soils with models because there is no national inventory of 

carbon in forest soils.

Although the fluxes in Tables 3.1 and 3.2 represent the 

most recent published estimates, with most less than five 

years old, a few are older than ten years (see the citations at 

the bottom of each table). Also, the time interval between 

inventories varies among the elements of the tables, with 

most covering a five to ten year period. In these tables and 

throughout this document we report uncertainties using the 

six categories outlined in Box 3.1.

Table 3.1 Annual net emissions (source = positive) or uptake (land sink = negative) of 

carbon in millions of tons circa 2003 (see Box 3.1 for uncertainty conventions).

a http://www.eia.doe.gov/env/inlenv.htm

b Smith and Heath (2005) for above-ground carbon, but including 20 Mt C per year for United 

States’ urban and suburban forests from Chapter 14, and Pacala et al. (2001) for below-ground 

carbon.

c Environment Canada (2006), Chapter 11, plus 11 Mt C per year for Canadian urban and suburban 

forests, Chapter 14.

d Masera et al. (1997) e Skog et al. (2004), Skog and Nicholson (1998)

f Goodale et al. (2002) g Houghton et al. (1999), Hurtt et al. (2002), Houghton and Hackler (1999). h Chapter 10; Uncertain; Could range from -7 Mt C per year to -14 Mt C per year for North 

America.

i Chapter 13

j Stallard (1998); Pacala et al. (2001)

ND indicates that no data are available.

Source (positive) or 

Sink (negative)

United 

States Canada Mexico N. America

Fossil source (positive)

Fossil fuel (oil, gas, coal) 1582a,** ***

(681, 328, 573)

164a,*****

(75, 48, 40)

110a,*****

(71, 29, 11)

1856*****

(828, 405, 624)

Non-fossil carbon sink (negative) or source (positive)

Forest –256b,*** –28c,*** +52d,** –233***

Wood products –57e,*** –11 f,*** ND –68***

Woody encroachment –120g,* ND ND –120*

Agricultural soils –8h,*** –2h,*** ND –10h,***

Wetlands –23i,* –23i,* –4i,* –49*

Rivers and reservoirs –25 j,** ND ND –25*

Total carbon source or sink –489*** –64** 48* –505***

Net carbon source (positive) 1093  100** * 158*** 1351 
33

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

In addition to inventory methods, it is also possible to estimate carbon sources and sinks by measuring carbon dioxide 

(CO2) in the atmosphere. For example, if air exits the border 

of a continent with more CO2 than it contained when it 

entered, then there must be a net source of CO2 somewhere 

inside the continent. We do not include estimates obtained in 

this way because they are still highly uncertain at continental 

scales. Pacala et al. (2001) found that atmosphere- and inventory-based methods gave consistent estimates of United 

States’ ecosystem sources and sinks but that the range of 

uncertainty from the former was considerably larger than 

the range from the latter. For example, by far the largest 

published estimate for the North American carbon sink 

was produced by an analysis of atmospheric data by Fan 

et al. (1998) (-1700 Mt C per year). The appropriate inventory-based estimate to compare this to is our -666 Mt C per 

year of net absorption (atmospheric estimates include net 

horizontal exports by rivers and trade), and this number is 

well within the wide uncertainty limits in Fan et al. (1998). 

The allure of estimates from atmospheric data is that they 

do not risk missing critical uninventoried carbon pools. 

But in practice, they are still far less accurate at continental 

scales than a careful 

inventory (Pacala et 

al., 2001). Using today’s 

technology, it should be 

possible to complete a 

comprehensive inventory of the sink at national 

scales with the same 

accuracy as the United 

States’ forest inventory 

currently achieves for 

above-ground carbon in 

forests (25%, Smith and 

Heath, 2005). Moreover, 

this inventory would 

provide disaggregated 

information about the 

sink’s causes and geographic distribution. 

In contrast, estimates 

from atmospheric methods 

rely on the accuracy of 

atmospheric models, and 

estimates obtained from 

different models vary by 

100% or more at the scale 

of the United States, Canada, or Mexico (Gurney 

et al., 2004). Nonetheless, 

extensions of the atmospheric sampling network 

should improve the accuracy of atmospheric methods and might allow them to achieve 

the accuracy of inventories at regional and whole-country 

scales. In addition, atmospheric methods will continue to 

provide an independent check on inventories to make sure 

that no large flux is missed, and atmospheric methods will 

remain the only viable method to assess interannual variation in the continental flux of carbon.

The current magnitude of the North American sink (documented in Tables 3.1 and 3.2) offers the possibility that 

significant carbon mitigation could be accomplished by 

managing forests, rangelands, and croplands to increase the 

carbon stored in them. However, many of the estimates in 

Tables 3.1 and 3.2 are highly uncertain; for some, the range 

of uncertainty is larger than the value reported. The largest 

contributors to the uncertainty in the United States’ sink 

are the amount of carbon stored on rangelands because of 

the encroachment of woody vegetation and the lack of comprehensive and continuous inventory of Alaskan lands. A 

carbon inventory of these lands would do more to constrain 

the size of the United States’ sink than would any other 

measurement program of similar cost. Also, we still lack 

Table 3.2 Annual net horizontal transfers of carbon in millions of tons (see Box 3.1 for 

uncertainty conventions).

Net horizontal transfer: imports 

exceed exports = positive; exports 

exceed imports = negative 

United 

States Canada Mexico North America

Wood products 14c,** ** –74a,**** –1b,* –61****

Agriculture products –65d,*** ND ND –65***

Rivers to ocean –35d,** ND ND –35*

Total net absorption

(Total carbon source or sink in Table 3.1 

plus exports)

–575*** –138** 47* –666**

Net absorption (negative) or emission 

(positive) by coastal waters ND ND ND 19e,*

a Environment Canada (2005), World Forest Institute (2006)

b Masera et al. (1997) c Skog et al. (2004), Skog and Nicholson (1998) d Pacala et al. (2001) e Chapter 15

ND indicates that no data are available.

BOX 3.1: CCSP SAP 2.2 Uncertainty Conventions

***** = 95% certain that the actual value is within 10% of the estimate reported, 

  = 95% certain that the estimate is within 25%, 

** * = 95% certain that the estimate is within 50%, 

** = 95% certain that the estimate is within 100%, and

* = uncertainty greater than 100%.

† = The magnitude and/or range of uncertainty for the given numerical 

 value(s) is not provided in the references cited.
The U.S. Climate Change Science Program Chapter 3

34 

comprehensive United States’ inventories of carbon in soils, 

woody debris, wetlands, rivers, and reservoirs. Finally, we 

lack estimates of any kind for five significant components of 

the carbon budget in Canada and six in Mexico (see Tables 

3.1 and 3.2).

The cause and future of the North American carbon sink is 

also highly uncertain. Although we can document the accumulation of carbon in ecosystems and wood products, we 

do not know how much of the sink is due to fertilization of 

the ecosystems by the nitrogen in air pollution and by the 

added CO2 in the atmosphere. We do not fully understand 

the impact of tropospheric ozone, nor do we understand 

precisely how the sink will change as the climate changes. 

Research is mixed about the importance of nitrogen and 

CO2 fertilization (Casperson et al., 2000; Oren et al., 2001; 

Hungate et al., 2003; Luo, 2006; Körner et al., 2005). If these 

factors are weak, then, all else being equal, we expect the 

North American sink to decline over time as ecosystems 

complete their recovery from past exploitation (Hurtt et 

al., 2002). However, if these factors are strong, then the 

sink could grow in the future. Similarly, global warming 

is expected to lengthen the growing season in most parts 

of North America, which should increase the sink (but see 

Goetz et al., 2005). But warming is also expected to increase 

forest fire and the rate of decomposition of dead organic 

matter, which should decrease the sink and might convert 

it into a source (Gillett et al., 2004; Flannigan et al., 2005; 

Schaphoff et al., 2006; Westerling et al., 2006). The relative 

strength of the various opposing factors is still difficult to 

predict. Experimental manipulations of climate, atmospheric 

CO2, tropospheric ozone, and nitrogen, at the largest possible scale, will be required to reduce uncertainty about the 

future of the carbon sink.

In what follows, we provide additional detail about the elements in Tables 3.1 and 3.2.

3.2.1 Forests

Based on U.S. Forest Service inventories, forest ecosystem 

carbon stocks in the United States, excluding soil carbon, 

have increased since 1953. The rate of increase has recently 

slowed because of increasing harvest and declining growth 

in some areas with maturing forests. The current average 

annual increase in carbon in trees is 146 Mt C per year 

(Smith and Heath, 2005, uncertainty ****) plus 20 Mt C 

per year from urban and suburban trees (the midpoint of 

the range in Chapter 14, uncertainty ***). The total estimate 

of the carbon sink in forested ecosystems is -256 Mt C per 

year and includes a sink of 90 Mt C per year (uncertainty 

**) from the accumulation of nonliving carbon in the soil 

(-90-146-20 = -256) (Pacala et al., 2001; Goodale et al.,

2002). Although the magnitude of the forest soil sink has 

always been uncertain, it is now possible to measure the total 

above-and below-ground sink in a few square kilometers by 

monitoring the atmospheric CO2 that flows into and out of 

the site over the course of a year. Note that these spatially 

intensive methods, appropriate for monitoring the sink over 

a few square kilometers, are unrelated to the spatially extensive methods described above, which attempt to constrain 

the sink at continental scales. As described in Appendix B, 

these studies are producing data that, so far, confirm the 

estimates of inventories and show that most of the forest 

sink is above-ground.

According to Canada’s Greenhouse Gas Inventory (Environment Canada 2006, Chapter 11 this report), managed 

forests in Canada (comprising 83% of the total forest area) 

sequestered an average of 17 Mt C per year in trees and 

soils between 1990 and 2004 (uncertainty **). In addition, 

Chapter 14 estimates a sink of 11 (2-20) Mt C per year in 

urban and suburban trees of Canada (uncertainty ***) that 

were not included in the Environment Canada (2006) accounting. The total estimate for the Canadian forest sink is 

thus 28 Mt C per year (Table 3.1).

The two published carbon inventories for Mexican forests 

(Masera et al., 1997 and Cairns et al., 2000) both report 

substantial losses of forest carbon, primarily because of 

deforestation in the tropical south. However, both of these 

studies rely on calculations of carbon loss from remote 

imagery, rather than direct measurements, and both report 

results for a period that ended more than 10 years ago. 

Thus, in addition to being highly uncertain, the estimates 

for Mexican forests in Table 3.1 are not recent. Chapter 14 

estimates a small urban forest sink of 2 (0-3) Mt C per year 

in Mexico. Whether the small urban forest sink would have 

been detected in changes in remote imagery and included 

in the Mexican inventories is uncertain, and accordingly is 

not included in Table 3.1.

3.2.2 Wood Products

Wood products create a carbon sink because they accumulate both in use (e.g., furniture, house frames, etc.) and in 

landfills. The wood products sink is estimated at -57 Mt C 

per year in the United States (Skog and Nicholson, 1998) and 
35

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

-11 Mt C per year in Canada (Goodale et al., 2002, Chapter 

11 this report). We know of no estimates for Mexico.

3.2.3 Woody Encroachment

Woody encroachment is the invasion of woody plants into 

grasslands or the invasion of trees into shrublands. It is 

caused by a combination of fire suppression and grazing. 

Fire inside the United States has been reduced by more than 

95% from the pre-settlement level of approximately 80 million hectares burned per year, and this favors shrubs and 

trees in competition with grasses (Houghton et al., 2000). 

Field studies show that woody encroachment both increases 

the amount of living plant carbon and decreases the amount 

of dead carbon in the soil (Guo and Gifford, 2002; Jackson et 

al., 2002). Although the total gains and losses are ultimately 

of similar magnitude (Jackson et al., 2002), the losses occur within approximately a decade after the woody plants 

invade (Guo and Gifford, 2002), while the gains occur over 

a period of up to a century or more. Thus, the net source 

or sink depends on the distribution of times since woody 

plants invaded, and this is not known. Estimates for the 

size of the current United States’ woody encroachment sink 

(Houghton et al., 1999, Houghton and Hackler, 2000; and 

Hurtt et al., 2002) all rely on methods that do not account 

for the initial rapid loss of carbon from soil when grasslands 

were converted to shrublands or forest. The estimate of -120 

Mt C per year in Table 3.1 is from Houghton et al. (1999), 

but is similar to the estimates from the other two studies 

(-120 and -130 Mt C per year). No estimates are currently 

available for Canada or Mexico. Note the error estimate of 

more than 100% in Table 3.1. A comprehensive set of measurements of woody encroachment would reduce the error 

in the national and continental carbon budgets more than 

any other inventory.

3.2.4 Agricultural Lands

Soils in croplands and grazing lands have been historically 

depleted of carbon by humans and their animals, especially 

if the land was converted from 

forest to non-forest use. Harvest 

or consumption by animals reduces the input of organic matter to the soil, while tillage and 

manure inputs increase the rate 

of decomposition. Changes in 

cropland management, such as 

the adoption of no-till agriculture 

(Chapter 10 this report), have 

reversed the losses of carbon on 

some croplands, but the losses 

continue on the remaining lands. 

The net is a small sink of -2 Mt 

C per year for agricultural soils 

in Canada and, for the United 

States, is a sink of between -5 and -12 Mt C per year. 

3.2.5 Wetlands

Peatlands are wetlands 

that have accumulated 

deep soil carbon deposits because plant productivity has exceeded 

decomposition over 

thousands of years. 

Thus, wetlands form 

the largest carbon pool 

of any North American ecosystem (Table 3.3). If drained for 

development, this soil carbon pool is rapidly lost. Canada’s 

extensive frozen and unfrozen wetlands create a net sink 

of -23 Mt C per year, with from -6 to -11 Mt C per year of 

that sink in areas underlain by permafrost (Chapters 12 and 

13, this report). Drainage of peatlands in the conterminous 

United States has created a source of 6 Mt C per year, but 

other wetlands, including those in Alaska, are a sink of -29 

Mt C per year for a net United States wetland sink of -23 Mt 

C per year (Chapter 13, this report). The very large pool of 

peat in northern wetlands is vulnerable to climate change 

and could add more than 100 ppm to the atmosphere (1 ppm 

≈ 2.1 billion tons of carbon [Gt C]) during this century, if 

released, because of global warming (see the model result 

in Cox et al., 2000 for an example).

T h e c a r b o n 

si n k d u e t o 

sedimentation 

in wetlands is 

estimated to 

be 4 Mt C per 

year in Canada 

and 22 Mt C 

per year in the 

United States, 

Table 3.3 Carbon stocks in North America in billions of tons, (see Box 3.1 for 

uncertainty conventions).

a Goodale et al. (2002) 

b Chapter 10

c Chapter 13

d Masera et al. (1997)

United States Canada Mexico North America

Forest 67a,*** 86a,*** 19d,** 171***

Cropland 14b,  4b,** ** 1b,** 19 

Grazing lands 33b,** * 12b,*** 10b,*** 55***

Wetlands 64c,*** 157c,*** 2c,* 223***

Total 178*** 259*** 33** 468***

Wetlands form the largest 

carbon pool of any North 

American ecosystem (Table 3.3). 

If drained for development, this 

soil carbon pool is rapidly lost.
The U.S. Climate Change Science Program Chapter 3

36 

but this estimate is highly uncertain (Chapter 13 this report). 

Another important priority for research is to better constrain 

carbon sequestration due to sedimentation in wetlands, 

lakes, reservoirs, and rivers.

The focus on this chapter is on CO2; we do not include estimates for other greenhouse gases. However, wetlands are 

naturally an important source of methane (CH4). Methane 

emissions effectively cancel out the positive benefits of any 

carbon storage, such as peat in Canada, and make United 

States’ wetlands a source of warming on a decadal time 

scale (Chapter 13 this report). Moreover, if wetlands become 

warmer and remain wet with future climate change, they 

have the potential to emit large amounts of CH4. This is probably the single most important consideration, and unknown, 

in the role of wetlands and future climate change.

3.2.6 Rivers and Reservoirs

Organic sediments accumulate in artificial lakes and in 

alluvium (deposited by streams and rivers) and colluvium 

(deposited by wind or gravity) and represent a carbon 

sink. Pacala et al. (2001) extended an analysis of reservoir 

sedimentation (Stallard, 1998) to an inventory of the 68,000 

reservoirs in the United States and also estimated net carbon 

burial in alluvium and colluvium. Table 3.1 includes the midpoint of their estimated range of 10 to 40 Mt C per year in the 

coterminous United States. This analysis has also recently 

been repeated and produced an estimate of 17 Mt C per year 

(E. Sundquist, personal communication; unreferenced). We 

know of no similar analysis for Canada or Mexico.

3.2.7 Exports Minus Imports of Wood 

and Agricultural Products

The United States imports 

more wood products (14 Mt 

C per year) than it exports 

and exports more agricultural products (35 Mt C 

per year) than it imports 

(Pacala et al., 2001). The 

large imbalance in agricultural products is primarily because 

of exported grains and oil seeds. Canada and Mexico are net 

wood exporters, with Canada at -74 Mt C per year (Environment Canada, 2005) and Mexico at -1 Mt C per year (Masera 

et al., 1997). The North American export of 61 Mt C per year 

accounts correctly for the large net transfer of lumber and 

wood products from Canada to the United States. We know 

of no analysis of the Canadian or Mexican export-import 

balance for agricultural products.

3.2.8 River Export

Rivers in the coterminous United States were estimated 

to export 30-40 Mt C per year to the oceans in the form 

of dissolved and particulate organic carbon and inorganic 

carbon derived from the atmosphere (Pacala et al., 2001). 

An additional 12-20 Mt C per year of inorganic carbon is 

also exported by rivers but is derived from carbonate minerals. We know of no corresponding estimates for Alaska, 

Canada, or Mexico.

3.2.9 Coastal Waters

Chapter 15 summarizes the complexity and large uncertainty of the sea-air flux of CO2 in North American coastal 

waters. It is important to understand that the source in 

Mexican coastal waters is not caused by humans and would 

have been present in pre-industrial times. It is simply the 

result of the purely physical upwelling of carbon-rich deep 

waters and is a natural part of the oceanic carbon cycle. It 

is not yet known how much of the absorption of carbon by 

United States’ and Canadian coastal waters is natural and 

how much is caused by nutrient additions to the coastal zone 

by humans. Accordingly, it is essentially impossible to currently assess the potential or costs of carbon management 

in coastal waters of North America.

3.3 SUMMARY

Fossil-fuel emissions currently dominate the net carbon balance in the United States, Canada, and Mexico (Figure 3.1, 

Tables 3.1 and 3.2). In 2003, fossil-fuel consumption in the 

United States emitted 1582 Mt C per year to the atmosphere 

(confidence  , see definition of confidence categories in 

Table 3.1 footnote). This source was partially balanced by 

a flow of 489 Mt C per year from the atmosphere to land 

caused by net ecosystem sinks in the United States (** *). 

Canadian fossil-fuel consumption transfered 164 Mt C per 

year to the atmosphere in 2003 (****), but net ecological 

sinks capture 64 Mt C per year (**). Mexican fossil-fuel 

emissions of 110 Mt C per year (****) were supplemented by 

a net ecosystem source of 48 Mt C per year (*) from tropical 

deforestation. Each of the three countries has always been a 

net source of CO2 emissions to the atmosphere for the past 

three centuries (Houghton et al., 1999, 2000; Houghton and 

Hackler, 2000; Hurtt et al., 2002).

Fossil-fuel emissions currently 

dominate the net carbon 

balance in the United States, 

Canada, and Mexico.
The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

What Are the Options That Could 

Significantly Affect the North American 

Carbon Cycle?

CHAPTER

4

37

Coordinating Lead Author: Erik Haites, Margaree Consultants, Inc.

Lead Authors: Ken Caldeira, Carnegie Inst.; Patricia Romero Lankao, 

NCAR and UAM-Xochimilco; Adam Z. Rose, The Pa. State Univ. and 

Univ. Southern Calif.; Thomas J. Wilbanks, ORNL

Contributing Authors: Skip Laitner, U.S. EPA; Richard Ready, The Pa. 

State Univ.; Roger Sedjo, Resources for the Future

For further affiliation details see the Author Team list on pages III and IV

KEY FINDINGS

Options to reduce energy-related carbon dioxide emissions include improved efficiency, fuel switching (among fossil 

fuels and non-carbon fuels), and carbon dioxide capture and storage.

Most energy use, and hence energy-related carbon dioxide emissions, involves equipment or facilities with a relatively 

long life—5 to 50 years. Many options for reducing these carbon dioxide emissions are most cost-effective, and 

sometimes only feasible, in new equipment or facilities. This means that cost-effective reduction of energy-related 

carbon dioxide emissions may best be achieved as existing equipment and facilities are replaced1. If emission reductions 

are implemented over a long time, technological change will have a significant impact on the cost.

Options to increase carbon sinks include forest growth and agricultural soil sequestration. The amount of carbon that 

can be captured by these options is significant, but additions to current stocks would be small to moderate relative 

to carbon emissions. These options can be implemented in the short term, but the amount of carbon sequestered 

typically is low initially, then rises for a number of years before tapering off again as the total potential is achieved. 

There is also a significant risk that the carbon sequestered may be released again by natural phenomena or human 

activities.

Both policy-induced and voluntary actions can help reduce carbon emissions and increase carbon sinks, but significant 

changes in the carbon budget are likely to require policy interventions. The effectiveness of a policy depends on the 

technical feasibility and cost-effectiveness of the portfolio of actions it seeks to promote, on its suitability given the 

institutional context, and on its interaction with policies implemented to achieve other objectives.

Policies to reduce atmospheric carbon dioxide concentrations cost effectively in the short- and long-term could include: 

(1) encouraging adoption of cost-effective emission reduction and sink enhancement actions through such mechanisms 

as an emissions trading program or an emissions tax; (2) stimulating development of technologies that lower the cost 

of emissions reduction, carbon capture and sequestration, and sink enhancement; (3) adopting appropriate regulations 

for sources or actions subject to market imperfections, such as energy efficiency measures and cogeneration; (4) 

revising existing policies with other objectives that lead to higher carbon dioxide or methane emissions so that the 

objectives, if still relevant, are achieved with lower emissions; and (5) encouraging voluntary actions.

Implementation of such policies at a national level, and cooperation at an international level, would reduce the overall 

cost of achieving a carbon reduction target by providing access to more low-cost mitigation/sequestration options. 

1

 An emission reduction action is cost-effective if the cost per ton of carbon dioxide reduced is lower than the least-cost alternative.

•

•

•

•

•

•
The U.S. Climate Change Science Program

38 

Chapter 4

4.1 INTRODUCTION

This chapter provides an overview of options that can reduce carbon dioxide (CO2) and methane (CH4) emissions 

and those that can enhance carbon sinks, and it attempts to 

compare them. Finally, it discusses policies to encourage 

implementation of source reduction and sink enhancement 

options. No emission reduction or sink enhancement target 

is proposed, and no policy or option is recommended.

4.2 SOURCE REDUCTION OPTIONS

4.2.1 Energy-Related Carbon Dioxide Emissions

Combustion of fossil fuels is the main source of CO2 emissions (Chapters 1-3 this report), although some CO2 is also 

released in non-combustion and natural processes. Most energy use, and hence energy-related CO2 emissions, involves 

equipment or facilities with a relatively long life—5 to 50 

years. Many options for reducing these CO2 emissions are 

most cost-effective, and sometimes only feasible, in new 

equipment or facilities (Chapters 6 through 9 this report).

To stabilize the atmospheric 

concentration of CO2 “would 

require global anthropogenic 

CO2 emissions to drop below 

1990 levels . . . and to steadily 

decrease thereafter” (IPCC, 

2001)2. That entails a transition to a very different energy 

system, for example, where the 

major energy carriers are electricity and hydrogen produced 

by non-fossil sources or from 

fossil fuels with capture and geological storage of the CO2

generated. A transition to such an energy system, while also 

meeting growing energy needs, could take at least several 

decades. Thus, shorter term (2015–2025) and longer term 

(post-2050) options are differentiated.

Options to reduce energy-related CO2 emissions can be 

grouped into a few categories:

efficiency improvement,

fuel switching to fossil fuels with lower carbon content 

per unit of energy produced or to non-fossil fuels, and 

switching to electricity and hydrogen produced from 

fossil fuels in processes with CO2 capture and geological storage.

2

 The later the date at which global anthropogenic CO2 emissions drop 

below 1990 levels, the higher the level at which the CO2 concentration 

is stabilized.

•

•

•

4.2.1.1 Efficiency Improvement

Energy is used to provide services such as heat, light, and 

motive power. Any measure that delivers the desired service 

with less energy is an efficiency improvement3

. Efficiency 

improvements reduce CO2 emissions whenever they reduce 

the use of fossil fuels at any point between production of the 

fuel and delivery of the desired service4. Energy use can be 

reduced by improving the efficiency of individual devices 

(such as refrigerators, industrial boilers, and motors), by 

improving the efficiency of systems (using the correct motor 

size for the task), and by using energy that is not currently 

utilized, such as waste heat5. Opportunities for efficiency 

improvements are available in all sectors.

It is useful to distinguish two 

levels of energy efficiency 

improvement: (1) the amount 

consistent with efficient utilization of resources (the economic definition) and (2) the 

maximum attainable (the engineering definition). Energy 

efficiency improvement thus 

covers a broad range, from 

measures that provide a cost 

saving to measures that are 

technically feasible but too expensive under current market 

conditions to warrant implementation. Market imperfections 

inhibit adoption of some cost-effective efficiency improvements (NCEP, 2005)6

.

Energy efficiency improvements tend to occur gradually, 

but steadily, across the economy in response to technological developments, replacement of equipment and buildings, 

changes in energy prices, and other factors7. In the short 

term, the potential improvement depends largely on greater 

deployment and use of available efficient equipment and 

technology. In the long term, it depends largely on tech3

 In the transportation sector, for example, energy efficiency can be 

increased by improving the fuel performance of vehicles, shifting to 

less emissions-intensive modes of transport, and adopting options 

that reduce transportation demand, such as telecommuting and 

designing communities so that people live closer to shopping and 

places of work.

4

 Increasing the fuel economy of vehicles or the efficiency of coalfired generating units reduces fossil-fuel use directly. Increasing 

the efficiency of refrigerators or electricity transmission reduces 

electricity use and hence the fossil fuel used to generate electricity.

5

 For example, 40 to 70% of the energy in the fuel used to generate 

electricity is wasted. Cogeneration or combined heat and power 

systems generate electricity and produce steam or hot water. 

Cogeneration requires a nearby customer for the steam or heat. 

6

 Examples of market imperfections include limited foresight, 

externalities, capital market barriers, and principal/agent split 

incentive problems. As an example of the principal/agent imperfection, 

a landlord has little incentive to improve the energy efficiency of the 

housing unit and its appliances if the tenant pays the energy bills.

7

 The rate of efficiency improvement varies widely across different 

types of equipment such as lighting, refrigerators, electric motors, 

and motor vehicles.

Canada and the United 

States use much more 

energy per capita than other 

high income countries, 

suggesting considerable 

potential to reduce energy 

use and associated CO2

emissions with little impact 

on the standard of living.
39

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

nological developments. Canada and the United States 

use much more energy per capita than other high-income 

countries, suggesting considerable potential to reduce energy 

use and associated CO2 emissions with little impact on the 

standard of living8.

4.2.1.2 Fuel Switching

Energy-related CO2 emissions are primarily due to combustion of fossil fuels. Thus CO2 emissions can be reduced by 

switching to a less carbon-intensive fossil fuel or to a noncarbon fuel.

The CO2 emissions per unit of energy (carbon intensity) for 

fossil fuels differ significantly, with coal being the highest, 

oil and related petroleum products about 25% lower, and 

natural gas over 40% lower than coal. Oil and/or natural 

gas can be substituted for coal in all energy uses, mainly 

electricity generation. However, natural gas is not available 

everywhere in North America and is much less abundant 

than coal, limiting the large-scale, long-term replacement of 

coal with natural gas. Technically, natural gas can replace oil 

in all energy uses, but to substitute for gasoline and diesel 

fuel, by far the largest uses of oil, would require conversion 

of millions of vehicles and development of a gas-refueling 

infrastructure.

Non-fossil fuels include

biomass and fuels, such as ethanol and biodiesel, produced from biomass; and

electricity and hydrogen produced from carbon-free 

sources.

Biomass can be used directly as a fuel in some situations. 

Pulp and paper plants and sawmills, for example, can use 

wood waste and sawdust as fuel. Ethanol, currently produced 

mainly from corn, is blended with gasoline and biodiesel is 

produced from vegetable oils and animal fats. Wood residuals 

and cellulose materials, such as switch grass, can be utilized 

both for energy and the production of syngases, which can 

be used to produce biopetroleum (AF&PA, 2006). The CO2

emission reduction achieved depends on whether the biomass 

used is replaced, on the emissions associated with production 

and combustion of the biomass fuel, and the carbon content 

of the fuel displaced9.

8

 The total primary energy supply per capita during 2004, in tons of 

oil equivalent, was 8.42 for Canada, 7.91 for the United States, 4.43 for 

France, 4.22 for Germany, 4.18 for Japan, 3.91 for the United Kingdom, 

and 1.59 for Mexico (IEA, 2006a).

9

 The CO2 reductions achieved depend on many factors including 

the inputs used to produce the biomass (fertilizer, irrigation water), 

whether the land is existing cropland or converted from forests or 

grasslands, and the management practices used (no-till, conventional 

till).

•

•

Carbon-free energy sources include hydro, wind, solar, 

biomass, geothermal, and nuclear fission10. Sometimes they 

are used to provide energy services directly, such as solar 

water heating and windmills for pumping water. But they 

are mainly used to generate electricity, about 35% of the 

electricity in North America. Currently, generating electricity 

using any of the carbon free energy sources is usually more 

costly than using fossil fuels.

Most of the fuel switching options are currently available, 

and so are viable short-term options in many situations.

4.2.1.3 Electricity and Hydrogen From Fossil 

Fuels with Carbon Dioxide Capture and Storage

About 65% of the electricity in North America is generated 

from fossil fuels, mainly coal, but with a rising share for 

natural gas (EIA, 2003a; Chapter 6 this report). The CO2

emissions from fossil-fired generating units can be captured 

and injected into a suitable geological formation for longterm storage.

Hydrogen (H2) is an energy 

carrier that emits no CO2 when 

burned, but may give rise to 

CO2 emissions when it is produced (National Academies, 

2004). Currently, most hydrogen is produced from fossil 

fuels in a process that generates 

CO2 (National Research Council, 2004). The CO2 from this 

process can be captured and stored in geological formations. 

Alternatively, hydrogen can be produced from water using 

electricity, in which case the CO2 emissions depend on how 

the electricity is generated. Hydrogen could substitute for 

10 Reservoirs for hydroelectric generation produce CO2 and CH4

emissions, and production of fuel for nuclear reactors generates CO2

emissions, so such sources are not totally carbon free.

Carbon-free energy sources 

include hydro, wind, solar, 

biomass, geothermal, and 

nuclear fission. Combined 

these sources generate 

about 35% of the electricity 

in North America.
The U.S. Climate Change Science Program

40 

Chapter 4

40 

natural gas in most energy uses and could be used by fuel 

cell vehicles.

Carbon dioxide can be captured from the emissions of large 

sources, such as power plants, and pumped into geologic 

formations for long-term storage, thus permitting continued 

use of fossil fuels while avoiding CO2 emissions to the atmosphere11. Many variations on this basic theme have been 

proposed; for example, pre-combustion vs. post-combustion 

capture, production of hydrogen from fossil fuels, and the 

use of different chemical approaches and potential storage 

reservoirs (IPCC, 2005). While 

most of the basic technology 

exists, legal, environmental, 

and safety issues need to be addressed before CO2 capture 

and storage can be integrated into our energy system, so this 

is mainly a long-term option (IPCC, 2005). Carbon dioxide 

capture and storage could contribute about 30% (15-55%) of 

the total mitigation effort, mainly after 2025 (IPCC, 2005; 

IEA, 2006b; Stern, 2006).

4.2.2 Industrial Processes

The processes used to make cement, lime, and ammonia 

release CO2. Because the quantity of CO2 released is determined by chemical reactions, the process emissions are 

determined by the output. But the CO2 could be captured 

and stored in geological formations. Carbon dioxide also is 

released when iron ore and coke are heated in a blast furnace to produce molten iron, but alternative steel-making 

technologies with lower CO2 emissions are commercially 

available. Consumption of the carbon anodes during aluminum smelting leads to CO2 emissions, but good management 

practices can reduce the emissions. Raw natural gas contains 

CO2 that is removed at gas processing plants and could be 

captured and stored in geological formations.

4.2.3 Methane Emissions 

Methane is produced as organic matter decomposes in lowoxygen conditions and is emitted by landfills, wastewater 

treatment plants, and livestock manure. In many cases, the 

CH4 can be collected and used as an energy source. Methane emissions also occur during 

the transport of natural gas. Such 

emissions usually can be flared 

or collected for use as an energy 

source12. Ruminant animals produce CH4 while digesting their 

food. Emissions by ruminant farm 

11 Since combustion of biomass releases carbon previously removed 

from the atmosphere, capture and storage of these emissions results 

in negative emissions (a sink).

12 Flaring or combustion of CH4 as an energy source produces CO2

emissions.

animals can be reduced by measures that improve animal 

productivity. All of these emission reduction options are 

currently available.

4.3 TERRESTRIAL SEQUESTRATION 

OPTIONS

Trees and other plants sequester carbon as biological growth 

captures carbon from the atmosphere and sequesters it in 

the plant cells (IPCC, 2000). Currently, very large volumes 

of carbon are sequestered in the plant cells of the Earth’s 

forests. Increasing the stock of forest through afforestation13, 

reforestation, or forest management draws carbon from the 

atmosphere and increases the carbon sequestered in the forest and the soil of the forested area. Sequestered carbon is 

released by fire, insects, disease, decay, wood harvesting, 

conversion of land from its natural state, and disturbance 

of the soil. Substituting long-lived wood products for steel 

and cement can reduce emissions and increase the amount 

of carbon sequestered.

Agricultural practices can increase the carbon sequestered 

by the soil. Some crops build soil organic matter, which is 

largely carbon, better than others. Some research shows that 

crop-fallow systems result in lower soil carbon content than 

continuous cropping systems (Chapter 10 this report). No-till 

and low-till cultivation builds soil organic matter.

Conversion of agricultural land to forestry can increase 

carbon sequestration in soil and tree biomass, but the rate 

of sequestration depends on environmental factors (such 

as type of trees planted, soil type, climate, and topography) 

and management practices (such as thinning, fertilization, 

and pest control). Conversion of agricultural land to other 

uses can result in positive or negative net carbon emissions 

depending upon the land use.

Forest growth and soil sequestration currently offset about 

30% (15-45%) of the North American fossil fuel emissions 

(Chapter 3 this report), and this percentage might be increased to some degree. These options can be implemented 

in the short term, but the amount of carbon sequestered typically is low initially, then rises for a number of years before 

tapering off again as the total potential is achieved (Chapters 

10-13 this report).

4.4 INTEGRATED COMPARISON OF 

OPTIONS

As is clear from the previous sections, there are many options 

to reduce emissions of or to sequester CO2. To help them 

decide which options to implement, policy makers need to 

13 See the Glossary for a definition of this term and related terms. 

CO2 capture and storage 

could contribute about 

30% of the total mitigation 

effort, mainly after 2025.

Forest growth and soil 

sequestration currently 

offset about 30% of 

the North American 

fossil-fuel emissions.
41

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

BOX 4.1: Emission Reduction Supply Curve

A tool commonly used to compare emission reduction and sequestration options is an emission reduction supply 

curve, such as that shown in the figure. It compiles the emission reduction and sequestration options available 

for a given jurisdiction at a given time. If the analysis is for a future date, a detailed scenario of future conditions 

is needed. The estimated emission reduction potential of each option is based on local circumstances at the 

specified time, taking into account the interaction among options, such as improved fuel efficiency for vehicles 

and greater use of less carbon-intensive fuel. The options are combined into a curve starting with the most 

cost-effective and ending with the least cost-effective. For each option, the curve shows the cost per metric 

ton of CO2 reduced on the vertical axis and the potential emission reduction, tons of CO2 per year, on the 

horizontal axis. The curve can be used to identify the lowest cost options to meet a given emission reduction 

target, the associated marginal cost (the cost per metric ton of the last option included), and total cost (the 

area under the curve).

An emission reduction supply curve is an excellent tool for assessing alternative emission reduction targets. The 

best options and cost are easy to identify. The effect on the cost of dropping some options is easy to calculate 

unless they interact with other options. And the cost impact of having to implement additional options due to 

underperformance by others is simple to estimate. The drawbacks are that constructing the curve is a complex 

analytical process and that the curve is out of date almost immediately because fuel prices and the cost or performance of some options change.

When constructed for a future date, such as 2010 or 2020, the precision suggested by the curve is misleading 

because the future will differ from the assumed scenario. A useful approach in such cases is to group options into 

cost ranges, such as less than $5 per metric ton of CO2, $5 to $15 per metric ton of CO2, etc., ignoring some 

interaction effects and the impacts of the policy used to implement the option. This still identifies the most costeffective options. Comparing the emissions reduction target with the emission reduction potential of the options 

in each group indicates the most economic strategy.

The curve shows the estimated unit cost ($/t CO2 equivalent) and annual emission reduction (t CO2 equivalent) for emission reduction and sequestration options for a given region and date arranged in order of increasing unit cost.
The U.S. Climate Change Science Program

42 

Chapter 4

42 

know the magnitude of the potential emission reduction at 

various costs for each option so they can select the options 

that are the most cost-effective—have the lowest cost per 

metric ton of CO2 reduced or sequestered.

This involves an integrated comparison of options, which 

can be surprisingly complex in practice. It is most useful and 

accurate for short-term options where the cost and performance of each option can be forecast with a high degree of 

confidence. The performance of many options is interrelated; 

for example, the emission reductions that can be achieved by 

blending ethanol in gasoline depend, in addition to the factors relating to ethanol production previously cited, on other 

options, such as telecommuting to reduce travel demand, 

the success of modal shift initiatives, and the efficiency of 

motor vehicles. The prices of fossil fuels affect the cost-effectiveness of many options. Finally, the policy enacted to 

encourage an option, incentives vs. a regulation for example, 

can affect its potential.

The emission reduction potential and cost-effectiveness of 

options also vary by location. Energy sources and sequestration options differ by location; for example, natural gas may 

not be available, the wind and solar regime vary, hydro potential may be small or large, land suitable for afforestation/

reforestation is limited, the agricultural crops may or may 

not be well suited to low-till cropping. Climate, lifestyles, 

and consumption patterns also affect the potential of many 

options; for example, more potential for heating options in a 

cold climate or air conditioning options in a hot climate. The 

mix of single-family and multi-residential buildings affects 

the potential for options focused on those building types, 

and the scope for public transit options tends to increase 

with city size. Institutional factors affect the potential of 

many options as well; for example, the prevalence of rented 

housing affects the potential to implement residential emission reduction measures, the authority to specify minimum 

efficiency standards for vehicles, appliances, and equipment 

may rest with the state/provincial government or the national 

government, and the ownership and regulatory structure for 

gas and electric utilities can affect their willingness to offer 

energy efficiency programs.

The estimated cost and emission reduction potential for the 

principal short-term CO2 emission reduction and sequestration options are summarized in Table 4.1. All estimates are 

expressed in 2004 United States dollars per metric ton of 

carbon . The limitations of emission reduction supply curves 

noted in the text box apply equally to the cost estimates in 

Table 4.1.

Most options have a range of costs. The range is due to four 

factors. First, the cost per unit of emissions reduced varies 

by location even for a very simple measure. For example, the 

emission reduction achieved by installing a more efficient 

light bulb depends on the hours of use and the generation mix 

that supplies the electricity. Second, the cost and performance 

of any option in the future is uncertain. Different assumptions about future costs and performance contribute to the 

range. Third, most mitigation and sequestration options are 

subject to diminishing returns, that is, their cost rises at an 

increasing rate with greater use, as in the power generation, 

agriculture, and forestry cost estimates14. So the estimated 

scale of adoption contributes to the range. Finally, some categories include multiple options, notably those for the United 

States economy as a whole, each with its own marginal cost. 

For example, the “All Industry” category is an aggregation of 

seven subcategories discussed in Chapter 8 this report. The 

result again is a range of cost estimates.

The cost estimates in Table 4.1 are the direct costs of the 

options. A few options, such as the first estimate for power 

generation in Table 4.1, have a negative annualized cost. 

This implies that the option is likely to yield cost savings 

for reasons such as improved combustion efficiency. Some 

options have ancillary benefits (e.g., reductions in ordinary 

pollutants, reduced dependence on imported oil, expansion 

of wildlife habitat associated with afforestation) that reduce 

their cost from a societal perspective. Indirect (multiplier, 

general equilibrium, macroeconomic) effects in the economy 

tend to increase the direct costs (as when the increased cost 

of energy use raises the price of products that use energy or 

energy-intensive inputs). Examples of these complicating 

effects are presented in Chapters 6 through 11 this report, 

along with some estimates of their impacts on costs.

None of the options listed in Table 4.1 offers the prospect 

of carbon budget stabilization alone (see below), which 

indicates a need to consider combinations of options. In any 

such consideration, costs are the primary driving force (e.g., 

Table 4.1). Other considerations affecting the choice of options include the magnitudes of their potential contributions, 

their feasibility, and the time scale of their contribution. Table 

4.2 summarizes these characteristics for the main families of 

emission reduction and sink enhancement options (see also 

Kauppi et al., 2001).

As indicated in several segments of Table 4.1, costs are 

sensitive to the policy instruments used to encourage the 

option. In general, the less restrictive the policy, the lower 

the cost. That is why the cost estimates for the Feebate15 are 

lower than the cost estimate for the Corporate Average Fuel 

Economy (CAFE) standard. In a similar vein, costs are low14 For example, increasing the scale of tree planting to sequester 

carbon requires more land. Typically, the value of the extra land used 

rises, so the additional sequestration becomes increasingly costly.

15 A “Feebate” is a system of progressive vehicle taxes on purchases 

of less efficient new vehicles and subsidies for more efficient new 

vehicles. 
43

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

ered by expanding the number of participants in an emissions 

trading arrangement, especially those with a prevalence of 

low-cost options, such as developing countries. That is why 

global trading costs are lower than the industrialized country 

trading case for the United States economy.

The task of choosing the “best” combination of options may 

seem daunting given the numerous options, their associated 

cost ranges, and ancillary impacts. This combination will 

depend on several factors including the emission target, the 

emitters covered, the compliance period, and the ancillary 

benefits and costs of the options. The best combination 

will change over time as locations where cheap options can 

be implemented are exhausted, and technological change 

lowers the costs of more expensive options. It is unlikely 

that decision makers can identify the least-cost combination of options to achieve a given emission target, but they 

can adopt policies, such as emissions trading or emissions 

Option/applicable 

date(s)

Annualized average 

cost (in $2004 U.S.)

Potential range 

(Mt C per year) or % 

reduction

Source

Power generation -$227 to 1176/tC N.A. DOE/EIA (2006)

Transportation/2010

(U.S. permit trading) $84/t C N.A. EIA (2003b)

Transportation/2025

 (U.S. permit trading) $236/t C 22 EIA (2003b)

Transportation/2017

(CAFE standarda

) $82/t C 39 CBO (2003)

Transportation/2030 

(Feebateb

) $47/t C 67 Greene et al. (2005)

Buildings N.A. 60% for offices

70% for homes

USGBC (2005)

DOE/EERE (2006)

Afforestation/2010-2110 $60 to 120/t C 37 to 224

EPA (2005)

Forest management/2010-

2110 $4 to 120/t C 7 to 86

Biofuels/2010-2110 $120 to 201/t C 102 to 153

Agricultural soil carbon

sequestration/2010-2110 $20 to 60/t C 34 to 46

All industry

 Reduction of fugitives $92 to 180/t C 3%

Herzog (1999)

Martin et al. (2001)

Jaccard et al. (2002, 

2003a, 2003b)

Worrel et al. (2004)

DOE (2006)

 Energy efficiency $0 to 180/t C 8% to 12%

 Process change $92 to 180/t C 20%

 Fuel substitution $0 to 92/t C 10%

 CO2 capture and storage $180 to 367/t C 30%

Waste management

 Reduction of fugitives $0 to 92/t C 90% Herzog (1999)

Jaccard et al. (2002) CO2 capture and storage >$367/t C 30%

Entire U.S. economy

 No trading $102 to 548/t Cc Not specified

 Industrialized country EMF (2000)

 trading $19 to 299/t Cc Not specified

 Global trading $7 to 164/t Cc Not specified

Table 4.1 Standardized cost estimates for short-term CO2 emission reduction and 

sequestration options (annualized cost in 2004 constant U.S. dollars per metric ton of 

carbon [t C]).

a CAFE= Corporate Average Fuel Economy

b

 A “feebate” is a system of progressive vehicle taxes on purchases of less efficient new vehicles and subsidies for 

more efficient new vehicles.

c Annualized marginal cost (cost at upper limit of application, and therefore typically higher than average cost).
The U.S. Climate Change Science Program

44 

Chapter 4

taxes, that cover a large number of emitters and allow them 

to use their first-hand knowledge to choose the lowest cost 

reduction options16.

4.5 IMPLEMENTATING OPTIONS

4.5.1 Overview

No single technology or approach can achieve a sufficiently 

large CO2 emission reduction or sequestration to stabilize the 

carbon cycle (Hoffert et al., 1998, 2002; Pacala and Socolow, 

2004). Decision makers will need to consider a portfolio of 

options to reduce emissions 

and increase sequestration in 

the short term, taking into account constraints on and implications of mitigation strategies 

and policies. The portfolio of 

short-term options is likely 

to include greater efficiency 

in the production and use of 

16 Swift (2001) finds that emissions trading programs yield greater 

environmental and economic benefits than regulations. Several other 

studies of actual policies (Ellerman et al., 2000) and proposed policies 

(Rose and Oladosu, 2002) have indicated relative cost savings of these 

incentive-based instruments. 

energy; expanded use of 

non-carbon and low-carbon 

energy technologies; and 

various changes in forestry, 

agricultural, and land-use 

practices. Actions will also 

be supported by encouraging research and development of technologies that 

can reduce emissions even 

further in the long term, 

such as technologies for removing carbon from fossil 

fuels and sequestering it in 

geological formations and 

possibly other approaches, 

some of which are currently 

very controversial, such as 

certain types of “geoengineering.”

Because CO2 has a long atmospheric residence time17, 

immediate action to reduce 

emissions and increase 

sequestration allows its 

atmospheric concentration 

to be stabilized at a lower 

level18. Policy instruments 

to promote cost-effective 

implementation of a portfolio of options covering virtually 

all emissions sources and sequestration options are available 

for the short term. Implementation of policy instruments at 

a national level, and cooperation at an international level, 

would reduce the overall cost of achieving a carbon reduction 

target by providing access to more low-cost mitigation/sequestration options.

17 Carbon dioxide has an atmospheric lifetime of 5 to 200 years. A 

single lifetime can not be defined for CO2 because of different rates of 

uptake by different removal processes. (IPCC, 2001, Table 1, p. 38)

18 IPCC (2001), p. 187.

No single technology or 

approach can achieve a 

sufficiently large CO2

emission reduction or 

sequestration to stabilize 

the carbon cycle. 

Category of Options

Magnitude 

of potential 

contribution

Feasibility of 

contribution

Time scale of 

contribution

Emission reduction

 Efficiency improvement Moderate High Near to mid term

 Fuel switching:

 - to less carbon-intensive

 fossil fuels Small to moderate High Near to mid term

 - to non-fossil fuels Moderate to large Moderate to high Mid to long term

 CO2 capture and storage Large1 Highly uncertain2 Long term3

Sink enhancement

 Forests Small to moderate Moderate to high Near to mid term

 Soils Small Moderate to high Mid to long term

Table 4.2 Overview of possible contributions of families of options to managing the North 

American carbon cycle.a

 Note that combining a number of small contributions can add 

up to a moderate contribution, and combining a number of moderate contributions can 

sdd up to a large contribution.

a Magnitude refers to the potential size of contribution in net emission reduction: large = above 500 MtC 

yr-1; moderate = 250-500; small = below 250. Feasibility refers to the likelihood that such a magnitude 

can be reached under reasonable assumptions about economic, policy, and science/technology conditions. 

Time scale is defined as: long term = beyond 2040; mid term = 2020-2040; near term = sooner than 

2020. Following principles of analytic-deliberative assessment (Stern and Fineberg, 1996), these categories 

represent the authors’ expert synthesis and qualitative assessment or interpretation of diverse information presented or cited in this and other chapters of this report as well as from relevant literature (e.g., 

IPCC, 2005; Kauppi et al., 2001). 1

Depending upon the (uncertain) availability of large geological reservoirs the potential contribution could 

possibly be very large (much greater than 500 Mt C per year).

2

 Uncertainty in availability of reservoirs, technology, public risk perception and costs among other factors 

makes the feasibility of large scale applications capable of realizing large potential highly uncertain.

3

For large-scale or large-magnitude contributions exceeding the small magnitude, near term contributions 

of pilot-studies or existing oil recovery applications. 
45

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

The effectiveness of such policies is determined by 

the technical feasibility and cost-effectiveness of 

the portfolio of options they seek to promote, their 

interaction with other policies that have unintended 

impacts on CO2 emissions, and their suitability 

given the institutional and socioeconomic context 

(Raupach et al., 2004). This means that the effectiveness of the portfolio can be limited by factors 

such as:

Demographic and social dynamics. Land 

tenure, population growth, and migration may 

pose an obstacle to afforestation/reforestation 

strategies.

Institutional settings. The acceptability of 

taxes, subsidies, and regulations to induce 

the deployment of certain technology may be 

limited by stakeholder opposition.

Environmental considerations. The portfolio of options 

may incur environmental costs such as nuclear waste 

disposal or biodiversity reduction.

Institutional and timing aspects of technology transfer. 

The patent system, for instance, may pose a barrier for 

some countries and sectors in obtaining the best available technology.

4.5.2 General Considerations

Decisions about the implementation of options for carbon 

management are made at a variety of geographic scales, by a 

variety of decision makers, for a variety of reasons. In many 

cases, they emphasize decentralized voluntary decision-making within market and other institutional conditions that are 

shaped by governmental policies. Over the past decade in the 

United States, state and local governments and private firms, 

motivated by such factors as cost savings, public image, and 

perceptions of possible future policy directions, have implemented voluntary actions to reduce CO2 emissions (Kates and 

Wilbanks, 2003). Although these actions have contributed to 

a decline in the ratio of CO2 emissions to GDP (Casler and 

Rose, 1998), total emissions have continued to increase.

A wide array of policies have been implemented or are under 

discussion by governments in North America19. Policies to 

encourage reduction and sequestration of CO2 emissions 

could include information programs, voluntary programs, 

conventional regulation, emissions trading, and emissions 

taxes (Tietenberg, 2000). Working Group III of the Intergovernmental Panel on Climate Change (IPCC) concluded 

that “[V]oluntary agreements between industry and governments, which vary considerably, are politically attractive, 

raise awareness among stakeholders, and have played a role 

19 Policies can be found at: http://www.epa.gov/climatechange/policy/

neartermghgreduction.html, http://www.ecoaction.gc.ca/index-eng.

cfm, and http://cambio_climatico.ine.gob.mx/ccygob/ccygobingles.

html 

•

•

•

•

in the evolution of many national policies. . . However, there 

is little evidence that voluntary agreements have achieved 

significant emissions reductions beyond business as usual 

(high agreement/much evidence).” (Gupta et al. 2007; see 

also OECD, 2003b; Harrison, 1999; King and Lenox, 2000; 

Welch et al., 2000; Darnall and Carmin, 2003; Croci, 2005; 

Jaccard et al., 2006).

Reducing annual emissions in North America consistently 

over several decades requires a portfolio of policies across 

all sectors and gases tailored to fit specific national circumstances. Regulations can 

require designated sources 

to keep their emissions below a specified limit, either a 

quantity per unit of output or 

an absolute amount per day 

or year. Regulations can also 

stipulate minimum or average 

levels of energy efficiency of 

appliances, buildings, equipment, and vehicles.

An emissions trading program establishes a cap on the annual 

emissions of a set of sources. Allowances equal to the cap are 

issued and can be traded. Each source must monitor its actual 

emissions and remit allowances equal to its actual emissions 

to the regulator. An emission trading program creates an 

incentive for sources with low-cost options to reduce their 

emissions and sell their surplus allowances. Sources with 

high-cost options find it less expensive to buy allowances at 

the market price than to reduce their own emissions enough 

to achieve compliance.

An emissions tax requires designated sources to pay a specified levy for each unit of its actual emissions. Each emitter 

will reduce its emissions to the point where the mitigation 

Although voluntary actions 

have contributed to a 

decline in the ratio of 

CO2 emissions to GDP, 

total emissions have 

continued to increase.
The U.S. Climate Change Science Program

46 

Chapter 4

46 

cost is equal to the tax, but once the mitigation cost exceeds 

the tax, the emitter will opt to pay the tax.

The framework for evaluating such a policy instrument 

needs to consider technical, institutional, and socioeconomic 

constraints that would affect its implementation, such as 

the ability of sources to monitor their actual emissions, the 

constitutional authority of national and/or provincial/state 

governments to impose emissions taxes, regulate emissions 

and/or regulate efficiency standards. It is also important 

to consider potential conflicts between carbon reduction 

policies and policies with other objectives, such as keeping 

energy costs to consumers as low as possible.

Practically every policy (except cost-saving energy conservation options)20, no matter what instrument is used to 

implement it, has a cost in terms of utilization of resources 

and ensuing price increases that leads to reductions in output, income, employment, or other measures of economic 

well-being. The total cost is usually higher than the direct 

cost due to interactions with other segments of the economy 

and with existing policies (“general equilibrium” effects). 

Regardless of where the compliance obligation is imposed, 

the cost ultimately is borne by the general public as consumers, shareholders, employees, taxpayers, and recipients of 

government services21. The cost can have competitiveness 

impacts if some emitters in other jurisdictions are not subject 

to similar policies. But societal benefits, such as improved 

public health and reduced environmental damage, may offset 

part or all of the cost of implementing the policy.

20 These are often called “no regret” options. 21 The source with the compliance obligation passes on the cost 

through some combination of higher prices for its products, negotiating 

lower prices with suppliers, layoffs, and/or lower wages for employees, 

and lower profits that lead to lower tax payments and lower share 

prices. Other firms that buy the products or supply the inputs make 

similar adjustments. Governments raise taxes or reduce services to 

compensate for the loss of tax revenue. Ultimately, all of the costs are 

borne by the general public.

To achieve a given emission reduction target, regulations that require each affected source to meet a specified emissions limit or implement specified controls 

are almost always more costly than emissions trading 

or emissions taxes because they require each affected 

source to meet the regulation regardless of cost rather 

than allowing emission reductions to be implemented 

where the cost is lowest (Bohm and Russell, 1986)22. The 

cost saving available through trading or an emissions 

tax generally increases with the diversity of sources and 

share of total emissions covered by the policy (Rose and 

Oladosu, 2002)23. A policy that raises revenue (an emissions tax or auctioned allowances) has a lower cost to 

the economy than a policy that does not, if the revenue 

is used to reduce existing distortionary taxes24 such as 

sales or income taxes (see, e.g., Parry et al., 1999).

4.5.3 Source Reduction Policies

Historically CO2 emissions have not been regulated directly. 

Some energy-related CO2 emissions have been regulated 

indirectly through energy policies, such as promotion of 

renewable energy, and efficiency standards and ratings for 

equipment, vehicles, and some buildings. Methane emissions 

from oil and gas production, underground coal mines, and 

landfills have been regulated, usually for safety reasons.

Policies with other objectives can have a significant impact 

on CO2 emissions. Policies to encourage production or use 

of fossil fuels, such as favorable tax treatment for fossil fuel 

production, increase CO2 emissions. Similarly, urban plans 

and infrastructure that facilitate automobile use rather than 

public transit increase CO2 emissions. In contrast, a tax on 

vehicle fuels reduces CO2 emissions25.

Carbon dioxide emissions are suited to emissions trading 

and emissions taxes. These policies allow considerable 

flexibility in the location and, to a lesser extent, the timing 

of the emission reductions26. The environmental impacts of 

22 As well, regulation is generally inferior to emissions trading or 

taxes in inducing technological change.

23 These policies encourage implementation of the lowest cost 

emission reductions available to the affected sources. They establish 

a price (the emissions tax or the market price for an allowance) for a 

unit of emissions and then allow affected sources to respond to the 

price signal. In principle, these two instruments are equivalent in 

terms of achievement of the efficient allocation of resources, but they 

may differ in terms of equity because of how the emission permits are 

initially distributed and whether a tax or subsidy is used. It is easier to 

coordinate emissions trading programs than emissions taxes across 

jurisdictions. 

24 A distortionary tax is one that changes the relative prices of goods 

or services. For example, income taxes change the relative returns 

from work, leisure, and savings.

25 Initially the reduction may be small because demand for gasoline 

is not very sensitive to price, but over time the tax causes people to 

adjust their travel patterns and the vehicles they drive, thus yielding 

larger reductions. 

26 An emissions trading program may allow participants to buy 

credits issued to entities not covered by the program for emission 

reductions or increased carbon sequestration. Determination of 
47

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

CO2 depend on its atmospheric concentration, which is not 

sensitive to the location or timing of the emissions. Apart 

from ground-level safety concerns, the same is true of CH4

emissions. In addition, the large number and diverse nature 

of the CO2 and CH4 sources means that use of such policies 

can yield significant cost savings but may also be difficult 

to implement.

Regulations setting maximum emissions on individual 

sources or efficiency standards for appliances and equipment might be preferred to emissions trading and taxes. 

Such regulations may be desirable where monitoring actual 

emissions is costly or where firms or individuals do not 

respond well to price signals due to lack of information 

or market imperfections. Energy efficiency standards for 

appliances, buildings, equipment, and vehicles tend to fall 

into this category (OECD, 2003a)27. In some cases, such as 

refrigerators, standards have been used successfully to drive 

technology development.

4.5.4 Terrestrial Sequestration Policies

To date, policies that explicitly encourage carbon sequestration in terrestrial systems have taken the form of modifying conservation programs aimed at other environmental 

objectives to include rewards for increasing carbon uptake 

by forests and agricultural soils. For example, the United 

States Department of Agriculture modified the enrollment 

criteria of the Conservation Reserve Program (CRP) and the 

Environmental Quality Incentives Program to give additional 

consideration to bids offering to install specific practices 

and technologies that sequester more carbon. The CRP also 

was modified to give landowners the right to sell carbon sequestered on lands enrolled in the program in private carbon 

markets. Policies that affect crop choice (support payments, 

crop insurance, disaster relief) and farmland preservation 

(conservation easements, use value taxation, agricultural 

zoning) may increase or reduce the carbon stock of agricultural soils. And policies that encourage higher agricultural 

output (support payments) can reduce the carbon stored by 

agricultural soils if they lead to increased tillage; such policies may increase stored carbon or be neutral with respect 

to carbon if they do not increase tillage.

A broad suite of policies are potentially available to increase 

terrestrial carbon stocks:

Regulations, such as: requirements to limit or offset carbon emissions from land-use practices, requirements to 

reforest areas that have been logged, good practice standards, and requirements to establish carbon reserves.

Market-based approaches, including: product labeling, 

the quantity of credits earned requires resolution of many issues, 

including the baseline, leakage, and additionality. 

27 The efficiency of standards sometimes can be improved by allowing 

manufacturers that exceed the standard to earn credits that can be sold 

to manufacturers that do not meet the standard.

•

•

tradable development rights, markets for terrestrial carbon28,29, and taxes on carbon emission from terrestrial 

systems.

Incentives: tax credits for good management practices, 

cost-sharing of practice costs, payment of land rents for 

set-asides, outcome oriented payments based on carbon 

stored or sequestered (Feng et al., 2003).

Education and extension: Training, technical assistance, 

guidance on best management practices, education on 

impacts of alternative management practices, recommendations, technology pilots, and efforts to address 

lack of experience, learning costs, and risk aversion 

(Sedjo, 2001; Sedjo and Swallow, 2002).

Policies to enhance terrestrial carbon sinks have significant 

potential to store additional carbon more cost effectively than 

emissions reductions in other sectors, at least for the next few 

decades (EPA, 2005). The amount of carbon that could be 

sequestered and the cost-effectiveness of this option would 

depend on the policies employed and the value placed on 

terrestrial carbon. (e.g., Marland et al., 2001).

4.5.5 Research and Development Policies

Policies to stimulate research and 

development of lower emissions 

technologies can reduce the cost 

of meeting a long-term reduction 

target. Policies to reduce CO2

emissions also influence the rate 

and direction of technological 

change (OECD, 2003a; Stern, 

2006). By stimulating additional 

technological change, such policies can reduce the cost of 

meeting a given reduction target (Goulder, 2004; Grubb et 

al., 2006; Stern, 2006). Such induced technological change 

tends to justify earlier and more stringent emission reduction 

targets (Goulder, 2004; Grubb et al., 2006).

Two types of policies are needed to ensure that available 

technologies can achieve a given cumulative CO2 reduction or concentration target at least cost. Direct support for 

research and development produces less emission-intensive 

technologies and policies to reduce emissions and increase 

sequestration create a market for those technologies. The 

combination of “research push” and “market pull” policies 

is more effective than either strategy on its own (Goulder, 

2004; CBO, 2006; Stern, 2006). Policies should encourage 

research and development for all promising technologies 

28 There needs to be a buyer for the credits, such as sources subject to 

CO2 emissions trading program or an offset requirement. 29 Since carbon sequestered in terrestrial plants and soils can be 

released from these sinks (e.g., through forest fires or a return to 

tillage), markets for terrestrial carbon may need to address the 

permanence of the carbon sequestered. A number of options are 

available to address permanence. 

•

•

The environmental impacts 

of CO2 depend on its 

atmospheric concentration, 

which is not sensitive to 

the location or timing 

of the emissions. 
The U.S. Climate Change Science Program

48 

Chapter 4

because there is considerable uncertainty about which ones 

will ultimately prove most useful, socially acceptable, and 

cost-effective30.

4.6 CONCLUSIONS 

Actions to reduce projected CO2 and CH4 concentrations in 

the atmosphere should recognize the following:

Emissions are produced by millions of diverse sources, 

most of which (e.g., power plants, factories, building 

heating and cooling systems, and large appliances) have 

lifetimes of 5 to 50 years, and so are likely to adjust only 

slowly at reasonable cost.

Potential uptake by agricultural soils and forests is 

significant but small to moderate relative to emissions 

(Chapter 11 this report) and can be reversed at any 

given location by natural phenomena or human activities. Policies to enhance and maintain terrestrial carbon 

sinks have significant potential to store additional carbon 

more cost-effectively than emissions reductions in other 

sectors, at least for the next few decades.

Technological change will have a significant impact 

on the cost because emission reductions will be implemented over a long time, and new technologies should 

lower the cost of future reductions.

Many policies implemented by national, state/provincial, 

and municipal jurisdictions and private firms to achieve 

objectives other than carbon management increase or 

reduce CO2/CH4 emissions.

Under a wide range of assumptions, policies to reduce atmospheric CO2 and CH4 concentrations cost-effectively in the 

short and long term would:

Encourage adoption of low cost emission reduction 

and sink enhancement actions. An emission trading 

program or emissions tax that covers as many sources 

and sinks as possible, combined with regulations where 

appropriate, is an example of a way to achieve this. Use 

of revenues from auctioned allowances and/or emission 

taxes could reduce the net economic cost of emission 

reduction policies.

Stimulate development of technologies that lower the 

cost of emissions reduction, carbon capture and sequestration, and sink enhancement.

Adopt appropriate regulations for sources or actions 

subject to market imperfections, such as energy 

efficiency measures and cogeneration.

Revise existing policies at the national, state/

provincial, and local level related to objectives other 

30 In other words, research and development is required for a 

portfolio of technologies. Because technologies have global markets, 

international cooperation to stimulate the research and development, 

as occurs through the International Energy Agency and the AsiaPacific Partnership on Clean Development and Climate (APP), is 

appropriate.

•

•

•

•

•

•

•

•

than carbon management so that the objectives, if 

still relevant, are achieved with lower CO2 or CH4

emissions.

Implementation of such policies at a national level, and cooperation at an international level, would reduce the overall cost 

of achieving a carbon reduction target by providing access to 

more low-cost mitigation/sequestration options.
How Can We Improve the Usefulness of 

Carbon Science for Decision Making?

CHAPTER

5

49

Coordinating Lead Authors: Lisa Dilling, Univ. Colo./NCAR; Ronald 

Mitchell, Univ. Oreg.

Lead Author: David M. Fairman, Consensus Building Inst., Inc.

Contributing Authors: Myanna Lahsen, IGBP (Brazil) and Univ. Colo.; 

Susanne Moser, NCAR; Anthony Patt, Boston Univ./IIASA; Chris Potter, 

NASA; Charles Rice, Kans. State Univ.; Stacy VanDeveer, Univ. N.H.

The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

KEY FINDINGS

• Decision makers are seeking more comprehensive information on the carbon cycle and on carbon 

management options across scales and sectors. Carbon management is a relatively new concept not only for 

decision makers and members of the public, but also for the science community.

• Improving the usefulness of carbon science in North America will require stronger commitments to generating 

high quality science that is also decision-relevant.

• Research on the production of policy-relevant scientific information suggests several ways to improve the 

usefulness of carbon science for decision making, including co-production of knowledge, development of 

applied modeling tools for decision support, and use of “boundary organizations” that can help carbon 

scientists and decision makers communicate and collaborate.

• A number of initiatives to 

improve understanding of 

decision support needs and 

options related to the carbon 

cycle are under way, some as 

a part of the Climate Change 

Science Program (CCSP).

• Additional pilot projects 

should be considered aimed 

at enhancing interactions 

between climate change 

scientists and parties involved 

in carbon management 

activities and decisions.
The U.S. Climate Change Science Program

50 

Chapter 5

5.1 INTRODUCTION: THE CHALLENGE 

OF “USABLE” CARBON SCIENCE

This chapter answers two questions:

How well is the carbon cycle science community doing 

in “decision support” of carbon cycle management, i.e., 

in responding to decision makers’ demands for carbon 

cycle management information?

How can the carbon cycle science community improve 

such decision support?

Chapters in Parts 2 and 3 of this report identify many 

research priorities, including assessing the potential for 

geological storage of carbon dioxide (CO2), quantifying expansion of the North American carbon sink, and identifying 

the economic impact of carbon tax systems. This chapter 

focuses on improving communication and collaboration 

between scientific researchers and carbon managers, to 

help researchers be more responsive to decision making, 

and carbon managers be better informed in making policy, 

investment, and advocacy decisions.

Humans have been inadvertently altering the Earth’s carbon 

cycle since the dawn of agriculture, and more rapidly since 

the industrial revolution. These influences have become 

large enough to cause significant climate change (IPCC, 

2007). In response, environmental advocates, business executives, and policy-makers have increasingly recognized 

the need to manage the carbon cycle deliberately. Effective 

carbon management requires that the variety of people 

whose decisions affect carbon emissions and sinks have relevant, appropriate science. Yet, carbon cycle science is rarely 

organized or conducted to support decision making on managing carbon emissions, uptake and storage (sequestration), 

and impacts. This reflects that, until recently, scientists have 

approached carbon cycle science as basic science and only a 

relatively small, although growing, portion of non-scientist 

decision makers have demanded carbon cycle information. 

Consequently, emerging efforts to manage carbon are less 

informed by carbon cycle science than they could be (Dilling et al., 2003). 

Applying carbon 

science to carbon management 

requires making 

carbon cycle science more useful to public and 

private decisionmakers at all levels, from national and international policymakers to the executives and employees of corporations to 

the millions of individuals whose myriad consumer and 

household decisions are central to human impacts on the 

•

•

carbon cycle. In particular, scientists and decision makers 

will need to identify the information most needed in specific 

sectors for carbon management, adjust research priorities, 

and develop mechanisms that enhance the credibility of the 

information generated and the responsiveness of the information-generating process to address stakeholder’s views 

(Lahsen and Nobre, 2007; Mitchell et al., 2006; Cash et al., 

2003). Combining some “applied” or “solutions-oriented” 

research with a portfolio that also includes basic science 

would make carbon science more directly relevant to decision making.

5.2 TAKING STOCK: WHERE ARE 

WE NOW IN PROVIDING DECISION 

SUPPORT TO IMPROVE CAPACITIES FOR 

CARBON MANAGEMENT?

How effective is the scientific community at providing 

decision support for carbon management? The Climate 

Change Science Program (CCSP) Strategic Plan defines 

decision support as: “the set of analyses and assessments, 

interdisciplinary research, analytical methods, model and 

data product development, communication, and operational 

services that provide timely and useful information to address questions confronting policymakers, resource managers, and other stakeholders” (U.S. Climate Change Science 

Program, 2003).

Who are the potential stakeholders for information related 

to the carbon cycle and what are the options and measures 

for altering human influences on that cycle? Most people 

constantly, but unconsciously, make decisions that affect 

the carbon cycle through their use of energy, transportation, 

living spaces, and natural resources. Increasing attention 

to climate change has led some policy makers, businesses, 

advocacy groups, and consumers to begin making choices 

that consciously limit carbon emissions1

. Whether carbon 

emission reductions are driven by political pressures or legal 

requirements, by economic opportunities, or consumer pressures, or by moral or ethical commitments to averting climate change, people and organizations are seeking information that can help them achieve their specific carbon-related 

or climate-related goals2. Even in countries and economic 

sectors that lack a consensus on the need to manage carbon, 

some people and organizations have begun to experiment 

with carbon-limiting practices and investments in anticipation of a carbon-constrained future.

1

 For examples, see Box 5.1

2

 For example, carbon science was presented at recent meetings 

of the West Coast Governors’ Global Warming Initiative and the 

Climate Action Registry [http://www.climateregistry.org/EVENTS/

PastConferences/; http://www.climatechange.ca.gov/events/2005_

conference/presentations/ ]

Humans have been inadvertently altering 

the Earth’s carbon cycle since the 

dawn of agriculture, and more rapidly 

since the industrial revolution. These 

influences have become large enough 

to cause significant climate change. 
51

The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

In designing and producing this report, we engaged individuals from a wide range of sectors and activities, including forestry, agriculture, utilities, fuel companies, carbon 

brokers, transportation, non-profits, and local and federal 

governments. Although we did not conduct new research on 

the informational or decision support needs of stakeholders, 

a preliminary review suggests that many stakeholders may 

be interested in carbon-related information (see Box 5.1).

5.3 CURRENT APPROACHES AND 

TRENDS

Interest in, and attention paid to, carbon information has 

increased incrementally over the last 20 years. Future levels of interest are likely to depend on perceived risks from 

carbon emissions as well as on whether and how mandatory 

and incentive-based policies related to carbon management 

evolve. As efforts at deliberate carbon management become 

increasingly common, decision makers from the local to the 

national level are increasingly open to or actively seeking 

carbon science information as a direct input to policy and 

investment decisions (Apps et al., 2003). The government 

of Canada, having ratified the Kyoto Protocol, has been exploring emission reduction opportunities and offsets and has 

identified specific needs for applied research (Environment 

Canada, 2005). For example, Canada’s national government 

recently entered a research partnership with the province of 

Alberta to assess geological sequestration of CO2, to develop 

fuel cell technologies using hydrogen, and to expand the 

use of vegetative matter (biomass) and biowaste for energy 

production (Western Economic Diversification Canada, 2006).

Some stakeholders in the United States are actively using 

carbon science to move forward with voluntary emissions 

offset programs. For example, the Chicago Climate Exchange brokers agricultural carbon credits in partnership 

with the Iowa Farm Bureau3. Many cities and several states 

have established commitments to manage carbon emissions, 

including regional partnerships on the east and west coasts, 

and non-governmental organizations and utilities have 

begun to experiment with pilot sequestration projects (Box 

5.1). In Europe, for example, mandatory carbon emissions 

policies have resulted in intense interest in carbon science 

by those directly affected by such policies (Schröter et al., 

2005).

In the United States, federal carbon science has very few 

mechanisms to assess demand for carbon information across 

scales and sectors. Thus far, federally-funded carbon science 

has focused on basic research to clarify fundamental uncertainties in the global carbon cycle and local and regional 

processes affecting the exchange of carbon (Dilling, in 

3

 http://www.iowafarmbureau.com/special/carbon/default.aspx

press). Most federal efforts are organized under 

the CCSP. The National 

Aeronautics and Space 

Administration (NASA) 

and the National Science 

Foundation (NSF) manage almost two-thirds 

of this effort and their 

missions are limited to 

basic research, not decision support (CCSP, 2006; Dilling, 2007). Research efforts 

have also been undertaken at the Department of Energy 

(DOE), the Department of Agriculture (USDA)4, and the 

Department of Interior’s Geological Survey (USGS/DOI). 

Significant technology efforts are underway in the Climate 

Change Technology Program (CCTP), a sister program to 

the CCSP focused on technology development. Increasing 

linkages among these programs may increase the usefulness of CCSP carbon-related research to decision makers. 

For over a decade, the National Oceanic and Atmospheric 

Administration (NOAA) Climate Program Office has 

invested in research and institutions intended to improve 

the usability of climate science, although that investment is 

small relative to the investment in climate science itself and 

has focused on the usability of climate, rather than carbon 

cycle, science.

Until recently, the concept of “carbon management” has not 

been widely recognized—even now, most members of the 

public do not understand the term “carbon sequestration” 

or its potential implications (Shackley et al., 2005; Curry et 

al., 2004). However, the carbon cycle science community 

is beginning to recognize that it may have information 

relevant to policy and decision making. Thus prominent 

carbon scientists have called for “coordinated rigorous, 

interdisciplinary research that is strategically prioritized to 

address societal needs” (Sarmiento and Wofsy, 1999) and the 

North American Carbon Program’s (NACP) “Implementation Plan” lists decision support as one of four organizing 

questions (Denning et al., 2005).

That same plan, however, states that the scientific community knows relatively little about the likely users of information that the NACP will produce. Indeed, the National 

Academy of Sciences’ review of the CCSP stated that “as 

the decision support elements of the program are implemented, the CCSP will need to do a better job of identifying 

stakeholders and the types of decisions they need to make” 

(NRC, 2004). Moreover, they state that “managing risks 

4

 For example, the Consortium for Agricultural Soil Mitigation of 

Greenhouse Gases (CASMGS) was recently funded by the USDA to 

provide information and technology necessary to develop, analyze, 

and implement carbon sequestration strategies.

As efforts at deliberate carbon 

management become increasingly 

common, decision makers from 

the local to the national level 

are increasingly open to or 

actively seeking carbon science 

information as a direct input to 

policy and investment decisions.
The U.S. Climate Change Science Program

52 

Chapter 5

BOX 5.1: Sectors and Stakeholders Expressing Interest and/or 

Participating in the SAP 2.2 Process

This list of sectors is neither exhaustive nor is it based on a systematically rigorous assessment, but is meant 

to demonstrate the wide variety of stakeholders with a potential interest in carbon-related information.

Agriculture: Tillage and other farming practices significantly influence carbon storage in agricultural soils. 

Managing these practices presents opportunities both to slow carbon loss and to restore carbon in soils. Farmers 

have been quite interested in carbon management as a means to stimulate rural economic activity. Since much 

of the agricultural land in the United States is privately owned, both economic forces and governmental policies 

will be critical factors in the participation of this sector in carbon management. (Chapter 10 this report).

Forestry: Forests accumulate carbon in above-ground biomass as well as soils. The carbon impact of planting, 

conserving, and managing forests has been an area of intense interest in international negotiations on climate 

change (IPCC, 2000). Whether seeking to take advantage of international carbon credits, to offset other emissions, or to simply identify environmental co-benefits of forest actions taken for other reasons, governments, 

corporations, landowners, and conservation groups may need more information on and insight into the carbon 

implications of forestry decisions ranging from species selection to silviculture, harvesting methods, and the uses 

of harvested wood. (Chapter 11 this report).

Utilities and Industries: In the United States, over 85% of energy produced comes from fossil fuels with 

relatively high carbon intensity. The capital investment and fuel source decisions of utilities and energy-intensive 

industries thus have major carbon impacts. A small but growing number of companies have made public commitments to reducing carbon emissions, developed business models that demonstrate sensitivity to climate change, 

and begun exploring carbon capture and storage opportunities. For example, Cinergy, a large Midwestern utility, 

has experimented with carbon-offset programs in partnership with The Nature Conservancy. (Chapter 6 and 

8 this report).

Transportation: Transportation accounts for approximately 37% of carbon emissions in the United States, 

and about 22% worldwide. Governmental infrastructure investments, automobile manufacturers’ decisions about 

materials, technologies and fuels, and individual choices regarding auto purchases, travel modes, and distances 

all have significant impacts on carbon emissions. (Chapter 7 this report). 

Government: In the United States, national policies currently rely primarily on voluntary measures and incentive structures (U.S. Department of State, 2004; Richards, 2004). Canada, having ratified the Kyoto Protocol, has 

direct and relatively immediate needs for information that can help it meet its binding targets as cost-effectively 

as possible (Environment Canada, 2005). The Mexican government appears to be particularly interested in locally 

relevant research on natural and human influences on the carbon cycle, likely impacts across various regions, and 

the costs, benefits, and viability of various management options (Martinez and Fernandez-Bremauntz, 2004). Below the national level, more and more states and local governments are taking steps, including setting mandatory 

policies, to reduce carbon emissions, and may need new carbon cycle science scaled to the state and local level 

to manage effectively. For example, nine New England and mid-Atlantic states have formed a regional partnership, also observed by Eastern Canadian provinces, to reduce carbon emissions through a cap and trade program 

combined with a market-based emissions trading system (Regional Greenhouse Gas Initiative—RGGI—www.

rggi.org). (Chapters 4 and 14 this report).

Non-Profits and Non-Governmental Organizations (NGOs): Many environmental and business-oriented organizations have an interest in carbon management decision making. Such organizations rely on science 

to support their positions and to undercut the arguments of opposing advocates. There has been substantial 

criticism of “advocacy science” in the science-for-policy literature, and new strategies will need to be developed 

to promote constructive use of carbon cycle science by advocates (Ehrmann and Stinson, 1999; Adler et al., 

1999).
53

The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

and opportunities requires stakeholder support on a range 

of scales and across multiple sectors, which in turn implies 

an understanding of the decision context for stakeholders” 

(NRC, 2004). Successful decision support ( i.e., science that 

improves societal outcomes) requires understanding of who 

the users are and of the kind of information they are likely 

to deem relevant and bring to bear on their decision making. 

Without such knowledge, information runs the risk of being 

“left on the loading-dock” and not used (Cash et al., 2006; 

Lahsen and Nobre, 2007).

Some programs within CCSP may shed light on how to 

link carbon science to user needs. NASA has an Applied 

Sciences program that seeks to find uses for its data and 

modeling products using “benchmarking systems,” and 

the USDA and DOE have invested significant resources in 

science that might inform carbon sequestration efforts and 

carbon accounting in agriculture and forests. However, these 

programs have not been integrated into a broader framework 

self-consciously aimed at making carbon cycle science more 

useful to decision makers.

Funding agencies, scientists, policy makers, and private 

sector managers can improve the usefulness of carbon 

science programs in North America by increasing their 

commitments to generating decision-relevant carbon cycle 

information and by integrating those programs more fully 

into forums and institutions involved in carbon cycle management. The participatory methods and boundary spanning institutions identified in the next section help both 

refine research agendas and accelerate the application of 

research results to carbon management and societal decision making.

5.4 OPTIONS FOR IMPROVING THE 

APPLICABILITY OF SCIENTIFIC 

INFORMATION TO CARBON 

MANAGEMENT AND DECISION MAKING

Studies of the creation and use of knowledge for decision 

making have found that information must be perceived not 

only as credible, but also as relevant to high priority decisions and as stemming from a process that decision makers 

view as responsive to their concerns (Mitchell et al., 2006; 

Cash et al., 2003). Even technically and intellectually 

rigorous science lacks influence with decision makers if 

decision makers perceive it as not addressing the decisions 

they face, as being biased, or as having ignored their views 

and interests. 

Research on the production of policy-relevant scientific 

information suggests several strategies that can maintain 

the integrity of the research endeavor while increasing its 

policy relevance. Although communicating results more effectively is clearly important, generating science that is more 

applicable to decision making may require deeper changes 

in the way scientific information is produced. Carbon cycle 

scientists and carbon decision makers will need to develop 

methods for interaction that work best in the specific arenas 

in which they work. At their core, strategies will be effective 

to the extent that they promote interaction among scientists 

and stakeholders in the development of research questions, 

selection of research methods, and review, interpretation, 

and dissemination of results (Adler et al., 1999; Ehrmann 

and Stinson, 1999; NRC, 1999; NRC, 2005; Farrell and 

Jaeger, 2005; Mitchell et al., 2006). Such processes work 

best when they enhance the usability of the research while 

preserving the credibility of both scientists and stakeholders. 

Transparency and expanded participation are important for 

guarding against politicization and enhancing usability. 

Examples of joint scientist-stakeholder development of 

policy relevant scientific information include:

Co-production of research knowledge (e.g., Regional 

Integrated Sciences and Assessments): In regional 

partnerships across the United States, university 

researchers work closely with local operational agencies 

and others that might incorporate climate information 

in decision making. New research is developed through 

ongoing, iterative consultations with all partners (Lemos 

and Morehouse, 2005). Co-production of research 

knowledge involves efforts to reach out to, educate, and 

involve stakeholders in programs that facilitate a dialog 

•
The U.S. Climate Change Science Program

54 

Chapter 5

of researchers and stakeholders consulting 

with and engaging each other in identifying 

near-term research questions and longer-term 

research trajectories. 

Institutional experimentation and adaptive 

behavior (e.g., adaptive management): 

Adaptive management acknowledges our 

inherent uncertainty about how natural 

systems respond to human management, 

and periodically assesses the outcomes of 

management decisions and adjusts those 

decisions accordingly, a form of deliberate 

“learning by doing” (cf., Holling, 1978). 

Adaptive management principles have 

been applied to several resources where 

multiple stakeholders are involved, including 

management of river systems and forests (Holling, 1995; 

Pulwarty and Redmond, 1997; Mitchell et al., 2004; 

Lemos and Morehouse, 2005).

Assessments as policy components (e.g., recovering 

the stratospheric ozone layer): Assessments that were 

credible, relevant, and responsive played a significant 

role in the Montreal Protocol’s success in phasing out 

the use of ozone-depleting substances. A highly credible 

scientific and technical assessment process with diverse 

academic and industry participation is considered 

crucial in the Protocol’s success (Parson, 2003).

Mediated modeling: Shared tools can facilitate 

scientist-user interactions, help diverse groups develop 

common knowledge and understanding of a problem, 

and clarify common assumptions and differences. In 

mediated modeling, participants from a wide variety 

of perspectives jointly construct a computer model to 

solve complex environmental problems or envision a 

shared future. The process has been used for watershed 

management, endangered species management, and 

other difficult environmental issues (Van den Belt, 

2004).

• Carbon modeling tools as decision support: Although 

the United States government has not yet adopted a 

carbon management policy, some federal agencies 

have begun to develop online decision support tools, 

with customizable user interfaces, to estimate carbon 

sequestration in various ecosystems and under various 

land-use scenarios (see the NASA Ames Carbon Query 

and Evaluation Support Tools, http://geo.arc.nasa.

gov/sge/casa/cquestwebsite/index.html; the U.S. Forest 

Service Carbon Online Estimator, http://ncasi.uml.

edu/COLE/;and Colorado State’s CarbOn Management 

Evaluation Tool, http://www.cometvr.colostate.edu/).

Over time, well-structured scientist-stakeholder interaction 

can help both scientists and decision makers (Moser, 2005). 

Scientists learn to identify research questions that are both 

•

•

•

scientifically interesting and relevant to decisions, and to 

present their answers in ways that audiences are more likely 

to find compelling. Non-scientists learn what questions 

science can and cannot answer. Such interactions clarify 

the boundary between empirical questions that scientists 

can answer (e.g., the sequestration potential of a particular 

technology) and issues that require political resolution (e.g., 

the appropriate allocation of carbon reduction targets across 

firms). Institutional arrangements can convert ad hoc successes in scientist-stakeholder interaction into systematic 

and ongoing networks of scientists, stakeholders, and managers. Such “co-production of knowledge,” can enhance 

both the scientific basis of policy and management and the 

research agenda for applied science (Lemos and Morehouse, 

2005; Gibbons et al., 1994; Patt et al., 2005a).

That said, such interactive approaches have limitations, 

risks, and costs. Scientists may be reluctant to involve nonscientists who “should” be interested in a given issue, but 

who can add little scientific value to the research, and whose 

involvement requires time and effort. Involving private sector firms may require scientists accustomed to working in 

an open informational environment to navigate in a world of 

proprietary information. Scientists may also avoid applied, 

participatory research if they do not see it producing the 

“cutting edge” (and career enhancing) science most valued 

by other scientists (Lahsen and Nobre, 2007; Lemos and 

Morehouse, 2005). Public and private carbon cycle science 

programs, as well as universities and research institutes, 

more generally, can help address these obstacles by recognizing that they exist and altering incentive structures 

to reward innovation in applied research through endowed 

chairs, fellowships, research grants, and the like. 

Some stakeholders may lack the financial resources, expertise, time, or other capacities necessary to meaningful 

participation. Some will distrust scientists in general, and 

government-sponsored science in particular, for cultural, 

institutional, historical, or other reasons. Some may reject 
55

The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

the idea of interacting with those with whom they disagree 

politically or compete economically. Stakeholders may try to 

manipulate research questions and findings to serve their political or economic interests. In addition, stakeholders often 

show little interest in diverting their time from other activities to what they perceive as the slow and too-often fruitless 

pursuit of scientific knowledge (Patt et al., 2005b).

Where direct stakeholder participation proves too difficult, 

costly, unmanageable, or unproductive, scientists and research managers need other methods to identify the needs 

of potential users. Science on the one hand, and policy, 

management, and decision making on the other, often exist 

as separate social and professional realms, with different 

traditions, norms, codes of behavior, and reward systems. 

The boundaries between such realms serve many useful 

functions but can inhibit the transfer of useful knowledge 

across those boundaries. A boundary organization is an 

institution that “straddles the shifting divide” between 

politics and science (Guston, 2001). Boundary organizations 

are accountable to both sides of the boundary and involve 

professionals from each. Boundary spanning individuals 

and organizations may facilitate the uptake of science by 

translating scientific findings so that stakeholders find them 

more useful and by stimulating adjustments in research 

agendas and approach.

Boundary organizations can exist at a variety of scales and 

for a variety of purposes. For example, cooperative agricultural extension services and non-governmental organizations (NGOs) successfully convert large-scale scientific 

understandings of weather, aquifers, or pesticides into locally-tuned guidance to farmers (Cash, 2001). The International Research Institute for Climate Prediction focuses on 

seasonal-to-interannual scale climate research and modeling 

to make their research results useful to farmers, anglers, 

and public health officials (e.g., Agrawala et al., 2001). The 

Subsidiary Body for Scientific and Technological Advice 

of the United Nations Framework Convention on Climate 

Change serves as an international boundary organization 

that links information and assessments from expert sources 

(such as the Intergovernmental Panel on Climate Change 

[IPCC]) to the Conference of the Parties, which focuses 

on setting policy5

. The University of California Berkeley 

Digital Library Project Calflora has explicitly designed their 

database on plants to support environmental planning (Van 

House et al., 2003).

Though attractive in principle, boundary organizations may 

not be effective in practice. They may fail to be useful if they 

are not responsive to both the stakeholders and scientists 

they seek to engage. They may be captured by one particular 

5

 http://unfccc.int/2860.php 

stakeholder or science interest. 

Their usefulness may decline 

over time if they are unable to 

keep pace with the salient issues 

of the principals on either side of 

the boundary.

Even where boundary organizations do facilitate the translation 

of scientific expertise for policy, 

other significant challenges 

exist in the use of knowledge. 

People fail to integrate new research and information in their decisions for many reasons. 

People often are not motivated to use information that supports policies they dislike or that conflicts with pre-existing 

preferences, interests, or beliefs, or with cognitive, organizational, sociological, or cultural norms (e.g., Douglas and 

Wildavsky, 1984; Lahsen, 1999; Yaniv, 2004; Lahsen, 2007). 

These tendencies are important components of a healthy 

democratic process. Developing processes to make carbon 

science more useful to decision makers will not guarantee 

its use, but will make its use more likely.

5.5 RESEARCH NEEDS TO ENHANCE 

DECISION SUPPORT FOR CARBON 

MANAGEMENT

The demand for detailed analysis of carbon management 

issues and options across major economic sectors, nations, 

and levels of government in North America is likely to grow 

substantially in the near future. This will be especially 

true in jurisdictions that place policy constraints on carbon 

budgets, such as Canada, United States’ states comprising the Regional Greenhouse Gas Initiative, or the U.S. 

State of California. Although new efforts are underway in 

some federal agencies, 

carbon cycle science in 

the United States could 

be organized and carried 

out to better and more 

systematically meet this 

potential demand. Effective implementation of 

the goals of the Climate 

Change Science Program “requires focused 

research to develop decision support resources and methods” (NRC, 2004). Relevant 

science could evaluate the impacts, technical feasibility, 

and economic potential of the wide range of existing and 

newly-developed options that are likely to be proposed in 

response to growing regional and national interest in carbon 

management.

Cooperative agricultural 

extension services 

and non-governmental 

organizations (NGOs) 

successfully convert 

large-scale scientific 

understandings of weather, 

aquifers, or pesticides 

into locally-tuned 

guidance to farmers.

Relevant science could evaluate 

the impacts, technical feasibility, 

and economic potential of 

the wide range of existing and 

newly-developed options that 

are likely to be proposed in 

response to growing interest 

in carbon management.
The U.S. Climate Change Science Program

56 

Chapter 5

Creating information for decision support should differ 

significantly from doing basic science. In such “use-inspired research,” societal need is as important as scientific 

curiosity (Stokes, 1997). Scientists and carbon managers 

need to improve their joint understanding of the top priority 

questions facing carbon-related decision making. They need 

to collaborate more effectively in undertaking research and 

interpreting results in order to answer those questions.

A first step might involve developing a formal process “for 

gathering requirements and understanding the problems 

for which research can inform decision makers outside the 

scientific community,” including forming a decision support 

working group (Denning et al., 2005). The NRC has recommended that the CCSP’s decision support components could 

be improved by organizing various deliberative activities, 

including workshops, focus groups, working panels, and 

citizen advisory groups to: “1) expand the range of decision support options being developed by the program; 2) to 

match decision support approaches to the decisions, decision 

makers, and user needs; and 3) to capitalize on the practical knowledge of practitioners, managers, and laypersons” 

(NRC, 2004).

5.6 SUMMARY AND CONCLUSIONS

The carbon cycle is influenced through both deliberate and 

inadvertent decisions by diverse and spatially dispersed 

people and organizations, working in many different sectors and at different scales. To make carbon cycle science 

more useful to decision makers, we suggest that leaders in 

the scientific and program level carbon science community 

initiate the following steps:

Identify categories of decision makers for whom 

carbon cycle science is a relevant concern, focusing on 

policy makers and private sector 

managers in carbon-intensive 

sectors (energy, transport, 

manufacturing, agriculture, 

and forestry).

Evaluate existing information 

about carbon impacts of 

actions in these arenas, and 

assess the need and demand 

for additional information. 

In some cases, demand may 

need to be fostered through an 

interactive process.

Encourage scientists and 

r e s e a r c h p r o g r a m s t o 

experiment with incremental, 

as well as major, departures 

from existing practice with 

•

•

•

the goal of making carbon cycle science more credible, 

relevant, and responsive to carbon managers.

Involve experts in the social sciences and communication 

as well as experts in physical, biological, and other 

natural science disciplines in efforts to produce usable 

science.

Consider initiating participatory pilot research projects 

and identifying existing boundary organizations (or 

establishing new ones) to bridge carbon management 

and carbon science.

•

•
PART II OVERVIEW

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

57

Energy, Industry, and Waste Management Activities: 

An Introduction to CO2 Emissions From Fossil Fuels

Coordinating Lead Author: Gregg Marland, ORNL and Mid Sweden Univ. (Östersund)

Contributing Authors: Robert J. Andres, Univ. N. Dak.; T.J. Blasing, ORNL; Thomas A. Boden, ORNL; 

Christine T. Broniak, Oreg. State Univ.; Jay S. Gregg, Univ. Md.; London M. Losey, Univ. N. Dak.; Karen 

Treanton, IEA (Paris)

II.1 The Context

Fossil fuels (coal, oil, and natural gas) are used 

primarily for their concentration of chemical energy, energy that is released as heat when the fuels 

are burned. Fossil fuels are composed primarily of 

compounds of hydrogen and carbon, and when the 

fuels are burned, the hydrogen and carbon oxidize to 

water and carbon dioxide (CO2) and heat is released. 

If the water and CO2 are released to the atmosphere, 

the water will soon fall out as rain or snow. The 

CO2, however, will increase the concentration of 

CO2 in the atmosphere and join the active cycling 

of carbon that takes place among the atmosphere, 

biosphere, and hydrosphere. Since humans began 

taking advantage of fossil-fuel resources for energy, 

we have been releasing to the atmosphere, over a 

very short period of time, carbon that was stored 

deep in the Earth over millions of years. We have 

been introducing a large perturbation to the active 

cycling of carbon.

Estimates of fossil-fuel use globally show 

that there have been significant emissions 

of CO2 dating back at least to 1750, and 

from North America, back at least to 

1785. However, this human perturbation 

of the active carbon cycle is largely a 

recent process, with the magnitude of 

the perturbation growing as population 

grows and demand for energy grows. 

Over half of the CO2 released from fossilfuel burning globally has occurred since 

1980 (Figure II.1).

Some CO2 is also released to the atmosphere during the manufacture of cement. 

Limestone (CaCO3) is heated to release 

CO2 and produce the calcium oxide (CaO) 

used to manufacture cement. In North America, cement 

manufacture now releases less than 1% of the mass of 

CO2 released by fossil-fuel 

combustion. However, cement manufacture is the 

third largest human-caused 

(anthropogenic) source of 

CO2 (after fossil-fuel use 

and the clearing and oxidation of forests and soils; see Part III this report). The CO2

emissions from cement manufacture are often included 

with the accounting of anthropogenic CO2 emissions 

from fossil fuels.

Part II of this report addresses the magnitude and pattern 

of CO2 emissions from fossil-fuel consumption and cement manufacture in North America. This introductory 

section addresses some general issues associated with 

CO2 emissions and the annual and cumulative magnitude 

of total emissions. It looks at the temporal and spatial disOver half of the CO2

released from fossil-fuel 

burning globally has 

occurred since 1980.

Figure II.1 Cumulative global emmissions of CO2 from fossil-fuel combustion and cement manufacture from 1751 to 2002. Source data: Marland 

et al. (2005).
The U.S. Climate Change Science Program Part II Overview

58 

tribution of emissions and other data likely to be of interest. 

The following four chapters delve into the sectoral details 

of emissions so that we can understand the forces that have 

driven the growth in emissions to date and the possibilities 

for the magnitude and pattern of emissions in the future. 

These chapters reveal, for example, that 38% of CO2 emissions from North America come from enterprises whose 

primary business is to provide electricity and heat and another 31% come from the transport of passengers and freight. 

This introduction focuses on the total emissions from the use 

of fossil fuels and the subsequent chapters provide insight 

into how these fuels are used and the economic and human 

factors motivating their use.

II.1.1 Estimating Carbon Dioxide Emissions

It is relatively straightforward to estimate the amount of CO2

released to the atmosphere when fossil fuels are consumed. 

Because CO2 is the equilibrium product of oxidizing the carbon in fossil fuels, we need to know only the amount of fuel 

used and its carbon content. For greater accuracy, we adjust 

this estimate to take into consideration the small amount of 

carbon that is left as ash 

or soot and is not actually 

oxidized. We also consider 

the fraction of fossil fuels 

that are used for things 

like asphalt, lubricants, 

waxes, solvents, and 

plastics and may not be soon converted to 

CO2. Some of these long-lived, carbon-containing products will release their contained 

carbon to the atmosphere as CO2 during use 

or during processing of waste. Other products 

will hold the carbon in use or in landfills for 

decades or longer. One of the differences 

among the various estimates of CO2 emissions is the way they deal with the carbon in 

these products. 

Fossil-fuel consumption is often measured 

in mass or volume units and, in these terms, 

the carbon content of fossil fuels is quite variable. However, when we measure the amount 

of fuel consumed in terms of its energy 

content, we find that for each of the primary 

fuel types (coal, oil, and natural gas) there 

is a strong correlation between the energy 

content and the carbon content. The rate of 

CO2 emitted per unit of useful energy released depends on 

the ratio of hydrogen to carbon and on the details of the 

organic compounds in the fuels; but, roughly speaking, 

the numerical conversion from energy released to carbon 

released as CO2 is about 25 kg C per 109 joules for coal, 20 

kg C per 109 joules for petroleum, and 15 kg C per 109 joules 

for natural gas. Figure PII.2 shows details of the correlation 

between energy content and carbon content for more than 

1000 coal samples. Detailed analysis of the data suggests 

that hard coal contains 25.16 ± 2.09% kg C per 109 joules 

of coal (measured on a net heating value basis1). The value 

is slightly higher for lignite and brown coal (26.23 kg C ± 

1

 Net heating value (NHV) is the heat release measured when fuel is 

burned at constant pressure so that the water (H2O) is released as H2O 

vapor. This is distinguished from the gross heating value (GHV), the 

heat release measured when the fuel is burned at constant volume so 

that the H2O is released as liquid H2O. The difference is essentially 

the heat of vaporization of the H2O and is related to the hydrogen 

content of the fuel.

Fuel Emissions coefficient 

(kg C/109

 J net heating value) 

Lignite 27.6

Anthracite 26.8

Bituminous coal 25.8

Crude oil 20.0

Residual fuel oil 21.1

Diesel oil 20.2

Jet kerosene 19.5

Gasoline 18.9

Natural gas 15.3

Table II.1 A sample of the coefficients used for estimating CO2 emissions from the amount of fuel burned.

Source: IPCC (1997).

Figure II.2 The carbon content of coal varies with the heat content, shown 

here as the net heating value. To make them easier to distinguish, data for lignites and brown coals are shown on the left axis, while data for hard coals are 

offset by 20% and shown on the right axis. Heating value is plotted in the units 

at which it was originally reported, Btu/lb, where 1 Btu/lb = 2324 J/kg. Source: 

Marland et al. (1995).

It is relatively 

straightforward to estimate 

the amount of CO2 released 

to the atmosphere when 

fossil fuels are consumed.
59

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

2.33% per 109 joules (also shown in Figure II.2). 

Similar correlations exist for all fuels and Table 

PII.1 shows some of the coefficients reported by 

the Intergovernmental Panel on Climate Change 

(IPCC) for estimating CO2 emissions. The differences between the values in Table II.1 and those 

in Figure II.2 are small, but they begin to explain 

how different data compilations can end up with 

different estimates of CO2 emissions. 

Data on fossil-fuel production, trade, consumption, etc. are generally collected at the level of 

some political entity, such as a country, and over 

some time interval, typically a year. Estimates 

of national, annual fuel consumption can be 

based on estimates of fuel production and trade, 

estimates of actual final consumption, data for 

fuel sales or some other activity that is clearly 

related to fuel use, or on estimates and models of 

the activities that consume fuel (such as vehicle 

miles driven). In the discussion that follows, some estimates 

of national, annual CO2 emissions are based on “apparent 

consumption” (defined as production + imports – exports 

+/– changes in stocks), while others are based on more direct 

estimates of fuel consumption. All of the emissions estimates in this chapter are as the mass of carbon released2

. 

The uncertainty in estimates of CO2 emissions will thus 

depend on the variability in the chemistry of the fuels, the 

quality of the data or models of fuel consumption, and on uncertainties in the amount of carbon that is used for non-fuel 

purposes (such as asphalt and plastics) or is otherwise not 

burned. For countries like the United States—with good data 

on fuel production, trade, and consumption—the uncertainty 

in national emissions of CO2 is on the order of ±5% or less. 

In fact, the U.S. Environmental Protection Agency (USEPA, 

2005) suggests that their estimates of CO2 emissions from 

energy use in the United States are accurate, at the 95% 

confidence level, within –1 to +6% and Environment Canada 

(2005) suggests that their estimates for Canada are within –4 

to 0%. The Mexican National Report (Mexico, 2001) does 

not provide estimates of uncertainty, but our analyses with 

the Mexican data suggest that uncertainty is larger than for 

the United States and Canada. Emissions estimates for these 

same three countries, as reported by the Carbon Dioxide 

Information Analysis Center (CDIAC) and the International 

Energy Agency (IEA) (see the following section), will have 

larger uncertainty because these groups are making estimates for all countries. Because they work with data from 

2

 The carbon is actually released to the atmosphere as CO2 and it is 

accurate to report (as is often done) either the amount of CO2 emitted 

or the amount of C in the CO2. The numbers can be easily converted 

back and forth using the ratio of the molecular masses, i.e. (mass of 

C) x (44/12) = (mass of CO2).

all countries, they use global average values for things like 

the emissions coefficients, whereas agencies within the 

individual countries use values that are more specific to the 

particular country. When national emissions are calculated 

by consistent methods it is likely that year-to-year changes 

can be estimated more accurately than would be suggested 

by the uncertainties of the individual annual values.

II.1.2 The Magnitude of National and 

Regional Carbon Dioxide Emissions

Figure II.3 shows that from the beginning of the fossil-fuel 

era (1751 in these graphs) to the end of 2002, there were 93.5 

billion tons of carbon (Gt C) released as CO2 from fossil-fuel 

consumption (and cement manufacture) in North America: 

84.4 Gt C from the United States, 6.0 from Canada, and 3.1 

from Mexico. All three countries of North America are major users of fossil fuels and this 93.5 Gt C was 31.5% of the 

global total. Among all countries, the United States, Canada, 

and Mexico ranked as the first, eighth, and eleventh largest 

emitters of CO2 from fossil-fuel consumption, respectively 

(for 2002) (Marland et al., 2005). Figure II.4 shows, for each 

of these countries and for the sum of the three, the annual 

total of emissions and the contributions from the different 

fossil fuels. 

The long time series of emissions estimates in Figures II.1, 

II.3, and II.4 are from the CDIAC (Marland et al., 2005). 

These estimates are derived from the “apparent consumption” of fuels and are based on data from the United Nations 

Statistics Office back to 1950 and on data from a mixture 

of sources for the earlier years (Andres et al., 1999). There 

are other published estimates (with shorter time series) 

of national, annual CO2 emissions. Most notably the IEA 

(2005) has reported estimates of emissions for many counFigure II.3 The cumulative total of CO2 emissions from fossil-fuel consumption 

and cement manufacture, as a function of time, for the three countries of North 

America and for the sum of the three. Source: Marland et al. (2005). 
The U.S. Climate Change Science Program Part II Overview

60 

tries for all years back to 1971, and most countries have 

now provided some estimates of their own emissions as 

part of their national obligations under the United Nations 

Framework Convention on Climate Change (UNFCCC, 

see http://unfccc.int). These latter two sets of estimates are 

based on data on actual fuel consumption and thus are able 

to provide details as to the sector of the economy where 

fuel use is taking place3. 

Comparing the data from 

multiple sources can give 

us some insight into the 

reliability of the estimates, 

generally. These different 

estimates of CO2 emissions 

are not, of course, truly independent because they all rely, 

ultimately, on national data on fuel use; but they do represent 

3

 The International Energy Agency provides estimates based on both 

the reference approach (estimates of apparent consumption) and the 

sectoral approach (estimates of actual consumption) as described by 

the IPCC (IPCC, 1997). In the comparison here, we use the numbers 

that they believe to be the most accurate, those based on the sectoral 

approach.

different manipulations of this primary data and in many 

countries there are multiple potential sources of energy 

data. Many developing countries do not collect or do not 

report all of the data necessary to precisely estimate CO2

emissions and in these cases differences can be introduced 

by how the various agencies derive the basic data on fuel 

production and use. Because of the way data are collected, 

there are statistical differences between “consumption” and 

“apparent consumption” as defined above.

To make comparisons of different estimates of CO2 emissions we would like to be sure that we are indeed comparing 

estimates of the same thing. For example, emissions from 

cement manufacture are not available from all of the sources, 

so they are not included in the comparisons in Table II.2. All 

of the estimates in Table II.2, except those from the IEA, 

include emissions from flaring natural gas at oil production facilities. It is not easy to identify the exact reason the 

estimates differ, but the differences are generally small. The 

differences have mostly to do with the statistical difference 

between consumption and apparent consumption, the way 

in which correction is made for non-fuel usage of fossil-fuel 

resources, the conversion from mass or volume to energy 

Figure II.4 Annual emissions of CO2 from fossil-fuel use by fuel type for (A) the United States, (B) Canada, (C) Mexico, and (D) 

North America, as the sum of the data shown in the other three panels. Note that in order to illustrate the contributions of the 

different fuels, the four plots are not to the same vertical scale. Source: Marland et al. (2005). 

All three countries of North 

America are major users of 

fossil fuels and this 93.5 Gt C 

was 31.5% of the global total.
61

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

units, and/or the way in which estimates of carbon content 

are derived. Because the national estimates from CDIAC do 

not include emissions from the non-fuel uses of petroleum 

products, we expect them to be slightly smaller than the 

other estimates shown here, all of which do include these 

emissions4. The comparisons in Table II.2 reveal one number 

for which there is a notable relative difference among the 

multiple sources, emissions from Mexico in 1990. Losey 

(2004) has suggested, based on other criteria, that there is 

a problem in the United Nations energy data set with the 

Mexican natural gas data for the three years 1990-1992, and 

these kinds of analyses result in re-examination of some of 

the fundamental data.

The IEA (2005, p. 1.4) has systematically compared their estimates with those reported to the 

UNFCCC by the different countries and they 

find that the differences for most developed 

countries are within 5%. The IEA attributes 

most of the differences to the following: use of 

the IPCC Tier 1 method that does not take into 

account different technologies, use of energy 

data that may have come from different “official” sources within a country, use of average 

values for net heating value of secondary oil 

products, use of average emissions values, use 

of incomplete data on non-fuel uses, different 

treatment of military emissions, and a different 

split between what is identified as emissions 

4

 The CDIAC estimate of global total emissions does include estimates 

of emissions from oxidation from non-fuel use of hydrocarbons.

from energy and emissions 

from industrial processes.

II.1.3 Emissions by Month 

and/or State

With increasing interest in the 

details of the global carbon 

cycle there is increasing interest 

in knowing emissions at spatial 

and temporal scales finer than 

countries and years. For the 

United States, energy data have 

been collected for many years 

at the level of states and months 

and thus estimates of CO2 emissions can be made by state or 

by month. Figure II.5 shows 

the variation in United States’ 

emissions by month and preliminary analyses by Gurney 

et al. (2005) reveal that proper 

recognition of this variability 

can be very important in some 

exercises to model the details of the global carbon cycle. 

Because of differences in the way energy data are collected and aggregated, it is not obvious that an estimate of 

emissions from the United States will be identical to the 

sum of estimates for the 50 United States’ states. Figure 

II.6 shows that estimates of total annual CO2 emissions 

are slightly different if we use data directly from the U.S. 

Department of Energy (DOE) and sum the estimates for 

the 50 states or if we sum the estimates for the 12 months 

of a given year, or if we take United States’ energy data 

as aggregated by the United Nations Statistics Office and 

calculate the annual total of CO2 emissions directly. Again, 

Figure. II.5 Emissions of CO2 from fossil-fuel consumption in the 

United States, by month. Emissions from cement manufacturing are 

not included. Source: Blasing et al. (2005a).

Notes:

Many of these data were published in terms of the mass of CO2, and these data have been

multiplied by 12/44 to get the mass of carbon for the comparison here. 

All data except CDIAC include oxidation of non-fuel hydrocarbons.

All data except IEA include flaring of gas at oil and gas processing facilities.

Sources: CDIAC (Marland et al., 2005), IEA (2005), USEPA (2005), Canada

(Environment Canada, 2005), and Mexico (2001).

Country 1990 1998 2002

United States CDIAC 1305 CDIAC 1501 CDIAC 1580

IEA 1320 IEA 1497 IEA 1545

USEPA 1316 USEPA 1478 USEPA 1534

Canada CDIAC 112 CDIAC 119 CDIAC 139

IEA 117 IEA 136 IEA 145

Canada 117 Canada 133 Canada 144

Mexico CDIAC 99 CDIAC 96 CDIAC 100

IEA 80 IEA 96 IEA 100

Mexico 81 Mexico 96 Mexico NA

Table II.2 Different estimates (in MtC) of CO2 emissions from fossil-fuel 

consumption for the United States, Canada, and Mexico.
The U.S. Climate Change Science Program Part II Overview

62 

the state and monthly emissions data are based on estimates 

of fuel consumption while the national emissions estimates 

calculated using United Nations’ data result from estimates 

of “apparent consumption.” There is a difference between 

annual values for consumption and annual values of “apparent consumption” (the IEA calls this difference simply 

“statistical difference”) that is related to the way statistics 

are collected and aggregated. There are also differences in 

the way values for fuel chemistry and non-fuel usage are 

averaged at different spatial and temporal scales, but the 

differences in CO2 estimates are seen to be within the error 

bounds generally expected.

Data from DOE permit us to estimate emissions by state 

or by month (Blasing et al., 2005a and 2005b), but they do 

not permit us to estimate CO2 emissions for each state by 

month directly from the published energy data. Nor do we 

have sufficiently complete data to estimate emissions from 

Canada and Mexico by month or province. Andres et al. 

(2005), Gregg (2005), and Losey (2004) have shown that 

we can disaggregate national 

total emissions by month or by 

some national subdivision (such 

as states or provinces) if we 

have data on some large fraction of fuel use. Because this 

approach relies on determining 

the fractional distribution of an 

otherwise-determined total, it 

can be done with incomplete 

data on fuel use. The estimates 

will, of course, improve as the 

fraction of the total fuel use is increased. Figure II.7 is 

based on sales data for most fossil-fuel commodities and the 

CDIAC estimates of total national emissions and shows how 

the CO2 emissions from North America vary at a monthly 

time scale.

.II.1.4 Emissions by Economic Sector

To understand how CO2 emissions from fossil-fuel use 

interact in the global and regional cycling of carbon, it is 

necessary to know the masses of emissions and their spatial 

and temporal patterns. We have tried to summarize this 

information here. To understand the trends and the driving 

forces behind the growth in fossil-fuel emissions, and the 

opportunities for controlling emissions, it is necessary to 

look in detail at how the fuels are used. This is the goal of 

the next four chapters of this report. 

Before looking at the details of how energy is used and 

where CO2 emissions occur in the economies of North 

America, however, there are two indices of CO2 emissions 

at the national level that provide perspective on the scale 

and distribution of emissions. These two indices are emisFigure II.7 Carbon dioxide emissions from fossil-fuel consumption in North America, by month. Monthly values are shown 

where estimates are justified by the availability of monthly data 

on fuel consumption or sales. Source: Andres et al., (2005).

To understand the trends 

and the driving forces 

behind the growth in 

fossil-fuel emissions, and 

the opportunities for 

controlling emissions, it is 

necessary to look in detail 

at how the fuels are used.

Figure. II.6 A comparison of three different estimates of national annual emissions of CO2 from fossil-fuel consumption in the 

United States. (A) Estimates from U.S. Department of Energy data on fuel consumption by state (blue squares) vs. estimates based 

on UN Statistics Office data on apparent fuel consumption for the full United States (red squares). (B) Estimates based on DOE 

data on fuel consumption in the 50 U.S. states (blue squares) vs. estimates based on national fuel consumption for each of the 12 

months (red squares). The state and monthly data include estimates of oxidation of non-fuel hydrocarbon products; the UN-based 

estimates do not. Source: Blasing et al., (2005b). 
63

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

Figure II.8 Per capita emissions of CO2 from fossil-fuel consumption and cement 

manufacture in the United States, Canada, and Mexico and for the global total of 

emissions. Source: Marland et al., (2005).

sions per capita and emissions per unit of economic activity, 

the latter generally represented by CO2 per unit of gross 

domestic product (GDP). Figure II.8 shows the 1950–2002 

record of CO2 emissions per capita for the three countries 

of North America and for perspective includes the same data 

for the Earth as a whole. Similarly, Table II.3 shows CO2

emissions per unit of GDP for the three countries of North 

America and for the world total. These are, of course, very 

complex indices and though they provide some insight they 

say nothing about the details and the distributions within the 

means. The data on CO2 per capita for the 50 United States’ 

states (Figure II.9) show that values range over a full order 

of magnitude, differing in complex ways with the structure 

of the economies and probably with factors like climate, 

population density, and access to resources (Blasing et al., 

2005b; Neumayer, 2004).

Chapters 6 through 9 of this report 

discuss the patterns and trends of 

CO2 emissions by sector and the driving forces behind the trends that are 

observed. Estimating emissions by 

sector brings special challenges in 

defining sectors and assembling the 

requisite data. Readers will find that 

there is consistency and coherence 

within each of the following chapters 

but will encounter difficulty in aggregating or summing numbers across 

chapters. Different experts use different sector boundaries, different data 

sources, different conversion factors, 

etc. Different analysts and literature 

sources will find data for different 

base years and may treat electricity 

and biomass fuels differently. The 

national reports of the United States, 

Canada, and Mexico do not cover the 

same time periods, nor do they present 

data in the same way. In a discussion 

of the possibilities for reducing CO2

emissions in the building sector it is 

not obvious, for example, whether to 

include the relevant electricity within 

the building sector, to leave electric 

power generation as a separate sector, or to accept some overlap in the 

discussion. The authors of Chapters 

6, 7, 8, and 9 have chosen the system 

boundaries and data they find most 

useful for the individual sectors, even 

though it makes it more difficult to 

aggregate across sectors.

Despite these differences in accounting procedures, the four 

chapters that follow accurately characterize the patterns of 

emissions and the opportunities for controlling the growth 

in emissions. They reveal that there are major differences 

between the countries of 

North America where, for 

example, the United States 

derives 51% of its electricity 

from coal, Mexico gets 68% 

from petroleum and natural 

gas, and Canada gets 58% 

from hydroelectric stations. 

Partially as a ref lection 

of this difference, 40% of 

United States’ CO2 emissions are from enterprises whose primary business is to generate electricity and heat, while this number is only 31% in 

Forty percent of the United 

States’ CO2 emissions are 

from enterprises whose 

primary business is to 

generate electricity and heat, 

while this number is only 31% 

in Mexico and 23% in Canada.

Country

CO2 emissions per unit of GDPa

Year

1990 1998 2002

United States 0.19 0.17 0.15

Canada 0.18 0.18 0.16

Mexico 0.13 0.12 0.11

Global Total 0.17 0.15 0.14

a Carbon dioxide is measured in kg carbon and GDP is reported

in 2000 US$ purchasing power parity.

Source: IEA (2005).

Table II.3 Emissions of CO2 from fossil-fuel consumption (cement manufacture and gas flaring are not included) per unit of GDP for the United 

States, Canada, Mexico and for the global total.
The U.S. Climate Change Science Program Part II Overview

64 

Mexico and 23% in Canada (for 2003; 

from IEA, 2005). Chapter 8 reveals 

that the sectors are not independent 

as, for example, a change from fuel 

burning to electricity in an industrial 

process will decrease emissions from 

the industrial sector but increase 

emissions in the electric power sector. The database of the IEA allows us 

to summarize CO2 emissions for the 

three countries according to sectors 

that closely correspond to the sectoral division of chapters 6 through 

9 (Table II.4). 

II.2 Conclusion

There are a variety of reasons that we 

want to know the emissions of CO2

from fossil fuels, there are a variety 

of ways of coming up with the desired 

estimates, and there are a variety of 

ways of using the estimates. By the 

nature of the process of fossil-fuel 

combustion, and because of its economic importance, there are reasonably good data over long time intervals that we can use to 

make reasonably accurate estimates of CO2 emissions to 

the atmosphere. In fact, it is the economic importance of 

fossil-fuel burning that has assured us of both good data 

on emissions and great challenges in altering the rate of 

emissions.

Figure II.9 Per capita emissions of CO2 from fossil-fuel consumption for the 50 United 

States in 2000. To demonstrate the range, values have been rounded to whole numbers of metric tons carbon per capita. A large portion of the range for extreme values 

is related to the occurrence of coal resources and inter-state transfers of electricity. 

Source: Blasing et al. (2005b).

a The sum of three IEA categories, “public electricity and heat production,”

“unallocated autoproducers,” and “other energy industries.” 

b IEA category “transport.”

c IEA category “manufacturing industries and construction.”

d IEA category “other sectors.”

Source: IEA (2005).

Sector United States Canada Mexico North America

Energy extraction and conversiona 46.2 36.2 47.7 45.4

Transportationb 31.3 27.7 30.3 31.0

Industryc 11.2 16.8 13.6 11.8

Buildingsd 11.3 19.3 8.4 11.8

Table II.4 Percentage of CO2 emissions by sector for 2003.
Energy Extraction and Conversion

CHAPTER

6

65

Lead Author: Thomas J. Wilbanks, ORNL 

Contributing Authors: Marilyn Brown, Ga. Inst. Tech.; Ken Caldeira, 

Carnegie Inst.; William Fulkerson, Univ. Tenn.; Erik Haites, Margaree 

Consultants, Inc; Stephen Pacala, Princeton Univ.; David M. Fairman, 

Consensus Building Inst., Inc.

The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

KEY FINDINGS

• In recent years, the extraction of primary energy sources and their conversion into energy commodities in North America 

released on the order of 760 million tons of carbon (2800 million tons of carbon dioxide) per year to the atmosphere, 

approximately 40% of total North American emissions in 2003 and 10% of total global emissions. Electricity generation 

is responsible for a very large share of North America's energy extraction and conversion emissions.

• Carbon dioxide emissions from energy supply systems in North America are currently rising.

• Principal drivers behind carbon emissions from energy supply systems are (1) the growing appetite for energy services, 

closely related to economic and social progress, and (2) the market competitiveness of fossil energy compared with 

alternatives.

• Emissions from energy supply systems in North America are projected to increase in the future. Projections vary among 

the countries, but increases approaching 50% or more in coming decades appear likely. Projections for the United States, 

for example, indicate that carbon dioxide emissions from electricity generation alone will rise to above 900 million tons 

of carbon (3300 million tons of carbon dioxide) by 2030, an increase of about 45% over emissions in 2004, with threequarters of the increase associated with greater coal use in electric power plants.

• Prospects for major reductions in carbon 

dioxide emissions from energy supply 

systems in North America appear dependent 

upon (a) the extent, direction, and pace of 

technological innovation and (b) whether 

policy conditions favoring carbon emissions 

reduction that do not now exist will emerge 

(Figure 6.1). In these regards, the prospects 

are brighter in the long term (e.g., more than 

several decades in the future) than in the 

near term.

• Research and development priorities for 

managing carbon emissions from energy 

supply systems include, on the technology 

side, clarifying and realizing potentials for 

carbon capture and storage, and on the policy 

side, understanding the public acceptability 

of policy incentives for reducing dependence 

on carbon-intensive energy sources. Figure 6.1 Prospects for carbon emissions from energy extraction and 

conversion in North America, assuming substantial improvement in energy 

efficiency. 
The U.S. Climate Change Science Program

66 

Chapter 6

6.1 INTRODUCTION

The energy supply system in North America is a significant 

part of the North American carbon cycle, because so many of 

its primary energy resources are fossil fuels associated with 

extraction and conversion activities that emit greenhouse 

gases. This chapter summarizes the knowledge bases related 

to emissions from energy extraction, energy conversion, and 

other energy supply activities such as energy movement and 

energy storage, along with options and measures for managing emissions.

Clearly, this topic overlaps the subject matter of other chapters. For instance, the dividing line between energy conversion and other types of industry is sometimes indistinct. 

One prominent case is emissions associated with electricity 

and process heat supply for petroleum refining, and other 

fossil-fuel processing (a large share of their total emissions) 

included in industrial 

sector emission totals; 

another example is industrial co-generation as an 

energy-efficiency strategy. In addition, biomass 

energy extraction/conversion is directly related to 

agriculture and forestry. Moreover, emission-related policy 

alternatives for energy supply systems are often directed at 

both supply and demand responses, involving not only emission reductions, but also potential payoffs from efficiency 

improvements in buildings, industry, and transportation, especially where they reduce the consumption of fossil fuels.

6.2 CARBON EMISSIONS 

INVENTORY

6.2.1 Carbon Emissions From 

Energy Extraction and Conversion

Carbon emissions from energy resource extraction, conversion into energy commodities, and transmission are one of the 

“big three” sectors accounting for most of the total emissions 

from human systems in North America, along with industry 

and transportation. The largest share of total emissions from 

energy supply (not including energy end use) is from coal 

and other fossil-fuel use in producing electricity; fossil-fuel 

conversion activities such as oil refining and natural gas 

transmission and distribution also contribute to this total, but 

in much smaller amounts. Other emission sources are less 

well defined, but generally small, such as emissions from oil 

production and methane from reservoirs established partly to 

support hydropower production (Tremblay et al., 2004), or 

from materials production (e.g., metals production) associated with other renewable or nuclear energy technologies. 

Generally, data on emissions have a relatively low level of 

uncertainty, although the source materials do not include 

quantitative estimates of uncertainty.

Data on emissions from energy supply systems are unevenly 

available for the countries of North America, and none are 

associated with sufficient information to support an assessment of uncertainty. Most emission data sets are organized by 

fuel consumed rather than by consuming sector, and countries 

differ in sectors identified and the units of measurement. As 

a result, inventories are reported in this chapter by country 

in whatever forms are available rather than constructing a 

North American inventory that could not be consistent across 

all three major countries. It is worth noting that Canada and 

Mexico export energy supplies to the United States, therefore, 

some emissions from energy supply systems in these countries are associated with energy uses in the United States.

 6.2.1.1 CANADA

Canada is the world’s fifth-largest energy producing country, 

a significant exporter of both natural gas and electricity to the 

United States. In Alberta, which produces nearly two-thirds 

of Canada’s energy, energy accounts for about one-quarter of 

the province’s economic activity; its oil sands are estimated 

to have more potential energy value than the remaining 

oil reserves of Saudi Arabia (U.S. Department of Energy, 

2004). Although Canada has steadily reduced its energy and 

carbon intensities since the early 1970s, its overall energy 

intensity remains high—in part due to its prominence as an 

energy producer—and total greenhouse gas emissions have 

grown by 9% since 1990. As of 2003, greenhouse gas emissions were 36.5 million 

metric tons of carbon (Mt 

C) equivalents (134 million tons of carbon dioxide 

[Mt CO2] equivalents) for 

electricity and heat generation and 19 Mt C (71 

Mt CO2) for petroleum 

refining and upgrading and 

other fossil-fuel production (Environment Canada, 

2003). Although the mix of 

Canada is the world’s fifthlargest energy producing 

country, a significant exporter of 

both natural gas and electricity 

to the United States.

BOX 6.1: CCSP SAP 2.2 Uncertainty Conventions

***** = 95% certain that the actual value is within 10% of the estimate reported, 

  = 95% certain that the estimate is within 25%, 

** * = 95% certain that the estimate is within 50%, 

** = 95% certain that the estimate is within 100%, and

* = uncertainty greater than 100%.

† = The magnitude and/or range of uncertainty for the given numerical 

 value(s) is not provided in the references cited.
67

The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

carbon dioxide (CO2) and methane (CH4) in these figures is 

unclear, the carbon emission equivalent is probably within 

the range of 60-80 Mt C.

6.2.1.2 Mexico

Mexico is one of the largest sources of energy-related 

greenhouse gas emissions in Latin America, although its 

per capita emissions are well below the per capita average 

of industrialized countries. The first large oil-producing 

nation to ratify the Kyoto Protocol, it has promoted shifts 

to natural gas use to reduce greenhouse gas emissions. The 

most recent emission figures are from the country’s Second 

National Communication to the United Nations Framework 

Convention on Climate Change (UNFCCC) in 2001, which 

included relatively comprehensive data from 1996 and 

some data from 1998. In 1998, total emissions from “energy 

industries” were 13 Mt C (47.3 Mt CO2); from electricity 

generation they totaled 27.6 Mt C (101.3 Mt CO2); and “fugitive” emissions from oil and gas production and distribution 

were between 1.4 and 2.0 Mt C (1.9 and 2.6 Mt of CH4), 

depending on the estimated “emission factor” (Government 

of Mexico, 2001).

6.2.1.3 United States

The United States is the largest national emitter of greenhouse gases in the world, and CO2 emissions associated with 

electricity generation in 2004 account for 627 Mt C (2299 

Mt CO2), or 39% of a national total of 1600 Mt C (5890 Mt 

CO2) (EIA, 2006a). Greenhouse gases are also emitted from 

oil refining, natural gas transmission, and other fossil energy 

supply activities, but apart from energy consumption figures 

included in industry sector calculations, these emissions are 

relatively small compared with electric power plant emissions. For instance, emissions from petroleum consumed 

in refining processes in the United States are about 40 Mt 

C per year (EIA, 2004), while fugitive emissions from gas 

transmission and distribution pipelines in the United States 

are about 2.2 Mt C per year1**(see Box 6.1 for uncertainty 

conventions). On the other hand, a study of greenhouse gas 

emissions from a six-county area in southwestern 

Kansas found that compressor stations for natural 

gas pipeline systems are a significant source of 

emissions at that local scale (AAG, 2003).

6.2.2 Carbon Sinks Associated With 

Energy Extraction and Conversion

Generally, energy supply in North America is based 

heavily on mining hydrocarbons from carbon sinks 

accumulated over millions of years; but current carbon sequestration occurs in plant growth, including 

the cultivation of feedstocks for bioenergy production. Limited strictly to energy sector applications, 

 This numerical value represents the authors’ estimate.

the total contribution 

of these sinks to the 

North American carbon 

cycle is relatively small, 

while other aspects of 

bioenergy development 

are associated with carbon emissions; but the substitution of biomass-derived fuels 

(approximately emisson-neutral, as stored carbon is released 

with fuel use) for fossil fuels represents a potentially significant net savings in emissions.

6.3 TRENDS AND DRIVERS

Three principal drivers are behind carbon emissions from 

energy extraction and conversion:

The growing global and national appetite for energy 

services such as comfort, convenience, mobility, and 

labor productivity, so closely related to progress with 

economic and social development and the quality of 

life (Wilbanks, 1992). Globally, the challenge is to 

increase total energy services (not necessarily supplies) over the next half-century by a factor of at least 

three or four—more rapidly than overall economic 

growth—while reducing environmental impacts from 

the associated supply systems (NAS, 1999). Mexico 

shares this need, while increases in Canada and the 

United States are likely to be more or less proportional 

to rates of economic growth.

The market competitiveness of fossil energy sources 

compared with supply- and demand-side alternatives. 

Production costs of electricity from coal, oil, or natural 

gas at relatively large scales are currently lower than 

other sources, except large-scale hydropower, and production costs of liquid and gas fuels are currently far 

lower than other sources, though rising. This is mainly 

because the energy density and portability of fossil fuels 

is as yet unmatched by other energy sources, and in some 

cases policy conditions reinforce fossil-fuel use. These 

1.

2.

The substitution of 

biomass-derived fuels for fossil 

fuels represents a potentially 

significant net savings in emissions.
The U.S. Climate Change Science Program

68 

Chapter 6

conditions appear likely to 

continue for some years. In 

many cases, the most costcompetitive alternative to 

fossil-fuel production and 

use is not alternative supply 

sources, but efficiency improvement.

Enhanced future markets 

for alternative energy supply sources. In the longer 

run, however, emissions 

from energy supply systems 

may—and in fact, are likely 

to—begin to decline as alternative technology options are 

developed and/or improved. 

Other possible driving forces 

for attention to alternatives 

to fossil fuels, at least in the 

mid to longer term, include the possibility of shrinking 

oil and/or gas reserves and changes in attitudes toward 

energy policy interventions.

Given the power of 

the first two of these 

drivers, total carbon emissions from energy extraction and 

conversion in North America are currently rising (e.g., Figure 

6.2). National trends and drivers are as follows. As is always 

the case, projections of the future involve higher levels of 

uncertainty than measurements of the present, but source 

materials do not include quantitative estimates of uncertainties associated with projections of future emissions.

6.3.1 Canada

Canada has ratified the Kyoto Protocol, and it is seeking to 

meet the Kyoto target of CO2 emission reduction to 6% below 1990 levels. Of these reductions, 25% are to be through 

domestic actions and 75% through market mechanisms such 

as purchases of carbon credits (Government of Canada, 

2005). Domestic actions will include a significant reduction 

in coal consumption. Available projections, however, indicate a total national increase of emissions in CO2 equivalent 

of 36.1% by 2020 from 1990 levels (Environment Canada, 

2005). Emissions from electricity generation could increase 

2000-2020 by as much as two-thirds, while emissions from 

fossil-fuel production 

would remain relatively 

stable (although substantial expansion of oil 

sands production could 

be a factor).

3.

Figure 6.2 U.S. carbon dioxide emissions from electricity generation, 1990-2004. 

Source: EIA, 2004, and the authors’ extensions for year 2004. 

6.3.2 Mexico

It has been estimated that total Mexican CO2 emissions will 

grow 69% by 2010, although mitigation measures could reduce this rate of growth by nearly half (Pew Center, 2002). 

Generally, energy sector emissions in Mexico vary in proportion to economic growth (e.g., declining somewhat with 

a recession in 2001). However, factors, such as a pressing 

need for additional electricity supplies (calling for more than 

doubling production capacity between 1999 and 2008) could 

increase net emissions, while a national strategy to promote 

greater use of natural gas (along with other policies related 

in part to concerns about emissions associated with urban air 

pollution) could reduce emissions compared with a reference 

case (EIA, 2005).

6.3.3 United States

The Energy Information Administration (EIA, 2006b) projects that emissions from electricity generation in the United 

States between 2004 and 2030 will rise from about 627 Mt 

C (2299 Mt CO2) to more than 900 Mt C (3300 Mt CO2) (an 

increase of about 45%) with three-quarters of the increase 

associated with greater coal use in electric power plants. EIA 

projects that technology advances could lower emissions by 

as much as 9%. Projections of other emissions from energy 

supply systems appear to be unavailable, but emissions could 

be expected to rise at a rate just below the rate of change in 

product consumption in the United States’ economy.

6.4 OPTIONS FOR REDUCING 

EMISSIONS FROM ENERGY

EXTRACTION AND CONVERSION

Few aspects of the carbon cycle have received more attention in the past several decades than emissions from fossil 

It has been estimated that total 

Mexican CO2 emissions will grow 

69% by 2010, although mitigation 

measures could reduce this 

rate of growth by nearly half.

Total carbon emissions from 

energy extraction and conversion in 

North America are currently rising.
69

The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

energy extraction and conversion. As a result, there is a wide 

array of technology and policy options, many of which have 

been examined in considerable detail, although there is not 

a strong consensus on courses of action.

6.4.1 Technology Options

Technology options for reducing energy-supply-related 

emissions (other than reduced requirements due to end-use 

efficiency improvements) consist of:

reducing emissions from fossil energy extraction, production, and movement (e.g., for electricity generation 

by improving the efficiency of existing power plants or 

moving toward the use of lower-emission technologies 

such as coal gasification-combined cycle generation 

facilities) and

shifting from fossil energy sources to other energy 

sources (e.g., energy from the sun [renewable energy] 

or from the atom [nuclear energy]). 

The most comprehensive description of emission-reducing 

and fuel switching technologies and their potentials is the 

U.S. Climate Change Technology Program (CCTP) draft 

Strategic Plan (U.S. Climate Change Technology Program, 

2005), especially Chapters 5 (energy supply) and 6 (capturing and sequestering CO2)—see also National Laboratory 

Directors (1997). The CCTP report focuses on five energy 

supply technology areas: low-emission fossil-based fuels and 

power, hydrogen as an energy carrier, renewable energy and 

fuels, nuclear fission, and fusion energy.

There is a widespread consensus that no one of these options, 

nor one family of options, is a good prospect to stabilize 

greenhouse gas emissions from energy supply systems, nationally or globally, because each faces daunting constraints 

(Hoffert et al., 2002). An example is possible physical 

and/or technological limits to effective global “decarbon-

•

•

ization” (i.e., reducing the use 

of carbon-based energy sources 

as a proportion of total energy 

supplies), including renewable 

or other non-fossil sources of 

energy use at scales that would 

dramatically change the global 

carbon balance between now and 

2050. One conclusion is that “the disparity between what is 

needed and what can be done without great compromise may 

become more acute.”

Instead, progress with technologies likely to be available in 

the coming decades may depend on adding together smaller 

“wedges” of contributions by a variety of resource/technology combinations (Pacala and Socolow, 2004), each of which 

may be feasible if the demands upon it are moderate. If many 

such contributions can be combined, the total effect could 

approach requirements for even relatively ambitious carbon 

stabilization goals, at least in the first half of the century, 

although each contribution would need to be economically 

competitive with current types of fossil energy sources.

A fundamental question is whether prospects for significant 

decarbonization depend on the emergence of new technologies, in many cases requiring advances in science. For 

instance, efforts are being made to develop economically affordable and socially acceptable options for large-scale capture of carbon from fossil-fuel streams—with the remaining 

hydrogen offering a clean energy source—and sequestration 

of the carbon in the ground or the oceans. This approach is 

known to be technologically feasible and is being practiced 

commercially in the North Sea. Recent assessments suggest 

that it may have considerable promise (e.g., IPCC, 2006). If 

so, there is at least some chance that fossil energy sources 

may be used to provide energy services in North America 

and the world in large quantities in the mid to longer terms 

without contributing to a carbon cycle 

imbalance.

What can be expected from technology options over the next quarter to 

half a century is a matter of debate, 

partly because the pace of technology 

development and use depends heavily on policy conditions. Chapter 3 in 

the CCTP draft Strategic Plan (2005) 

shows three advanced technology scenarios drawn from work by the Pacific 

Northwest National Laboratory, varying according to carbon constraints. 

Potential cumulative contributions to 

global emission reduction by energy 

supply technology initiatives between 

If many contributions can 

be combined, the total 

effect could approach 

requirements for even 

relatively ambitious 

carbon stabilization goals.
The U.S. Climate Change Science Program

70 

Chapter 6

2000 and 2100 range from about 25 billion tons of carbon (Gt 

C) equivalent to nearly 350 Gt, which illustrates uncertainties related to both science and policy issues. Carbon capture 

and storage, along with terrestrial sequestration, could add 

reductions between about 100 and 325 Gt C. It has been 

suggested, however, that significantly decarbonizing energy 

systems by 2050 could require massive efforts on a par with 

the Manhattan Project or the Apollo Space Program (Hoffert 

et al., 2002).

Estimated costs of potential technology alternatives for 

reducing greenhouse gas emissions from energy supply 

systems are summarized after the following discussion of 

policy options, because cost estimates are generally based 

on assumptions about policy interventions.

6.4.2 Policy Options

Policy options for carbon emission reduction from energy 

supply systems revolve around either incentives or regulatory 

requirements for such reductions. Generally, interventions 

may be aimed at (a) shaping technology choice and use or 

(b) shaping technology development and supply. Many of the 

policy options are aimed at encouraging end-use efficiency 

improvement as well as supply-side emission reduction.

Options for intervening to change the relative attractiveness 

of available energy supply technology alternatives include 

appealing to voluntary action (e.g., improved consumer 

information, “green power”), a variety of regulatory actions 

(e.g., mandated purchase policies such as energy portfolio 

standards), carbon emission rights trading (where emission 

reduction would have market value), technology/product 

standards, production tax credits for non-fossil energy production, tax credits for alternative energy use, and carbon 

emission taxation or ceilings. Options for changing the 

relative attractiveness of investing in carbon-emission-reducing technology development and dissemination include tax 

credits for certain kinds of energy research and development, 

public-private sector research and devleopment cost sharing, 

and electric utility restructuring. For a more comprehensive 

listing and discussion, see Chapter 6 in IPCC (2001).

In some cases, perceptions that policies and market conditions of the future will be more favorable to emission 

reduction than at present are motivating private industry to 

consider investments in technologies whose market competitiveness would grow in such a future. Examples include 

the CO2 Capture Project and industry-supported projects at 

MIT, Princeton, and Stanford (e.g., see http://www.co2captureproject.org/index.htm).

Most estimates of the impacts of energy policy options on 

greenhouse gas emissions do not differentiate the contributions from energy supply systems from the rest of the energy 

economy (e.g., IWG, 1997; IWG, 2000; IPCC, 2001; National Commission on Energy Policy, 2004; also see OTA, 1991 

and NAS, 1992). For instance the IWG (1997) considered 

effects of $25 and $50 per ton carbon emission permits on 

both energy supply and use, while Interlaboratory Working 

Group (IWG) considered fifty policy/technology options 

(IWG, 2000; also see IPCC, 2001), most of which would 

affect both energy supply and energy use decisions.

6.4.3 Estimated Costs of Implementation

Estimating the costs of emission reduction associated with 

the implementation of various technology and policy options 

for energy supply and conversion systems is complicated by 

several realities. First, many estimates are aggregated for 

the United States or the world as a whole, without separate 

estimates for the energy extraction and conversion sector. 

Second, estimates differ in the scenarios considered, the 

modeling approaches adopted, and the units of measure that 

are used.

More specifically, estimates of costs of emission 

reduction vary widely according to assumptions 

about such issues as how welfare is measured, 

ancillary benefits, and effects in stimulating 

technological innovation; and therefore any particular set of cost estimate includes considerable 

uncertainty. According to IWG (2000), benefits 

of emission reduction would be comparable to 

costs, and the National Commission on Energy 

Policy (2004) estimates that their recommended 

policy initiatives would be, overall, revenueneutral with respect to the federal budget. Other 

participants in energy policymaking, however, 

are convinced that truly significant carbon emission reductions would have substantial economic 

impacts (GAO, 2004).
71

The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

Globally, IPCC (2001) projected that total CO2 emissions 

from energy supply and conversion could be reduced in 

2020 by 350 to 700 Mt C equivalents per year, based on 

options that could be adopted using generally accepted policies, at a positive direct cost of less than U.S. $100 per ton 

of carbon (t C) equivalents. Based on DOE/EIA analyses in 

2000, this study includes estimates of the cost of a range of 

specific emission-reducing technologies for power generation, compared with coal-fired power, although the degree of 

uncertainty is not clear. Within the United States, the report 

estimated that the cost of emission reduction per metric ton of 

carbon emissions reduced would range from -$170 to +$880, 

depending on the technology used. Marginal abatement costs 

for the total United States’ economy (in 1990 U.S. dollars 

per metric ton carbon) were estimated by a variety of models 

compared by the Energy Modeling Forum at $76 to $410 

with no emission trading, $14 to $224 with Annex I trading, 

and $5 to $123 with global trading.

Similarly, the National Commission on Energy Policy (2004) 

considered costs associated with a tradable emission permit 

system that would reduce United States’ national greenhouse 

gas emission growth from 44% to 33% from 2002 to 2025, a 

reduction of 207 Mt C (760 Mt CO2) in 2025 compared with 

a reference case. The cost would be a roughly 5% increase in 

total end-use expenditures compared with the reference case. 

Electricity prices would rise by 5.4% for residential users, 

6.2% for commercial users, and 7.6% for industrial users.

The IWG (2000) estimated that a domestic carbon trading 

system with a $25/t C permit price would reduce emissions 

by 13%, or 63 Mt C (230 Mt CO2), compared with a reference case, while a $50 price would reduce emissions by 

17 to 19%, or 83 to 91 Mt C (306 to 332 Mt CO2). Both 

cases assume a doubling of United States’ government appropriations for cost-shared clean energy research, design, 

and development.

For carbon capture and sequestration, IPCC (2006) concluded 

that this option could contribute 15 to 55% to global mitigation between now and 2100 if technologies develop as projected in relatively optimistic scenarios and very large-scale 

geological carbon sequestration is publicly acceptable. Under 

these assumptions, the cost is projected to be $110 to $260/t 

C ($30 to $70/t CO2). With less optimistic assumptions, the 

cost could rise above $730/t C ($200/t CO2).

Net costs to the consumer, however, are balanced in some 

analyses by benefits from advanced technologies, which are 

developed and deployed on an accelerated schedule due to 

policy interventions and changing public preferences. The 

U.S. Climate Change Technology Program (2005: pp. 3-

19) illustrates how costs of achieving different stabilization 

levels can conceivably be reduced substantially by the use 

of advanced technologies, and IWG (2000) 

estimates that net enduser costs of energy 

can actually be reduced 

by a domestic carbon 

trading system if it accelerates the market penetration of 

more energy-efficient technologies.

In many cases, however, discussions of the promise of technology options are not associated with cost estimates. Economic costs of energy are not one of the drivers of the IPCC 

Special Report on Emissions Scenarios (SRES) scenarios, 

and such references as Hoffert et al. (2002) and Pacala and 

Socolow (2004) are concerned with technological potentials 

and constraints as a limiting condition on market behavior 

rather than with comparative costs and benefits of particular 

technology options at the margin.

6.4.4 Summary

In terms of prospects for major emission reductions from 

energy extraction and conversion in North America, the key 

issues appear to be the extent, direction, and pace of technological innovation and the likelihood that policy conditions 

favoring carbon emissions reduction that do not now exist 

will emerge if concerns about carbon cycle imbalances grow. 

In these regards, the prospects are brighter in the long term 

(e.g., more than several decades in the future) than in the near 

term. History suggests that technology solutions are usually 

easier to implement than policy solutions, but observed impacts of carbon cycle imbalances might change the political 

calculus for policy interventions in the future.

6.5 RESEARCH AND 

DEVELOPMENT NEEDS

If it is possible that truly effective management of carbon 

emissions from energy supply and conversion systems 

cannot be realized with the current portfolio of technology 

alternatives under current policy conditions, then research 

and development needs and opportunities deserve expanded 

attention and support (e.g., National Commission on Energy 

Policy, 2004). If so, the priorities include the following:

Technology. Several objectives seem to be especially relevant to carbon management potentials:

clarifying and realizing potentials for carbon capture 

and sequestration;

clarifying and realizing potentials of affordable renewable energy systems at a relatively large scale;

addressing social concerns about the nuclear energy fuel 

cycle, especially in an era of concern about terrorism;

improving estimates of economic costs and emission 

reduction benefits of a range of energy technologies 

•

•

•

•

Costs of achieving different 

stabilization levels can conceivably 

be reduced substantially by the 

use of advanced technologies.
The U.S. Climate Change Science Program

72 

Chapter 6

across a range of economic, technological, and policy 

scenarios; and

“Blue Sky” research to develop new technology options 

and families, such as innovative approaches for energy 

from the sun and from biomass, including possible applications of nanoscience (Caldeira et al., 2005; Lewis, 

2005).

Policy. Research and development could also be applied to 

policy options in order to enlarge their knowledge bases and 

explore their implications. For instance, research priorities 

might include learning more about:

public acceptability of policy incentives for reducing 

dependence on energy sources associated with carbon 

emissions;

possible effects of incentives for the energy industry to 

increase its support for pathways not limited to fossil 

fuels;

approaches toward a more distributed electric power 

supply enterprise in which certain renewable (and hydrogen) energy options might be more attractive;

transitions from one energy system/infrastructure to 

another; and

interactions and linkage effects among driving forces 

and responses, along with possible effects of exogenous 

processes and policy interventions.

In these ways, technology and policy advances might be 

combined with multiple technologies to transform the capacity to manage carbon emissions from energy supply systems, 

if that is a high priority for North America.

•

•

•

•

•

•
The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

Transportation

CHAPTER

7

73

Lead Author: David L. Greene, ORNL

KEY FINDINGS

The transportation sector of North America released 587 million tons of carbon into the atmosphere in 2003, nearly 

all in the form of carbon dioxide from combustion of fossil fuels. This comprises 37% of the total carbon dioxide emissions from worldwide transportation activity, which in turn, accounts for about 22% of total global carbon dioxide 

emissions.

Transportation energy use in North America and the associated carbon emissions have grown substantially and 

relatively steadily over the past 40 years. Growth has been most rapid in Mexico, the country most dependent upon 

road transport.

Carbon emissions by transport are determined by the levels of passenger and freight activity, the shares of transport 

modes, the energy intensity of passenger and freight movements, and the carbon intensity of transportation fuels. 

The growth of passenger and freight activity is driven by population, per capita income, and economic output.

Chiefly as a result of economic growth, energy use by North American transportation is expected to increase by 46% 

from 2003 to 2025. If the mix of fuels were assumed to remain the same, carbon dioxide emissions would increase 

from 587 million tons of carbon in 2003 to 859 million tons of carbon in 2025. Canada, the only one of the three 

countries in North America to have committed to specific greenhouse gas reduction goals, is expected to show the 

lowest rate of growth in carbon emissions.

The most widely proposed options for reducing the carbon emissions of the North American transportation sector are increased vehicle fuel economy, increased prices for carbon-based fuels, liquid fuels derived from vegetation 

(biomass), and in the longer term, hydrogen 

produced from renewable energy sources 

(such as hydropower), nuclear energy, 

or from fossil fuels with carbon capture 

and storage. Biomass fuels appear to be a 

promising near- and long-term option, while 

hydrogen could become an important energy 

carrier after 2025.

After the development of advanced energy 

efficient vehicle technologies and low-carbon 

fuels, the most pressing research need in the 

transportation sector is for comprehensive, 

consistent, and rigorous assessments of 

carbon emissions mitigation potentials and 

costs for North America.

•

•

•

•

•

•
The U.S. Climate Change Science Program Chapter 7

74 

7.1 BACKGROUND

Transportation is the largest source of carbon emissions 

among North American energy end uses (electricity 

generation is considered energy conversion rather than end 

use). This fact reflects the vast scale of passenger and freight 

movements in a region that 

comprises one-fourth of 

the global economy, as 

well as the dominance of 

relatively energy-intensive 

road transport and the near 

total dependence of North 

American transportation 

systems on petroleum as a 

source of energy. If present 

trends continue, carbon 

emissions from North American transportation are expected 

to increase by more than one-half by 2050. Options for 

mitigating carbon emissions from the transportation sector, 

like increased vehicle fuel economy and biofuels, could offset 

the expected growth in transportation activity. However, at 

present only Canada has committed to achieving a specific 

reduction in future greenhouse gas (GHG) emissions: 6% 

below 1990 levels by 2012 (Environment Canada, 2005b).

7.2 INVENTORY OF CARBON EMISSIONS

Worldwide, transportation produced about 22% (1.5 billion 

tons of carbon [Gt C]) of total global carbon dioxide (CO2) 

emissions from the combustion of fossil fuels (6.6 Gt C) in 

2000 (page 3-1 in U.S. EPA, 2005; 

Marland, Boden, and Andres, 

2005). Home to 6.7% of the world’s 

6.45 billion people and source of 

24.8% of the world’s $55.5 trillion 

gross world product (CIA, 2005), 

North America produces 37% of 

the total carbon emissions from 

worldwide transportation activity 

(Fulton and Eads, 2004).

Transportation activity is driven 

chiefly by population, economic 

wealth, and geography. Of the 

approximately 435 million residents of North America, 68.0% 

reside in the United States, 24.5% 

in Mexico, and 7.5% in Canada 

(CIA, 2005) (these population 

estimates are judged by the author 

to have 95% certainty that the 

actual value is within 10% of the 

estimate reported, and the gross 

domestic product (GDP) estimates are judged to have 95% 

certainty that the actual value is within 25% of the estimate 

reported, chiefly because they are not based on triple bottom 

line accounting). The differences in the sizes of the three 

countries’ economies are far greater. The United States is the 

world’s largest economy, with an estimated GDP of $11.75 

trillion in 2004. 

 Although Mexico has approximately three times the population of Canada, its GDP is roughly the same, $1.006 trillion 

compared to $1.023 trillion (measured in 2004 purchasing 

power parity dollars). With the largest population and largest 

economy, the United States has by far the largest transportation system. The United States accounted for 87% of the 

energy used for transportation in North America in 2003, 

Canada for 8%, and Mexico 5% (Figure 7.1) (see Table 4.1 in 

Figure 7.1 Transportation energy use in North America, 1990-

2003. Sources: NATS (2005), Table 4-1; U.S. DOE/EIA (2005a), 

Table 2.1e.

North American Carbon Emissions by Country and Mode, 2003/2001

(Mt C)

United 

States

2003

Canada

2003

Mexico

2001

North 

America

2003/2001

Road 399.4 36.7 26.0 462.0

Domestic Air 46.7 1.9 1.8 50.4

Rail 11.7 1.4 0.4 13.5

Domestic Water 15.7 1.6 0.9 18.1

Pipeline 9.5 2.4 11.9

International Bunker 23.0 3.0 0.5 26.4

Off-Road 4.6 4.6

Total 505.9 51.7 29.4 587.0

Table 7.1 Carbon emissions from transportation in North America in 2003.

Sources: U.S. EPA (2005); Environment Canada (2005a); INE (2003)

Note: Data for Mexico is 2001, United States and Canada are 2003.

Carbon dioxide emissions estimates are considered by the Canadian and Mexican sources to have 

95% certainty that the actual value is within 10% of the estimate reported. The United States did 

not provide quantitative uncertainty estimates for 2003, but these estimates are considered to be 

equally accurate by the author.

Transportation is the 

largest source of carbon 

emissions among North 

American energy end uses 

(electricity generation is 

considered energy conversion 

rather than end use).
75

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

NATS, 2005). These differences in energy use are directly 

reflected in carbon emissions from the three countries’ 

transportation sectors (Table 7.1)1.

Transportation is defined as private and public vehicles that 

move people and commodities (U.S. EPA, 2005, p. 296). This 

includes automobiles, trucks, buses, motorcycles, railroads 

and railways (including streetcars and subways), aircraft, 

ships, barges, and natural gas pipelines. This definition 

excludes petroleum, coal slurry, and water pipelines, as well 

as the transmission of electricity, although many countries 

consider all pipelines part of the transport sector. It also 

generally excludes mobile sources not engaged in transporting people or goods, such as construction equipment 

and on-farm agricultural equipment. In addition, carbon 

emissions from international bunker fuel-use in aviation and 

waterborne transport, though considered part of transport 

emissions, are generally accounted for separately from a 

nation’s domestic GHG inventory. In this chapter, however, 

they are included, as are carbon emissions from military 

transport operations, because they are real inputs to the carbon cycle. Upstream, or well-to-tank, carbon emissions are 

not included with transportation end-use, nor are end-of-life 

emissions produced in the disposal or recycling of materials 

used in transportation vehicles or infrastructure because 

these carbon flows are in the domain of other chapters. These 

two categories of emissions typically comprise 20-30% of 

total life cycle emissions for transport vehicles (see Table 5.4 

in Weiss et al., 2000). In the future, it is likely that upstream 

carbon emissions will be of greater importance in determining the total emissions due to transportation activities.

In addition to CO2, the combustion of fossil fuels by transportation produces other GHGs including methane (CH4), 

nitrous oxide (N2O), carbon monoxide (CO), nitrogen oxides 

(NOx), and non-CH4 volatile organic compounds (VOCs). 

Those containing carbon are generally oxidized in the atmosphere to ultimately produce CO2. However, the quantities 

of non-CO2 gases produced by transportation vehicles are 

very minor sources of carbon in comparison to the volume 

of CO2 emissions. For example, North American emissions 

of CH4 by transportation accounted for only 0.03% of total 

transportation carbon emissions in 2003. This chapter will 

therefore address primarily the CO2 emissions from transportation activities (CH4 emissions are included in the totals 

presented in Table 7.1, but they are not included in any other 

estimates presented in this chapter). Estimates of non-CO2

emissions are also subject to much greater uncertainty. 

INE (2003) generally put the accuracy of the Mexican 2001 

non-CO2 GHG emissions at 95% certainty that the actual 

value is within 50% of the estimate reported. However, Environment Canada’s 2003 inventory (Environment Canada, 

1

 Uncertainties in these estimates are discussed later in this chapter 

(see Section 7.5). 

2005a) rates the uncertainty of CH4 emissions from mobile 

sources as 95% certain that the actual value is within 10% 

of the estimate reported. 

Four main sources of information on carbon emissions are 

used in this chapter. The estimates shown in Table 7.1 were 

obtained from the GHG inventory reports of the three countries, estimated by environmental agencies in accordance 

with Intergovernmental Panel on Climate Change (IPCC) 

guidelines. As Annex 1 countries, Canada and the United 

States are obliged to compile annual inventories under IPCC 

guidelines. As a non-Annex 1 country, Mexico is not. These 

inventories are the most authoritative sources for estimates 

of carbon emissions. The inventory reports, however, do 

not generally provide estimates of associated energy use 

and the most recent inventory data available for Mexico 

are for 2001. Estimates of energy use and carbon emissions 

produced by the countries’ energy agencies are also used 

in this chapter to illustrate the relationship between energy 

use and carbon emissions and its historical trends. There 

are some minor differences between the carbon emissions 

estimates from the two sources. Finally, future projections 

of carbon emissions for North America to 2025 were taken 

from the U.S. Energy Information’s Annual Energy Outlook 

2005, and projections to 2050 were taken from the World 

Business Council on Sustainable Development’s Sustainable 

Mobility Project (WBCSD, 2004).

7.2.1 Fuels Used in Transportation

Virtually all of the energy used by the transport sector in 

North America is derived from petroleum, and most of the 

remainder comes from natural gas (Table 7.2). In the United 

States, 96.3% of total transportation energy is obtained by 

combustion of petroleum fuels (U.S. DOE/EIA, 2005a). Most 

of the non-petroleum energy is natural gas used to power 

natural gas pipelines (2.5%, 744 

petajoules). During 

the past two decades, ethanol use 

(as a blending component for gasoline) 

has increased from a 

negligible amount to 

1.1% of transportation energy use (312 petajoules). Electricity, mostly for passenger rail transport, comprises only 0.1% 

of United States transport energy use. This pattern of energy 

use has persisted for more than half a century.

The pattern of energy sources is only a little different in 

Mexico where 96.2% of transportation energy use is gasoline, diesel, or jet fuel, 3.4% is liquefied petroleum gas, and 

less than 0.2% is electricity (Rodríguez, 2005). In Canada, 

natural gas use for natural gas pipelines accounts for 7.5% 

Virtually all of the energy used 

by the transport sector in North 

America is derived from petroleum, 

and most of the remainder 

comes from natural gas.
The U.S. Climate Change Science Program Chapter 7

76 

of transport energy use, 91.8% 

is petroleum, 0.5% is propane, 

and only 0.1% is electricity (see 

Table 1 in NRCan, 2006).

7.2.2 Mode of Transportation

Mode of transportation refers to how people and freight 

are moved about, whether by 

road, rail, or air, or in light or 

heavy vehicles. Carbon dioxide emissions from the North 

American transportation sector 

are summarized by mode in 

Table 7.3, and the distribution 

of emissions by mode for North 

America in 2003 is illustrated in 

Figure 7.2.

 7.2.2.1 Freight Transport

Movement of freight is a major 

component of the transportation 

sector in North America. Total 

freight activity in the United 

States, measured in metric tonkm, is 20 times that in Mexico 

and more than 10 times the levels observed in Canada (Figures 

7.3A, 7.3B, and 7.3C).

In Mexico, trucking is the mode 

of choice for freight movements. Four-fifths of Mexican 

metric ton-km is produced by 

trucks. Moreover, trucking’s 

modal share has been increasing over time.

In Canada, rail transport accounts for the majority of 

freight movement (65%). Rail 

transport is well suited to the 

approximately linear distribution of Canada’s population in 

close proximity to the United 

States border, the long-distances from east to west, and 

the large volumes of raw material flows typical of Canadian 

freight traffic (see Table 5.2 in 

NATS, 2005).

North America energy source Energy 

input (Petajoules)

Carbon input 

(Mt C)

Gasoline 20,923 358.3

Diesel/distillate 7,344 129.5

Jet fuel/kerosene 2,298 68.5

Residual 681 14.5

Other fuels 124 1.3

Natural gas 926 9.7

Electricity 36 0.0

Unallocated/error 466 -

Total 32,798 581.8

United States

Gasoline 18,520 312.5

Diesel/distillate 6,193 107.1

Jet fuel/kerosene 1,986 62.3

Residual 612 13.1

Other fuels 50 0.2

Natural gas 748 9.7

Electricity 20 0.0

Unallocated/error 466.2 -

Total 28,595.2 504.9

Sources: U.S. EPA (2005), Tables 3-7 and 2-17; Davis and Diegel (2004), Tables 2.6 and 2.7.

Canada

Gasoline 1,355 26.2

Diesel/distillate 698 13.9

Jet fuel/kerosene 223 4.3

Residual 67 1.3

Other fuels 17 0.2

Natural gas 2 0.0

Electricity 3 0.0

Unallocated/error 0

Total 2,363 45.9

NRCan (2006), Tables 1 and 8.

Mexico

Gasoline 1,066 19.5

Diesel/distillate 447 8.5

Jet fuel/kerosene 106 1.9

Residual 4 0.1

Other fuels 57 0.9

Natural gas 1 0.0

Electricity 4 0.0

Unallocated/error

Total 1,685 31.0

Sources: Transportation energy use by fuel and mode from Rodríguez (2005).

Table 7.2 Summary of North American transport energy use and CO2 emissions 

in 2003 by energy source or fuel type.

The accuracy of the data in the above table is judged by the author to be 95% certain that the 

actual value is within 10% of the estimate reported. 

Data sources differ somewhat by country with respect to modal, fuel, and greenhouse gas 

definitions so that the numbers are not precisely comparable. Canadian carbon emissions data 

include all GHGs produced by transportation in CO2 equivalents, while the United States’ data are 

CO2 emissions only. Carbon dioxide emissions for Mexico were estimated by applying U.S. EPA 

emissions factors to the Mexican energy use data. For Mexico, it is asumed that no transportation 

carbon emissions result from electricity use.
77

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

In the United States, road freight plays a greater role than 

in Canada, and rail is less dominant, although rail still carries the largest share of metric ton-km (40%). In none of the 

countries does air freight account for a significant share of 

metric ton-km.

7.2.2.2 Passenger Transport

In all three countries, passenger transport is predominantly 

by road, followed in distant second by air travel. The rate of 

growth in air travel in North America is more than double 

that of road transport, so air transport’s share of carbon 

emissions will increase in the future. Nearly complete data 

are available for passenger-kilometers-traveled (pkt) by 

mode in the United States and Canada in 2001. Of the more 

than 8 trillion pkt accounted for 

by the United States, 86% was by 

light-duty personal vehicles, most 

by passenger car but a growing 

share by light trucks (Figure 7.4A) 

(motorcycle pkt, about 0.2% of the 

total, is included with passenger 

car). Air travel claims 10%; other 

modes are minor.

Canadian passenger travel exhibits a very similar modal 

structure, but with a smaller role played by light trucks and 

air and a larger share for buses (Figure 7.4B) (transit numbers for Canada were not available at the time these figures 

were compiled).

7.3 TRENDS AND DRIVERS

Driven by economic and population growth, transportation 

energy use has increased substantially in all three countries 

since 1990. Figures 7.5A and 7.5B illustrate the evolution 

of transport energy use by mode for Mexico and the United 

Figure 7.2 North American carbon emissions from transportation by mode; United States and Canada 2003, Mexico 2001. 

Sources: U.S. EPA (2005); Environment Canada (2005a); INE 

(2003).

North America 

transport mode

Energy use 

(Petajoules)

Carbon 

emissions 

(Mt C)

Road 25,830 463.5

Air 2,667 53.0

Rail 751 13.7

Waterborne 1,386 18.4

Pipeline 990 12.3

Internatl./Bunker 0 23.0

Total 31,624 583.9

United States

Road

Light vehicles 17,083 303.8

Heavy vehicles 5,505 95.5

Air 2,335 46.7

Rail 655 11.7

Waterborne 1,250 15.7

Pipeline/other 986 9.5

Internatl./Bunker 23.0

Total 27,814 505.8

Source: U.S. EPA (2005), Tables 3-7 and 2-17; Davis and 

Diegel (2004), Tables 2-6 and 2-7.

Canada

Road

Light vehicles 1,233 23.8

Heavy vehicles 491 12.4

Air 226 4.3

Rail 74 1.6

Waterborne 103 2.1

Pipeline/other 1.8

Total 2,126 46.1

Source: NRCan (2006); Tables 1 and 8.

Mexico

Road 1,518 27.9

Light vehicles

Heavy vehicles

Air 107 2.0

Rail 22 0.5

Waterborne 33 0.6

Electric 4 -

Total 1,684 32.0

Source: Rodríguez (2005).

Table 7.3 Summary of North American transport energy use and carbon dioxide emissions in 2003 by mode 

of transportation.

The accuracy of the data in the above table is judged by the 

author to be 95% certain that the actual value is within 10% of the 

estimate reported for the larger modes of transportation, and 

95% certain that the value is within 25% for the smaller modes.

Data sources differ somewhat by country with respect to 

modal, fuel, and GHG defintions so that the numbers are not 

precisely comparable. Canadian carbon emissions data include 

all GHGs produced by transportation in CO2 equivalents, while 

United States data are CO2 emissions only. Carbon dioxide 

emissions for Mexico were estimated by applying U.S. EPA 

emissions factors to the Mexican energy use data. Electricity is 

assumed to produce no carbon emssions in end use.

In all three countries, 

passenger transport is 

predominantly by road, 

followed in distant 

second by air travel.
The U.S. Climate Change Science Program Chapter 7

78 

States. Energy use has grown most rapidly in Mexico, the 

country most dependent on road transport. In the United 

States, the steady growth of transportation oil use was 

interrupted by oil price shocks in 1973-74, 1979-80, and to 

a much lesser degree in 1991. The impact of the attack on 

the World Trade Center in 2001 and subsequent changes in 

air travel procedures had a visible effect on energy use for 

air travel.

The evolution of transport carbon emissions has closely followed the evolution of energy use. Carbon dioxide emissions 

by mode are shown for the United States and Canada for the 

period 1990-2003 in Figures 7.6A and 7.6B. The Canadian 

data include light-duty commercial vehicles in road freight 

transport, while all light trucks are included in the light-duty 

vehicle category in the United States data. These data illustrate the relatively faster growth of freight-transport energy 

use. Fuel economy standards in both countries restrained the 

growth of passenger car and light-truck energy use (NAS, 

2002). From 1990 to 2003 passenger kilometers traveled 

by road in Canada increased by 23%, while energy use 

increased by only 15%. In 2003, freight activity accounted 

for more than 40% of Canada’s transport energy use. In 

addition, while passenger transport energy use increased 

by 15% from 1990 to 2003, freight energy use increased by 

40%. The Canadian transport energy statistics do not include 

natural gas pipelines as a transport mode.

Carbon emissions by transport are determined by the levels 

of passenger and freight activity, the shares of transport 

modes, the energy intensity of passenger and freight movements, and the carbon intensity of transportation fuels. In 

North America, petroleum fuels supply over 95% of transportation’s energy requirements and account for 98% of the 

sector’s GHG emissions. Among modes, road vehicles are 

predominant, producing almost 80% of sectoral GHG emissions. Consequently, the driving forces for transportation 

GHG emissions have been changes in activity and energy 

intensity. The principal driving forces of the growth of passenger transportation are population and per capita income 

(WBCSD, 2004). Increased vehicle ownership follows rising 

per capita income, as do vehicle use, fuel consumption, and 

emissions. In general, energy forecasters expect the greatest 

growth in vehicle ownership and fossil-fuel use in transporFigure 7.3A Freight activity by mode in Canada.

Figure 7.3B Freight activity by mode in Mexico. 

Figure 7.3C Freight activity by mode in the United States.

Figure 7.4A Distribution of passenger travel in the United 

States by mode.

Figure 7.4B Distribution of passenger travel by mode in 

Canada.
79

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

tation over the next 25-50 years to occur in the developing 

economies (U.S. DOE/EIA, 2005b; IEA, 2004; WBCSD, 

2004; Nakićenović, Grűbler, and McDonald, 1998). The 

chief driving forces for freight activity are economic 

growth and the integration of economic activities at both 

regional and global scales (WBCSD, 2004).

Projections of North American transportation energy use 

and carbon emissions to 2030 have been published by the 

U.S. Energy Information Administration (U.S. DOE/EIA, 

2005b) and the International Energy Agency (IEA, 2005a). 

Historical population growth rates are similar in the three 

countries, 0.92% per year in the United States, 1.17% per 

year in Mexico, and 0.90% per year in Canada. Recent 

annual GDP growth rates are 4.4% for the United States, 

4.1% for Mexico, and 2.4% for Canada (CIA, 2005). The 

U.S. Energy Information Administration’s Reference Case 

projection assumes annual GDP growth rates of 3.1% for 

the United States, 2.4% for Canada, and 3.9% for Mexico 

(see Table A3 in U.S. DOE/EIA, 2005b). Assumed population growth rates are United States: 0.9%; Canada: 0.6%; 

Mexico: 1.0% (see Table A14 in U.S. DOE/EIA, 2005b). 

Chiefly because of economic growth, energy use by North 

American transportation is expected to increase by 46% 

from 2003 to 2025 (U.S. DOE/EIA, 2005b). If the mix of 

fuels is assumed to remain the same, as it nearly does in 

the IEO 2005 Reference Case projection, CO2 emissions 

would increase from 587 million metric tons of carbon (Mt 

C) in 2003 to 859 Mt C in 2025 (Figure 7.7). Canada, the 

only one of the three countries to have committed to specific 

GHG reduction goals, is expected to show the lowest rate of 

growth in CO2 emissions.

The World Business Council for Sustainable Development 

(WBCSD), in collaboration with the International Energy 

Agency developed a model for projecting world transport 

energy use and GHG emissions to 2050 (Table 7.4). The 

WBCSD’s reference case projection foresees the most rapid 

growth in carbon emissions from transportation occurring 

in Asia and Latin America (Figure 7.8). Still, in 2050, North 

America accounts for 26.4% of global CO2 emissions from 

transport vehicles (down from a 37.2% share in 2000). 

Figure 7.5A Evolution of transport energy use in Mexico.

Figure 7.5B Evolution of transport energy use in the United 

States.

Figure 7.6A Evolution of transport energy use in Mexico. 

Source: SENER (2005).

Figure 7.6B Transport CO2 emissions in the United States.
The U.S. Climate Change Science Program Chapter 7

80 

7.4 OPTIONS FOR MANAGEMENT

Dozens of policies and measures for reducing petroleum 

consumption and mitigating carbon emissions from 

transportation in North America have been identified and 

assessed (e.g., U.S. DOT, 1998; IEA, 2001; Greene and Schafer, 2003; Greene et al., 2005; CBO, 2003; Harrington and 

McConnell, 2003; NRTEE, 2005). However, there is no consensus about how much transportation GHG emissions can 

be reduced and at what cost. In general, top-down models 

estimating the mitigation impacts of economy-wide carbon 

taxes or cap-and-trade systems find the cost of mitigation 

high and the potential modest. On the other hand, bottomup studies evaluating a wide array of policy options tend 

to reach the opposite conclusion. Part of the explanation of 

this paradox may lie in the predominant roles that governments play in constructing, maintaining, and operating the 

majority of transportation infrastructure and in the strong 

interrelationship between land-use planning and transportation demand. In addition, top down models typically assume 

that all markets are efficient, whereas there is evidence of 

real-world transportation energy market failures, especially 

with respect to the determination of light-duty vehicle fuel 

economy (e.g., Turrentine and Kurani, 2004; Chapter 5 in 

NAS, 2002). Estimates of the costs and benefits of mitigation 

policies also vary widely and depend critically on premises 

concerning (1) the efficiency of transportation energy markets, (2) the values consumers attach to vehicle attributes 

such as acceleration performance and vehicle weight, and (3) 

the current and future status of carbon-related technology.

A U.S. Energy Information Administration evaluation of 

a GHG cap and trade system, expected to result in carbon 

permit prices of $79/t C in 2010 and $221/t C in 2025, was 

estimated to reduce 2025 transportation energy use by 4.3 

Petajoules (PJ) and to cut transportation’s carbon emissions by 10% from 225 Mt C in the reference case to 203 

Mt C under this policy (U.S. DOE/EIA, 2003). The average 

fuel economy of new light-duty vehicles was estimated to 

increase from 26.4 miles 

per gallon (mpg, or 8.9 L 

per 100 km) to 29.0 mpg 

(8.1 L per 100 km) in the 

policy case, an improvement of only 10%. A 

2002 study by the U.S. 

National Academy of 

Sciences (NAS, 2002) 

estimated that “cost-efficient” fuel economy 

improvements for United 

States’ light-duty vehicles using proven technologies ranged from 

12% for subcompact cars 

to 27% for large cars, 

and from 25% for small 

2000 2010 2020 2030 2040 2050

OECD North America 544 623 708 768 824 882

OECD Europe 313 359 392 412 420 428

OECD Pacific 133 142 153 161 169 179

FSU 48 64 88 109 132 153

Eastern Europe 23 28 36 42 52 66

China 69 108 163 225 308 417

Other Asia 98 131 174 220 283 368

India 38 54 80 108 146 203

Middle East 59 71 88 106 122 138

Latin America 95 127 172 216 275 352

Africa 43 58 80 103 127 158

TOTAL - All Regions 1463 1766 2134 2470 2858 3343

Table 7.4 Global carbon emissions from transportation vehicles to 2050 by regions, 

WBCSD reference case projection (Mt C).

Source: Fulton and Eads (2004).

Figure 7.8 World Business Council for Sustainable Development 

(WBCSD) projections of world transportation vehicle CO2 emissions to 2050. Source: U.S. EPA (2005), Table 2-17.

Figure 7.7 Projected CO2 emissions from the North American 

transport sector in 2025, based on EIA IEO (2005) reference 

case. Source: NRCan (2006).
81

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

sport utility vehicles (SUVs) to 42% for large SUVs. The 

NAS study did not include the potential impacts of diesel or 

hybrid vehicle technologies and assumed that vehicle size 

and horsepower would remain constant. 

The U.S. Congressional Budget Office (CBO, 2003) estimated that achieving a 10% reduction in United States gasoline use would create total economic costs of approximately 

$3.6 billion per year if accomplished by means of Corporate 

Average Fuel Economy (CAFE) standards, $3.0 billion if 

the same standards allowed trading of fuel economy credits 

among manufacturers, and $2.9 billion if accomplished via 

a tax on gasoline. This partial equilibrium analysis assumed 

that it would take about 14 years for the policies to have their 

full impact. If one assumes that the United States would 

consume 22,600 PJ of gasoline in 2017, resulting in 387 Mt 

of CO2 emissions, then a 10% reduction amounts to 39 Mt 

C. At a total cost of $3 billion per year, and attributing the 

full cost to carbon reduction (vs. other objectives such as 

reducing petroleum dependence), produces an upper-bound 

mitigation cost estimate of $77/t C.

The bipartisan National Commission on Energy Policy 

(NCEP, 2004) surveyed recent assessments of the potential 

to increase light-duty vehicle fuel economy in the United 

States. Taking into consideration uncertainties about the 

costs and technical potential of fuel economy technologies, 

as well as the future price of fuel, the Commission concluded 

that future increases in fuel economy of from 40% to 80% 

could be achieved at a cost that would be fully offset by the 

value of fuel saved over the life of a vehicle. They estimated 

that the essentially costless carbon emissions reductions 

would amount to between 250 and 400 million metric tons 

per year by 2030.

Systems of progressive vehicle taxes on purchases of less 

efficient new vehicles and subsidies for more efficient new 

vehicles (“feebates”) are yet another alternative for increasing vehicle fuel economy. A study of the United States 

market (Greene et al., 2005) examined a variety of feebate 

structures under two alternative assumptions: (1) consumers consider only the first three years of fuel savings when 

making new vehicle purchase decisions, and (2) consumers 

consider the full discounted present value of lifetime fuel 

savings. The study found that if consumers consider only 

the first three years of fuel savings, then a feebate of $1000 

per 0.01 gal/mile (3.5 L per 100 km), designed to produce no 

net revenue to the government, would produce net benefits 

to society in terms of fuel savings and would reduce carbon 

emissions by 139 Mt C in 2030. If consumers fully valued 

lifetime fuel savings, the same feebate system would cause 

a $3 billion loss in consumers’ surplus (a technical measure 

of the change in economic well-being closely approximating 

income loss) and reduce carbon emissions by only 67 Mt C, 

or an implied cost of $44/Mt CO2.

The most widely proposed options for reducing the carbon 

content of transportation fuels are liquid fuels derived from 

biomass and hydrogen produced from renewables, nuclear 

energy, or from fossil fuels with carbon sequestration. Biomass fuels, such as ethanol from cellulosic feedstocks or 

liquid hydrocarbon fuels produced via biomass gasification 

and synthesis, appear to be a promising mid- to long-term 

option, while hydrogen could become an important energy 

carrier, but not before 2025 (WBCSD, 2004). The carbon 

emission reduction potential of biomass fuels for transportation is strongly dependent on the feedstock and conversion 

processes. Advanced methods of producing ethanol from 

grain, the predominant feedstock in the United States can 

reduce carbon emissions by 10% to 30% (Wang, 2005; p. 

16 in IEA, 2004). Production of ethanol from sugar cane, 

as is the current practice 

in Brazil, or by not-yetcommercialized methods 

of cellulosic conversion 

can achieve up to a 90% 

net reduction over the 

fuel cycle. Conversion of 

biomass to liquid hydrocarbon fuels via gasification and synthesis may 

have a similar potential 

(Williams, 2005). The technical potential for liquid fuels 

production from biomass is very large and very uncertain; 

recent estimates of the global potential range from 10 to 400 

exajoules per year (see Table 6.8 in IEA, 2004). The U.S. 

Departments of Energy and Agriculture have estimated 

that 30% of United States’ petroleum use could be replaced 

by biofuels by 2030 (Perlack et al., 2005). The economic 

potential will depend on competition for land with other 

uses, the development of a global market for biofuels, and 

advances in conversion technologies.

Hydrogen must be considered a long-term option because 

of the present high cost of fuel cells, technical challenges 

in hydrogen storage, and the need to construct a new infrastructure for hydrogen production and distribution (NAS, 

2004; U.S. DOE, 2005; IEA, 2005b). Hydrogen’s potential to 

mitigate carbon emissions from transport will depend most 

strongly on how hydrogen is produced. If produced from 

coal gasification without sequestration of CO2 emissions 

in production, it is conceivable that carbon emissions could 

increase. If produced from fossil fuels with sequestration, 

or from renewable or nuclear energy, carbon emissions from 

road and rail vehicles could be virtually eliminated (General 

Motors et al., 2001).

The most widely proposed 

options for reducing the carbon 

content of transportation 

fuels are liquid fuels derived 

from biomass and hydrogen 

produced from renewables, 

nuclear energy, or from fossil 

fuels with carbon sequestration. 
The U.S. Climate Change Science Program Chapter 7

82 

In a comprehensive assessment of opportunities to reduce 

GHG emissions from the United States transportation sector, a study published by the Pew Center on Global Climate 

Change (Greene and Schafer, 2003) estimated that sectorwide reductions in the vicinity of 20% could be achieved 

by 2015 and 50% by 2030 (Table 7.5). The study’s premises 

assumed no change in the year 2000 distribution of energy 

use by mode. A wide range of strategies was considered, 

including research and development, efficiency standards, 

use of biofuels and hydrogen, pricing policies to encourage 

efficiency and reduce travel demand, land-use transportation 

planning options, and public education (Table 7.5). Other 

key premises of the analysis were that (1) for efficiency 

improvements the value of fuel saved to the consumer must 

be greater than or equal to the cost of the improvement, (2) 

there is no change in vehicle size or performance, (3) pricing 

Reduction potential 

per mode/fuel (%)

Transportation sector 

reduction potential (%)

Management option Carbon emission 

(Mt C) 2000 2015 2030 2015 2030

Research, development, and demonstration

Light-duty vehicles (LDVs) 289 11b 38b 7b 23b

Heavy trucks 80 11b 24b 2b 4b

Commercial aircraft 53 11b 27b 1b 3b

Efficiency standards

Light-duty vehicles 289 9 31 6 18

Heavy trucks 80 9 20 2 3

Commercial aircraft 53 9 22 1 2

Replacement and alternative fuels

Low-carbon replacement fuels

(~10% of LDV fuel) 27 30 100 2 7

Hydrogen fuel (All LDV fuel) 289 1 6 1 4

Pricing policies

Low-carbon replacement fuels

(~10% of LDV fuel) 27 30 100 2 6

Carbon pricing

(All transportation fuel) 489 3 6 3 6

Variabilization

(All highway vehicle fuel) 370 8 12 6 9

Behavioral

Land use and infrastructure

(2/3 of highway fuel) 246 5 10 3 5

System efficiency

(25% LDV fuel) 72 2 5 0 1

Climate change education

(All transportation fuel) 489 1 2 1 2

Fuel economy information

(All LDV fuel) 289 1 2 1 1

Total 489 22 48

Notes:

a Carbon emissions for the year 2000 are used to weight percent reductions for the respective emissions source and example policy 

category in calculating total percent reduction potential. The elasticity of vehicle travel with respect to fuel price is –0.15 for all modes. 

Price elasticity of energy efficiency with respect to fuel price is –0.4.

b R&D efficiency improvements have no direct effect on total. Their influence is seen through efficiency standards impacts.

Policies affecting the same target emissions, such as passenger car efficiency, low carbon fuels, and land-use policies are multiplicative, to 

avoid double counting (e.g. [1–0.1]*[1.0–0.2] = 1–0.28, a 28% rather than a 30% reduction.)

Table 7.5 Potential impacts of transportation GHG reduction policies in the United States by 2015 and 2030a based 

on the 2000 distribution of emissions by mode and fuel (Greene and Shafer, 2003).
83

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

policies shift the incidence but do not increase the overall 

cost of transportation, and (4) there is a carbon cap and trade 

system in effect equivalent to a charge of approximately 

$50/t C. Similar premises underlie the 2030 estimates, except 

that technological progress is assumed to have expanded 

the potential for efficiency improvement and lowered the 

cost of biofuels.

The Pew Center study notes that if transportation demand 

continues to grow as the IEO 2005 and WBCSD projections 

anticipate, the potential reductions shown in Table 7.4 would 

be just large enough to hold United States transportation 

CO2 emissions in 2030 to 2000 levels.

A study for the U.S. Department of Energy (ILWG, 2000) 

produced estimates of carbon mitigation potential for the 

entire United States economy using a variety of policies 

generally consistent with carbon taxes of $25-$50/t C. 

In the study’s business as usual case, transportation CO2

emissions increased from 478 Mt C in 1997 to 700 Mt C 

in 2020. A combination of technological advances, greater 

use of biofuel, fuel economy standards, paying for a portion of automobile insurance as a surcharge on gasoline, 

and others, were estimated to reduce 2020 transportation 

CO2 emissions by 155 Mt C to 545 Mt CO2. The study did 

not produce cost estimates and did not consider impacts on 

global energy markets.

A joint study of the U.S. Department of Energy and Natural 

Resources Canada (Patterson et al., 2003) considered alternative scenarios of highway energy use in the two countries 

to 2050. The study did not produce estimates of cost-effectiveness for GHG reduction strategies but rather focused on 

the potential impacts of differing social, economic, and technological trends. Two of the scenarios describe paths that 

lead to essentially constant GHG emissions from highway 

vehicles through 2050 through greatly increased efficiency 

and biofuel and hydrogen use and, 

in one scenario, reduced demand for 

vehicle travel.

7.5 INCONSISTENCIES 

AND UNCERTAINTIES

There are some inconsistencies in 

the way the three North American 

countries report transportation carbon emissions. The principal source 

for Mexican emissions data breaks 

out transportation into four modes 

(road, air, rail, and waterborne), 

it does not report emissions for 

pipelines but does report emissions 

from use of international bunker 

fuels. The United States and Canada report transport emissions in much greater modal detail, by vehicle type and fuel 

type within modes. The United States and Mexico report 

emissions from international bunker fuels in their national 

inventory reports, while Canada does not. Estimates of international bunker fuel emissions for Canada presented in 

this chapter were derived by subtracting Air and Waterborne 

emissions reported by Environment Canada (2005a) which 

exclude international bunker fuels from total air and waterborne emissions as reported by Natural Resources Canada 

(2006) which include them. Environment Canada reports 

off-road emissions from mobile sources separately; in the 

tables and figures in this chapter, Canadian off-road emissions have been added to road emissions. Both Canada and 

the United States include emissions from military transport 

operations in their inventories. It is not clear whether these 

are included in the estimates for Mexico.

All three countries’ GHG inventories discuss uncertainties in estimated emissions. In general, the uncertainties 

were estimated in accordance with IPCC guidelines. The 

U.S. EPA provides only an estimate of a 95% confidence 

Source: Environment Canada (2005a), table A7-9.

Mode % Below

(2.5th Percentile)

% Above

(97.5th Percentile)

Total Mobile Sources excluding pipeline -4 0

Road Transportation -8 -3

On-Road Gasoline Vehicles -7 -3

On-Road Diesel Vehicles -13 -1

Railways -5 3

Navigation -3 3

Off-Road Mobile Sources 4 45

Pipeline -3 3

Table 7.6 Uncertainty in estimates of carbon dioxide emissions from energy 

use in transport: Canada (2003).
The U.S. Climate Change Science Program Chapter 7

84 

interval for all CO2 emissions from the combustion of 

fossil fuels (-1% to 6%) which can be inferred to apply to 

transportation. Mexico’s INE estimates a total uncertainty 

for transportation GHG emissions of about ± 10%. For CO2

emissions from road transport, the uncertainty is put at ± 

9% (INE, 2003, Appendix B). The Canadian Greenhouse 

Gas Inventory provides by far the most extensive and 

detailed estimates of uncertainty. Given the similarity in 

methods, the Canadian uncertainty estimates are probably also approximately correct for the United States, and 

therefore may be considered indicative of the uncertainty 

of North American carbon emission estimates (Table 7.6). 

Most significant is the apparent overestimation of carbon 

emissions from on-road vehicles, offset to a degree by the 

underestimation of off-road mobile source emissions. Still, 

total mobile source carbon emissions are estimated to have 

a 95% confidence interval of (-4% to 0%).

7.6 RESEARCH AND DEVELOPMENT 

NEEDS

Research needs with respect to the transport sector as a part 

of the carbon cycle fall into three categories: (1) improved 

data, (2) comprehensive assessments of mitigation potential, and (3) advances in 

key mitigation technologies 

and policies for transportation. The available data are 

adequate to describe carbon inputs by fuel type and 

carbon emissions by very 

broad modal breakdowns 

by country. Environment 

Canada (2005a) and the U.S. 

Environmental Protection 

Agency (2005) annually publish estimates of transportation’s 

carbon emissions that closely follow IPCC guidelines with 

respect to methods, data sources, and quantification of uncertainties (GAO, 2003). The Mexican Instituto Nacional 

de Ecología has published estimates for 2001 that are also 

based on IPCC methods. However, that report also notes 

deficiencies in the data available for Mexico’s transport 

sector and recommends establishing an information system 

for estimating Mexico’s transportation GHG emissions on 

a continuing basis (INE, 2003, p. 21). Knowledge of the 

magnitude of GHG emissions by type of activity and fuel, 

and of trends is essential if policies are to be focused on the 

most important GHG sources.

The most pressing research need is for comprehensive, consistent, and rigorous assessments of the carbon emissions 

mitigation potential for North American transportation. The 

lack of such studies for North America parallels a similar 

dearth of consistent and comprehensive global analyses 

noted by the IPCC (Moomaw and Moreira, 2001). Existing 

studies focus almost exclusively on a single country, with 

premises and assumptions varying widely from country to 

country. Even the best single country studies omit the impacts of carbon reduction policies on global energy markets. 

Knowledge of how much contribution the transport sector 

can make to GHG mitigation, at what cost, and what options 

are capable of achieving those potentials is crucial to the 

global GHG policy discussion.

Continued research and development of vehicle technologies 

and fuels that can cost-effectively increase energy efficiency 

and displace carbon-based fuels is essential to achieving 

major reductions in transportation carbon emissions. Highly 

promising technologies for reducing transportation GHG 

emissions include hybrid vehicles, which are available today, 

and in the future, plug-in hybrid vehicles capable of accepting electrical energy from the grid, and eventually fuel cell 

vehicles powered by hydrogen. While hybrids are already 

in the market and fuel cell vehicles are still years away, all 

three technologies would benefit from cost reduction. Hydrogen fuel cell vehicles also face significant technological 

challenges with respect to hydrogen storage and fuel cell 

durability. Energy-efficient technologies could also greatly 

reduce GHG emissions from other transport modes. For 

example, blended wing-body aircraft designs are under 

development that could reduce fuel burn rates by one-third. 

Biofuels in the near term and hydrogen in the longer term 

appear to be the most promising low-carbon fuel options. To 

achieve the greatest GHG reduction benefits, biofuels must 

be made from plants’ ligno-cellulosic components either 

by conversion to alcohol or by gasification and synthesis of 

liquid hydrocarbon fuels. Cost reductions in both feedstock 

production and fuel conversion are needed.

The most pressing research 

need is for comprehensive, 

consistent, and rigorous 

assessments of the carbon 

emissions mitigation 

potential for North 

American transportation.
Industry and Waste Management

CHAPTER

8

85

The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

KEY FINDINGS

Lead Author: John Nyboer, Simon Fraser Univ.

Contributing Authors: Mark Jaccard, Simon Fraser Univ.; 

Ernst Worrell, LBNL

In 2002, North America’s industry (not including fossil-fuel mining and processing or electricity generation) contributed 225 million metric tons of carbon (826 million tons of carbon dioxide), 16% of the world’s carbon dioxide 

emissions to the atmosphere from industry. Waste treatment plants and landfill sites in North America accounted 

for 13.4 million tons of methane (282 million tons of carbon dioxide equivalent; 10 million tons of carbon), roughly 

20% of global totals.

Industrial carbon dioxide emissions from North America decreased nearly 11% between 1990 and 2002, while energy 

consumption in the United States and Canada increased 8% to 10% during that period. In both countries, a shift in 

production activity toward less energy-intensive industries and dissemination of more energy efficient equipment 

kept the rate of energy demand growth lower than industrial gross domestic product growth.

Changes in industrial carbon dioxide emissions are a consequence of changes in industrial energy demand and changes 

in the mix of fossil fuels used by industry to supply that demand. Changes in industrial energy demand are themselves 

a consequence of changes in total industrial output, shifts in the relative shares of industrial sectors, and increases 

in energy efficiency. Shifts from coal and refined petroleum products to natural gas and electricity contributed to a 

decline in total industrial carbon dioxide emissions since 1997 in both Canada and the United States.

An increase in carbon dioxide emissions from North American industry is likely to accompany the forecasted increase 

in industrial activity (2.3% per year until 2025 for the United States). 

Emissions per unit of industrial activity will likely decline as non-energy intensive industries grow faster than energy 

intensive industries and with increased penetration of energy efficient equipment. However, continuation of the trend 

toward less carbon-intensive fuels is uncertain given the rise in natural gas prices relative to coal in recent years.

Options for reducing carbon dioxide emissions from North American industry can be broadly classified as methods to: 

(1) reduce process/fugitive emissions or convert currently released emissions; (2) increase energy efficiency, including 

combined heat and power management; (3) change industrial processes (materials efficiency, recycling, substitution 

between materials or between materials and energy, and 

nanotechnology); (4) substitute less carbon intense fuels; 

and (5) capture and store carbon dioxide.

Further work on materials substitution holds promise for 

industrial emissions reduction, such as the replacement 

of petrochemical feedstocks by feedstocks derived from 

vegetative matter (biomass), of steel by aluminum in the 

transport sector, and of concrete by wood in the buildings 

sector. The prospects for greater usage of energy efficiency 

technologies are equally substantial.

•

•

•

•

•

•

•
The U.S. Climate Change Science Program Chapter 8

86 

8.1 Introduction

This chapter assesses carbon flows through industry (manufacturing and construction including 

industry process emissions, but excluding fossilfuel mining and processing)1

 and municipal waste 

disposal.

In 2002, industry was 

responsible for 1423.8 

million metric tons of 

carbon (Mt C) (5220.6 

million tons of carbon dioxide [Mt CO2]), 

which is 21% of human-caused (anthropogenic) emissions to the 

atmosphere (244.8 Mt C [4322.9 Mt CO2] from fuel 

combustion and 1179.0 Mt C [897.7 Mt CO2] from 

industrial processes). North America’s industry 

contributed 206.9 Mt C (758.7 Mt CO2) of combustion-sourced emissions and 18.2 Mt C (66.8 Mt 

CO2) of process emissions for a total of 225 Mt C 

(826 Mt CO2) or 16% of global totals (WRI, 2005; 

see Figure 8.1A)2 †. The manufacturing industry 

contributed 12% of total North American greenhouse gas (GHG) emissions, lower than in many 

other parts of the world. However, with North 

America’s population at 6.8% of the world’s total, 

industry contributed a proportionally larger share 

of total industrial emissions per capita than the 

rest of the world3. 

Industrial CO2 emissions decreased nearly 11% between 

1990 and 2002 while energy consumption in the United 

States and Canada increased 8% to 10% (EIA, 2005; CIEEDAC, 2005). In both countries, a shift in production activity 

toward less energy-intensive industries and dissemination of 

more energy efficient equipment kept the rate of growth in 

energy demand lower than industrial gross domestic product 

(GDP) growth (IEA, 2004)4. This slower demand growth, 

in concert with a shift toward less carbon-intensive fuels, 

explains the decrease in industrial CO2 emissions.

The municipal waste stream excludes agricultural and 

forestry wastes but includes wastewater. Carbon dioxide, 

generated from aerobic metabolism in waste removal and 

1

 This includes direct flows only. Indirect carbon flows (e.g., due to 

electricity generation) are associated with power generation. 

2 † A dagger symbol indicates that the magnitude and/or range of 

uncertainty for the given numerical value(s) is not provided in the 

references cited.

3

 North America, including Mexico, was responsible for about 27% 

of global CO2 emissions in 2002. 4

 Decomposition analyses can assess changes in energy consumption 

due to, for example, increases in industry activity, changes in relative 

productivity to or from more intense industry subsectors, or changes 

in material or energy efficiency in processes.

storage processes, arises from biological material and is 

considered GHG neutral. Methane (CH4) released from 

anaerobic activity at waste treatment plants and landfill 

sites, forms a substantial portion of carbon emissions to 

the atmosphere. Given its high global warming potential 

(GWP) (i.e., the GWP for CH4 is 21 times that of CO2), CH4

plays an important role in the evaluation of possible climate 

change impacts (WRI, 2005; see Figure 8.1B)5 †. Globally, 

CH4 emissions from waste amount to 66 Mt, or 378 Mt C 

equivalent (1386 Mt CO2 equivalent). North American activity accounts for 13.4 Mt of CH4 (77 Mt C equivalent [282 Mt 

CO2 equivalent]) or roughly 20% of global totals. 

Substantial sequestration of carbon occurs in landfills6.

Data on carbon buried there are poor. The Environmental 

Protection Agency (EPA), using data from Barlaz and Ham 

(1990) and Barlaz (1994), estimated that 30% of carbon in 

food waste and up to 80% of carbon in newsprint, leaves, and 

5

 While not carbon-based, N2O from sewage treatment is included in 

Figure 8.4, below, to show its relative GHG importance.

6

 IPCC guidelines currently do not address landfill sequestration. 

Such guidelines will be in the 2006 publication.

In 2002, industry was 

responsible for 21% 

of human-caused 

(anthropogenic) emissions 

to the atmosphere. 

Figure 8.1A Carbon dioxide emissions by sector in 2002. Source: WRI 

(World Resources Institute)(2005). The magnitude and/or range of uncertainty for the given numerical values is not provided in the reference. To 

convert from Mt CO2 to MtC, multiply the Mt CO2 value by 12/44.
87

The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

branches remain in the landfill†. Plastics show no deterioration. In all, 80% of the carbon entering a landfill site may 

be sequestered, depending on moisture, aeration, and site 

conditions. Bogner and Spokas (1993) estimate that “more 

than 75% of the carbon deposited in landfills remains in 

sedimentary storage.”

8.2 Industry Carbon Cycle

Carbon may enter industry as a fuel or as a feedstock where 

the carbon becomes entrained in the industry’s final product. 

Carbon in the waste stream can be distinguished as atmospheric and non-atmospheric, the former being comprised 

of process and combustion-related emissions. Process CO2

emissions, a non-combustive source, are the result of the 

transformation of the material inputs to the production 

process. For example, cement production involves the calcination of lime, which chemically alters limestone to form 

calcium oxide and releases CO2. Of course, combustionrelated CO2 emissions occur when carbon-based 

fuels provide thermal energy to drive industrial 

processes.

8.2.1 Overview of Carbon Inputs and Outputs

Industry generates about one-third as much emitted carbon as the production of electricity and 

other fuel supply in North America and only about 

55% as much as is generated by the transportation 

sector.

 8.2.1.1 Carbon In

 Carbon-based raw materials typically enter industrial sites as biomass (primarily wood), limestone, 

soda ash, oil products, coal/coke, natural gas, and 

natural gas liquids. These inputs are converted to 

dimension lumber and other wood products, paper 

and paperboard, cement and lime, glass, and a host 

of chemical products, plastics, and fertilizers.

While the bulk of the input carbon leaves the industrial site as a product, some leaves as process CO2

and some is converted to combustible fuel. Waste 

wood (or hog fuel) and black liquor, generated in 

the production of chemical pulps, are burned to 

provide process heat or steam for digesting wood 

chips or for drying paper or wood products, in some 

cases providing electricity through cogeneration. 

Chemical processes utilizing natural gas often 

generate off-gases that, mixed with conventional 

fuels, provide process heat. Finally, some of the 

carbon that enters as a feedstock leaves as solid or 

liquid waste.

In some industries, carbon is used to remove oxygen from 

other input materials through “reduction.” In most of the 

literature, such carbon is considered an input to the process 

and is released as “process” CO2, even though it acts as a 

fuel (i.e., it unites with oxygen to form CO2 and releases 

heat). For example, in metal smelting and refining processes, 

a carbon-based reductant separates oxygen from the metal 

atoms. Coke, from the destructive distillation of coal, enters 

a blast furnace with iron ore to strip off the oxygen associated with the iron. Carbon anodes in electric arc furnaces 

in steel mills and specialized electrolytic “Hall-Heroult” 

cells oxidize to CO2 as they melt recycled steel or reduce 

alumina to aluminum.

8.2.1.2 Carbon Out

Carbon leaves industry as part of the intended commodity 

or product, as a waste product or as a gas, usually CO2.

Figure 8.1B Greenhouse gas emissions by sector in 2000, CO2, 

CH4, N2O, PFCs, HFCs, and SF6. Source: WRI (World Resources Institute)(2005). The magnitude and or range of uncertainty for the given 

numerical values is not provided in the reference. To convert from MtCO2

equivalent to MtC equivalent, multiply the Mt CO2 value by 12/44.
The U.S. Climate Change Science Program Chapter 8

88 

Process emissions are CO2 emissions that 

occur as a result of the process itself—the 

calcining of limestone releases about 0.5 

tons CO2 per ton of clinker (unground cement) or about 0.8 tons per ton of lime7,8

. 

The oxidation of carbon anodes generates 

about 1.5 tons CO2 to produce a ton of 

aluminum. Stripping hydrogen from CH4

to make ammonia releases about 1.6 tons 

CO2 per ton of ammonia.

Combustion 

of c a r b o n -

based f uels 

results in the 

emission of 

CO2. In many 

c a s e s , t h e 

combustion 

process is not 

complete and 

other carbonbased compounds may 

be released (carbon monoxide, CH4, 

volatile organic compounds). These often 

decompose into CO2, but their life spans 

in the atmosphere vary.

8.2.1.3 Carbon Flow

Figure 8.2 illustrates the flows of carbon 

in and out of industries in North America. 

Comparable diagrams for individual countries are presented 

in Appendix C. On the left side of Figure 8.2, all carbonbased material by industry sector is accounted for, whether 

in fuel or in feedstock. On the right, the exiting arrows 

portray how much of the carbon leaves as part of the final 

products from that industry. The carbon in the fossil fuel 

and feedstock materials leave in the waste stream as emissions from fuel combustion (including biomass), as process 

emissions, or as other products and waste. Carbon capture 

and storage potentials are assessed in the industry subsections below.

8.2.2 Sectoral Trends in the 

Industrial Carbon Cycle 

Figure 8.2 shows that energy-intensive industries differ 

significantly in their carbon cycle dynamics.

7

 In these industries, more CO2 is generated from processing limestone 

than from the fossils fuels combusted. 

8

 The calcination of limestone also takes place in steel, pulp and paper, 

glass, and sugar industries.

8.2.2.1 Pulp and Paper

While pulp and paper products are quite energy-intensive, 

much of the energy is obtained from biomass. By using hog 

fuel and black liquor, some types of pulp mills are energy 

self-sufficient. Biomass fuels are considered carbon neutral 

because return of the biomass carbon to the atmosphere 

completes a cycle that began with carbon uptake from the 

atmosphere by vegetation9. Fuel handling difficulties and 

air quality concerns can arise from the use of biomass as 

a fuel.

8.2.2.2 Cement, Lime, and Other

Nonmetallic Minerals

Cement and lime production require the calcination of 

limestone, which releases CO2; about 0.78 tons of CO2 per 

ton of lime calcined.

 CaCO3 → CaO + CO2

calcium carbonate calcium oxide carbon dioxide

9

 This is also reflected in the United Nations Framework Convention 

on Climate Change (UNFCCC) IPCC guidelines to estimate CO2

emissions.

Figure 8.2 Carbon flows for Canada, the United States, and Mexico combined. 

Values in megatons carbon can be converted to megatons CO2 equivalents by multiplying by 44/12; the ratio of CO2 mass to carbon mass. Comparable diagrams for the 

individual countries are in Appendix C. Source: Energy data from Statistics Canada 

Industrial Consumption of Energy survey, Conversion coefficients, IEA Oil Information (2004), IEA Coal Information (2005), IEA Natural Gas Information (2004). 

Process emissions from Environment Canada, Canada GHG Inventory (2002), EPA, 

U.S. Emissions Inventory. Production data from Statistics Canada, CANSIM Table 

002-0010, Tables 303-0010, -0014 to -0021, -0024, -0060, Pub. Cat. Nos.: 21-020, 

26-002, 45-002, Canadian Pulp and Paper Association on forestry products. Production of forestry products: USDA Database; FO-2471000, -2472010, -2482000, 

-2483040, -6342000, -6342040, U.S. Timber Production, Trade, Consumption, and 

Price Statistics 1965-2005. Production of organic products (e.g., food): USDA PS&D 

Official Statistical Results. Steel: International Iron and Steel Institute, World steel 

in figures (2003). Minerals production: USGS mineral publications.

Biomass fuels are 

considered carbon neutral 

because return of the 

biomass carbon to the 

atmosphere completes 

a cycle that began with 

carbon uptake from the 

atmosphere by vegetation. 
89

The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

Outside of the combustion of fossil fuels, lime calcining is 

the single largest human-caused source of CO2 emissions. 

Annual growth in cement production is forecast at 2.4% in 

the United States for at least the next decade. This industry 

could potentially utilize sequestration technologies to capture and store CO2 generated.

The production of soda ash (sodium carbonate) from sodium 

bicarbonate in the Solvay process releases CO2, as in glass 

production, in its utilization. Soda ash is used to produce 

pulp and paper, detergents, and soft water.

 2NaHCO3 → Na2CO3 + CO2 + 

sodium bicarbonate sodium carbonate carbon dioxide

 H2O 

 water

8.2.2.3 Nonferrous Metal Smelting and Iron and

Steel Smelting

Often metal smelting requires the reduction of metal oxides 

to obtain pure metal through use of a “reductant”, usually 

coke. Because reduction processes generate relatively pure 

streams of CO2, the potential for capture and storage is 

good.

In electric arc furnaces, carbon anodes decompose to CO2

as they melt the scrap iron and steel feed in “mini-mills”. In 

Hall-Heroult cells, a carbon anode oxidizes when an electric 

current forces oxygen from aluminum oxide (alumina) in the 

production of aluminum10.

8.2.2.4 Metal and Nonmetal Mining

Mining involves the extraction of ore and its transformation 

into a concentrated form. This involves transportation from 

mine site, milling, and separating mineral-bearing material 

from the ore. Some transportation depends on truck activity, 

but the grinding process is driven by electric motors (i.e., 

indirect release of CO2). Some processes, like the sintering 

or agglomeration of iron ore and the liquid extraction of 

potash, use a considerable amount of fossil fuels directly.

8.2.2.5 Chemical Products

This diverse group of industries includes energy-intensive 

electrolytic processes as well as the consumption of large 

quantities of natural gas as a feedstock to produce commodities like ammonia, methanol, and hydrogen. Ethylene and 

propylene monomers from natural gas liquids are used in 

plastics production. Some chemical processes generate fairly 

pure streams of CO2 suitable for capture and storage.

10 Ceramic anodes may soon be available to aluminum producers and 

significantly reduce process CO2 emissions.

8.2.2.6 Forest Products

This industry uses biomass waste to dry commercial products such as lumber, plywood, and other products. The 

industry also includes silviculture, the practice of replanting 

and managing forests.

8.2.2.7 Other Manufacturing

Most of the remaining industries, while economically important, individually play a relatively minor role in the carbon 

cycle because they are not energy intensive and use little 

biomass11. In aggregate, however, these various industries 

contribute significantly to total industrial CO2 emissions. 

Industries in this group include the automotive industry, 

electronic products, leather and allied products, fabricated 

metals, furniture and related products, and plastics and 

rubber products.

8.2.3 Changing Role of 

Industry in the Carbon Cycle

Energy consumption per unit GDP has declined in Canada 

and the United States by more than 30% since the mid-1970s. 

In manufacturing, the decline was even greater—more than 

50% in the United States since 1974.

The National Energy Modeling System operated by the 

United States’ Energy Information Administration applies growth forecasts from` 

the Global Insight macroeconomic model. While the 

United States economy is 

forecast to grow at an aver 

age rate of 3.1% per year to 

2025, industrial growth is 

forecast at 2.3% per year—

an amalgam of manufactur11 Except, of course, the food, beverage, and some textile industries.

The shift from coal 

and refined petroleum 

products to natural gas 

and electricity contributed 

to a decline in total 

industrial CO2 emissions 

since 1997 in both Canada 

and the United States.
The U.S. Climate Change Science Program Chapter 8

90 

ing growth of 2.6% per year and 

non-manufacturing of 1.5% per 

year. Manufacturing is further 

disaggregated into energy-intensive industries, growing at 

1.5% per year, and non-energy 

intensive industries at 2.9% 

per year. The slower growth in 

the energy-intensive industries is reflected in the expected 

decline in industrial energy intensity of 1.6% per year over 

the EIA (2005) forecast.

The International Energy Agency reviewed energy consumption and emissions during the last 30 years to identify 

and project underlying trends in carbon intensity12. The 

review’s decomposition analysis (Figure 8.3) attributes 

changes in industrial energy demand to changes in total 

industrial output (activity), shifts in the relative shares of 

industrial sectors (structure), and increases in energy efficiency (intensity).

Changes in carbon emissions result from these three factors, but also from changes in fuel shares—substitution 

away from or toward more carbon-intensive fuels. The shift 

from coal and refined petroleum products to natural gas and 

electricity13 contributed to a decline in total industrial CO2

emissions since 1997 in both Canada and the United States. 

The continuation of this trend is uncertain given the rise in 

natural gas prices relative to coal in recent years.

12 Most of the information in this section is obtained from IEA 

(2004).

13 As noted earlier, emissions associated with electricity are allocated 

to the electricity supply sector. Thus a shift to electricity reduces the 

GHG intensity of the industry using it. If electricity is made in coalfired plants, however, total CO2 emissions may actually increase.

8.2.4 Actions and Policies for Carbon Management in Industry

Industry managers can reduce carbon flows through industry by altering the material or energy intensity and character 

of production (IPCC, 2001). Greater materials efficiency 

typically reduces energy demands in processing because of 

reduced materials handling. For example, recycling materials often reduces energy consumption per unit of output by 

26 to 95% (Table 8.1). Further work on materials substitution 

also holds promise for reduced energy consumption and 

emissions reduction14.

The prospects for greater energy efficiency are equally substantial. Martin et al. (2001) characterized more than 50 key 

emerging energy efficient technologies, including efficient 

Hall-Heroult cell retrofits, black liquor gasification in pulp 

production, and shape casting in steel industries. Worrell et 

al. (2004) covers many of the same technologies and notes 

that significant potential exists in utilizing efficient motor 

systems and advanced cogeneration technologies.

At the same time, energy is a valuable production input 

that, along with capital, can substitute for labor as a means 

of increasing productivity. Thus overall productivity gains 

in industry can be both energy-saving and energy-augmenting, and the net impact depends on the 

nature of technological innovation and the 

expected long-run cost of energy relative to 

other inputs. This suggests that, if policies to 

manage carbon emissions from industry were 

to be effective, they would need to provide a 

significant signal to technology innovators 

and adopters to reflect the negative value that 

society places on carbon emissions. This in 

turn suggests the application of regulations or 

financial instruments, examples being energy 

efficiency regulations, carbon management 

regulations, and fees on carbon emissions.

8.3 Waste Management

Carbon Cycle

The carbon cycle associated with human 

wastes includes industrial, commercial, 

14 For example, substitute petrochemical feedstocks by biomass or 

concrete by wood in home foundations.

Figure 8.3 Decomposition of energy use, manufacturing section, 1990-1998. 

Source: IEA (2004).

Table 8.1 Energy reductions in recycling.

Source: Hershkowitz (1997)

Recycled material Energy saved Recycled material Energy saved

Aluminum 95% Glass 31%

Tissue paper 54% Newsprint 45%

Printing/writing paper 35% Corrugated cardboard 26%

Plastics 57%–75% Steel 61%
91

The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

construction, demolition, 

and residential waste. 

Municipal solid waste 

cont ai ns sig n if ica nt 

amounts of carbon. Paper, 

plastics, yard trimmings, 

food scraps, wood, rubber, and textiles made 

up more than 80% of the 

236 Mt of municipal solid 

waste generated in the 

United States in 2003 

(EPA, 2005) and the 25 

Mt generated in Canada 

(Statistics Canada, 2004), 

as shown in Table 8.2. In 

Mexico, as much as 20% 

of wastes are not systematically collected; no disaggregated 

data are available (EPA, 2005).

A portion of municipal solid waste is recycled: 31% in the 

United States (EPA, 2003b)†

 and 27% in Canada (Statistics Canada, 2004).† Up to 14% of the remaining waste is 

incinerated in the United States, slightly less in Canada. 

Incineration can reduce the waste stream by up to 80%, but 

this ensures that more of the carbon reaches the atmosphere 

as opposed to being sequestered (or subsequently released 

as CH4) in a landfill. Incineration, however, can be used to 

cogenerate electricity and useful heat, which may reduce 

carbon emissions from stand-alone facilities.

Once in a landfill, carbon in wastes may be acted upon 

biologically, releasing roughly equal amounts of CO2 and 

CH4 by volume15 depending on ambient conditions, as well 

as a trace amount of carbon monoxide and volatile organic 

compounds. While no direct data on the quantity of CO2

released from landfills exists, one can estimate the CO2

released by using this ratio; the estimated amount of CO2

released from landfills in Canada and the United States (no 

data from Mexico) would be approximately 38 Mt16, a relatively small amount compared to the total of other subsectors 

in this chapter. Also, recall that these emissions are from 

biomass and, in the context of IPCC assessment guidelines, 

are considered GHG-neutral.

Depending on the degree to which aerobic or anaerobic 

metabolism takes place, a considerable amount of carbon 

remains unaltered and more or less permanently stored in 

the landfill (75%-80%; see Barlaz and Ham, 1990; Barlaz, 

15 Based on gas volumes, this means that roughly equivalent amounts 

of carbon are released as CO2 as CH4. 16 14 Mt of CH4 (see Table 8.3) are equivalent, volume wise at standard 

temperature and pressure, to 38 Mt of CO2. This derived estimate is 

highly uncertain and not of the same caliber as other emissions data 

provided here.

1994; and Bogner and 

Spokas, 1993). Because 

data on the proportions of 

carboniferous material entering landfills can be estimated, 

approximate carbon contents of these materials can be determined and the degree to which these materials can decompose, it would be possible to estimate the amount of carbon 

sequestered in a landfill site (see EPIC, 2002; Mohareb et al., 

2004; EPA, 2003b; EPA, 2005). While EPA (2005) provides 

an estimate of carbon sequestered in US landfills (see Table 

8.2), no data are available for other regions.

Anaerobic digestion generates CH4 gases that can be captured and used in cogenerators. Many of the 1800 municipal 

solid waste sites in 2003 in the United States captured and 

combusted landfill-generated CH4; about half of all the CH4

produced was combusted or oxidized in some way (EPA, 

2005). In Canada, about 23% of the CH4 emissions were captured and utilized to make energy in 2002 (Mohareb et al., 

2004). The resultant CO2 released from such combustion is 

considered biological in origin. Thus only CH4 emissions, at 

21 times the CO2 warming potential, are included as part of 

GHG inventories. Their combustion greatly alleviates the net 

contribution to GHG emissions and, if used in cogeneration, 

may offset the combustion of fossil fuels elsewhere. Figure 

8.4 provides an estimate of CH4 (and nitrous oxide [N2O] as 

the other GHG for comparison) released from landfills and 

waste treatment facilities. 

8.4 Costs Related to Controlling

human-caused Impacts on the

Carbon Cycle

Defining costs associated with reducing human-caused 

(anthropogenic) impacts on the carbon cycle is a highly 

contentious issue. Different approaches to cost assessments 

(top-down, bottom-up, applicable discount rates, social 

United States Canada Mexico

Total waste (Mt per year) 236.0 24.8 29.2

Recycled 72.0 6.6 –

Carbon-based waste 197.1 19.6 –

Carbon-based waste recycled 47.3a 4.3 –

Carbon sequestered (CO2 equivalents) 10.1 – –

Methane (kt per year) 

Generated 12,486 1,452 –

Captured, oxidized 6,239 336 –

Emitted 6,247 1,117 –

Emitted (CO2 equivalents) 131,187 23,453 –

Table 8.2 Waste materials flows by region in North America, 2003.

a

 Calculated estimate

Source: EPA (2003b, 2005), Statistics Canada (2004), Mohareb (2004) for Canada methane data, California 

Evironmental Protection Agency (2003) for Mexico data point.

Municipal solid waste contains 

significant amounts of carbon.
The U.S. Climate Change Science Program Chapter 8

92 

• reducing or altering process/fugitive emissions,

• energy efficiency, including combined heat and 

power,

• process changes,

• fuel substitution,

• carbon capture and storage.

One can attribute potential reductions over a set 

time under a range of costs. We suggest the costrange categories (“A” through “D”) shown in Table 

8.3. The table contains estimates of the percentage 

reduction by industry under these cost categories. 

Costs are not drawn from a single source but are 

the authors’ estimates based on a long history of 

costs reported in various documents17. Some studies focus on technical potential and do not provide 

the cost of achieving the reductions. As such, 

achievable reductions are likely overestimated. 

Others describe optimization models that provide 

normative costs and likely overestimate potentials 

and underestimate costs. Still others use top-down 

approaches where historic data sets are used to determine relationships between emissions and factors 

of production; costs are often high and emissions 

reductions underestimated.

When looking at cost numbers like this, one should 

remember that, for each $10 cost increment per t 

CO2 (or about $37 per t C), gasoline prices would 

increase about 2.4¢/L (9¢/U.S. gallon). Diesel fuel 

cost would be nearly 2.7¢/L (10¢/U.S. gallon). Costs 

per Gigajoule (GJ)18 vary by fuel: coal rises about 

90¢/GJ, depending on type, heavy fuel oil (HFO) 

by 73¢, and natural gas by 50¢. At 35% efficiency, 

coal-fired electricity generation would be about 

0.8¢/kWh higher, about 0.65¢/kWh for HFO, and about 

0.45¢/kWh for natural gas.

Of course, as the cost of carbon increases, one moves up 

the carbon supply curve for industrial sectors. However, 

reductions become marginal or insignificant and so are not 

included in Table 8.3. If a cell in Table 8.3 shows two cost 

categories (e.g., A/B) and two reduction levels (%Qred is 

15/20), the value associated with the second portrays the additional reduction at that increased expenditure level. Thus 

spending up to $50/t CO2 to improving efficiency in metal 

smelting implies a potential reduction of 35% (see Table 8.3). 

Reductions in each category are not additive for an industry 

type because categories are not independent.

17 Studies vary widely in how they define system boundaries, baseline, 

and time periods, which sectors or subsectors are included, economic 

assumptions, and many other factors. See `Some Explanatory Notes`

in Section 8.4.1 for a list.

18 A Gigajoule (GJ), or one billion joules, is slightly smaller than 1 

MMBtu (1 GJ = 0.948 MMBtu).

costing, cost effectiveness, no regrets), different understandings of what costs include (risk, welfare, intangibles, 

capital investment cycles), different values associated with 

energy demand in different countries (accessibility, availability, infrastructure, resource type and size), actions and 

technologies included in the analysis, and the perspective 

on technology development all have an impact on evaluating 

costs. Should analysts consider only historical responses to 

energy prices, production and demand elasticities, or income changes? Does one consider only technology options 

and their strict financial costs or see historic technology 

investments as sunk costs? Should one include producers’ 

or consumers’ welfare? Are there local, national, international issues?

Cost variation within industries is significant. Costs associated with various methods to reduce emissions also vary. 

Reduction methods can be classified as:

Figure 8.4 Greenhouse gas emissions by gas from waste in 2000. Source: 

WRI (World Resources Institute) (2005). The magnitude and/or range of 

uncertainty for the given numerical values is not provided in the reference. 

To convert from Mt CO2 equivalent to Mt C equivalent, multiply the Mt 

CO2 value by 12/44. 
93

The First State of the Carbon Cycle Report (SOCCR)-

The North American Carbon Budget and Implications for the Global Carbon Cycle

Because not all reduction methods are applicable to all 

industries, as one aggregates to an “all industry” level (top 

line, Table 8.3), the total overall emissions reduction level 

may be less than any of the individual industries sited.

8.4.1 Some Explanatory Notes

Data come from a variety of sources and do not delineate 

costs as per the categories described here. Data sources can 

be notionally categorized into the following groups (with 

some references listed twice)19:

• General overviews: Grubb et al. (1993), Weyant et al. 

(1999)20, Grubb et al. (2002), Löschel (2002).

• Top-down analyses: McKitrick (1996), Herzog (1999), 

Sands (2002), McFarland et al. (2004), Schäfer and Jacoby 

(2005), Matysek et al. (2006).

• Bottom up analyses: Martin et al. (2001), Humphreys and 

Mahasenan (2002), Worrell et al. (2004), Kim and Worrell (2002), Morris et al. (2002), Jaccard et al. (2003a), 

DOE (2006), IEA (2006).

• Hybrid model analyses: Böhringer (1998), Jacobsen 

(1998), Edmonds et al. (2000), Koopmans and te Velde 

(2001), Jaccard (2002), Frei et al. (2003), Jaccard et al.

(2003a), Jaccard et al. (2003b), Edenhofer et al. (2006).

• Others: Newell et al. (1999), Sutherland (2000), Jaffe et 

al. (2002).

19 Two authors are currently involved with IPCC’s upcoming fourth 

assessment report where estimated costs of reduction are provided. 

Preliminary reviews of the cost data presented there do not differ 

substantially from those in table 8.3.

20 John Weyant of Stanford University is currently editing another 

analysis similar to this listed publication to be released in the near 

future. 

8.4.1.1 Process and Fugitives

Process and fugitive reductions are only available in certain 

industries. For example, because wood-products industries 

burn biomass, fugitives are higher than in other industries 

and reduction potentials exist.

In the waste sector, the reductions potentials are very large; 

we have simply estimated possible reductions if we were to 

trap and burn all landfill CH4. The costs for this are quite 

low. EPA (2003a) estimates of between 40% and 60% of CH4

available for capture may generate net economic benefits.

8.4.1.2 Energy Efficiency

The potential for emissions reductions from efficiency 

improvements is strongly linked with both process change 

and fuel switching. For example, moving to Cermet-based 

processes in electric arc furnaces in steel and aluminum 

smelting industries can significantly improve efficiencies 

and lower both combustion and process GHG emissions.

A “bottom up” technical analyses tends to show higher 

potentials and lower costs than when one uses a hybrid or a 

“top-down” approach to assess reduction potentials due to 

efficiency improvements; Table 8.3 portrays the outcome 

of the more conservative hybrid (mix of top-down and bottom-up) approach and provides what some may consider 

conservative estimates of reduction potential (see particularly Martin et al., 2001; Jaccard et al., 2002; Jaccard et al., 

2003a; Jaccard et al., 2003b; and Worrell et al., 2004).

Sector

Reduction of 

fugitives

Energy 

efficiency Process change Fuel substitution

Carbon Capture 

and Storage

Cost 

category %Qred

Cost 

categorya %Qreda Cost category %Qred

Cost 

category %Qred

Cost 

categorya %Qreda

All industry B 3 A/B 12/8 B 20 A 10 C 30

P&P B 5 A/B 10/5 B 40 A 40 D ?

Nonmetal min A 10 A 40 A 40 C 80

Metal smelt A/B 15/20 B 10 A 15 C 40

Mining A 5

Chemicals B 10 A/B 10/5 B 25 A 5 C/D 40/20

Forest products B 5 A 5

Other man A 15 A 20 A 5 D ?

Waste A 90 D 30

a If two letters appear, two percent quantities reduced are shown. Each shows the quantity reduced at that cost. That is, if all lesser and 

higher costs were made, emissions reduction would be the sum of the two values.

Note: The reductions across categories are NOT additive. For example, if “Carbon Capture and Storage” is employed, then fuel 

switching would have little bearing on the emissions reduction possible. Also, it is difficult to isolate process switching and efficiency 

improvements.

The “Cost Categories” are as follows:

CO2-Based: A: $0–$25/t CO2; B: $25–$50/t CO2; C: $50–$100/t CO2; D: >$100/t CO2

Carbon-Based: A: $0–$92/t C; B: $92–$180/t C; C: $180–$367/t C; D: >$367/t C

Table 8.3 Approximate costs and reductions potential.
The U.S. Climate Change Science Program Chapter 8

94 

8.4.1.3 Process Change

Reductions from process change requires not only an understanding of the industry and its potential for change but 

also an understanding of the market demand for industry 

products that may change over time. In pulp production, 

for example, one could move from higher quality kraft 

pulp to mechanical pulp and increase production ratios (the 

kraft process only converts one-half the input wood into 

pulp), but will market acceptability for the end product be 

unaffected? Numerous substitution possibilities exist in 

the rather diverse Other Manufacturing industries (carpet 

recycling, alternative uses for plastics, etc.).

8.4.1.4 Fuel Substitution

It is difficult to isolate fuel substitution and efficiency improvement because fuels display inherent qualities that affect 

efficiency. Fuel substitution can reduce carbon flow but efficiency may become worse. In wood products industries, 

shifts to biomass reduces emissions but increases energy 

use. In terms of higher heating values, shifts from coal or 

oil to natural gas may worsen efficiencies while reducing 

emissions21.

8.4.1.5 Carbon Capture and Storage (CC&S)

In one sense, all industries and landfills could reduce 

emissions through CC&S but the range of appropriate 

technologies has not been fully defined and/or the costs are 

very high. For example, one could combust fuels in a pure 

oxygen environment such that the exhaust steam is CO2-

rich and suitable for capture and storage. Even so, some 

industries, like cement production, are reasonable candidates 

for capture, but cost of transport of the CO2 to storage may 

prohibit implementation (see particularly Herzog, 1999; 

DOE, 2006).

8.5 RESEARCH AND DEVELOPMENT 

NEEDS

If we assume that carbon management will play a significant 

role in the future and that fossil fuels are likely to remain an 

economical energy supply for industries, research and development (R&D) will focus on the control of carbon emissions 

related to the extraction of this energy. Typical combustion 

technologies extract and transform fossil fuels’ chemical 

energy relatively efficiently but, outside of further improvements in efficiency, they generally do little to manage the 

emissions generated. More recently, advanced technologies 

remove particularly onerous airborne emissions, such as 

compounds of sulphur and nitrogen, particulates, volatile 

21 As the ratio of hydrogen to carbon rises in a fossil fuel, more of 

the total heat released upon combustion is caught up in the latent heat 

of vaporization of water and is typically lost to process. This loss is 

equivalent to the difference between a fuel’s higher heating value and 

its lower heating value.

organic compounds, and other criteria air contaminants. 

However, emissions of CO2 remain relatively unaltered. In 

the light of changing views on the impacts of CO2 released 

to the atmosphere, R&D will likely focus on the extraction 

of the energy while preventing CO2 release. Fossil fuels 

might well remain economically competitive and socially 

desirable as a source of energy in some circumstances, 

even when one includes the extra cost of capturing the CO2

and preventing its atmospheric release when converting 

these fuels into non-carbon secondary forms of energy like 

electricity, hydrogen, or heat. 

Some carbon capture and storage processes currently exist; indeed, oil companies have long “sequestered” CO2 to 

enhance oil recovery from underground wells simply by 

injecting it into the oil reservoir. Many newer processes to 

accomplish CO2 capture are being investigated, primarily 

in two categories: pre-combustion and post-combustion 

processes. Pre-combustion alternatives include gasification 

processes where, for example, coal’s energy is entrapped in 

hydrogen and the CO2 stream is subsequently sequestered. 

Post-combustion alternatives include carbon combustion 

in pure oxygen atmospheres and then trapping the resultant 

CO2 for sequestration, and flue stack devices designed to 

extract the CO2 from the flue gases for delivery to sequestration systems. Research has also been conducted on devices 

that can extract CO2 directly from the atmosphere (Keith 

et al., 2003).
The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

Buildings

CHAPTER

9

95

Lead Author: James E. McMahon, LBNL

Contributing Authors: Michael A. McNeil, LBNL, Itha Sánchez 

Ramos, Instituto de Investigaciones Eléctricas, Mexico

KEY FINDINGS

The buildings sector of North America was responsible for annual carbon dioxide emissions of 671 million tons of 

carbon in 2003, which is 37% of total North American carbon dioxide emissions and 10% of global emissions. United 

States buildings alone are responsible for more carbon dioxide emissions than total carbon dioxide emissions of any 

other country in the world, except China.

Carbon dioxide emissions from energy use in buildings in the United States and Canada increased by 30% from 1990 

to 2003, an annual growth rate of 2.1% per year.

Carbon dioxide emissions from buildings have grown with energy consumption, which in turn is increasing with 

population and income. Rising incomes have led to larger residential buildings and increased household appliance 

ownership.

These trends are likely to continue in the future, with increased energy efficiency of building materials and equipment 

and slowing population growth, especially in Mexico, only partially offsetting the general growth in population and 

income.

Options for reducing the carbon dioxide emissions of new and existing buildings include increasing the efficiency of 

equipment and implementing insulation and passive design measures to provide thermal comfort and lighting with 

reduced energy. Current best practices can reduce emissions from buildings by at least 60% for offices and 70% for 

homes. Technology options could be supported by a portfolio of policy options that take advantage of cooperative 

activities, avoid unduly burdening certain sectors, and are cost effective.

Because reducing carbon dioxide emissions 

from buildings is currently secondary to 

reducing building costs, continued improvement of energy efficiency in buildings and 

reduced carbon dioxide emissions from 

the building sector will require a better 

understanding of the total societal cost of 

carbon dioxide emissions as an externality 

of building costs, including the costs of mitigation compared to the costs of continued 

emissions.

•

•

•

•

•

•
The U.S. Climate Change Science Program Chapter 9

96 

9.1 BACKGROUND

In 2003, buildings were responsible for 615 million metric 

tons of carbon (Mt C)1 emitted in the United States (DOE/

EIA, 2005), 40 Mt Cin Canada (Natural Resources Canada, 

2005a), and 17 Mt Cin Mexico (SENER México, 2005), for 

a total of 671 Mt C in North America2 †. According to the 

International Energy Agency, total energy-related emissions in North America in this year were 1815 Mt C (IEA, 

2005). Therefore, buildings were responsible for 37% of 

energy-related emissions 

in North America. North 

American buildings accounted for 10% of global 

energy emissions, which 

totaled 6814 Mt C. United 

States’ buildings alone are responsible for more carbon dioxide (CO2) emissions than total CO2 emissions of any other 

country in the world, except China (Kinzey et al., 2002). 

Significant carbon emissions are due to energy consumption 

during the operation of the buildings; other emissions, not 

well quantified, may occur from water use in and around 

the buildings and from land-use impacts related to buildings. Buildings are responsible for 72% of United States 

electricity consumption and 54% of natural gas consumption 

(DOE/EERE, 2005)3. The discussions in this chapter include 

an accounting of CO2 emissions from electricity consumed 

in the buildings sector; however, this represents a potential 

double counting of the CO2 emissions from fossil fuels that 

are used to generate that electricity (Chapter 6, this report). 

This chapter provides a description of how energy, including 

electrical energy, is used within the buildings sector. Following the discussion of such end uses of energy, this chapter 

then describes the opportunities and potential for reducing 

energy consumption within the sector.

Many options are available for reducing the carbon impacts of new and existing buildings, including increasing 

equipment efficiency and implementing alternative design, 

construction, and operational measures to provide thermal 

comfort and lighting with reduced energy. Current best practices can reduce carbon 

emissions for buildings 

by at least 60% for offices4

 and up to 70% for 

homes5. Residential and 

commercial buildings 

in the United States and 

1 Carbon dioxide emissions only.

2† A dagger symbol indicates that the magnitude and/or range of 

uncertainty for the given numerical value(s) is not provided in the 

references cited.

3

 See Tables 1.1.6 and 1.1.7 in DOE/EERE (2005).

4

 Leadership in Energy and Environment Design (LEED) Gold 

Certification (USGBC, 2005). 

5

 U.S. DOE Building America Program (DOE/EERE, 2006). 

Canada occupy 27 billion m2 (2.7 million hectares)† of floor 

space, providing a large area available for siting non-carbonemitting on-site energy supplies (e.g., photovoltaic panels on 

roofs)6. With the most cutting-edge technology, at the least, 

emissions can be dramatically reduced, and at best, buildings 

can produce electricity without carbon emissions by means 

of on-site renewable electricity generation.

9.2 CARBON FLUXES

Carbon fluxes from energy emissions in buildings are well 

understood, since primary energy inputs from the source 

of production are tracked, their emissions rates are known, 

and the total end user consumption data are gathered and 

reported by energy utilities, typically monthly. The quantity 

of energy consumed by each particular end use is slightly 

less well known because attribution requires detailed data 

on use patterns in a wide variety of contexts. The governments of North America have invested in detailed energy 

consumption surveys, which allow researchers to identify 

opportunities for reducing energy use.

The largest contribution to carbon emissions from buildings is through the operation of energy-using equipment. 

The energy consumed in the average home accounts for 

2.9 metric tons7

 of carbon per year in the United States, 

1.7 metric tons8 per year in Canada, and 0.6 metric tons9

in Mexico (DOE/EIA, 2005; Natural Resources Canada, 

2005b; SENER México, 2004)†. Energy consumption in a 

500 m2 commercial, government, or public-use building in 

the United States produces 1.9 metric tons of carbon (DOE/

EIA, 2005)10 †. Energy consumption includes electricity as 

6

 A recent study estimates a potential of 711 GW generation capacity 

from rooftop installation of photovoltaic systems (Chaudhari et al., 

2004). 

7

 United States’ residential sector emissions of 334 Mt C divided by 

114 million households in 2004; the numerical value given for “tons 

of carbon” is for carbon dioxide emissions only.

8

 Canada residential sector emissions of 20.6 Mt C divided by 12.2 

million households in 2003.

9

 Mexico residential sector emissions of 13.2 Mt C divided by 23.8 

million households in 2004.

10 United States’ commercial sector emissions per m2

 in 2003 times 

500 m2

.

North American buildings 

accounted for 10% of global 

energy emissions, 2003.

Current best practices can 

reduce carbon emissions for 

buildings by at least 60% for 

offices and up to 70% for homes.
97

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

well as the direct combustion of fossil 

fuels (natural gas, bottled gas, and 

petroleum distillates) and the burning 

of wood. Because most electricity in 

North America is produced from fossil 

fuels, each kilowatt-hour consumed 

in a building contributed about 180 g 

of carbon to the atmosphere in 2003 

(DOE/EIA, 2005)11. The equivalent 

amount of energy from natural gas or 

other fuels contributed about 52 g of 

carbon (DOE/EIA, 2005)12. Renewable energy accounted for 9% of electricity production in 2003, down from 

12% in 1990. Renewable site energy 

use in buildings also decreased in that 

time, from 4% to 2%, mostly due to 

decreasing use of wood as a household 

fuel (DOE/EERE, 2005)13.

Buildings-sector CO2 emissions and the relative contribution of each end use are shown in Figure 9.1. In the United 

States, five end uses account for 87% of primary energy 

consumption in buildings: space conditioning (including 

space heating, cooling, and ventilation), 40.9%; lighting, 

19.8%; water heating, 10.5%; refrigeration, 7.9%; and 

electronics (including televisions, computers, and office 

equipment), 7.7% (DOE/EERE, 2005)14 †. Space heating and 

cooling are the largest single uses for residences, commercial, and public-sector buildings, accounting for 46% and 

35% of primary energy, respectively, in the United States 

(DOE/EERE, 2005)15. Water heating is the second-highest 

energy consumer in the United States and Canada in terms 

of site energy, while lighting is the second-highest source 

of CO2 emissions, due to the higher emissions per unit of 

electricity compared to natural gas.

Heating and cooling loads are highly climate dependent; 

colder regions use heating during much of the year (primarily with natural gas), while warm regions seldom use 

heating. The majority of United States households own an 

air conditioner; and although air-conditioner ownership has 

been historically low in Mexico16, sales of this equipment 

are now growing significantly, 14% per year over the past 

10 years17. Space-conditioning energy end use depends 

11 United States’ emissions from electricity divided by delivered 

energy.

12 United States’emissions from natural gas and other fuels divided 

by delivered energy.

13 See Table 1.1.2 and Summary Table 2 in DOE/EERE (2005). 14 Does not include the adjustment EIA uses to relieve differences 

between data sources.

15 Table 1.2.3 and Table 1.3.3 in DOE/EERE (2005); available at 

http://buildingsdatabook.eere.energy.gov (2003 data).

16 Air conditioners have typically been used only in the northern and 

coastal areas of Mexico.

17 Air conditioner sales 1995–2004 from Asociacion Nacional de 

significantly on building construction (e.g., insulation, air 

infiltration) and operation (thermostat settings). Water heating is a major consumer of energy in the United States and 

Canada, where storage-tank systems are common.

Aside from heating and cooling, lighting, and water heating, energy is consumed by a variety of appliances, mostly 

electrical. Most homes in the United States and Canada own 

all of the major appliances, including refrigerators, freezers, 

clothes washers, clothes dryers, dishwashers, and at least 

one color television. The remainder of household energy 

consumption comes from small appliances (blenders and 

microwaves, for example) and increasingly from electronic 

devices such as entertainment equipment and personal computers. In Mexico, 96.6% of households used electricity 

in 2005, and recent years have shown a marked growth in 

appliance ownership: ownership rates in 2000 were 85.9% 

for televisions, 68.5% for refrigerators, 52% for washing 

machines, and only 9.3% for computers. By the end of 2005 

ownership rates had grown to 91% for televisions, 79% for 

refrigerators, 62.7% for washing machines, and 19.6% for 

computers (INEGI, 2005).

Many end uses—such as water heating and space heating, 

cooling, and ventilation—occur in most commercial sector 

buildings. Factors such as climate and building construction 

influence the carbon emissions by these buildings. In addition, commercial buildings contain specialized equipment, 

such as large-scale refrigeration units in supermarkets, 

cooking equipment in food preparation businesses, and 

computers, printers, and copiers in office buildings. Office equipment is the largest component of electricity use 

Fabricantes de Aparatos Domesticos, A.C. (ANFAD).

Figure 9.1 United States’ carbon emissions by sector and (for commercial and residential buildings) by end use.
The U.S. Climate Change Science Program Chapter 9

98 

aside from cooling and lighting. 

Due to heat from internal loads, 

many commercial buildings use 

air-conditioning year round in most 

climates in North America.

Residential and commercial buildings in the United States are responsible for 37% of CO2 emissions 

from energy nationally and 34% 

of emissions from energy in North 

America as a whole. Total emissions from buildings in the United 

States are ten times as high as in 

the other two countries combined, 

due to a large population compared 

to Canada, and high per capita consumption compared to Mexico. On 

a per capita basis, building energy 

consumption in the United States 

(65 Gigajoules [GJ] per person per 

year) is comparable with that of Canada (75 GJ per person 

per year).† This is about seven to eight times higher than in 

Mexico, where 9 GJ is consumed per person per year18 †.

In general, contributions from the residential sector are 

roughly equal to that of the commercial sector, except in 

Mexico, where the commercial sector contributes less. 

Electricity contributes more emissions than all other fuels 

combined in the United States and Mexico (2.6 and 1.8 

times as much, respectively). In Canada, natural gas is on 

par with electricity (0.85 times as many emissions) due to 

high heating loads resulting 

from the cold climate. Fuel oil 

represents most of Canada’s 

“other fuels” for the commercial sector. Firewood (leña) 

remains an important fuel for 

many Mexican households for 

heating, water heating, and cooking. Table 9.1 summarizes 

CO2 emissions by country, sector, and fuel type.

The energy consumed during building operation is the 

most important input to the carbon cycle from buildings; 

but it is not the only one. The construction, renovation, and 

demolition of buildings also generate a significant flux of 

wood and other materials. Construction of a typical 204 

m2 (2200 ft2) house requires about 20 metric tons of wood 

and creates 2 to 7 metric tons of construction waste (DOE/

18 Total building energy in 1999 (Source: IEA) divided by population 

(Source: UN Department of Economic and Social Affairs) United 

States, 18296 million GJ divided 282 million; Canada 2280 million 

GJ divided by 30.5 million; Mexico 855 million GJ divided by 97.4 

million. 

EERE, 2005) 19 †. Building lifetimes are many decades and, 

especially for commercial buildings, may include several 

cycles of remodeling and renovation. In the United States 

as a whole, water supplied to residential and commercial 

customers accounts for about 6% of total national fresh 

water consumption. This water consumption also impacts 

the carbon cycle because water supply, treatment, and waste 

disposal require energy.

9.3 TRENDS AND DRIVERS

Several factors influence trends in carbon emissions in the 

buildings sector. Some driver variables tend to increase 

emissions, while others decrease emissions. Emissions from 

energy use in buildings in the United States and Canada increased 30% from 1990 to 2003 (DOE/EERE, 2005; Natural 

Resources Canada, 2005a) 20, corresponding to an annual 

growth rate of 2.1%.

Carbon emissions from buildings have grown with energy 

consumption, which in turn is increasing with population 

and income. Demographic shifts therefore have a direct influence on residential energy consumption. Rising incomes 

have led to larger residential buildings and the amount of 

living area per capita is increasing in all three countries in 

North America. On one hand, total population growth is 

slowing, especially in Mexico, as families are having fewer 

children than in the past. Annual population growth during 

the 1990s was 1.1% in the United States, 1.0% in Canada, 

19 Construction data from Table 2.1.7 in DOE/EERE (2005); wood 

content estimated from lumber content. Construction waste from Table 

3.4.1 in DOE/EERE (2005).

20 Data from Table 3.1.1 in DOE/EERE (2005).

Emissions from energy use 

in buildings in the United 

States and Canada increased 

30% from 1990 to 2003.

a Mexican commercial building emissions include electricity statistics provided by the 

National Energy Balance (SENER, 2004). Recent investigations suggest that these may be 

significantly underestimated, since the methodology used categorizes most large commercial 

and public sector buildings in the category “medium industry” (Odón de Buen Rodríguez, 

President, Energía Technología y Educación SC, Puente de Xoco, Mexico, personal 

communication to James McMahon, Lawrence Berkeley National Laboratory, Berkeley, 

California, November 23, 2006).

Table 9.1 Carbon dioxide emissions from energy consumed in buildings.

2003 Carbon Dioxide Emissions (Mt C)

Electricity Natural Gas Other Fuels All Fuels

United States 44 5.8 122.1 46.5 614.5

Residential 229.2 75.6 29.3 334.1

Commercial 216.6 46.5 17.2 280.4

Canada 17.7 15.8 6.1 39.5

Residential 9.4 8.7 2.5 20.6

Commercial 8.2 7.1 3.5 18.9

Mexico 10.7 0.5 5.6 16.9

Residential 7.3 0.4 5.5 13.2

Commercial a 3.5 0.1 0.1 3.7
99

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

and 1.7% in Mexico. In the period from 1970 to 1990, it 

was 1.0%, 1.2%, and 2.5%, respectively21 †. By 2005, annual population growth in Mexico declined to 1% (INEGI, 

2005). On the other hand, a shift from large, extendedfamily households to nuclear-family and single-occupant 

households means an increase in the number of households 

per unit population22, each with its own heating and cooling 

systems and appliances.

The consumption of energy on a per capita basis or per 

unit economic activity (gross domestic product [GDP]) is 

also not constant but depends on several underlying factors. 

Economic development is a primary driver of overall per 

capita energy consumption and influences the mix of fuels 

used23. Per capita energy consumption generally grows 

with economic development, since wealthier people live in 

larger dwellings and use more energy24. Recently, computers, printers, and other office equipment have become commonplace in nearly all 

businesses and in most 

homes. These end uses 

now constitute 7% of 

primary household energy consumption. Because of these growing 

electricity uses, the ratio of electricity to total 

household primary energy has increased. This 

is significant to emissions because of the large 

21 Source: U.N. Department of Economic and Social Affairs. 22 See household size statistics in Table 9.2. 23 For example, whether biomass, natural gas, or electricity is used 

for space heating and cooking.

24 See Table 4.2.6 in DOE/EERE (2005).

emissions associated with the combustion of fossil fuels in 

power plants. Electricity can be generated from renewable 

sources such as solar or wind, but their full potential has 

yet to be realized.

In the United States, the major drivers of energy consumption growth are growth in commercial floor space and an 

increase in the size of the average home. The size of an average United States single-family home has grown from 160 

m2 (1720 ft2) for a house built in 1980 to 216 m2 (2330 ft2) 

in 2003†. In the same 

time, commercial floor 

space per capita has 

increased from 20 to 

22.6 m2 (215 to 240 ft2) 

(DOE/EERE, 2005)25 †. 

Certain end uses once 

considered luxuries have now become commonplace. Only 

56% of United States’ homes in 1978 used mechanical spacecooling equipment (DOE/EIA, 2005). By 2001, ownership 

grew to 83% driven by near total saturation in warmer 

climates and a demographic shift in new construction to 

these regions. Table 9.2 shows emissions trends as well as 

the underlying drivers.

 

Although the general trend has been toward growth in per 

capita emissions, emissions per unit of GDP have decreased 

in past decades due to improvements in efficiency. Efficiency performance of most types of equipment has generally increased, as has the thermal insulation of buildings, 

due to influences such as technology improvements and 

voluntary and mandatory efficiency standards and building codes. The energy crisis of the 1970s was followed by 

25 See Tables 2.1.6 and 2.2.1 in DOE/EERE (2005). Residential data 

are from 1981. 

In the United States, the major 

drivers of energy consumption 

growth are growth in commercial 

floor space and an increase in 

the size of the average home.

Table 9.2 Principal drivers of buildings emissions trends.

Driver

United States Canada Mexico

Total 2000

Growth 

Rate 1990-

2000

Total 2000

Growth 

Rate 1990-

2000

Total 2000

Growth 

Rate 1990-

2000

Population (millions) 288 1.1% 31.0 1.0% 100 1.7%

Household Size (persons per household) 2.5 -0.6% 2.6 -0.9% 5.3 -0.1%

Per capita GDP (thousand $US 1995) 31.7 2.0% 23.0 1.8% 3.8 1.8%

Residential Floor space (billion m2

) 15.7 2.4% 1.5 2.4% 0.85 N/A

Commercial Floor space (million m2

) 6.4 0.6% 0.5 1.6% N/A N/A

Building Energy Emissions per GDP (g C/$US) 70 -0.5% 59 -0.9% N/A N/A

Source: Population - United Nations Department of Economic and Social Affairs (UNDESA); Household Size - United Nations Development 

Programme (UNDP); gross domestic product (GDP) - World Bank

Source: Floor space - EIA-EERE (2005), U.S. residential floor space estimated from 2001 Residential Energy Consumption Survey (DOEEIA), Natural Resources Canada (2005a). Mexican residential floor space estimated from Table 1.8 in CONAFOVI (2001)

Source: Emissions - EIA-EERE (2005), Natural Resources Canada (2005b)
The U.S. Climate Change Science Program Chapter 9

100 

a sharp decline in economic energy intensity. Increases in 

efficiency were driven both by market-related technology 

improvements and incentives and by the establishment of 

federal and state/provincial government policies designed 

to encourage or require energy efficiency.

9.4 OPTIONS FOR MANAGEMENT

A variety of alternatives exists for reducing emissions 

from the buildings sector. Technology- and market-driven 

improvements in efficiency are expected to continue for 

most equipment, but this will probably not be sufficient to 

curtail emissions growth adequately without government 

intervention. The government has many different ways in 

which it can manage emissions that have been proven effective in influencing the flow of products from manufacturers 

to users (Interlaboratory Working Group, 2000). That flow 

may involve six steps: advancing technologies; product 

development and manufacturing; supply, distribution, and 

wholesale purchasing; retail purchasing; system design and 

installation; and operation and maintenance (Wiel and McMahon, 2005). Options for specific products or packages include government investment in research and development, 

information and education programs, energy pricing and 

metering, incentives and 

financing, establishment of 

voluntary guidelines, procurement programs, energy 

audits and retrofits, and 

mandatory regulation. The 

most effective approaches 

will likely include more 

than one of these options in 

a policy portfolio that takes 

advantage of synergies, 

avoids unduly burdening 

certain sectors, and is cost 

effective. Major participants include not only federal agencies, but also state 

and local governments, 

energy and water utilities, 

private research and development firms, equipment 

manufacturers and importers, energy services companies (ESCOs), nonprofit 

organizations, and building 

owners and occupants. An 

ESCO is a company that 

offers to reduce a client’s 

utility costs, often with the 

cost savings being split with 

the client through an energy 

performance contract or a shared savings agreement.

Technology adoption supported by research and 

development: Government has the opportunity to 

encourage development and adoption of energy-efficient technologies through investment in research 

and development, which can advance technologies and 

bring down prices, therefore enabling a larger market. 

Successful programs have contributed to the development of high-efficiency lighting, heating, cooling, and 

refrigeration. Research and development has also had an 

impact on the improvement of insulation, ducting, and 

windows. Finally, government support of research and 

development has been critical in the reduction of costs 

associated with development of renewable energy.

Voluntary Programs: By now, there are a wide range 

of efficiency technologies and best practices available 

and if the most cost-effective among them were widely 

utilized, carbon emissions would be reduced. Voluntary 

measures can be effective in overcoming some market 

barriers. Government has been active with programs to 

educate consumers with endorsement labels or ratings 

(such as the U.S. Environmental Protection Agency’s 

[EPA’s] and U.S. Department of Energy’s [DOE’s] En-

•

•

Source: California Energy Commission— Available at 

http://www.energy.ca.gov/2005publications/CEC-999-2005-007/CEC-999-2005-007.PDF, 

Slide 5

BOX 9.1: Electricity Consumption in 

the United States and in California

Since the mid-1970s, the state of California has pursued an aggressive set of efficiency 

regulations and utility programs. As a result, per capita electricity consumption has 

stabilized in that state, while it continues to grow in the United States as a whole.
101

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

ergy Star Appliances and Homes) and public-private 

partnerships (such as DOE’s “Building America Program”). Government is not the only player, however. 

Energy utilities can offer rebates for efficient appliances and ESCOs can facilitate best practices at the 

firm level. Finally, nongovernmental organizations and 

professional societies (such as the U.S. Green Building 

Council and the American Institute of Architects) can 

play a role in establishing benchmarks and ratings.

Regulations: Governments can dramatically impact 

energy consumption through well-considered regulations that address market failures with cost-effective 

measures. Regulations facilitate best practices in two 

ways: they eliminate the lowest-performing equipment 

from the market, and they boost the market share of 

high-efficiency technologies. Widely used examples are 

mandatory energy efficiency standards for appliances, 

equipment, and lighting, mandatory labeling programs, 

and building codes. Most equipment standards are instituted at a national level, whereas most states have their 

own set of prescriptive building codes (and sometimes 

energy performance standards for equipment) to guarantee a minimum standard for 

energy-saving design in homes 

and businesses.

Although large strides in efficiency 

improvement have been made over 

the past three decades, significant 

improvements are still possible. They 

will involve continued improvement 

in equipment technology and will 

increasingly take a whole-building 

approach that integrates the design 

of the building and the energy consumption of the equipment inside it. 

The improvements may also involve 

alternative ways to provide energy 

services, such as cogeneration of heat 

and electricity and thermal energy 

storage units (Public Technology Inc. 

and U.S. Green Building Council, 

1996).

Whole-building certification standards evaluate a package of efficiency 

and design options. An example is the 

Leadership in Energy and Environmental Design (LEED) certification 

system developed by the U.S. Green 

Building Council, a non-profit organization. In existence for five years, 

the LEED program has certified 36 

million m2

 (390 million ft2) of com-

•

mercial and public-sector buildings and has recently implemented a certification system for homes. The LEED program 

includes a graduated rating system (Certified, Silver, Gold, 

or Platinum) for environmentally friendly design, of which 

energy efficiency is a key component (USGBC, 2005).

On the government side, the EPA’s Energy Star Homes 

program awards certification to new homes that are independently verified to be at least 30% more energy-efficient 

than homes built to the 1993 national Model Energy Code, 

or 15% more efficient than state energy code, whichever 

is more rigorous. Likewise, the DOE’s Building America 

program partners with homebuilders, providing research 

and development toward goals to decrease primary energy 

consumption by 30% for participating projects by 2007, and 

by 50% by 2015.

BOX 9.2: Impact of Efficiency Improvements

Source: California Energy Commission—Available at 

http://www.energy.ca.gov/2005publications/CEC-999-2005-007/CEC-999-

2005-007.PDF, Slide 7

Between 1974 and 2001, the energy consumption of the average refrigerator sold in the United States dropped by 74%, a change driven by 

market forces and regulations. From 1987 to 2005, the U.S. Congress 

and DOE promulgated labels or minimum efficiency standards for over 

40 residential and commercial product types. Canada and Mexico also 

have many product labels and efficiency standards, and a program is 

under way to harmonize standards throughout North America in connection with the North American Free Trade Agreement (NAFTA).
The U.S. Climate Change Science Program Chapter 9

102 

9.5 RESEARCH AND 

DEVELOPMENT NEEDS

Research, development, demonstration, and 

deployment of technologies and programs to 

improve energy efficiency in buildings and to 

produce energy with fewer carbon emissions 

have involved significant effort over the last 

30 years. These efforts have contributed options toward carbon management. Technologies 

and markets continue to evolve, representing 

new crops of “low-hanging fruit” available for 

harvesting. However, in most buildings-related 

decisions in North America, reducing carbon 

emissions remains a secondary objective to other goals, 

such as reducing first costs (DeCanio, 1993 and 1994). The 

questions for which answers could significantly change the 

discussion about options for carbon management include 

the following:

What is the total societal cost of environmental externalities26, including carbon emissions? Energy resources 

in North America have been abundant and affordable, 

but external costs have not been completely accounted 

for. Most economic decisions are weighted toward the 

short term and do not consider the complete costs. Total 

societal costs of carbon emissions are unknown and 

because it is a global issue, difficult to allocate. Practical 

difficulties notwithstanding, this is a key issue, answers 

to which could influence priorities for research and 

development as well as policies such as energy pricing, 

carbon taxes, or credits.

What cost-effective reduced-carbon-emitting equipment and building systems—including energy demand 

(efficient equipment) and supply (renewable energy)—

are available in the short, medium, and long term? 

Policymakers must have sufficient information to be 

confident that particular new technology types or programs will be effective and affordable. For consumers to 

consider a set of options seriously, the technologies must 

be manifested as products that are widely available and 

competitive in the marketplace. Therefore, economic 

and market analyses are necessary before attractive 

options for managing carbon can be proposed.

How do the costs of mitigation compare to the costs of 

continued emissions? The answers to the previous two 

questions can be compared in order to develop a supply curve of conserved carbon comprising a series of 

least-cost options, whether changes to energy demand 

or to supply, for managing carbon emissions. The sup26 External costs are the costs borne by society beyond those included 

in the market prices of goods. For example, carbon emissions may 

cause environmental damage not reflected in the market transactions 

associated with the buying and selling of energy (Rabl and Spadaro, 

2007). 

•

•

•

ply curve of conserved carbon will need to be updated 

at regular intervals to account for changes in technologies, production practices, and market acceptance of 

competing solutions.
The Carbon Cycle in Land and Water Systems

Lead Author: R.A. Houghton, Woods Hole Research Center

PART III OVERVIEW

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

103

The six chapters (Chapters 10-15) in Part III consider 

the current and future carbon balance of terrestrial 

and aquatic ecosystems in North America. Although 

the amount of carbon exchanged between these ecosystems and the atmosphere each year through photosynthesis and plant and microbial respiration is large, 

the net balance for all of the ecosystems combined is 

currently a net sink of 370-505 million tons of carbon 

(Mt C) per year1. This net sink offsets only about 20-

30% of current fossil-fuel emissions from the region 

(1856 Mt C per year in 2003) (Chapter 3 this report). 

The cause of this terrestrial carbon sink is uncertain. 

Although management has the potential for removing 

carbon from the atmosphere and storing it in vegetation and soil, most of the current sink is not the result 

of current management practices. Instead, most of it 

may be attributed to a combination of past management and the response of terrestrial ecosystems to 

environmental changes.

The large sink in the forests of Canada and the 

United States, for example, is, in some measure, the 

consequence of continued forest growth following 

agricultural abandonment that occurred in the past. 

This is partly the result of past and current management practices (e.g., fire suppression), and partly the 

result of forest responses to a changing environment 

(climatic change, carbon dioxide [CO2] 

fertilization, and the 

increased mobilization of nutrients). 

The relative importance of these broad 

factors in accounting 

for the current sink is 

unknown. Estimates 

vary from attributing 

nearly 100% of the 

sink in United States 

forests to regrowth 

(Caspersen et al., 

1

 The lower estimate is from this overview, the larger estimate 

from Chapter 3, with most of the difference attributable to 

uncertainty in the sink from woody encroachment. See Table 

III.1, footnote h, for discussion of this range.

2000; Hurtt et al., 2002) to attributing nearly all of it 

to CO2 fertilization (Schimel et al., 2000). The attribution question is critical because the current sink may 

be expected to increase in the future if the important 

mechanism is CO2 fertilization, for example, but may 

be expected to decline if the important mechanism 

is forest regrowth (forests accumulate carbon more 

slowly as they age). Understanding the history of land 

use, management, and disturbance is critical because 

disturbance and recovery are major determinants of 

the net terrestrial carbon flux.

Land-use change 

and management 

have been, and 

will be, important in the carbon 

balance of other 

ecosystems besides forests. The 

expansion of cultivated lands in 

Canada and the United States in the 1800s released 

large amounts of carbon to the atmosphere (Houghton 

et al., 1999), leaving those lands with the potential 

for recovery (i.e., a future carbon sink), if managed 

properly. For example, recent changes in farming 

practice may have begun to recover the carbon that 

was lost decades ago. Recovery of carbon in soil, 

however, generally takes longer than its loss through 

cultivation. Grazing lands, although not directly affected by cultivation, have, nevertheless, been managed in the United States through fire suppression. 

The combined effects of grazing and fire suppression 

are believed to have promoted the invasion of woody 

vegetation, possibly a carbon sink at present. Wetlands 

are also a net carbon sink, but the magnitude of the 

sink was larger in the past than it is today, again, as 

a result of land-use change (draining of wetlands for 

agriculture and forestry). The only lands that seem to 

have escaped management are those lands overlying 

permafrost (perennially frozen ground), and they 

are clearly subject to change in the future as a result 

of global warming. Settled lands, by definition, are 

managed, and are dominated by fossil-fuel emissions. 

Nevertheless, the accumulation of carbon in urban and 

Understanding the history of 

land use, management, and 

disturbance is critical because 

disturbance and recovery are 

major determinants of the 

net terrestrial carbon flux.
The U.S. Climate Change Science Program Part III Overview

104 

suburban trees suggests a net sequestration of carbon in the 

biotic component of long-standing settled lands. Residential 

lands recently cleared from forests, on the other hand, are 

sources of carbon (Wienert and Hamburg, 2006).

From the perspective of carbon and climate, ecosystems are 

important if (1) they are currently large sources or sinks of 

carbon or (2) they have the potential to become large sources 

or sinks of carbon in the future through either management 

or environmental change, where “large” sources or sinks, in 

this context, are determined by the product of area (hectares) 

times flux per unit area (or flux density) (megagrams of 

carbon [Mg C] per hectare per year).

The largest carbon sink in North America (270 Mt C per 

year) is associated with forests (Chapter 11 this report) 

(Table III-1). The sink includes the carbon accumulating in 

wood products (e.g., in increasing numbers of houses and 

landfills) as well as in the forests themselves. A sink is believed to exist in wetlands (Chapter 13 this report), including 

the wetlands overlying permafrost (Chapter 12 this report), 

although the magnitude of this sink is uncertain. More certain is the fact that the current sink is considerably smaller 

than it was before wetlands were drained for agriculture and 

forestry. The other important aspect of wetlands is that they 

hold more than half of the carbon in North America. Thus, 

despite the current net 

sink in these systems, 

their potential for future 

emissions is large.

Although management 

has the potential to increase the carbon sequestered in agricultural (cultivated) lands, these lands today 

are nearly in balance with respect to carbon (Chapter 10 this 

report). The carbon lost to the atmosphere from cultivation 

of organic soils (soils dominated by organic matter) is approximately balanced by the carbon accumulated in mineral 

soils (soils consisting of more inorganic material, such as 

sand or clay). In the past, before cultivation, these soils held 

considerably more carbon than they do today, but 25-30% 

of that carbon was lost soon after the lands were initially 

cultivated. In large areas of grazing lands, there is the possibility that the invasion and spread of woody vegetation 

(woody encroachment) is responsible for a significant net 

carbon sink at present (Chapter 10 this report). The magnitude (and even sign) of this flux is uncertain, however, in part 

because some ecosystems lose carbon below-ground (soils) 

as they accumulate it aboveground (woody vegetation), and 

in part because the invasion and spread of exotic grasses into 

semi-arid lands of the western United States are increasing 

the frequency of fires, reversing woody encroachment, and 

releasing carbon (Bradley et al., 2006).

The emissions of carbon from settled lands are largely 

considered in the chapters in Part II and in Chapter 14 of 

this report. Non-fossil carbon seems to be accumulating in 

trees in these lands, but the net changes in soil carbon are 

uncertain.

The only ecosystems that appear to release carbon to the 

atmosphere at present are the coastal waters. The estimated 

flux of carbon is close to zero (and difficult to determine) 

because the gross fluxes (from river transport, photosynthesis, and respiration) are large and variable in both space 

and time.

The average net fluxes of carbon expressed as Mg C per 

hectare per year in Table III-1 are for comparative purposes. 

They show the relative flux density for different types of 

ecosystems. These annual fluxes of carbon are rarely determined with direct measurements of flux, however, because 

of the extreme variability of fluxes in time and space, even 

within a single ecosystem type. Extrapolating from a few 

isolated measurements to an estimate for the whole region’s 

flux is difficult. Rather, the net changes are more often 

based on differences in measured stocks over intervals of 

10 years, or longer (Chapter 3 this report), or are based on 

the large and rapid changes per hectare that are reasonably 

well documented for certain forms of management, such as 

the changes in carbon stocks that result from the conversion 

of forest to cultivated land. Thus, most of the flux estimates 

in Table III-1 are long-term and large-area estimates.

Nevertheless, average flux density is one factor important 

in determining an ecosystem’s role as a net source or sink 

for carbon. The other important factor is area. Permafrost 

wetlands, for example, are currently a small net sink for 

carbon. They cover a large area, however, hold large stocks 

of carbon, and, thus, have the potential to become a significant net source of carbon if the permafrost thaws with global 

warming (Smith et al., 2001; Smith et al., 2005a; Osterkamp 

and Romanovsky, 1999; Osterkamp et al., 2000). Forests 

clearly dominate the net uptake and storage of carbon in 

North America, although wetlands and settled lands have 

mean flux densities that are above average.

The two factors (flux density and area) demonstrate the 

level of management required to remove a significant 

amount of carbon from the atmosphere and keep it on land. 

Under current conditions, sequestration of 100 Mt C per 

year, for example (about 7% of fossil-fuel emissions from 

North America), requires nearly half the forest area (Table 

III-1). As discussed above, the cause of this sequestration is 

uncertain, but enhancing it through management over a few 

hundred million hectares would require considerable effort. 

Nevertheless, the cost (in $/metric ton CO2) may be low 

relative to other options for managing carbon. For example, 

Wetlands hold more than half of 

the carbon in North America. 

Thus, despite the current net sink 

in these systems, their potential 

for future emissions is large.
105

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

forestry activities are estimated to have the potential to sequester 100-200 Mt C per year in the United States at prices 

ranging from less than $10/ton of CO2 for improved forest 

management, to $15/ton for afforestation, to $30-50/ton for 

production of biofuels (Chapter 11 this report). Somewhat 

smaller sinks of 10-70 Mt C per year might be stored in 

agricultural soils at low to moderate costs ($3-30/ton CO2) 

(Chapter 10 this report). The maximum amounts of carbon 

that might be accumulated in forests and agricultural soils 

are not known, thus, the number of years these rates of sequestration might be expected to continue is also unknown. 

It seems unlikely that the amount of carbon currently held 

in forests and agricultural lands could double. Changes in 

climate will also affect carbon storage, but the net effect of 

management and climate is uncertain.

a. Fossil-fuel inputs to crop management are not included. Some of the carbon sequestration is occurring on grasslands as well as croplands, 

but the inventories do not separate these fluxes. The near-zero flux is for Canada and the United States only. Including Mexican croplands 

would likely change the flux to a net source because croplands are expanding in Mexico, and the carbon in biomass and soil is released to 

the atmosphere as native ecosystems are cultivated.

b. Fossil-fuels are not included. The small net sink results from the Conservation Reserve Program in the United States. Including Mexico is 

likely to change the net sink to a source because forests are being converted to grazing lands. Neither woody encroachment nor woody 

elimination is included in this estimate of flux because the uncertainties are so large.

c. Includes an annual sink of 68 Mt C per year in wood products as well as a sink of 201 Mt C per year in forested ecosystems.

d. Includes zones with continuous, discontinuous, sporadic, and isolated permafrost; that is, not all of the lands are strictly over permafrost. 

e. Urban trees only (does not include soil carbon). Note that this sink is accounted for as part of the forest sink in Chapter 3 (Table 3.1).

f. Sum does not include coastal waters. The summed area is larger than the total area (note i) because of double counting. For example, an 

estimated 75 × 106

 hectares (ha) of permafrost lands in Canada are forested (and may be included in forest area as well as permafrost area), 

26 x 106

 ha of wetlands in the United States are forested, and 54 x 106 ha of wetlands are shrublands. In addition, an estimated 75 x 106 ha 

of other wooded lands are included as both forests and rangelands, and ~70 x 106

 ha of grasslands and shrublands are counted also as nonpermafrost lands within areas defined as sporadic or isolated permafrost (see note d).

g. Weighted average; does not include coastal waters.

h. Does not include coastal waters. The total annual sink of 370 Mt C is lower than the estimate of 505 Mt C presented in Chapter 3 (Table 

3.1). The largest difference results from the flux of carbon attributed to woody encroachment. Chapter 3 includes a sink of 120 Mt C per 

year; Table III-1, above, presents a net flux of zero (see note b). Other differences between the two estimates include: (1) an additional 

sink in Table III-1 of 14 Mt C per year in permafrost mineral soils and (2) a sink of 25 Mt C per year in rivers and reservoirs that is included in Table 3.1 but not in Table III-1. In addition, there are small differences in the estimates for agricultural lands and grasslands. 

i. Areas (106

 ha) (The Times Atlas of the World, 1990) 

Globe North America Canada United States Mexico 

14,900 2,126 992 936 197 j. Total carbon stocks are reduced by the areas double counted (see note f).

Type of ecosystem

Area

(106 ha)

Current mean

flux density

(Mg C per ha

per year)

Current

flux

(Mt C per year)

Carbon

stocks

(Mt C)

Mean

carbon stocks

(Mt C per ha)

Agriculture 231 0.0 0±15a 18,500 80

Grass, shrub and arid 558 –0.01 –6b 59,950 107

Forests 771 –0.35 –269c 171,500 222

Permafrost lands

 Peatlands 51 –0.13 –6.7 57,700 1130

 Mineral soilsd 517 –0.03 –14 98,780 191

Non-permafrost wetlands

 Peatlands 86 –0.12 –10 126,400 1470

 Mineral soils 105 –0.21 –22.3 38,100 363

 Estuarine 4.5 –2.3 –10.2 900 200

Settled landse 104 –0.31 –32 ~1,000 10

Coastal waters 384 0.05 19

 Sum 2427f –0.15g –370h 572,830f

 Total 2126i 480,000j 225g

Table III.1 Ecosystems in North America: their areas, net annual fluxes of carbon (negative values are sinks), and 

carbon stocks (including both vegetation and soils).
The U.S. Climate Change Science Program Part III Overview

106 

Despite the limited nature of carbon uptake and storage in 

offsetting the global emissions of carbon from fossil fuels, 

local and regional activities may, nevertheless, offset local 

and regional emissions of fossil carbon. This offset, as well 

as other co-benefits, may be particularly successful in urban 

and suburban systems (Chapter 14 this report).

The effects and cost of managing aquatic systems are less 

clear. Increasing the area of wetlands, for example, would 

presumably increase the sequestration of carbon; but it 

would also increase emissions of methane (CH4), countering 

the effect of carbon storage. Fertilization of coastal waters 

with iron has been proposed as a method for increasing 

oceanic uptake of CO2, but neither the amount of carbon 

that might be sequestered nor the side effects are known 

(Chapter 15 this report).

A few studies have estimated the potential magnitudes of 

future carbon sinks as a result of management (Chapters 10, 

11 this report). However, the contribution of management, 

as opposed to the environment, in today’s sink is unclear 

(Chapter 3 this report), and for the future, the relative roles of 

management and environmental change are even less clear. 

The two drivers might work together to enhance terrestrial 

carbon sinks, as seems to have been the case during recent 

decades (Prentice et al., 2001) (Chapter 2 this report). On the 

other hand, they might work in opposing directions. A worstcase scenario, quite possible, is one in which management 

will become ineffective in the face of large natural sources 

of carbon not previously experienced in the modern world. 

In other words, while management is likely to be essential 

for sequestering carbon, it may not be sufficient to preserve 

the current terrestrial carbon sink over North America, let 

alone to offset fossil-fuel emissions.

At least one other observation about storing carbon in terrestrial and aquatic ecosystems should be mentioned. In 

contrast to the hundreds of millions of hectares that must 

be managed to sequester 100 Mt C annually, a few million 

hectares of forest fires can release an equivalent amount of 

carbon in a single year. This disparity in flux densities underscores the fact that a few million hectares are disturbed 

each year, while hundreds of millions of hectares are recovering from past disturbances. The natural fluxes of carbon 

are large in comparison to net fluxes. The observation is 

relevant for carbon management, because the cumulative 

effects of managing small net sinks to mitigate fossil-fuel 

emissions will have to be understood, analyzed, monitored, 

and evaluated in the context of larger, highly variable, and 

uncertain sources and sinks in the natural cycle.

The major challenge for future research is quantification of 

the mechanisms responsible for current (and future) fluxes 

of carbon. In particular, what are the relative effects of management (including land-use change), environmental change, 

and natural disturbance in determining sources and sinks 

of carbon for today and tomorrow? Will the current natural 

sinks continue, grow in magnitude, or reverse to become net 

sources? What is the role of soils in the current (and future) 

carbon balance (Davidson and Janssens, 2006)? What are 

the most cost-effective means of managing carbon?

Answering these questions will require two scales of measurement: (1) an expanded network of intensive research sites 

dedicated to understanding basic processes (e.g., the effects 

of management and environmental effects on carbon stocks), 

and (2) extensive national-level networks of monitoring sites, 

through which uncertainties in carbon stocks (inventories) 

would be reduced and changes, directly measured. Elements 

of these measurements are underway, but the effort has not 

yet been adequate for resolving these questions.

KEY UNCERTAINTIES AND GAPS IN 

UNDERSTANDING THE CARBON CYCLE 

OF NORTH AMERICA

• As mentioned above, the net flux of carbon resulting from 

woody encroachment and its inverse, woody elimination, 

is highly uncertain. Even the sign of the flux is in question.

• Rivers, lakes, dams, and other inland waters are mentioned in Chapter 15 as being a source of carbon, but they 

are claimed elsewhere to be a sink (Chapter 3 this report). 

The sign of the net carbon flux attributable to erosion, 

transport, deposition, accumulation, and decomposition 

is uncertain (e.g., Stallard, 1998; Lal, 2001; Smith et al., 

2005b).

• Several chapters cite studies that have attempted to 

quantify the potential for management to increase carbon 

sinks in the future, but no studies have yet attempted to 

estimate the potential future sources of carbon for North 

America as they have for the globe (e.g., Friedlingstein et 

al., 2006; Jones et al., 2005). Global models that include 

the feedbacks between climatic change and the carbon 

cycle have all shown decreased carbon sinks over the 

next century. In North America, warming of wetlands 

and thawing of permafrost, in particular, are likely to 

increase emissions of carbon to the atmosphere, CH4

as well as CO2; and periods of unusually low rainfall, 

combined with warming trends, are likely to release 

carbon from the ecosystems of the Mountain West and 

the southwestern United States through increasing their 

vulnerability to wildfires and insect outbreaks (Potter et 

al., 2003 and 2005).
The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

Agricultural and Grazing Lands

CHAPTER

10

107

Lead Authors: Richard T. Conant, Colo. State Univ.; Keith 

Paustian, Colo. State Univ.

Contributing Authors: Felipe García-Oliva, UNAM; H. Henry 

Janzen, Agriculture and Agri-Food Canada; Victor J. Jaramillo, 

UNAM; Donald E. Johnson, Colo. State Univ. (deceased); Suren N. 

Kulshreshtha, Univ. Saskatchewan

KEY FINDINGS

Agricultural and grazing lands (cropland, pasture, rangeland, shrublands, and arid lands) occupy 789 million hectares 

(1.95 billion acres), which is 47% of the land area of North America, and contain 78.5 ± 19.51 billion tons of organic 

carbon (17% of North American terrestrial carbon) in the soil alone.

The emissions and uptake and storage of carbon on agricultural lands are mainly determined by two conditions: management and changes in the environment. The effects of converting forest and grassland to agricultural lands and of 

agricultural management (e.g., cultivation, conservation tillage) are reasonably well known and have been responsible 

for historic losses of carbon in Canada and the United States (and for current losses in Mexico); the effects of climate 

change or of elevated concentrations of atmospheric carbon dioxide are uncertain.

Conservation-oriented management of agricultural lands (e.g., use of conservation tillage, improved cropping and 

grazing systems, reduced bare fallow, set-asides of fragile lands, and restoration of degraded soils) can significantly 

increase soil carbon stocks.

Agricultural and grazing lands in the United States and Canada are currently near neutral with respect to their soil 

carbon balance, but agricultural and grazing lands in Mexico are likely losing carbon due to land-use change. Although 

agricultural soils are estimated to currently uptake about 19-20 million tons of carbon per year, the cultivation of 

organic soils releases approximately 6-12 million tons of carbon per year. On-farm fossil-fuel use (around 31 million 

tons of carbon per year), agricultural liming (1.2 million tons of carbon per year), and manufacture of agricultural 

inputs including fertilizer (approximately 6 million tons of carbon per year) yields a net source from the agricultural 

sector of about 25-30 million tons of carbon per year.

As much as 120 million tons of carbon per year may be accumulating through woody encroachment of arid and 

semi-arid lands of North America; this value is highly uncertain. Woody encroachment is generally accompanied by 

decreased forage production, and ongoing efforts to reestablish forage species are likely to reverse carbon accumulation by vegetation.

Projections of future trends in agricultural land area and soil carbon stocks are unavailable or highly uncertain because 

of uncertainty in future land-use change and agricultural management practice. 

Annualized prices of $15/metric ton carbon dioxide, could yield mitigation amounts of 46 million tons of carbon per 

year captured in agricultural soils and 14.5 million tons of carbon per year from reductions in fossil-fuel use. At lower 

prices of $5/metric ton carbon dioxide, the corresponding values would be 34 million tons of carbon per year and 9 

million tons of carbon per year, respectively. 

Policies designed to suppress emissions of one greenhouse gas need to consider complex interactions to ensure that 

net emissions of total greenhouse gases are reduced. For example, increased use of fertilizer or irrigation may increase 

crop residues and carbon uptake and storage, but may stimulate emissions of methane or nitrous oxide.

1

 The uncertainty in this value is given as one standard error of the mean. 

•

•

•

•

•

•

•

•
The U.S. Climate Change Science Program Chapter 10

108 

Many of the practices that lead to carbon capture and storage or to reduced carbon dioxide 

and methane emissions from agricultural lands 

not only increase production efficiencies, but 

lead to environmental co-benefits, for example, 

improved soil fertility, reduced erosion, and 

pesticide immobilization.

An expanded network of intensive research 

sites would allow us to better understand the 

effects of management on carbon cycling and 

storage in agricultural systems. An extensive 

national-level network of soil monitoring sites 

in which changes in carbon stocks are directly 

measured would allow us to reduce the uncertainty in the inventory of agricultural and 

grazing land carbon. Better information about 

the spatial extent of woody encroachment, 

the amount and growth of woody vegetation, 

and variation in impacts on soil carbon stocks 

would help reduce the large uncertainty of the 

carbon impacts of woody encroachment.

10.1 INVENTORY

10.1.1 Background

Agricultural and grazing lands (cropland, pasture, rangeland, shrublands, and arid lands)2

 occupy 47% of the land 

area in North America (59% in the United States, 70% in 

Mexico, and 11% in Canada), and contain 17% of the terrestrial carbon. Most of the carbon in these ecosystems is held 

in soils. Live vegetation in cropland generally contains less 

than 5% of total carbon, whereas vegetation in grazing lands 

contains a greater proportion (5–30%), but still less than 

that in forested systems (30–65%). Agricultural and grazing lands in North America contain 78.5 ± 19.5 (±1 standard 

error) billion tons of organic carbon (Gt C) in the soil (Table 

10.1). Significant increases in vegetation carbon stocks in 

some grazing lands have been observed and, together with 

soil carbon stocks from croplands and grazing lands, likely 

contribute significantly to the large North American terrestrial carbon sink (Houghton et al., 1999; Pacala et al., 

2001; Eve et al., 2002; Ogle et al., 2003). These lands also 

emit greenhouse gases: fossil-fuel use for on-farm machinery and buildings, for 

manufacture of agricultural inputs, and for 

transportation account 

for 3–5% of total carbon 

dioxide (CO2) emissions 

in developed countries 

(Enquete Commission, 

1995); activities on agricultural and grazing 

2

 We refer collectively to pasture, rangeland, shrublands, and arid 

lands as grazing lands since grazing is their primary use, even though 

not all of these lands are grazed.

•

•

lands, like livestock production, animal waste management, 

biomass burning, and rice cultivation emit 35% of global 

anthropogenic methane (CH4) (27% of United States’, 31% 

of Mexican, and 27% of Canadian CH4 emissions) (Mosier 

et al., 1998b; CISCC, 2001; Ministry of the Environment, 

2006; EPA, 2006); and agricultural and grazing lands are the 

largest anthropogenic source of nitrous oxide (N2O) emissions (CAST, 2004; see Box 10.1). However, agricultural and 

grazing lands are actively managed and have the capacity 

to take up and store carbon. Thus

 improving management could lead to substantial reductions 

in CO2 and CH4 emissions and could sequester carbon to 

offset emissions from other lands or sectors.

10.1.2 Carbon Dioxide Fluxes From 

Agricultural and Grazing Land

The main processes governing the carbon balance of agricultural and grazing lands are the same as for other ecosystems: 

the photosynthetic uptake and assimilation of CO2 into 

organic compounds, the release of gaseous carbon through 

respiration (primarily CO2 but also CH4), and fire. Like other 

terrestrial ecosystems in general, for which CO2 emissions 

are approximately two orders of magnitude greater than CH4

emissions, carbon cycling in most agricultural and grazing 

lands is dominated by fluxes of CO2 rather than CH4. In 

agricultural lands, carbon assimilation is directed towards 

production of food, fiber, and forage by manipulating species 

composition and growing conditions (soil fertility, irrigation, etc.). Biomass, being predominantly herbaceous (i.e., 

non-woody), is a small, transient carbon pool (compared 

to forests) and hence soils constitute the dominant carbon 

stock. Cropland systems can be among the most productive 

ecosystems, but in some cases restricted growing season 

length, fallow periods, and grazing-induced shifts in species 

Agricultural and grazing lands 

are actively managed and have 

the capacity to take up and 

store carbon. Thus improving 

management could lead to 

substantial reductions in 

CO2 and CH4 emissions.

Nitrous oxide (N2O) is the most potent greenhouse gas 

in terms of global warming potential, with a radiative 

forcing 296 times that of CO2 (IPCC, 2001). Agricultural 

activities that add mineral or organic nitrogen (fertilization, plant N2 fixation, manure additions, etc.) augment 

naturally occurring N2O emissions from nitrification and 

denitrification by 0.0125 kg N2O per kg nitrogen applied 

(Mosier et al., 1998a). Agriculture contributes significantly 

to total global N2O fluxes through soil emissions (35% 

of total global emissions), animal waste handling (12%), 

nitrate leaching (7%), synthetic fertilizer application (5%), 

grazing animals (4%), and crop residue management (2%). 

Agriculture is the largest source of N2O in the United 

States (78% of total N2O emissions), Canada (59%), and 

Mexico (76%).

BOX 10.1: Nitrous Oxide Emissions From 

Agricultural and Grazing Lands 
109

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

Inorganic carbon in the soil is comprised of primary carbonate minerals, such as calcite (CaCO3) or 

dolomite (CaMg[CO3]2), or secondary minerals formed when carbonate (CO3

2–), derived from soil 

CO2, combines with base cations (e.g., Ca2+, Mg2+) and precipitates within the soil profile in arid and 

semi-arid ecosystems. Weathering of primary carbonate minerals in humid regions can be a source 

of CO2, whereas formation of secondary carbonates in drier areas is a sink for CO2; however, the 

magnitude of either flux is highly uncertain. Agricultural liming involves addition of primary carbonate 

minerals to the acid soils to increase the pH. In Canada and the United States, about 0.1 and 1.1 Mt 

C per year is emitted from liming (Sobool and Kulshreshtha, 2005; EPA, 2006). Inorganic carbon 

stocks in North America have been estimated at 66.8 Gt C (Sombroek et al., 1993).

BOX 10.2: Inorganic Soil Carbon

in Agricultural and Grazing Ecosystems

Practice Temperate dry b,c Temperate wet Tropical dry Tropical wet Total

Agricultural lands

Canada 1.79±0.35

(17.3)

1.77±0.36

(22.1) – – 3.60±0.77(39.4)

Mexico – – 0.24±0.06

(3.9)

0.53±0.14

(10.2)

0.81±0.22

(14.1)

United States 3.31±0.74

(34.8)

8.66±2.18

(108.4)

0.35±0.08

(5.6)

1.53±0.33

(28.4)

14.05±3.20

(177.1)

Total 5.16±1.07

(52.1)

10.57±2.42

(130.5)

0.61±0.14

(9.5)

2.18±0.54

(38.6)

18.5±4.16

(230.6)

Grazing lands

Canada 2.17±0.55

(18.4)

9.49±1.27

(40.8) – – 11.66±4.88(59.2)

Mexico – – 7.20±1.62

(99.1)

2.19±0.58

(20.3)

9.99±2.60

(119.4)

United States 16.89±3.62

(209.9)

5.67±1.39

(55.0)

4.26±0.98

(68.1)

4.30±0.89

(46.7)

32.88±7.18

(379.7)

Total 19.34±4.27

(228.3)

21.07±5.80

(95.8)

12.59±2.73

(167.1)

6.94±1.86

(67.0)

59.95±14.65

(558.2)

Table 10.1 Soil organic carbon pools in agricultural and grazing lands in Canada, Mexico, and the United 

States. The data values are given in Gt C. The area (in millions of hectares) for each climatic zone is in 

parentheses. Current soil carbon stocks are secondary quantities derived from an initial starting point of 

undisturbed native ecosystems carbon stocks, which were quantified using the intersection of (Moderate 

Resolution Imaging Spectroradiometer-International Geosphere-Biosphere Programme) MODIS-IGBPa 

land cover types (Friedl et al., 2002) and mean soil carbon contents to 1-m depth from Sombroek et al.

(1993), spatially arrayed using Food and Agriculture Organization soil classes (ISRIC, 2002), and summed 

by climate zone. These undisturbed native ecosystem carbon stock values were then multiplied by soil 

carbon loss factors for tillage- and overgrazing-induced losses (Nabuurs et al., 2004; Ogle et al., 2004) to 

estimate current soil carbon stocks (see Figure 10.2). Uncertainties (± one standard error) were derived 

from uncertainty associated with soil carbon stocks and soil carbon loss factors.

a Cropland area was derived from the IGBP cropland land cover class plus the area in the cropland/natural vegetation IGBP class in 

Mexico and one-half of the area in the cropland/natural vegetation IGBP class in Canada and the United States. Grazing land area 

includes IGBP woody savannas, savannas, and grasslands in all three countries, plus open shrubland in Mexico and open shrublands 

(not in Alaska) in the United States.

b Temperate zones are those located above 30o latitude. Tropical zones (below 30o latitude) include subtropical regions.

c Dry climates were defined as those where the ratio of mean annual precipitation (MAP) to potential evapotranspiration (PET) is 

less than one; in wet areas, MAP/PET is greater than one.
The U.S. Climate Change Science Program Chapter 10

110 

composition or production can reduce carbon uptake 

relative to that in other ecosystems. These factors, 

along with tillage-induced soil disturbances and 

removal of plant carbon through harvest, have depleted soil carbon stocks by 20-40% (or more) from 

pre-cultivated conditions (Davidson and Ackerman, 

1993; Houghton and Goodale, 2004). Soil organic 

carbon stocks in grazing lands (see Box 10.2 for 

information on inorganic soil carbon stocks) have 

been depleted to a lesser degree than for cropland 

(Ogle et al., 2004), and in some regions biomass 

has increased due to suppression of disturbance and 

subsequent woody encroachment (see Box 10.3). 

Woody encroachment is potentially a significant 

sink for atmospheric CO2, but the magnitude of the 

sink is poorly constrained (Houghton et al., 1999; 

Pacala et al., 2001). Since woody encroachment 

leads to decreased forage production, management practices 

are aimed at reversing it, with 

c o n s e q u e n t 

reductions in 

biomass carbon. Dis- turbance-induced increases in decomposition rates of aboveground litter and harvest removal of some (30–50% of forage 

in grazing systems, 40–50% in grain crops) or all (e.g., corn 

for silage) of the above-ground biomass, have drastically 

altered carbon cycling within agricultural lands and thus 

the sources and sinks of CO2 to the atmosphere.

Much of the carbon lost from agricultural soil and biomass 

pools can be recovered with changes in management practices that increase carbon inputs, stabilize carbon within 

the system, or reduce carbon losses, while still maintaining 

outputs of food, fiber, and forage. Increased production, 

increased residue carbon inputs to the soil, and increased 

organic matter additions have reversed historic soil carbon 

losses in long-term experimental plots (e.g., Buyanovsky and 

Wagner, 1998). However, the management practices that promote soil carbon sequestration would need to be maintained 

over time to avoid subsequent losses of sequestered carbon. 

Across Canada and the United States, mineral soils have 

been sequestering 2.5† and 17.0 ± 0.45 million metric tons of 

carbon (Mt C) per year3 (Ministry of the Environment, 2006; 

Ogle et al., 2003; EPA, 2006), respectively, largely through 

increased production and improved management practices 

on annual cropland (Figure 10.1, Table 10.2). Conversion of 

agricultural land to grassland, like under the Conservation 

Reserve Program in the United States (7.6–11.5 Mt C per 

year on 31.5 million acres [12.5 million hectares] of land), 

and afforestation have also sequestered carbon in agricul3 † A dagger symbol indicates that the magnitude and/or range of 

uncertainty for the given numerical value(s) is not provided in the 

references cited.

Much of the carbon lost from 

agricultural soil and biomass 

pools can be recovered with 

changes in management practices.

Figure 10.1 North American agricultural and grazing land CO2 (left 

side) and CH4 (right side), adjusted for global warming potential. All 

units are in Mt C-equivalent per year for years around 2000. Negative values indicate net flux from the atmosphere to soil and biomass 

carbon pools (i.e., sequestration). All data are from Canadian (Matin 

et al., 2004) and U.S. (EPA, 2006) National Inventories and from the 

second Mexican National Communication (CISCC, 2001), except for 

Canadian (from Kulshreshtha et al., 2000) and U.S. fossil-fuel inputs 

(from Lal et al., 1998) and woody encroachment (from Houghton 

et al., 1999). Values are for 2003 for Canada, 1998 for Mexico, and 

2004 for the United States. A global warming potential of 23 for 

methane was used to convert emissions of CH4 to CO2 equivalents 

(IPCC, 2001) and a factor of 12/44 to convert from CO2 to carbon. 

Asterisks indicate unavailable data. Data ranges are indicated by error bars where available.

Encroachment of woody species into grasslands—caused 

by overgrazing-induced reduction in grass biomass and 

subsequent reduction or elimination of grassland fires—is 

widespread in the United States and Mexico, decreases 

forage production, and is unlikely to be reversed without costly mechanical intervention (Van Auken, 2000). 

Encroachment of woody species into grassland tends to 

increase biomass carbon stocks by one million grams 

of carbon (1 Mg C) per hectare per year (Pacala et al., 

2001), with estimated net sequestration of 120–130 Mt 

C per year in encroaching woody biomass (Houghton 

et al., 1999; Pacala et al., 2001). In response to woody 

encroachment, soil organic carbon stocks can significantly increase or decrease, thus predicting impacts on 

soil carbon or ecosystem carbon stocks is very difficult 

(Jackson et al., 2002). Invasion of grass species into native 

shrublands tends to lead to the release of soil organic 

carbon (Bradley et al., 2006).

BOX 10.3: Impacts of Woody 

Encroachment Into Grasslands on 

Ecosystem Carbon Stocks 
111

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

tural and grazing lands (Follett et al., 2001a). In contrast, 

cultivation of organic soils (e.g., peat-derived soils) is releasing an estimated 0.1 and 8.3 ± 3.2 Mt C per year†

 from 

soils in Canada and the United States (Matin et al., 2004; 

Ministry of the Environment, 2006; Ogle et al., 2003; EPA, 

2006). Compared with other systems, the high productivity and management-induced disturbances of agricultural 

systems promote movement and redistribution (through 

erosion, runoff, and leaching) of organic and inorganic 

carbon, sequestering potentially large amounts of carbon 

in sediments and water (Raymond and Cole, 2003; Smith 

et al., 2005; Yoo et al., 2005). However, the net impact of 

soil erosion on carbon emissions to the atmosphere remains 

highly uncertain.

Production, delivery, and use of field equipment, fertilizer, 

seed, pesticides, irrigation water, and maintenance of animal 

production facilities contribute 3–5% of total fossil-fuel CO2

emissions in developed countries (Enquete Commission, 

1995). On-farm fossil-fuel emissions together with manufacture of fertilizers and pesticides contribute emissions of 

32.7 Mt C per year† within the United States (Lal et al., 1998) 

and 4.6 Mt C per year in Canada (Kulshreshtha et al., 2000) 

(Table 10.2). Energy consumption for heating and cooling 

high intensity animal production facilities is among the 

largest CO2 emitters within the 

agricultural sector (Enquete 

Commission, 1995).

Much of the ammonia production and urea application 

(United States: 4.3 Mt C per 

year; Mexico: 0.4 Mt C per 

year; Canada: 1.7 Mt C per 

year) and phosphoric acid 

manufacture (United States: 

0.4 Mt C per year; Mexico: 

0.2 Mt C per year; Canada: 

not reported) are devoted to 

agricultural uses.

10.1.3 Methane Fluxes 

From Agricultural 

and Grazing Lands

Cropland and grazing land 

soils act as both sources and 

sinks for atmospheric CH4. 

Methane formation is an anaerobic process and is most 

significant in waterlogged 

soils, like those under paddy 

rice cultivation (United States: 

0.25 ± 0.28 Mt CH4-C per 

year; Mexico: 0.01 Mt CH4-C 

per year†; Canada: negligible, not reported; Table 10.2). 

Methane is also formed by incomplete biomass combustion 

of crop residues (United States: 0.03 ± 0.02 Mt CH4-C per 

year; Mexico: <0.01 Mt CH4-C per year; Canada: negligible, 

not reported; Table 10.2). Methane oxidation in soils is a 

global sink for about 5% of CH4 produced annually and 

is mainly limited by CH4 diffusion into the soil. However, 

intensive cropland management tends to reduce soil CH4

consumption relative to forests and extensively managed 

grazing lands (CAST, 2004). Management-induced changes 

in CH4-C fluxes have a smaller impact on terrestrial carbon 

cycling than changes in CO2-C fluxes (Table 10.2), but relatively greater radiative forcing for CH4 amplifies the impact 

of increasing atmospheric CH4 concentrations on net radiative forcing (Figure 10.1). Recent research has shown that 

live plant biomass and litter produce substantial amounts of 

CH4, potentially making plants as large a source of CH4 as 

livestock (Keppler et al., 2006). If this is the case, activities 

that increase plant biomass (and sequester CO2) may lead to 

increased CH4 production (Keppler et al., 2006).

10.1.4 Methane Fluxes From Livestock

Enteric fermentation (the process of organic matter breakdown by gut flora within the gastrointestinal tract of animals, 

particularly ruminants) allows for the digestion of fibrous 

Canada Mexico United States Total

CO2

On-farm fossil-fuel use 2.9a ND 28b 30.9

Fertilizer manufacture 1.7 ND 4.7 6.4

Mineral soil carbon sequestration (2.5) ND (17±0.45) (19.1) – (20.0)

Organic soil cultivation 0.1 ND 8.3±3.2 5.6 – 11.9

Agricultural liming 0.1 ND 1.1 1.2

Woody encroachment ND ND (120)c (120)

Total 2.3 ND (114.7) – (120.1) (117) – (122.4)

CH4

Rice production 0 0.011 0.25±0.28 0.26

Biomass burning <0.01 <0.01 0.03±0.02 0.05

Livestock 0.62 1.48 3.67±0.53 5.93

Manure 0.18 0.05 1.28±0.24 1.60

Total 0.80 1.54 5.23 7.84

ND = no data reported.

a

 From Kulshreshtha et al. (2000).

b

 From Lal et al. (1998).

c

 From Houghton et al. (1999).

Table 10.2 North American agricultural and grazing land carbon fluxes for 

the years around 2000. All units are in Mt C per year. Negative numbers (in 

parentheses) indicate net flux from the atmosphere to soil and biomass carbon 

pools. Unless otherwise noted, data are from Canadian (Matin et al., 2004) and 

United States’ National Inventories (EPA, 2006), and from the Second Mexican 

National Communication (CISCC, 2001). Values are for 2003 for the United States 

and Canada, and 1998 for Mexico. A factor of 12/44 was used to convert from CO2

to carbon and a factor of 12/16 to convert CH4 to carbon
The U.S. Climate Change Science Program Chapter 10

112 

materials by livestock, but the extensive fermentation of the 

ruminant diet requires 5–7% of the dietary gross energy to 

be belched out as CH4 to sustain the anaerobic processes 

(Johnson and Johnson, 1995). Methane emissions from 

livestock contribute significantly to total CH4 emissions 

in the United States (3.7 ± 0.53 Mt CH4-C per year, 20% of 

total United States’ CH4 emissions), Canada (0.78 ± 0.14 Mt 

CH4-C per year, 22% of total) (Ministry of the Environment, 

2006; Sobool and Kulshreshtha, 2005), and Mexico (1.5 Mt 

CH4-C per year, 27% of total)† with the vast majority of enteric CH4 emissions from beef (72%) and dairy cattle (23%) 

(Table 10.2). Emissions from ruminants are tightly coupled 

to feed consumption, since CH4 emission per unit of feed 

energy is relatively constant, except for feedlot cattle with 

diets high in cereal grain contents, for which the fractional 

loss falls to one-third to one-half of normal rates (Johnson 

and Johnson, 1995). Between 1990 and 2002, CH4 emissions from enteric fermentation fell 2% in the United States 

but increased by 20% 

in Canada (EPA, 2000; 

Matin et al., 2004).

Met h a ne e m ission s 

during manure storage 

(United States: 1.3 ± 

0.24 Mt CH4 per year; 

Mexico: 0.06 Mt CH4 per 

year †; Canada: 0.3 ± 0.05 Mt CH4 per year) are governed by 

the amount of degradable organic matter, degree of anoxia, 

storage temperature, and 

duration of storage. Unlike enteric CH4, the major 

sources of manure CH4

emissions in the United 

States are from swine (44%) 

and dairy cattle (39%). 

Manure CH4 production is 

greater for production systems with anoxic lagoons, 

largely anoxic pits, or manure handled or stored as 

slurry. Between 1990 and 

2002, CH4 emissions from 

manure management increased 25% in the United 

States and 21% in Canada 

(EPA, 2000; Matin et al., 

2004).

10.2 DRIVERS AND 

TRENDS 

The extent to which agriculture will contribute 

to greenhouse gas mitigation will largely depend on government policy decisions, but mitigation opportunities 

will also be constrained by technological advances and 

changing environmental conditions (see discussion below). 

Estimates from national inventories suggest that United 

States’ and Canadian agricultural soils are currently near 

neutral or small net sinks for CO2, which has occurred as a 

consequence of changing management (e.g., reduced tillage 

intensity) and government programs designed for purposes 

other than greenhouse gas mitigation (e.g., soil conservation, 

commodity regulation). However, to realize the much larger 

potential for soil carbon sequestration (see section below) 

and for significant reductions in CH4 (and N2O) emissions, 

specific policies targeted at greenhouse gas reductions are 

required. It is generally recognized that farmers (and other 

economic actors) are, as a group, “profit-maximizers,” which 

implies that to change from current practices to ones that 

reduce net emissions, farmers will incur additional costs 

(termed “opportunity costs”). Hence, where the incentives (e.g., carbon offset market payments, government 

subsidies) to adopt new practices exceed the opportunity 

costs, farmers will adopt new practices. Crop productivity, 

production input expenses, marketing costs, etc. (which 

determine profitability) vary widely within (and between) 

countries. Thus, the payment needed to achieve a unit of 

emission reduction will vary, among and within regions. In 

general, each successive increment of carbon sequestration 

or emission reduction comes at a progressively higher cost 

Figure 10.2 Relative soil carbon following implementation of new agricultural or grassland management practices. Conventionally tilled, medium-input cultivated land and moderately grazed grasslands 

with moderate inputs are defaults for agricultural and grazing lands, respectively. Default soil carbon 

stocks (like those in Table 10.1) can be multiplied by one or more stock change factors to estimate 

carbon sequestration rates (over a 20-year time period). The dashed horizontal line indicates default 

soil carbon stocks (i.e., those under conventional-tillage cropland or undegraded grazingland, with 

medium inputs). Temperature/precipitation divisions are the same as those described in Table 10.1. 

Data are from Nabuurs et al. (2004) and Ogle et al. (2004).

Where the incentives (e.g., 

carbon offset market payments, 

government subsidies) to 

adopt new practices exceed 

the opportunity costs, farmers 

will adopt new practices.
113

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

(this relationship is often shown in the form of an upward 

bending marginal cost curve).

The interaction of changes in technological and environmental conditions, including crop growth improvements, 

impacts of CO2 increase, nitrogen deposition, and climate 

change, will shape future trends in greenhouse gas emissions and mitigation from agricultural and grazing lands. 

A continuation of the yield increases seen in the past 

several decades for agricultural crops (Reilly and Fuglie, 

1998) would tend to enhance the potential for soil carbon 

sequestration (CAST, 2004). Similarly, increased plant 

growth due to higher concentrations of CO2 (and nitrogen 

deposition) has been projected to boost carbon uptake on 

agricultural (and other) lands, offsetting some or all of 

the climate-change induced reductions in productivity 

projected in some regions of North America (NAS, 2001). 

However, recent syntheses from field-scale FACE (Free-Air 

Carbon dioxide Enrichment) studies of croplands (Long 

et al., 2006) and grasslands (Nowak et al., 2004) suggest 

that the growth enhancement from CO2 fertilization may 

be much less than previously thought. Feedbacks between 

temperature and soil carbon stocks could counteract efforts 

to reduce greenhouse gases via carbon sequestration within 

agricultural ecosystems. Increased temperatures tend to 

increase the rate of biological processes—including plant 

respiration and organic matter decay, and CO2 release by soil 

organisms—particularly in temperate climates that prevail 

across most of North America. Because soil carbon stocks, 

including those in agricultural lands, contain such large 

amounts of carbon, small percentage increases in the rate of 

soil organic matter decomposition could lead to substantially 

increased emissions (Jenkinson et al., 1991; Cox et al., 2000). 

There is currently a scientific debate about the relative temperature sensitivity of the different constituents making up 

soil organic matter (e.g., Kätterer et al., 1998; Giardina and 

Ryan, 2000; Ågren and Bosatta, 2002; Knorr et al., 2005), 

reflecting uncertainty in the possible degree and magnitude 

of climate change feedbacks. Despite this uncertainty, the 

potential for climate and other environmental feedbacks 

to influence the carbon balance of agricultural systems by 

perturbing productivity (and carbon input rates) and organic 

matter turnover, and potentially soil N2O and CH4 fluxes, 

cannot be overlooked.

10.3 OPTIONS FOR MANAGEMENT

10.3.1 Carbon Sequestration

Agricultural and grazing land management practices capable 

of increasing carbon inputs or decreasing carbon outputs, 

while still maintaining yields, can be divided into two 

classes: those that impact carbon inputs, and those that affect 

carbon release through decomposition and disturbance. Reversion to native vegetation or setting agricultural land aside 

as grassland, such as in the Canadian Prairie Cover Program 

and the U.S. Conservation Reserve Program, can increase 

the proportion of photosynthesized carbon retained in the 

system and sequester carbon in the soil4 (Conant et al., 2001; 

Post and Kwon, 2000; Follett et al., 2001b) (Figure 10.2). In 

annual cropland, improved crop rotations, yield enhancement measures, organic amendments, cover crops, improved 

fertilization and irrigation practices, and reduced bare fallow 

tend to increase productivity and carbon inputs, and thus soil 

carbon stocks (Lal et al., 1998; Paustian et al., 1998; VandenBygaart et al., 2003) (Figure 10.2). Tillage, traditionally used 

for soil preparation and weed control, disturbs the soil and 

stimulates decomposition and loss of soil carbon. Practices 

that substantially reduce (reduced-till) or eliminate (no-till) 

tillage-induced disturbances are being increasingly adopted 

and generally increase soil carbon stocks while maintaining or enhancing productivity levels (Paustian et al., 1997; 

Ogle et al., 2003) (Figure 10.2). Estimates of the technical 

potential for annual cropland soil carbon sequestration are 

on the order of 50–100 Mt C per year in the United States 

(Lal et al., 2003; Sperow et al., 2003) and 3.3–6.4 Mt C per 

year in Canada (Boehm et al., 2004).

Within grazing lands, historical overgrazing has substantially reduced productive capacity in many areas, leading 

to loss of soil carbon stocks (Conant and Paustian, 2002) 

(Figure 10.2). Conversely, improved grazing management 

and production inputs (like fertilizer, adding (nitrogenfixing) legumes, organic amendments, and irrigation) can 

increase productivity, carbon inputs, and soil carbon stocks 

(Conant et al., 2001), potentially storing 0.44 Mt C per year†

in Canada (Lynch et al., 2005) and as much as 16–54 (mean 

= 33.2) Mt C per year in the United States (Follett et al., 

2001a). Such improvements will carry a carbon cost, par4

 The bulk of carbon sequestration potential in agricultural and 

grazing lands is restricted to soil carbon pools, though carbon can be 

sequestered in woody biomass in agroforestry systems (Sheinbaum 

and Masera, 2000). Woody encroachment on grasslands can also 

store substantial amounts of carbon in biomass, but the phenomenon 

is neither well-controlled nor desirable from the standpoint of livestock production, since it results in decreased forage productivity, 

and the impacts on soil carbon pools are highly variable and poorly 

understood.
The U.S. Climate Change Science Program Chapter 10

114 

ticularly fertilization and irrigation, since their production 

and implementation require the use of fossil fuels.

10.3.2 Fossil-Fuel Derived Emission Reductions

The efficiency with 

which on-farm (from 

tractors and machinery) 

and off-farm (from production of agricultural 

input) energy inputs 

are converted to agricultural products varies 

several-fold (Lal, 2004). 

Where more energy-efficient practices can be substituted for 

less efficient ones, fossil-fuel CO2 emissions can be reduced 

(Lal, 2004). For example, converting from conventional 

plowing to no-tillage can reduce on-farm fossil-fuel emissions by 25–80% (Frye, 1984; Robertson et al., 2000) and 

total fossil-fuel emissions by 14–25% (West and Marland, 

2003). Substitution of legumes for mineral nitrogen can reduce energy input by 15% in cropping systems incorporating 

legumes (Pimentel et al., 2005). More efficient heating and 

cooling (e.g., better building insulation) could reduce CO2

emissions associated with housed animal facilities (e.g., 

dairy). Substitution of crop-derived fuels for fossil fuels 

could decrease net emissions.

Energy intensity (energy per unit product) for the United 

States’ agricultural sector has declined since the 1970s 

(Paustian et al., 1998). Between 1990 and 2000, fossil-fuel 

emissions on Canadian farms increased by 35%† (Sobool 

and Kulshreshtha, 2005). 

10.3.3 Methane Emission Reduction

Reducing flood duration and decreasing organic matter 

additions to paddy rice fields can reduce CH4 emissions. 

Soil amendments such as ammonium sulfate and calcium 

carbide inhibit CH4 formation. Coupled with adoption of 

new rice cultivars that favor lower CH4 emissions, these 

management practices could reduce CH4 emission from 

paddy rice systems by 16–70% (mean = 40%) of current 

emissions (Mosier et al., 1998b).

Biomass burning is uncommon in most Canadian and 

United States’ crop production systems; less than 3% of 

crop residues are burned annually in the United States (EPA, 

2006). Biomass burning in conjunction with land clearing and with subsistence 

agriculture still occurs in 

Mexico, but these practices 

are declining. The primary 

path for emission reduction 

is reducing residue burning 

(CAST, 2004).

Refinement of feed quality, feed rationing, additives, and 

livestock production efficiency chains can all reduce CH4

emissions from ruminant livestock with minimal impacts 

on productivity or profits (CAST, 2004). Boadi et al. (2004) 

review several examples of increases in energy intensity. 

Wider adoption of more efficient practices could reduce 

CH4 production from 5–8% to 2–3% of gross feed energy 

(Agriculture and Agri-Food Canada, 1999), reducing CH4

emissions by 20–30% (Mosier et al., 1998b).

Methane emissions from manure storage are proportional to 

duration of storage under anoxic conditions. Handling solid 

rather than liquid manure, storing manure for shorter periods 

of time, and keeping storage tanks cool can reduce emissions 

from stored manure (CAST, 2004). More important, capture 

of CH4 produced during anaerobic decomposition of manure 

(in covered lagoons or small- or large-scale digesters) can 

reduce emissions by 70–80% (Mosier et al., 1998b). Use of 

digester systems is spreading in the United States, with 50 

digesters currently in operation and 60 systems in construction or planned (NRCS, 2005). Energy production using CH4

captured during manure storage will reduce energy demands 

and associated CO2 emissions.

10.3.4 Environmental Co-benefits From Carbon 

Sequestration and Emission Reduction Activities

Many of the practices that lead to carbon sequestration and 

reduced CO2 and CH4 emissions not only increase production efficiencies but also lead to environmental co-benefits. 

Practices that sequester carbon in agricultural and grazing 

land soils improve soil fertility, buffering capacity, and pesticide immobilization (Lal, 2002; CAST, 2004). Increasing 

soil carbon content makes the soil more easily workable and 

reduces energy requirements for field operations (CAST, 

2004). Decreasing soil disturbance and retaining more surface crop residues enhance water infiltration and prevent 

wind and water erosion, improving air quality. Increased 

water retention plus improved fertilizer management reduces 

nitrogen losses and subsequent nitrate (NO3ˉ) leaching and 

downstream eutrophication.

10.3.5 Economics and Policy Assessment

Policies for agricultural mitigation activities can range 

from transfer payments (such as subsidies, tax credits, etc.) 

to encourage greenhouse gas mitigating practices or taxes 

or penalties to discourage practices with high emissions, to 

emission offset trading in a free market-based system with 

governmental sanction. Currently the policy context of the 

three North American countries differs greatly. Canada and 

the United States are both Annex 1 (developed countries) 

within the United Nations Framework Convention on Climate 

Change (UNFCCC), but Canada is obligated to mandatory 

emission reductions as a party to the Kyoto Protocol, while 

the United States currently maintains a national, voluntary 

Converting from conventional 

plowing to no-tillage can reduce 

on-farm fossil-fuel emissions 

by 25–80% and total fossilfuel emissions by 14–25%.

Practices that sequester 

carbon in agricultural and 

grazing land soils improve soil 

fertility, buffering capacity, and 

pesticide immobilization.
115

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

em ission 

reduction 

p o l i c y 

o u t s i d e 

of Kyoto. 

Mexico is 

a non-Annex 1 (developing) 

c o u n t r y 

and thus is not currently subject to mandatory emission 

reductions under Kyoto.

At present, there is relatively little practical experience upon 

which to judge the costs and effectiveness of agricultural 

mitigation activities. Governments are still in the process of 

developing policies and, moreover, the economics of various mitigation activities will only be known when there is a 

significant economic incentive for emission reductions, e.g., 

through regulatory emission caps or government-sponsored 

bids and contracts. However, several economic analyses 

have been performed in the United States, using a variety 

of models (e.g., McCarl and Schneider, 2001; Antle et al., 

2003; Lewandrowski et al., 2004). Most studies have focused 

on carbon sequestration, and less work has been done on 

the economics of reducing CH4 and N2O emissions. While 

results differ between models and for different parts of the 

country, some preliminary conclusions have been drawn 

(see Boehm et al., 2004; CAST, 2004).

• Additional carbon (10–70 Mt C per year), above current 

rates, could be sequestered in soils at low to moderate 

costs ($10–100 per metric ton of carbon).

• Mitigation practices that maintain the primary income 

source (i.e., crop/livestock production), such as conservation tillage and pasture improvement, have a lower cost 

per ton sequestered carbon compared with practices 

where mitigation would be a primary income source (i.e., 

foregoing income from crop and/or livestock production), 

such as land set-asides, even if the latter have a higher 

biological sequestration potential.

• With higher energy prices, major shifts in land use in 

favor of energy crops and afforestation may occur at the 

expense of annual cropland and pasture.

• Policies based on per-ton payments (for carbon actually 

sequestered) are more economically efficient than perhectare payments (for adopting specific practices, see 

Antle et al., 2003), although the former have a higher verification cost (i.e., measuring actual carbon sequestered 

versus measuring adoption of specific farming practices 

on a given area of land).

A recent study commissioned by the U.S. Environmental 

Protection Agency (EPA, 2005), evaluated some agricultural 

mitigation options for different policy scenarios, including 

constant CO2 price scenarios for 2010–2110, where the price 

represents the incentive required for the mitigation activity. 

Annualized prices of $15/ton of CO2 would yield mitigation 

amounts of 46 Mt C per year through agricultural soil carbon sequestration and 14.5 Mt C per year from fossil-fuel 

use reduction (compared with the estimated United States’ 

national ecosystem carbon sink of 480 Mt C per year). At 

lower prices of $5/ton CO2, the corresponding values would 

be 34 Mt C per year (for soil sequestration) and 9 Mt C per 

year (for fossil-fuel reduction), respectively, reflecting the 

effect of price on the supply of mitigation activities5.

10.3.6 Other Policy Considerations

Agricultural mitigation of CO2 through carbon sequestration and emission reductions for CH4 (and N2O), differ in 

ways that impact policy design and implementation. Direct 

emission reductions of CH4 and CO2 from fossil-fuel use 

are considered “permanent” reductions, while carbon sequestration is a “non-permanent” reduction, in that carbon 

stored through conservation practices could potentially be 

re-emitted if management practices revert back to the previous state or otherwise change so that the stored carbon is 

lost. This permanence issue applies to all forms of carbon 

sinks. In addition, soil carbon storage, with a given change 

in management (e.g., tillage reduction, pasture improvement, 

afforestation), will tend to level off at a new steady state level 

after 15–30 years, after which there is no further accumulation of carbon (West et al., 2004). Enhanced management 

practices must be sustained to maintain these higher carbon 

stocks. Key implications for policy are that the value of 

sequestered carbon could be discounted compared to direct 

emission reductions to compensate for the possibility of 

future emissions. Alternatively, long-term contracts will 

be needed to build and maintain carbon stocks, which will 

tend to increase the price per unit of sequestered carbon. 

However, even temporary storage of carbon has economic 

value (CAST, 2004), and various proposed concepts of 

leasing carbon storage or applying discount rates could accommodate carbon sequestration as part of a carbon offset 

trading system (CAST, 2004). In addition, switching to 

practices that increase soil carbon (and hence, improve soil 

fertility) could be more profitable to farmers in the longrun, so that additional incentives to maintain the practices 

once they become well established may not be necessary 

(Paustian et al., 2006).

Another policy issue relating to carbon sequestration is 

leakage (also termed “slippage” in economics), whereby 

mitigation actions in one area (e.g., geographic region, pro5 These estimates were produced using a national-scale economic 

sector model which estimates the linkage between CO2 prices and the 

supply of mitigation activities, for specified price scenarios. Hence, 

the model can produce a range of CO2 mitigation amounts as a function of price, but the model was not used to estimate the uncertainty 

of mitigation amounts at a given price level. 
The U.S. Climate Change Science Program Chapter 10

116 

duction system) stimulate additional emissions elsewhere. 

For forest carbon sequestration, leakage is a major concern. 

For example, reducing harvest rates in one area (thereby 

maintaining higher biomass carbon stocks) can stimulate 

increased cutting and reduction in stored carbon in other 

areas, as was seen with the reduction in harvesting in the 

Pacific Northwest during the 1990s (Murray et al., 2004). 

Preliminary studies suggest that leakage is of minor concern 

for agricultural carbon sequestration, since most practices 

would have little or no effect on the supply and demand of 

agricultural commodities. However, there are uncertain and 

conflicting views on whether land-set asides in which land is 

taken out of agricultural production, such as the Conservation Reserve Program in the United States, might be subject 

to significant leakage.

A further question, relevant to policies for carbon sequestration, is how practices for conserving carbon affect emissions 

of other greenhouse gases. Of particular importance is the 

interaction of carbon sequestration with N2O emissions, 

because N2O is such a potent greenhouse gas (Robertson 

and Grace, 2004; Six et al., 2004; Gregorich et al., 2005). 

(See Box 10.4). In some environs, carbon-sequestration practices, such as reduced tillage, can stimulate N2O emissions, 

thereby offsetting part of the benefit; elsewhere, carbon-conserving practices may suppress N2O emissions, amplifying 

the net benefit (Smith et al., 2001; Smith and Conen, 2004; 

Conant et al., 2005; Helgason et al., 2005).

Similarly, carbon-sequestration practices might affect 

emissions of CH4, if the practice, such as increased use 

of forages in rotations, leads to higher livestock numbers. 

These examples demonstrate that policies designed to 

suppress emission of one greenhouse gas, need to also 

consider complex interactions to ensure that net emissions of total greenhouse gases are reduced.

A variety of other factors will affect the willingness of 

farmers to adopt greenhouse gas reducing practices and 

the efficacy of agricultural policies, including perceptions 

of risk, information and extension efforts, technological 

developments, and social and ethical values (Paustian et 

al., 2006). Many of these factors are difficult to incorporate into traditional economic analyses. Pilot mitigation 

projects, along with additional research using integrated 

ecosystem and economic assessment approaches (e.g., 

Antle et al., 2001), will allow us to get a clearer picture 

of the actual potential of agriculture to contribute to 

greenhouse gas mitigation efforts.

10.4 RESEARCH AND DEVELOPMENT 

NEEDS

Expanding the network of intensive research sites 

dedicated to understanding basic processes, coupled with 

national-level networks of soil monitoring/validation sites, 

could reduce inventory uncertainty and contribute to attributing changes in ecosystem carbon stocks to changes 

in land management (see Bellamy et al., 2005). Expansion 

of both networks should be informed about how different 

geographic areas and ecosystems contribute to uncertainty 

and the likelihood that reducing uncertainty could inform 

policy decisions. For example, changes in ecosystem carbon 

stocks due to woody encroachment on grasslands constitute 

one of the largest, but least certain, aspects of terrestrial carbon cycling in North America (Houghton et al., 1999; Pacala 

et al., 2001). Better information about the spatial extent of 

woody encroachment, the amount and growth of woody 

biomass, and variation in the impacts on soil carbon stocks 

would help reduce that uncertainty. Identifying location, 

cause, and size of this sink could help identify practices that 

may promote continued sequestration of carbon and would 

constrain estimates of carbon storage in other lands, possibly 

helping to identify other policy options. Uncertainty in land 

use, land-use change, soil carbon responses to management 

(e.g., tillage) on particular soils, and impacts of cultivation 

on soil carbon stocks (e.g., impacts of erosion) are the largest contributors to uncertainty in the Canadian and United 

States’ national agricultural greenhouse gas inventories 

(Ogle et al., 2003; VandenBygaart et al., 2003). Finally, if 

the goal of a policy instrument is to reduce greenhouse gas 

emissions, net impacts on CO2, CH4, and N2O emissions, 

which are not as well understood, should be considered.

When mineral soil nitrogen content is increased by 

nitrogen additions (i.e., fertilizer), a portion of that 

nitrogen can be transformed to N2O as a byproduct 

of two microbiological processes (nitrification and denitrification) and lost to the atmosphere. Coincidental 

introduction of large amounts of easily decomposable 

organic matter and NO3ˉ from either a plow down 

of cover crop or manure addition greatly stimulates 

denitrification under wet conditions (Peoples et al., 

2004). Some practices intended to sequester atmospheric carbon in soil could prompt increases in N2O 

fluxes. For example, reducing tillage intensity tends 

to increase soil moisture, leading to increased N2O 

fluxes, particularly in wetter environments (Six et al., 

2004). Synchronizing organic amendment applications 

with plant nitrogen uptake and minimizing manure 

storage under anoxic conditions can reduce N2O 

emissions by 10–25% and will increase nitrogen use 

efficiency which can decrease indirect emissions (in 

waterways) by 5–20% (CAST, 2004).

BOX 10.4: Agricultural and

Grazing Land N2O Emission Reductions 
The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

North American Forests

CHAPTER

11

117

Lead Authors: Richard A. Birdsey, USDA Forest Service; Jennifer C. 

Jenkins, Univ. Vt.; Mark Johnston, Saskatchewan Research Council; Elisabeth Huber-Sannwald, Instituto Potosino de Investigación Científica y 

Tecnológica

Contributing Authors: Brian Amiro, Univ. Manitoba; Ben de Jong, 

ECOSUR; Jorge D. Etchevers Barra, Colegio de Postgraduado; Nancy 

French, Altarum Inst.; Felipe García-Oliva, UNAM; Mark Harmon, 

Oreg. State Univ.; Linda S. Heath, USDA Forest Service; Victor J. 

Jaramillo, UNAM; Kurt Johnsen, USDA Forest Service; Beverly E. Law, 

Oreg. State Univ.; Erika Marín-Spiotta, Univ. Calif. Berkeley; Omar 

Masera, UNAM; Ronald Neilson, USDA Forest Service; Yude Pan, 

USDA Forest Service; Kurt S. Pregitzer, Mich. Tech. Univ.

KEY FINDINGS

North American forests contain roughly 170 ± 40 billion tons of carbon, of which approximately 28% is in live 

vegetation and 72% is in dead organic matter.

North American forests were a net carbon sink of -270 ± 130 million tons of carbon per year over the last 10 to 

15 years.

Deforestation continues in Mexico where forests are a source of carbon dioxide to the atmosphere. Forests of the 

United States and parts of Canada have become a carbon sink as a consequence of the recovery of forests following 

the abandonment of agricultural land.

Carbon dioxide emissions from Canada’s forests are highly variable because of interannual changes in area burned 

by wildfire.

The size of the carbon sink in United States’ forests appears to be declining based on inventory data from 1952 to 

the present.

Many factors that cause changes in carbon stocks of forests have been identified, including land-use change, timber 

harvesting, natural disturbance, increasing atmospheric carbon dioxide, climate change, nitrogen deposition, and 

ozone in the lower atmosphere. There is a lack of consensus about how these different natural and human-caused 

factors contribute to the current sink, and the relative importance of factors varies geographically.

There have been several continental- to sub continental-scale assessments of future changes in carbon and vegetation distribution in North America, but the resulting projections of future trends for North American forests are 

highly uncertain. Some of this is due to uncertainty in future climate, but there is also considerable uncertainty in 

forest response to climate change and in the interaction of climate with other natural and human-caused factors.

Forest management strategies can be adapted to manipulate the carbon sink strength of forest systems. The net 

effect of these management strategies will depend on the 

area of forests under management, management objectives 

for resources other than carbon, and the type of disturbance 

regime being considered.

Decisions concerning carbon storage in North American 

forests and their management as carbon sources and sinks 

will be significantly improved by (1) filling gaps in inventories 

of carbon pools and fluxes, (2) a better understanding of how 

management practices affect carbon in forests, (3) a better 

estimate of potential changes in forest carbon under climate 

change and other factors, and (4) the increased availability of 

decision support tools for carbon management in forests.

•

•

•

•

•

•

•

•

•
The U.S. Climate Change Science Program Chapter 11

118 

11.1 

INTRODUCTION

The forest area of North 

America totals 771 million hectares (ha), 36% 

of the land area of North 

America and about 20% 

of the world’s forest area 

(Food and Agriculture 

Organization, 2001)† (see 

Table 11.1 and Box 11.1 for 

estimates and uncertainty 

conventions, respectively). About 45% of this forest area is 

classified as boreal, mostly in Canada and some in Alaska. 

Temperate and tropical forests constitute the remainder of 

the forest area.

North American forests are critical components of the global 

carbon cycle, exchanging large amounts of carbon dioxide 

(CO2) and other gases with the atmosphere and oceans. In 

this chapter, we present the most recent estimates of the role 

of forests in the North American carbon balance, describe 

the main factors that affect forest carbon stocks and fluxes, 

describe how forests affect the carbon cycle through CO2

sequestration and emissions, and discuss management options and research needs.

11.2 CARBON STOCKS AND FLUXES

11.2.1 Ecosystem Carbon Stocks and Pools

North American forests contain more than 170 billion tons 

of carbon (Gt C), of which 28% is in live biomass and 72% 

is in dead organic matter (Table 11.2). Among the three 

countries, Canada’s forests contain the most carbon and 

Mexico’s forests the least.

Carbon density (the amount of carbon stored per unit of land 

area) is highly variable. In Canada, the majority of carbon 

storage occurs in boreal and cordilleran forests (Kurz and 

Apps, 1999). In the United States, forests of the Northeast, 

Upper Midwest, Pacific Coast, and Alaska (with 14 Gt C) 

store the most carbon. In Mexico, temperate forests contain 

4.5 Gt C, tropical forests contain 4.1 Gt C, and semiarid 

forests contain 5.0 Gt C. 

11.2.2 Net North American Forest Carbon Fluxes

According to nearly all published studies, North American 

lands are a net carbon sink (Pacala et al., 2001). A summary 

of currently available data from greenhouse gas inventories 

and other sources suggests that the magnitude of the North 

American forest carbon sink was approximately -269 million 

metric tons of carbon (Mt C) per year over the last decade 

or so, with United States’ forests accounting for most of the 

sink (Table 11.3). This estimate is likely to be within 50% 

of the true value.

Canadian forests were estimated to be a net sink of -17 Mt 

C per year from 1990-2004 (Environment Canada, 2006) 

(Table 11.3). These estimates pertain to the area of forest 

considered to be “managed” under international reporting guidelines, which is 83% of the total area of Canada’s 

forests. The estimates also include the carbon changes that 

result from land-use change. Changes in forest soil carbon 

are included; urban forests are excluded (Chapter 14 this 

report). High interannual variability is averaged into this 

estimate—the annual change varied from approximately -50 

to +40 between 1990 and 2004. Years with net emissions 

were generally years with high forest fire 

activity (Environment Canada, 2005) 

(Figure 11.1).

Most of the net sink in United States’ 

forests is in aboveground carbon pools, 

which account for -146 Mt C per year 

(Smith and Heath, 2005). The net sink 

for the below-ground carbon pool is estimated at -90 Mt C (Pacala et al., 2001) 

(Table 11.3). The size of the carbon sink 

in United States’ forest ecosystems appears to have declined slightly over the 

last decade (Smith and Heath, 2005). In 

Ecological zone: Canadab U.S.c Mexicod Total

Tropical/subtropical 0***** 115,200***** 30,700***** 145,900*****

Temperate 101,100***** 142,400***** 32,900***** 276,400*****

Boreal 303,000***** 45,500***** 0***** 348,500*****

Total 404,100***** 303,100***** 63,600***** 770,800*****

a The certainty for estimates in this table are listed in Box 11.1. See sources for estimates 

(e.g., see Bechtold and Patterson, 2005 for the United States). b Canadian Forest Service (2005)

c Smith et al. (2004) d Palacio-Prieto et al. (2000)

Table 11.1 Area of forest land by biome and country, 2000 (1000 ha)a. See 

Box 11.1 for uncertainty conventions.

BOX 11.1: CCSP SAP 2.2 Uncertainty Conventions

***** = 95% certain that the actual value is within 10% of the estimate reported, 

  = 95% certain that the estimate is within 25%, 

** * = 95% certain that the estimate is within 50%, 

** = 95% certain that the estimate is within 100%, and

* = uncertainty greater than 100%.

† = The magnitude and/or range of uncertainty for the given numerical 

 value(s) is not provided in the references cited.
119

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

contrast, a steady or increasing supply of timber products 

now and in the foreseeable future (Haynes, 2003) means 

that the rate of increase in the wood products carbon pool 

is likely to remain steady.

For Mexico, the most comprehensive available estimate for 

the forest sector suggests a source of +52 Mt C per year in 

the 1990s (Masera et al., 1997) (Table 11.3). This estimate 

does not include changes in the wood products carbon pool. 

The main cause of the estimated source is deforestation, 

which is offset to a much lesser degree by restoration and 

recovery of degraded forestland.

Landscape-scale estimates of ecosystem carbon fluxes reflect the dynamics of individual forest stands that respond 

to unique combinations of disturbance history, management 

intensity, vegetation, and site characteristics. Extensive landbased measurements of forest/atmosphere carbon exchange 

for forest stands at various stages 

of recovery after disturbance reveal patterns and causes of sink or 

source strength, which is highly 

dependent on time since disturbance. Representative estimates 

for North America are summarized 

in Appendix D. As forests are 

planted or regrow on abandoned 

farmland, or as they recover from 

fire, harvest, or other disturbance, 

there is an initial period of slow 

(or negative) carbon sequestration 

followed by a period of rapid carbon sequestration. Many forests 

continue sequestering significant 

amounts of carbon for 125 years 

or more after establishment (Smith 

et al., 2006). Eventually, the rate 

of sequestration slows as forests 

reach a new balance of carbon 

uptake and release, and in old 

growth forests processes of carbon 

uptake are very nearly balanced 

by processes of release (Chapter 

3, this report).

11.3 TRENDS AND 

DRIVERS

11.3.1 Overview of Trends 

and Drivers of Change 

in Carbon Stocks

Many factors that cause changes in 

carbon stocks of forests and wood 

products have been identified, but 

the relative importance of each remains difficult to quantify (Barford et al., 2001; Caspersen et al., 2000; Goodale 

et al., 2002; Körner, 2000; Schimel et al., 2000). Land-use 

Figure 11.1 Average and annual estimates of change in carbon stocks for forest ecosystems 

of Canada, 1990-2004. Interannual variability is high because of changes in rates and impacts 

of disturbances such as fire and insects (from Environment Canada, 2006).

Ecosystem carbon pool: Canadab U.S.c Mexicod Total

Biomass 14,500**** 24,900  7,700** ** 47,100 

Dead organic mattere 71,300** ** 41,700  11,400** ** 124,400 

Total 85,800** ** 66,600  19,100** ** 171,500 

a The certainty for estimates in this table are listed in Box 11.1. See sources for estimates (Heath 

and Smith, 2000; Smith and Heath, 2000). The estimated carbon stock in North American 

forests is thus 171,500 ± 43,000 Mt C.

b Kurz and Apps (1999)

c Heath and Smith (2004), Birdsey and Heath (1995)

d Masera et al. (2001) e Includes litter, coarse woody debris, and soil carbon.

Table 11.2 Carbon stocks in forests by ecosystem carbon pool and country 

(Mt C)a. See Box 11.1 for uncertainty conventions.

a Data for 1990-2004, taken from Environment Canada (2006), 

Goodale et al. (2002). b From Smith and Heath (2005) (excluding soils), and Pacala et al. (2001) 

(soils). Estimates do not include urban forests.

c From Masera (1997)

d Estimates are not available. 

Table 11.3 Change in carbon stocks for forests and wood 

products by country (Mt C per year). See Box 11.1 for 

uncertainty conventions.

Carbon pool: Canadaa U.S.b Mexicoc Total

Forest ecosystem –17**  –236*** +52** –201

Wood products –11** –57*** NDd –68

Total –28** –293*** +52** –269
The U.S. Climate Change Science Program Chapter 11

120 

change, timber harvesting, natural disturbance, increasing 

atmospheric CO2, climate change, nitrogen deposition, and 

tropospheric ozone all have effects on carbon stocks in forests, with their relative influence depending on geographic 

location, the type of forest, and specific site factors. It is 

important for policy implementation and management of 

forest carbon to separate the effects of direct human actions 

from natural factors.

The natural and human-caused (anthropogenic) factors that 

significantly influence forest carbon stocks are different for 

each country, and still debated in the scientific literature. 

Natural disturbances are significant in Canada, but estimates 

of the relative effects of different kinds of disturbance are 

uncertain. One study estimated that impacts of wildfire 

and insects caused emissions of about +40 Mt C per year†

of carbon to the atmosphere over the two decades (Kurz 

and Apps, 1999). Another study concluded that the positive 

effects of climate, CO2, and nitrogen deposition outweighed 

the effects of wildfire 

and insects, making 

Canada’s forests a net 

carbon sink in the same 

period (Chen et al., 

2003). In the United 

States, land-use change 

and timber harvesting seem to be dominant factors according to repeated forest inventories from 1952 to 1997 that 

show forest carbon stocks (excluding soils) increasing by 

about 175 Mt C per year. The most recent inventories show 

a decline in the rate of carbon uptake by forests, which appears to be mainly the result of changing growth and harvest rates following a long history of land-use change and 

management (Birdsey et al., 2006; Smith and Heath, 2005). 

The factors behind net emissions from Mexico’s forests are 

deforestation, forest degradation, and forest fires that are 

not fully offset by forest regeneration (Masera et al., 1997; 

De Jong et al., 2000).

11.3.2 Effects of Land-use Change

Since 1990, approximately 549,000 ha of former cropland or 

grassland in Canada have been abandoned and are reverting to forest, while 71,000 ha of forest have been converted 

to cropland, grassland, or settlements, for a net increase in 

forest area of 478,000 ha (Environment Canada, 2005)†

. In 

2004, approximately 25,000 ha were converted from forest 

to cropland, 19,000 ha from forest to settlements, and approximately 3,000 ha converted to wetlands. These land-use 

changes resulted in emissions of about 4 Mt C (Environment 

Canada, 2005)†.

In the last century more than 130 million ha of land in the 

conterminous United States were either afforested (62 million ha) †

 or deforested (70 million ha)† (Birdsey and Lewis, 

2003). Houghton et al. (1999) estimated that cumulative 

changes in forest carbon stocks for the period from 1700 to 

1990 in the United States were about +25 Gt C,† primarily 

from conversion of forestland to agricultural use and reduction of carbon stocks for wood products. 

Emissions from Mexican forests to the atmosphere are 

primarily due to the impacts of deforestation to pasture and 

degradation of 720,000 to 880,000 ha per year† (Masera et 

al., 1997; Palacio-Prieto et al., 2000). The highest deforestation rates occur in the tropical deciduous forests (304,000 

ha in 1990)† and the lowest in temperate 

broadleaf forests (59,000 ha in 1990)†.

11.3.3 Effects of Forest Management

The direct human impact on North 

American forests ranges from very minimal for protected areas to very intense 

for plantations (Table 11.4). Between 

these extremes is the vast majority of 

forestland, which is impacted by a wide 

range of human activities and government policies that influence harvesting, 

wood products, and regeneration.

Management 

class: Canada U.S. Mexico Total

Protected 19,300***** 66,700***** 6,000***** 92,000*****

Plantation 4,500***** 16,200***** 200***** 20,900*****

Other 380,300***** 220,200***** 57,400***** 657,900*****

Total 404,100***** 303,100***** 63,600***** 770,800*****

Table 11.4 Area of forestland by management class and country, 

2000 (1000 ha)a. See Box 11.1 for uncertainty conventions.

a

From Food and Agriculture Organization (2001), Natural Resources 

Canada (2005). The certainty for estimates in this table are listed in Box 

11.1. See sources for estimates (e.g., for the United States, see Bechtold 

and Patterson, 2005). 

The most recent inventories for 

the U.S. show a decline in the 

rate of carbon uptake by forests.
121

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

Forests and other wooded land in Canada occupy about 

402 million ha. Approximately 310 million ha is considered 

forest of which 255 million ha (83%) are under active forest 

management (Environment Canada, 2005)†.Managed forests 

are considered to be under the direct influence of human 

activity and not reserved. Less than 1% of the area under 

active management is harvested annually. Apps et al. (1999) 

used a carbon budget model to simulate carbon in harvested 

wood products (HWP) for Canada. Approximately 800 Mt C 

were stored in the Canadian HWP sector in 1989, of which 

50 Mt C were in imported wood products, 550 Mt C in exported products, and 200 Mt C in wood products produced 

and consumed domestically†.

Between 1990 and 2000, about 4 million ha per year were 

harvested in the United States, two-thirds by partial-cut 

harvest and one-third by clear-cut (Birdsey and Lewis, 

2003). Between 1987 and 1997, about 1 million ha per year 

were planted with trees, and about 800,000 ha were treated 

to improve the quality and/or quantity of timber produced 

(Birdsey and Lewis, 2003). Harvesting in United States’ 

forests accounts for substantially more tree mortality than 

natural causes such as wildfire and insect outbreaks (Smith 

et al., 2004). The harvested wood resulted in -57 Mt C added 

to landfills and products in use, and an additional 88 Mt C 

were emitted from harvested wood burned for energy (Skog 

and Nicholson, 1998) †.

About 80% of the forested area in Mexico is socially owned 

by communal land grants (ejidos) and rural communities. 

About 95% of timber harvesting occurs in native temperate 

forests (SEMARNAP, 1996). Illegal harvesting involves 13.3 

million cubic meters of wood every year (Torres, 2004). 

The rural population is the controlling factor for changes 

in carbon stocks from wildfire, wood extraction, shifting 

agriculture practices, and conversion of land to crop and 

pasture use.

11.3.4 Effects of Climate and 

Atmospheric Chemistry

Environmental factors, including climate variability, nitrogen deposition, tropospheric ozone, and elevated CO2, have 

been recognized as significant factors affecting the carbon 

cycle of forests (Aber et al., 2001; Ollinger et al., 2002). 

Some studies indicate that these effects are significantly 

smaller than the effects of land management and landuse change (Caspersen et al., 2000; Schimel et al., 2000). 

Recent reviews of ecosystem-scale studies known as Free 

Air CO2 Exchange (FACE) experiments suggest that rising 

CO2 increases net primary productivity by 12-23% over all 

species studied (Norby et al., 2005; Nowak et al., 2004). 

However, it is uncertain whether this effect results in a lasting increase in sequestered carbon or causes a more rapid 

cycling of carbon between the ecosystem and the atmosphere 

(Körner et al., 2005; Lichter et al., 2005). Experiments have 

also shown that the effects of rising CO2 are significantly 

moderated by increasing tropospheric ozone (Karnosky et 

al., 2003; Loya et al., 2003). When nitrogen availability is 

also considered, reduced soil fertility limits the response to 

rising CO2, but nitrogen deposition can increase soil fertility 

to counteract that effect (Finzi et al., 2006; Johnson et al., 

1998; Oren et al., 2001). Observations of photosynthetic activity from satellites suggest that productivity changes due to 

lengthening of the growing season depend on whether areas 

were disturbed by fire (Goetz et al., 2005). Based on these 

conflicting and complicated results from different studies and approaches, a definitive assessment of the relative 

importance, and interactions, of natural and anthropogenic 

factors is a high priority for research (U.S. Climate Change 

Science Program, 2003).

11.3.5 Effects of Natural Disturbances

Wildfire, insects, diseases, and weather events are common 

natural disturbances in North America. These factors impact 

all forests but differ in magnitude by geographic region. 

Wildfires were the largest disturbance in the twentieth century in Canada (Weber and Flannigan, 1997). In the 1980s 

and 1990s, the average total burned area was 2.6 million ha 

per year in Canada’s forests, with a maximum 7.6 million ha 

per year in 1989†

.Carbon emissions from forest fires range 

from less than +1 Mt C per year in the interior of British 

Columbia to more than +10 Mt C per year in the western 
The U.S. Climate Change Science Program Chapter 11

122 

boreal forest. Total emissions from forest fires 

in Canada averaged approximately +27 Mt C 

per year between 1959 and 1999 (Amiro et al., 

2001)†. Estimated carbon emissions from four 

major insect pests in Canadian forests (spruce 

budworm, jack pine budworm, hemlock looper, 

and mountain pine beetle) varied from +5 to 10 

Mt C per year in the 1970s to less than +2 Mt C 

per year in the mid-1990s1. Much of the Canadian forest is expected to experience increases 

in fire severity (Parisien et al., 2005) and burn 

areas (Flannigan et al., 2005), and continued 

outbreaks of forest pests are also likely (Volney 

and Hirsch, 2005).

In United States’ forests, insects, diseases, and 

wildfire combined, affect more than 30 million 

ha per decade (Birdsey and Lewis, 2003). Damage from weather events (hurricanes, tornadoes, 

and ice storms) may exceed 20 million ha per decade (Dale 

et al., 2001). Although forest inventory data reveal the extent 

of tree mortality attributed to all causes combined, estimates 

of the impacts of individual categories of natural disturbance 

on carbon pools of temperate forests are scarce. The impacts 

of fire are clearly significant. According to one estimate, 

the average annual carbon emissions from biomass burning 

in the contemporary United States ranges from 9 to 59 Mt 

C (Leenhouts, 1998). McNulty (2002) estimated that large 

hurricanes in the United States could convert 20 Mt C of 

live biomass into detrital carbon pools.

The number and area of 

sites affected by forest 

fires in Mexico have 

fluctuated considerably 

between 1970 and 2002, 

with a clear tendency of 

an increasing number of 

fire events (4,000-7,000 in the 1970s and 1,800-15,000 in the 

1990s), and overall, larger areas are being affected (0.08-

0.25 million ha in the 1970s and 0.05-0.85 million ha in the 

1990s). During El Nino years, increasing drought increases 

fire frequencies (Torres, 2004). Between 1995 and 2000, an 

average of 8,900 fire events occurred per year and affected 

about 327,000 ha of the forested area. Currently, no estimates 

are available on the contribution of these fires to CO2 emissions. Pests and diseases are important natural disturbance 

agents in temperate forests of Mexico; however, no statistics 

exist on the extent of the affected land area.

1 These estimates are the product of regional carbon density values, 

the proportion of mortality in defoliated stands given in Kurz and 

Apps (1999), data on area affected taken from NFDP (2005), and 

the proportion of carbon in insect-killed stands that is emitted 

directly to the atmosphere (0.1) from the disturbance matrix for 

insects used in the CBM-CFS (Kurz et al., 1992).

11.3.6 Projections of Future Trends

11.3.6.1 Canada

Large portions of the Canadian and Alaskan forest are expected to be particularly sensitive to climate change (Hogg 

and Bernier, 2005). Climate change effects on forest growth 

could be positive (e.g., increased rates of photosynthesis 

and increased water use efficiency) or negative (decreased 

water availability, higher rates of respiration) (Baldocchi 

and Amthor, 2001). It is difficult to predict the direction 

of these changes and they will likely vary by species and 

local conditions of soils and topography (Johnston and Williamson, 2005). Because of the large area of boreal forests 

and expected high degree of warming in northern latitudes, 

Canada and Alaska require close monitoring over the next 

few decades as these areas will likely be critical to determining the carbon balance of North America.

11.3.6.2 United States

Assessments of future changes in carbon and vegetation 

distribution in the United States suggest that under most 

future climate conditions, net primary production (NPP) 

would respond positively to changing climate but total 

carbon storage would remain relatively constant (VEMAP 

Members, 1995; Pan et al., 1998; Neilson et al., 1998; Joyce 

et al., 2001). Some climate scenarios indicate that much of 

the Northwest U.S. will receive more annual precipitation. 

When coupled with higher CO2 and longer growing seasons, 

simulations show woody expansion and increased sequestration of carbon as well as increases in fire (Bachelet et al., 

2001). However, recent scenarios from the Hadley climate 

model show drying in the Northwest, which produces some 

forest decline (Price et al., 2004). Many simulations show 

continued growth in eastern forests through the end of the 

twenty-first century, but some show the opposite, especially 

in the Southeast. Eastern forests could experience a period 

of enhanced growth in the early stages of warming, due to 

elevated CO2, increased precipitation, and a longer growing 

Large portions of the Canadian 

and Alaskan forest are 

expected to be particularly 

sensitive to climate change.
123

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

season. However, further warming could bring on increasing 

drought stress, reducing the carrying capacity of the ecosystem and causing carbon losses through drought-induced 

dieback and increased fire and insect disturbances. North 

American boreal forests are of particular concern due to 

substantial increases in fire activity projected under most 

future climate scenarios (Flannigan et al., 2005).

11.3.6.3 Mexico

For Mexican forests, deforestation will continue to cause 

large carbon emissions in the years to come. However, government programs (since 2001) are trying to reduce deforestation rates and forest degradation, implement sustainable 

forestry in native forests, promote commercial plantations 

and diverse agroforestry systems, and promote afforestation 

and protection of natural areas (Masera et al., 1997).

11.4 OPTIONS FOR MANAGEMENT

Forest management strategies can be adapted to increase 

the amount of carbon uptake by forest systems. Alternative 

strategies for wood products are also important in several 

ways: how long carbon is retained in use, how much wood is 

used for biofuel, and substitution of wood for other materials that use more energy to produce. The net effect of these 

management and production strategies on carbon stocks and 

emissions will depend on emerging government policies 

for greenhouse gas management, the area of forests under 

management, management objectives for resources other 

than carbon, and the type of management and production 

regime being considered.

The forest sector includes a variety of activities that can 

contribute to increasing carbon sequestration, including: 

afforestation, mine land reclamation, forest restoration, 

agroforestry, forest management, biomass energy, forest 

preservation, wood products management, and urban forestry (Birdsey et al., 2000). Although the science of managing forests specifically for carbon sequestration is not well 

developed, some ecological principles are emerging to guide 

management decisions (Appendix E). The prospective role of 

forestry in helping to stabilize atmospheric CO2 depends 

on government policy, harvesting and disturbance rates, 

expectations of future forest productivity, the fate and 

longevity of forest products, and the ability to deploy 

technology and forest practices to increase the retention 

of sequestered CO2. Market factors are also important 

in guiding the behavior of the private sector.

For Canada, Price et al. (1997) examined the effects 

of reducing natural disturbance, manipulating stand 

density, and changing rotation lengths for a forested 

landscape in northwest Alberta. By replacing natural 

disturbance (fire) with a simulated harvesting regime, 

they found that long-term equilibrium carbon storage 

increased from 105 to 130 Mt C. Controlling stand density 

following harvest had minimal impacts in the short term 

but increased landscape-level carbon storage by 13% after 

150 years. Kurz et al. (1998) investigated the impacts on 

landscape-level carbon storage of the transition from natural 

to managed disturbance regimes. For a boreal landscape in 

northern Quebec, a simulated fire disturbance interval of 

120 yr was replaced by a harvest cycle of 120 yr. The net 

impact was that the average age of forests in the landscape 

declined from 110 yr to 70 yr, and total carbon storage in 

forests declined from 16.3 to 14.8 Mt C (including both 

ecosystem and forest products pools).

Market approaches and 

incentive programs to 

manage greenhouse 

gases, particularly CO2, 

are under development 

in the United States, the 

European Union, and 

elsewhere (Totten, 1999). Since forestry activities have highly variable costs because of site productivity and operational 

variability, most recent studies of forestry potential develop 

“cost curves”, i.e., estimates of how much carbon will be sequestered by a given activity for various carbon prices (value 

in a market system) or payments (in an incentive system). 

There is also a temporal dimension to the analyses because 

the rate of change in forest carbon stocks is variable over 

time, with forestry activities tending to have a high initial 

rate of net carbon sequestration followed by a lower or even 

a negative rate as forests reach advanced age. 

In the United States, a bundle of forestry activities could 

potentially increase carbon sequestration from -100 to -200 

Mt C per year according to several studies (Birdsey et al., 

2000; Lewandrowski et al., 2004; Environmental Protection Agency, 2005; Stavins and Richards, 2005). The rate 

of annual mitigation would likely decline over time as 

low-cost forestry opportunities become scarcer, forestry 

sinks become saturated, and timber harvesting takes place. 

Substantial increases in fire 

activity for North American 

boreal forests are projected under 

most future climate scenarios.
The U.S. Climate Change Science Program Chapter 11

124 

Economic analyses of the U.S. forestry potential have focused on three broad categories of activities: afforestation 

(conversion of agricultural land to forest), improved management of existing forests, and use of woody biomass for 

fuel. Improved management of existing forest lands may 

be attractive to landowners at carbon prices below $10 per 

ton of CO2; afforestation requires a moderate price of $15 

per ton of CO2 or more to induce landowners to participate; 

and biofuels become dominant at prices of $30-50 per ton 

of CO2 (Lewandrowski et al., 2004; Stavins and Richards, 

2005; Environmental Protection Agency, 2005). Table 11.5 

shows a simple scenario of emissions reduction below 

baseline, annualized over the time period 2010-2110, for 

forestry activities as part of a bundle of reduction options 

for the land base.

Production of renewable materials that have lower lifecycle emissions of greenhouse gases than non-renewable 

alternatives is a promising strategy for reducing emissions. 

Lippke et al. (2004) found that wood components used in 

residential construction had 

lower emissions of CO2 from 

energy inputs than either concrete or steel.

Co-benefits are vitally important for inducing good 

forest carbon management. 

For example, conversion of 

agricultural land to forest 

will generally have positive 

effects on water, air, and soil 

quality and on biodiversity. 

In practice, some forest carbon sequestration projects have 

already been initiated even though sequestered carbon has 

little current value (Winrock International, 2005). In many 

of the current projects, carbon is a secondary objective that 

supports other landowner interests, such as restoration of 

degraded habitat. But co-effects may not all be beneficial. 

Water quantity may decline because of increased transpiration by trees relative to other vegetation. And taking land 

out of crop production may affect food prices—at higher 

carbon prices, nearly 40 million ha may be converted from 

cropland to forest (Environmental Protection Agency, 2005). 

Implementation of a forest carbon management policy will 

need to carefully consider co-effects, both positive and 

negative.

11.5 DATA GAPS AND INFORMATION 

NEEDS FOR DECISION SUPPORT

Decisions concerning carbon storage in North American 

forests and their management as carbon sources and sinks 

will be significantly improved by (1) filling gaps in inventories of carbon pools and fluxes, (2) a better 

understanding of how management practices 

affect carbon in forests, and (3) the increased 

availability of decision support tools for carbon management in forests.

11.5.1 Major Data Gaps in Estimates of Carbon Pools and Fluxes

Effective carbon policy and management to 

increase carbon sequestration and/or reduce 

emissions requires thorough understanding of 

current carbon stock sizes and flux rates, and 

responses to disturbance. Data gaps complicate analyses of the potential for policies to 

influence natural, social, and economic drivers that can change carbon stocks and fluxes. 

Forests in an area as large as North America 

are quite diverse, and comprehensive data sets 

that can be used to analyze forestry opportunities, such as spatially explicit historical 

a Adapted from Environmental Protection Agency (2005). Maximum price analyzed was 

$50/t CO2.

Forestry 

activity

Carbon sequestration 

rate (t CO2 per ha 

per year)

Price range 

($/t CO2)

Emissions reduction 

potential 

(Mt CO2 per year)

Afforestation 5.4–23.5 15–30 137–823

Forest 

management

5.2–7.7 1–30 25–314

Biofuels 11.8–13.6 30–50 375–561

Table 11.5 Illustrative emissions reduction potential of various forestry activities in 

the United States under a range of prices and sequestration ratesa.
125

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

management and disturbance rates and effects on the carbon 

cycle, would enable managers to change forest carbon stocks 

and fluxes. Although this report provides aggregate statistics 

on forest carbon by biome and country, users could benefit 

from spatially explicit estimates of forest carbon. Such an 

analysis might involve matching estimates based on forest 

inventories as presented by political unit and general forest 

type (Birdsey and Lewis, 2003) with data developed using 

remote sensing techniques (Running et al., 2004). Research 

at the level of individual sites has proven the feasibility of 

this combination (e.g., Van Tuyl et al., 2005; Turner et al., 

2006). This kind of analysis could facilitate development of 

a forest carbon map for North America.

In the United States, the range of estimates of the size of the 

land carbon sink is between -0.30 and -0.58 Mt C per year 

(Pacala et al., 2001). Significant data gaps among carbon 

pools include carbon in wood products, soils, woody debris, 

and water transport (Birdsey, 2004; Pacala et al., 2001). 

Geographic areas that are poorly represented in the available data sets include much of the Intermountain Western 

United States and Alaska, where forests of low productivity 

have not been inventoried as intensively as more productive timberlands (Birdsey, 2004). Accurate quantification 

of the relative magnitude of various causal mechanisms at 

large spatial scales is not yet possible, although research 

is ongoing to combine various approaches and data sets: 

large-scale observations, process-based modeling, ecosystem experiments, and laboratory investigations (Foley and 

Ramankutty, 2004).

Data gaps exist for Canada, particularly regarding changes 

in forest soil carbon and forest lands that are considered 

“unmanaged” (17% of forest lands). Aboveground biomass 

is better represented in forest inventories; however, the information needs to be updated and made more consistent among 

provinces. The new Canadian National Forest Inventory, 

currently under way, will provide a uniform 

coverage at a 20 × 20 km grid that will be the 

basis for future forest carbon inventories. Data 

are also lacking on carbon fluxes, particularly 

those due to insect outbreaks and forest stand 

senescence. The ability to model forest carbon 

stock changes has considerably improved with 

the release of the Carbon Budget Model of the 

Canadian Forest Sector (CBM-CFS3)(Kurz et 

al., 2002); however, the CBM-CFS3 was not 

designed to incorporate climate change impacts 

(Price et al., 1999; Hogg and Bernier, 2005).

For Mexico, there is very little data about 

measured carbon stocks for all forest types. 

Information on forest ecosystem carbon fluxes 

is primarily based on deforestation rates, while 

fundamental knowledge of carbon exchange processes in 

almost all forest ecosystems is missing. That information is 

essential for understanding the effects of both natural and 

human-induced drivers (hurricanes, fires, insect outbreaks, 

climate change, migration, and forest management strategies), which all strongly impact the forest carbon cycle. Current carbon estimates are derived from studies in preferred 

sites in natural reserves with species-rich tropical forests. 

Therefore, inferences made from the studies on regional 

and national carbon stocks and fluxes probably give biased 

estimates on the carbon cycle.

11.5.2 Major Data Gaps in 

Knowledge of Forest Management Effects

There is insufficient information available to guide land 

managers in specific situations to change forest management practices to increase carbon sequestration, and there is 

some uncertainty about the longevity of effects (Caldeira et 

al., 2004). This reflects a gap in the availability of inexpensive techniques for measuring, monitoring, and predicting 

changes in ecosystem carbon pools at the smaller scales appropriate for managers. There is more information available 

about management effects on live biomass and woody debris, 

and less about effects on soils and wood products. This 

imbalance in data has the potential to produce unintended 

consequences if predicted results are based on incomplete 

carbon accounting.

In the tropics, agroforestry systems offer a promising economic alternative to slash-and-burn agriculture, including 

highly effective soil conservation practices and mid-term 

and long-term carbon mitigation options (Soto-Pinto et al., 

2001; Nelson and de Jong, 2003; Albrecht and Kandji, 2003). 

However, a detailed assessment of current implementations 

of agroforestry systems in different regions of Mexico is 

missing. Agroforestry also has potential in temperate agricultural landscapes, but as with forest management, there 
The U.S. Climate Change Science Program Chapter 11

126 

is a lack of data about how specific systems affect carbon 

storage (Nair and Nair, 2003).

Refining management of forests to realize significant carbon 

sequestration, while at the same time continuing to satisfy 

the needs of forests and the services they provide (e.g., timber harvest, recreational value, watershed management) will 

require a multi-criteria decision support framework for a holistic and adaptive management program of the carbon cycle 

in North American forests. For example, methods should be 

developed for enhancing the efficiency of forest management, increasing the carbon storage per acre from existing 

forests, or even increasing the acreage devoted to forest 

systems that provide carbon sequestration. Currently there 

is little information about how appropriate incentives might 

be applied to accomplish 

these goals effectively, 

but given the importance 

of forests in the global 

carbon cycle, success in 

this endeavor could have 

important long-term and 

large-scale effects on 

global atmospheric carbon stocks.

11.5.3 Availability of Decision Support Tools

Few decision support tools for land managers that include 

complete carbon accounting are available; one example is 

the CBM-CFS3 carbon accounting model (Kurz et al., 2002). 

Some are in development or have been used primarily in 

research studies (Proctor et al., 2005; Potter et al., 2003). As 

markets emerge for trading carbon credits, and if credits for 

forest management activities have value in those markets, 

then the demand for decision support tools will encourage 

their development.

Given the importance of 

forests in the global carbon 

cycle, success in enhancing 

the efficiency of forests as a 

renewable energy source could 

have important long-term and 

large-scale effects on global 

atmospheric carbon stocks.
The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

Carbon Cycles in the Permafrost Region 

of North America

CHAPTER

12

127

Lead Author: Charles Tarnocai, Agriculture and Agri-Food Canada

Contributing Authors: Chien-Lu Ping, Univ. Alaska; John Kimble, 

USDA NRCS (retired)

KEY FINDINGS

Much of northern North America (more than 6 million square kilometers) is characterized by the presence of 

permafrost (soils or rocks that remain frozen for at least two consecutive years). This permafrost region contains 

approximately 25% of the world’s total soil organic carbon, a massive pool of carbon that is vulnerable to release 

to the atmosphere as carbon dioxide in response to an already detectable polar warming.

The soils of the permafrost region of North America contain 213 billion tons of organic carbon, approximately 61% 

of the carbon in all soils of North America.

The soils of the permafrost region of North America are currently a net sink of approximately 11 million tons of 

carbon per year.

The soils of the permafrost region of North America have been slowly accumulating carbon for the last 5000–8000 

years. More recently, increased human activity in the region has resulted in permafrost degradation and at least 

localized loss of soil carbon.

Patterns of climate, especially the region’s cool and cold temperatures and their interaction with soil hydrology 

to produce wet and frozen soils, are primarily responsible for the historical accumulation of carbon in the region. 

Non-climatic drivers of carbon change include human activities, including flooding associated with hydroelectric 

development, that degrade permafrost and lead to carbon loss. Fires, increasingly common in the region, also lead 

to carbon loss.

Projections of future warming of the polar regions of North America lead 

to projections of carbon loss from the soils of the permafrost region, 

with upwards of 78% (34 billion tons) and 41% (40 billion tons) of carbon 

stored in soils of the Subarctic and northern-most coniferous (Boreal) 

regions, respectively, being severely or extremely severely affected by 

future climate change.

Options for management of carbon in the permafrost region of North 

America, including construction methods that cause as little disturbance 

of the permafrost and surface as possible, are primarily those which avoid 

permafrost degradation and subsequent carbon losses.

Most research needs for the permafrost region are focused on reducing 

uncertainties in knowing how much carbon is vulnerable to a warming 

climate and how sensitive that carbon loss is to climate change. Development and adoption of measures that reduce or avoid the negative impact 

of human activities on permafrost are also needed. 

•

•

•

•

•

•

•

•
The U.S. Climate Change Science Program Chapter 12

128 

12.1 INTRODUCTION

It is especially important to understand the carbon cycle in 

the permafrost region of North America because the soils 

in this area contain large amounts of organic carbon that is 

vulnerable to release to the atmosphere as carbon dioxide 

(CO2) and methane (CH4) in response to climate warming. 

It is predicted that the average annual air temperature in the 

permafrost region will increase 3–4°C by 2020 and 5–10°C 

by 2050 (Hengeveld, 2000, see Box 12.1)†. The soils in this 

region contain approximately 61%*** of the organic carbon 

occurring in all soils in North America (Lacelle et al., 2000) 

even though the permafrost area covers only about 21%***

of the soil area of the continent. Release of even a fraction 

of this carbon in greenhouse gases could have global consequences.

Permafrost is defined, on the basis of temperature, as soils 

or rocks that remain below 0oC for at least two consecutive 

years (van Everdingen, 1998 revised May 2005). Permafrost terrain often contains large quantities 

of ground ice in the 

upper section of the 

permafrost. If this terrain is well protected 

by forests or peat, this 

ground ice is generally 

in equilibrium with 

the current climate. If this insulating layer is not sufficient, 

however, even small temperature changes, especially in 

the southern part of the permafrost region, could cause 

degradation and result in severe thermal erosion (thawing). 

For example, some of the permafrost that formed in central Alaska during the Little Ice Age is now degrading in 

response to warming during the last 150 years (Jorgenson 

et al., 2001).

The permafrost region in North America is divided into four 

zones on the basis of the percentage of the land area underlain by permafrost (Figure 12.1). These zones are the Continuous Permafrost Zone (>90 to 100%), the Discontinuous 

Permafrost Zone (>50 to <90%), the Sporadic Permafrost 

Zone (>10 to <50%), and the Isolated Patches Permafrost 

Zone (0 to <10%) (Brown et al., 1997).

These permafrost zones encompass three major ecoclimatic provinces (ecological regions) (Figure 12.2): the Arctic 

(north of the arctic tree line), the Subarctic (open canopy coniferous forest), and the Boreal (closed canopy forest, either 

Figure 12.1 Permafrost zones in North America (Brown et 

al., 1997).

Figure 12.2 Arctic, Subarctic, and Boreal ecoclimatic provinces 

(ecological regions) in North America (Ecoregions Working 

Group, 1989; Baily and Cushwa, 1981).

Some of the permafrost that 

formed in central Alaska 

during the Little Ice Age is now 

degrading in response to warming 

during the last 150 years. 

BOX 12.1: CCSP SAP 2.2 Uncertainty Conventions

***** = 95% certain that the actual value is within 10% of the estimate reported, 

  = 95% certain that the estimate is within 25%, 

** * = 95% certain that the estimate is within 50%, 

** = 95% certain that the estimate is within 100%, and

* = uncertainty greater than 100%.

† = The magnitude and/or range of uncertainty for the given numerical 

 value(s) is not provided in the references cited.
129

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

coniferous or mixed coniferous and deciduous). Peatlands 

(organic wetlands characterized by more than 40 cm of peat 

accumulation) cover large areas in the Boreal, Subarctic, and 

southern part of the Arctic ecoclimatic provinces.

Although northern ecosystems (Arctic, Subarctic, and Boreal) in North America cover approximately 14% of the global 

land area, they contain approximately 25% of the world’s 

total soil organic carbon (Oechel and Vourlitis, 1994) †. In 

addition, Oechel and Vourlitis (1994) indicate that the tundra 

(Arctic) ecosystems alone contain approximately 12% of the 

global soil carbon pool, even though they account for only 

6% of the total global land area†. Based on direct measure 

of the carbon density to one meter depth, the soil carbon 

pool should be doubled (Michaelson et al., 1996). The soils 

of the permafrost region of North America are currently a 

carbon sink and are unique because they are able to actively 

sequester carbon and store it for thousands of years.

The objectives of this chapter are to give the below-ground 

carbon stocks and to explain the mechanisms associated 

with the carbon cycle (sources and sinks) in the soils of the 

permafrost region of North America.

12.2 PROCESSES AFFECTING THE 

CARBON CYCLE IN A PERMAFROST 

ENVIRONMENT

12.2.1 Soils of the Permafrost Region

Soils cover approximately 6,211,340 square kilometers (km2) *** of the area of the North American permafrost region 

(Tables 12.1 and 12.2), with approximately 58%*** of the 

land area being occupied by permafrost-affected (perennially frozen) soils (Cryosols/Gelisols) and the remainder by 

non-permafrost soils (Soil Carbon Database Working Group, 

1993). Approximately 17%*** of this area is associated with 

organic soils (peatlands), the remainder with mineral soils 

(Soil Carbon Database Working Group, 1993). It is important 

to distinguish between mineral soils and organic soils in the 

region because different processes are responsible for the 

carbon cycle in these two types of soils.

12.2.2 Mineral Soils

The schematic diagram in Figure 12.3 

provides general information about the 

carbon sinks and sources in mineral 

soils. Most of the permafrost-affected 

mineral soils are carbon sinks because 

of the slow decomposition rate due to 

cold and wet conditions and the process 

of cryoturbation, which moves surface 

organic matter into the deeper soil layers. 

Other processes, such as decomposition, 

wildfires, and thermal degradation, 

release carbon into the atmosphere and, 

thus, act as carbon sources.

For unfrozen soils and noncryoturbated 

frozen soils in the permafrost region, the 

carbon cycle is similar to that in soils 

occurring in temperate regions. In these 

soils, organic matter is deposited on the 

soil surface. Some soluble organic matter 

may move downward, but because these 

soils are not affected by cryoturbation, 

they have no mechanism for moving 

organic matter from the surface into 

the deeper soil layers and preserving it 

from decomposition and wildfires. Most 

of their below-ground carbon originates 

from roots and its residence time is relatively short.

The role of cryoturbation: Although 

permafrost-affected ecosystems proPermafrost zones

Area (103

 km2)

Canadaa

AlaskabTotal

Continuous 2001.80 353.46 2355.26

Discontinuous 636.63 479.15 1115.78

Sporadic 717.63 110.98 828.61

Isolated Patches 868.08 0.73 868.81

Total 4224.14 944.32 5168.46

a

Calculated using the Soil Carbon of Canada Database (Soil Carbon Database Working 

Group, 1993).

b

Calculated using the Northern and Mid Latitudes Soil Database (Cryosol Working 

Group, 2001).

Table 12.1 Areas of mineral soils in the various 

permafrost zones.

a

Calculated using the Peatlands of Canada Database (Tarnocai et al., 2005). b

Calculated using the Northern and Mid Latitudes Soil Database (Cryosol Working 

Group, 2001).

Table 12.2 Areas of peatlands (organic soils) in the various 

permafrost zones.

Permafrost zones

Area (103

 km2)

Canadaa

AlaskabTotal

Continuous 176.70 51.31 228.01

Discontinuous 243.51 28.74 272.25

Sporadic 307.72 0.62 308.34

Isolated Patches 221.23 13.05 234.28

 Total 949.16 93.72 1042.88
The U.S. Climate Change Science Program Chapter 12

130 

duce much less biomass than do temperate ecosystems, 

permafrost-affected soils that are subject to cryoturbation 

(frost-churning), a cryogenic process, have a unique ability 

to sequester a portion of this organic matter and store it for 

thousands of years. A number of models have been developed to explain the mechanisms involved in cryoturbation 

(Mackay, 1980; Van Vliet-Lanoë, 1991; Vandenberghe, 

1992). The most recent model involves the process of differential frost heave (heave-subsidence), which produces 

downward and lateral movement of materials (Walker et 

al., 2002; Peterson and Krantz, 2003).

Part of the organic matter produced annually by the vegetation is deposited as litter on the soil surface, with some 

decomposing as a result of biological activity. A large portion 

of this litter, however, builds up 

on the soil surface, forming an 

organic soil horizon. Cryoturbation causes some of this organic 

material to move down into the 

deeper soil layers (Bockheim and 

Tarnocai, 1998). Soluble organic 

materials move downward because of the effect of gravity and 

the movement of water along the 

thermal gradient toward the freezing front (Kokelj and Burn, 2005). 

Once the organic material has 

moved down to the cold, deeper 

soil layers where very little or no 

biological decomposition takes 

place, it may be preserved for 

many thousands of years. Radiocarbon dates from cryoturbated 

soil materials ranged between 490 

and 11,200 yr BP (Zoltai et al., 

1978). These dates were randomly 

distributed within the soil and 

did not appear in chronological 

sequence by depth (the deepest 

material was not necessarily the 

oldest), indicating that cryoturbation is an ongoing process.

The permafrost table (top of the 

permafrost) is very dynamic 

and is subject to deepening due 

to factors such as removal of 

vegetation and/or the insulating 

surface organic layer, wildfires, 

global climate change, and other 

natural or human activities. When 

this occurs, the seasonally thawed 

layer (active layer) becomes deeper and the organic material is able to move even deeper into the soil (translocation). 

However, if such factors cause thawing of the soil and melting of the ground ice, some or all of the organic materials 

locked in the system could be exposed to the atmosphere. 

This change in soil environment gives rise to both aerobic 

and anaerobic decomposition, releasing carbon into the 

atmosphere as CO2 and CH4, respectively (Figure 12.3). At 

this stage, the soil can become a major carbon source.

If, however, the permafrost table rises (and the active layer 

becomes shallower) because of reestablishment of the vegetation or buildup of the surface organic layer, this deep 

organic material becomes part of the permafrost and is, 

Figure 12.3 Carbon cycle in permafrost-affected upland (mineral) soils, showing belowground organic carbon sinks and sources.
131

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

thus, more securely preserved. This is the main reason that 

permafrost-affected soils contain high amounts of organic 

carbon not only in the upper (0–100 cm) layer, but also in 

the deeper layers. These cryoturbated, permafrost-affected 

soils are effective carbon sinks.

12.2.3 Peatlands (Organic Soils)

The schematic diagram in Figure 12.4 provides general information about the processes driving the carbon sinks and 

sources in peatland soils. The water-saturated conditions, 

low soil temperatures, and acidic conditions of northern 

peatlands provide an environment in which very little decomposition occurs; hence, the litter is converted to peat and 

preserved. This gradual buildup process has been ongoing 

in peatlands during the last 5000–8000 years, resulting in 

peat deposits that are an average of 2–3 meters (m) thick 

and, in some cases, up to 10 m thick. At this stage, peatlands 

can act as very effective carbon sinks for many thousands 

of years (Figure 12.4).

Carbon dynamics: Data for carbon accumulation in various 

peatland types in the permafrost regions are given in Table 

12.3. Although some values for the rate of peat accumulation 

are higher (associated with unfrozen peatlands), the value 

for frozen peatlands, which are more widespread, is 13.31 

± 2.20 grams of carbon per square meter (g C per m2) per 

year (Robinson and Moore, 1999). Peat accumulations in the 

various ecological regions were calculated on the basis of 

the thickness of the deposit and the date of the basal peat. 

The rate of peat accumulation is generally highest in the 

Boreal region and decreases northward (Table 12.3). Note, 

however, that if the surface of the peat deposit has eroded, 

the calculated rate of accumulation (based on the age of 

the basal peat and a decreased 

deposit thickness) will appear 

to be higher than it should be. 

This is probably the reason 

for some of the high rates of 

peat accumulation found for 

the Arctic region, which likely 

experienced a rapid rate of accumulation during the Hypsithermal Maximum with subsequent erosion of the surface of 

some of the deposits reducing 

their thicknesses. Wildfires, 

decomposition, and leaching of 

soluble organic compounds release approximately one-third 

of the carbon input, causing 

most of the carbon loss in these 

peatlands.

12.3 BELOWGROUND CARBON 

STOCKS

The carbon content of mineral soils to a 1-m depth is 49-

61 kilograms (kg) per m2 for 

permafrost-affected soils and 

12-17 kg per m2 for unfrozen 

soils (Tables 12.4 and 12.5). 

The carbon content of organic 

soils (peatlands) for the total 

depth of the deposit is 81-129 

kg per m2 for permafrost-affected soils and 43-144 kg per Figure 12.4 Carbon cycle in permafrost peatlands, showing below-ground organic carbon 

sinks and sources.
The U.S. Climate Change Science Program Chapter 12

132 

m2 for unfrozen soils (Tables 12.4 and 12.5) (Tarnocai, 1998 

and 2000).

Soils in the permafrost region of North America contain 213 

billion tons (Gt) of organic carbon (Tables 12.6 and 12.7), 

which is approximately 61% of the organic carbon in all soils 

on this continent (Lacelle et al., 2000). Mineral soils contain 

approximately 99 Gt of organic carbon in the 0- to 100-cm 

depth (Table 12.6). Although peatlands (organic soils) cover 

a smaller area than mineral soils (17% vs. 83%), they contain 

approximately 114 Gt of organic carbon in the total depth 

of the deposit, or more than half (54%) of the soil organic 

carbon of the region (Table 12.7).

12.4 CARBON FLUXES

12.4.1 Mineral Soils

Very little information is available about carbon 

fluxes in both unfrozen and perennially frozen 

mineral soils in the permafrost regions. For unfrozen upland mineral soils, Trumbore and Harden 

(1997) report a carbon accumulation of 60-100 g C 

per m2 per year (Table 12.4). They further indicate 

that the slow decomposition results in rapid organic 

matter accumulation, but the turnover time due to 

wildfires (every 500–1000 years) eliminates the 

accumulated carbon except for the deep carbon 

derived from roots in the subsoil. The turnover time 

for this deep carbon is 100-1600 years. Therefore, 

the carbon stocks in these unfrozen soils are low, 

and the turnover time of this carbon is 100 to 1600 

years.

As with unfrozen mineral soils, very little information has been published on the carbon cycle in 

perennially frozen mineral soils. The carbon cycle 

in these soils differs from that in unfrozen soils in 

that, because of cryogenic activities, these soils are 

able to move the organic matter deposited on the soil 

surface into the deeper soil layers. Assuming that 

cryoturbation was active in these soils during the 

last six thousand years (Zoltai et al., 1978), an average of 9 million tons of carbon (Mt C)** have been 

added annually to these soils. Most of this carbon 

has been cryoturbated into the deeper soil layers, 

but some of the carbon in the surface organic layer 

is released by decomposition and, periodically, by 

wildfires. The schematic diagram in Figure 12.5 

shows the carbon cycle in these soils.

12.4.2 Peatlands (Organic Soils)

Peatland vegetation deposits various amounts of 

organic material (litter) annually on the peatland 

surface. Reader and Stewart (1972) found that the 

amount of litter (dry biomass) deposited annually on 

the bog surface in boreal peatlands in Manitoba, Canada was 

489-1750 g per m2. Approximately 25% of the original litter 

fall was found to have decomposed during the following 

year. In the course of the study, they found that the average 

annual accumulation rate was 10% of the annual net primary 

production. Robinson and Moore (1999) and Robinson et al. 

(2003) found that, in the Sporadic Permafrost Zone, mean 

carbon accumulation rates over the past 100 years for unfrozen bogs and frost mounds were 88.6 ± 4.4 and 78.5 ± 8.8 

g per m2

 per year, respectively. They also found that, in the 

Discontinuous Permafrost Zone, the mean carbon accumulation rate during the past 1200 years in frozen peat plateaus 

was 13.31 ± 2.20 g per m2 per year, while in unfrozen fens 

Peatlands Amount of carbon

Boreal peatlands –9.8 Mt per yeara

All Canadian peatlands –30 Mt per yearb

All mineral and organic soils –18 mg per m2 per yearc

Rich fens –13.58 ± 1.07 g per m2 per yeard

Poor fens (unfrozen, Discontinuous 

Permafrost Zone) –20.34 ± 2.86 g per m2

 per yeard

Peat plateaus (frozen, Discontinuous 

Permafrost Zone) –13.31 ± 2.20 g per m2

 per yeard

Collapse fens –13.54 ± 1.50 g per m2 per yeard

Bogs (unfrozen, Discontinuous 

Permafrost Zone) –21.81 ± 3.25 g per m2

 per yeard

Dissolved organic carbon (DOC) +2 g per m2 per yeare

Arctic peatlands –0 to –16 cm/100 yrf

Subarctic peatlands –2 to –5 cm/100 yrf

Boreal peatlands –2 to –11 cm/100 yrf

Carbon release by each fire in 

northern boreal peatlands +1.46 kg C per m2

g

Carbon release by fires in all terrain +27 Mt per yearh

Carbon release by fires in Western 

Canadian peatlands +5.9 Mt per yearh

a Zoltai et al. (1988).

b Gorham (1988).

c Liblik et al. (1997).

d Robinson and Moore (1999).

e Moore (1997).

f Calculated based on the thickness of the deposit and the date of the basal 

peat (National Wetlands Working Group, 1988).

g Robinson and Moore (2000).

h Turetsky et al. (2004). 

Note: Except as explicitly indicated otherwise, no estimates of the confidence, 

certainty, or uncertainty of the numerical values in this table are available.

Table 12.3 Organic carbon accumulation and loss in various 

Canadian peatlands. Positive values indicate net flux into the 

atmosphere (source); negative values indicate carbon sequestration (land sinks).
133

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

and bogs the comparable rates were 20.34 ± 2.86 and 21.81 

± 3.25 g per m2 per year, respectively.

Because peatlands cover large areas in the permafrost region 

of North America, their contribution to the carbon stocks is 

significant (Table 12.5). Zoltai et al. (1988) estimated that the 

annual carbon accumulation capacity of boreal peatlands is 

approximately 9.8 Mt†. Gorham (1988), in contrast, estimated 

that Canadian peatlands accumulate approximately 30 Mt 

C† annually. 

Currently, wildfires are probably the greatest natural force 

in converting peatlands to a carbon source. Ritchie (1987) 

found that the western Canadian boreal forests have a fire 

return interval of 50-100 years, while Kuhry (1994) indicated 

that, for wetter Sphagnum bogs, the interval is 400-1700 

years. For peat plateau bogs, each fire resulted in an average 

decrease in carbon mass of 1.46 kg per m2 and an average 

decrease in height of 2.74 cm, which represents about 150 

years of peat accumulation (Robinson and Moore, 2000). In 

recent years, the number of these wildfires has increased, as 

has the area burned, releasing increasing amounts of carbon 

into the atmosphere.

The schematic diagram presented in 

Figure 12.6 summarizes the carbon cycle 

in peatlands in the 

permafrost region. 

Based on average 

values for the rate of 

peat accumulation, 

approximately 17 g 

C per m2

 per year, or 

18 Mt C, is added annually to peatlands in 

this region of North 

America. Approximately 1.46 kg C per 

m2 is released to the 

atmosphere every 600 

years by wildfires in 

the northern boreal 

peatlands. In addition, decomposition 

of unfrozen peatlands 

releases approximately 2.0 g C per m2

 per 

year, and a further 

2.0 g C per m2 per 

year is released by 

leaching of dissolved 

organic carbon (DOC), leading to a carbon decrease of approximately 4 Mt** annually, not including that released by 

wildfires (Figure 12.6). Note that these values are based on 

current measurements. However, rates of peat accumulation 

have varied during the past 5000–8000 years, with periods 

during which the rate 

of peat accumulation 

was much higher than 

at present.

Type

Peatlands Mineral soils

Total Perennially 

frozen Unfrozen Perennially frozen Unfrozen

Current area (× 103 km2) 422a 527a 2088b 2136b 5173

Current pool (Gt) 47c 65a 56c 28b 196

Current atm. flux 

(g per m2 per year) –5.7d –15.2e

Carbon accumulation 

(g per m2 per year) –13.3 ± 2.20f –20.34 ± 2.86 to –21.81 ± 3.25f

–60 to 

–100g

Carbon release by fires 

(g per m2 per year)h +7.57i

Methane flux (g per m2 per 

year) +2.0j

a Calculated using the Peatlands of Canada Database (Tarnocai et al., 2005).

b Calculated using the Soil Carbon of Canada Database (Soil Carbon Database Working Group, 1993).

c Tarnocai (1998).

d Using C accumulation rate of 0.13 mg per ha per year (this report).

e Using C accumulation rate of 0.194 mg per ha per year (Vitt et al., 2000).

f Robinson and Moore (1999).

g Trumbore and Harden (1997).

h Fires recur every 150–190 years (Kuhry, 1994; Robinson and Moore, 2000).

i Robinson and Moore (2000).

j Moore and Roulet (1995).

Note: Except as explicitly indicated otherwise, no estimates of the confidence, certainty, or uncertainty of 

the numerical values in this table are available.

Table 12.4 Soil carbon pools and fluxes for the permafrost areas of Canada. Positive flux 

numbers indicate net flux into the atmosphere (source); negative values indicate carbon 

sequestration (land sinks).

a For the 1-m depth.

b For the total depth of the peat deposit.

Table 12.5 Average organic carbon content for soils in the 

various ecological regions (Tarnocai, 1998 and 2000).

Ecological 

regions

Average carbon content (kg per m2

)

Mineral soilsa Organic soils 

(peatlands)b

Frozen Unfrozen Frozen Unfrozen

Arctic 49 12 86 43

Subarctic 61 17 129 144

Boreal 50 16 81 134

The soils in the permafrost region 

of North America currently 

act as a net carbon sink.
The U.S. Climate Change Science Program Chapter 12

134 

12.4.3 Total Flux

Based on the limited data available for this vast, and largely 

inaccessible, area of the continent, approximately 27 Mt C 

per year** is deposited on the surface of mineral soils and 

peatlands (organic soils) in the permafrost region of North 

America. Approximately 8 Mt per year** of surface carbon 

(excluding vegetation) is released by decomposition and 

wildfires, and by leaching into the water systems. Thus, the 

soils in the permafrost region of North America currently 

act as a sink for approximately 19 Mt C per year** and as a 

source for approximately 8 Mt C per year** and are, therefore, 

a net carbon sink (Figures 12.5 and 12.6).

12.5 POSSIBLE EFFECTS OF GLOBAL 

CLIMATE CHANGE

The permafrost region is unique because the soils in this 

vast area contain large amounts of organic materials and 

much of the carbon has been actively sequestered by peat accumulation (organic soils) and cryoturbation (mineral soils) 

and stored in the permafrost for many thousands of years. 

Historical patterns of climate are responsible for the large 

amount of carbon found in the soils of the region today, but 

cryoturbation is a consequence of the region’s current cool to 

cold climate and the effects of that climate on soil hydrology. 

As a result, patterns of climate and climate change are dominant drivers of carbon cycling in the region. Future climate 

change will determine the fate of that carbon and whether 

the region will remain a slow but significant carbon sink, or 

whether it will reverse and become a source, rapidly releasing large amounts of CO2 and CH4 to the atmosphere.

12.5.1 Peatlands

A model for estimating the sensitivity of peatlands to global 

climate change was developed using current climate (1x 

CO2), vegetation, and permafrost data together with the 

changes in these variables expected in a 2x CO2 environment (Kettles and Tarnocai, 1999). The data generated by 

this model were used to produce a peatland sensitivity map. 

Using geographic information system (GIS) techniques, 

this map was overlaid on the peatland map of Canada to 

Permafrost 

zones

Carbon massa (Gt)

Canadab Alaskac Total

Continuous 51.10 9.04 60.14

Discontinuous 10.33 4.82 15.15

Sporadic 9.15 0.75 9.90

Isolated Patches 13.59 0 13.59

Total 84.17 14.61 98.78

Table 12.6 Organic carbon mass in mineral soils in the 

various permafrost zones.

a Calculated for the 0–100 cm depth.

b Calculated using the Soil Carbon of Canada Database (Soil Carbon 

Database Working Group, 1993).

c Calculated using the Northern and Mid Latitudes Soil Database 

(Cryosol Working Group, 2001).

Permafrost 

zones

Carbon massa (Gt)

Canadab Alaskac Total

Continuous 21.82 1.46 23.28

Discontinuous 26.54 0.84 27.38

Sporadic 30.66 0.27 30.93

Isolated Patches 32.95 0 32.95

Total 111.97 2.57 114.54

Table 12.7 Organic carbon mass in peatlands (organic soils) 

in the various permafrost zones.

a Calculated for the total depth of the peat deposit. 

b Calculated using the Peatlands of Canada Database (Tarnocai et al., 

2005).

c Calculated using the Northern and Mid Latitudes Soil Database 

(Cryosol Working Group, 2001).

Figure 12.6 Carbon cycle in peatlands in the permafrost 

region.

Figure 12.5 Carbon cycle in perennially frozen mineral soils 

in the permafrost region. Question marks represent data values 

that cannot be quantified.
135

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

determine both the sensitivity ratings of the various peatland 

areas and the associated organic carbon masses. The sensitivity ratings, or classes, used are no change, very slight, 

slight, moderate, severe, and extremely severe. Because 

global climate change is expected to have the greatest impact on the ecological processes and permafrost distribution 

in peatlands in the severe and extremely severe categories 

(Kettles and Tarnocai, 1999), the areas and carbon masses 

of peatlands in these two sensitivity classes are considered 

to be most vulnerable to climate change. The sensitivity 

ratings are determined by the degree of change in the ecological zonation combined with the degree of change in the 

permafrost zonation, with the greater the change, the more 

severe the sensitivity rating. For example, if a portion of 

the Subarctic becomes Boreal in ecology and the associated 

sporadic permafrost disappears (no permafrost remains in 

the region), the sensitivity of this region is rated as extremely 

severe. If however, a portion of the Boreal remains Boreal 

in ecology, but the discontinuous permafrost disappears 

(no permafrost remains in the region), the sensitivity of this 

region is rated as severe.

The peatland sensitivity model (Tarnocai, 2006) indicates 

that the greatest effect of global climate change will occur 

in the Subarctic region, where about 85% (314,270 km2

) of 

the peatland area and 78% (33.96 Gt) of the organic carbon 

mass will be severely or extremely severely affected by climate change, with 66% of the area and 57% of the organic 

carbon mass being extremely severely affected (Figure 12.7)

†

. The second largest effect will occur in the Boreal region, 

where about 49% (353,100 km2) of the peatland area and 

41% (40.20 Gt) of the organic carbon mass will be severely 

or extremely severely affected, with 10% of both the area 

and organic carbon mass being extremely severely affected. 

These two regions contain almost all (99%) of the Canadian 

peatland area and organic carbon mass that is predicted to 

be severely or extremely severely affected (Figure 12.7) 

(Tarnocai, 2006).

In the Subarctic region and the northern part of the Boreal 

region, where most of the perennially frozen peatlands 

occur, the increased temperatures are expected to cause 

increased thawing of the perennially frozen peat. Thawing 

of the ice-rich peat and the underlying mineral soil will 

initially result in water-saturated conditions. These watersaturated conditions, together with the higher temperatures, 

result in anaerobic decomposition, leading to the production 

of CH4.

In the southern part 

of the Boreal region, 

where the peatlands 

are generally unfrozen, the main impact is 

expected to be drought 

conditions resulting 

from higher summer 

temperatures and higher evapotranspiration. Under such conditions, peatlands 

become a net source of CO2 because the oxygenated conditions lead to aerobic decomposition (Melillo et al., 1990; 

Christensen, 1991). These dry conditions will likely also 

increase wildfires and, eventually, burning of peat, leading 

to the release of CO2 to the atmosphere.

12.5.2 Permafrost-affected Mineral Soils

The same model described above was used to determine 

the effect of climate change on mineral permafrost-affected soils. The model suggests that 

approximately 21% (11.9 Gt)† of the total 

organic carbon in these soils could be 

severely or extremely severely affected 

by climate warming (Tarnocai, 1999). The 

model also suggests that the permafrost 

will probably disappear from the soils 

(the soils will become unfrozen) in the 

Sporadic and Isolated Patches permafrost 

zones. The main reason for the high sensitivity of mineral soils in these zones is 

that soil temperatures at both the 100- and 

150-cm depths are only slightly below 

freezing (-0.3°C). The slightest disturbance or climate warming could initiate 

rapid thawing in these soils, with resultant 

loss of carbon (Tarnocai, 1999).

Figure 12.7 The organic carbon mass in the various sensitivity classes for the 

Subarctic and Boreal ecoclimatic provinces (ecological regions) (Tarnocai, 2006).

The greatest effect of global 

climate change will occur in the 

Subarctic region, where about 85% 

of the peatland area and 78% of 

the organic carbon mass will be 

severely or extremely severely 

affected by climate change.
The U.S. Climate Change Science Program Chapter 12

136 

12.6 NON-CLIMATIC DRIVERS

Wildfires are an important part of the ecology of Boreal and 

Subarctic forests and are probably the major non-climatic 

drivers of carbon change in the permafrost region. There 

has been a rapid increase in both the frequency of fires and 

the area burned as a result of warmer and drier summers 

and increased human activity in the region. According 

to observations of natives, not only has the frequency of 

lightning strikes increased in the more southerly areas, but 

they have now appeared in more northerly areas where they 

were previously unknown. Because lightning is the major 

cause of wildfires in areas of little habitation, it is likely 

largely responsible for 

the increase in wildfires 

now being observed.

Increased human activity 

as a result of the construction of pipelines, 

roads, airstrips, and 

mines, expansion of agriculture, and development and expansion of town sites has disturbed the natural 

soil cover and exposed the organic-rich soil layers, leading 

to increased soil temperatures and, hence, decomposition 

of the exposed organic materials. Burgess and Tarnocai 

(1997), studying the Norman Wells Pipeline, provide some 

examples of the effect of pipeline construction on frozen 

peatlands and permafrost in Canada.

Shoreline erosion along rivers, lakes, and oceans and thermal erosion (thermokarst) are also common processes in 

the permafrost region, exposing the carbon-rich frozen soil 

layers to the atmosphere and making the organic materials available for decomposition. Along the 1957 km of the 

Beaufort Sea coast of Arctic Alaska, an estimated 1.8x105

Mg C per year erodes into the Arctic Ocean due to thawing 

of permafrost. As a result, CO2 and CH4 are released directly 

into the atmosphere, but most of this carbon goes into the 

ocean as particulate organic matter, and a small fraction 

as dissolved organic carbon (Jorgenson and Brown, 2005; 

Ping et al., 2006).

Large hydroelectric projects in northern areas, such as 

Southern Indian Lake in Manitoba and the James Bay region 

of Quebec, have flooded vast areas of peatlands and initiated 

permafrost degradation and decomposition of organic carbon, some of which is released into the atmosphere as CH4. 

Of greater immediate concern, however, is the carbon that 

has entered the water system as dissolved organic carbon. 

These compounds include contaminants such as persistent 

organic pollutants (e.g., Polychlorinated biphenyls [PCBs], 

Dichloro-Diphenyl-Trichloroethane [DDT], Hexachlorocyclohexanes [HCH], and chlorobenzene [AMAP, 2004]) that 

have been widely distributed in northern ecosystems over 

many years, much of it deposited by snowfalls, concentrated by cryoturbation, and stored in the organic soils. Of 

particular concern is the release of methylmercury because 

peatlands are net producers of this compound (Driscoll et 

al., 1998; Suchanek et al., 2000), which is a much greater 

health hazard than inorganic or elemental mercury. Natives 

There has been a rapid 

increase in both the frequency 

of fires and the area burned 

as a result of warmer and 

drier summers and increased 

human activity in the region.
137

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

in the regions where these hydroelectric developments have 

taken place have developed mercury poisoning after ingesting fish contaminated by this mercury, leading to serious 

health problems for many of the people. This is an example 

of what can happen when permafrost degrades as a result 

of human activities. When climate warming occurs, the 

widespread degradation of permafrost, with the resulting 

release of such dangerous pollutants into the water systems, 

could cause serious health problems for fish, animals, and 

humans that rely on such waters.

12.7 OPTIONS FOR MANAGEMENT OF 

CARBON IN THE PERMAFROST REGION

Although wildfires are the most effective mechanism for 

releasing carbon into the atmosphere, they are also an important factor in maintaining the integrity of northern ecosystems. Therefore, such fires are allowed to burn naturally 

and are controlled only if they are close to settlements or 

other man-made structures.

The construction methods currently used in permafrost 

terrain are designed to cause as little surface disturbance 

as possible and to preserve the permafrost. Thus, the construction of pipelines, airstrips, and highways is commonly 

carried out in the winter so that the heavy equipment used 

will cause minimal surface disturbance.

The greatest threat to the region is a warmer (and possibly 

drier) climate, which would drastically affect not only the 

carbon cycle, but also the biological systems, including human life. Unfortunately, we know very little about how to 

manage the natural systems in this new environment.

12.8 DATA GAPS AND UNCERTAINTIES

The permafrost environment is a very complex system, and 

the data available for it are very limited with numerous gaps 

and uncertainties. Information on the distribution of soils in 

the permafrost region is based on small-scale maps, and the 

carbon stocks calculated for these soils are derived from a 

relatively small number of datasets. Although there is some 

understanding of the carbon sinks and sources in these soils, 

the limited amount of data available make it very difficult, or 

impossible, to assign reliable values. Only limited amounts 

of flux data have been collected for the permafrost-affected 

soils and, in some cases, it has been collected on sites that 

are not representative of the overall landscape. This makes 

it very difficult to scale this information up for a larger area. 

As Davidson and Janssens (2006) state:

“...the unresolved question regarding 

peatlands and permafrost is not 

the degree to which the currently 

constrained decomposition rates are 

temperature sensitive, but rather how 

much permafrost is likely to melt and 

how much of the peatland area is likely 
The U.S. Climate Change Science Program Chapter 12

138 

to dry significantly. Such regional 

changes in temperature, precipitation, 

and drainage are still difficult to predict 

in global circulation models. Hence, 

the climate change predictions, as 

much as our understanding of carbon 

dynamics, limit our ability to predict 

the magnitude of likely vulnerability of 

peat and permafrost carbon to climate 

change.”

To obtain more reliable estimates of the carbon sinks and 

sources in permafrost-affected soils, we need much more 

detailed data on the distribution and characteristics of these 

soils. Carbon stock estimates currently exist only for the upper 1 m of the soil. Limited data from the Mackenzie River 

Valley in Canada, Arctic coast of Alaska and the Kolyma 

Lowland of NE Russia indicate that a considerable amount 

of soil organic carbon occurs below the 1-m depth, even at 

the 3-m depth. Future estimates of carbon stocks should be 

extended to cover a depth of 0-2 m or, in some cases, even 

greater depths. More measurements of carbon fluxes and 

inputs are also needed if we are to understand the carbon 

sequestration process in these soils in the various permafrost 

zones. Our understanding of the effect that rapid climate 

warming will have on the carbon sinks and sources in these 

soils is also very limited. Future research should focus in 

greater detail on how the interactions of climate with the 

biological and physical environments will affect the carbon 

balance in permafrost-affected soils.

The changes that are occurring, and will occur, in the permafrost region are almost totally driven by natural forces 

and so are almost impossible for humans to manage on a 

large scale. Human activities, such as they are, are aimed at 

protecting the permafrost and, thus, preserving the carbon. 

Perhaps we humans should realize that there are systems 

(e.g., glaciers, ocean currents, droughts, and rainfall) that 

will be impossible for us to manage. We simply must learn 

to accept them, and if possible, adapt.
The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

Wetlands

CHAPTER

13

139

Lead Author: Scott D. Bridgham, Univ. Oreg.

Contributing Authors: J. Patrick Megonigal, Smithsonian 

Environmental Research Center; Jason K. Keller, Smithsonian 

Environmental Research Center; Norman B. Bliss, SAIC, USGS 

Center for Earth Resources Observation and Science; Carl Trettin, 

USDA Forest Service

KEY FINDINGS

North America is home to approximately 40% of the global wetland area, encompassing about 2.5 million square 

kilometers (965,000 square miles) with a carbon pool of approximately 223 billion tons, mostly in peatland soils.

North American wetlands currently are a carbon dioxide sink of approximately 49 million tons of carbon per year, 

but that estimate has an uncertainty of greater than 100%. North American wetlands are also a source of approximately 9 million tons of methane, a more potent atmospheric heat-trapping gas. The uncertainty in that flux is also 

greater than 100%.

Historically, the destruction of North American wetlands through land-use change has reduced carbon storage in 

wetlands by 15 million tons of carbon per year, primarily through the oxidation of carbon in peatland soils as they 

are drained and a more general reduction in carbon uptake and storage capacity of wetlands converted to other 

land uses. Methane emissions have also declined with the loss of wetland area.

Projections of future carbon storage and methane emissions of North American wetlands are highly uncertain and 

complex, but the large carbon pools in peatlands may be at risk for oxidation and release to the atmosphere as 

carbon dioxide if they become substantially warmer and drier. Methane emissions may increase with warming, but 

the response will likely vary with wetland type and with changes in precipitation.

Because of the potentially significant role of North American wetlands in methane production, the activities associated with the restoration, creation, and protection of wetlands are likely to focus on the ecosystem services 

that wetlands provide, such as filtering 

of toxics, coastal erosion protection, 

wildlife habitat, and havens of biological diversity, rather than on carbon 

sequestration, per se.

Research needs to reduce the uncertainties in carbon storage and fluxes 

in wetlands to provide information 

about management options in terms 

of carbon uptake and storage and 

trace gas fluxes.

•

•

•

•

•

•

•

•

•
The U.S. Climate Change Science Program Chapter 13

1440 

13.1 INTRODUCTION

While there are a variety of legal and scientific definitions 

of a wetland (National Research Council, 1995; National 

Wetlands Working Group, 1997), most emphasize the presence of waterlogged conditions in the upper soil profile 

during at least part of the growing season, and plant species 

and soil conditions that reflect these hydrologic conditions. 

Waterlogging tends to suppress microbial decomposition 

more than plant productivity, so wetlands are known for 

their ability to accumulate large amounts of soil carbon, most 

spectacularly seen in large peat deposits that are often many 

meters deep. Thus, when examining carbon dynamics, it is 

important to distinguish between freshwater wetlands with 

surface soil organic matter deposits greater than 40 cm thick 

(i.e., peatlands) and those with lesser amounts of soil organic 

matter (i.e., freshwater mineral-soil wetlands [FWMS]). 

Some wetlands have permafrost (fluxes and pools in wetlands with and without permafrost are discussed separately 

in Appendix F). We also differentiate between freshwater 

wetlands and estuarine wetlands (salt marshes, mangroves, 

and mud flats) with marine-derived salinity.

Peatlands occupy about 3% of the terrestrial global surface, 

yet they contain 16–33% of the total soil carbon pool (Gorham, 1991; Maltby and Immirzi, 1993)1

. Most peatlands occur between 50 and 70o N, although significant areas occur 

at lower latitudes (Matthews and Fung, 1987; Aselmann 

and Crutzen, 1989; Maltby and Immirzi, 1993). Large areas 

of peatlands exist in Alaska, Canada, and in the northern 

midwestern, northeastern, and southeastern United States 

(Bridgham et al., 2000). Because this peat formed over 

thousands of years, these areas represent a large carbon pool, 

but with relatively slow 

rates of accumulation. 

By comparison, estuarine wetlands and some 

freshwater mineral-soil 

wetlands rapidly sequester carbon as soil organic 

matter due to rapid burial 

in sediments. Large areas of wetlands have been converted 

to other land uses, globally and in North America (Dugan, 

1993; OECD, 1996), which may have resulted in a net flux 

of carbon to the atmosphere (Armentano and Menges, 

1986; Maltby and Immirzi, 1993). Additionally, wetlands 

emit 92–237 million tons of methane (Mt CH4) per year1

, 

which is a large fraction of the total annual global flux of 

about 600 Mt CH4 per year (Ehhalt et al., 2001). This is 

important because CH4 is a potent greenhouse gas (GHG), 

second in importance only to carbon dioxide (CO2) (Ehhalt 

et al., 2001).

1

 The uncertainties for the numerical values cited in this chapter are 

presented and explained in Table 13.1 and Appendix F.

A number of previous studies have examined the role of 

peatlands in the global carbon balance (reviewed in Mitra 

et al., 2005), and Roulet (2000) focused on the role of Canadian peatlands in the Kyoto process. Here we augment these 

previous studies by considering all types of wetlands (not 

just peatlands) and integrate new data to examine the carbon 

balance in the wetlands of Canada, the United States, and 

Mexico. We also briefly compare these values to those from 

global wetlands. We limit this review to those components of 

the carbon budget that result in a net gaseous exchange with 

the atmosphere on an interannual basis and do not consider 

other internal carbon fluxes. We do not consider dissolved 

organic carbon (DOC) fluxes from wetlands, although they 

may be substantial (Moore, 1997), because the oxidation of 

the DOC would be counted as atmospheric carbon emissions 

in the receiving ecosystems downstream and we do not want 

to double-count fluxes.

Given that many undisturbed wetlands are a natural sink for 

CO2 and a source of CH4, a note of caution in interpretation 

of our data is important. Using the Intergovernmental Panel 

on Climate Change (IPCC) terminology, a radiative forcing 

denotes “an externally imposed perturbation in the radiative 

energy budget of the Earth’s climate system” (Ramaswamy 

et al., 2001). Thus, it is the change from a baseline condition 

in GHG fluxes in wetlands that constitute a radiative forcing 

that will impact climate change, and carbon fluxes in unperturbed wetlands are important only in establishing a baseline 

condition. For example, historical steady state rates of CH4

emissions from wetlands have zero net radiative forcing, but 

an increase in CH4 emissions due to climatic warming would 

constitute a positive radiative forcing. Similarly, steady state 

rates of soil carbon sequestration in wetlands have zero net 

radiative forcing, but the lost sequestration capacity and the 

oxidation of the soil carbon pool in drained wetlands are 

both positive radiative forcings.

13.2 INVENTORIES

13.2.1 Current Wetland Area and Rates of Loss

The current and original wetland area and rates of loss are 

the basis for all further estimates of pools and fluxes in this 

chapter. The loss of wetlands has caused the oxidation of 

their soil carbon, particularly in peatlands, reduced their 

ability to sequester carbon, and reduced their emissions of 

CH4. The strengths and weakness of the wetland inventories 

of Canada, the United States, and Mexico are discussed in 

Appendix F.

The conterminous United States has 312,000 km2 of FWMS 

wetlands, 93,000 km2 of peatlands, and 25,000 km2 of estuarine wetlands, which encompass 5.5% of the land area (Table 

13.1). This represents just 48% of the original wetland area 

in the conterminous United States (Table F.1 in Appendix F). 

5.5% of the land area of the 

contiguous United States is 

wetlands. This represents just 48% 

of the original wetland area in 

the conterminous United States.
1441

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

a Estuarine includes salt marsh, mangrove, and mudflat, except for Mexico and global for which no mudflat estimates were available.

b Includes soil carbon and plant carbon, but overall soil carbon is 98% of the total pool.

c Includes soil carbon sequestration, plant carbon sequestration, and loss of carbon due to drainage of wetlands. Plant carbon 

sequestration and soil oxidative flux due to drainage are either unknown or negligible for North American wetlands except for the 

conterminous United States (see Appendix F). 

ND indicates that no data are available.

Areaa

(km2)

Carbon Poolb

(Gt C)

Net Carbon 

Balancec

(Mt C per 

year)

Historical 

Loss in 

Sequestration 

Capacity

(Mt C per year)

Methane Flux

(Mt CH4 per 

year)

Canada

Peatland 1,135,608  152** ** -19*** 0.3* 3.2**

Freshwater Mineral 158,720** 4.9** -2.7* 3.4* 1.2*

Estuarine 6,400*** 0.1*** -1.3** 0.5* 0.0***

Total 1,300,728  157** ** -23** 4.2* 4.4*

Alaska

Peatland 132,196**** 15.9** -2.0** 0.0**** 0.3*

Freshwater Mineral 555,629**** 27.1** -9.4* 0.0**** 1.4*

Estuarine 8,400**** 0.1*** -1.9** 0.0  0.0** *

Total 696,224***** 43.2** -13* 0.0**** 1.7*

Conterminous United States

Peatland 93,477**** 14.4*** 5.7* 1.2* 0.7**

Freshwater Mineral 312,193***** 6.2*** -9.8* 7.6* 2.4**

Estuarine 25,000***** 0.6***** -5.4** 0.5* 0.0***

Total 430,670***** 21.2*** -9.5* 9.4* 3.1**

U.S. Total 1,126,895***** 64.3** -23* 9.4* 4.8**

Mexico

Peatland 10,000* 1.5* -1.6* ND* 0.1*

Freshwater Mineral 20,685* 0.4* -0.4* ND* 0.2*

Estuarine 5,000* 0.2* -1.6* 1.0* 0.0*

Total 35,685* 2.0* -3.6* ND* 0.2*

North America

Peatland 1,371,281**** 184**** -17* 1.5* 4.3**

Freshwater Mineral 1,047,227  39** * -22* 11* 5.1*

Estuarine 44,800*** 0.9*** -10** 2.0* 0.1**

Total 2,463,308  223** ** -49* 15* 9.4*

Global

Peatland 3,443,000*** 462*** 150** 16* 37**

Freshwater Mineral 2,315,000*** 46*** -39* 45* 68**

Estuarine 203,000* 5.4* -43* 21* 0.2**

Total 5,961,000*** 513*** 68* 82* 105**

Table 13.1 The area, carbon pool, net carbon balance, and methane flux from wetlands in North America 

and the world. Positive fluxes indicate net fluxes to the atmosphere, whereas negative fluxes indicate 

net fluxes into an ecosystem. Citations and assumptions in calculations are in the text and in Appendix 

F (see Box 13.1 for uncertainty conventions).

BOX 13.1: CCSP SAP 2.2 Uncertainty Conventions

***** = 95% certain that the actual value is within 10% of the estimate reported, 

  = 95% certain that the estimate is within 25%, 

** * = 95% certain that the estimate is within 50%, 

** = 95% certain that the estimate is within 100%, and

* = uncertainty greater than 100%.
The U.S. Climate Change Science Program Chapter 13

1442 

However, wetland losses in the United States have declined 

from 1855 km2 per year in the 1950s–1970s to 237 km2

per year in the 1980s–1990s (Dahl, 2000). Such data mask 

large differences in loss rates among wetland classes and 

conversion of wetlands to other classes (Dahl, 2000), with 

potentially large effects on carbon stocks and fluxes. For 

example, the majority of wetland losses in the United States 

have occurred in FWMS wetlands. As of the early 1980s, 

84% of United States’ peatlands were unaltered (Armentano 

and Menges, 1986; Maltby and Immirzi, 1993; Rubec, 1996), 

and, given the current regulatory environment in the United 

States, recent rates of loss are likely small.

Canada has 1,301,000 km2 of wetlands, covering 14% of its 

land area, of which 87% are peatlands (Table 13.1). Canada 

has lost about 14% of its wetlands, mainly due to agricultural 

development of FWMS wetlands (Rubec, 1996), although 

the ability to estimate wetland losses in Canada is limited 

by the lack of a regular wetland inventory.

The wetland area in Mexico is estimated at 36,000 km2

(Table 13.1), with an estimated historical loss of 16,000 

km2 (Table F.1 in Appendix F). However, given the lack of a 

nationwide wetland inventory and a general paucity of data, 

this number is highly uncertain.

Problems with inadequate wetland inventories are even more 

prevalent in lesser developed 

countries (Finlayson et al., 

1999). We estimate a global 

wetland area of 6.0 × 106 km2

(Table 13.1); thus, North America currently has about 43% 

of the global wetland area. It has been estimated that about 

50% of the world’s original wetlands have been converted to 

other uses (Moser et al., 1996).

13.2.2 Carbon Pools

We estimate that North American 

wetlands have a current soil and plant 

carbon pool of 223 billion tons (Gt), 

of which approximately 98% is in the 

soil (Table 13.1). The majority of this 

carbon is in peatlands, with FWMS 

wetlands contributing about 18% of 

the carbon pool. The large amount of 

soil carbon (27 Gt) in Alaskan FWMS 

wetlands had not been identified in 

previous studies (see Appendix F).

13.2.3 Soil Carbon Fluxes

North American peatlands currently 

have a net carbon balance of about -17 

million metric tons of carbon (Mt C) 

per year (Table 13.1), but several large fluxes are incorporated into this estimate. (Negative numbers indicate net fluxes 

into the ecosystem, whereas positive numbers indicate net 

fluxes into the atmosphere). Peatlands sequester -29 Mt C 

per year (Table F.2 in Appendix F). However, this carbon 

sink is partially offset by a net oxidative flux of 18 Mt C per 

year as of the early 1980s in peatlands in the conterminous 

United States that have been drained for agriculture and forestry (Armentano and Menges, 1986). Despite a substantial 

reduction in the rate of wetland loss since the 1980s (Dahl, 

2000), drained organic soils continue to lose carbon over 

many decades, so the actual flux to the atmosphere is probably close to the 1980s estimate. There has also been a loss 

in sequestration capacity in drained peatlands of 1.5 Mt C 

per year (Table 13.1), so the overall soil carbon sink of North 

American peatlands is about 20 Mt C per year smaller than 

it would have been in the absence of disturbance.

Very little attention has been given to the role of FWMS wetlands in North American or global carbon balance estimates, 

with the exception of CH4 emissions. Carbon sequestration 

associated with sediment deposition is a potentially large, 

but poorly quantified, flux in wetlands (Stallard, 1998; Smith 

et al., 2001). We estimate that North American FWMS wetlands sequester -18 Mt C per year in sedimentation (Table F.2 

in Appendix F). However, as discussed in Appendix F, wetland sedimentation rates are extremely variable. Moreover, 

almost no studies have placed sediment carbon sequestration 

in FWMS wetlands in a landscape context, considering allochthonous-derived (from on-site plant production) versus 

autochthonous-derived (imported from outside the wetland) 

carbon, replacement of carbon in terrestrial source areas, and 

differences in decomposition rates between sink and source 

areas (Stallard, 1998; Harden et al., 1999; Smith et al., 2001). 

However, it is clear that sedimentation in FWMS wetlands 

North America currently 

has about 43% of the 

global wetland area.
1443

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

is a potentially substantial carbon sink and an important 

unknown in carbon budgets. For example, agriculture typically increases sedimentation rates by 10- to 100-fold and 

90% of sediments are stored within the watershed, amounting to about -40 Mt C per year in the conterminous United 

States (Stallard, 1998; Smith et al., 2001). Our estimate of 

sediment carbon sequestration in FWMS wetlands seems 

quite reasonable in comparison to within-watershed sediment storage in North America. Moreover, Stallard (1998) 

and Smith et al. (2001) estimated a global sediment sink on 

the order of -1 Gt C per year.

Decomposition of soil carbon in FWMS wetlands that have 

been converted to other land uses appears to be responsible 

for only a negligible loss of soil carbon, currently (Table F.2 

in Appendix F). However, due to the historical loss of FWMS 

wetland area, we estimate that they currently sequester 11 

Mt C per year less than they did prior to disturbance (Table 

13.1). This estimate has the same unknowns described in the 

previous paragraph on current sediment carbon sequestration in extant FWMS wetlands.

We estimate that estuarine wetlands currently sequester 

-10.2 Mt C per year (Table F.2 in Appendix F), with a historical reduction in sequestration capacity of 2.0 Mt C per 

year due to loss of area (Table 13.1). However, the reduction 

is almost certainly greater because our “original” area is 

only from the 1950s. Despite the relatively small area of 

estuarine wetlands, they currently contribute about 31% 

of total wetland carbon sequestration in the conterminous 

United States and about 18% of the North American total. 

Estuarine wetlands sequester carbon at a rate about 10 times 

higher on an area basis than other wetland ecosystems due 

to high sedimentation rates, high soil carbon content, and 

constant burial due to sea level rise. Estimates of sediment 

deposition rates in estuarine wetlands are reasonably robust, 

but the same ‘landscape’ issues of allochthonous versus 

autochthonous inputs of carbon, replenishment of carbon 

in source area soils, and differences in decomposition rates 

between sink and source areas exist as for FWMS wetlands. 

Another large uncertainty in the estuarine carbon budget 

is the area and carbon content of mud flats, particularly in 

Canada and Mexico.

Overall, North American wetland soils appear to be a substantial carbon sink with a net flux of -49 Mt C per year (with 

very large error bounds because of FWMS wetlands) (Table 

13.1). The large-scale conversion of wetlands to upland uses 

has led to a reduction in the wetland soil carbon sequestration capacity of 15 Mt C per year from the likely historical 

rate (Table 13.1), but this estimate is driven by large losses of 

FWMS wetlands with their highly uncertain sedimentation 

carbon sink. Adding in the current net oxidative flux of 18 

Mt C per year from conterminous United States’ peatlands, 

we estimate that North American wetlands currently sequester 33 Mt C per year less than they did historically (Table 

F.2 in Appendix F). Furthermore, North American peatlands 

and FWMS wetlands have lost 2.6 Gt and 0.8 Gt of soil carbon, respectively, and collectively they have lost 2.4 Gt of 

plant carbon since approximately 1800. Very little data exist 

to estimate carbon fluxes for freshwater Mexican wetlands, 

but because of their small area, they will not likely have a 

large impact on the overall North American estimates.

The global wetland soil carbon balance has only been examined in peatlands, which currently are a moderate source of 

atmospheric carbon of about 150 Mt C per year (Table 13.1), 

largely due to the oxidation of peat drained for agriculture 

and forestry and secondarily due to peat combustion for fuel 

(Armentano and Menges, 1986; Maltby and Immirzi, 1993). 

The cumulative historical shift in soil carbon stocks has been 

estimated to be 5.5 to 7.1 Gt C (Maltby and Immirzi, 1993). 

Although we are aware of no previous evaluation of the carbon balance of global FWMS and estuarine wetlands, using 

the assumption noted above, we estimate that they are a sink 

of approximately -39 and -43 Mt per year, respectively.

13.2.4 Methane and Nitrous

Oxide Emissions

We estimate that North 

American wetlands 

emit 9.4 Mt CH4 per 

year (Table 13.1). For 

comparison, a mechanistic CH4 model yielded emissions of 3.8 and 

7.1 Mt CH4 per year for 

Alaska and Canada, 

respectively (Zhuang 

et al., 2004). A regional inverse atmospheric modeling approach estimated total CH4 emissions (from all sources) of 

16 and 54 Mt CH4 per year for boreal and temperate North 

America, respectively (Fletcher et al., 2004b).

Methane emissions are currently about 5 Mt CH4 per year 

less than they were historically in North American wetlands 

(see Table F.4 in Appendix F) because of the loss of wetland area. We do not consider the effects of conversion of 

wetlands from one type to another (Dahl, 2000), which may 

have a significant impact on CH4 emissions. Similarly, we 

estimate that global CH4 emissions from natural wetlands 

are only about half of what they were historically due to 

loss of area (Table F.4 in Appendix F). However, this may 

be an overestimate because wetland losses have been higher 

in more developed countries than less developed countries 

(Moser et al., 1996), and wetlands at lower latitudes have 

higher emissions on average (Bartlett and Harriss, 1993).

Despite the relatively small 

area of estuarine wetlands, they 

currently contribute about 

31% of total wetland carbon 

sequestration in the conterminous 

United States and about 18% 

of the North American total.
The U.S. Climate Change Science Program Chapter 13

144 

When we multiplied the very low published estimates of 

nitrous oxide emissions from natural and disturbed wetlands 

(Joosten and Clarke, 2002) by North American wetland 

area, the flux was insignificant (data not shown). However, 

nitrous oxide emissions have been measured in few wetlands, particularly in FWMS wetlands and wetlands with 

high nitrogen inputs (e.g., from agricultural run-off) where 

emissions might be expected to be higher.

We use global warming potentials (GWPs) as a convenient 

way to compare the relative contributions of CO2 and CH4

fluxes in North American wetlands to the Earth’s radiative balance. The GWP is 

the radiative effect of a 

pulse of a substance into 

the atmosphere relative to 

CO2 over a particular time 

horizon (Ramaswamy et 

al., 2001). However, it is 

important to distinguish between radiative balance, which 

refers to the static radiative effect of a substance, and radiative forcing, which refers to an externally imposed perturbation on the Earth’s radiative energy budget (Ramaswamy 

et al., 2001). Thus, changes in radiative balance lead to a 

radiative forcing, which subsequently leads to a change in 

the Earth’s surface temperature. For example, wetlands have 

a large effect on the Earth’s radiative balance through high 

CH4 emissions, but it is only to the extent that emissions 

change through time that they represent a positive or negative radiative forcing and impact climate change.

Methane has GWPs of 1.9, 6.3, and 16.9 CO2-carbon 

equivalents on a mass basis across 500-year, 100-year, 

and 20-year time frames, respectively (Ramaswamy et al., 

2001)2. Depending upon the time frame and within the large 

confidence limits of many of our estimates in Table 13.1, 

the net radiative balance of North American wetlands as a 

whole currently are approximately neutral in terms of net 

CO2-carbon equivalents to the atmosphere (note that we discuss net radiative forcing in Trends and Drivers of Wetland 

Carbon Fluxes, Section 13.3). The exception is estuarine 

wetlands, which are a net 

sink for CO2-carbon equivalents because they support 

both rapid rates of carbon 

sequestration and low CH4

emissions. However, caution should be exercised 

in using GWPs to draw 

2

 GWPs in Ramaswamy et al. (2001) were originally reported in 

CO2-mass equivalents. We have converted them into CO2-carbon 

equivalents so that the net carbon balance and CH4 flux columns in 

Table 13.1 can be directly compared by multiplying CH4 fluxes by 

the GWPs given here.

conclusions about changes in the net flux of CO2-carbon 

equivalents because GWPs are based upon a pulse of a gas 

into the atmosphere, whereas carbon sequestration is more 

or less continuous. For example, if one considers continuous 

CH4 emissions and carbon sequestration in peat over time, 

most peatlands are a net sink for CO2-carbon equivalents 

because of the long lifetime of CO2 sequestered as peat 

(Frolking et al., 2006).

13.2.5 Plant Carbon Fluxes

We estimate that wetland forests in the conterminous United 

States currently sequester -10.3 Mt C per year as increased 

plant biomass (see Table F.3 in Appendix F). Sequestration in 

plants in undisturbed wetland forests in Alaska, many peatlands, and estuarine wetlands is probably minimal, although 

there may be substantial logging of Canadian forested peatlands that we do not have the data to account for.

13.3 TRENDS AND DRIVERS OF 

WETLAND CARBON FLUXES

While extensive research has been done on carbon cycling 

and pools in North American wetlands, to our knowledge, 

this is the first attempt at an overall carbon budget for all 

of the wetlands of North America, although others have 

examined the carbon budget for North American peatlands 

as part of global assessments (Armentano and Menges, 

1986; Maltby and Immirzi, 1993; Joosten and Clarke, 2002). 

Historically, the destruction of wetlands through land-use 

changes has had the largest effect on the carbon fluxes 

and, consequently, the radiative forcing of North American 

wetlands. The primary effects have been a reduction in their 

ability to sequester carbon (a small to moderate increase 

in radiative forcing depending on carbon sequestration by 

sedimentation in FWMS and estuarine wetlands), oxidation 

of their soil carbon reserves upon drainage (a small increase 

in radiative forcing), and a reduction in CH4 emissions (a 

small to large decrease in radiative forcing depending on 

actual emissions) (Table F.1 and Appendix F). Globally, the 

disturbance of peatlands appears to have shifted them into a 

net source of carbon to the atmosphere. Any positive effect 

of wetland loss due to a reduction in their CH4 emissions, 

and hence radiative forcing, will be more than negated by 

the loss of the many ecosystem services they provide, such 

as havens for biodiversity, recharge of groundwater, reduction in flooding, fish nurseries, etc. (Zedler and Kercher, 

2005).

A majority of the effort in examining future global change 

impacts on wetlands has focused on northern peatlands 

because of their large soil carbon reserves, although under 

current climate conditions they have modest CH4 emissions 

(Moore and Roulet, 1995; Roulet, 2000; Joosten and Clarke, 

2002, and references therein). The effects of global change 

Historically, the destruction 

of wetlands through land-use 

changes has had the largest 

effect on the carbon fluxes.

Wetland ecosystems provide 

havens for biodiversity, 

recharge of groundwater, 

and reduction in flooding 

and fish nurseries.
145

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

on carbon sequestration in peatlands are probably 

of minor importance as a global flux because of the 

relatively low rate of peat accumulation. However, 

losses of soil carbon stocks in peatlands drained for 

agriculture and forestry (Table F.2 in Appendix F) 

attest to the possibility of large losses from the massive soil carbon deposits in northern peatlands if 

they become substantially drier in a future climate. 

Furthermore, Turetsky et al. (2004) estimated that 

up to 5.9 Mt C per year are released from western 

Canadian peatlands by fire and predicted that increases in fire frequency may cause these systems 

to become net atmospheric carbon sources. We did 

not add this flux to our estimate of the net carbon 

balance of North American wetlands because 

historical oxidation of peat by fire should be integrated in 

the peat sequestration estimates and recent changes due to 

anthropogenic effects are highly uncertain.

Our compilation shows that attention needs to be directed toward understanding climate change impacts to FWMS wetlands, which collectively emit similar amounts of CH4 and 

potentially sequester an equivalent amount of carbon than 

peatlands. The effects of changing water table depths are 

somewhat more tractable in FWMS wetlands than peatlands 

because FWMS wetlands have less potential for oxidation of 

soil organic matter. In forested FWMS wetlands, increased 

precipitation and runoff may increase radiative forcing by 

simultaneously decreasing wood production and increasing 

methanogenesis (Megonigal et al., 2005). The influence of 

changes in hydrology on CH4 emissions, plant productivity, 

soil carbon preservation, and sedimentation will need to be 

addressed in order to fully anticipate climate change impacts 

on radiative forcing in these systems.

The effects of global change on estuarine wetlands is of concern because sequestration rates are rapid, and they can be 

expected to increase in proportion to the rate of sea level rise 

provided estuarine wetland area does not decline. Because 

CH4 emissions from estuarine wetlands are low, this increase 

in sequestration capacity could represent a net decrease in 

radiative forcing, depending on how much of the sequestered 

carbon is autochthonous. Changes in tidal wetland area with 

sea-level rise will depend on rates of inland migration, erosion at the wetland-estuary boundary, and wetland elevation 

change. The rate of loss of tidal wetland area has declined 

in past decades due to regulations on draining and filling 

activities (Dahl, 2000). However, rapid conversion to open 

water is occurring in coastal Louisiana (Bourne, 2000) and 

Maryland (Kearney and Stevenson, 1991), suggesting that 

marsh area will decline with increased rates of sea level rise 

(Kearney et al., 2002). A multitude of human and climate 

factors are contributing to the current losses (Turner, 1997; 

Day Jr. et al., 2000; Day Jr. et al., 2001). Although it is uncertain how global changes in climate, eutrophication, and 

other factors will interact with sea level rise (Najjar et al., 

2000), it is likely that increased rates of sea level rise will 

cause an overall decline in estuarine marsh area and soil 

carbon sequestration.

One of the greatest concerns is how climate change will 

affect future CH4 emissions from wetlands because of their 

large GWP. Wetlands emit about 105 Mt CH4 per year (Table 

13.1), or 20% of the global total. Increases in atmospheric 

CH4 concentrations over 

the past century have 

had the second largest 

radiative forcing (after 

CO2) in human-induced 

climate change (Ehhalt 

et al., 2001). Moreover, 

CH4 fluxes from wetlands have provided an important radiative feedback on climate over the geologic past (Chappellaz 

et al., 1993; Blunier et al., 1995; Petit et al., 1999). The large 

global warming observed since the 1990s may have resulted 

in increased CH4 emissions from wetlands (Fletcher et al., 

2004a; Wang et al., 2004; Zhuang et al., 2004).

Data (Bartlett and Harriss, 1993; Moore et al., 1998; Updegraff et al., 2001) and modeling (Gedney et al., 2004; Zhuang 

et al., 2004) strongly support the contention that water table 

position and temperature are the primary environmental 

controls over CH4 emissions. How this generalization plays 

out with future climate change is, however, more complex. 

For example, most climate models predict much of Canada 

will be warmer and drier in the future. Based upon this prediction, Moore et al. (1998) proposed a variety of responses 

to climate change in the carbon fluxes from different types 

of Canadian peatlands. Methane emissions may increase in 

collapsed former-permafrost bogs (which will be warmer 

and wetter) but decrease in fens and other types of bogs 

(warmer and drier). A CH4-process model predicted that 

modest warming will increase global wetland emissions, 

It is likely that increased rates of 

sea level rise will cause an overall 

decline in estuarine marsh area 

and soil carbon sequestration.
The U.S. Climate Change Science Program Chapter 13

1446 

but larger increases in temperature will decrease emissions 

because of drier conditions (Cao et al., 1998).

The direct, non-climatic effects of increasing atmospheric 

CO2 on carbon cycling in wetland ecosystems has received 

far less attention than upland systems. Field studies have 

been done in tussock tundra (Tissue and Oechel, 1987; Oechel et al., 1994), bog-type peatlands (Hoosbeek et al., 2001), 

rice paddies (Kim et al., 2001), and a salt marsh (Rasse et 

al., 2005); and a somewhat wider variety of wetlands have 

been studied in small scale glasshouse systems. Temperate and tropical wetland ecosystems consistently respond 

to elevated CO2 with an increase in photosynthesis and/or 

biomass (Vann and Megonigal, 2003). By comparison, the 

response of northern peatland plant communities has been 

inconsistent. A hypothesis that remains untested is that the 

elevated CO2 response of northern peatlands will be limited 

by nitrogen availability. In an in situ study of tussock tundra, 

complete photosynthetic acclimation occurred when CO2

was elevated, but acclimation was far less severe with both 

elevated CO2 and a 4oC increase in air temperature (Oechel 

et al., 1994). It was hypothesized that soil warming relieved 

a severe nutrient limitation on photosynthesis by increasing 

nitrogen mineralization.

A consistent response to elevated CO2-enhanced photosynthesis in wetlands is an increase in CH4 emissions ranging 

from 50 to 350% (Megonigal and Schlesinger, 1997; Vann 

and Megonigal, 2003). It is generally assumed that the increased supply of plant photosynthate stimulates anaerobic 

microbial carbon metabolism, of which CH4 is a primary 

end product. An increase in CH4 emissions from wetlands 

due to elevated CO2 constitutes a positive feedback on radiative forcing because CO2 is rapidly converted to a more 

effective GHG (CH4).

An elevated CO2-induced increase in CH4 emissions may 

be offset by an increase in carbon sequestration in soil organic matter or wood. Although there are very little data to 

evaluate this hypothesis, a study on seedlings of a wetlandadapted tree species reported that elevated CO2 stimulated 

photosynthesis and CH4 emissions, but not growth, under 

flooded conditions (Megonigal et al., 2005). It is possible 

that elevated CO2 will stimulate soil carbon sequestration, 

particularly in tidal wetlands experiencing sea level rise, 

but a net loss of soil carbon is also possible due to priming 

effects (i.e., increased labile carbon inputs from elevated 

CO2 enhance decomposition of the overall soil carbon pool) 

(Hoosbeek et al., 2004; Lichter et al., 2005). Elevated CO2

has the potential to influence the carbon budgets of adjacent 

aquatic ecosystems by increasing export of dissolved organic 

carbon (Freeman et al., 2004) and dissolved inorganic carbon (Marsh et al., 2005).

Other important anthropogenic forcing factors that will 

affect future CH4 emissions include atmospheric sulfate 

deposition (Vile et al., 2003; Gauci et al., 2004) and nutrient additions (Keller et al., 2005). These external forcing 

factors in turn will interact with internal ecosystem constraints such as pH and carbon quality (Moore and Roulet, 

1995; Bridgham et al., 1998), anaerobic carbon flow (Hines 

and Duddleston, 2001), and net ecosystem productivity and 

plant community composition (Whiting and Chanton, 1993; 

Updegraff et al., 2001; Strack et al., 2004) to determine the 

actual response.

13.4 OPTIONS FOR MANAGEMENT 

Wetland policies in the United States and Canada are driven 

by a variety of federal, state or provincial, and local laws and 

regulations in recognition of the many wetland ecosystem 

services and large historical loss rates (Lynch-Stewart et al., 

1999; National Research Council, 2001; Zedler and Kercher, 

2005). Thus, any actions to enhance the ability of wetlands 

to sequester carbon, or reduce their CH4 emissions, must be 

implemented within the context of the existing regulatory 

framework. The most important option in the United States 

has already been largely achieved, and that is to reduce the 

historical rate of peatland losses with their accompanying 

large oxidative losses of the stored soil carbon. Decreases 

in the rates of loss of all wetlands have helped to maintain 

their soil carbon sequestration potential.

There has been strong interest expressed in using carbon 

sequestration as a rationale for wetland restoration and creation in the United States, Canada, and elsewhere (Wylynko, 

1999; Watson et al., 2000). However, high CH4 emissions 

from conterminous United States’ wetlands suggest that 

creating and restoring wetlands may increase net radiative 

forcing, although adequate data do not exist to fully evaluate 

this possibility. Roulet (2000) came to a similar conclusion 

concerning the restoration of Canadian wetlands. Net radiative forcing from restoration will likely vary among different 

kinds of wetlands and the specifics of their carbon budgets. 

The possibility of increasing radiative forcing by creating 

or restoring wetlands does not apply to estuarine wetlands, 

which emit relatively little CH4 compared to the carbon 

they sequester. Restoration of drained peatlands may stop 

the rapid loss of their soil carbon, which may compensate 

for increased CH4 emissions. However, Canadian peatlands 

restored from peat extraction operations increased their net 

emissions of carbon because of straw addition during the 

restoration process, although it was assumed that they would 

eventually become a net sink (Cleary et al., 2005).

Regardless of their internal carbon balance, the area of restored wetlands is currently too small to form a significant 

carbon sink at the continental scale. Between 1986 and 1997, 
1447

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

only 4157 km2 of uplands were converted into wetlands in 

the conterminous United States (Dahl, 2000). Using the soil 

carbon sequestration rate of 3.05 Mg C per hectare per year 

found by Euliss et al. (2006) for restored prairie pothole 

wetlands3, we estimate that wetland restoration in the United 

States would have sequestered 1.3 Mt C over this 11-year period. However, larger areas of wetland restoration may have 

a significant impact on carbon sequestration. A simulation 

model of planting 20,000 km2 into bottomland hardwood 

trees as part of the Wetland Reserve Program in the United 

States showed a sequestration of 4 Mt C per year through 

2045 (Barker et al., 1996). Euliss et al. (2006) estimated 

that if all cropland on former prairie pothole wetlands in 

the United States and Canada (162,244 km2) were restored 

that 378 Mt C would be sequestered over 10 years in soils 

and plants. However, neither study accounted for the GWP 

of increased CH4 emissions.

Potentially more significant is the conversion of wetlands 

from one type to another; for example, 8.7% (37,200 km2) 

of the wetlands in the conterminous United States in 1997 

3

 Euliss et al. (2006) regressed surface soil carbon stores in 27 

restored semi-permanent prairie pothole wetlands against years since 

restoration to derive this estimate (r2

 = 0.31, P = 0.002). However, there 

was no significant relationship in seasonal prairie pothole wetlands 

(r2

 = 0.04, P = 0.241).

were in a previous wetland category in 1986 (Dahl, 2000). 

The net effect of these conversions on wetland carbon fluxes 

is unknown. Similarly, Roulet (2000) argued that too many 

uncertainties exist to include Canadian wetlands in the 

Kyoto Protocol.

In summary, North American wetlands form a very large 

carbon pool, primarily because of storage as peat, and are a 

small-to-moderate carbon sink (excluding CH4 effects). The 

largest unknown in the wetland carbon budget is the amount 

and significance of sedimentation in FWMS and estuarine 

wetlands, and CH4 emissions in freshwater wetlands. With 

the exception of estuarine wetlands, CH4 emissions from 

wetlands may largely offset any positive benefits of carbon 

sequestration in soils and plants. Given these conclusions, 

it is probably unwarranted to use carbon sequestration as 

a rationale for the protection and restoration of FWMS 

wetlands, although the many other ecosystem services that 

they provide justify these actions. However, protecting and 

restoring peatlands will stop the loss of their soil carbon 

(at least over the long term) and estuarine wetlands are an 

important carbon sink given their limited areal extent and 

low CH4 emissions.

The most important areas for further scientific research in 

terms of current carbon fluxes in the United States are to 

establish an unbiased, 

landscape-level sampling scheme to determine sediment carbon 

sequestration in FWMS 

and estuarine wetlands 

and additional measurements of annual CH4

emissions to better constrain these important fluxes. It would also be beneficial 

if the approximately decadal National Wetland Inventory 

(NWI) status and trends data were collected in sufficient 

detail with respect to the Cowardin et al. (1979) classification 

scheme to determine changes among mineral-soil wetlands 

and peatlands.

Canada lacks any regular inventory of its wetlands, and thus, 

it is difficult to quantify land-use impacts upon their carbon 

fluxes and pools. While excellent scientific data exists on 

most aspects of carbon cycling in Canadian peatlands, Canadian FWMS and estuarine wetlands have been relatively 

poorly studied, despite having suffered large proportional 

losses to land-use change. Wetland data for Mexico is almost 

entirely lacking. Thus, anything that can be done to improve 

upon this would be helpful. All wetland inventories should 

consider the area of estuarine mud flats, which have the 

potential to sequester considerable carbon and are poorly 

understood with respect to carbon sequestration.

Larger areas of wetland 

restoration may have a significant 

impact on carbon sequestration, 

but may also increase methane 

emissions offsetting any positive 

greenhouse gas effects.
The U.S. Climate Change Science Program Chapter 13

148 

recent references. R. Kelman Wieder provided useful initial 

information on peatlands in Canada. Comments of two 

anonymous reviewers and Shuguang Liu (USGS Center for 

Earth Resources Observation and Science) greatly improved 

this manuscript.

The greatest unknown is how global change will affect the 

carbon pools and fluxes of North American wetlands. We 

will not be able to accurately predict the role of North American wetlands as potential positive or negative feedbacks to 

anthropogenic climate change without knowing the integrative effects of changes in temperature, precipitation, atmospheric CO2 concentrations, and atmospheric deposition of 

nitrogen and sulfur within the context of internal ecosystem 

drivers of wetlands. To our knowledge, no manipulative 

experiment has simultaneously measured more than two of 

these perturbations in any North American wetland, and few 

have been done at any site. Modeling expertise of the carbon 

dynamics of wetlands has rapidly improved in the last few 

years (Frolking et al., 2002; Zhuang et al., 2004, and references therein), but this needs even further development in 

the future, including for FWMS and estuarine wetlands.

ACKNOWLEDGMENTS

Steve Campbell (U.S. Department of Agriculture [USDA] 

Natural Resource Conservation Service [NRCS], OR) 

synthesized the National Soil Information database so that 

it was useful to us. Information on wetland soils within 

specific states was provided by Joseph Moore (USDA 

NRCS, AK), Robert Weihrouch (USDA NRCS, WI), and 

Susan Platz (USDA NRCS, MN). Charles Tarnocai provided 

invaluable data on Canadian peatlands. Thomas Dahl 

(U.S. Fish and Wildlife Service) explored the possibility 

of combining NWI data with United States’ soils maps. 

Nigel Roulet (McGill University) gave valuable advice on 
The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

Human Settlements and the North 

American Carbon Cycle

CHAPTER

14

149

Lead Authors: Diane E. Pataki, Univ. Calif., Irvine

Contributing Authors: Alan S. Fung, Dalhousie Univ.; David J. Nowak, 

USDA Forest Service; E. Gregory McPherson, USDA Forest Service; 

Richard V. Pouyat, USDA Forest Service; Nancy Golubiewski, Landcare 

Research; Christopher Kennedy, Univ. Toronto; Patricia Romero 

Lankao, NCAR and UAM-Xochimilco; Ralph Alig, USDA Forest 

Service

KEY FINDINGS

Human settlements occupy almost 5% of the North American land area.

There is currently insufficient information to determine the complete carbon balance of human settlements in 

North America. Fossil-fuel emissions, however, very likely dominate carbon fluxes from settlements.

An estimated 410 to 1679 million tons of carbon are currently stored in the urban tree component of North 

American settlements. The growth of urban trees in North America produces a sink of approximately 16 to 49 

million tons of carbon per year, which is 1 to 3% of the fossil-fuel emissions from North America in 2003.

Estimates of historical trends of the net carbon balance of North American settlements are not available. Fossil-fuel emissions have likely gone up with the growth of urban lands, but the net balance of carbon loss during 

conversion of natural to urban or suburban land cover and subsequent uptake by lawns and urban trees is highly 

uncertain.

The density and development patterns of human settlements are drivers of fossil-fuel emissions, especially in 

the residential and transportation sectors. Biological carbon gains and losses are influenced by type of predevelopment land cover, post-development urban design and landscaping choices, soil and landscape management 

practices, and the time since land conversion.

Projections of future trends in the net carbon balance of North American settlements are not available. However, the projected expansion of urban areas in North America will strongly impact the future North American 

carbon cycle as human settlements affect (1) the direct emission of carbon dioxide from fossil-fuel combustion, 

(2) plant and soil carbon cycling in converting wildlands to residential and urban land cover.

A number of municipalities in Canada, Mexico, and the United States have made commitments to voluntary 

greenhouse gas emission reductions under the Cities for Climate Protection program of International 

Governments for Local Sustainability (formerly the 

International Council for Local Environmental Initiatives [ICLEI]). Reductions have in some cases been 

associated with improvements in air quality.

Research is needed to improve comprehensive carbon 

inventories for settled areas, to improve understanding 

of how development processes relate to driving forces 

for the carbon cycle, and to improve linkages between 

understanding of human and environmental systems 

in settled areas.

•

•

•

•

•

•

•

•
The U.S. Climate Change Science Program Chapter 14

150 

14.1 BACKGROUND

Activities in human settlements form the basis for much of 

North America’s contribution to global carbon dioxide (CO2) 

emissions. Settlements such as cities, towns, and suburbs 

vary widely in density, form, and distribution. Urban settlements, as they have been defined by the census bureaus of 

the United States, Canada, and Mexico, make up approximately 75 to 80% of the population of the continent, and this 

proportion is projected to continue to increase (United Nations, 2004). The density and forms of new development will 

strongly impact the future trajectory of the North American 

carbon cycle as human settlements affect the carbon cycle 

by (1) direct emission of CO2 from fossil-fuel combustion, 

(2) alterations to plant and soil carbon cycles in conversion 

of wildlands to residential and urban land cover, and (3) indirect effects of residential and urban land cover on energy 

use and ecosystem carbon cycling.

14.2 CARBON INVENTORIES OF HUMAN 

SETTLEMENTS

Conversion of agricultural and wildlands to settlements 

of varying densities is occurring at a rapid rate in North 

America, faster, in fact, than the rate of population growth. 

For example, according to U.S. Census Bureau estimates, 

urban land in the coterminous United States 

increased by 23% in 

the 1990s (Nowak et 

al., 2005) while the 

population increased 

by 13%.1† Given these 

trends, it is important 

to determine the carbon balance of different 

1 † A dagger symbol indicates that the magnitude and/or range of uncertainty for the given numerical value(s) is not provided in the references cited.

types of settlements and how future urban policy and planning may impact the magnitude of CO2 sources and sinks 

at regional, continental, and global scales. However, unlike 

many other types of common land cover, complete carbon 

inventories including fossil-fuel emissions and biological 

sources and sinks of carbon have been conducted only rarely 

for settlements as a whole. Assessing the carbon balance of 

settlements is challenging, as they are characterized by large 

CO2 emissions from fuel combustion and decomposition of 

organic waste as well as transformations to vegetation and 

soil that affect carbon sources and sinks.

Determining the extent of human settlements across North 

America also presents a challenge, as definitions of “developed,” “built-up,” and “urban” land vary greatly, particularly 

among nations. The U.S., Canadian, and Mexican census 

definitions are not consistent; in addition, several other 

classification schemes for defining and mapping settlements have been developed, such as the U.S. Department 

of Agriculture’s National Resource Inventory categorization of developed land, which uses a variety of methods 

based on satellite imagery and ground-based information. 

One method of classifying settled land cover that has been 

consistently applied at a continental scale is the Global Rural-Urban Mapping Project conducted by a consortium of 

institutions, including Columbia University and the World 

Bank (CIESIN et al., 2004). This estimate, which is based on 

nighttime lights satellite imagery, is 1,039,450 km2

, almost 

5% of the total continental land area (Figure 14.1).†

Currently, there is insufficient information to determine 

the complete current or historical carbon balance of total 

continental land area. Fossil-fuel emissions very likely 

dominate carbon fluxes from settlements, just as settlement-related emissions likely dominate total fossil-fuel 

consumption in North America. However, specific estimates 

of the proportion of total fossil-fuel emissions 

directly attributable to settlements are difficult to 

make given current inventory methods, which are 

often conducted on a state or province-wide basis. 

In addition, the biological component of the carbon 

balance of settlements is highly uncertain, particularly with regard to the influence of urbanization 

on soil carbon pools and biogenic greenhouse gas 

emissions.

For the urban tree component of the settlement carbon balance, carbon stocks and sequestration have 

been estimated for urban land cover (as defined by 

the U.S. Census Bureau) in the coterminous United 

States to be on the order of 700 million tons (Mt) 

(335-980 million metric tons of carbon [Mt C]) 

with sequestration rates of 22.8 Mt C per year (13.7-25.9 

Mt C per year) (Nowak and Crane, 2002). These estimates 

Conversion of agricultural and 

wildlands to settlements of 

varying densities is occurring 

at a rapid rate in North 

America, faster, in fact, than the 

rate of population growth.
151

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

encompass a great deal of regional variability and contain 

some uncertainty about differences in carbon allocation 

between urban and natural trees, as urban trees have been 

less studied. However, to a first approximation, these estimates can be used to infer a probable range of urban tree 

carbon stocks and gross sequestration on a continental basis. 

Nowak and Crane (2002) estimated that urban tree carbon 

storage in the Canadian border states (excluding semi-arid 

Montana, Idaho, and North Dakota) ranged from 24 to 45 

tons of carbon per hectare (t C per ha), and carbon sequestration ranged from 0.8 to 1.5 t C per ha per year. Applying 

these values to a range of estimates of the extent of urban 

Figure 14.1 North America urban extents.
The U.S. Climate Change Science Program Chapter 14

152 

land in Canada (28,045 km2 from the 1996 Canadian Census and 131,560 km2

 from CIESIN et al., 2004), Canadian 

urban forest carbon stocks are between 67 and 592 Mt while 

carbon sequestration rates are between 2.2 and 19.7 Mt C 

per year. Similarly, for Mexico, Nowak and Crane (2002) 

estimated that urban carbon storage and sequestration in 

the U.S. southwestern states varied from 4.4 to 10.5 t per 

ha and 0.1 to 0.3 t per ha per year, respectively, leading to 

estimates of 10 to 107 Mt C stored in urban trees in Mexico 

and 0.2 to 3.1 Mt C per year sequestered. In this analysis, 

urban “trees” were defined as vegetation with woody stems 

greater than 1 inch diameter as measured 4.5 feet from the 

ground; carbon storage of other types of urban vegetation 

is not included in these estimates. Estimates of historical 

trends are not available.

While complete national or continental-scale estimates of 

the carbon budget of 

settlements including fossil fuels, vegetation, and soils are 

not available, several 

methods are available 

to assess the full carbon balance of individual settlements 

and can be applied in the next several years toward constructing larger-scale inventories. Atmospheric measurements can be used to determine the net losses of carbon 

from settlements and urbanizing regions (Grimmond et al., 

2002; Grimmond et al., 2004; Nemitz et al., 2002; Soegaard 

and Moller-Jensen, 2003). Specific sources of CO2 can be 

determined from unique isotopic signatures (Pataki et al., 

2003; Pataki et al., 2006b) and from the relationship between CO2 and carbon monoxide (Lin et al., 2004). Many 

of these techniques have been commonly applied to natural 

ecosystems and may be easily adapted for settled regions. In 

addition, there have been several attempts to 

quantify the “metabolism” of human settlements in terms of their inputs and outputs of 

energy, materials, and wastes (Decker et al., 

2000) and the “footprint” of settlements in 

terms of the land area required to supply their 

consumption of resources and to offset CO2

emissions (Folke et al., 1997). Often these 

calculations include local flows and transformations of materials as well as upstream 

energy use and carbon appropriation, such as 

remote electrical power generation and food 

production.

To conduct metabolic and footprint analyses 

of specific settlements, energy and fuel use 

statistics are needed for individual municipalities, and these data are seldom made available at that 

scale. Consequently, metabolic and footprint analyses of 

carbon flows and conversions associated with metropolitan 

regions have been conducted for a relatively small number 

of cities. A metabolic analysis of the Toronto metropolitan 

region showed per capita net CO2 emissions of 14 t CO2 per 

year † (Sahely et al., 2003), higher than analyses of other large 

metropolitan areas in developed countries (Newman, 1999; 

Pataki et al., 2006a; Warren-Rhodes and Koenig, 2001). In 

contrast, an analysis of Mexico City estimated per capita 

CO2 emissions of 3.4 t CO2 per year † (Romero Lankao et 

al., 2004). Local emissions inventories can provide useful 

supplements to national and global inventories in order to 

ensure that emissions reductions policies are applied effectively and equitably (Easterling et al., 2003). A detailed 

review of methodological uncertainties and research needs 

is given in Pataki et al. (2006b).

Current projections for urban land development in North 

America highlight the importance of improving carbon 

inventories of settlements and assessing patterns and impacts of future urban and rural development. Projections for 

increases in the extent of developed, nonfederal land cover 

in the United States in the next 25 years are as high as 79%, 

which would increase the proportion of developed land from 

5.2% to 9.2% of total land cover (Alig et al., 2004). The 

potential consequences of this increase for the carbon cycle 

are significant in terms of CO2 emissions from an expanded 

housing stock and transportation network as well as from 

conversion of agricultural land, forest, rangeland, and other 

ecosystems to urban land cover. Because the dynamics of 

carbon cycling in settled areas encompass a range of physical, biological, social, and economic processes, studies of 

the potential impacts of future development on the carbon 

cycle must be interdisciplinary. Large-scale research on what 

has been called the study “of cities as ecosystems” (Pickett 

et al., 2001) has begun only relatively recently, pioneered 

Projections for increases in the 

extent of developed, nonfederal land 

cover in the United States in the 

next 25 years would increase the 

proportion of developed land from 

5.2% to 9.2% of total land cover.
153

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

by interdisciplinary studies such as the National Science 

Foundation’s Long-Term Ecological Research sites in the 

central Arizona-Phoenix area and in Baltimore (Grimm 

et al., 2000). Although there is not yet sufficient data to 

construct a complete carbon inventory of settlements across 

North America, it is a feasible research goal to do so in the 

next several years if additional studies in individual municipalities are conducted in a variety of urbanizing regions.

14.3 TRENDS AND DRIVERS

Drivers of change in the carbon cycle associated with human settlements include (1) factors that influence the rate 

of land conversion and urbanization, such as population 

growth and density, household size, economic growth, and 

transportation infrastructure; (2) additional factors that 

influence fossil-fuel emissions, such as climate, residence 

and building characteristics, transit choices, and affluence; 

and (3) factors that influence biological carbon gains and 

losses, including the type of predevelopment land cover, 

post-development urban design and landscaping choices, 

soil and landscape management practices, and the time since 

land conversion.

14.3.1 Fossil-fuel Emissions

The density and patterns of development of human settlements (i.e., their “form”) are drivers of the magnitude of the 

fossil-fuel emissions component of the carbon cycle. The 

size and number of residences and households influence 

CO2 emissions from the residential sector, and the spatial 

distribution of residences, commercial districts, and transportation networks is a key influence in the 

vehicular and transportation sectors. Many 

of the attributes of urban form that influence 

the magnitude of fossil-fuel emissions are 

linked to historical patterns of economic development, which have differed in Canada, 

the United States, and Mexico. The future 

trajectory of development and associated 

levels of affluence and technological and 

social change will strongly influence key 

aspects of urban form such as residence size, vehicle miles 

traveled, and investment in urban infrastructure, along with 

associated fossil-fuel emissions. Whereas emissions from 

the transportation and residential sectors are discussed in 

detail in Chapters 7 

and 9, respectively, 

this chapter discusses 

specific aspects of the 

form of human settlements that affect the 

current continental 

carbon balance and 

its possible future trajectories.

Household size in terms of the number of occupants per 

household has been declining in North America (Table 14.1) 

while the average size of new residences has been increasing. 

For example, the average size of new, single family homes in 

the United States increased from 139 m2

 (1500 ft2) to more 

than 214 m2 (2300 ft2) between 1970 and 2004 (NAHB, 

2005). These trends have contributed to increases in per 

capita CO2 emissions from the residential sector as well as 

increases in the consumption of land for residential and urban development (Alig et.al., 2003; Ironmonger et al., 1995; 

Liu et al., 2003; MacKellar et al., 1995). In addition, when 

considering total emissions from settlements, the trajectory 

of the transportation and residential sectors may be linked. 

There have been a number of qualitative discussions of the 

role of “urban sprawl” in influencing fossil-fuel and pollutant emissions from cities (CEC, 2001; Gonzalez, 2005), 

although definitions of urban sprawl vary (Ewing et 

al., 2003). Quantitative linkages between urban form 

and energy use have been attempted by comparing 

datasets for a variety of cities, but the results have 

been difficult to interpret due to the large number of 

factors that may affect transportation patterns and 

energy consumption (Anderson et al., 1996). For 

example, in a seminal analysis of data from a variety of cities, Kenworthy and Newman (1990) found 

a negative correlation between population density 

and per capita energy use in the transportation sector. However, their data have been reanalyzed and 

reinterpreted in a number of subsequent studies that 

Total Population (%) Households (%)

Canada 19 39

Mexico 33 60

United States 15 25

Table 14.1 Increases in number of households and the total 

population of the United States, Canada, and Mexico between 1985 

and and 2000. (United Nations, 2002; United Nations 

Habitat, 2003).

Although there is not yet sufficient 

data to construct a complete 

carbon inventory of settlements 

across North America, it is a 

feasible research goal to do so 

in the next several years.
The U.S. Climate Change Science Program Chapter 14

154 

have highlighted other important driving variables, such as 

income levels, employment density, and transit choice (Gomez-Ibanez, 1991; Gordon and Richardson, 1989; Mindali 

et al., 2004).

Quantifying the nature and extent of the 

linkage between development patterns 

of human settlements 

and greenhouse gas 

emissions is critical 

from the perspective 

of evaluating the potential impacts of land-use policy. One way forward is to 

further the application of integrated land-use and transportation models that have been developed to analyze future 

patterns of urban development in a variety of cities (Agarwal 

et al., 2000; EPA, 2000; Hunt et al., 2005). Only a handful 

have been applied to date for generating fossil-fuel emissions 

scenarios from individual metropolitan areas (Jaccard et al., 

1997; Pataki et al., 2006a), such that larger-scale national or 

continental projections for human settlements are not currently available. However, there is potential to add a carbon 

cycle component to these models that would assess the linkages between land-use and land-cover change, residential 

and commercial energy use and emissions, emissions from 

the transportation sector, and net carbon gains and losses in 

biological sinks following land conversion. A critical feature 

of these models is that they may be used to evaluate future 

scenarios and the potential impacts of policies to influence 

land-use patterns and transportation networks in individual 

settlements and developing regions.

14.3.2 Vegetation and Soils in 

Human Settlements

Human settlements contain vegetation and soils that are 

often overlooked in national inventories, as they fall outside 

common classification schemes. Nevertheless, patterns of 

development affect the carbon balance of biological systems, 

both in the replacement of natural ecosystems with rural, 

residential, or urban land cover and in processes 

within settlements that affect constructed and managed land cover. In the United States, satellite data 

and ecosystem modeling for the mid-1990s suggested 

that urbanization occurred largely on productive agricultural land and therefore caused a net loss of carbon 

fixed by photosynthesis of 40 Mt C 

per year † (Imhoff 

et al., 2004).

Urban forests and vegetation sequester carbon directly as 

described under carbon inventories. In addition, urban trees 

influence the carbon balance of municipalities indirectly 

through their effects on energy use. Depending on their 

placement relative to buildings, trees may cause shading 

and windbreak effects, as well as evaporative cooling due to 

transpiration (Akbari, 2002; Oke, 1989; Taha, 1997). These 

effects have been estimated in a variety of studies, mostly 

involving model calculations that suggest that urban trees 

generally result in net reductions in energy use (Akbari, 

2002; Akbari and Konopacki, 2005; Akbari et al., 1997; 

Akbari and Taha, 1992; Huang et al., 1987). Taking into 

account CO2 emissions resulting from tree maintenance 

and decomposition of removed trees, “avoided” emissions 

from energy savings were responsible for approximately 

half of the total net reduction in CO2 emissions from seven 

municipal urban forests, with the remainder attributable 

to direct sequestration of CO2 (McPherson et al., 2005). 

Direct measurements of meteorological fluxes that quantify 

the contribution of vegetation are needed to validate these 

estimates.

Like natural ecosystems, soils in human settlements contain 

carbon, although rates of sequestration are much more uncertain in urban soils than in natural soils. In general, soil 

carbon is lost following disturbances associated with conversion from natural to urban or suburban land cover (Pouyat 

et al., 2002). Soil carbon pools may subsequently increase at 

varying rates, depending on the soil and land cover type, local climate, and management intensity (Golubiewski, 2006; 

Pouyat et al., 2002; Qian and Follet, 2002). In ecosystems 

with low rates of carbon sequestration in native soil such as 

arid and semi-arid ecosystems, conversion to highly managed, settled land cover can result in higher rates of carbon 

sequestration and storage than pre-settlement due to large 

inputs of water, fertilizer, and organic matter (Golubiewski, 

2006). Pouyat et al. (2006) used urban soil organic carbon 

measurements to estimate the total above- and below-ground 

carbon storage, including soil carbon, in U.S. urban land 

cover to be 2,640 Mt (1,890 to 3,300 Mt). This range does 

not include the uncertainty in classifying urban land cover, 

Urban trees generally result in 

net reductions in energy use.

Quantifying the nature and 

extent of the linkage between 

development patterns of human 

settlements and greenhouse gas 

emissions is critical from the 

perspective of evaluating the 

potential impacts of land-use policy.
155

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

but applies the range of uncertainty in above-ground urban 

carbon stocks reported in Nowak and Crane (2002) and the 

standard deviation of urban soil carbon densities reported 

in Pouyat et al. (2006). In addition, irrigated and fertilized 

urban soils have been associated with higher emissions of 

CO2 and the potent greenhouse gas nitrous oxide (N2O) 

relative to natural soils, offsetting some potential gains of 

sequestering carbon in urban soils (Kaye et al., 2004; Kaye et 

al., 2005; Koerner and Klopatek, 2002). Finally, full carbon 

accounting that incorporates fossil-fuel emissions associated 

with soil management (e.g., irrigation and fertilizer production and transport) has not yet been conducted. In general, 

additional data on soil carbon balance in human settlements 

are required to assess the potential for managing urban and 

residential soils for carbon sequestration.

14.4 OPTIONS FOR MANAGEMENT

A number of municipalities in Canada, the United States, 

and Mexico have committed to voluntary programs of greenhouse gas emissions reductions. Under the Cities for Climate 

Protection program (CCP) of International Governments 

for Local Sustainability (ICLEI, formerly the International 

Council of Local Environmental Initiatives) 269 towns, 

cities, and counties in North America have committed to 

conducting emissions inventories, establishing a target for 

reductions, and monitoring the results of reductions initiatives (the current count of the number of municipalities participating in voluntary greenhouse gas reduction programs 

may be found on-line at http://www.iclei.org). Emissions 

reductions targets vary by municipality, as do the scope of 

reductions, which may apply to the municipality as a whole 

or only to government operations (i.e., emissions related to 

operation of government-owned buildings, facilities, and 

vehicle fleets).

Kousky and Schneider (2003) interviewed representatives 

from 23 participating CCP municipalities in the United 

States who indicated that cost savings and other co-benefits 

of greenhouse gas reductions in cities and towns were the 

most commonly cited reasons for participating in voluntary greenhouse gas reductions programs. Potential cost 

savings include reductions in energy and fuel costs from 

energy efficiency programs in buildings, street lights, and 

traffic lights; energy cogeneration in landfills and sewage 

treatment plants; mass transit programs; and replacement of 

municipal vehicles and buses with alternative fuel or hybrid 

vehicles (ICLEI, 1993; 2000). Other perceived co-benefits 

include reductions in emissions of particulate and oxidant 

pollutants, alleviation of traffic congestion, and availability 

of lower-income housing in efforts to curb urban sprawl. 

These co-benefits are often “perceived” because many 

municipalities have not attempted to quantify them as part 

of their emissions reductions programs (Kousky and Schneider, 2003); however, it has been suggested that they play a 

key role in efforts to promote reductions of municipal-scale 

greenhouse gas emissions because local constituents regard 

them as an issue of interest (Betsill, 2001).

Of the co-benefits of municipal programs to reduce CO2

emissions, improvements in air quality are perhaps the 

most well studied. Cifuentes (2001) analyzed the benefits 

of reductions in atmospheric particulate matter measuring 

less than 10 micrometers (μm) in diameter (PM10) and ozone 

concentrations in four 

cities in North and 

South America. Using a greenhouse gas 

reduction of 13% of 

2000 levels by 2020 

from energy efficiency and fuel substitution programs, 

Cifuentes (2001) estimated that PM10 and ozone concentrations would decline 

by 10% of 2000 levels. Estimated health benefits from such 

a reduction included avoidance of 64,000 (18,000-116,000) 

premature deaths associated with air quality-related heath 

problems as well as avoidance of 91,000 (28,000-153,000) 

hospital admissions and 787,000 (136,000-1,430,000) 

emergency room visits. However, using calculations for 

co-control of CO2 and air pollutants in Mexico City, West 

et al. (2004) found that in practice, if electrical energy is 

primarily generated in remote locations relative to the urban 

area, cost-effective energy efficiency programs may have 

a relatively small effect on air quality. In that case, options 

for reducing greenhouse gas emissions would have to be 

implemented primarily in the transportation sector to appreciably affect air quality.

Two hundred and sixty nine towns, 

cities, and counties in North America 

have committed to conducting 

emissions inventories, establishing a 

target for reductions, and monitoring 

the results of reductions initiatives.
The U.S. Climate Change Science Program Chapter 14

156 

14.5 RESEARCH NEEDS

Additional studies of the carbon balance of settlements of 

varying densities, geographical location, and patterns of 

development are needed to quantify the potential impacts of 

various policy and planning alternatives on net greenhouse 

gas emissions. While it may seem intuitive that policies to 

curb urban sprawl or enhance tree planting programs will 

result in emissions reductions, different aspects of urban 

form (e.g., housing density, availability of public transportation, type and location of forest cover) may have different 

net effects on carbon sources and sinks, depending on the 

location, affluence, economy, and geography of various 

settlements. It is possible to develop quantitative tools to take 

many of these factors into account. To facilitate development 

and application of integrated urban carbon cycle models 

and to extrapolate local studies to regional, national, and 

continental scales, useful additional data include: • common land cover classifications appropriate for characterizing a variety of human settlements across North 

America,

•emissions inventories at small spatial scales such as 

individual neighborhoods and municipalities,

•expansion of the national carbon inventory and flux 

measurement networks to include land cover types within 

human settlements,

•comparative studies of processes and drivers of development in varying regions and nations, and

•interdisciplinary studies of land-use change that evaluate 

socioeconomic as well as biophysical drivers of carbon 

sources and sinks.

In general, there has been a focus in carbon cycle science on 

measuring carbon stocks and fluxes in natural ecosystems, 

and consequently highly managed and human-dominated 

systems such as settlements have been underrepresented 

in many regional and national inventories. To assess the 

full carbon balance of settlements ranging from rural developments to large cities, a wide range of measurement 

techniques and scientific, economic, and social science 

disciplines are required to understand the dynamics of urban 

expansion, transportation, economic development, and biological sources and sinks. An advantage to an interdisciplinary focus on the study of human settlements from a carbon 

cycle perspective is that human activities and biological 

impacts in and surrounding settled areas encompass many 

aspects of perturbations to atmospheric CO

2, including a 

large proportion of national CO

2 emissions and changes in 

carbon sinks resulting from land-use change.
The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

Coastal Oceans

CHAPTER

15

157

Lead Authors: Francisco P. Chavez, MBARI; Taro Takahashi, 

Columbia Univ.

Contributing Authors: Wei-Jun Cai, Univ. Ga.; Gernot Friederich, 

MBARI; Burke Hales, Oreg. State Univ.; Rik Wanninkhof, NOAA; 

Richard A. Feely, NOAA

KEY FINDINGS

The combustion of fossil fuels has increased carbon dioxide in the atmosphere, and the oceans have annually 

absorbed an equivalent of 20-30% of the carbon dioxide in fossil-fuel emissions. The present annual uptake 

by the oceans of approximately 1.8 billion tons of carbon (26% of global fossil-fuel emissions in 2003) is well 

constrained, has slightly acidified the oceans and may ultimately affect ocean ecosystems in unpredictable 

ways.

The carbon budgets of ocean margins (coastal regions) are not as well-characterized due to lack of 

observations coupled with complexity and highly localized geographic variability. Existing data are 

insufficient, for example, to estimate the amount of carbon derived from human activity stored in the 

coastal regions of North America or to predict future scenarios.

New air-sea carbon flux observations reveal that on average, waters within about 100 km (60 miles) of the 

shores surrounding North America are neither a source nor a sink of carbon dioxide to the atmosphere. 

A small net source of carbon dioxide to the atmosphere of 19 million tons of carbon per year (with large 

uncertainty) is estimated mostly from waters around the Gulf of Mexico and the Caribbean Sea. This is 

equivalent to about 1% of the global ocean uptake.

With the exception of one or two time-series sites, almost nothing is known about historical trends in airsea fluxes and the source-sink behavior of North America’s coastal oceans.

The Great Lakes and estuarine systems of North America may be net sources of carbon dioxide where 

terrestrially-derived organic material is decomposing, while reservoir systems may be storing carbon 

through sediment transport and burial.

Options for sequestering carbon in the ocean include iron fertilization in sunlit surface waters and injection 

of carbon dioxide in subsurface coastal waters. However, sequestration capacity and potential adverse 

effects on marine environments need to be investigated. 

Highly variable air-sea carbon dioxide fluxes in coastal areas may introduce errors in North American 

carbon dioxide fluxes calculated by atmospheric inversion methods. Reducing these errors and the 

uncertainties regarding the variability of carbon cycling in coastal oceans will require observation systems 

utilizing fixed and mobile platforms, novel instrumentation to measure critical stocks and fluxes, and 

coordinated national and international research programs. Experimental studies involving coastal carbon 

cycling should be encouraged. 

•

•

•

•

•

•

•
The U.S. Climate Change Science Program Chapter 15

158 

15.1 INVENTORIES 

(STOCKS AND FLUXES, 

QUANTIFICATION)

This chapter 

first introduces the role the 

ocea ns play 

in modulating 

at mospheric 

carbon dioxide (CO2), then 

quantifies air-sea CO2 fluxes 

in coastal waters1 surrounding North America and considers how the underlying processes affect the air-sea fluxes. Stocks of living organisms in 

marine environments are small relative to those on land, but 

turnover rates are very high. 

In addition, aquatic stocks 

are not well characterized 

because of their spatial and 

temporal variability, the complexity of carbon compound 

transformations, and limited 

data on these processes. The 

oceans act as a huge reservoir 

1

 “Coastal waters” are the region within 100 km from shore in which 

processes unique to coastal marine environments influence the partial 

pressure of CO2 in surface sea waters. 

for inorganic carbon, containing about 50 times as much 

CO2 as the atmosphere. The ocean’s biological pump converts CO2 to organic particulate carbon by photosynthesis, 

transports the organic carbon from the surface by sinking, 

and therefore plays a critical role in removing atmospheric 

CO2 in combination with physical and chemical processes 

(Gruber and Sarmiento, 2002; Sarmiento and Gruber, 

2006). Atmospheric concentration of CO2 would be much 

higher in the absence of current ocean processes implying 

that climate-driven changes in ocean circulation, chemical 

properties or biological rates could result in strong feedbacks 

to the atmosphere.

The release of CO2 into the atmosphere by the combustion 

of fossil fuels has increased pre-industrial concentrations 

from around 280 ppm to present day 

levels of nearly 380 ppm in 2005. This 

increase in atmospheric concentrations 

is driving CO2 into the ocean with the 

present net air-sea CO2 flux from the 

atmosphere into the ocean well constrained to about 1800 million metric 

tons of carbon (Mt C, See Box 15.1)****

per year (or 1.8 billion tons of carbon 

[Gt C]  per year) (Figure 15.1 and 

Table 15.1) (Chapter 2 for a description 

of how ocean carbon fluxes relate to the 

global carbon cycle). The uptake of this 

human-caused CO2 by the oceans is, on 

average, turning them more acidic with 

negative and potentially catastrophic 

effects on some biota (Kleypas et al., 

2006). The atmosphere is well mixed 

and nearly homogenous so the large 

spatial variability in air-sea CO2 fluxes 

shown in Figure 15.1 is driven by a 

combination of physical, chemical, 

and biological processes in the ocean. 

The flux over the coastal margins 

has neither been well characterized 

(Liu et al., 2000) nor integrated into 

global calculations because there are 

large variations over small spatial and temporal scales, and 

observations have been limited. The need for higher spatial 

Latitude 

bands Pacific Atlantic Indian Southern 

Ocean Global

N of 50°N +0.01 –0.31 –0.30

14°N-50°N –0.49 –0.25 +0.05 –0.69

14°N-14°S +0.65 +0.13 +0.13 +0.91

14°S-50°S –0.39 –0.21 –0.52 –1.12

S of 50°S –0.30 –0.30

Total flux –0.23 –0.64 –0.34 –0.30 –1.50

% of flux 15 42 23 20 100

Area (106

 km2) 152.0 74.6 53.0 41.1 320.7

% of area 47 23 17 13 100

Table 15.1 Climatological mean distribution of the net air-sea CO2 flux (in Gt C per 

year) over the global ocean regions (excluding coastal areas) in reference year 1995. 

The fluxes are based on about 1.75 million partial pressure measurements for CO2

in surface ocean waters, excluding the measurements made in the equatorial Pacific 

(10°N- 10°S) during El Niño periods (see Takahashi et al., 2002). The NCAR/NCEP 

42-year mean wind speeds and the (wind speed)2

 dependence for air-sea gas transfer 

rate are used (Wanninkhof, 1992). Plus signs indicate that the ocean is a source for 

atmospheric CO2, and negative signs indicate that ocean is a sink. The ocean uptake 

has also been estimated on the basis of the following methods: temporal changes in 

atmospheric oxygen and CO2 concentrations (Keeling and Garcia, 2002; Bender et 

al., 2005), 13C/12C ratios in sea and air (Battle et al., 2000; Quay et al., 2003), ocean CO2

inventories (Sabine et al., 2004), and coupled carbon cycle and ocean general circulation models (Sarmiento et al., 2000; Gruber and Sarmiento, 2002). The consensus is 

that the oceans take up 1.3 to 2.3 Gt C per year.

Climate-driven changes in 

ocean circulation, chemical 

properties or biological 

rates could result in strong 

feedbacks to the atmosphere.

The uptake of this humancaused CO2 by the oceans 

is, on average, turning them 

more acidic with negative 

and potentially catastrophic 

effects on some biota.

BOX 15.1: CCSP SAP 2.2 Uncertainty Conventions

** *** = 95% certain that the actual value is within 10% of the estimate reported, 

  = 95% certain that the estimate is within 25%, 

** * = 95% certain that the estimate is within 50%, 

** = 95% certain that the estimate is within 100%, and

* = uncertainty greater than 100%.

† = The magnitude and/or range of uncertainty for the given numerical 

 value(s) is not provided in the references cited.
159

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

resolution to resolve the coastal variability has hampered 

modeling efforts. In the following sections we review existing information on the coastal ocean carbon cycle and its 

relationship to the global ocean, and we present the results of 

a new analysis of about a half million 

observations of air-sea flux of CO2 in 

coastal waters surrounding the North 

American continent.

15.1.1 Global Coastal 

Ocean Carbon Fluxes

The carbon cycle in coastal oceans involves a series of processes, including 

runoff from terrestrial environments, 

upwelling and mixing of high CO2

water from below, photosynthesis at 

the sea surface, sinking of organic 

particles, respiration, production and 

consumption of dissolved organic 

carbon, and air-sea CO2 fluxes (Figure 

15.2). Although fluxes in the coastal 

oceans are large relative to surface 

area (Muller-Karger et al., 2005), there 

is disagreement as to whether these 

regions are a net sink or a net source 

of CO2 to the atmosphere (Tsunogai et al., 1999; Cai and 

Dai, 2004; Thomas et al., 2004). Great uncertainties remain 

in coastal carbon fluxes, which are complex and dynamic, 

varying rapidly over short distances and at high frequencies. Only recently have new technologies allowed for the 

measurement of these rapidly changing fluxes (Friederich 

et al., 1995 and 2002; Hales and Takahashi, 2004).

Carbon is transported from land to sea mostly by rivers in 

four components: CO2 dissolved in water, organic carbon 

dissolved in water, particulate inorganic carbon (e.g., calcium carbonate [CaCO3]), and particulate organic carbon. 

The global rate of river input has been estimated to be 1000 

Mt C*** per year, about 38% of it as dissolved CO2 (or 384 Mt 

C per year), 25% as dissolved organic matter, 21% as organic 

particles, and 17% as CaCO3 particles (Gattuso et al., 1998). 

Estimates for the riverine dissolved CO2 flux vary from 

385 to 429 Mt C per year (Sarmiento and Sundquist, 1992). 

The Mississippi River, the seventh-largest in freshwater 

discharge in the world, delivers about 13 Mt C*** per year

as dissolved CO2 (Cai, 2003). Organic matter in continental 

Figure 15.1 Global distribution of sea-air CO2 flux. The source areas (cyan-greenyellow-orange) are primarily in the tropics with a few high latitiude areas where 

deep mixing occurs in winter. The sink areas (blue-magenta) are located in mid to 

high latitiudes. The white line represents zero flux. Updated from Takahashi et al.

(2002).

Figure 15.2 Mean air-sea CO2 flux as calculated from shipboard measurements on a line perpendicular to the central California 

coast (top panel). Flux within Monterey Bay (~0-20 km offshore) is into the ocean, flux across the active upwelling region (~20-75 

km offshore) is from the ocean, and flux in the California Current (75-300 km) is on average into the ocean. These fluxes result 

from the processes shown in the bottom panel. California Undercurrent water, which has a high CO2 partial pressure, upwells near 

shore, and is advected offshore into the California Current and into Monterey Bay. Phytoplankton growing in the upwelled water 

use CO2 as a carbon source, and CO2 is drawn to low levels in those areas. Phytoplankton carbon eventually sinks or is subducted 

below the euphotic zone, where it decays, elevating the CO2 levels of subsurface waters. Where the level of surface CO2 is higher 

than the level of atmospheric CO2, diffusion drives CO2 into the atmosphere. Conversely, where the level of surface CO2 is lower 

than that of atmospheric CO2, diffusion drives CO2 into the ocean. The net air-sea flux on this spatial scale is near zero. DIC = 

concentration of inorganic carbon (i.e., all CO2 species) dissolved in seawater. Updated from Pennington et al. (in press).
The U.S. Climate Change Science Program Chapter 15

160 

shelf sediments exhibits only weak isotope and chemical signatures of terrestrial origin, suggesting that riverine organic 

matter is reprocessed in coastal environments on a time scale 

of 20 to 130 years (Hedges et al., 1997; Benner and Opsahl, 

2001). Of the organic carbon, about 30% is accumulating in 

estuaries, marshes, and deltas, and a large portion (20% to 

60%) of the remaining 70% is readily and rapidly oxidized 

in coastal waters (Smith and Hollibaugh, 1993). Only about 

10% is estimated to be contributed by human activities, such 

as agriculture and forest clearing (Gattuso et al., 1998), and 

the rest is a part of the natural carbon cycle.

One of the major differences between coastal and open ocean 

systems is the activity of the biological pump. In coastal 

environments, the pump operates much more efficiently, 

leading to rapid reduction of surface CO2 and thus complicating the accurate quantification of air-sea CO2 fluxes. For 

example, Ducklow and McCallister (2004) constructed a 

carbon balance for the coastal oceans using the framework 

of the ocean carbon cycle of Gruber and Sarmiento (2002) 

and estimated a net CO2 removal by primary productivity 

of 1200 Mt C per year and a large CO2 sink of 900 Mt C per 

year for the atmosphere. In contrast, Smith and Hollibaugh 

(1993) estimated a biological pump of about 200 Mt C per 

year and concluded that the coastal oceans are a weak CO2

sink of 100 Mt C per year, about one-ninth of the estimate by 

Ducklow and McCallister (2004). Since the estimated air-sea 

CO2 flux depends on quantities that are not well constrained, 

the mass balance provides widely varying results. For this 

reason, in this chapter, the net air-sea flux over coastal waters is estimated on the basis of direct measurements of the 

air-sea difference of partial pressure of CO2 (pCO2).

15.1.2 North American Coastal Carbon

Two important types of North American coastal ocean 

environments can be identified: (1) river-dominated coastal 

Location

Surface 

seawater 

pCO2 

(μatm)

Instantaneous 

CO2 flux (mol/

per m2

 per 

year)

Annual 

average 

(mol per m2

per year)

Sampling 

method Reference

New Jersey Coast 211–658 −17 to +12 −0.65 Regional survey Boehme et al. (1998)

Cape Hatteras, 

North Carolina ND −1.0 to +1.2 ND

Moored 

measurements

DeGrandpre et al.

(1997)

Middle Atlantic Bight, 

inner shelf 150–620 ND −0.9 Regional survey DeGrandpre et al.

(2002)

Middle Atlantic Bight, 

middle shelf 220–480 ND −1.6 Regional survey DeGrandpre et al.

(2002)

Middle Atlantic Bight, 

outer shelf 300–430 ND −0.7 Regional survey DeGrandpre et al.

(2002)

Florida Bay, Florida 325–725 ND ND Regional survey Millero et al. (2001)

Southern California 

Coastal Fronts 130–580 ND ND Regional survey Simpson (1985)

Coastal Calif. (M-1; 

Monterey Bay) 245–550 −8 to +50

1997–98: −1.0 

1998–99: +1.1

Moored 

measurements

Friederich et al.

(2002)

Oregon Coast 250–640 ND ND Regional survey van Geen et al. (2000)

Bering Sea Shelf in 

spring (April–June) 130–400 −8 to −12 −8 Regional survey Codispoti et al. (1986)

South Atlantic Bight 300–1200 ND 2.5 Regional survey Cai et al. (2003)

Miss. River Plume 

(summer) 80–800 ND ND Regional survey Cai et al. (2003)

Bering Sea (Aug–Sep.) 192–400 ND ND Regional survey Park et al. (1974)

Table 15.2 Variability of CO2 distributions and fluxes in U.S. coastal waters from regional 

surveys and moored measurements (from Doney et al., 2004).

ND indicates that no data are available.

To convert from “mol” to “grams,” multiply the numerical “mol” value by 12.
161

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

margins with large inputs of fresh water, organic matter, and 

nutrients from land (e.g., Mid- and South-Atlantic Bights) 

(Cai et al., 2003) and (2) coastal upwelling zones (e.g., the 

California-Oregon-Washington coasts, along the eastern 

boundary of the Pacific) where physical processes bring 

cool, high-nutrient, and high-CO2 waters to the surface. In 

both environments, the biological uptake of CO2 plays an 

important role in determining whether an area becomes a 

sink or a source for the atmosphere.

High biological productivity fueled by nutrients added to 

coastal waters can lead to seawater becoming a CO2 sink 

during the summer growing season, as observed in the 

Bering Sea Shelf (Codispoti and Friederich, 1986) and the 

northwest waters off Oregon and Washington (van Geen et 

al., 2000; Hales et al., 2005). Similar CO2 draw-downs may 

occur in the coastal waters of the Gulf of Alaska and in the 

Gulf of Mexico near the Mississippi River outflow. Coastal 

upwelling results in a very high concentration of CO2 for 

the surface water (as high as 1000 μatm), and, hence, the 

surface water becomes a strong CO2 source. This is followed 

by rapid biological uptake of CO2, which causes the water 

to become a strong CO2 sink (Friederich et al., 2002; Hales 

et al., 2005).

A review of North American coastal carbon fluxes has 

been carried out by Doney et al. (2004) (Table 15.2). The 

information reviewed was very limited in space (only 13 

locations) and time, leading Doney et al. to conclude that it 

was unrealistic to reliably estimate an annual flux for North 

American coastal waters. Measurement programs have increased recently, and we have used the newly available data 

to calculate annual North American coastal air-sea fluxes 

for the first time.

15.1.3 Synthesis of Available North American Air-Sea Coastal CO2 Fluxes

A large data set consisting of 550,000 measurements of the 

pCO2 in surface waters has been assembled and analyzed 

(Figure 15.3; see Appendix G for details). Partial pressure 

of CO2 is measured in a carrier gas equilibrated with seawater and, as such, it is a 

measure of the outflux/

influx tendency of CO2

from the atmosphere. 

Carbon dioxide reacts 

with seawater and 99.5% 

of the total amount of 

CO2 dissolved in seawater is in the form of bicarbonate (HCO3

-

) and carbonate 

ions (CO3

=

), which do not exchange with the overlying atmosphere. Only CO2 molecules, which constitute about 0.5% 

of the total dissolved CO2, exchange with the atmosphere. 

This is expressed as pCO2,which is affected by physical and 

biological processes; pCO2 increases as seawater warms and 

decreases when photosynthesis is stimulated. The data were 

obtained by the authors and collaborators, quality-controlled, 

and assembled in a uniform electronic format for analysis 

(available at www.ldeo.columbia.edu/res/pi/CO2). Observations in each 1° × 1° pixel area were compiled into a single 

year and were analyzed for time-space variability. Seasonal 

and interannual variations were not well characterized except in a few locations (Friederich et al., 2002). The annual 

mean air-sea pCO2 difference (∆pCO2) was computed for 

5°-wide zones along the North American continent and was 

plotted as a function of latitude for four regions (Figure 15.4): 

North Atlantic, Gulf of Mexico/Caribbean, North Pacific, 

and Bering/Chukchi Seas. Figure 15.4A shows the fluxes in 

the first nearshore band, and Figure 15.4B shows the fluxes 

for a band that is several hundred kilometers from shore. The 

average fluxes for them and for the intermediate bands are 

given in Table 15.3. The flux and area data are listed in Table 

Figure 15.3 (A) Distribution of coastal surface water CO2 partial 

pressure measurements made between 1979 and 2004. (B) The 

distribution of the annual mean air-sea net CO2 flux over 1° × 1° 

pixel areas (N-S 100 km, E-W 80 km) around North America. 

The flux (g C per m2 per year) represents the climatological mean 

over the 25-year period. The magenta-blue colors indicate that 

the ocean water is a sink for atmospheric CO2, and the green-yellow-orange colors indicate that the sea is a CO2 source. The data 

were obtained by the authors and collaborators of this chapter 

and are archived at the Lamont-Doherty Earth Observatory 

(www.ldeo.columbia.edu/res/pi/CO2).

The open ocean Pacific waters 

south of 30°N are, on the 

annual average, a CO2 source 

to the atmosphere, whereas the 

area north of 40°N is a sink.
The U.S. Climate Change Science Program Chapter 15

162 

15.4. A full complement of seasonal observations are lacking in the Arctic Sea, including Hudson Bay, the northern 

Labrador Sea, and the Gulf of St. Lawrence; the northern 

Bering Sea; the Gulf of Alaska; the Gulf of California; and 

the Gulf of Mexico and the Caribbean Sea.

The offshore patterns follow the same 

general trend found in the global open 

ocean data set shown in Figure 15.1. On 

an annual basis the lower latitudes tend 

to be a source of CO2 to the atmosphere, 

whereas the higher latitudes tend to be 

sinks (Figures 15.3B and 15.4B). The 

major difference in the coastal waters 

is that the latitude where CO2 starts to 

enter the ocean is further north than it 

is in the open ocean, particularly in the Atlantic. A more 

detailed region-by-region description follows.

15.1.4 Pacific Ocean

Observations made in waters along the Pacific coast of 

North America illustrate how widely coastal waters vary 

in space and time, in this case driven by upwelling and 

relaxation (Friederich et al., 2002). Figure 15.5A shows a 

summertime quasi-synoptic distribution of temperature, 

salinity, and pCO2 in surface waters based on measurements 

made in July through September 2005. The effects of the 

Columbia River plume emanating from ~46°N are clearly 

seen (colder temperature, low salinity, and low pCO2), as 

are coastal upwelling effects off Cape Mendocino (~40°N) 

(colder, high salinity, and very high pCO2). These coastal 

features are confined to within 300 km from the coast. The 

1997-2005 time-series data for surface water pCO2 observed 

off Monterey Bay (Figure 15.5B) show the large, rapidly 

fluctuating air-sea CO2 fluxes during the summer upwelling 

season in each year, as well as the low-pCO2 periods during 

the 1997-1998 and 2002-2003 El Niño events. In spite of the 

large seasonal variability, ranging from 200 to 750 μatm, the 

annual mean air-sea pCO2 difference and the net CO2 flux 

over the waters off Monterey Bay areas (~37°N) are close 

to zero (Pennington et al., in press). The seasonal amplitude 

decreases away from the shore and in the open ocean bands, 

where the air-sea CO2 flux changes seasonally in response 

to seawater temperature (out of the ocean in summer and 

into the ocean in winter).

The open ocean Pacific waters south of 30°N are, on the 

annual average, a CO2 source to the atmosphere, whereas 

the area north of 40°N is a sink, and the zone between 30° 

and 40°N is neutral (Takahashi et al., 2002). Coastal waters 

in the 40°N through 45°N zone (northern California-Oregon 

coasts) are even a stronger CO2 sink, associated with nutrient 

input and stratification by fresh water from the Columbia 

River (Hales et al., 2005). On the other hand, coastal pCO2

values in the 15°N through 40°N zones have pCO2 values 

similar to open ocean values and to the atmosphere. In the 

zones 15°N through 40°N, the annual mean values for the net 

air-sea CO2 flux are nearly zero, consistent with the finding 

by Pennington et al. (in press).

15.1.5 Atlantic Ocean

With the exception of the 5°N-10°N zone, the open ocean 

areas are an annual net sink for atmospheric CO2 with 

stronger sinks at high latitudes, especially north of 35°N 

(Figure 15.3B). In contrast, the nearshore waters are a CO2

source between 15°N and 45°N. Accordingly, in contrast to 

the Pacific coast, the latitude where Atlantic coastal waters 

become a CO2 sink is located further north. In the areas 

north of 45°N, the open ocean waters are a strong CO2 sink, 

due primarily to the cold Labrador Sea waters.

 In contrast to the 

Pacific coast, the 

latitude where 

Atlantic coastal 

waters become a 

CO2 sink is located 

further north. 

Figure 15.4 Estimated air-sea CO2 fluxes (g C per per m2 per 

year) from 550,000 seawater CO2 partial pressure (pCO2) observations made from 1979 to 2004 in ocean waters surrounding 

the North American continent. (A) Waters within one degree 

(about 80 km) of the coast and (B) open ocean waters between 

300 and 900 km from the shore (see Figure 15.3B). The annual 

mean air-sea pCO2 difference (∆ pCO2) values were calculated 

from the weekly mean atmospheric CO2 concentrations in the 

GLOBALVIEW-CO2 database (2004) over the same pixel area 

in the same week and year as the seawater pCO2 was measured. 

The monthly net air-sea CO2 flux was computed from the mean 

monthly wind speeds in the National Centers for Environmental 

Prediction/National Center for Atmospheric Research (NCEP/

NCAR) database in the (wind speed)2

 formulation for the airsea gas transfer rate by Wanninkhof (1992). The ± uncertainties 

represent one standard deviation.
163

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

Ocean 

regions

Coastal boxes a First offshore a Second offshore a Third offshore a Open ocean a

Flux N Flux N Flux N Flux N Flux N 

North

Atlantic 3.2±142 80,417 −1.4±94 65,148 −7.3±57 35,499 −10.4± 

76.4 15,771 −26±83 37,667

North

Pacific −0.2±105 164,838 −6.0±81 69,856 −4.3±66 32,045 −5.3±60 16,174 −1.2±56 84,376

G. Mexico 

Caribbean 9.4±24 75,496 8.4±23 61,180 11.5±17.0 8,410 13±20 1,646

Bering/

Chukchi 28.0±110 892 −28±128 868 −44±104 3,399 −53±110 1,465 −63±130 1,848

Table 15.3 Climatological mean annual air-sea CO2 flux (g C per m2

 per year) over the oceans surrounding North 

America. Negative values indicate that the ocean is a CO2 sink for the atmosphere. N is the number of seawater 

pCO2 measurements. The ± uncertainty is given by one standard deviation of measurements used for analysis and 

represents primarily the seasonal variability. 

a The pCO2 data are binned into 1° latitude x 1° longitude box areas. The boxes that include shorelines are named “coastal boxes,” and 

the 1° x 1° boxes located on the ocean side of these “coastal boxes” are called “first offshore” boxes. The next two rows of ocean side 

boxes are called respectively the “second offshore” and the “third offshore” boxes.

In the coastal zone very high pCO2 values (up to 2600 μatm) 

are observed occasionally in areas within 10 km offshore of 

the barrier islands (see small red dots off the coasts of Georgia and the Carolinas in Figure 15.3B). These waters which 

have salinities around 20 and high total CO2 concentrations 

appear to represent outflow of estuarine/marsh waters rich 

in carbon (Cai et al., 2003). The large contribution of fresh 

water that is rich in organic matter relative to the Pacific 

contributes to this small coastal Atlantic source. Offshore 

fluxes are in phase with the seasonal cycle of warming and 

cooling; fluxes are out of the ocean in summer and fall and 

are the inverse in winter and spring.

15.1.6 Bering and Chukchi Seas

Although measurements in these high-latitude waters are 

limited, the relevant data for the Bering Sea (south of 65°N) 

and Chukchi Sea (north of 65°N) are plotted as a function of 

the latitude in Figure 15.4. The values for the areas north of 

55°N are for the summer months only; CO2 observations are 

not available during winter seasons. Although data scatter 

widely, the coastal and open ocean waters are a strong CO2

sink during the summer months due to photosynthetic drawdown of CO2. The data in the 70°-75°N zone are from the 

shallow shelf areas in the Chukchi Sea. These waters are a 

very strong CO2 sink (air-sea pCO2 differences ranging from 

−80 to -180 μatm) with little changes between the coastal 

and open ocean areas. The air-sea CO2 flux during winter 

months is not known but the summer fluxes are shown in 

Figure 15.4 for comparison. Bates (2006) estimated a meanannual air-to-sea CO2 flux2

 of 39 Mt C*** per year over the 

2 The flux was estimated on the basis of measurements made only 

during the spring and summer months of 2002 at several stations 

located in a limited area of the Chukchi Sea. The uncertainty of ± 7 

Mt C given in the original paper represents one standard deviation of 

Chukchi shelf using data from spring and summer of 2002 

that suggested that remnant winter waters were as strong a 

CO2 sink as summer waters (with air-sea pCO2 differences 

of -60 to -160 μatm).

15.1.7 Gulf of Mexico and Caribbean Sea

Although observations are limited, available data suggest 

that these waters are a strong CO2 source (Figure 15.4 and 

Table 15.3). A subsurface anoxic zone has been formed in 

the Texas-Louisiana coast as a result of the increased addition of anthropogenic nutrients and organic carbon by the 

Mississippi River (e.g., Lohrenz et al., 1999). The carbonnutrient cycle in the northern Gulf of Mexico is also being 

investigated (e.g., Cai, 2003), and the studies suggest that at 

times those waters are locally a strong CO2 sink due to high 

biological production.

15.2 SYNTHESIS

An analysis of half a million measurements of air-sea 

flux of CO2 shows that the 

nearshore (< 100 km) coastal 

waters surrounding North 

America are a net CO2 source 

for the atmosphere on an annual average of about 19±22 Mt C 

per year 3 (Table 15.4). Most of 

the flux (14±9 Mt C per year)3

occurs in the Gulf of Mexico 

measured pCO2, but does not include uncertainties in the sea-air gas 

transfer coefficient estimated on the basis of wind speeds and those 

from limited time-space coverage.

3 The specified uncertainty is ± one standard deviation around the 

mean.

 An analysis of half a million 

measurements shows that 

the nearshore (< 100 km) 

coastal waters surrounding 

North America are a weak 

net CO2 source for the 

atmosphere, the open 

oceans are a net CO2 sink 

on an annual average.
The U.S. Climate Change Science Program Chapter 15

164 

and Caribbean Sea. The open oceans are a net CO2 sink on 

an annual average (Table 15.4; Takahashi et al., 2002). The 

reported uncertainties reflect the time-space variability but 

do not reflect uncertainties due to lack of observations in 

some portions of the Arctic Sea, Bering Sea, Gulf of Alaska, 

Gulf of Mexico, or Caribbean Sea. Observations in these 

areas will be needed to improve estimates. If the estimate of 

39 Mt C*** per year sink for the Chukchi Sea (Bates, 2006) 

is included, the North American coastal waters might be 

a small CO2 sink. These results are consistent with recent 

global estimates that suggest that nearshore areas receiving 

terrestrial organic carbon input are sources of CO2 to the 

atmosphere and that marginal seas are sinks (Borges, 2005; 

Borges et al., in press). Hence, the net contribution from 

North American ocean margins is small and difficult to 

distinguish from zero. It is not clear how much of the open 

ocean sink results from photosynthesis driven by nutrients 

of coastal origin.

15.3 TRENDS AND DRIVERS

The sea-to-air CO2 flux from the coastal zone is small (about 

1%) compared with the global ocean uptake flux, which is 

about 1800 Mt C per year (or 1.8 Gt C per year), and hence 

does not influence the global air-sea CO2 budget. However, 

coastal waters undergo large variations in air-sea CO2 flux 

on daily to seasonal time scales and on small spatial scales 

(Figure 15.5). Fluxes can change on the order of 250 g C per 

m2 per year or 0.7 g C per m2 per day on a day to day basis 

(Figure 15.5). These large fluctuations can significantly 

modulate atmospheric CO2 concentrations over the adjacent 

continent and need to be considered when using the distribution of CO2 in calculations of continental fluxes.

Freshwater bodies have not been treated in this analysis 

except to note the large surface pCO2 resulting from estuaries along the east coast. The Great Lakes and rivers also 

represent net sources of CO2 as, in the same manner as the 

estuaries, organic material from the terrestrial environment 

is oxidized so that respiration exceeds photosynthesis. Interestingly, the effect of fresh water is opposite along the 

coast of the Pacific northwest, where increased stratification 

and iron inputs enhance photosynthetic activity (Ware and 

Thomson, 2005), resulting in a large sink for atmospheric 

CO2 (Figure 15.3). A similar process may be at work at the 

mouth of the Amazon (Körtzinger, 2003). This emphasizes 

once again the important role of biological processes in 

controlling the air-sea fluxes of CO2.

The air-sea fluxes and the underlying carbon cycle processes 

that determine them (Figure 15.2) vary seasonally, interannually, and on longer time scales. The eastern Pacific, including the United States’ west coast, is subject to changes 

associated with large-scale climate oscillations such as El 

Niño (Chavez et al., 1999; Feely et al., 2002; Feely et al., 

2006) and the Pacific Decadal Oscillation (PDO) (Chavez et 

al., 2003; Hare and Mantua, 2000; Takahashi et al., 2003). 

These climate patterns, and others, like the North Atlantic 

Oscillation (NAO), alter the oceanic CO2 sink/source conditions directly through seawater temperature changes as well 

as ecosystem variations that occur via complex physicalOcean areas (km2

) Mean air-sea CO2 flux (1012 grams or Mt C per year)

Coastal 

boxes

First 

offshore

Second 

offshore

Third 

offshore

Open 

ocean

Coast 

box

First 

offshore

Second 

offshore

Third 

offshore Open ocean

North Atlantic coast (8° N to 45°N)

625,577 651,906 581,652 572,969 3,388,500 2.7±9.5 -0.5±9.3 -4.0±4.9 -6.5±6.3 -41.5±28.1

North Pacific coast (8°N to 55°N)

1,211,555 855,626 874,766 646,396 7,007,817 2.1±17.1 -7.0±14.1 -4.8±12.5 -3.7±5.3 -53.8±60.7

Gulf of Mexico and Caribbean Sea (8°N to 30°N)

1,519,335 1,247,413 935,947 1,008,633 13.6±8.9 10.9±7.5 6.8±5.00 6.6±5.0

Bering and Chukchi Seas (50°N to 70°N)

481,872 311,243 261,974 117,704 227,609 0.8±3.1 -6.2±9.5 -5.3±7.5 -3.7±3.0 -9.8±3.7

Total ocean areas surrounding North America

3,838,339 3,066,188 2,654,339 2,300,702 10,623,926 19.1±21.8 -2.8±20.7 -7.4±16.2 -7.3±10.1 -105.2±67.0

Table 15.4 Areas (km2

) and mean annual air-sea CO2 flux (Mt C per year) over four ocean regions surrounding 

North America. Since the observations in the areas north of 60°N in the Chukchi Sea were made only during the 

summer months, the fluxes from that area are not included. The ± uncertainty is given by one standard deviation 

of measurements used for analysis and represents primarily the seasonal variability.
165

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

biological interactions (Hare and Mantua, 2000; Chavez et 

al., 2003; Patra et al., 2005). For example, during El Niño, 

upwelling of high CO2 waters is dramatically reduced along 

central California (Figure 15.5) so that flux out of the ocean 

is reduced. At the same time, photosynthetic uptake of CO2

is also reduced (Chavez et al. 2002), reducing ocean uptake. The net effect of climate variability on air-sea fluxes 

therefore remains uncertain and depends on the time-space 

integral of the processes.

15.4 OPTIONS FOR MANAGEMENT

Two options for carbon sequestration have been proposed: (1) 

injection of CO2 in deep subsurface waters (Brewer, 2003) 

and (2) ocean iron fertilization (Martin, 1990). The first 

might be applicable in waters surrounding North America, 

although potential biological side effects are unresolved. The 

largest potential for iron fertilization resides in the high nutrient waters of the equatorial Pacific, subarctic Pacific, and 

Southern Ocean. Offshore waters of coastal upwelling systems have also been considered to be iron limited. However, 

efficiency and capacity of sequestration remain unresolved 

(Bakker et al., 2001; Boyd et al., 2000; Coale et al., 2004; 

Gervais et al., 2002) as do environmental perturbations that 

could be induced by fertilization (Chisholm et al., 2001).

15.5 RESEARCH AND DEVELOPMENT 

NEEDS VIS-à-VIS OPTIONS

Waters with highly variable air-sea CO2 fluxes are located 

primarily within 100 km of the coast (Figure 15.5). With 

the exception of a few areas, the available observations are 

grossly inadequate to resolve the high-frequency, smallspatial-scale variations. These high intensity air-sea CO2

flux events may introduce errors in continental CO2 fluxes 

calculated by atmospheric inversion methods. Achieving 

a comprehensive understanding of the carbon cycle in 

waters surrounding the North American continent will 

Figure 15.5 Time-space variability of coastal waters off the west coast of North America. (A) Quasi-synoptic distribution of the 

temperature, salinity, and pCO2 in surface waters during July-September 2005. The Columbia River plume (~46°N) and the upwelling 

of deep waters off Cape Mendocino (~40°N) are clearly seen. (B) 1997-2005 time-series data for air-sea CO2 flux from a mooring off 

Monterey Bay, California. Seawater is a CO2 source for the atmosphere during the summer upwelling events, but biological uptake 

reduces levels very rapidly. These rapid fluctuations can affect atmospheric CO2 levels. For example, if CO2 from the sea is mixed 

into a static column, a 500 m thick planetary boundary layer over the course of one day, atmospheric CO2 concentration would 

change by 2.5 μatm. If the column of air is mixed vertically through the troposphere to 500 mbar, a change of about 0.5 μatm would 

occur. The effects would be diluted as the column of air mixes laterally. However, this demonstrates that the large fluctuations of 

air-sea CO2 flux observed over coastal waters could affect the concentration of CO2 significantly enough to affect estimates of airland flux based on the inversion of atmospheric CO2 data. Air-sea CO2 flux was low during the 1997-1998 and 2002-2003 El Niño 

periods. The shaded areas indicate the 1997-1998 and 2002-2003 El Niño episodes. The greatest El Niño anomalies occur in the 

winter which is the period of lowest air-sea fluxes. 
The U.S. Climate Change Science Program Chapter 15

166 

require development of advanced 

technologies and sustained and 

inter-disciplinary research efforts. Both of these seem to be on 

the horizon with (1) the advent of 

ocean observatories that include 

novel fixed and mobile platforms 

together with developing instrumentation to measure critical 

stocks and fluxes and (2) national 

and international research programs that include the Integrated 

Ocean Observing System (IOOS) 

and Ocean Carbon and Climate 

Change (OC3). A more comprehensive understanding will require the 

development of a robust observing 

program that incorporates time series observations of air-sea and sinking-particulate carbon 

fluxes in the coastal and open ocean. Our present estimates 

suggest that the carbon that reaches the bottom over continental margins may be responsible for upwards of 40%***

of the carbon reaching the ocean seafloor (Muller-Karger 

et al., 2005). Given the importance of aquatic systems to 

atmospheric CO2 concentrations, these developing efforts 

must be strongly encouraged. Ocean carbon sequestration 

studies should also be continued.
The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

APPENDIX A

167

Although the lands of the New World were inhabited 

before the arrival of Europeans, the changes since arrival have been enormous, especially during the last two 

centuries. Peak United States emissions from land-use 

change occurred late in the nineteenth century, and 

the last few decades have experienced a carbon sink 

(Houghton et al., 1999; Hurtt et al., 2002). 

In Canada, peak emissions occurred 

nearly a century later than in the United 

States, and current data show that land-use 

change causes a net carbon sink (Environment Canada, 2005). In Mexico, the emissions of carbon continue to increase from 

net deforestation. All three countries may 

be in different stages of the same development pattern (Figure 3.2)

The largest changes in land use and the 

largest emissions of carbon came from 

the expansion of croplands. In addition 

to the carbon lost from trees, soils lose 

25-30% of their initial carbon content (to 

a depth of 1 m) when cultivated. In the 

United States, croplands increased from 

about 0.25 million hectares (ha) in 1700 

to 236 million ha in 1990 (Houghton et 

al., 1999; Houghton and Hackler, 2000). 

The most rapid expansion (and the largest 

emissions) occurred between 1800 and 

1900, and since 1920, there has been little 

net change in cropland area. Pastures expanded nearly as much, from 0.01 million 

to 231 million ha, most of the increase 

Historical Overview of the Development of United States, 

Canadian, and Mexican Ecosystem Sources and Sinks for 

Atmospheric Carbon

Coordinating Lead Author: Stephen Pacala, Princeton Univ.

Lead Authors: Richard A Birdsey, USDA Forest Service; Scott D. Bridgham, Univ. Oreg.; Richard T. Conant, 

Colo. State Univ.; Kenneth Davis, The Pa. State Univ.; Burke Hales, Oreg. State Univ.; Richard A. Houghton, 

Woods Hole Research Center; Jennifer C. Jenkins, Univ. Vt.; Mark Johnston, Saskatchewan Research Council; 

Gregg Marland, ORNL and Mid Sweden Univ. (Östersund); Keith Paustian, Colo. State Univ.;

Contributing Authors: John Casperson, Univ. Toronto; Robert Socolow, Princeton Univ.; Richard S. J. Tol, 

Hamburg Univ.

taking place between 1850 and 1950. As most pastures 

were derived from grasslands, the associated changes 

in carbon stocks were modest.

The total area of forests and woodlands in the United 

States declined as a result of agricultural expansion by 
The U.S. Climate Change Science Program Appendix A

168

160 million ha (38%), but this net change obscures the dynamics of forest loss and recovery, especially in the eastern 

part of the United States. After 1920, forest areas increased 

by 14 million ha nationwide as farmlands continued to be 

abandoned in the northeast, southeast, and north central regions. Nevertheless, another 4 million ha of forest were lost 

in other regions, and the net recovery of 10 million ha offset 

only 6% of the net loss (Houghton and Hackler, 2000).

Between 1938 and 2002, the total area of forestland in the 

conterminous United States decreased slightly, by 3 million 

ha (Smith et al., 2004). This small change is the net result 

of much larger shifts among land-use classes (Birdsey and 

Lewis, 2003). Gains of forestland, primarily from cropland 

and pasture, were about 50 million ha for this period. Losses 

of forestland to cropland, pasture, and developed use were 

about 53 million ha for the same period. Gains of forestland 

were primarily in the Eastern United States, whereas losses 

to cropland and pasture were predominantly in the South, 

and losses to developed use were spread around all regions 

of the United States.

In the United States, harvest of industrial wood (timber) generally followed the periods of major agricultural clearing in 

each region. In the last few decades, total volume harvested 

increased until a recent leveling took place (Smith et al.,

2004). The volume harvested in the Pacific Coast and Rocky 

Mountain regions has declined sharply, whereas harvest 

in the South increased and in the North, stayed level. Fuel 

wood harvest peaked between 1860 and 1880, after which 

fossil fuels became the dominant type of fuel (Houghton 

and Hackler, 2000).

The arrival of Europeans reduced the area annually burned, 

but a federal program of fire protection was not established 

until early in the twentieth century. Fire exclusion had begun 

earlier in California and in parts of the central, mountain, 

and Pacific regions. However, neither the extent nor the timing of early fire exclusion is well known. After about 1920, 

the Cooperative Fire Protection Program gradually reduced 

the areas annually burned by wildfires (Houghton et al., 

1999, 2000). The reduction in wildfires led to an increase 

in carbon storage in forests. How long this “recovery” will 

last is unclear. There is some evidence that fires are becoming more widespread again, especially in Canada and the 

western United States. Fire exclusion and suppression are 

also thought to have led to woody encroachment, especially 

in the southwestern and western United States. The extent 

and rate of this process is poorly documented, however, 

and estimates of a carbon sink are very uncertain. Gains in 

carbon above-ground may be offset by losses below-ground 

in some systems, and the spread of exotic annual grasses 

into semiarid deserts and shrublands may be converting the 

recent sink to a source (Bradley et al., in preparation).

The consequence of this land-use history is that United 

States’ forests, at present, are recovering from agricultural 

abandonment, fire suppression, and reduced logging (in 

some regions), and as a result, are accumulating carbon 

(Birdsey and Heath, 1995; Houghton et al., 1999; Caspersen 

et al., 2000; Pacala et al., 2001). The magnitude of the sink 

is uncertain, and whether any of it has been enhanced by 

environmental change (CO2 fertilization, nitrogen deposition, and changes in climate) is unclear. Understanding the 

mechanisms responsible for the current sink is important for 

predicting its future behavior (Hurtt et al., 2002).

In the mid-1980s, Mexico lost approximately 668,000 ha of 

closed forests annually, about 75% of them tropical forests 

(Masera et al., 1997). Most deforestation was for pastures. 

Another 136,000 ha of forest suffered major perturbations, 

and the net flux of carbon from deforestation, logging, fires, 

degradation, and the establishment of plantations was 52.3 

million tons of carbon per year, about 40% of the country’s 

estimated annual emissions of carbon. A later study found 

the deforestation rate for tropical Mexico to be about 12% 

higher (1.9% per year) (Cairns et al., 2000).
The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

APPENDIX B

169

Eddy-Covariance Measurements Now Confirm 

Estimates of Carbon Sinks from Forest Inventories 

Coordinating Lead Author: Stephen Pacala, Princeton Univ.

Lead Authors: Richard A Birdsey, USDA Forest Service; Scott D. Bridgham, Univ. Oreg.; Richard T. Conant, 

Colo. State Univ.; Kenneth Davis, The Pa. State Univ.; Burke Hales, Oreg. State Univ.; Richard A. Houghton, 

Woods Hole Research Center; Jennifer C. Jenkins, Univ. Vt.; Mark Johnston, Saskatchewan Research Council; 

Gregg Marland, ORNL and Mid Sweden Univ. (Östersund); Keith Paustian, Colo. State Univ.;

Contributing Authors: John Casperson, Univ. Toronto; Robert Socolow, Princeton Univ.; Richard S. J. Tol, 

Hamburg Univ.

Long-term, tower-based, eddy-covariance measurements (e.g., Wofsy et al., 1993) represent an independent 

approach to measuring ecosystem-atmosphere carbon 

dioxide (CO2) exchange. The method describes fluxes 

over areas of approximately 1 

km2 (Horst and Weil, 1994), 

measures hour-by-hour ecosystem carbon fluxes, and can be 

integrated over time scales of 

years. A network of more than 

200 sites now exists globally 

(Baldocchi et al., 2001); more 

than 50 of these are in North 

America. None of these sites existed in 1990, so these represent a 

relatively new source of information about the terrestrial carbon 

cycle. An increasing number of 

these measurement sites include 

concurrent carbon inventory 

measurements.

Where eddy-covariance and 

inventory measurements are 

concurrent, the rates of accumulation or loss of biomass are 

often consistent to within several 

tens of g C per m2 per year for 

a one-year sample (10 g C per 

year is 5% of a typical net sink 

of two metric tons of carbon per 

hectare per year for an Eastern 

deciduous successional forest). 

Published intercomparisons in 

North America exist for western coniferous forests 

(Law et al., 2001), agricultural sites (Verma et al., 

2005), and eastern deciduous forests (Barford et al., 

2001; Cook et al., 2004; Curtis et al., 2002; Ehmann et 

Component

Change in carbon 

stock or flux

(Mg C per ha per 

year)a

Totals

Change in live biomass

A. Above-ground

1. Growth

2. Mortality

B. Below-ground (estimated)

1. Growth

2. Mortality

Subtotal

1.4 (±0.2)

–0.6 (±0.6)

0.3

–0.1

1.0 (±0.2)

Change in dead wood

A. Mortality

1. Above-ground

2. Below-ground

B. Respiration

Subtotal

0.6 (±0.6)

0.1

–0.3 (±0.3)

0.4 (±0.3)

Change in soil carbon (net) 0.2 (±0.1)

Sum of carbon budget figures 1.6 (±0.4)

Sum of eddy-covariance flux 

measurements 2.0 (±0.4)

Table B.1 Carbon budget for Harvard Forest from forest inventory and 

eddy-covariance flux measurements, 1993-2001. Source: Barford et al. 

(2001), Table 1. Numbers in parentheses give the ranges of the 95% confidence intervals. Following the sign convention in Barford et al. (2001), 

positive values represent uptake from the atmosphere (i.e., a sink) and 

negative values a release (i.e., a source).

a 1 Mg C per ha per year = 100g C per m2 per year.
The U.S. Climate Change Science Program Appendix B

170

al., 2002; Gough et al., in review). Multiyear studies at two 

sites (Barford et al., 2001; Gough et al., in review) show that 

5- to 10-year averages converge toward inventory measurements. Table B.1 from Barford et al. (2001) shows the results 

of nearly a decade of concurrent measurements in an eastern 

deciduous forest.

This concurrence between eddy-covariance flux measurements and ecosystem carbon inventories is relevant because 

it provides independent validation of the inventory measurements used to estimate long-term trends in carbon stocks. 

The eddy-covariance data are also valuable because the 

assembly of global eddy-covariance data provides independent support for net storage of carbon by many terrestrial 

ecosystems and the substantial year-to-year variability in 

this net sink. The existence of the eddy-covariance data also 

makes the sites suitable for co-locating mechanistic studies 

of interannual and shorter, time-scale processes governing 

the terrestrial carbon cycle. Chronosequences show trends 

consistent with inventory assessments of forest growth, and 

comparisons across space and plant functional types are 

beginning to show broad consistency. These results show a 

consistency across a mixture of observational methods with 

complementary characteristics, which should facilitate the 

development of an increasingly complete understanding of 

continental carbon dynamics (Canadell et al., 2000).
The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

APPENDIX C

171

Industry and Waste Management - Supplemental Material

Lead Author: John Nyboer, Simon Fraser Univ.

Contributing Authors: Mark Jaccard, Simon Fraser Univ.; Ernest Worrell, LBNL

This appendix presents diagrams of the carbon flows 

in Canada, the United States, and Mexico, respectively 

(Figures C.1 through C.3). The numerical data in these 

figures are shown in thousands of metric tons of carbon, 

which can be converted into thousands of metric tons 

of carbon dioxide (CO2) equivalents by multiplying 

the carbon values by 44/12 (i.e., the ratio of CO2 mass 

to carbon mass). The combined carbon flows for all 

three nations are presented in Figure 8.2 in Chapter 8 

of this report.

Figure C.1 Carbon flows, Canada. Source: Energy data from Statistics Canada Industrial Consumption of Energy survey, 

conversion coefficients and process emissions from Environment Canada, Canada GHG Inventory (2002). Production 

data from Statistics Canada, CANSIM Table 002-0010, Tables 303-0010, -0014 to -0021, -0024, -0060, Pub. Cat. Nos.: 

21-020, 26-002, 45-002, Canadian Pulp and Paper Association on forestry products.
The U.S. Climate Change Science Program Appendix C

172

Figure C.2 Carbon flows, United States. Source: Energy data from IEA Oil Information (2004), IEA Coal Information (2005), 

IEA Natural Gas Information (2004). Process emissions: EPA, U.S. Emissions Inventory. Production of forestry products: USDA 

Database; FO-2471000 and -2472010, U.S. Timber Production, Trade, Consumption, and Price Statistics 1965-2005, Production 

of organic products (e.g., food): USDA PS&D Official Statistical Results, Steel: International Iron and Steel institute, World steel in 

figures (2003), Minerals production: USGS mineral publications.

Figure C.3 Carbon flows, Mexico. Source: Energy data from IEA Oil Information (2004), IEA Coal Information (2005), IEA Natural 

Gas Information (2004). Process emissions: EPA, U.S. Emissions Inventory. Production of forestry products: USDA Database; FO2471000, -2472010, -2482000, -2483040, -6342000, -6342040. Production of organic products (e.g., food): USDA PS&D Official 

Statistical Results. Steel: International Iron and Steel institute, World steel in figures (2003).
The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

APPENDIX D

173

Ecosystem Carbon Fluxes

Lead Authors: Richard A. Birdsey, USDA Forest Service; Jennifer C. Jenkins, Univ. Vt.; Mark Johnston, Saskatchewan Research Council; Elisabeth Huber-Sannwald, Instituto Potosino de Investigación Científica y 

Tecnológica

Contributing Authors: Brian Amiro, Univ. Manitoba; Ben de Jong, ECOSUR; Jorge D. Etchevers Barra, Colegio de Postgraduado; Nancy French, Altarum Inst.; Felipe Garcia-Oliva, UNAM; Mark Harmon, Oreg. State Univ.; 

Linda S. Heath, USDA Forest Service; Victor J. Jaramillo, UNAM; Kurt Johnsen, USDA Forest Service; Beverly E. 

Law, Oreg. State Univ.; Erika Marin-Spiotta, Univ. Calif. Berkeley; Omar Masera, UNAM; Ronald Neilson, USDA 

Forest Service; Yude Pan, USDA Forest Service; Kurt Pregitzer, Mich. Tech. Univ.

The recent history of disturbance largely determines 

whether a forest system will be a net source or sink of 

carbon. For example, net ecosystem productivity (NEP, 

see Table D.1 for a list of definitions and acronyms 

used in this appendix) is being measured across a range 

of forest types in Canada using the eddy covariance 

technique. In mature forests, values range from -19.6 

tons of carbon per hectare (t C per ha) per year in a 

white pine plantation in southern Ontario (Arain and 

Restrepo-Coupe, 2005) to -3.2 t C per ha per year in a 

jack pine forest (Amiro et al., 2005; Griffis et al., 2003). 

In recently disturbed forests, NEP ranges from +58.0 

t C per ha per year in a harvested Douglas-fir forest 

(Humphreys et al., 2005) to +5.7 t C per ha per year 

in a seven year old harvested jack pine forest (Amiro 

et al., 2005). In general, forest stands recovering from 

disturbance are sources of carbon until uptake from 

growth becomes greater than losses due to respiration, 

usually within 10 years (Amiro et al., 2005).

Term Acronym Definition

Net Primary Production NPP Net uptake of carbon by plants in excess of 

respiratory loss

Heterotrophic Respiration Rh

Respiratory loss by above- and below-ground 

heterotrophs (herbivores, decomposers, etc.)

Net Ecosystem Production NEP

Net carbon accumulation within the ecosystem after all gains and losses are accounted 

for, typically measured using ground-based 

techniques. By convention, positive values of 

NEP represent accumulaitons of carbon by 

the ecosystem, and negative values represent 

carbon loss.

Net Ecosystem Exchange NEE

The net flux of carbon between the land and 

the atmosphere, typically measured using 

eddy covariance techniques. Note: NEE and 

NEP are equivalent terms but are not always 

identical because of measurement and scaling 

issues, and the sign conventions are reversed. Positive values of NEE (net ecosystem 

exchange with the atmoshpere) usually refer 

to carbon released to the atmosphere (i.e., a 

source), and negative values refer to carbon 

uptake (i.e., a sink).

Table D.1 Ecosystem Productivity Terms and Definitions. (Terms and 

definitions apply to Appendices D and E of this report.) 

Sources: Randerson et al. (2002); Chapin et al. (2006).
The U.S. Climate Change Science Program Appendix D

174

In the United States, extensive land-based measurements 

of forest/atmosphere carbon exchange reveal patterns and 

causes of sink or source strength (Table D.2). Results show 

that net ecosystem exchange (NEE) of carbon in temperate 

forests ranges from a source of +12.7 t C per ha per year 

to a sink of -5.9 t C per ha per year. Forests identified as 

sources are primarily forests in the earliest stages of regeneration (up to about eight years) following stand-replacing 

disturbances such as wildfire and logging (Law et al., 

2002). Mature temperate deciduous broadleaf forests and 

mature evergreen coniferous forests were an average sink 

of -2.7 and -2.5 t C per ha per year, respectively (12 sites, 

54 site-years of data). Values ranged from a source of +0.3 

for a mixed deciduous and evergreen forest to a sink of -5.8 

for an aggrading deciduous forest, averaged over multiple 

years. Young temperate evergreen coniferous forests (8 to 

20 years) ranged from a sink of -0.6 to -5.9 t C per ha per 

year (mean -3.1). These forests are still rapidly growing and 

have not reached the capacity for carbon uptake.

Mature forests can have substantial stocks of sequestered 

carbon. Disturbances that damage or replace forests can 

result in the land being a net source of carbon dioxide (CO2) 

for a few years in mild climates to 10-20 years in harsh 

climates while the forests are recovering (Law et al., 2002; 

Clark et al., 2004). Thus, the range of observed annual NEE 

of CO2 ranges from a source of about +13 t C per ha per year 

in a clearcut forest to a net sink of -6 t C per ha in mature 

temperate forests.

For Mexican forests, estimates of net ecosystem carbon 

exchange are unavailable, but estimates from other tropical 

forests may indicate rates for similar systems in Mexico. 

In Puerto Rico, aboveground NPP in tropical forests range 

from -9.2 to -11.0 t C per ha per year (Lugo et al., 1999). 

Below-ground NPP measurements exist for only one site 

with -19.5 t C per ha per year (Lugo et al., 1999). In Hawaii, 

above-ground and below-ground NPP of native forests 

dominated by Metreosideros polymorpha vary depending 

on substrate age and precipitation regime. Above-ground 

NPP ranges between -4.0 to -14.0 t C per ha per year, while 

below-ground NPP ranges between -5.2 and -9.0 t C per ha 

per year (Giardina et al., 2004). Soil carbon emissions along 

the substrate age gradient range from +2.2 to +3.3 t C per ha

per year, and along the precipitation gradient from +4.0 to 

+9.7 t C per ha per year (Osher et al., 2003). NEP estimates 

are not available for these tropical forests, so their net impact 

on atmospheric carbon stocks cannot be calculated.

NEE (t Carbon per ha per year)

Regenerating Clearcut 

(1 to 3 years after disturbance) 

(1 site, 5 site-years)

Young forest

(8 to 20 years old) 

(4 sites, 16 site-years)

Mature forest 

(>20 years old)

(13 sites, 60 site-years)

Evergreen Coniferous 

Forests

–1.7 to +12.7

mean = 7.1, (SD 4.7)

(1 site, 5 site-years)

–0.6 to –5.9

mean = –3.1, (SD 2.6) 

(4 sites, 16 site-years)

–0.6 to –4.5 

mean = –2.5, (SD 1.4) 

(6 sites, 20 site-years)

Mixed Evergreen and 

Deciduous Forests NA NA

–0.3 to –2.1

mean = –1.0, (SD 0.6) 

(1 site, 6 site-years)

Deciduous Broadleaf 

Forests NA NA

–0.6 to –5.8

mean = –2.7, (SD 1.8) 

(6 sites, 34 site-years)

Table D.2 Comparison of net ecosystem exchange (NEE) for different types and ages of temperate 

forests. Negative NEE means the forest is a sink for atmospheric CO2. Eighty-one site years of data are 

from multiple published papers from each of the AmeriFlux network sites, and a network synthesis 

paper (Law et al., 2002). NEE was averaged by site, then the mean was determined by forest type and 

age class. SD is standard deviation among sites in the forest type and age class.
The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

APPENDIX E

175

Principles of Forest Management for Enhancing 

Carbon Sequestration

Lead Authors: Richard A. Birdsey, USDA Forest Service; Jennifer C. Jenkins, Univ. Vt.; Mark Johnston, Saskatchewan Research Council; Elisabeth Huber-Sannwald, Instituto Potosino de Investigación Científica y Tecnológica

Contributing Authors: Brian Amiro, Univ. Manitoba; Ben de Jong, ECOSUR; Jorge D. Etchevers Barra, 

Colegio de Postgraduado; Nancy French, Altarum Inst.; Felipe Garcia-Oliva, UNAM; Mark Harmon, Oreg. 

State Univ.; Linda S. Heath, USDA Forest Service; Victor J. Jaramillo, UNAM; Kurt Johnsen, USDA Forest 

Service; Beverly E. Law, Oreg. State Univ.; Erika Marin-Spiotta, Univ. Calif. Berkeley; Omar Masera, UNAM; 

Ronald Neilson, USDA Forest Service; Yude Pan, USDA Forest Service; Kurt Pregitzer, Mich. Tech. Univ.

The net rate of carbon accumulation has been generally 

understood (Woodwell and Whittaker, 1968) as the 

difference between gross primary production (gains) 

and respiration (losses), although this neglects important processes such as leaching of dissolved organic 

compounds (DOCs), emission of methane (CH4), fire, 

harvests, or erosion that may contribute substantially 

to carbon loss and gain in forest ecosystems (Schulze et 

al., 1999; Harmon, 2001; Chapin et al., 2006). The net 

ecosystem carbon balance (NECB) in forests is, therefore, defined as net ecosystem production, or NEP, plus 

the non-physiological horizontal and vertical transfers 

into and out of the forest stand.

With respect to the impacts of forest management on the 

overall carbon balance, some general principles apply 

(Harmon, 2001; Harmon and Marks, 2002; Pregitzer et 

al., 2004). First, forest management can impact carbon 

pool sizes via:

• changing production rates (since NEP = net 

primary production [NPP] – heterotrophic 

respiration [Rh]);

• changing decomposition flows (Rh) (e.g., 

Fitzsimmons et al., 2004);

• changing the amount of material transferred 

between pools; or

• changing the period between disturbances/

management activities.

The instantaneous balance between production, 

decomposition, and horizontal or vertical transfers 

into and out of a forest stand determines whether 

the forest is a net source or a net sink. Given that 

these terms all change as forests age, the disturbance return interval is a key driver of stand- and 

landscape-level carbon dynamics. Rh tends to be 

enhanced directly after disturbance, so as residue and 

other organic carbon pools decompose, a forest is often 

a net source immediately after disturbances such as 

management activity. NPP tends to increase as forests 

age, although in older forests it may decline (Ryan, 

1997). Eventually, as stands age, NPP and Rh become 

similar in magnitude, although few managed stands 

are allowed to reach this age. The longer the average 

time interval between disturbances, the more carbon is 

stored. The nature of the disturbance is also important; 

the less severe the disturbance (e.g., less fire removal), 

the more carbon is stored.

Several less general principles can be applied to specific 

carbon pools, fluxes, or situations:

• Management activities that move live carbon to 

dead pools (such as coarse woody debris [CWD] 

or soil carbon) over short periods of time will often 

dramatically enhance decomposition (Rh), although 

considerable carbon can be stored in decomposing 

pools (Harmon and Marks, 2002). Regimes seeking to reduce the decomposition-related flows from 

residue following harvest may enhance overall sink 

capacity of these forests if these materials are used 

for energy generation or placed into forest products 

that last longer than the residue.

• Despite the importance of decomposition rates 

to the overall stand-level forest carbon balance, 

management of CWD pools is mostly impacted by 

recruitment of new CWD rather than by changing 

decomposition rates (Janisch and Harmon, 2002; 

Pregitzer and Euskirchen, 2004). Decreasing the 

interval between harvests can significantly decrease 

the store in this pool.

• Live coarse root biomass accounts for approximately 
The U.S. Climate Change Science Program Appendix E

176

20-25% of aboveground forest biomass (Jenkins et al., 

2003), and there is additional biomass in fine roots. 

Following harvest, this pool of live root biomass is 

transferred to the dead biomass pool, which can form a 

significant carbon store. Note that roots of various size 

classes and existing under varying environmental conditions decompose at different rates.

•Some carbon can be sequestered in wood products from 

harvested wood, though, due to manufacturing losses, 

only about 60% of the carbon harvested is stored in 

products (Harmon, 1996). Clearly, longer-lived products 

will sequester carbon for longer periods of time.

•According to international convention, the replacement of 

fossil fuel by biomass fuel can be counted as an emissions 

offset if the wood is produced from sustainably managed 

forests (Schoene and Netto, 2005)

Little published research has been aimed at quantifying the 

impacts of specific forest management activities on carbon 

storage, but examples of specific management activities 

can be given.

Practices aimed at increasing NPP: fertilization; 

genetically improved trees that grow faster (Peterson 

et al., 1999); any management activity that enhances 

growth rate without causing a concomitant increase 

in decomposition (Stanturf et al., 2003; Stainback 

and Alavalapati, 2005).

Practices aimed at reducing R

h

(i.e., minimizing the 

time forests are a source to the atmosphere following disturbance): low impact harvesting (that does 

not promote soil respiration); utilization of logging 

residues (biomass energy and fuels); incorporation 

of logging residue into soil during site prep (but note 

that this could also speed up decomposition); thinning to capture mortality; fertilization.

Since NECB changes with time as forests age, if a landscape 

is composed of stands with different ages, then carbon gains 

in one stand can be offset by losses from another stand. The 

net result of these stand-level changes determines overall 

landscape-level carbon stores. Note that disturbance-induced Rh losses are typically larger than annual gains, such that 

a landscape where forest area is increasing might still be 

neutral with respect to carbon stocks overall. Thus, at the 

landscape level, practices designed to enhance carbon sequestration must, on balance, replace lower-carbon-density 

systems with higher-carbon-density systems. Examples of 

these practices include: reducing fire losses; emphasizing 

very long-lived forest products; increasing the interval between disturbances; or reducing decomposability of dead 

material. ••
The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

APPENDIX F

177

Wetlands - Supplemental Material

Lead Author: Scott D. Bridgham, Univ. Oreg.

Contributing Authors: J. Patrick Megonigal, Smithsonian Environmental Research Center; Jason K. Keller, 

Smithsonian Environmental Research Center; Norman B. Bliss, SAIC, USGS Center for Earth Resources, 

Observation and Science; Carl Trettin, USDA Forest Service

F.1 INVENTORIES

F.1.1 Current Wetland Area and Rates of Loss

The ability to estimate soil carbon pools and fluxes in 

North American wetlands is constrained by the national 

inventories (or lack thereof) for Canada, the United 

States, and Mexico (Davidson et al., 1999). The National Wetland Inventory (NWI) program of the United 

States has repeatedly sampled several thousand wetland 

sites using aerial photographs and more limited field 

verification. The data are summarized in a series of 

reports detailing changes in wetland area in the conterminous United States for the periods of the mid-1950s to 

mid-1970s (Frayer et al., 1983), mid-1970s to mid-1980s 

(Dahl and Johnson, 1991), and 1986 to 1997 (Dahl, 

2000). We used these relatively high-quality data sets 

extensively for estimating wetland area and loss rates 

in the conterminous United States, including mud flats. 

However, the usefulness of the NWI inventory reports 

for carbon budgeting is limited by the level of classification used to define wetland categories within the 

Cowardin et al. (1979) wetland classification system. At 

the level used in the national status and trend reports, 

vegetated freshwater wetlands are classified by dominant physiognomic vegetation type, and it is impossible 

to make the important distinction between wetlands 

with deep organic soils (i.e., peatlands) and wetlands 

with mineral soils. The data are not at an adequate 

spatial resolution to combine with U.S. Department of 

Agriculture (USDA) Natural Resources Conservation 

Service (NRCS) soil maps to discriminate between 

the two types of wetlands (T. Dahl, personal comm.). 

Because of these data limitations, we used the NRCS 

soil inventory of peatlands (i.e., Histosols and Histels, 

or peatlands with and without permafrost, respectively) 

to estimate original peatland area (Bridgham et al., 

2000) and combined these data with regional estimates 

of loss (Armentano and Menges, 1986) to estimate current peatland area in the conterminous United States. 

We calculated the current area of freshwater mineralsoil (FWMS) wetlands in the conterminous United 

States by subtracting peatland area from total wetland 

area (Dahl, 2000). This approach was limited by the 

Armentano and Menges peatland area data being current only up to the early 1980s, although large losses of 

peatlands since then are unlikely due to the institution 

of wetland protection laws.

We used a similar approach for Alaskan peatlands: peatland area was determined by the NRCS soil inventory 

(N. Bliss, query of the NRCS State Soil Geographic 

[STATSGO] database, February 2006) and overall 

wetland inventory was determined by standard NWI 

methods (Hall et al., 1994). However, our peatland 

estimate of 132,000 km2 (Table F.1) is 22% of the 

often cited value by Kivinen and Pakarinen (1981) of 

596,000 km2.

Kivinen and Pakarinen also used NRCS soils data 

(Rieger et al., 1979) for their peatland estimates, but 

they defined a peatland as having a minimum organic 

layer thickness of 30 cm, whereas the current United 

States and Canadian soil taxonomies require a 40-cm 

thickness. The original 1979 Alaska soil inventory has 

been reclassified with current United States soil taxonomy (J. Moore, Alaska State Soil Scientist, personal 

comm.). Using the reclassified soil inventory, Alaska 

has 417,000 km2 of wetlands with a histic modifier 

(i.e., a surface organic layer between 20 and 60 cm 

thick) that are not Histosols or Histels, indicating significant carbon accumulation in the surface horizons 

of FWMS wetlands. Thus, we conclude that Kivinen 

and Pakarinen’s Alaska peatland area estimate is higher 

because many Alaskan wetlands have a thin organic 

horizon that is not deep enough to qualify as a peatland 

under current soil taxonomy. Our smaller peatland area 

significantly lowers our estimate of carbon pools and 

fluxes in Alaskan peatlands compared to earlier studies 

(see Carbon Pools below). 

The area of salt marsh in the conterminous United 

States, Canada, and Alaska were taken from Mendels-
The U.S. Climate Change Science Program Appendix F

178

a Tarnocai et al. (2005).

b National Wetlands Working Group (1988).

c Brackish and salt marsh areas from Mendelssohn and McKee (2000); freshwater tidal wetlands for the conterminous United States only 

from Odum et al. (1984) and Field et al. (1991).

d Estimated from the area of Canadian salt marshes and the ratio of mudflat to salt marsh area reported by Hanson and Calkins (1996).

e Accounting for losses due to permafrost melting in western Canada (Vitt et al., 1994). This is an underestimate, as similar, but 

undocumented, losses have probably also occurred in eastern Canada and Alaska.

f 9000 km2 lost to reservoir flooding (Rubec, 1996), 250 km2 to forestry drainage (Rubec, 1996), 124 km2 to peat harvesting for 

horticulture (Cleary et al., 2005), and 16 km2 to oil sands mining (Turetsky et al., 2002). See note e for permafrost melting estimate.

g Rubec (1996).

h Estimated loss rate for the Americas from Valiela et al. (2001) for approximately 1980 to 1990.

i Historical area from NRCS soil inventory (Bridgham et al., 2000), except Alaska inventory updated by N. Bliss from a February 2006 

query of the STATSGO database. Less than 1% wetland losses have occurred in Alaska (Dahl, 1990). 

j Total freshwater wetland area from Hall et al. (1994) minus peatland area.

k Hall et al. (1994).

l Historical area from Bridgham et al. (2000) minus losses in Armentano and Menges (1986).

m Overall freshwater wetland area from Dahl (2000) minus peatland area.

n Dahl (2000). Historical area estimates are only from the 1950s.

o Total historical wetland area from Dahl (1990) minus historical peatland area minus historical estuarine area.

p Spiers (1999) and Davidson (1999).

q ND indicates that no data are available. 

r Assuming that historical proportion of peatlands to total wetlands in Mexico was the same as today.

s Bridgham et al. (2000) for the United States, Tarnocai et al. (2005) for Canada, Joosten, and Clarke (2002) for the rest of world. 

Recent range in literature 2,974,000–3,985,000 km2 (Matthews and Fung, 1987; Aselmann and Crutzen, 1989; Maltby and Immirzi, 1993; 

Bridgham et al., 2000; Joosten and Clarke, 2002).

t Average of 2,289,000 km2 from Matthews and Fung (1987) and 2,341,000 km2 Aselmann and Crutzen (1989).

u Chmura et al. (2003). Underestimated because no inventories were available for the continents Asia, South America, and Australia 

which are mangrove-dominated but also support salt marsh.

v Spalding (1997).

w Range from 3,880 to 4,086 in Maltby and Immirzi (1993). 

x Approximately 50% loss from Moser et al. (1996).

y Assumed a 25% loss rate outside North America for tidal marshes; a loss rate of 35% was used for mangroves (Valiela et al., 2001).

Table F.1 Current and historical area of wetlands in North America and the world (×103 km2). 

Historical refers to approximately 1800, unless otherwise specified.

Permafrost

peatlands

Nonpermafrost

peatlands

Mineral-soil

freshwater

Salt

marsh

Mangrove Mudflat Total

Canada

Current 422a 714a 159b 0.4c 0 6d 1301

Historical 424e 726f 359g 1.3b 0 7h 1517

Alaska

Current 89i 43i 556j 1.4c 0 7k 696

Historical 89 43 556 1.4 0 7 696

Conterminous United States

Current 0 93l 312m 20c 3c 2n 431

Historical 0 111i 762o 22n 4n 3n 901

Mexico

Current 0 10p 21p 0 5c NDq 36

Historical 0 45p 0 8h ND 53

North America

Current 511 861 1,047 22 8 15 2,463

Historical 513 894r 1,706r 25 12 17 3,167

Global

Current 3,443s 2,315t 22u 181v ND 5,961

Historical 4,000w 5,000x 29y 278y ND 9,307
The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

179

sohn and McKee (2000). Because these estimates include 

brackish tidal marshes, they cannot be compared directly to 

the area of Canadian salt marshes. Compilations of freshwater, tidal wetland area are difficult to find, but there is 

approximately 1,640 km2 on the east coast of the United 

States (Odum et al., 1984) and 470 km2 on the United States’ 

Gulf Coast (Field et al., 1991). Although some freshwater 

tidal wetlands are forested, this total was added to the tidal 

marsh area for the conterminous United States. Mangrove 

area was taken from Mendelssohn and McKee (2000), and 

is similar to an estimate by Lugo and Snedaker (1974).

The original area of tidal wetlands in the conterminous 

United States was based on the NWI (Dahl, 2000), which 

we considered to be the most defensible estimate available. 

However, “original” here only refers to the 1950s, when the 

first national wetland inventory was conducted in the conterminous United States to provide a historic baseline area. 

It is almost certain that the actual loss of tidal wetland area 

in the conterminous United States over a longer time frame 

was larger than the 7.7% figure used in our calculation. Valiela et al. (2001) estimated a loss of 31% of mangrove area 

in the United States from 1958 to 1982, but acknowledged 

a high level of uncertainty in this figure. We assumed that 

the original area of Alaskan tidal wetlands was similar to the 

current area because there has been relatively little development pressure in Alaska. To estimate loss of global tidal 

wetlands, we arbitrarily used a figure of 35% loss for tidal 

marshes outside of the United States and Mexico.

A regular national inventory of Canada’s wetlands has not 

been undertaken, although wetland area has been mapped 

by ecoregion (National Wetlands Working Group, 1988). 

Extensive recent effort has gone into mapping Canadian 

peatlands (Tarnocai, 1998; Tarnocai et al., 2005). We calculated the current area of mineral-soil wetlands as the 

difference between total wetland area and peatland area in 

National Wetland Working Group (1988). The original area 

of FWMS wetland area was obtained from Rubec (1996). 

Canadian salt marsh estimates were taken from a compilation by Mendelssohn and McKee (2000). The compilation 

does not include brackish or freshwater tidal marshes, 

and we were unable to locate other estimates of Canadian 

brackish marsh area. The original area of salt marshes was 

estimated from the National Wetland Working Group (1988), 

but it is highly uncertain. There are no reliable country-wide 

estimates of mud flat area for Canada, but a highly uncertain 

extrapolation from a limited number of regional estimates 

was possible based upon the ratio of mudflat to salt marsh 

area reported by Hanson and Calkins (1996).

No national wetland inventories have been done for Mexico. 

Current freshwater wetland estimates for Mexico were 

taken from Davidson et al. (1999) and Spiers (1999), who 

used inventories of discrete wetland regions performed by 

a variety of organizations. Thus, freshwater wetland area 

estimates for Mexico are highly unreliable and are possibly a 

large underestimate. For mangrove area in Mexico, we used 

the estimates compiled by Mendelssohn and McKee (2000), 

which are similar to estimates reported in Davidson et al.

(1999) and Spalding et al. (1997). We could find no estimates 

of tidal marsh or mud flat area for Mexico. Since most 

vegetated Mexican tidal wetlands are dominated by mangroves (Olmsted, 1993; Mendelssohn and McKee, 2000), the 

omission of Mexican tidal marshes should not significantly 

affect our carbon budget. However, there may be large areas 

of mud flat that would significantly increase our estimate 

of carbon pools and sequestration in this country. We used 

the Valiela et al. (2001) estimate of 38% for mangrove loss 

in the Americas, which roughly covers the period 1980 to 

1990. This is less than the rough worldwide estimate of 50% 

wetland loss since the 1880s that is often cited (see Zedler 

and Kercher, 2005) and is probably conservative. A global 

loss rate of 35% was used for mangrove area globally based 

on the analysis of Valiela et al. (2001).

F.2 CARBON POOLS

F.2.1 Freshwater Mineral-Soil (Gleysol) 

Carbon Pools 

Gleysol is a soil classification used by the Food and Agriculture Organization (FAO) and many countries that denotes 

mineral soils formed under waterlogged conditions (FAOUNESCO, 1974). Tarnocai (1998) reported a soil carbon 

density of 200 Mg C per hectare (ha) for Canadian Gleysols 

to 1-m depth. Batjes (1996) determined soil carbon content 

globally from the Soil Map of the World (FAO, 1991) and a 

large database of soil pedons. He estimated an average value 

for soil carbon density of 199 Mg C per ha (CV1 = 212%, n 

= 14 pedons) for Gleysols of the world to 2-m depth; to 1-m 

depth, he reported a soil carbon density of 131 Mg C per ha 

(CV = 109%, n =142 pedons).

Gleysols are not part of the United States’ soil taxonomy 

scheme, and mineral soils with attributes reflecting waterlogged conditions are distributed among numerous 

soil groups. We queried the NRCS State Soil Geographic 

(STATSGO) soils database for soil carbon density in “wet” 

mineral soils of the conterminous United States (all soils 

that had a surface texture described as peat, muck, or 

mucky peat, or appeared on the 1993 list of hydric soils, 

which were not classified as Histosols) (N. Bliss, query 

of NRCS STATSGO database, December 2005). We used 

the average soil carbon densities of 162 Mg C per ha from 

this query for FWMS wetlands in the conterminous United 

States and Mexico.

1 CV is the “coefficient of variation,” or 100 times the standard deviation 

divided by the mean. 
The U.S. Climate Change Science Program Appendix F

180

Permafrost

peatlands

Non-permafrost

peatlands

Mineralsoil

freshwater

Salt

marsh Mangrove Mudflat Total

Canada

Pool Size in Current Wetlands 47.4a 102.9b 4.6a 0.0c 0.0c 0.1d 155.0

Sequestration in Current Wetlands -5.5e -13.6e -2.7f -0.1 0.0 c -1.2d -23.0

Oxidation in Former Wetlands 0.2g 0.0h 0.0i 0.0 0.0 0.2

Historical Loss in Sequestration Capacity 0.0e 0.2e 3.4f 0.2 0.0 0.3 4.2

Change in Flux From Wetland Conversions 0.4 3.4 0.2 0.0 0.3 4.3

Alaska

Pool Size in Current Wetlands 9.3j 6.2j 26.0k 0.0 0.0 0.1 41.7

Sequestration in Current Wetlands -1.2e -0.8e -9.4f -0.3 0.0 -1.6 -13.3

Oxidation in Former Wetlands 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Historical Loss in Sequestration Capacity 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Change in Flux From Wetland Conversions 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Conterminous United States

Pool Size in Current Wetlands 0 14.0l 5.1k 0.4 0.1 0.0 19.6

Sequestration in Current Wetlands 0 -6.6m -5.3f -4.4 -0.5 -0.5 -17.3

Oxidation in Former Wetlands 0 18.0n 0.0h 0.0 0.0 0.0 18.0

Historical Loss in Sequestration Capacity 0 1.2m 7.6f 0.4 0.0 0.1 9.4

Change in Flux from Wetland Conversions 0 19.2 7.6 0.4 0.0 0.1 27.4

Mexico

Pool Size in Current Wetlands 0 1.5l 0.3k 0.0 0.1 ND 1.9

Sequestration in Current Wetlands 0 -1.6o -0.4f 0.0 -1.6 ND -3.6

Oxidation in Former Wetlands 0 ND ND 0.0 0.0 0.0 ND

Historical Loss in Sequestration Capacity 0 ND ND 0.0 1.0 ND ND

Change in Flux from Wetland Conversions 0 ND ND 0.0 1.0 ND ND

North America

Pool Size in Current Wetlands 56.7 124.6 36.0 0.4 0.2 0.3 218.2

Sequestration in Current Wetlands -6.6 -22.6 -17.7 -4.8 -2.1 -3.3 -57.2

Oxidation in Former Wetlands 18.2 0.0 0.0 0.0 0.0 18.2

Historical Loss in Sequestration Capacity 0 1.4 11.0 0.5 1.0 0.5 14.5

Change in Flux from Wetland Conversions 19.6 11.0 0.5 1.0 0.5 32.7

Global

Pool Size in Current Wetlands 462p 46q 0.4r 4.9r ND 513

Sequestration in Current Wetlands -55s -39f -4.6r -38.0r ND -137

Oxidation in Former Wetlands 205t ND 0 0 0 205

Historical Loss in Sequestration Capacity 16t 45f 0.7u 20v ND 82

Change in Flux From Wetland Conversions 221t > 45 0.7 20 ND 287

Table F.2 Soil carbon pools (Gt) and fluxes (Mt per year) of wetlands in North America and the world. 

“Sequestration in current wetlands” refers to carbon sequestration in extant wetlands; “oxidation 

in former wetlands” refers to emissions from wetlands that have been converted to non-wetland 

uses or conversion among wetland types due to human influence; “historical loss in sequestration 

capacity” refers to the loss in the carbon sequestration function of wetlands that have been converted 

to non-wetland uses; “change in flux from wetland conversions” is the sum of the two previous fluxes. 

Positive flux numbers indicate a net flux into the atmosphere, whereas negative numbers indicate a 

net flux into the ecosystem.
The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

181

Some caution is necessary regarding the use of Gleysol 

or “wet” mineral soil carbon densities because apparently 

they include large areas of seasonally wet soils that are not 

considered wetlands by the more conservative definition of 

wetlands used by the United States and many other countries and organizations. For example, Eswaran et al. (1995) 

estimated that global wet mineral-soil area was 8,808,000 

km2, which is substantially higher than the commonly accepted mineral-soil wetland area estimated by Matthews and 

Fung (1987) of 2,289,000 km2 and Aselmann and Crutzen 

(1989) of 2,341,000 km2, even accounting for substantial 

global wetland loss. In our query of the NRCS STATSGO 

database for the United States, we found 1,258,000 km2

of wet soils in the conterminous United States versus our 

estimate of 312,000 km2 of FWMS wetlands, currently, 

and 762,000 km2, historically (Table F.1). We assume that 

including these wet-but-not-wetland soils will decrease the 

estimated soil carbon density, but to what degree we do not 

know. However, just considering the differences in area will 

give large differences in the soil carbon pool. For example, 

Eswaran et al. (1995) estimated that wet mineral soils globally contain 108 Gt C to 1-m depth, whereas our estimate is 

46 Gt C to 2-m depth (Table F.2).

For Alaska, many soil investigations have been conducted 

since the STATSGO soil data was coded. We updated 

STATSGO by calculating soil carbon densities from data 

obtained from the NRCS on 479 pedons collected in Alaska, 

and then we used this data for both FWMS wetlands and 

peatlands. For some of the Histosols, missing bulk densities 

a Tarnocai (1998); mineral soil to 1-m depth.

b Tarnocai et al. (2005).

c Rates and pools calculated from Chmura et al. (2003) using country-specific data (sedimentation accumulation rates in Mg C per ha 

per year: Mexican mangroves = 3.3, conterminous United States mangroves = 1.8, conterminous United States tidal marshes = 2.2, tidal 

marshes in Canada and Alaska = 2.1); areas from Table 13F.1.

d Assumed the same carbon density and accumulation rates as the adjacent vegetated wetland ecosystem (mangrove data for Mexico and 

salt marsh data elsewhere).

e Assumed carbon accumulation rate of 0.13 Mg C per ha per year for permafrost peatlands and 0.19 Mg C per ha per year for nonpermafrost peatlands. Reported range of long-term apparent accumulation rates from 0.05-0.35 (Ovenden, 1990; Maltby and Immirzi, 1993; 

Trumbore and Harden, 1997; Vitt et al., 2000; Turunen et al., 2004).

f Rate calculated as the geometric mean sediment accumulation rate of 2.2 Mg sediment per ha per year (range 0-80) from Johnston (1991) 

and Craft and Casey (2000) times 7.7 % C (CV = 109) (Batjes 1996). 

g Sum of 0.24 Mt C per year from horticulture removal of peat (Cleary et al., 2005) and 0.10 Mt C per year from increased peat 

sequestration due to permafrost melting (Turetsky et al., 2002). 

h Assumed that the net oxidation of 8.6% of the soil carbon pool (Euliss et al., 2006) over 50 years after conversion to non-wetland use.

i Assumed that conversion of tidal systems is caused by fill and results in burial and preservation of SOM, Sedimentary Organic Matter, 

rather than oxidation.

j Soil carbon densities of 1,441 Mg C per ha for Histosols and 1,048 Mg C per ha for Histels (Tarnocai et al., 2005). 

k Soil carbon density of 162 Mg C per ha for the conterminous United States and Mexico and 468 Mg C per ha for Alaska based upon 

NRCS STATSGO database and soil pedon information. 

l Assumed soil carbon density of 1,500 Mg C per ha. 

m Webb and Webb (1988). 

n Estimated loss rate as of early 1980s (Armentano and Menges, 1986). Overall, wetlands losses in the United States have declined 

dramatically since then (Dahl, 2000) and probably even more so for Histosols, so this number may still be representative.

o Using peat accumulation rate of 1.6 Mg C per ha (range 1.0–2.25) (Maltby and Immirzi, 1993).

p From Maltby and Immirzi (1993). Range of 234 to 679 GtC (Gorham, 1991; Maltby and Immirzi, 1993; Eswaran et al., 1995; Batjes, 1996; 

Lappalainen, 1996; Joosten and Clarke, 2002).

q Soil carbon density of 199 Mg C per ha (Batjes, 1996).

r Chmura et al. (2003).

s Joosten and Clarke (2002) reported range of -40 to -70 Mt C per year. Using the peatland estimate in Table F.1 and a C accumulation rate 

of 0.19 Mg C per ha per year, we calculate a global flux of -65 Mt C per year in peatlands. 

t Current oxidative flux is the difference between the change in flux and the historical loss in sequestration capacity from this table. The 

change in flux is from Maltby and Immirzi (1993) (reported range 176 to 266 Mt C per year) and the historical loss in sequestration 

capacity is from this table for North America, from Armentano and Menges (1986) for other northern peatlands, and from Maltby and 

Immirzi (1993) for tropical peatlands.

u Assumed that global rates approximate the North America rate because most salt marshes inventoried are in North America.

v Assumed 25% loss globally since the late 1800s.

ND indicates that no data are available. 
The U.S. Climate Change Science Program Appendix F

182

were calculated using averages of measured bulk densities 

for the closest matching class in the USDA Soil Taxonomy 

(NRCS, 1999). A matching procedure was developed for 

relating sets of pedons to sets of STATSGO components. 

If there were multiple components for each map unit in 

STATSGO, the percentage of the component was used to 

scale area and carbon data. We compared matching sets of 

pedons to sets of components at the four top levels of the 

United States’ soil taxonomy: Orders, Suborders, Great 

Groups, and Subgroups. For example, the soil carbon for all 

pedons having the same soil order were averaged, and the 

carbon content was applied to all of the soil components of 

the same order (e.g., Histosol pedons are used to characterize 

Histosol components). At the Order level, all components 

were matched with pedon data. At the suborder level, pedon 

data were not available to match approximately 20,000 km2

(compared to the nearly 1,500,000-km2 area of soil in the 

state), but the soil characteristics were more closely associated with the appropriate land areas than at the Order level. 

At the Great Group and Subgroup levels, pedon data were 

unavailable for much larger areas, even though the quality 

of the data when available became better. For this study, we 

used the Suborder-level matching. The resulting soil carbon 

density for Alaskan FWMS wetlands was 469 Mg C per ha, 

reflecting large areas of wetlands with a histic epipedon as 

noted above.

F.2.2 Peatland Soil Carbon Pools

The carbon pool of permafrost and non-permafrost peatlands 

in Canada had been previously estimated by Tarnocai et al.

(2005) based upon an extensive database. Good soil-carbon 

density data are unavailable for peatlands in the United 

States, as the NRCS soil pedon information typically only 

goes to a maximum depth of between 1.5 to 2 m, and many 

peatlands are deeper than this. Therefore, we used the carbon 

density estimates of Tarnocai et al. (2005) of 1,441 Mg C 

per ha for Histosols and 1,048 Mg C per ha for Histels to 

estimate the soil carbon pool in Alaskan peatlands.

The importance of our using a smaller area of Alaskan 

peatlands becomes obvious here. Using the larger area from 

Kivinen and Pakarinen (1981), Halsey et al. (2000) estimated 

that Alaskan peatlands have a soil carbon pool of 71.5 Gt, 

almost 5-fold higher than our estimate. However, some of 

the difference in soil carbon between the two estimates can 

be accounted for by the 26 Gt C that we calculated resides 

in Alaskan FWMS wetlands (Table F.2).

The peatlands of the conterminous United States are different in texture, and probably depth, from those in Canada 

and Alaska, so it is probably inappropriate to use the soil 

carbon densities for Canadian peatlands for those in the 

conterminous United States. For example, we compared the 

relative percentage of the Histosol suborders (excluding the 

small area of Folists, as they are predominantly upland soils) 

for Canada (Tarnocai, 1998), Alaska (updated STATSGO 

data, J. Moore, personal comm.), and the conterminous 

United States (NRCS, 1999). The relative percentage of 

Fibrists, Hemists, and Saprists, respectively, in Canada are 

37%, 62%, and 1%, in Alaska are 53%, 27%, and 20%, and 

in the conterminous United States are 1%, 19%, and 80%. 

Using the STATSGO database (N. Bliss, query of NRCS 

STATSGO database, December 2005), the average soil 

carbon density for Histosols in the conterminous United 

States is 1,089 Mg C per ha, but this is an underestimate 

as many peatlands were not sampled to their maximum 

depth. Armentano and Menges (1986) reported average 

carbon density of conterminous United States’ peatlands to 

1-m depth of 1,147 to 1,125 Mg C per ha. Malterer (1996) 

gave soil carbon densities of conterminous United States’ 

peatlands of 2,902 Mg C per ha for Fibrist, 1,874 Mg C per 

ha for Hemists, and 2,740 Mg C per ha for Saprists, but it is 

unclear how he derived these estimates. Batjes (1996) and 

Eswaran et al. (1995) gave average soil carbon densities to 

1-m depth for global peatlands of 776 and 2,235 Mg C per 

ha, respectively. We chose to use an average carbon density 

of 1,500 Mg C per ha, which is in the middle of the reported 

range, for peatlands in the conterminous United States and 

Mexico.

F.2.3 Estuarine Soil Carbon Pools 

Tidal wetland soil carbon density was based on a countryspecific analysis of data reported in an extensive compilation 

by Chmura et al. (2003). There were more observations for 

the United States (n = 75) than Canada (n = 34) or Mexico 

(n = 4), and consequently there were more observations of 

marshes than mangroves. The Canadian salt marsh estimate 

was used for Alaskan salt marshes and mud flats. In the conterminous United States and Mexico, country-specific marsh 

or mangrove estimates were used for mudflats. Although 

Chmura et al. (2003) reported some significant correlations 

between soil carbon density and mean annual temperature, 

scatter plots suggest the relationships are weak or driven 

by a few sites. Thus, we did not separate the data by region 

or latitude and used mean values for scaling. Chmura et al.

(2003) assumed a 50-cm-deep profile for the soil carbon 

pool, which may be an underestimate.

F.2.4 Plant Carbon Pools 

While extensive data on plant biomass in individual wetlands have been published, no systematic inventory of wetland plant biomass has been undertaken in North America. 

Nationally, the forest carbon biomass pool (including aboveground and below-ground biomass) has been estimated to be 

54.9 Mg C per ha (Birdsey, 1992), which we used for forested 

wetlands in the United States and Canada. This approach assumes that wetland forests do not have substantially different 

biomass carbon densities from upland forests. There is one 
The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

183

regional assessment of forested wetlands in the southeastern United States, which comprise approximately 35% of 

the total forested wetland area in the conterminous United 

States. We utilized the southeastern United States regional 

inventory to evaluate this assumption; above-ground tree 

biomass averaged 125.2 m3 per ha for softwood stands and 

116.1 m3 per ha for hardwood stands. Using an average wood 

density and carbon content, the carbon density for these 

forests would be 33 Mg C per ha for softwood stands and 

Table F.3 Plant carbon pools (Gt) and fluxes (Mt per year) of wetlands in North America and the 

world. Positive flux numbers indicate a net flux into the atmosphere, whereas negative numbers 

indicate a net flux into the ecosystem. 

a Biomass for non-forested peatlands from Vitt et al. (2000), assuming 50% of biomass is below-ground. Forest biomass density from 

Birdsey (1992) and forested area from Tarnocai et al. (2005) for Canada and from Hall et al. (1994) for Alaska. 

b Assumed 2000 g C per m2 in above-ground and below-ground plant biomass (Gorham, 1991).

c Biomass data from Mitsch and Gosselink (1993).

d Biomass for non-forested wetlands from Gorham (1991). Forest biomass density from Birdsey (1992), and forested area from Hall et 

al. (1994) for Alaska and Dahl (2000) for the conterminous United States.

e 50 g C per m2 per yr sequestration from forest growth from a southeastern United States regional assessment of wetland forest 

growth (Brown et al., 2001). 

f Assumed that global pools approximate those from North America because most salt marshes inventoried are in North America.

g Twilley et al. (1992).

ND indicates that no data are available. 

Permafrost

peatlands

Non-permafrost

peatlands

Mineralsoil

freshwater

Salt

marsh Mangrove Total

Canada

Pool Size in Current Wetlands 1.4a 0.3b 0.0c 0.0 1.7

Sequestration in Current 

Wetlands 0.0 ND 0.0 0.0 0.0

Alaska

Pool Size in Current Wetlands 0.4a 1.1d 0.0 0.0 1.5

Sequestration in Current 

Wetlands 0.0 0.0 0.0 0.0 0.0 0.0

Conterminous United States

Pool Size in Current Wetlands 0.0 1.5d 0.0 0.0 1.5

Sequestration in Current 

Wetlands 0.0 -10.3e 0.0 0.0 -10.3

Mexico

Pool Size in Current Wetlands 0.0 0.0b 0.0b 0.0 0.1 0.1

Sequestration in Current 

Wetlands 0.0 ND ND 0.0 ND 0.0

North America

Pool Size in Current Wetlands 4.8 0.0 0.1 4.9

Sequestration in Current 

Wetlands 0.0 -10.3 0.0 ND -10.3

Global

Pool Size in Current Wetlands 6.9b 4.6b 0.0f 4.0g 15.5

Sequestration in Current 

Wetlands 0.0 ND ND 0.0 ND ND

42 Mg C per ha for hardwood stands. However, these estimates do not include understory vegetation, below-ground 

biomass, or dead trees, which account for 49% of the total 

forest biomass (Birdsey, 1992). Using that factor to make an 

adjustment for total forest biomass, the range would be 49 

to 66 Mg C per ha for the softwood and hardwood stands, 

respectively. Accordingly, the assumption of using 54.9 Mg 

C per ha seems reasonable for a national-level estimate.
The U.S. Climate Change Science Program Appendix F

184

The area of forested wetlands in Canada came from Tarnocai 

et al. (2005), for Alaska from Hall et al. (1994), and for the 

conterminous United States from Dahl (2000).

Since Tarnocai et al. (2005) divided Canadian peatland area 

into bog and fen, we used above-ground biomass for each 

community type from Vitt et al. (2000), and assumed that 

50% of biomass is below-ground. We used the average bog 

and fen plant biomass from Vitt et al. (2000) for Alaskan 

peatlands. For other wetland areas, we used an average value 

of 20.0 Mg C per ha for non-forested wetland biomass carbon 

density (Gorham, 1991).

Tidal marsh root and shoot biomass data were estimated 

from a compilation in Table 8-7 in Mitsch and Gosselink 

(1993). There was no clear latitudinal or regional pattern 

in biomass, so we used mean values for each. Mangrove 

biomass has been shown to vary with latitude, so we used 

the empirical relationship from Twilley et al. (1992) for 

this relationship. We made a simple estimate using a single 

latitude that visually bisected the distribution of mangroves 

either in the United States (26.9o) or Mexico (23.5o). Total 

biomass was estimated using a root-to-shoot ratio of 0.82 

and a carbon-mass-to-biomass ratio of 0.45, both from Twilley et al. (1992).

Plant biomass carbon data are presented in Table F.3.

F.3 CARBON FLUXES

F.3.1 Peatland Soil Carbon 

Accumulation Rates

Most studies report the long-term apparent rate of carbon 

accumulation (LORCA) in peatlands based upon basal peat 

dates, but this assumes a linear accumulation rate through 

time. However, due to the slow decay of the accumulated 

peat, the true rate of carbon accumulation will always be 

less than the LORCA (Clymo et al., 1998), 

so most reported rates are inherently biased 

upwards. Tolonen and Turunen (1996) 

found that the true rate of peat accumulation was about 67% of the LORCA.

For estimates of soil carbon sequestration in 

conterminous United States’ peatlands, we 

used the LORCA data from 82 sites and 215 

cores throughout eastern North America 

(Webb and Webb III, 1988). They reported 

a median accumulation rate of 0.066 cm 

per year (mean = 0.092, sd = 0.085). We 

converted this value into a carbon accumulation rate of -0.71 Mg C per ha per 

year by assuming 58% C (see NRCS Soil 

Survey Laboratory Information Manual, 

available on-line at http://soils.usda.gov/survey/nscd/lim/), 

a bulk density of 0.28 g per cm3, and an organic matter 

content of 69%. (Positive carbon fluxes indicate net fluxes 

to the atmosphere, whereas negative carbon fluxes indicate 

net fluxes into an ecosystem.) The bulk density and organic 

matter content were the area-weighted and depth-weighted 

average from all Histosol soil map units greater than 202.5 

ha (n = 3,884) in the conterminous United States from the 

National Soil Information System (NASIS) data base provided by S. Campbell (USDA NRCS, Portland, Oreg.). For 

comparison, Armentano and Menges (1986) used soil carbon 

accumulation rates that ranged from -0.48 Mg C per ha per 

year in northern conterminous United States peatlands to 

-2.25 Mg C per ha per year in Florida peatlands.

Peatlands accumulate lesser amounts of soil carbon at 

higher latitudes, with especially low accumulation rates in 

permafrost peatlands (Ovenden, 1990; Robinson and Moore, 

1999). The rates used in this report reflect this gradient, 

going from -0.13 to -0.19 to -0.71 Mg C per ha per year in 

permafrost peatlands, non-permafrost Canadian and Alaskan peatlands, and peatlands in the conterminous United 

States and Mexico, respectively (Table F.2).

F.3.2 Freshwater Mineral-Soil Wetland 

Carbon Accumulation Rates

Many studies have estimated sediment deposition rates in 

FWMS wetlands, with a geometric mean rate of 2.2 Mg sediment per ha per year (n = 26, arithmetic mean = 16.3, range 0 

to 80.0) in a compilation by Johnston (1991), along with those 

reported more recently in Craft and Casey (2000). As can be 

seen by the difference between the geometric and arithmetic 

means, this dataset is log-normally distributed with several 

large outliers. Assuming 7.7% carbon for FWMS wetlands 

(Batjes, 1996), this gives a geometric mean accumulation 

rate of 0.17 Mg C per ha per year. Johnston (1991) and Craft 

and Casey (2000) reported more studies with only vertical 
The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

185

sediment accumulation rates, 

with a geometric mean of 0.23 

cm per year (n = 34, arithmetic 

mean = 0.63 cm per year, range 

-0.6 to 2.6). If we assume a bulk 

density of 1.00 g per cm3 for 

FWMS wetlands (Batjes, 1996; 

Smith et al., 2001), this converts 

into an unrealistically large accumulation rate of 1.85 Mg C per 

ha per year.

We suggest that caution is necessary in interpretation of these 

data for a number of reasons. 

There is large variability in sedimentation rates among studies, 

and even within a site, sedimentation rates are highly variable 

depending on the local deposition 

environment (Johnston et al., 2001). Researchers may have 

preferentially chosen wetlands with high sedimentation rates 

to study this process, providing a bias towards greater carbon sequestration. Rates of erosion and resultant deposition 

have substantially decreased during the last century in the 

conterminous United States (Craft and Casey, 2000; Trimble 

and Crosson, 2000). More fundamentally, it is important to 

distinguish between autochthonous carbon (derived from onsite plant production) and allochthonous carbon (imported 

from outside the wetland) in soil carbon storage. The soil 

carbon stored in peatlands is of autochthonous origin and 

represents sequestration of atmospheric carbon dioxide at the 

landscape scale. In contrast, a unknown portion of the soil 

carbon that is stored in FWMS wetlands is of allochthonous 

origin. However, conterminous United States’ soils average between 0.9 and 1.3% soil carbon, which is much less 

than the average carbon content of FWMS wetlands (7.7%) 

(Batjes, 1996), suggesting a substantial autochthonous input 

to FWMS wetlands.

At a landscape scale, redistribution of sediments from uplands to wetlands represents net carbon sequestration only 

to the extent that the soil carbon is replaced in the terrestrial 

source area and/or decomposition rates are substantially 

lower in the receiving wetland (Stallard, 1998; Harden et 

al., 1999). Agricultural lands are a major source of erosion 

(Meade et al., 1990, as cited in Stallard, 1998), but it appears that, after large initial losses, soil carbon is relatively 

stable (Stallard, 1998; Smith et al., 2001) or even increases 

(Harden et al., 1999) under modern agricultural techniques. 

It is also generally assumed that sediment carbon deposited 

in anaerobic environments, such as occur in many wetlands, 

is relatively recalcitrant (Stallard, 1998; Smith et al., 2001). 

For example, in a variety of Minnesota wetland soils, carbon 

mineralization was approximately six times slower anaerobically than aerobically (Bridgham et al., 1998). However, 

time since initial deposition and organic quality of sediments 

appears to be an important constraint on its relative reactivity. Kristensen et al. (1995) found that relatively fresh, labile 

organic matter had similar decomposition rates aerobically 

and anaerobically, whereas “aged,” recalcitrant organic matter decomposed ten times slower anaerobically. Gunnison 

et al. (1983) found that freshly flooded soils had twice as 

rapid carbon mineralization rates as sediments. In newly 

constructed reservoirs, sediments maintained these rapid 

mineralization rates even 6-10 years after initial flooding. 

Overall, these latter two studies suggest that there may be 

substantial carbon mineralization in freshly deposited allochthonous sediments in wetlands, but we feel that the data 

are not adequate to account for this effect quantitatively.

We use a landscape-level sediment sequestration rate of 0.17 

Mg C per ha per year for FWMS wetlands in North America, 

while acknowledging the low level of confidence in this estimate. Johnston (1991) and Craft and Casey (2000) only gave 

sedimentation rates in FWMS wetlands in the conterminous 

United States. Since most FWMS wetlands in Canada are in 

more developed and agricultural regions, we felt that it was 

reasonable to use the sedimentation estimates from these 

studies. However, most Alaskan FWMS wetlands are relatively pristine, with little anthropogenic sediment input, but 

as described above, most have an extensive histic epipedon, 

so at least historically, they have actively accumulated soil 

carbon. Given that our soil carbon accumulation rate for 

Alaskan peatlands is 0.19 Mg C per ha per year, our sediment 

sequestration rate of 0.17 Mg C per ha per year for Alaskan 

FWMS wetlands does not seem unreasonable.
The U.S. Climate Change Science Program Appendix F

186

a Used CH4 flux of 2.5 g per m2 per yr (range 0 to 130, likely mean 2 to 3) (Moore and Roulet, 1995) for Canadian peatlands 

and all Alaskan freshwater wetlands. Used CH4 flux of 7.6 g per m2 per yr for Canadian freshwater mineral-soil wetlands and all 

United States and Mexican freshwater wetlands and 1.3 g per m2 per yr for estuarine wetlands—from synthesis of published CH4

fluxes for the United States (see Table F.5).

b Includes a 17-fold increase in CH4 flux (Kelly et al., 1997) in the 9000 km2 of reservoirs that have been formed on peatlands 

(Rubec, 1996) and an estimated CH4 flux of 15 g per m2 per yr (Moore et al., 1998) from 2,630 km2 of melted permafrost 

peatlands (Vitt et al., 1994). 

c Assumed trace gas fluxes from unvegetated estuarine wetlands (i.e., mudflats) was the same as adjacent wetlands.

d Bartlett and Harriss (1993).

e Assumed that global rates approximate the North America rate because most salt marsh area is in North America.

f Ehhalt et al. (2001), range of 92 to 237 Mt per yr.

g Using rates from Bartlett and Harriss (1993) and historical loss of area in Table 1.

ND indicates that no data are available. 

Table F.4 Methane fluxes (Mt per year) from wetlands in North America and the world.

Permafrost

peatlands

Nonperma-frost

peatlands

Mineral-soil

freshwater

Salt

marsh Mangrove Mudflat Total

Canada

CH4 Flux in Current

Wetlands 1.1a 2.1b 1.2 0.0 0.0 0.0c 4.4

Historical change in 

CH4 Flux 0.0 0.3 -1.5 0.0 0.0 0.0 -1.2

Alaska

CH4 Flux in Current

Wetlands 0.2 0.1 1.4 0.0 0.0 0.0 1.7

Historical change in 

CH4 Flux 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Conterminous United States

CH4 Flux in Current 

Wetlands 0.0 0.7 2.4 0.0 0.0 0.0 3.1

Historical change in 

CH4 Flux 0.0 -0.1 -3.4 0.0 0.0 0.0 -3.5

Mexico

CH4 Flux in Current

 Wetlands 0.0 0.1 0.2 0.0 0.0 ND 0.2

Historical change in 

CH4 Flux 0.0 -0.1 0.0 0.0 ND -0.1

North America

CH4 Flux in Current 

Wetlands 1.3 3.0 5.1 0.0 0.0 0.0 9.4

Historical change in 

CH4 Flux 0.0 -4.9 0.0 0.0 0.0 -4.9

Global

CH4 Flux in Current 

Wetlands 14.1d 22.5d 68.0d 0.0e 0.2 ND 105f

Historical change in 

CH4 Flux -3.6g -79 g 0.0e -0.1 ND -83
The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

187

F.3.3 Estuarine Carbon Accumulation Rates

Carbon accumulation in tidal wetlands was assumed to be 

entirely in the soil pool. This should provide a reasonable 

estimate because marshes are primarily herbaceous, and 

mangrove biomass should be in steady state unless the site 

was converted to another use. An important difference 

between soil carbon sequestration in tidal and non-tidal 

systems is that tidal sequestration occurs primarily through 

burial driven by sea level rise. For this reason, carbon accumulation rates can be estimated well with data on changes 

in soil surface elevation and carbon density. Rates of soil 

carbon accumulation were calculated from Chmura et al.

(2003) as described above for the soil carbon pool (rates 

in Mg C per ha per year are 3.3 for Mexican mangroves; 

1.8 and 2.2 for mangroves and tidal marshes, respectively, 

in the conterminous United States; 2.1 for tidal marshes 

in Canada and Alaska). These estimates are based on a 

variety of methods, such as 210Pb dating and soil elevation 

tables, which integrate vertical soil accumulation rates over 

periods of time ranging from 1–100 years. The soil carbon 

sequestered in estuarine wetland sediments is likely to be a 

mixture of both allochthonous and autochthonous sources. 

However, without better information, we assumed that in 

situ rates of soil carbon sequestration in estuarine wetlands 

is representative of the true landscape-level rate.

F.3.4 Extractive Uses of Peat 

Use of peat for energy production is, and always has been, 

negligible in North America, as opposed to other parts of the 

world (WEC, 2001). However, Canada produces a greater 

volume of horticultural and agricultural peat than any other 

country in the world (WEC, 2001). Currently, 124 km2 of 

Canadian peatlands have been under extraction now or in 

the past (Cleary et al., 2005). A life-cycle analysis by these 

authors estimated that as of 1990 Canada emitted 0.2 Mt 

per year of CO2-C equivalents through peat extraction. The 

United States’ production of horticultural peat is about 19% 

of Canada’s (Joosten and Clarke, 2002), which assuming a 

similar life-cycle as for Canada, suggests that the United 

States produces 0.05 Mt of CO2-C equivalents through peat 

extraction.

F.3.5 Methane Fluxes

Moore and Roulet (1995) reported a range of methane fluxes 

from 0 to 130 g CH4 per m2 per year from 120 peatland sites 

in Canada, with the majority <10 g CH4 per m2 per year. 

They estimated a low average flux rate of 2 to 3 g CH4 per 

m2 per year, which equaled an emission of 2–3 Mt CH4 per 

year from Canadian peatlands. We used an estimate of 2.5 

g CH4 per m2 per year for Canadian peatlands and Alaskan 

freshwater wetlands (Table F.4).

To our knowledge, the last synthesis of field measurements 

of methane emissions from wetlands was done by Bartlett 

and Harriss (1993). We supplemented their analysis with 

all other published field studies (using chamber or eddy 

covariance techniques) we could find that reported annual 

or average daily methane fluxes in the conterminous United 

States (Table F.5). We excluded a few studies that used cores 

or estimated diffusive fluxes. 

In cases where multiple years from the same site were presented, we took the average of those years. Similarly, when 

multiple sites of the same type were presented in the same 

paper, we took the average. Studies were separated into 

freshwater and estuarine systems.

In cases where papers presented both an annual flux and a 

mean daily flux, we calculated a conversion factor (annual 

flux/average daily flux) to quantify the relationship between 

those two numbers (Table F.5). When we looked at all studies (n = 30), this conversion factor was 0.36, suggesting that 

there is a 360-day emission season. There was surprisingly 

little variation in this ratio, and it was similar in freshwater 

(0.36) and estuarine (0.34) wetlands. In contrast, previous 

syntheses used a 150-day emission season for temperate 

wetlands (Matthews and Fung, 1987; 

Bartlett and Harriss, 1993). While 

substantial winter methane emissions 

have been found in some studies, it is 

likely that flux data from most studies 

have a non-normal distribution with 

occasional periods of high flux rates 

that are better captured with annual 

measurements.

Using the conversion factors for 

freshwater and estuarine wetlands, 

we estimated average annual fluxes 

from the average daily fluxes. The 

data were highly log-normally distributed, so we used geometric means. For 

freshwater wetlands, the geometric 
The U.S. Climate Change Science Program Appendix F

188

mean estimated annual flux rate was 7.1 g CH4 per m2 per 

year (n = 74, 1 SE = 0.8, arithmetic mean = 38.6), which is 

very similar to the geometric mean measured rate of 8.1 g 

CH4 per m2 per year (n = 32, arithmetic mean = 32.1). For 

estuarine wetlands, the geometric mean estimated annual 

flux rate was 1.3 g CH4 per m2 per year (n = 25, 1 SE = 0.2, 

arithmetic mean = 9.8), which is smaller than the geometric 

mean measured rate of 5.0 g CH4 per m2 per year (n = 13, 

arithmetic mean = 16.9).

Finally, we combined both approaches. In cases where a 

paper presented an annual value, we used that number. In 

cases where only an average daily number was presented, 

we used that value corrected with the appropriate conversion 

factor. For conterminous United States wetlands, FWMS 

Canadian wetlands, and Mexican wetlands, we used a 

geometric mean flux of 7.6 g CH4 per m2 per year, and for 

estuarine wetlands, we used a geometric mean flux of 1.3 

g CH4 per m2 per year.

F.3.6 Plant Carbon Fluxes

For ecosystems at approximately steady state, plant biomass 

should be reasonably constant on average because plant 

production is roughly balanced by mortality and subsequent 

decomposition. We assumed insignificant plant biomass 

accumulation in freshwater and estuarine marshes because 

they are dominated by herbaceous plants that do not accumulate carbon in wood. Sequestration in plants in relatively 

undisturbed forested wetlands in Alaska and many parts of 

Canada is probably small, although there may be substantial 

logging of Canadian forested wetlands for which we do not 

have data. Similarly, no data was available to evaluate the effect of harvesting of woody biomass in Mexican mangroves 

on carbon fluxes.

Tree biomass carbon sequestration averages -1.40 Mg C per 

ha per year in United States’ forests across all forest types 

(Birdsey, 1992). Using the tree growth estimates from the 

southeastern United States regional assessment of wetland 

forests (Brown et al., 2001) yields an even lower estimate of 

sequestration in above-ground tree biomass (approx. -0.50 

Mg C per ha per year). We used this lower value and area 

estimates from Dahl (2000) to estimate that forested wetlands in the conterminous United States currently sequester 

-10.3 Mt C per year.
The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

189

Table F.5 Methane fluxes measured in the conterminous United States. The conversion factor is 

the ratio of the daily average flux to the measured annual flux × 103. The calculated annual flux was 

determined based upon the average conversion factor for freshwater (FW) and saltwater wetlands 

(SW). The measured annual flux was used if that was available; otherwise, the calculated annual flux 

was used.

Habitat State Methoda Salt/

Fresh

Daily

Average

Flux

(mg CH4

per m2 

per day)

Measured

Annual

Flux

(g CH4

per m2 

per year)

Conversion

Factor

Estimated

Annual

Flux

(g CH4

per m2 

per year)

Used

Annual

Flux

(g CH4

per m2 

per year)

Reference

Fens CO C FW 40.7 40.7 Chimner and Cooper 

(2003)

Wet Alpine Meadow CO C FW 0.1 0.0 0.0 Neff et al. (1994)

Lake - Average CO C FW 25.4 9.2 9.2 Smith and Lewis 

(1992)

Wetland - Average CO C FW 28.3 10.3 10.3 Smith and Lewis 

(1992)

Nuphar Bed CO C FW 202.1 73.6 73.6 Smith and Lewis 

(1992)

Tundra - Carex 

Meadow CO C FW 2.8 1.0 1.0 West et al. (1999)

Tundra - Acomastylis Meadow CO C FW -0.5 -0.2 -0.2 West et al. (1999)

Tundra - Kobresia 

Meadow CO C FW -0.8 -0.3 -0.3 West et al. (1999)

Moist Grassy CO C FW 6.1 1.9 0.32 2.2 1.9 Wickland et al. (1999)

Moist Mossy CO C FW 1.5 0.5 0.33 0.5 0.5 Wickland et al. (1999)

Wetland CO C FW 41.7 41.7 Wickland et al. (1999)

Hardwood Hammock FL C FW 0.0 0.0 0.0 Bartlett et al. (1989)

Dwarf Cypress / 

Sawgrass FL C FW 7.5 2.7 2.7 Bartlett et al. (1989)

Spikerush FL C FW 29.4 10.7 10.7 Bartlett et al. (1989)

Sawgrass < 1m FL C FW 38.8 14.1 14.1 Bartlett et al. (1989)

Sawgrass/Spikerush/

Periphyton FL C FW 45.1 16.4 16.4 Bartlett et al. (1989)

Swamp Forest FL C FW 68.9 25.1 25.1 Bartlett et al. (1989)

Sawgrass > 1m FL C FW 71.9 26.2 26.2 Bartlett et al. (1989)

Sawgrass FL C FW 107.0 38.9 38.9 Burke et al. (1988)

Pond Open Water FL C FW 624.0 227.1 227.1 Burke et al. (1988)

Everglades - Cladium FL C FW 45.4 16.5 16.5 Chanton et al. (1993)

Everglades - Typha FL C FW 142.9 52.0 52.0 Chanton et al. (1993)

Wet Prairie (Marl) FL C FW 87.0 31.6 31.6 Happell et al. (1993)

Wet Prairie (Marl) FL C FW 27.4 10.0 10.0 Happell et al. (1993)

Marsh (Marl) FL C FW 30.0 10.9 10.9 Happell et al. (1993)

Marsh (Marl) FL C FW 49.6 18.0 18.0 Happell et al. (1993)

Marsh (Peat) FL C FW 45.4 16.5 16.5 Happell et al. (1993)

Marsh (Peat) FL C FW 13.0 4.7 4.7 Happell et al. (1993)

Marsh (Peat) FL C FW 163.6 59.6 59.6 Happell et al. (1993)

Marsh (Peat) FL C FW 20.4 7.4 7.4 Happell et al. (1993)

Wet Prairie / Sawgrass

FL C FW 61.0 22.2 22.2 Harriss et al. (1988)

Wetland Forest FL C FW 59.0 21.5 21.5 Harriss et al. (1988)

Cypress Swamp 

- Flowing Water FL C FW 67.0 24.4 24.4 Harriss and Sebacher (1981)

Open Water Swamp FL C FW 480.0 174.7 174.7 Schipper and Reddy 

(1994)

Waterlily Slough FL C FW 91.0 33.1 33.1 Schipper and Reddy 

(1994)

a C = chamber, T = tower, eddy covariance, E = ebulition measured separately.
The U.S. Climate Change Science Program Appendix F

190

Cypress Swamp 

- Deep Water GA C FW 92.3 33.6 33.6 Harriss and Sebacher 

(1981)

Bottomland Hardwoods/ Swamps GA C FW 23.0 23.0 Pulliam (1993)

Swamp Forest LA C FW 146.0 53.1 53.1 Alford et al. (1997)

Freshwater Marsh LA C FW 251.0 91.4 91.4 Alford et al. (1997)

Fresh LA C FW 587.0 213.0 0.36 213.6 213.0 DeLaune et al. (1983)

Fresh LA C FW 49.0 18.7 0.38 17.8 18.7 DeLaune et al. (1983)

Sphagnum Bog MD C FW -1.1 -0.4 -0.4 Yavitt et al. (1990)

Bog MI C FW 193.0 70.2 70.2 Shannon and White 

(1994)

Bog MI C FW 28.0 10.2 10.2 Shannon and White 

(1994)

Beaver Meadow MN C FW 2.3 2.3 Bridgham et al. (1995)

Open Bogs MN C FW 0.0 0.0 Bridgham et al. (1995)

Bog (Forested Hummock) MN C FW 10.0 3.5 0.35 3.6 3.5 Dise (1993)

Bog (Forested Hollow) MN C FW 38.0 13.8 0.36 13.8 13.8 Dise (1993)

Fen Lagg MN C FW 35.0 12.6 0.36 12.7 12.6 Dise (1993)

Bog (Open Bog) MN C FW 118.0 43.1 0.37 42.9 43.1 Dise (1993)

Fen (Open Poor 

Fen) MN C FW 180.0 65.7 0.37 65.5 65.7 Dise (1993)

Poor Fen MN C FW 242.0 88.1 88.1 Dise and Verry (2001)

Sedge Meadow MN C FW 11.7 11.7 Naiman et al. (1991)

Submergent MN C FW 14.4 14.4 Naiman et al. (1991)

Deep Water MN C FW 0.5 0.5 Naiman et al. (1991)

Poor Fen MN T FW 14.6 14.6 Shurpali and Verma 

(1998)

Submerged Tidal NC C, E FW 144.8 52.7 52.7 Kelly et al. (1995)

Banks Tidal NC C, E FW 20.1 7.3 7.3 Kelly et al. (1995)

Tidal Marsh NC C FW 3.0 1.0 0.34 1.1 1.0 Megonigal and 

Schlesinger (2002)

Tidal Marsh NC C FW 3.5 2.3 0.65 1.3 2.3 Megonigal and 

Schlesinger (2002)

Prairie Marsh NE T FW 64.0 64.0 Kim et al. (1999)

Poor Fen NH C FW 503.3 110.6 0.22 183.2 110.6 Carroll and Crill 

(1997)

Poor Fen NH C FW 69.3 69.3 Frolking and Crill 

(1994)

Forested Peatland NY C FW 0.6 0.2 0.37 0.2 0.2 Coles and Yavitt 

(2004)

Pools Forested 

Swamp NY C FW 224.6 69.0 0.31 81.7 69.0 Miller et al. (1999)

Typha Marsh - Mineral Soils NY C FW 344.4 125.3 125.3 Yavitt (1997)

Typha Marsh - Peat 

Soils NY C FW 65.1 23.7 23.7 Yavitt (1997)

Typha Marsh - All 

Soils NY C FW 204.8 74.5 74.5 Yavitt (1997)

Cypress Swamp 

- Floodplain SC C FW 9.9 3.6 3.6 Harriss and Sebacher 

(1981)

Habitat State Methoda Salt/

Fresh

Daily

Average

Flux

(mg CH4

per m2 

per day)

Measured

Annual

Flux

(g CH4

per m2 

per year)

Conversion

Factor

Estimated

Annual

Flux

(g CH4

per m2 

per year)

Used

Annual

Flux

(g CH4

per m2 

per year)

Reference
The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

191

Swamp VA C FW 470.3 171.2 171.2 Chanton et al. (1992)

Maple/Gum 

Forested Swamp VA C FW 0.5 0.5 Harriss et al. (1982)

Emergent Tidal 

Freshwater Marsh VA C FW 96.2 96.2 Neubauer et al.(2000)

Oak Swamp (Bank 

Site) VA C FW 117.0 43.7 0.37 42.6 43.7 Wilson et al. (1989)

Emergent Macrophytes (Peltandra) VA C FW 155.0 56.4 56.4 Wilson et al. (1989)

Emergent Macrophytes (Smartweed) VA C FW 83.0 30.2 30.2 Wilson et al. (1989)

Ash Tree Swamp VA C FW 152.0 55.3 55.3 Wilson et al. (1989)

Bog WA C FW 73.0 26.6 26.6 Lansdown et al. (1992)

Lowland Shrub and 

Forested Wetland

WI T FW 12.4 12.4 Werner et al. (2003)

Sphagnum/Eriophorum (Poor Fen) WV C FW 6.6 2.4 2.4 Yavitt et al. (1990)

Sphagnum/Shrub 

(Fen) WV C FW 0.1 0.0 0.0 Yavitt et al. (1990)

Polytrichum/Shrub 

(Fen) WV C FW -0.1 0.0 0.0 Yavitt et al. (1990)

Sphagnum/Forest WV C FW 9.6 3.5 3.5 Yavitt et al. (1990)

Sedge Meadow WV C FW 1.5 0.5 0.5 Yavitt et al. (1990)

Beaver Pond WV C FW 250.0 91.0 91.0 Yavitt et al. (1990)

Low Gradient Headwater Stream WV C FW 300.0 109.2 109.2 Yavitt et al. (1990)

Sphagnum/Eriophorum WV C FW 52.1 19.0 0.37 18.9 19.0 Yavitt et al. (1993)

Polytrichum WV C FW 41.1 15.0 0.37 15.0 15.0 Yavitt et al. (1993)

Sphagnum/Shrub WV C FW 4.4 1.6 0.37 1.6 1.6 Yavitt et al. (1993)

Salt Marsh DE C SW 0.5 0.2 0.2 Bartlett et al. (1985)

Red Mangroves FL C SW 4.2 1.4 1.4 Bartlett et al. (1989)

Dwarf Red Mangrove

FL C SW 81.9 27.9 27.9 Bartlett et al. (1989)

High Marsh FL C SW 3.9 1.3 1.3 Bartlett et al. (1985)

Salt Marsh FL C SW 0.6 0.2 0.2 Bartlett et al. (1985)

Salt Water Mangroves

FL C SW 4.0 1.4 1.4 Harriss et al. (1988)

Salt Marsh GA C SW 13.4 4.6 4.6 Bartlett et al. (1985)

Short Spartina 

Marsh - High Marsh GA C SW 145.2 53.1 0.37 49.5 53.1 King and Wiebe (1978

Mid Marsh GA C SW 15.8 5.8 0.37 5.4 5.8 King and Wiebe 

(1978)

Tall Spartina Marsh 

- Low Marsh GA C SW 1.2 0.4 0.34 0.4 0.4 King and Wiebe 

(1978)

Intermediate Marsh LA C SW 912b Alford et al. (1997)

Salt Marsh LA C SW 15.7 5.7 0.36 5.4 5.7 DeLaune et al. (1983)

Brackish LA C SW 267.0 97.0 91.1 97.0 DeLaune et al. (1983)

Salt Marsh LA C SW 4.8 1.7 0.35 1.6 1.7 DeLaune et al. (1983)

Brackish LA C SW 17.0 6.4 0.38 5.8 6.4 DeLaune et al. (1983)

Habitat State Methoda Salt/

Fresh

Daily

Average

Flux

(mg CH4

per m2 

per day)

Measured

Annual

Flux

(g CH4

per m2 

per year)

Conversion

Factor

Estimated

Annual

Flux

(g CH4

per m2 

per year)

Used

Annual

Flux

(g CH4

per m2 

per year)

Reference

b Outlier that was removed from further analysis.
The U.S. Climate Change Science Program Appendix F

192

Cypress Swamp 

- Floodplain SC C SW 1.5 0.5 0.5 Bartlett et al. (1985)

Salt Marsh SC C SW 0.4 0.1 0.1 Bartlett et al. (1985)

Salt Marsh VA C SW 3.0 1.3 0.43 1.0 1.3 Bartlett et al. (1985)

Salt Marsh VA C SW 5.0 1.2 0.24 1.7 1.2 Bartlett et al. (1985)

Salt Meadow VA C SW 2.0 0.4 0.22 0.7 0.4 Bartlett et al. (1985)

Salt Marsh VA C SW -0.8 -0.3 -0.3 Bartlett et al. (1985)

Salt Marsh VA C SW 1.5 0.5 0.5 Bartlett et al. (1985)

Salt Meadow VA C SW -1.9 -0.6 -0.6 Bartlett et al. (1985)

Tidal Salt Marsh VA C SW 16.0 5.6 0.35 5.5 5.6 Bartlett et al. (1987)

Tidal Brackish Marsh VA C SW 64.6 22.4 0.35 22.0 22.4 Bartlett et al. (1987)

Tidal Brackish/Fresh 

Marsh VA C SW 53.5 18.2 0.34 18.2 18.2 Bartlett et al. (1987)

Freshwater

n 32 18 74 88

Arithmetic Mean 32.1 0.36 38.6 36.0

Arithmetic Standard Error 7.9 0.02 6.0 5.0

Geometric Mean 8.1 7.1 7.6

Geometric Standard Error 2.1 0.82 2.2

Saltwater

n 13 12 25 25

Arithmetic Mean 16.9 0.34 9.8 10.3

Arithmetic Standard Error 7.8 0.02 4.1 4.4

Geometric Mean 5.0 1.3 1.3

Geometric Standard Error 2.0 0.2 3.3

Habitat State Methoda Salt/

Fresh

Daily

Average

Flux

(mg CH4

per m2 

per day)

Measured

Annual

Flux

(g CH4

per m2 

per year)

Conversion

Factor

Estimated

Annual

Flux

(g CH4

per m2 

per year)

Used

Annual

Flux

(g CH4

per m2 

per year)

Reference
The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

APPENDIX G

193

New pCO2 Database for Coastal Ocean Waters 

Surrounding North America

Lead Authors: Francisco P. Chavez, MBARI; Taro Takahashi, Columbia Univ.

Contributing Authors: Wei-Jun Cai, Univ. Ga.; Gernot Friederich, MBARI; Burke Hales, Oreg. State Univ.; 

Rik Wanninkhof, NOAA; Richard A. Feely, NOAA

A database for the partial pressure of carbon dioxide 

(pCO2), temperature, and salinity in surface waters 

within about 1,000 km from the shore of the North 

American continent has been assembled. About 550,000 

seawater pCO2 observations were made from 1979 to 

2004 by the authors and collaborators of Chapter 15. 

The pCO2 data have been obtained by a method using 

an infrared gas analyzer or gas-chromatograph for the 

determination of CO2 concentrations in a carrier gas 

equilibrated with seawater at a known temperature and 

total pressure. The precision of pCO2 measurements 

has been estimated to be about ± 0.7% on average. The 

quality-controlled data are archived at http://www.ldeo.

columbia.edu/res/pi/CO2.

The zonal distribution of the surface water pCO2, sea 

surface temperature (SST), and salinity data shows that 

the greatest variability is confined within 300 km from 

the shores of both the Atlantic and Pacific. Observations 

made in various years were combined into a single year 

and were averaged into 1° × 1° pixels (approximately NS 100 km by E-W 80 km) for the analysis. Accordingly, 

the results represent a climatological mean condition 

over the past 25 years. Finer resolutions (10 × 10 km) 

may be desirable for some areas close to shore because 

of outflow of estuarine and river waters and upwelling. However, for this study, which is aimed at a broad 

picture of waters surrounding the continent, the fine 

scale measurements have been incorporated into the 

1° × 1° pixels. In addition, data with salinities of less 

than 16.0 are considered to be inland waters and have 

been excluded from the analysis.

Climatological monthly and annual mean values for 

pCO2 in each zone were computed first. Then, the 

air-sea pCO2 difference, which represents the thermodynamic driving potential for air-sea CO2 gas transfer, 

was estimated using the atmospheric CO2 concentration 

data. Finally, the net air-sea CO2 flux was computed 

using transfer coefficients estimated on the basis of 

climatological mean monthly wind speeds using the 

(wind speed)2 formulation of Wanninkhof (1992). The 

transfer coefficient depends on the state of turbulence 

above and below the air-sea interface and is commonly 

parameterized as a function of wind speeds (corrected 

to 10 m above the sea surface). However, selection of 

wind data is problematic because wind speeds vary 

with the time scale (hourly, diurnal, or seasonal). 

For example, fluxes calculated for the South Atlantic 

Bight from 6-h mean wind speeds in the NCEP/NCAR 

version 2 file (1° × 1° mean) were lower than those 

estimated using the monthly mean. This discrepancy 

suggests that ships used commonly for coastal carbon studies tend to be small and, hence, are rarely at 

sea under high wind conditions, so observations are 

biased toward lower winds. Taking into account that 

the observations have been made infrequently over 

multiple years, the gas transfer coefficients estimated 

from climatological mean monthly wind speeds may be 

more representative. The Schmidt number is computed 

using measured SST and climatological mean salinity 

(DaSilva et al., 1994). The flux values in a given month 

are then averaged to yield a climatological mean flux 

(and standard deviation) for each month. This procedure 

assumes implicitly that the seawater pCO2 changes at 

much slower rates in space and time than the wind 

speed and that the seawater pCO2 does not correlate 

with the wind speed.
The U.S. Climate Change Science Program Appendix G

194
GLOSSARY AND ACRONYMS

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

195

GLOSSARY

afforestation

the process of establishing trees on land that has 

lacked forest cover for a very long period of time or 

has never been forested

anthropogenic

human-induced

apparent consumption

the amount or quantity expressed by the following 

formula: production + imports – exports +/– changes 

in stocks

biomass

the mass of living organic matter (plant and animal) 

in an ecosystem; biomass also refers to organic matter 

(living and dead) available on a renewable basis for 

use as a fuel; biomass includes trees and plants (both 

terrestrial and aquatic), agricultural crops and wastes, 

wood and wood wastes, forest and mill residues, animal wastes, livestock operation residues, and some 

municipal and industrial wastes

carbon sequestration

the process of increasing the carbon content of a carbon reservoir other than the atmosphere; often used 

narrowly to refer to increasing the carbon content of 

carbon pools in the biosphere and distinguished from 

physical or chemical collection of carbon followed by 

injection into geologic reservoirs, which is generally 

referred to as “carbon capture and storage”

carbon cycle

the term used to describe the flow of carbon (in various forms such as carbon dioxide [CO2], organic matter, and carbonates) through the atmosphere, ocean, 

terrestrial biosphere, and lithosphere

carbon equivalent

the amount of carbon in the form of CO

2 that would 

produce the same effect on the radiative balance of 

the Earth’s climate system; applicable in this report 

to greenhouse gases such as methane (CH

4

)

carbon intensity

the relative amount of carbon emitted per unit of energy or fuels consumed

coastal waters

the region within 100 km from shore in which processes 

unique to coastal marine environments influence the 

partial pressure of CO

2 in surface sea waters

CO

2 equivalent

the amount of CO

2 that would produce the same effect 

on the radiative balance of the Earth’s climate system as 

another greenhouse gas, such as CH

4

CO

2 fertilization

the phenomenon in which plant growth increases (and 

agricultural crop yields increase) due to the increased 

rates of photosynthesis of plant species in response to 

elevated concentrations of CO

2 in the atmosphere

decarbonization

reduction in the use of carbon-based energy sources as 

a proportion of total energy supplies or increased use of 

carbon-based fuels with lower values of carbon content 

per unit of energy content

deforestation

the process of removing or clearing trees from forested 

land

dry climates

climates where the ratio of mean annual precipitation to 

potential evapotranspiration is less than 1.0

ecosystem

a community (i.e., an assemblage of populations of 

plants, animals, fungi, and microorganisms that live in 

an environment and interact with one another, forming, 

together, a distinctive living system with its own composition, structure, environmental relations, development, 

and function) and its environment treated together as a 

functional system of complementary relationships and 

transfer and circulation of energy and matter

energy intensity

the relative amount or ratio of the consumption of energy 

to the resulting amount of output, service, or activity (i.e.,

expressed as energy per unit of output)

feebates

systems of progressive vehicle taxes on purchases of less 

efficient new vehicles and subsidies for more efficient 

new vehicles
The U.S. Climate Change Science Program Glossary and Acronyms

196 

fossil fuels

fuels such as coal, petroleum, and natural gas derived from 

the chemical and physical transformation (fossilization) 

of the remains of plants and animals that lived during the 

Carboniferous Period 360–286 million years ago

global warming potential

a factor describing the radiative forcing impact (e.g., warming of the atmosphere) of one unit mass of a given greenhouse gas relative to the warming caused by a similar mass 

of CO2; CH4, for example, has a GWP of 23

greenhouse gases

gases including water vapor, CO2, CH4, nitrous oxide, and 

halocarbons that trap infrared heat, warming the air near the 

surface and in the lower levels of the atmosphere

leakage

The part of emissions reductions in Annex B countries that 

may be offset by an increase of the emission in the non-constrained countries above their baseline levels. This can occur 

through (1) relocation of energy-intensive production in 

non-constrained regions; (2) increased consumption of fossil 

fuels in these regions through decline in the international 

price of oil and gas triggered by lower demand for these energies; and (3) changes in incomes (and thus in energy demand) 

because of better terms of trade. “Leakage” also refers to 

the situation in which a carbon sequestration activity (e.g.,

tree planting) on one piece of land inadvertently, directly 

or indirectly, triggers an activity, which in whole or part, 

counteracts the carbon effects of the initial activity

mitigation

a human intervention to reduce the sources of or to enhance 

the sinks of greenhouse gases

net ecosystem exchange

the net flux of carbon between the land and the atmosphere, 

typically measured using eddy covariance techniques; note: 

NEE and NEP are equivalent terms but are not always identical because of measurement and scaling issues, and the 

sign conventions are reversed; positive values of NEE (net 

ecosystem exchange with the atmosphere) usually refer to 

carbon released to the atmosphere (i.e., a source), and negative values refer to carbon uptake (i.e., a sink)

net ecosystem production

the net carbon accumulation within the ecosystem after all 

gains and losses are accounted for, typically measured using 

ground-based techniques; by convention, positive values of 

NEP represent accumulations of carbon by the ecosystem, 

and negative values represent carbon loss

net primary production

the net uptake of carbon by plants in excess of respiratory 

loss

North America

the combined land area of Canada, the United States of 

America, and Mexico and their coastal waters

North American Carbon Program

a multidisciplinary research program, supported by a 

number of different U.S. federal agencies through a variety 

of intramural and extramural funding mechanisms and 

award instruments, to obtain scientific understanding of 

North America’s carbon sources and sinks and of changes 

in carbon stocks needed to meet societal concerns and to 

provide tools for decision makers

ocean acidification

the phenomenon in which the pH of the oceans becomes 

more acidic due to increased levels of CO2 in the atmosphere 

which, in turn, increase the amount of dissolved CO2 in 

sea water

option

a choice among a set of possible measures or alternatives

peatlands

areas characterized as having an organic layer thickness 

of at least 40 cm.

permafrost

soils or rocks that remain below 0°C for at least two consecutive years

pool/reservoir

any natural region or zone, or any artificial holding area, 

containing an accumulation of carbon or carbon-bearing 

compounds or having the potential to accumulate such 

substances

reforestation

the process of establishing a new forest by planting or 

seeding trees in an area where trees have previously been 

removed

sink

in general, any process, activity, or mechanism which removes a greenhouse gas or a precursor of a greenhouse gas 

or aerosol from the atmosphere; in this report, a sink is any 

regime or pool in which the amount of carbon is increasing 

(i.e., is being accumulated or stored)
197

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

source

in general, any process, activity, or mechanism which releases a greenhouse gas or a precursor of a greenhouse gas 

or aerosol into the atmosphere; in this report, a source is any 

regime or pool in which the amount of carbon is decreasing 

(i.e., is being released or emitted)

stocks

the amount or quantity contained in the inventory of a pool 

or reservoir

temperate zones

regions of the earth’s surface located above 30o latitude and 

below 66.5o latitude

trend

a systematic change over time

tropical zones

regions located between the earth’s equator and 30o latitude 

(this area includes subtropical regions)

uncertainty

a term used to describe the range of possible values around 

a best estimate, sometimes expressed in terms of probability 

or likelihood (see Preface, this report)

wet climates

climates where the ratio of mean annual precipitation to 

potential evapotranspiration is greater than 1.0

wetlands

areas that are inundated or saturated by surface water 

or groundwater at a frequency and duration sufficient to 

support—and that, under normal circumstances, do support—a prevalence of vegetation typically adapted for life 

in saturated soil conditions, including swamps, marshes, 

bogs, and similar areas

ACRONYMS AND ABBREVIATIONS

μatm microatmosphere (a measure of 

pressure)

ACEEE American Council for an EnergyEfficient Economy

CAFE Corporate Average Fuel Economy

CAIT Climate Analysis Indicators Tool

CAST Council for Agricultural Science 

and Technology

CBO U.S. Congressional Budget Office

CCSP U.S. Climate Change Science 

Program

CCTP Climate Change Technology 

Program

CDIAC Carbon Dioxide Information 

Analysis Center

CEC California Energy Commission

CH4 methane

CIEEDAC Canadian Industrial Energy EndUse Data and Analysis Centre

CO carbon monoxide

CO2 carbon dioxide

CO3 carbonate

COP Conference of Parties

DOC dissolved organic carbon

DOE U.S. Department of Energy

DOT U.S. Department of Transportation 

EIA Energy Information Administration 

EPA U.S. Environmental Protection 

Agency

ESCOs energy services companies

FAO Food and Agriculture Organization 

FWMS freshwater mineral-soil

g gram

GAO U.S. Government Accountability 

Office

GDP gross domestic product

GHG greenhouse gas

Gt C gigatons of carbon (billions of 

metric tons; i.e., petagrams)

GWP global warming potential

ha hectare

HCO3 bicarbonate

ICLEI International Council for Local 

Environmental Initiatives 

(now known as International 

Governments for Local 

Sustainability)

IOOS Integrated Ocean Observing 

System

IPCC Intergovernmental Panel on Climate 

Change
The U.S. Climate Change Science Program Glossary and Acronyms

198 

IWG Interlaboratory Working Group

kg kilogram

km kilometer

L liter

LEED Leadership in Energy and 

Environment Design

m meter

MAP mean annual precipitation

Mt C megatons of carbon (millions of 

metric tons; i.e., teragrams)

N2O nitrous oxide (also, dinitrogen 

oxide)

NACP North American Carbon Program

NAO North Atlantic oscillation

NAS U.S. National Academy of Sciences 

NASA National Aeronautics and Space 

Administration

NATS North American Transportation 

Statistics

NCAR National Center for Atmospheric 

Research

NCEP National Centers for Environmental 

Prediction; National Commission 

on Energy Policy

NEE net ecosystem exchange

NEP net ecosystem productivity

NGO non-governmental organization

NO2 nitrogen dioxide

NOAA National Oceanic and Atmospheric 

Administration

NOx oxides of nitrogen

NPP net primary productivity

NRC National Research Council

NRCS Natural Resources Conservation 

Service

NSF National Science Foundation

NWI National Wetland Inventory

OCCC Ocean Carbon and Climate Change

pCO2 partial pressure of carbon dioxide in 

units of microatmospheres or ppm

PDO Pacific decadal oscillation

PET potential evapotranspiration

PJ petajoules

ppm parts per million by volume

PPP purchasing power parity

RGGI Regional Greenhouse Gas Initiative

SAP Synthesis and Assessment Product

SBSTA Subsidiary Body for Scientific and 

Technological Advice

SOCCR State of the Carbon Cycle Report

μatm microatmospheres or 10-6

atmospheres

UNFCCC United Nations Framework 

Convention on Climate Change

USDA U.S. Department of Agriculture

VOCs volatile organic compounds

WBCSD World Business Council for 

Sustainable Development
REFERENCES

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

199

EXECUTIVE SUMMARY

REFERENCES

IPCC, 2000: Land Use, Land-use Change and Forestry. 

A Special Report of the Intergovernmental Panel on 

Climate Change [Watson, R.T., I.R. Noble, B. Bolin, 

N.H. Ravindranath, D.J. Verado, and D.J. Dokken

(eds.)]. Cambridge University Press, Cambridge, 

United Kingdom and New York, NY, USA, 388 pp.

IPCC, 2001: Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third 

Assessment Report of the Intergovernmental Panel 

on Climate Change [Houghton, J.T., Y. Ding, D.J. 

Griggs, M. Noguer, P.J. van der Linden, X. Dai, K. 

Maskell, and C.A. Johnson (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New 

York, NY, USA, 881 pp.

IPCC, 2007: Summary for Policymakers. In: Climate 

Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment 

Report of the Intergovernmental Panel on Climate 

Change [Solomon, S., D. Qin, M. Manning, Z. Chen, 

M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller 

(eds.)]. Cambridge University Press, Cambridge, 

United Kingdom and New York, NY, USA.

Marland, G., T.A. Boden, and R.J. Andres, 2006:

Global, regional, and national fossil fuel CO2 emissions. In: Trends: A Compendium of Data on Global 

Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department 

of Energy, Oak Ridge, TN. Available at http://cdiac.

esd.ornl.gov/trends/trends.htm

CHAPTER 1 REFERENCES

Caldeira, K. and M.E. Wickett, 2003: Anthropogenic 

carbon and ocean pH. Nature, 425(6956), 365-366.

Caldeira, K., M.G. Morgan, D. Baldocchi, P.G. Brewer, 

C.-T.A. Chen, G.-J. Nabuurs, N. Nakicenovic, and 

G.P. Robertson, 2004: A portfolio of carbon management options. In: The Global Carbon Cycle: Integrating Humans, Climate, and the Natural World

[Field, C.B. and M.R. Raupach (eds.)]. Island Press, 

Washington, DC, pp. 103-129.

Canadell, J.G., D. Pataki, R. Gifford, R.A. Houghton, Y. 

Lou, M.R. Raupach, P. Smith, and W. Steffen, 2007: 

Saturation of the terrestrial carbon sink. In: Terrestrial Ecosystems in a Changing World, [Canadell, J.G., 

D. Pataki, and L. Pitelka (eds.)]. The IGBP Series. 

Springer-Verlag, Berlin Heidelberg, pp. 59-78.

Cash, D. and W. Clark, 2001: From Science to Policy: 

Assessing the Assessment Process. Faculty Research 

Working Paper 01-045, Kennedy School of Government, Harvard University, Cambridge, MA. Available at 

http://ksgnotes1.harvard.edu/Research/wpaper.nsf/RWP/

RWP01-045 

Cash, D., W. Clark, F. Alcock, N. Dickson, N. Eckley, D. Guston, J. Jäger, and R. Mitchell, 2003: Knowledge systems 

for sustainable development. Proceedings of the National 

Academy of Sciences, 100(14), 8086-8091.

Casperson, J.P., S.W. Pacala, J.C. Jenkins, G.C. Hurtt, P.R. 

Moorcraft, and R.A. Birdsey, 2000: Contributions of landuse history to carbon accumulation in U.S. Forests. Science, 

290(5494), 1148-1151.

CCSP (U.S. Climate Change Science Program), 2003: Strategic Plan for the U.S. Climate Change Science Program. 

A Report by the Climate Change Science Program and the 

Subcommittee on Global Change Research, Climate Change 

Science Program Office, Washington, DC, 211 pp.

DOE (U.S. Department of Energy), 1997: Technology Opportunities to Reduce Greenhouse Gas Emissions. U.S. Department of Energy, Washington, DC, 95 pp.

Dilling, L., S.C. Doney, J. Edmonds, K.R. Gurney, R.C. Harriss, D. Schimel, B. Stephens, and G. Stokes, 2003: The role 

of carbon cycle observations and knowledge in carbon management. Annual Review of Environment and Resources, 

28, 521-558.

Ehhalt, D., M. Prather, F. Dentener, E. Dlugokencky, E. Holland, I. Isaksen, J. Katima, V. Kirchhoff, P. Matson, P. 

Midgley, and M. Wang, 2001: Atmospheric chemistry and 

greenhouse gases. In: Climate Change 2001: The Scientific 

Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate 

Change [Houghton, J.T., Y. Ding, D.J. Griggs, M. Noguer, 

P.J. van der Linden, X. Dai, K. Maskell, and C.A. Johnson 

(eds.)]. Cambridge University Press, Cambridge, United 

Kingdom, pp. 239–287.

EIA (Energy Information Administration), 2005: Historical 

Data Overview. U.S. Department of Energy. Available at 

http://www.eia.doe.gov/overview_hd.html; http://cdiac.

ornl.gov/ftp/trends/emis/meth-reg.htm 

Fan, S., M. Gloor, J. Mahlman, S. Pacala, J. Sarmiento, T. Takahashi, and P. Tans, 1998: A large terrestrial carbon sink in 

North America implied by atmospheric and oceanic carbon 

dioxide data and models. Science, 282(5388), 442-446.

Foley, J.A. and N. Ramankutty, 2004: A primer on the terrestrial carbon cycle: hat we don’t know but should. In: The 

Global Carbon Cycle: Integrating Humans, Climate and 

the Natural World. [Field, C.B. and M.R. Raupauch, (eds.)] 

Island Press, Washington DC, pp. 279-294.

Friedlingstein, P., P. Cox, R. Betts, L. Bopp, W. von Bloh, V. 

Brovkin, P. Cadule, S. Doney, M. Eby, I. Fung, G. Bala, J. 

John, C. Jones, F. Joos, T. Kato, M. Kawamiya, W. Knorr, 
The U.S. Climate Change Science Program References

200 

K. Lindsay, H.D. Matthews, T. Raddatz, P. Rayner, C. Reick, 

E. Roeckner, K.-G. Schnitzler, R. Schnur, K. Strassmann, A.J. 

Weaver, C. Yoshikawa, and N. Zeng, 2006: Climate-carbon 

cycle feedback analysis: results from the C4

MIP model intercomparison. Journal of Climate, 19(14), 3337-3353.

Goodale, C.L., M.J. Apps, R.A. Birdsey, C.B. Field, L.S. Heith, 

R.A. Houghton, J.C. Jenkins, G.H. Kholmaier, W. Kurz, S. Liu, 

G.-J. Nabuurs, S. Nilsson, and A.Z. Shvidenko, 2002: Forest 

carbon sinks in the Northern Hemisphere. Ecological Applications, 12(3), 891-899.

Greenblatt, J.B. and J.L. Sarmiento, 2004: Variability and climate 

feedback mechanisms in ocean uptake of CO2. In: The Global 

Carbon Cycle: Integrating Humans, Climate, and the Natural 

World [Field, C.B. and M.R. Raupach (eds.)]. Island Press, 

Washington, DC, pp. 257-275. 

Gurney, K.R., R.M. Law, A.S. Denning, P.J. Rayner, D. Baker, 

P. Bousquet, L. Bruhwiler, Y.-H. Chen, P. Ciais, S. Fan, I.Y. 

Fung, M. Gloor, M. Heimann, K. Higuchi, J. John, T. Maki, 

S. Maksyutov, K. Masarie, P. Peylin, M. Prather, B.C. Pak, J. 

Randerson, J. Sarmiento, S. Taguchi, T. Takahashi, and C.-W. 

Yue, 2002: Towards robust regional estimates of CO2 sources and sinks using atmospheric transport models. Nature, 

415(6872), 626-630.

Hoffert, M.I., K. Caldeira, G. Benford, D.R. Criswell, C. Green, 

H. Herzog, A.K. Jain, H.S. Kheshgi, K.S. Lackner, J.S. Lewis, 

H.D. Lightfoot, W. Manheimer, J.C. Mankins, M.E. Mauel, L.J. 

Perkins, M.E. Schlesinger, T. Volk, and T.M.L. Wigley, 2002: 

Advanced technology paths to global climate stability: energy 

for a greenhouse planet. Science, 298(5595), 981-987.

Houghton, R.A., J.L. Hackler, and K.T. Lawrence, 1999: The 

U.S. carbon budget: contributions from land-use change. Science, 285(5427), 574-578.

Houghton, R.A., 2002: Magnitude, distribution and causes of terrestrial carbon sinks and some implications for policy. Climate 

Policy, 2, 71-88.

Houghton, R.A., 2003: The contemporary carbon cycle. In: Treatise on Geochemistry, Volume 8 Biogeochemistry [Schlesinger, 

W.H. (ed.)]. Elsevier Ltd, New York, pp. 473-513.

IPCC, 2001: Climate Change 2001: Synthesis Report. A Contribution of Working Groups I, II, and III to the Third Assessment 

Report of the Intergovernmental Panel on Climate Change

[Watson, R.T., and the Core Writing Team (eds.)]. Cambridge 

University Press, Cambridge, United Kingdom and New York, 

NY, 398 pp.

Jones, C.D., P.M. Cox, and C. Huntingford, 2006: Climate-carbon 

cycle feedbacks under stabilization: uncertainty and observational constraints. Tellus B, 58(5), 603-613.

Joos, F. and I.C. Prentice, 2004: A paleo-perspective on changes 

in atmospheric CO2 and climate. In: The Global Carbon Cycle: 

Integrating Humans, Climate, and the Natural World [Field, 

C.B. and M.R. Raupach (eds.)]. Island Press, Washington, DC, 

pp. 165-186.

Keeling, C.D. and T.P. Whorf, 2005: Atmospheric CO2 records 

from sites in the SIO air sampling network. In: Trends: A Compendium of Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, TN. Available at http://cdiac.

esd.ornl.gov/trends/trends.htm

Kirschbaum, M.U.F. and A.L. Cowie, 2004: Giving credit where 

credit is due: a practical method to distinguish between human 

and natural factors in carbon accounting. Climatic Change,

67(2-3), 417-436.

Liu, K.K., K. Iseki, and S.-Y. Chao, 2000: Continental margin carbon fluxes. In: The Changing Ocean Carbon Cycle [Hansen, 

R., H.W. Ducklow, and J.G. Field (eds.)]. Cambridge University Press, Cambridge, United Kingdom, pp. 187–239.

Marland, G., T.A. Boden, and R.J. Andres, 2003: Global, regional, and national CO2 emissions. In: Trends: A Compendium of 

Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department 

of Energy, Oak Ridge, TN, USA. Available at http://cdiac.esd.

ornl.gov/trends/trends.htm

Marland, G., T.A. Boden, and R.J. Andres, 2006: Global, regional, and national CO2 emissions. In: Trends: A Compendium of 

Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department 

of Energy, Oak Ridge, TN, USA. Available at http://cdiac.esd.

ornl.gov/trends/trends.htm

Nowak, R.S., D.S. Ellsworth, and S.D. Smith, 2004: Functional 

responses of plants to elevated atmospheric CO2- do photosynthetic and productivity data from FACE experiments support 

early predictions? New Phytologist, 162(2), 253-280.

Orr, J.C., V.J. Fabry, O. Aumont, L. Bopp, S.C. Doney, R.A. 

Feely, A. Gnanadesikan, N. Gruber, A. Ishida, F. Joos, R.M. 

Key, K. Lindsay, E. Maier-Reimer, R. Matear, P. Monfray, A. 

Mouchet, R.G. Najjar, G.K. Plattner, K.B. Rodgers, C.L. Sabine, J.L. Sarmiento, R. Schlitzer, R.D. Slater, I.J. Totterdell, 

M.F. Weirig, Y. Yamanaka, and A. Yool, 2005: Anthropogenic 

ocean acidification over the twenty-first century and its impact 

on calcifying organisms, Nature, 437(7059), 681-686.

Pacala, S.W., G.C. Hurtt, D. Baker, P. Peylin, R.A. Houghton, 

R.A. Birdsey, L. Heath, E.T. Sundquist, R.F. Stallard, P. Ciais, P. Moorcroft, J.P. Caspersen, E. Shevliakova, B. Moore, 

G. Kohlmaier, E. Holland, M. Gloor, M.E. Harmon, S.M. Fan, 

J.L. Sarmiento, C.L. Goodale, D. Schimel, and C.B. Field, 

2001: Consistent land- and atmosphere-based U.S. carbon sink 

estimates. Science, 292(5525), 2316-2320.

Parson, E.A., 2003: Protecting the Ozone Layer: Science and 

Strategy. Oxford University Press, Oxford, United Kingdom, 

400 pp.

Prentice, I.C., G.D. Farquhar, M.J.R. Fasham, M.L. Goulden, 

M. Heimann, V.J. Jaramillo, H.S. Kheshgi, C. Le Quéré, R.J. 

Scholes, and D.W.R. Wallace, 2001: The carbon cycle and 

atmospheric carbon dioxide. In: Climate Change 2001: The 

Scientific Basis. Contribution of Working Group I to the Third 

Assessment Report of the Intergovernmental Panel on Climate 

Change [J. T. Houghton, Y. Ding, D. J. Griggs, M. Noguer, P. J. 

van der Linden, X. Dai, K. Maskell, and C. A. Johnson (eds.)]. 
201

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

Cambridge University Press, Cambridge, United Kingdom and 

New York, pp. 183-237.

Prinn, R.G., 2004: Non-CO2 greenhouse gases. In: The Global 

Carbon Cycle: Integrating Humans, Climate, and the Natural 

World [Field, C.B. and M.R. Raupach (eds.)]. Island Press, 

Washington, DC, pp. 205-216.

Running, S.W., R.R. Nemani, F.A. Heinsch, M. Zhao, M. Reeves, 

and H. Hashimoto, 2004: A continuous satellite-derived measure of global terrestrial primary production. BioScience, 54(6), 

547-560.

Sabine, C.L., M. Heiman, P. Artaxo, D.C.E. Bakker, C.-T.A. Chen, 

C.B. Field, N. Gruber, C. LeQuéré, R.G. Prinn, J.E. Richey, P. 

Romero-Lankao, J.A. Sathaye, and R. Valentini, 2004: Current status and past trends of the carbon cycle. In: The Global 

Carbon Cycle: Integrating Humans, Climate, and the Natural 

World [Field, C.B. and M.R. Raupach (eds.)]. Island Press, 

Washington, DC, pp. 17-44.

Schaefer, K., A.S. Denning, N. Suits, J. Kaduk, I. Baker, S. Los, 

and L. Prihodko, 2002: Effect of climate on interannual variability of terrestrial CO2 fluxes. Global Biogeochemical Cycles, 16, 1102, doi:10.1029/2002GB001928.

Schimel, D.S., J. Melillo, H. Tian, A.D. McGuire, D. Kicklighter, 

T. Kittel, N. Rosenbloom, S. Running, P. Thornton, D. Ojima, 

W. Parton, R. Kelly, M. Sykes, R. Neilson, and B. Rizzo, 2000: 

Contribution of increasing CO2 and climate to carbon storage 

by ecosystems in the United States. Science, 287(5460), 2004-

2006.

Sundquist, E.T. and K. Visser, 2003: The geological history of the 

carbon cycle. In: Treatise on Geochemistry, Volume 8 Biogeochemistry [Schlesinger, W.H. (ed.)]. Elsevier Ltd, New York, 

pp. 425-472.

Turner, D.P., G.J. Koerper, M.E. Harmon, and J.J. Lee, 1995: A 

carbon budget for forests of the conterminous United States. 

Ecological Applications, 5(2), 421-436.

CHAPTER 2 REFERENCES

Andres, R.J., D.J. Fielding, G. Marland, T.A. Boden, N. Kumar, 

and A.T. Kearney, 1999: Carbon dioxide emissions from fossilfuel use, 1751-1950. Tellus B, 51(4), 759-765.

Archer, D., H. Kheshgi, and E. Maier-Reimer, 1998: Dynamics of 

fossil fuel CO2 neutralization by marine CaCO3. Global Biogeochemical Cycles, 12(2), 259-276.

Bacastow, R. and C.D. Keeling, 1973: Atmospheric carbon dioxide and radiocarbon in the natural carbon cycle. II. Changes 

from A.D. 1700 to 2070 as deduced from a geochemical reservoir. In: Carbon and the Biosphere [Woodwell, G.M. and E.V. 

Pecan (eds.)]. U.S. Department of Commerce, Springfield, VA, 

pp. 86-135. 

Bachelet, D., R.P. Neilson, T. Hickler, R.J. Drapek, J.M. Lenihan, M.T. Sykes, B. Smith, S. Sitch, and K. Thonicke, 2003: 

Simulating past and future dynamics of natural ecosystems in 

the United States. Global Biogeochemical Cycles, 17(2), 1045, 

doi:10.1029/2001GB001508.

Baker, D.F., R.M. Law, K.R. Gurney, P. Rayner, P. Peylin, A.S. 

Denning, P. Bousquet, L. Bruhwiler, Y.H. Chen, P. Ciais, I.Y. 

Fung, M. Heimann, J. John, T. Maki, S. Maksyutov, K. Masarie, M. Prather, B. Pak, S. Taguchi, and Z. Zhu, 2006: TransCom 3 inversion intercomparison: impact of transport model 

errors on the interannual variability of regional CO2 fluxes, 

1988-2003. Global Biogeochemical Cycles, 20, GB1002, 

doi:10.1029/2004GB002439.

Baldocchi, D. and R. Valentini, 2004: Geographic and temporal 

variation of carbon exchange by ecosystems and their sensitivity to environmental perturbations. In: The Global Carbon 

Cycle: Integrating Humans, Climate, and the Natural World

[Field, C.B. and M.R. Raupach (eds.)]. Island Press, Washington, DC, pp. 295-316.

Birdsey, R.A. and L.S. Heath, 1995: Carbon changes in U.S. forests. In: Productivity of America’s Forests and Climate Change

[Joyce, L.A. (ed.)]. General Technical Report RM-GTR-271, 

U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station, Fort Collins, CO, 

pp. 56-70.

Bousquet, P., P. Peylin, P. Ciais, C.L. Quéré, P. Friedlingstein, and 

P.P. Tans, 2000: Regional changes in carbon dioxide fluxes of 

land and oceans since 1980. Science, 290(5495), 1342-1346.

Broecker, W.S., T.H. Peng, and T. Takahashi, 1980: A strategy for 

the use of bomb-produced radiocarbon as a tracer for the transport of fossil fuel CO2 into the deep-sea source regions. Earth 

and Planetary Science Letters, 49(2), 463-468.

Caldeira, K. and M.E. Wickett, 2003: Anthropogenic carbon and 

ocean pH. Nature, 425(6956), 365-366.

Chen, J.M., W. Ju, J. Cihlar, D. Price, J. Liu, W. Chen, J. Pan, A. 

Black, and A. Barr, 2003: Spatial distribution of carbon sources 

and sinks in Canada’s forests. Tellus B, 55(2), 622-641.

Cramer, W., A. Bondeau, F.I. Woodward, I.C. Prentice, R.A. Betts, V. Brovkin, P.M. Cox, V.A. Fisher, J.A. Foley, A.D. Friend, 

and C. Kucharik, 2001: Global response of terrestrial ecosystem structure and function to CO2 and climate change: results 

from six dynamic global vegetation models. Global Change 

Biology, 7(4), 357-373.

Cramer, W., D.W. Kicklighter, A. Bondeau, B. Moore III, G. 

Churkina, B. Nemry, A. Ruimy, A.L. Schloss, J. Kaduk, and 

participants of the Potsdam NPP Model Intercomparison, 1999: 

Comparing global models of terrestrial net primary productivity (NPP): overview and key results. Global Change Biology, 

5(Suppl. 1), 1-15.

DeFries, R.S., C.B. Field, I. Fung, J. Collatz, and L. Bounoua, 

1999: Combining satellite data and biogeochemical models to 

estimate global effects of human-induced land cover change 

on carbon emissions and primary productivity. Global Biogeochemical Cycles, 13(3), 803-815.

DOE EIA (U.S. Department of Energy, Energy Information Administration), 2006. Available at http://www.eia.doe.gov/environment.html

Dukes, J., 2003: Burning buried sunshine: human consumption of 

ancient solar energy. Climatic Change, 61(1-2), 31-44.
The U.S. Climate Change Science Program References

202 

Enting, I.G., 2002: Inverse Problems in Atmospheric Constituent 

Transport. Cambridge University Press, Cambridge, Untied 

Kingdom, 392 pp.

Falkowski, P.G., M.E. Katz, A.J. Milligan, K. Fennel, B.S. Cramer, M.P. Aubry, R.A. Berner, M.J. Novacek, and W.M. Zapol, 

2005: The rise of oxygen over the past 205 million years and 

the evolution of large placental mammals. Science, 309(5744), 

2202-2204. 

Feely, R.A., C.L. Sabine, K. Lee, W. Berelson, J. Kleypas, V.J. 

Fabry, and F.J. Millero, 2004: Impact of anthropogenic CO2

on the CaCO3 system in the oceans. Science, 305(5682), 362-

366.

Friedli, H., H. Lötscher, H. Oeschger, U. Siegenthaler, and B. 

Stauffer, 1986: Ice core record of 13C/12C ratio of atmospheric 

CO2 in the past two centuries. Nature, 324(6094), 237-238.

Giampietro, M., S. Ulgiati, and D. Pimentel, 1997: Feasibility of 

large-scale biofuel production: does an enlargement of scale 

change the picture? Bioscience, 47(9), 587-600.

Gloor, M., N. Gruber, J. Sarmiento, C.L. Sabine, R.A. Feely, and 

C. Rodenbeck, 2003: A first estimate of present and preindustrial air-sea CO2 flux patterns based on ocean interior carbon 

measurements and models. Geophysical Research Letters, 

30(1), 1010, doi:10.1029/2002GL015594.

Goodale, C.L., M.J. Apps, R.A. Birdsey, C.B. Field, L.S. Heath, 

R.A. Houghton, J.C. Jenkins, G.H. Kohlmaier, W. Kurz, S.R. 

Liu, G.J. Nabuurs, S. Nilsson, and A.Z. Shvidenko, 2002: Forest carbon sinks in the Northern Hemisphere. Ecological Applications, 12(3), 891-899.

Graham, P.J., 2003: Potential for climate change mitigation 

through afforestation: an economic analysis of fossil fuel substitution and carbon sequestration benefits. Agroforestry Systems, 59(1), 85-95.

Greenblatt, J.B. and J.L. Sarmiento, 2004: Variability and climate 

feedback mechanisms in ocean uptake of CO2. In: The Global 

Carbon Cycle: Integrating Humans, Climate, and the Natural 

World [Field, C.B. and M.R. Raupach (eds.)]. Island Press, 

Washington, DC, pp. 257-275.

Gruber, N., P. Friedlingstein, C.B. Field, R. Valentini, M. Heimann, J.E. Richey, P. Romero-Lankao, E.-D. Schulze, and 

C.-T.A. Chen, 2004: The vulnerability of the carbon cycle in 

the 21st century: an assessment of carbon-climate-human interactions. In: The Global Carbon Cycle: Integrating Humans, 

Climate, and the Natural World [Field, C.B. and M.R. Raupach 

(eds.)]. Island Press, Washington, DC, pp. 45-76.

Gurney, K.R., R.M. Law, A.S. Denning, P.J. Rayner, D. Baker, 

P. Bousquet, L. Bruhwiler, Y.H. Chen, P. Ciais, S.M. Fan, I.Y. 

Fung, M. Gloor, M. Heimann, K. Higuchi, J. John, E. Kowalczyk, T. Maki, S. Maksyutov, P. Peylin, M. Prather, B.C. Pak, 

J. Sarmiento, S. Taguchi, T. Takahashi, and C.W. Yuen, 2003: 

TransCom 3 CO2 inversion intercomparison: 1. annual mean 

control results and sensitivity to transport and prior flux information. Tellus B, 55(2), 555-579.

Gurney, K.R., R.M. Law, A.S. Denning, P.J. Rayner, B.C. Pak, 

D. Baker, P. Bousquet, L. Bruhwiler, Y.H. Chen, P. Ciais, I.Y. 

Fung, M. Heimann, J. John, T. Maki, S. Maksyutov, P. Peylin, 

M. Prather, and S. Taguchi, 2004: Transcom 3 inversion intercomparison: model mean results for the estimation of seasonal 

carbon sources and sinks. Global Biogeochemical Cycles, 18, 

GB1010, doi:10.1029/2003GB002111.

Hansen, J., L. Nazarenko, R. Ruedy, M. Sato, J. Willis, A. Del 

Genio, D. Koch, A. Lacis, K. Lo, S. Menon, T. Novakov, J. 

Perlwitz, G. Russell, G.A. Schmidt, and N. Tausnev, 2005: 

Earth’s energy imbalance: confirmation and implications. Science, 308(5727), 1431-1435.

Heath, J., E. Ayres, M. Possell, R.D. Bardgett, H.I.J. Black, H. 

Grant, P. Ineson, and G. Kerstiens, 2005: Rising atmospheric 

CO2 reduces sequestration of root-derived soil carbon. Science, 

309(5741), 1711-1713.

Hegerl, G.C., F.W. Zwiers, P. Braconnot, N.P. Gillett, Y. Luo, 

J.A.M. Orsini, N. Nicholls, J.E. Penner, and P.A. Stott, 2007: 

Understanding and Attributing Climate Change. In: Climate 

Change 2007: The Physical Science Basis. Contribution of 

Working Group I to Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., Qin, D., 

Manning, M., Chen, Z., Marquis, M., Averyt, K. B., Tignor, 

M., and Miller, H. L. (eds.)]. Cambridge University Press, 

Cambridge, United Kingdom and New York, pp. 665-745.

Hoffert, M.I., K. Caldeira, G. Benford, D.R. Criswell, C. Green, 

H. Herzog, A.K. Jain, H.S. Kheshgi, K.S. Lackner, J.S. Lewis, 

H.D. Lightfoot, W. Manheimer, J.C. Mankins, M.E. Mauel, L.J. 

Perkins, M.E. Schlesinger, T. Volk, and T.M.L. Wigley, 2002: 

Advanced technology paths to global climate stability: energy 

for a greenhouse planet. Science, 298(5595), 981-987.

Houghton, R.A. 1999: The annual net flux of carbon to the atmosphere from changes in land use 1850-1990. Tellus B, 51(2), 

298-313.

Houghton, R.A., J.L. Hackler, and K.T. Lawrence, 1999: The 

U.S. carbon budget: contributions from land-use change. Science, 285(5427), 574-578.

Jacobson, A.R., S.E. Mikaloff-Fletcher, N. Gruber, J.L. Sarmiento, M. Gloor, and TransCom Modelers, 2007: A joint atmosphere-ocean inversion for surface fluxes of carbon dioxide. 

1. Methods and global-scale fluxes. Global Biogeochemical 

Cycles, 21, doi:10.1029/2005GB002556.

Joos, F. and I.C. Prentice, 2004: A paleo-perspective on changes 

in atmospheric CO2 and climate. In: The Global Carbon Cycle: 

Integrating Humans, Climate, and the Natural World [Field, 

C.B. and M.R. Raupach (eds.)]. Island Press, Washington, DC, 

pp. 165-186.

Keeling, C.D., R.B. Bacastow, A.E. Bainbridge, C.A. Ekdahl, 

P.R. Guenther, and L.S. Waterman, 1976: Atmospheric carbon 

dioxide variations at Mauna Loa Observatory, Hawaii. Tellus, 

28(6), 538-551.

Keeling, R.F., S.C. Piper, and M. Heimann, 1996: Global and 

hemispheric CO2 sinks deduced from changes in atmospheric 

O2 concentration. Nature, 381(6579), 218-221.
203

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

Keeling, R.F. and B.B. Stephens, 2001: Antarctic sea ice and the 

control of Pleistocene climate instability. Paleoceanography, 

16(1), 112-131.

Kirschbaum, M.U.F., 2003: To sink or burn? A discussion of the 

potential contributions of forests to greenhouse gas balances 

through storing carbon or providing biofuels. Biomass and 

Bioenergy, 24(4-5), 297-310.

Kurz, W.A. and M.J. Apps, 1999: A 70-year retrospective analysis 

of carbon fluxes in the Canadian forest sector. Ecological Applications, 9(2), 526-547.

Law, R.M., Y.-H. Chen, K.R. Gurney, and TransCom 3 Modellers, 

2003: TransCom 3 CO2 inversion intercomparison: 2. sensitivity of annual mean results to data choices. Tellus B, 55(2), 

580-595.

Le Quéré, C. and N. Metzl, 2004: Natural processes regulating 

the ocean uptake of CO2. In: The Global Carbon Cycle: Integrating Humans, Climate, and the Natural World [Field, C.B. 

and M.R. Raupach (eds.)]. Island Press, Washington, DC, pp. 

243-256.

Marland, G. and R.M. Rotty, 1984: Carbon dioxide emissions 

from fossil fuels: a procedure for estimation and results for 

1950-1982. Tellus B, 36(4), 232-261.

Martin, J.H., 1990: Glacial-interglacial CO2 change: the iron hypothesis. Paleoceanography, 5(1), 1-13.

Masarie, K.A. and P.P. Tans, 1995: Extension and integration 

of atmospheric carbon dioxide data into a globally consistent 

measurement record. Journal of Geophysical Research (Atmospheres), 100(D6), 11593-11610.

Matear, R.J. and B.I. McNeil, 2003: Decadal accumulation of anthropogenic CO2 in the Southern Ocean: a comparison of CFCage derived estimates to multiple-linear regression estimates. 

Global Biogeochemical Cycles, 17(4), 1113, doi:10.1029/

2003GB002089.

Matsumoto, K., J.L. Sarmiento, R.M. Key, O. Aumont, J.L. Bullister, K. Caldeira, J.M. Campin, S.C. Doney, H. Drange, J.C. 

Dutay, M. Follows, Y. Gao, A. Gnanadesikan, N. Gruber, A. 

Ishida, F. Joos, K. Lindsay, E. Maier-Reimer, J.C. Marshall, 

R.J. Matear, P. Monfray, A. Mouchet, R. Najjar, G.K. Plattner, 

R. Schlitzer, R. Slater, P.S. Swathi, I.J. Totterdell, M.F. Weirig, 

Y. Yamanaka, A. Yool, and J.C. Orr, 2004: Evaluation of ocean 

carbon cycle models with data-based metrics. Geophysical Research Letters, 31, L07303-07304.

McGillis, W.R., J.B. Edson, J.E. Hare, and C.W. Fairall. 2001: 

Direct covariance air-sea CO2 fluxes. Journal of Geophysical 

Research, 106(C8):16729-16745.

Newsam, G.N. and I.G. Enting, 1988: Inverse problems in atmospheric constituent studies: I. determination of surface sources 

under a diffusive transport approximation. Inverse Problems, 

4(4), 1037-1054.

Norby, R.J., E.H. DeLucia, B. Gielen, C. Calfapietra, C.P. Giardina, J.S. King, J. Ledford, H.R. McCarthy, D.J.P. Moore, R. 

Ceulemans, P. De Angelis, A.C. Finzi, D.F. Karnosky, M.E. 

Kubiske, M. Lukac, K.S. Pregitzer, G.E. Scarascia-Mugnozza, 

W.H. Schlesinger, and R. Oren, 2005: Forest response to elevated CO2 is conserved across a broad range of productivity. 

Proceedings of the National Academy of Sciences, 102(50), 

18052-18056.

Oren, R., D.S. Ellsworth, K.H. Johnsen, N. Phillips, B.E. Ewers, C. Maier, K.V.R. Schäfer, H. McCarthy, G. Hendrey, S.G. 

McNulty, and G.G. Katul, 2001: Soil fertility limits carbon 

sequestration by forest ecosystems in a CO2-enriched atmosphere. Nature, 411(6836), 469-472.

Orr, J.C., V.J. Fabry, O. Aumont, L. Bopp, S.C. Doney, R.A. 

Feely, A. Gnanadesikan, N. Gruber, A. Ishida, F. Joos, R.M. 

Key, K. Lindsay, E. Maier-Reimer, R. Matear, P. Monfray, A. 

Mouchet, R.G. Najjar, G.K. Plattner, K.B. Rodgers, C.L. Sabine, J.L. Sarmiento, R. Schlitzer, R.D. Slater, I.J. Totterdell, 

M.F. Weirig, Y. Yamanaka, and A. Yool, 2005: Anthropogenic 

ocean acidification over the twenty-first century and its impact 

on calcifying organisms. Nature, 437(7059), 681-686.

Pacala, S. and R. Socolow, 2004: Stabilization wedges: solving 

the climate problem for the next 50 years with current technologies. Science, 305(5686), 968-972.

Pacala, S.W., G.C. Hurtt, D. Baker, P. Peylin, R.A. Houghton, 

R.A. Birdsey, L. Heath, E.T. Sundquist, R.F. Stallard, P. Ciais, P. Moorcroft, J.P. Caspersen, E. Shevliakova, B. Moore, 

G. Kohlmaier, E. Holland, M. Gloor, M.E. Harmon, S.M. Fan, 

J.L. Sarmiento, C.L. Goodale, D. Schimel, and C.B. Field, 

2001: Consistent land- and atmosphere-based U.S. carbon sink 

estimates. Science, 292(5525), 2316-2320.

Petit, J.R., J. Jouzel, D. Raynaud, N.I. Barkov, J.-M. Barnola, I. 

Basile, M. Bender, J. Chappellaz, M. Davis, G. Delaygue, M. 

Delmotte, V.M. Kotlyakov, M. Legrand, V.Y. Lipenkov, C. Lorius, L. Pépin, C. Ritz, E. Saltzman, and M. Stievenard, 1999: 

Climate and atmospheric history of the past 420,000 years from 

the Vostok ice core, Antarctica. Nature, 399(6735), 429-436.

Peylin, P., P. Bousquet, C. Le Quere, S. Sitch, P. Friedlingstein, 

G. McKinley, N. Gruber, P. Rayner, and P. Ciais, 2005: Multiple constraints on regional CO2 flux variations over land 

and oceans. Global Biogeochemical Cycles, 19, GB1011, 

doi:10.1029/2003GB002214.

Post, W.M., T.H. Peng, W.R. Emanuel, A.W. King, V.H. Dale, and 

D.L. Deangelis, 1990: The global carbon cycle. American Scientist, 78(4), 310-326.

Prentice, I.C., G.D. Farquhar, M.J.R. Fasham, M.L. Goulden, 

M. Heimann, V.J. Jaramillo, H.S. Kheshgi, C. Le Quéré, R.J. 

Scholes, and D.W.R. Wallace, 2001: The carbon cycle and 

atmospheric carbon dioxide. In: Climate Change 2001: The 

Scientific Basis. Contribution of Working Group I to the Third 

Assessment Report of the Intergovernmental Panel on Climate 

Change [J. T. Houghton, Y. Ding, D. J. Griggs, M. Noguer, P. J. 

van der Linden, X. Dai, K. Maskell, and C. A. Johnson (eds.)]. 

Cambridge University Press, Cambridge, United Kingdom and 

New York, pp. 183-237.

Rodenbeck, C., S. Houweling, M. Gloor, and M. Heimann, 2003: 

CO2 flux history 1982-2001 inferred from atmospheric data us-
The U.S. Climate Change Science Program References

204 

ing a global inversion of atmospheric transport. Atmospheric 

Chemistry and Physics, 3(6), 1919-1964.

Rousteenoja, K., T.R. Carter, K. Jylha, and H. Tuomenvirta, 2003: 

Future Climate in World Regions: An Intercomparison of Model-Based Projections for the New IPCC Emissions Scenarios. 

Finnish Environment Institute, Helsinki, pp. 83.

Running, S.W., R.R. Nemani, F.A. Heinsch, M.S. Zhao, M. 

Reeves, and H. Hashimoto, 2004: A continuous satellite-derived measure of global terrestrial primary production. Bioscience, 54(6), 547-560.

Sabine, C.L., R.A. Feely, N. Gruber, R.M. Key, K. Lee, J.L. 

Bullister, R. Wanninkhof, C.S. Wong, D.W.R. Wallace, B. 

Tilbrook, F.J. Millero, T.H. Peng, A. Kozyr, T. Ono, and A.F. 

Rios, 2004a: The oceanic sink for anthropogenic CO2. Science, 

305(5682), 367-371.

Sabine, C.L., M. Heiman, P. Artaxo, D.C.E. Bakker, C.-T.A. Chen, 

C.B. Field, N. Gruber, C. LeQuéré, R.G. Prinn, J.E. Richey, P. 

Romero-Lankao, J.A. Sathaye, and R. Valentini, 2004b: Current status and past trends of the carbon cycle. In: The Global 

Carbon Cycle: Integrating Humans, Climate, and the Natural 

World [Field, C.B. and M.R. Raupach (eds.)]. Island Press, 

Washington, DC, pp. 17-44.

Schimel, D., J. Melillo, H. Tian, A.D. McGuire, D. Kicklighter, 

T. Kittel, N. Rosenbloom, S. Running, P. Thornton, D. Ojima, 

W. Parton, R. Kelly, M. Sykes, R. Neilson, and B. Rizzo, 2000: 

Contribution of increasing CO2 and climate to carbon storage 

by ecosystems in the United States. Science, 287(5460), 2004-

2006.

Schimel, D.S., J.I. House, K.A. Hibbard, P. Bousquet, P. Ciais, 

P. Peylin, B.H. Braswell, M.J. Apps, D. Baker, A. Bondeau, J. 

Canadell, G. Churkina, W. Cramer, A.S. Denning, C.B. Field, 

P. Friedlingstein, C. Goodale, M. Heimann, R.A. Houghton, 

J.M. Melillo, B. Moore, D. Murdiyarso, I. Noble, S.W. Pacala, I.C. Prentice, M.R. Raupach, P.J. Rayner, R.J. Scholes, 

W.L. Steffen, and C. Wirth, 2001: Recent patterns and mechanisms of carbon exchange by terrestrial ecosystems. Nature, 

414(6860), 169-172.

Shaw, M.R., E.S. Zavaleta, N.R. Chiariello, E.E. Cleland, H.A. 

Mooney, and C.B. Field, 2002: Grassland responses to global 

environmental changes suppressed by elevated CO2. Science, 

298(5600), 1987-1990.

Siegenthaler, U. and H. Oeschger, 1987: Biospheric CO2 emissions during the past 200 years reconstructed by deconvolution 

of ice core data. Tellus B, 39(1-2), 140-154.

Sigman, D.M. and E.A. Boyle, 2000: Glacial/interglacial variations in atmospheric carbon dioxide. Nature, 407(6806), 859-

869.

Takahashi, T., R.A. Feely, R.F. Weiss, R. Wanninkhof, D.W. 

Chipman, S.C. Sutherland, and T.T. Takahashi, 1997: Global 

air-sea flux of CO2: an estimate based on measurements of seaair pCO2 difference. Proceedings of the National Academy of 

Sciences, 94(16), 8292-8299.

Takahashi, T., S.C. Sutherland, C. Sweeney, A. Poisson, N. Metzl, 

B. Tilbrook, N. Bates, R. Wanninkhof, R.A. Feely, C. Sabine, 

J. Olafsson, and Y. Nojiri, 2002: Global sea-air CO2 flux based 

on climatological surface ocean pCO2, and seasonal biological and temperature effects. Deep-Sea Research II, 49(9-10_, 

1601-1622.

Tarantola, A., 1987: Inverse Problem Theory: Methods for Data 

Fitting and Model Parameter Estimation. Elsevier, New York, 

630 pp.

Thoning, K.W., P.P. Tans, and W.D. Komhyr, 1989: Atmospheric 

carbon dioxide at Mauna Loa Observatory 2. Analysis of the 

NOAA GMCC data, 1974-1985. Journal of Geophysical Research, 94(D6), 8549-8565.

van der Werf, G.R., J.T. Randerson, G.J. Collatz, L. Giglio, P.S. 

Kasibhatla, A.F. Arellano, S.C. Olsen, and E.S. Kasischk, 

2004: Continental-scale partitioning of fire emissions during 

the 1997 to 2001 El Niño/La Niña period. Science, 303(5654), 

73-74.

Wanninkhof, R. and W. McGillis, 1999: A cubic relationship between air-sea CO2 exchange and wind speed. Geophysical Research Letters, 26(13), 1889-1892.

Wofsy, S.C., M.L. Goulden, J.W. Munger, S.-M. Fan, P.S. Bakwin, B.C. Daube, S.L. Bassow, and F.A. Bazzaz, 1993: Net 

exchange of CO2 in a mid-latitude temperate forest. Science, 

260(5112), 1314-1317.

CHAPTER 3 REFERENCES

Aldy, J.E., 2005: An environmental kuznets curve analysis of US 

state level carbon dioxide emissions. Journal of Environment 

and Development, 14(1), 58-72.

Ang, B.W. and F.Q. Zhang, 2000: A survey of index decomposition analysis in energy and environmental studies. Energy, 

25(12), 1149-1176.

Bradley, B.A., R.A. Houghton, J.F. Mustard, and S.P. Hamburg, 

2006: Invasive grass reduces aboveground carbon stocks in 

shrublands of the Western US. Global Change Biology, 12(10), 

1815-1822.

Cairns, M.A., P.K. Haggerty, R. Alvarez, B.H.J. De Jong, and I. 

Olmsted, 2000: Tropical Mexico’s recent land-use change: a 

region’s contribution to the global carbon cycle. Ecological 

Applications, 10(5), 1426-1441.

Casler, S.D. and A.Z. Rose, 1998: Carbon dioxide emissions in 

the US economy. Environmental and Resource Economics, 

11(3-4), 349-363.

Caspersen, J.P., S.W. Pacala, J.C. Jenkins, G.C. Hurtt, P.R. Moorcroft, and R.A. Birdsey, 2000: Contributions of land-use history to carbon accumulation in U.S. forests. Science, 290(5495), 

1148-1151.

Cox, P.M., R.A. Betts, C.D. Jones, S.A. Spall, and I.J. Totterdell, 

2000: Acceleration of global warming due to carbon-cycle 

feedbacks in a coupled climate model. Nature, 408(6809), 

184-187.

Davis, W.B., A.H. Sanstad, and J.G. Koomey, 2002: Contributions 

of weather and fuel mix to recent declines in US energy and 

carbon intensity. Energy Economics, 25(4), 375-396.
205

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

Defries, R.S., R.A. Houghton, M.C. Hansen, C.B. Field, D. Skole, 

and J. Townshend, 2002: Carbon emissions from tropical deforestation and regrowth based on satellite observations for the 

1980s and 1990s. Proceedings of the National Academy of Sciences, 99(22), 14256-14261.

EIA (Energy Information Administration), 2005: Historical Data 

Overview. U.S. Department of Energy. Available at http://

www.eia.doe.gov/overview_hd.html; http://cdiac.ornl.gov/ftp/

trends/emis/meth-reg.htm

Environment Canada, 2005: Canada’s Greenhouse Gas Inventory 1990-2003: Initial Submission. Greenhouse Gas Division, 

Environment Canada, Ottawa, Ontario, Canada. Available at 

http://unfccc.int/national_reports/annex_i_ghg_inventories/

national_inventories_submissions/items/2761.php

Environment Canada, 2006: National Inventory Report 1990-

2004: Greenhouse Gas Sources and Sinks in Canada. Greenhouse Gas Division, Environment Canada, Ottowa, Ontario, 

Canada. Available at http://www.cc.gc.ca/pdb/ghg/inventory_

report/2004_report/toc_e.cfm

Fan, S.-M., M. Gloor, J. Mahlman, S. Pacala, J. Sarmiento, T. 

Takahashi, and P. Tans, 1998: Atmospheric and oceanic CO2

data and models imply a large terrestrial carbon sink in North 

America. Science, 282(5388), 442-446. 

Flannigan, M.D., K.A. Logan, B.D. Amiro, W.R. Skinner, and 

B.J. Stocks, 2005: Future area burned in Canada. Climatic 

Change, 72(1), 1-16.

Gillett, N.P., A.J. Weaver, F.W. Zwiers, and M.D. Flannigan, 2004: 

Detecting the effect of climate change on Canadian forest 

fires. Geophysical Research Letters, 31, L18211, doi:10.1029/

2004GL020876

Goetz, S.J., A. Bunn, G. Fiske, and R.A. Houghton. 2005: Satellite-observed photosynthetic trends across boreal North America associated with climate and fire disturbance. Proceedings of 

the National Academy of Sciences, 102(38), 13521-13525.

Golove, W.H. and L.J. Schipper, 1998: Long-term trends in U.S. 

manufacturing energy consumption and carbon dioxide emissions. Energy, 21(7/8), 683-692.

Goodale, C.L., M.J. Apps, R.A. Birdsey, C.B. Field, L.S. Heath, 

R.A. Houghton, J.C. Jenkins, G.H. Kohlmaier, W. Kurz, S. Liu, 

G.J. Nabuurs, S. Nilsson, and A.Z. Shvidenko, 2002: Forest 

carbon sinks in the Northern Hemisphere. Ecological Applications, 12(3), 891-899.

Greening, L.A., W.B. Davis, L. Schipper, and M. Khrushch, 1997: 

Comparison of six decomposition methods: application to aggregate energy intensity for manufacturing in 10 OECD countries. Energy Economics, 19(3), 375-390.

Greening, L.A., W.B. Davis, and L. Schipper, 1998: Decomposition of aggregate carbon intensity for the manufacturing sector: 

comparison of declining trends from 10 OECD countries for 

the period 1971-1993. Energy Economics, 20(1), 43-65.

Greening, L.A., M. Ting, and W.B. Davis, 1999: Decomposition 

of aggregate carbon intensity for freight: trends from 10 OECD 

countries for the period 1971-1993. Energy Economics, 21(4), 

331-361.

Greening, L.A., M. Ting, and T.J. Krackler, 2001: Effects of 

changes in residential end-uses on aggregate carbon intensity: 

comparison of 10 OECD countries for the period 1970 through 

1993. Energy Economics, 23(2), 153-178.

Greening, L.A., 2004: Effects of human behavior on aggregate 

carbon intensity of personal transportation: comparison of 10 

OECD countries for the period 1970-1993. Energy Economics, 

26(1), 1-30.

Grossman, G.M. and A.B. Krueger, 1995: Economic growth and 

the environment. Quarterly Journal of Economics, 60(2), 

353-375.

Guo, L.B. and R.M. Gifford, 2002: Soil carbon stocks and land 

use change: a meta analysis. Global Change Biology, 8(4), 

345-360.

Gurney, K.R., R.M. Law, A.S. Denning, P.J. Rayner, B.C. Pak, 

D. Baker, P. Bousquet, L. Bruhwiler, Y.H. Chen, P. Ciais, I.Y. 

Fung, M. Heimann, J. John, T. Maki, S. Maksyutov, P. Peylin, 

M. Prather, and S. Taguchi, 2004: Transcom 3 inversion intercomparison: model mean results for the estimation of seasonal 

carbon sources and sinks. Global Biogeochemical Cycles, 

18, GB1010, doi:10.1029/2003GB002111.

Houghton, R.A., J.L. Hackler, and K.T. Lawrence, 1999: The 

U.S. carbon budget: contributions from land-use change. Science, 285(5427), 574-578.

Houghton, R.A. and J.L. Hackler, 2000: Changes in terrestrial 

carbon storage in the United States. 1. The roles of agriculture 

and forestry. Global Ecology and Biogeography, 9(12), 125-

144.

Houghton, R.A., J.L. Hackler, and K.T. Lawrence, 2000: Changes 

in terrestrial carbon storage in the United States. 2. The role of 

fire and fire management. Global Ecology and Biogeography, 

9(2), 145-170.

Hungate, B.A., J.S. Dukes, M.R. Shaw, Y. Luo, and C.B. Field, 

2003: Nitrogen and climate change. Science, 302(5650), 1512-

1513.

Hurtt, G.C., S.W. Pacala, P.R. Moorcroft, J. Caspersen, E. Shevliakova, R.A. Houghton, and B. Moore III, 2002: Projecting 

the future of the U.S. carbon sink. Proceedings of the National 

Academy of Sciences, 99(3), 1389-1394.

Jackson, R.B., J.L. Banner, E.G. Jobbagy, W.T. Pockman, and 

D.H. Wall, 2002: Ecosystem carbon loss with woody plant invasion of grasslands. Nature, 418(6898), 623-626.

Kahn, M.E., 2003: The geography of US pollution intensive trade: 

evidence from 1958 to 1994. Regional Science and Urban Economics, 33(4), 383-400.

Körner, C., R. Asshoff, O. Bignucolo, S. Hättenschwiler, S.G. 

Keel, S. Peláez-Riedl, S. Pepin, R.T.W. Siegwolf, and G. Zotz, 

2005: Carbon flux and growth in mature deciduous forest trees 

exposed to elevated CO2. Science, 309(5739), 1360-1362.

Lenzen, M., M. Wier, C. Cohen, H. Hayami, S. Pachauri, and R. 

Schaeffer, 2006: A comparative multivariate analysis of household energy requirements in Australia, Brazil, Denmark, India 

and Japan. Energy, 31(2-3), 181-207.
The U.S. Climate Change Science Program References

206 

Lindmark, M., 2004: Patterns of historical CO2 intensity transitions among high and low income countries. Explorations in 

Economic History, 41(4), 426-447.

Luo, Y., D. Hui, and D. Zhang, 2006: Elevated carbon dioxide 

stimulates net accumulations of carbon and nitrogen in terrestrial ecosystems: a meta-analysis. Ecology, 87(1), 53-63.

Masera, O.R., M.J. Ordóñez, and R. Dirzo, 1997: Carbon emissions from Mexican forests: current situation and long-term 

scenarios. Climatic Change, 35(3), 265-295.

Maddison, A., 2003: The World Economy: Historical Statistics. 

OECD, Paris, 384 pp.

Marland, G., T.A. Boden, and R.J. Andres, 2005: Global, regional, and national CO2 emissions. In: Trends: A Compendium of 

Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department 

of Energy, Oak Ridge, TN. Available at http://cdiac.esd.ornl.

gov/trends/trends.htm

Mitchell, B.R., 1998: International Historical Statistics: The 

Americas, 1750-1993. Stockton Press, New York, 4th ed., 830 

pp.

Oren, R., D.S. Ellsworth, K.H. Johnsen, N. Phillips, B.E. Ewers, C. Maier, K.V.R. Schäfer, H. McCarthy, G. Hendrey, S.G. 

McNulty, and G.G. Katul, 2001: Soil fertility limits carbon 

sequestration by forest ecosystems in a CO2-enriched atmosphere. Nature, 411(6836), 469-472.

Pacala, S.W., G.C. Hurtt, D. Baker, P. Peylin, R.A. Houghton, 

R.A. Birdsey, L. Heath, E.T. Sundquist, R.F. Stallard, P. Ciais, P. Moorcroft, J.P. Caspersen, E. Shevliakova, B. Moore, 

G. Kohlmaier, E. Holland, M. Gloor, M.E. Harmon, S.M. Fan, 

J.L. Sarmiento, C.L. Goodale, D. Schimel, and C.B. Field, 

2001: Consistent land- and atmosphere-based U.S. carbon sink 

estimates. Science, 292(5525), 2316-2320.

Pacala, S. and R. Socolow, 2004: Stabilization wedges: solving 

the climate problem for the next 50 years with current technologies. Science, 305(5686), 968-972.

Rothman, D.S., 1998: Environmental Kuznets curves—real progress or passing the buck: a case for consumption-based approaches. Ecological Economics, 25(2), 177-194.

Schaphoff, S., W. Lucht, D. Gerten, S. Sitch, W. Cramer, and I.C. 

Prentice, 2006: Terrestrial biosphere carbon storage under alternative climate projections. Climatic Change, 74(1-3), 97-

122.

Selden, T.M. and D. Song, 1994: Environmental quality and development—is there a Kuznets curve for air pollution emissions? Journal of Environmental Economics and Management, 

27(2), 147-162.

Skog, K.E. and G.A. Nicholson, 1998: Carbon cycling through 

wood products: the role of wood and paper products in carbon 

sequestration. Forest Products Journal, 48(7), 75-83. Available 

at http://www.fpl.fs.fed.us/documnts/pdf1998/skog98a.pdf 

Skog, K.E., K. Pingoud, and J.E. Smith, 2004: A method countries 

can use to estimate changes in carbon stored in harvested wood 

products and the uncertainty of such estimates. Environmental 

Management, 33 (Supplement 1), S65-S73.

Smith, J.E. and L.S. Heath, 2005: Land use change and forestry 

and related sections. In: Inventory of U.S. Greenhouse Gas 

Emissions and Sinks: 1990-2003. Excerpted, EPA 430-R05-003, U.S. Environmental Protection Agency. Available at 

http://yosemite.epa.gov/oar/globalwarming.nsf/content/ResourceCenterPublicationsGHGEmissions.html

Stallard, R.F., 1998: Terrestrial sedimentation and the carbon cycle: coupling weathering and erosion to carbon burial. Global 

Biogeochemical Cycles, 12(2), 231-257.

Suri, V. and D. Chapman, 1998: Economic growth, trade and energy: implications for the environmental Kuznets curve. Ecological Economics, 25(2), 195-208.

Westerling, A., H.G. Hidalgo, D.R. Cayan, and T.W. Swetnam, 

2006: Warming and earlier Spring increase western U.S. forest 

wildfire activity. Science, 313(5789), 940-943.

World Forest Institute, 2006: Wood Products Trade: North 

America Available at http://wfi.worldforestrycenter.org/trade2.htm

WRI (World Resources Institute), 2005: EarthTrends—The Environmental Information Portal. Available at http://earthtrends.

wri.org/ 

CHAPTER 4 REFERENCES 

AF&PA (American Forest & Paper Association and the U.S. Department of Energy) 2006: Forest Products Industry Technology Roadmap. Agenda 2020 Technology Alliance, Washington, 

DC, 54 pp.

Bohm, P. and C. Russell 1986: Comparative analysis of alternative policy instruments. In: Handbook of Natural Resource and 

Energy Economics [Kneese, A. and J. Sweeney (eds.)]. Vol. 2, 

Elsevier, New York, pp. 395-460.

Casler, S.D. and A. Rose, 1998. Carbon dioxide emissions in the 

U.S. economy: a structural decomposition analysis. Environmental and Resource Economics, 11(3-4), 349-363.

CBO (Congressional Budget Office), 2003: The Economic Costs 

of Fuel Economy Standards Versus a Gasoline Tax. Congress 

of the United States, Washington, DC, 24 pp.

CBO (Congressional Budget Office), 2006: Evaluating the Role 

of Prices and R&D in Reducing Carbon Dioxide Emissions. 

Congress of the United States, Washington, DC, 19 pp.

Croci, E. (ed.), 2005: The Handbook of Environmental Voluntary 

Agreements: Design, Implementation and Evaluation Issues, 

Springer, The Netherlands, 391 pp.

Darnall, N. and J. Carmin, 2003: The Design and Rigor of U. S. 

Voluntary Environmental Programs: Results from the Survey, 

North Carolina State University, Raleigh, 55 pp.

DOE (U.S. Department of Energy), 2006: Carbon Sequestration 

R&D Overview, CO2 capture and storage costs. Available at 

http://www.fossil.energy.gov/programs/sequestration/overview.html

DOE/EERE (U.S. Department of Energy, Energy Efficiency and 

Renewable Energy), 2006: Building America Puts Residential Building Research to Work. Washington, DC. Available at 

http://www.eere.energy.gov/buildings/building_america/
207

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

DOE/EIA (Energy Information Administration), 2006: Annual 

Energy Review 2006: U.S. Department of Energy, , Washington, DC, 401 pp. 

EIA (Energy Information Administration), 2003a: International 

Energy Outlook: 2003. DOE/EIA-0484(2003), U.S. Department of Energy, Washington, DC, 249 pp.

EIA (Energy Information Administration), 2003b: Analysis of 

S.139, the Climate Stewardship Act of 2003. SR/OIAF/2003-

02, U.S. Department of Energy, Washington, DC, 515 pp.

EIA (Energy Information Administration), 2005. Emissions of 

Greenhouse Gases in the United States, 2005., U.S. Department of Energy, Washington, DC, 106 pp. 

Ellerman, D., P. Joskow, R. Schmalansee, J. Montero, and E. Bailey, 2000: Markets for Clean Air: The U.S. Acid Rain Program, 

Cambridge University Press, New York, 384 pp.

Energy Modeling Forum (EMF), 2000: Costs of GHG Emissions 

Reduction, Stanford University, Palo Alto, CA.

EPA (Environmental Protection Agency), 2005: Greenhouse Gas 

Mitigation Potential in U.S. Forestry and Agriculture. EPA430-R-05-006, U.S. Environmental Protection Agency, Washington, DC, 154 pp.

Feng, Hongli, C.L. Kling, L.A. Kurkalova, and S. Secchi, 2003: 

Subsidies! The Other Incentive-Based Instrument: The Case 

of the Conservation Reserve Program. Working Paper 03-WP 

345, Center for Agricultural and Rural Development, Iowa 

State University, Ames, IA, 29 pp.

Greene, D.L., P.D. Patterson, M. Singh, and J. Li, 2005: Feebates, 

rebates and gas guzzler taxes: a study of incentives for increased fuel economy. Energy Policy, 33(6), 757–776.

Goulder, L.H., 2004: Induced Technological Change and Climate 

Policy. Pew Center on Global Climate Change, Washington, 

DC, 38 pp.

Grubb, M., C. Carraro and J. Schellnhuber 2006: Technological 

change for atmospheric stabilization: introductory overview to 

the innovation modeling comparison project, The Energy Journal, Special Issue on Endogenous Technological Change and 

the Economics of Atmospheric Stabilization, pp. 1-16.

Gupta, S., D. A. Tirpak, N. Burger, J. Gupta, N. Höhne, A. I. 

Boncheva, G. M. Kanoan, C. Kolstad, J. A. Kruger, A. Michaelowa, S. Murase, J. Pershing, T. Saijo, A. Sari, 2007: Policies, instruments and co-operative arrangements. In: Climate 

Change 2007: Mitigation. Contribution of Working Group 

III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [B. Metz, O.R. Davidson, P.R. 

Bosch, R. Dave, L.A. Meyer (eds.)]. Cambridge University 

Press, Cambridge, United Kingdom and New York, NY, USA, 

pp 745-807.

Harrison, K., 1999: Talking with the donkey: cooperative approaches to environmental protection, Journal of Industrial 

Ecology, 2(3), 51–72.

Herzog, H, 1999: The economics of CO2 capture. In: Greenhouse 

Gas Control Technologies [Reimer, P., B. Eliasson, A. Wokaum (eds.)]. Elsevier Science Ltd., Oxford, United Kingdom, 

pp. 101–106.

Hoffert, M.I., K. Calderia, A.K. Jain, E.F. Haites, L.D.D. Harvey, 

S.D. Potter, M.E. Schlesinger, S.H. Schneider, R.G. Watson, 

T.M.L. Wigley, and D.J. Wuebbles, 1998: Energy implications 

of future stabilization of atmospheric CO2 content. Nature, 

395(6705), 881–884.

Hoffert, M.I., K. Caldeira, G. Benford, D.R. Criswell, C. Green, 

H. Herzog, A.K. Jain, H.S. Kheshgi, K.S. Lackner, J.S. Lewis, 

H.D. Lightfoot, W. Manheimer, J.C. Mankins, M.E. Mauel, L.J. 

Perkins, M.E. Schlesinger, T. Volk, and T.M.L. Wigley, 2002: 

Advanced technology paths to global climate stability: energy 

for a greenhouse planet. Science, 298(5595), 981-987.

IEA (International Energy Agency), 2006a: Key World Energy 

Statistics, 2006, IEA, Paris, France, 82 pp. 

I EA (I nter national Energ y Agency), 2006b: Energ y 

T e c h n o l o g y P e r s p e c t i v e s : S c e n a r i o s a n d 

St rategies to 2050, I EA, Par is, France, 484 pp.

IPCC, 2000: Land Use, Land-use Change and Forestry. A Special 

Report of the Intergovernmental Panel on Climate Change

[Watson, R.T., I.R. Noble, B. Bolin, N.H. Ravindranath, D.J. 

Verado, and D.J. Dokken (eds.)]. Cambridge University Press, 

Cambridge, United Kingdom and New York, NY, USA, 388 pp.

IPCC, 2001: Climate Change 2001: The Scientific Basis. 

Contribution of Working Group I to the Third Assessment 

Report of the Intergovernmental Panel on Climate Change 

[Houghton, J.T., Y. Ding, D.J. Griggs, M. Noguer, P.J. 

van der Linden, X. Dai, K. Maskell, and C.A. Johnson 

(eds.)]. Cambridge University Press, Cambridge, 

United Kingdom and New York, NY, USA, 881 pp.

IPCC, 2005: IPCC Special Report on Carbon Dioxide Capture 

and Storage, Summary for Policymakers. Approved by the 8th 

Session of IPCC Working Group III, Montreal, Canada, 53 pp.

Jaccard, M., J. Nyboer, and B. Sadownik, 2002: The Cost 

of Climate Policy. University of British Columbia 

Press, Vancouver, British Columbia, Canada. 242 pp.

Jaccard, M., J. Nyboer, C. Bataille, and B. Sadownik, 2003a: 

Modeling the cost of climate policy: distinguishing between 

alternative cost definitions and long-run cost dynamics. The 

Energy Journal, 24(1), 49-73.

Jaccard, M., R. Loulou, A. Kanudia, J. Nyboer, A. Bailie, and 

M. Labriet, 2003b: Methodological contrasts in costing GHG 

abatement policies: optimization and simulation modeling of 

micro-economic effects in Canada. European Journal of Operations Research, 145(1), 148-164.

Jaccard, M., N. Rivers, C. Bataille, R. Murphy, J. Nyboer and 

B. Sadownik, 2006: Burning Our Money to Warm the Planet. 

Commentary No. 234, C.D. Howe Institute, Toronto, 31 pp. 

Kauppi, P., R. Sedjo, M. Apps, C. Cerri, T. Fujimori, H. Janzen, O. Krankina, W. Makundi, G. Marland, O. Masera, G.-J. 

Nabuurs, W. Razali, N.H. Ravindranath, 2001. Technological 

and economic potential of options to enhance, maintain and 

manage biological carbon reservoirs and geo-engineering. In: 

Climate Change 2001 - Mitigation. Contribution of Working 

Group III to the Third Assessment Report of Inter-Governmental Panel on Climate Change [Metz, B., O. Davidson, R. Swart, 
The U.S. Climate Change Science Program References

208 

and J. Pan (eds.)]. UNEP-WMO. Cambridge University Press, 

Cambridge, United Kingdom and New York, NY, USA, pp. 

301-343.

Kates, R., and T. Wilbanks, 2003: Making the global local: responding to climate change concerns from the bottom up. Environment, 45(3), 12-23.

King, A., and M. Lenox, 2000: Industry self-regulation without 

sanctions: the chemical industry’s responsible care program. 

Academy of Management Journal, 43(4), 698-716.

Marland, G., B.A. McCarl, and U.A. Schneider, 2001: Soil carbon: 

policy and economics. Climatic Change, 51(1), 101–117.

Martin, N., E. Worrell, M. Ruth, L. Price, R.N. Elliott, A.M. 

Shipley, and J. Thorne, 2001: Emerging Energy-Efficient Industrial Technologies. LBNL Report Number 46990, New 

York State Edition, published by American Council for an Energy-Efficient Economy (ACEEE), Washington DC, 183 pp.

National Academies, 2004: The Hydrogen Economy: Opportunities, Costs, Barriers, and R&D Needs. The National Academies Press, Washington, DC, 240 pp.

NRC (National Research Council) and National Academy of Engineering, 2004: Committee on Alternatives and Strategies for 

Future Hydrogen Production and Use. The National Academies. Washington, DC, 148 pp.

NCEP (National Commission on Energy Policy), 2005: Ending 

the Energy Stalemate: A Bipartisan Strategy to Meet America’s 

Energy Challenge. Washington, DC, 148 pp.

OECD (Organization for Economic Co-operation and Development), 2003a: Technology Innovation, Development and Diffusion. OECD and IEA Information Paper, COM/ENV/EPOC/

IEA/SLT(2003)4, Paris, France, 48 pp.

OECD (Organization for Economic Co-operation and Development), 2003b: Voluntary Approaches for Environmental 

Policy: Effectiveness, Efficiency and Usage in Policy Mixes. 

OECD, Paris, France, 143 pp.

Pacala, S. and R. Socolow, 2004: Stabilization wedges: solving 

the climate problem for the next 50 years with current technologies. Science, 305(5686), 968-972.

Parry, I.W.H., R. Williams, and L.H. Goulder, 1999: When can 

carbon abatement policies increase welfare? The fundamental 

role of distorted factor markets. Journal of Environmental Economics and Management, 37(1), 52–84.

Raupach, M., J.G. Canadell, D.C. Bakker, P. Ciais, M.J. Sans, 

J.Y. Fank, J.M. Melillo, P. Romero-Lankao, J.A. Sathaye, E.D. 

Schulze, P. Smith, and J. Tschirley, 2004: Atmospheric stabilization in the context of carbon-climate-human interactions. 

In: Toward CO2 Stabilization: Issues, Strategies, and Consequences [Field, C. and M. Raupach (eds.)]. Island Press, Washington, DC.

Rose, A., and G. Oladosu, 2002: Greenhouse gas reduction in the 

U.S.: identifying winners and losers in an expanded permit 

trading system. Energy Journal, 23(1), 1–18.

Sedjo, R.A., 2001: Forest ‘sinks’ as a tool for climate-change policymaking: a look at the advantages and challenges. Resources, 

143, 21–23.

Sedjo, R.A. and S.K. Swallow, 2002: Voluntary eco-labeling and 

the price premium. Land Economics, 87(2), 272–284. 

Stern, N., 2006: Stern Review on the Economics of Climate 

Change, Cambridge University Press, Cambridge, United 

Kingdom. Available at http://www.hm-treasury.gov.uk/independent_reviews/stern_review_economics_climate_change/

sternreview_index.cfm 

Stern, P.C and Fineberg, H.V. (eds.), 1996: Understanding Risk: 

Informing Decisions in a Democratic Society. National Academy Press, Washington, DC, 249 pp.

Swift, B., 2001: How environmental laws work: an analysis of the 

utility sector’s response to regulation of nitrogen oxides and 

sulfur dioxide under the Clean Air Act, Tulane Environmental 

Law Journal, 14(2), 309-425. 

Tietenberg, T., 2000: Environmental and Natural Resource Economics. 5th Edition, Addison-Wesley, New York, 630 pp.

Tietenberg, T. and D. Wheeler, 2001: Empowering the community: information strategies for pollution control. In: Frontiers 

of Environmental Economics [Folmer, H., H.L. Gabel, S. Gerking, and A. Rose (eds.)]. Edward Elgar, Cheltenham, United 

Kingdom, 417 pp.

USGBC (U.S. Green Building Council), 2005: LEED for New 

Construction-Rating System 2.2 U.S. Greeen Building Council, Washington, DC. 83pp. 

Welch, E.W., A. Mazur, and S. Bretschneider, 2000: Voluntary behavior by electric utilities: levels of adoption and contribution 

of the Climate Challenge Program to the reduction of carbon 

dioxide, Journal of Public Policy Analysis and Management, 

19(3), 407-426. 

Worrell, E., L.K. Price, and C. Galitsky, 2004: Emerging Energyefficient Technologies in Industry: Case Studies of Selected 

Technologies. Environmental Technologies Division, Lawrence Berkeley Laboratory, University of California at Berkeley, 67 pp.

CHAPTER 5 REFERENCES

Adler, P., R. Barrett, M. Bean, J. Birkoff, C. Ozawa, and E. Rudin, 1999: 

Managing Scientific and Technical Information in Environmental 

Cases: Principles and Practices for Mediators. U.S. Institute 

for Environmental Conflict Resolution, Tucson, AZ, 74 pp.

Agrawala, S., K. Broad, and D.H. Guston, 2001: Integrating 

climate forecasts and societal decision making: 

challenges to an emergent boundary organization. 

Science, Technology and Human Values, 26(4), 454-477.

Apps, M., J. Canadell, M. Heimann, V. Jaramillo, D. Murdiyarso, 

D. Schimel, and M. Manning, 2003: Expert Meeting Report: 

IPCC Meeting on Current Understanding of the Processes 

Affecting Terrestrial Carbon Stocks and Human Influences 

Upon Them. Geneva, Switzerland, July 21-23, 2003. 

Available at http://www.ipcc.ch/pub/carbon.pdf. 37 pp.

Cash, D.W., 2001: In order to aid in diffusing useful and practical information: agricultural extension and boundary organizations. Science, Technology and Human Values, 26, 431-453.
209

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

Cash, D., W. Clark, F. Alcock, N. Dickson, N. Eckley, D. Guston, 

J. Jäger, and R. Mitchell, 2003: Knowledge systems for sustainable development. Proceedings of the National Academy of 

Sciences, 100(14), 8086-8091.

Cash, D.W., J.C. Borck, A.G. Patt, 2006: Countering the loadingdock approach to linking science and decision making. Science, Technology and Human Values, 31(4), 465-494.

Curry, T., D. Reiner, S. Ansolabehere, and H. Herzog, How Aware 

is the Public of Carbon Capture and Storage? Presented at the 

Seventh International Conference on Greenhouse Gas Control 

Technologies, Vancouver, Canada, September 2004. Available 

at http://sequestration.mit.edu/bibliography/policy.html 

Denning, A.S., et al., 2005: Science Implementation Strategy for 

the North American Carbon Program. Report of the NACP Implementation Strategy Group, U.S. Carbon Cycle Interagency 

Working Group, U.S. Carbon Cycle Science Program, Washington, DC, 68 pp. Available at http://www.nacarbon.org/nacp/

documents.html 

Dilling, L., 2007: Towards science in support of decision making: 

characterizing the supply of carbon cycle science. Environmental Science and Policy, 10(1), 48-61.

Dilling, L., S.C. Doney, J. Edmonds, K.R. Gurney, R.C. Harris, D. 

Schimel, B. Stephens, and G. Stokes, 2003: The role of carbon 

cycle observations and knowledge in carbon management. Annual Review of Environment and Resources, 28, 521-558.

Douglas, M. and A. Wildavsky, 1984: Risk and Culture. University of California Press, Berkeley, CA, 221 pp. (1982 ed.)

Ehrmann, J. and B. Stinson, 1999: Joint fact-finding and the use 

of technical experts. In: The Consensus Building Handbook

[Susskind, L., J.T. Larmer, and S. McKearnan (eds.)]. Sage 

Publications, Thousand Oaks, CA, 1147 pp.

Farrell, A. and J. Jäger (eds.), 2005: Assessments of Regional and 

Global Environmental Risks: Designing Processes for the Effective Use of Science in Decision-Making. Resources for the 

Future, Washington, DC, 301 pp.

Gibbons, M., C. Limoges, and H. Nowotny, 1994: The New Production of Knowledge: The Dynamics of Science and Research 

in Contemporary Societies. Sage, London, 179 pp.

Environment Canada, 2005: Project Green: Moving Forward 

on Climate Change: A Plan for Honoring Our Kyoto Commitment. Available at http://www.climatechange.gc.ca/english/

newsroom/2005/plan05.asp 

Guston, D.H., 2001: Boundary organizations in environmental 

policy and science: An introduction. Science, Technology, & 

Human Values, 26(4), 399-408, Special Issue: Boundary Organizations in Environmental Policy and Science (Autumn 

2001).

Holling, C.S. (ed.), 1978: Adaptive Environmental Assessment 

and Management. John Wiley, New York, 377 pp.

Holling, C.S., 1995: What barriers? What bridges? In: Barriers 

and Bridges to the Renewal of Ecosystems and Institutions

[Gunderson L.H., C.S. Holling, and S.S. Light (eds.)]. Columbia University Press, New York, pp. 3-34.

IPCC, 2000: Land Use, Land-use Change and Forestry. A Special Report of the Intergovernmental Panel on Climate Change

[Watson, R.T., I.R. Noble, B. Bolin, N.H. Ravindranath, D.J. 

Verado, and D.J. Dokken (eds.)]. Cambridge University Press, 

Cambridge, United Kingdom and New York, NY, USA, 388 

pp.

IPCC, 2007: Climate Change 2007: The Physical Science Basis.

Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge University 

Press, Cambridge, United Kingdom and New York, NY, USA, 

1009 pp.

Lahsen, M., 1999: The detection and attribution of conspiracies: 

the controversy over chapter 8. In: Paranoia Within Reason: A 

Casebook on Conspiracy as Explanation. [Marcus, G.E. (ed.)]. 

University of Chicago Press, Chicago, IL, pp. 111-136.

Lahsen, M., 2007: Trust through participation? Problems of 

knowledge in climate decision making. In: The Social Construction of Climate Change. [Pettinger, Mary E. (ed.)]. Ashgate Publishing, pp. 173-196. Available at http://sciencepolicy.

colorado.edu/our_science_their_science/pubs/lahsen_2007_

pettenger1.pdf

Lahsen, M. and C. A. Nobre, 2007: Challenges of connecting 

international science and local level sustainability efforts: the 

case of the Large-Scale Biosphere-Atmosphere Experiment in 

Amazonia. Environmental Science & Policy, 10(1), 62-74.

Lemos, M.C. and B.J. Morehouse, 2005: The co-production of 

science and policy in integrated climate assessments. Global 

Environmental Change, 15(1), 57-68.

Martinez, J. and A. Fernandez-Bremauntz (eds.), 2004: Cambio 

climático: una visión desde Mexico. Secretaría de Medio Ambiente y Recursos Naturales, Instituto Nacional de Ecología, 

Mexico City, Mexico, 525 pp.

Mitchell, R.B., W.C. Clark, D.W. Cash, and F. Alcock, 2004: Science, scientists, and the policy process: lessons from global 

environmental assessments for the northwest forest. In: Forest Futures: Science, Politics and Policy for the Next Century

[Arabas, K. and J. Bowersox (eds.)]. Rowman and Littlefield, 

pp. 95-111.

Mitchell, R.B., W.C. Clark, D.W. Cash, and N.M. Dickson (eds.), 

2006: Global Environmental Assessments: Information and Influence. The MIT Press, Cambridge, MA, 344 pp.

Moser, S., 2005: Stakeholder involvement in the first U.S. national 

assessment of the potential consequences of climate variability 

and change: an evaluation, finally. In: Public Participation in 

Environmental Assessment and Decision Making. National Research Council, Committee on Human Dimensions of Global 

Change, NAS/NRC, Washington, DC (in press).

NRC (National Research Council), 1999: Making Climate Forecasts Matter. National Academy Press, Washington, DC, 175 

pp.

NRC (National Research Council), 2004: Committee to Review 

the U.S. Climate Change Science Program Strategic Plan. Im-
The U.S. Climate Change Science Program References

210 

plementing Climate and Global Change Research: A Review 

of the Final U.S. Climate Change Science Program Strategic 

Plan, National Academy Press, Washington, DC, 96 pp.

NRC (National Research Council), 2005: Roundtable on Science 

and Technology for Sustainability. Knowledge-Action Systems 

for Seasonal to Interannual Climate Forecasting: Summary of a 

Workshop. National Academy Press, Washington, DC, 32 pp. 

Parson, E.A., 2003: Protecting the Ozone Layer: Science and 

Strategy. Oxford University Press, Oxford, United Kingdom, 

400 pp.

Patt, A., P. Suarez, and C. Gwata, 2005a: Effects of seasonal climate forecasts and participatory workshops among subsistence 

farmers in Zimbabwe. Proceedings of the National Academy of 

Sciences, 102(35), 12623-12628.

Patt, A.G., R. Klein, and A. de la Vega-Leinert, 2005b: Taking the 

uncertainties in climate change vulnerability assessment seriously. Comptes Rendus Geosciences, 337(4), 411-424.

Pulwarty, R. S. and K.T. Redmond, 1997: Climate and salmon 

restoration in the Columbia River Basin: the role and usability 

of seasonal forecasts. Bulletin of the American Meteorological 

Society, 78(3), 381-396.

Richards, K., 2004: A brief overview of carbon sequestration 

economics and policy. Environmental Management, 33(4), 

545-558.

Sarmiento, J.L. and S.C. Wofsy, 1999: A U.S. Carbon Cycle 

Science Plan: A Report of the Carbon and Climate Working 

Group. U.S. Global Change Research Program, Washington, 

DC. Available at http://www.nacarbon.org/nacp/documents.

html 

Schröter, D., W. Cramer, R. Leemans, I.C. Prentice, M.B. Araújo, 

N.W. Arnell, A. Bondeau, H. Bugmann, T.R. Carter, C.A. Gracia, A.C. de la Vega-Leinert, M. Erhard, F. Ewert, M. Glendining, J.I. House, S. Kankaanpää, R.J.T. Klein, S. Lavorel, 

M. Lindner, M.J. Metzger, J. Meyer, T.D. Mitchell, I. Reginster, M. Rounsevell, S. Sabaté, S. Sitch, B. Smith, J. Smith, P. 

Smith, M.T. Sykes, K. Thonicke, W. Thuiller, G. Tuck, S. Zaehle, B. Zierl, 2005: Ecosystem service supply and vulnerability 

to global change in Europe. Science, 310(5752), 1333-1337.

Shackley, S., C. McLachlan, and C. Gough, 2005: The public 

perception of carbon dioxide capture and storage in the UK: 

results from focus groups and a survey. Climate Policy, 4(4), 

377-398.

Stokes, D.E., 1997: Pasteur’s Quadrant: Basic Science and Technological Innovation. Brookings Institution Press, Washington, 

DC, 180 pp.

U.S. Climate Change Science Program, 2003: Strategic Plan for 

the U.S. Climate Change Science Program. Last accessed February 20, 2006. Available at http://www.climatescience.gov 

U.S. Climate Change Science Program, 2006: Our Changing 

Planet: The US Climate Change Science Program for Fiscal 

Year 2006. A Report by the Climate Change Science Program 

and the Subcommittee on Global Change Research. Last accessed February 23, 2006, Washington, DC. Available at: 

http://www.climatescience.gov 

U.S. Department of State, 2004: U.S. Climate Change Policy: 

The Bush Administration’s Actions on Global Climate Change. 

Fact sheet released by the White House, Office of the Press 

Secretary Washington, DC, November 19, 2004. Available at 

http://www.state.gov/g/oes/rls/fs/2004/38641.htm 

Van den Belt, M., 2004: Mediated Modeling: A Systems Dynamic 

Approach to Environmental Consensus Building. Island Press, 

Washington, DC, 296 pp.

Van House, N.A., 2003: Digital libraries and collaborative knowledge construction. In: Digital Library Use: Social Practice in 

Design and Evaluation [Bishop, A.P., B.P. Buttenfield, and 

N.A. Van House (eds.)]. MIT Press, pp. 271-295.

Western Economic Diversification Canada, 2006: Government 

of Canada and Government of Alberta Announce $16.6 Million 

Worth of Joint Projects. Available at http://www.wd.gc.ca/mediacentre/2006/may23-02a_e.asp

Yaniv, I., 2004: Receiving other people’s advice: influence and 

benefit. Organizational Behavior and Human Decision Processes, 93(1), 1-13.

Part II OVERVIEW REFERENCES

Andres, R.J., D.J. Fielding, G. Marland, T.A. Boden, N. Kumar, 

and A.T. Kearney, 1999: Carbon dioxide emissions from fossilfuel use, 1751–1950. Tellus B, 51(4), 759–765.

Andres, R.J., J.S. Gregg, L.M. Losey, and G. Marland, 2005: 

Monthly Resolution Fossil-Fuel-Derived Carbon Dioxide 

Emissions for the Countries of the North American Carbon 

Program. Proceedings of the Seventh International Carbon 

Dioxide Conference, Broomfield, CO, September, 2005, pp. 

157–158.

Blasing, T.J., C.T. Broniak, and G. Marland, 2005a: The annual 

cycle of fossil-fuel carbon dioxide emissions in the United 

States. Tellus B, 57(2), 107–115. Available at http://cdiac.esd.

ornl.gov

Blasing, T.J., C. Broniak, and G. Marland, 2005b: State-by-state 

carbon dioxide emissions from fossil-fuel use in the United 

States 1960–2000. Mitigation and Adaptation Strategies for 

Global Change, 10(4), 659–674.

Environment Canada, 2005: Canada’s Greenhouse Gas Inventory: 1990–2003. National Inventory Report, April 15, 2005, 

Greenhouse Gas Division, Environment Canada, 339 pp. 

Gregg, J.S., 2005: Improving the Temporal and Spatial Resolution of Carbon Dioxide Emissions Estimates from Fossil-Fuel 

Consumption. A thesis submitted to the graduate faculty of the 

University of North Dakota, August, 2005, 404 pp. Available at 

http://cdiac.esd.ornl.gov

Gurney, K.R., Y.H. Chen, T. Maki, S.R. Kawa, A. Andrews, and 

Z. Zhu, 2005: Sensitivity of atmospheric CO2 inversion to seasonal and interannual variations in fossil-fuel emissions. Journal of Geophysical Research, 110(D10), 10308, doi:10.1029/

2004JD005373. 

IEA (International Energy Agency), 2005: CO2 Emissions from 

Fuel Combustion: 1971–2003. OECD/IEA, Paris, France, 

556 pp.
211

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

IPCC, 1997: Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories (3 Volumes). IPCC Technical Support 

Unit, Bracknell, United Kingdom, 3 volumes (looseleaf).

Losey, L.M., 2004: Monthly and Seasonal Estimates of Carbon 

Dioxide Emissions from Fossil Fuel Consumption in Canada, 

Mexico, Brazil, The United Kingdom, France, Spain, Italy, 

and Poland. A thesis submitted to the graduate faculty of the 

University of North Dakota, May, 2004, 328 pp. Available at 

http://cdiac.essd.ornl.gov

Marland, G., T. Boden, and R.J. Andres, 1995: Carbon dioxide 

emissions from fossil fuel burning: emissions coefficients and 

the global contribution of eastern European countries. Időjárás, 

99, 157–170.

Marland, G., T.A. Boden, and R.J. Andres, 2005: Global, regional, and national CO2 emissions. In: Trends: A Compendium of 

Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department 

of Energy, Oak Ridge, TN. Available at http://cdiac.esd.ornl.

gov/trends/trends.htm

Mexico, 2001: México: Segunda Comunicación Nacional ante la 

Convención Marco de las Naciones Unidas sobre el Cambio 

Climático. Comité Intersecretarial Sobre Cambio Climático, 

Secretaria de Medio Ambiente y Recursos Naturales (Semarnat), Mexico City, 374 pp.

Neumayer, E., 2004: National carbon dioxide emissions: geography matters. Area, 36(1), 33–40.

USEPA (U.S. Environmental Protection Agency), 2005: Inventory 

of U.S. Greenhouse Gas Emissions and Sinks: 1990–2003. EPA 

430-R-05-003, EPA, Washington, DC.

CHAPTER 6 REFERENCES

AAG (Association of American Geographers), 2003: Global 

Change and Local Places: Estimating, Understanding, and 

Reducing Greenhouse Gases. Cambridge University Press, 

Cambridge, United Kingdom, 270 pp.

Caldeira, K, D. Day, W. Fulkerson, M. Hoffert, 2005: Climate 

Change Technology Exploratory Research. Working paper, 

Climate Policy Center, Washington, DC, 10 pp. Available online at http://www.cpc-inc.org/

EIA (Energy Information Administration), 2004: Emissions of 

Greenhouse Gases in the United States, 2004. U.S. Department of Energy, , Washington, DC, 134 pp.

EIA (Energy Information Administration), 2005: International 

Energy Outlook, 2005. U.S. Department of Energy, , Washington, DC, 186 pp.

EIA (Energy Information Administration), 2006a: International 

Energy Outlook, 2006. U.S. Department of Energy, , Washington, DC, 192 pp.

EIA (Energy Information Administration), 2006b: Annual Energy 

Review 2006: U.S. Department of Energy, , Washington, DC, 

401 pp. 

Environment Canada, 2003: Canada’s Greenhouse Gas Inventory, 1990-2003. Available at http://www.ec.gc.ca/pdb/ghg/inventory_report/2003_report/ts_2_e.cfm

Environment Canada, 2005: The Green Lane: Climate Change: 

The Greenhouse Gas Emissions Outlook to 2020. Available at 

http://www.ec.gc.ca/climate/overview_2020-e.html 

GAO (General Accounting Office), 2004: Climate Change: Analysis of Two Studies of Estimated Costs of Implementing the 

Kyoto Protocol. General Accounting Office, Washington, DC, 

20 pp.

Government of Canada, 2005: Project Green: Moving Forward 

on Climate Change. Government of Canada, Ottawa, 48 pp 

Government of Mexico, 2001: Second National Communication. 

Submitted to UNFCCC by the Secretaria de Medio Ambiente y 

Recursos Naturales, Mexico City.

Hoffert, M.I., K. Caldeira, G. Benford, D.R. Criswell, C. Green, 

H. Herzog, A.K. Jain, H.S. Kheshgi, K.S. Lackner, J.S. Lewis, 

H.D. Lightfoot, W. Manheimer, J.C. Mankins, M.E. Mauel, L.J. 

Perkins, M.E. Schlesinger, T. Volk, and T.M.L. Wigley, 2002: 

Advanced technology paths to global climate stability: energy 

for a greenhouse planet. Science, 298(5595), 981-987.

Interlaboratory Working Group, 1997: Scenarios of U.S. Carbon Reductions. Oak Ridge National Laboratory, Oak Ridge, 

TN.

Interlaboratory Working Group, 2000: Scenarios for a Clean 

Energy Future. Oak Ridge National Laboratory, Oak Ridge, 

TN, 371 pp.

IPCC, 2001: Climate Change, 2001: Mitigation. Contribution 

of Working Group III to the Third Assessment Report of the 

Intergovernmental Panel on Climate Change [B. Metz (ed.)]. 

Cambridge University Press, Cambridge, United Kingdom, 

752 pp.

IPCC, 2006: Carbon Dioxide Capture and Storage. IPCC Special 

Report. [B. Metz (ed.)]. Cambridge University Press, Cambridge, United Kingdom, 431 pp.

Lewis, N., 2005: Global Energy Perspective. Paper presented to 

the U.S. DOE Laboratory Energy and Development Working 

Group (LERDWG), Washington, DC. Available at http://nsl.

caltech.edu/energy.html

NAS (National Academy of Sciences), 1992: Policy Implications 

of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. Washington, DC, 127 pp.

NAS (National Academy of Sciences), 1999: Our Common Journey: A Transition Toward Sustainability. National Academy 

Press, Washington, DC, 363 pp.

National Commission on Energy Policy, 2004: Ending the Energy Stalemate: A Bipartisan Strategy to Meet America’s Energy 

Challenges. NCEP, Washington, DC, 148 pp.

National Laboratory Directors, 1997: Technology Opportunities 

to Reduce U.S. Greenhouse Gas Emissions. Prepared for the 

U.S. Department of Energy, 95 pp.

OTA (Office of Technology Assessment), 1991: Changing By Degrees: Steps to Reduce Greenhouse Gases. OTA-0-482, Washington, DC, 354 pp.

Pacala, S. and R. Socolow, 2004: Stabilization wedges: solving 

the climate problem for the next 50 years with current technologies. Science, 305(5686), 968-972.
The U.S. Climate Change Science Program References

212 

Pew Center on Global Climate Change, 2002: Climate Change 

Mitigation in Developing Countries: Brazil, China, Mexico, 

South Africa and Turkey. Report prepared by Chandler W., R. 

Schaffer, Z. Dadi, P.R. Shukla, F. Tudela, O. Davidson, and S. 

Alpan-Atamar, Washington, DC, 64 pp.

Tremblay, A., 2004: Greenhouse Gas Emissions - Fluxes and 

Processes: hydroelectric Reservoirs and Natural Environments. Springer, New York, 732 pp.

U.S. Climate Change Technology Program, 2005: Strategic 

Plan: Draft for Public Comment. Available at http://www.climatetechnology.gov/stratplan/draft/index.htm 

U.S. DOE (U.S. Department of Energy), 2004: National energy 

policy/overview/Canada. In: Energy Trends. Available at http://

energytrends.pnl.gov/Canada/ca004.htm 

Wilbanks, T., 1992: Energy policy responses to concerns about 

global climate change. In: Global Climate Change: Implications, Challenges and Mitigation Measures [Majumdar, S.K., 

L.S. Kalkstein, B. Yamal, E.W. Miller, and L.M. Rosenfeld 

(eds.)]. Pennsylvania Academy of Sciences, Easton, PA, pp. 

452-470.

CHAPTER 7 REFERENCES

CBO (Congressional Budget Office), 2003: The Economic Costs 

of Fuel Economy Standards Versus a Gasoline Tax. Congress 

of the United States, Washington, DC, December, 24 pp.

CIA (Central Intelligence Agency), 2005: The World Factbook. 

Washington, DC. Available at http://www.cia.gov/cia/publications/factbook 

Davis, S.C. and S.W. Diegel, 2004: Transportation Energy Data 

Book: Edition 24. ORNL-6973, Oak Ridge National Laboratory, Oak Ridge, TN.

Environment Canada, 2005a: Canada’s Greenhouse Gas Inventory: 1990-2003. National Inventory Report, Ottawa, Ontario, 

Canada, 339 pp.

Environment Canada, 2005b: Moving Forward on Climate 

Change: A Plan for Honouring our Kyoto Commitment. Ottawa, Canada. Available at http://www.climatechange.gc.ca 

Fulton, L. and G. Eads, 2004: IEA/SMP Model Documentation 

and Reference Case Projection. World Business Council for 

Sustainable Development. Available at http://www.wbcsd.ch/

web/publications/mobility/smp-model-document.pdf, July. 

GAO (U.S. General Accounting Office), 2003: Climate Change, 

Selected Nations’ Reports on Greenhouse Gas Emissions Varied in Their Adherence to Standards. GAO-04-98, Washington, DC, December. Available at http://www.gao.gov/cgi-bin/

getrpt?GAO-04-98. 

General Motors Corporation, Argonne National Laboratory, 

ExxonMobil, and Shell, 2001: Well-to-Wheel Energy Use and 

Greenhouse Gas Emissions of Advanced Fuel/Vehicle Systems: 

North American Analysis. Vol. 2, Argonne National Laboratory, Argonne, IL.

Greene, D.L. and A. Schafer, 2003: Reducing Greenhouse Gas 

Emissions from U.S. Transportation. Pew Center on Global 

Climate Change, Arlington, VA, May, 68 pp.

Greene, D.L., P.D. Patterson, M. Singh, and J. Li, 2005: Feebates, 

rebates and gas-guzzler taxes: a study of incentives for increased fuel economy. Energy Policy, 33(6), 757-776.

Harrington, W. and V. McConnell, 2003: Motor Vehicles and the 

Environment. RFF Report, Resources for the Future, Washington, DC, April, 92 pp.

IEA (International Energy Agency), 2005a: World Energy Outlook 

2005: Middle East and North Africa Insights. OECD, Paris, 

France, 629 pp.

IEA (International Energy Agency), 2005b: Prospects for Hydrogen and Fuel Cells. OECD, Paris, France, 253 pp.

IEA (International Energy Agency), 2004: Biofuels for Transport. 

OECD, Paris, France, 210 pp.

IEA (International Energy Agency), 2001: Saving Oil and Reducing CO2 Emissions in Transport. OECD, Paris, France, 

194 pp.

ILWG (Interlaboratory Working Group), 2000: Scenarios for a 

Clean Energy Future. Prepared by Lawrence Berkeley National Laboratory (LBNL-44029) and Oak Ridge National Laboratory (ORNL/CON-476) for the U.S. Department of Energy, 

371 pp.

INE (Instituto Nacional de Ecología), 2003: Energía. Sector 

Transporte 2000-2001, Inventario Nacional de Emisiones de 

Gases de Efecto Invernadero, INGEI/2000/ENC, Mexico D.F. 

Available at http://www.ine.gob.mx/dgicurg/cclimatico/inventario.html 

Marland, G., T. Boden, and R.J. Andres, 2005: Global CO2 Emissions from Fossil Fuel Burning, Cement Manufacture and Gas 

Flaring, 1751-2002. Available at http://cdiac.esd.ornl.gov/ftp/

ndp030/global.1751_2002.ems, November 8.

Moomaw, W.R. and J.R. Moreira, 2001: Technological and economic potential of greenhouse gas emissions reduction (Chapter 3). In: Climate Change 2001: Mitigation [Metz, Davidson, 

Swart, and Pan (eds.)]. Cambridge University Press, Cambridge, United Kingdom, pp. 167-277.

Nakićenović, N., A. Grűbler, and A. McDonald, 1998: Global 

Energy Perspectives. Cambridge University Press, Cambridge, 

United Kingdom, 299 pp.

NAS (National Academy of Sciences), 2004: The Hydrogen Economy: Opportunities, costs, barriers and research and development needs. National Academies Press, Washington, DC, 

240 pp.

NAS (National Academy of Sciences), 2002: Effectiveness and 

Impact of Corporate Average Fuel Economy (CAFE) Standards. National Academies Press, Washington, DC, 166 pp.

NATS (North American Transportation Statistics), 2005: Various 

Tables. A joint project of the U.S. Bureau of Transportation 

Statistics, Statistics Canada and Instituto Nacional de Estadistica Gegrafica Informatica (INEGI), Mexico. Available at 

http://nats.sct.gob.mx/lib/series 

NCEP (National Commission on Energy Policy), 2004: Ending 

the Energy Stalemate, A Bipartisan Strategy to Meet America’s 

Energy Challenges, Chapter 3, Washington, D.C.: National 
213

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

Commission on Energy Policy, 148 pp. Available at http://

www.energycommission.org

NRCan (Natural Resources Canada), 2006: Comprehensive Energy Use Database Tables. Transportation sector, table 1: 

Secondary energy use by source, table 8: GHG emissions by 

transportation mode. Available at http://oee.nrcan.gc.ca/corporate/statistics/neud/dpa/trends_tran_ca.cfm 

NRTEE (National Round Table on the Environment and the 

Economy), 2005: Economic Instruments for Long-term Reductions in Energy-based Carbon Emissions. Renouf Publishing 

Co., Ltd., Ottawa, Ontario, Canada, 132 pp.

Patterson, P., D. Greene, E. Steiner, S. Plotkin, M. Singh, A. Vyas, 

M. Mintz, D. Santini, S. Folga, J. Moore, P. Reilly-Roe, K. 

Cliffe, R. Talbot, P. Khannna, and V. Stanciulescu, 2003: Joint 

DOE/NRCan Study of North American Transportation Energy 

Futures. Energy Efficiency and Renewable Energy, U.S. Department of Energy, Washington, DC, May. Available at http://

www.eere.energy.gov/ba/pdfs/final_2050_pres.pdf 

Perlack, R.D., L.L. Wright, A.F. Turhollow, R.L. Graham, B.J. 

Stokes, and D.C. Erbach, 2005: Biomass as Feedstock for a 

Bioenergy and Bioproducts Industry: The Technical Feasibility 

of a Billion-Ton Annual Supply. DOE/GO-102995-2135, U.S. 

Department of Energy, Washington, DC.

Rodríguez, H.M., 2005: Perspectivas del Uso de los Hidrocarburos a Nivel México. Presentation, Subsecretario de Hidrocarburos, Mexico City, Mexico, slides online.

SENER (Secretaria de Energia), 2005: Sistema de Información 

Energetica, información estadistica. Available at http://sie.

energia.gob.mx/sie, under Consumo final de energia en el 

sector transporte. 

Turrentine, T. and K. Kurani, 2004: Automotive Fuel Economy in 

the Purchase and Use Decisions of Households. ITS-RR-04-

31, Institute for Transportation Studies, University of California at Davis, Davis, CA, 35 pp.

U.S. DOE (U.S. Department of Energy), 2005: Hydrogen, Fuel 

Cells and Infrastructure Technologies Program: Multi-Year 

Research, Development and Demonstration Plan. DOE/GO102003-1741, Energy Efficiency and Renewable Energy. 

Available at http://www.eere.energy.gov

U.S. DOE/EIA (U.S. Department of Energy, Energy Information 

Administration), 2005a: Annual Energy Review 2004. DOE/

EIA-0384(2004), Washington, DC, August. Available at http://

www.eia.doe.gov 

U.S. DOE/EIA (U.S. Department of Energy, Energy Information 

Administration), 2005b: International Energy Outlook 2005. 

DOE/EIA-0484(2005), Washington, DC, 186 pp.

U.S. DOE/EIA (U.S. Department of Energy, Energy Information 

Administration), 2003: Analysis of S.139, the Climate Stewardship Act of 2003. SR/OIAF/2003-02, Washington, DC, 515 

pp.

U.S. DOT (U.S. Department of Transportation), 1998: Transportation and Global Climate Change: A Review and Analysis of 

the Literature. Federal Highway Administration, Washington, 

DC.

U.S. EPA (U.S. Environmental Protection Agency), 2005: Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2003. 

EPA 430-R-05-003, Environmental Protection Agency, Office 

of Atmospheric Programs, Washington, DC.

Wang, M.Q., 2005: Argonne Expert Addresses Energy and Environmental Impacts of Fuel Ethanol. TransForum, 5(2), 3-4.

Weiss, M.A., J.B. Heywood, E.M. Drake, A. Schafer, and F.F. 

AuYeung, 2000: On the Road in 2020: A life-cycle analysis 

of new automobile technologies. Energy Laboratory Report 

#MIT EL 00-003, Energy Laboratory, Massachusetts Institute 

of Technology, Cambridge, MA.

Williams, R.H., 2005: CO2 Capture and Storage Strategies for 

Coal and Biomass to Reduce GHG Emissions for Synfuels. 

Princeton Environmental Institute, Princeton University, Princeton, NJ, March. Presentation, 154 pp.

WBCSD (World Business Council for Sustainable Development), 

2004: Mobility 2030. The Sustainable Mobility Project, Geneva, Switzerland. Available at http://www.wbcsd.org 

Chapter 8 references

Barlaz, M.A. and R.K. Ham, 1990: The Use of Mass Balances for 

Calculation of the Methane Potential of Fresh and Anaerobically Decomposed Refuse. Proceedings from the GRCDA 13th 

Annual International Landfill Gas Symposium, March 27-29, 

1990,Silver Spring, MD, GRCDA—The Association of Solid 

Waste Management Professionals, 1990, 235 pp.

Barlaz, M., 1994: Measurement of the Methane Potential of the 

Paper, Yard Waste, and Food Waste Components of Municipal 

Solid Waste. Unpublished paper, Department of Civil Engineering, North Carolina State University.

Bogner, J. and K. Spokas, 1993: Landfill CH4: rates, fates, and 

role in the global carbon cycle. Chemosphere, 26(1-4), 

369-386.

Böhringer, C., 1998: The synthesis of bottom-up and top-down in 

energy policy modeling. Energy Economics, 20(3), 233-48.

California Environmental Protection Agency, 2003: Environmental Technologies and Service Opportunities in the Baja 

California Peninsula. International Affairs Unit. 95 pp.

CIEEDAC (Canadian Industrial Energy End-Use Data and Analysis Centre), 2005: Development of Energy Intensity Indicators 

for Canadian Industry: 1990-2004. Simon Fraser University, 

Vancouver, Canada, 166 pp.

DOE, (U.S. Department of Energy), 2006: Accessed on March 

27, 2006, Carbon Sequestration: Research and Development 

Overview. Available at http://www.fossil.energy.gov/programs/

sequestration/overview.html 

Edenhofer, O., C. Carraro, J. Kohler, and M. Grubb, 2006: Endogenous technological change and the economics of atmospheric 

stabilisation. The Energy Journal, special issue, 284 pp.

Edmonds, J., J. Roop, and M. Scott, 2000: Technology and the 

Economics of Climate Change Policy. Prepared for the Pew 

Center on Climate Change by Battelle National Laboratories, 

35 pp. 
The U.S. Climate Change Science Program References

214 

Energy Information Administration, 2005: International Energy Outlook, 2005, 186 pp.

EPA (Environmental Protection Agency), 2003a: International 

Analysis of Methane and Nitrous Oxide Abatement Opportunities: Report to Energy Modeling Forum Working Group 21. 

Environmental Proection Agency, Washington DC, 9 pp.

EPA (Environmental Protection Agency), 2003b: Municipal Solid 

Waste in the United States: 2001 Facts and Figures. Environmental Protection Agency, Office of Solid Waste and Emergency Response, Washington DC, 170 pp.

EPA (Environmental Protection Agency), 2005. Inventory of U.S. 

Greenhouse Gas Emissions and Sinks, 1990-2003. Environmental Protection Agency, Office of Atmospheric Programs, 

Washington DC.

EPIC (Environment and Plastics Industry Council), 2002: Opportunities for Reducing Greenhouse Gas Emissions through Residential Waste Management. Environment and Plastics Industry 

Council, 34 pp.

Grubb, M., J.A. Edmonds, P. ten Brink, and M. Morrison, 1993: 

The cost of limiting fossil fuel CO2 emissions: a survey and 

analysis. Annual Review of Energy and the Environment, 18, 

397-478.

Grubb, M., I. Kohler, and D. Anderson, 2002: Induced technical change in energy and environmental modeling: analytical 

approaches and policy implications. Annual Review of Energy 

and the Environment, 27, 271-308.

Frei, C., P. Haldi, and G. Sarlos, 2003: Dynamic formulation of a 

top-down and bottom-up merging energy policy model. Energy 

Policy, 31(10), 1017-1031.

Hershkowitz, A., 1997: Too Good to Throw Away: Recycling’s 

Proven Record. National Resources Defense Council, New 

York, February 1997, 86 pp.

Herzog, H., 1999: The economics of CO2 capture. In: Greenhouse Gas Control Technologies [Reimer P., B. Eliasson, and 

A. Wokaum (eds.)]. Elsevier Science Ltd., Oxford, pp. 101-

106.

Humphreys, K. and M. Mahasenan, 2002: Toward A Sustainable 

Cement Industry - Substudy 8: Climate Change. World Business Council for Sustainable Development (WBCSD), Geneva, Switzerland.

IEA (International Energy Agency), 2004: Oil crisis and climate 

challenges:30 Years of Energy Use in IEA Countries. International Energy Agency, Paris, France. 211 pp.

IEA (International Energy Agency), 2006: Energy Technology 

Perspectives 2006: Scenarios and Strategies to 2050. International Energy Agency, Paris, France, 484 pp.

IPCC, 2001: Climate Change, 2001: Mitigation. Contribution of 

Working Group III to the Third Assessment Report of the Intergovernmental Panel on Climate Change [B. Metz (ed.)]. Cambridge University Press, Cambridge, United Kingdom, 752 pp

Jaccard, M., J. Nyboer, and B. Sadownik, 2002: The Cost of Climate Policy. University of British Columbia Press, Vancouver, 

British Columbia, Canada, 242 pp.

Jaccard, M., J. Nyboer, C. Bataille, and B. Sadownik, 2003a: 

Modeling the cost of climate policy: distinguishing between 

alternative cost definitions and long-run cost dynamics. The 

Energy Journal, 24(1), 49-73.

Jaccard, M., R. Loulou, A. Kanudia, J. Nyboer, A. Bailie, and 

M. Labriet, 2003b: Methodological contrasts in costing GHG 

abatement policies: optimization and simulation modeling of 

micro-economic effects in Canada. European Journal of Operations Research, 145(1), 148-164.

Jacobsen, H., 1998: Integrating the bottom-up and top-down approach to energy-economy modeling: the case of Denmark. 

Energy Economics, 20(4), 443-461.

Jaffe, A., R. Newell, and R. Stavins, 2002: Environmental policy 

and technological change. Environmental and Resource Economics, 22(1-2), 41-69.

Keith, D.W., and M. Ha-Duong, 2003: CO2 Capture From the Air: 

Technology Assessment and Implications for Climate Policy. 

Proceedings of the 6th Greenhouse Gas Control Conference, 

Kyoto, Japan [J. Gale and Y. Kaya (eds.)]. Permagon Press, 

Oxford, United Kingdom, pp. 187-197.

Kim, Y. and E. Worrell, 2002: International comparison of CO2

emissions trends in the iron and steel industry. Energy Policy, 

30(10), 827-838.

Koopmans, C.C. and D.W. te Velde, 2001: Bridging the energy 

efficiency gap: using bottom-up information in a top-down energy demand model. Energy Economics, 23(1), 57-75.

Löschel, A., 2002: Technological change in economic models of 

environmental policy: a survey. Ecological Economics, 43(2-

3), 105-126.

Martin, N., E. Worrell, M. Ruth, L. Price, R.N. Elliott, A.M. 

Shipley, and J. Thorne, 2001: Emerging Energy-Efficient Industrial Technologies: New York State Edition. LBNL Report 

Number 46990, American Council for an Energy-Efficient 

Economy (ACEEE), 195 pp.

Matysek, A., M. Ford, G. Jakeman, A. Gurney, K. Low, and B.S. 

Fisher, 2006: Technology: It’s role in economic development 

and climate change. ABARE Research Report 06.6, Canberra, Australia.

McFarland, J., J. Reilly, and H. Herzog, 2004: Representing energy technologies in top-down economic models using bottomup information. Energy Economics, 26(4), 685-707.

McKitrick, R., 1996: The Economic Consequences of Taxing 

Carbon Emissions in Canada. Department of Economics, University of British Columbia.

Mohareb, A.K., M. Warith, and R.M. Narbaitz, 2004: Strategies 

for the municipal solid waste sector to assist Canada in meeting its Kyoto Protocol commitments. Environmental Review, 

12(2), 71-95.

Morris, S., G. Goldstein, and V. Fthenakis, 2002: NEMS and 

MARKAL-MACRO models for energy-environmental-economic analysis: a comparison of the electricity and carbon reduction projections. Environmental Modeling and Assessment, 

7(3), 207-216.
215

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

Newell, R., A. Jaffe, and R. Stavins, 1999: The induced innovation 

hypothesis and energy-saving technological change. Quarterly 

Journal of Economics, 14(2), 941-975.

Sands, R., 2002: Dynamics of carbon abatement in the second 

generation model. Energy Economics, 26(4), 721-738.

Schäfer, A. and H. Jacoby, 2005: Technology detail in a multi-sector CGE model: transport under climate policy. Energy Economics, 27(1), 1-24.

Statistics Canada, 2004: Human Activity and the Environment. 

Statistics Canada, Cat no.16-201-XIE. Ottawa, Canada, 

100 pp.

Sutherland, R., 2000: “No cost” efforts to reduce carbon emissions in the U.S.: an economic perspective. Energy Journal, 

21(3), 89-112.

Weyant, J., H. Jacoby, J. Edmonds, and R. Richels (eds.), 1999: 

The costs of the Kyoto Protocol - a multi-model evaluation. 

The Energy Journal, special issue. 398 pp.

WRI (World Resources Institute), 2005: Climate Analysis Indicators Tool (CAIT), Version 3.0, Washington, DC. Available at 

http://cait.wri.org

Worrell, E., L.K. Price, and C. Galitsky, 2004: Emerging EnergyEfficient Technologies in Industry: Case Studies of Selected 

Technologies. Environmental Technologies Division, Lawrence 

Berkeley Laboratory, University of California at Berkeley.

CHAPTER 9 References

CEC (California Energy Commission), 2005: California’s Water 

Energy Relationship. Staff Final Report, California Energy 

Commission, Sacramento, CA, 174 pp.

Chaudhari, M., L. Frantzis, T.E. Hoff, 2004: PV Grid Connected 

Market Potential in 2010 under a Cost Breakthrough Scenario. 

1174373. Navigant Consulting Inc. 93 pp.

CONAFOVI (Comisión Nacional de Fomento a la Vivienda), 

2001: Programa Sectoral de Vivienda 2001-2006. 

DeCanio, S., 1993: Barriers within firms to energy-efficient investments. Energy Policy, 21(9), 906-914.

DeCanio, S., 1994: Why do profitable energy-saving investiment 

projects languish? Journal of General Management, 20(1), 

62-71.

DOE/EERE (U.S. Department of Energy, Energy Efficiency and 

Renewable Energy), 2005: 2005 Buildings Energy Data Book. 

Office of Energy Efficiency and Renewable Energy, Washington, DC.

DOE/EERE (U.S. Department of Energy, Energy Efficiency and 

Renewable Energy), 2006: Building America Puts Residential Building Research to Work. Washington, DC. Available at 

http://www.eere.energy.gov/buildings/building_america/ 

DOE/EIA (U.S. Departmenet of Energy and Energy Information 

Administration), 2003: Carbon Coefficients Used in Emissions of Greenhouse Gases in the United States. Washington, 

DC. Available at http://www.eia.doe.gov/oiaf/1605/ggrpt/pdf/

tab6.1.pdf

DOE/EIA (U.S. Department of Energy and Energy Information 

Administration), 2005: Annual Energy Outlook 2005. Energy Information Administration, EIA-0383(2005), Washington, DC, 136 pp.

IEA (International Energy Agency), 2005: CO2 Emissions from 

Fuel Combustion: 1971-2003. International Energy Agency, 

OECD/IEA, Paris, France.

INEGI (Instituto Nacional de Estadística Geografía e Informática), 2005: Censo general de población y vivienda 2005. 

Mexico, D.F., 2005.

Interlaboratory Working Group, 2000: Scenarios for a Clean 

Energy Future. Oak Ridge National Laboratory, Oak Ridge, 

TN, 371 pp.

Kinzey, B.R., S. Kim, J.D. Ryan, 2002: The Federal Buildings Research and Development Program: A Sharp Tool for Climate 

Policy. ACEEE Buildings Summer Study 2002, Pacific Grove. 

11 vols.

NRCan (Natural Resources Canada), 2005a: Residential Sector 

Secondary Energy Use and GHG Emissions by End Use 2005. 

Ottawa, Canada. 

NRCan (Natural Resources Canada), 2005b: Office of Energy Efficiency National Energy Use Database 2005. Ottawa, Canada. 

Available at http://oee.nrcan.gc.ca/corporate/statistics/neud/

dpa/data_e/database_e.cfm

Public Technology Inc. and U.S. Green Building Council, 1996: 

Sustainable Building Technical Manual. Washington D.C.,

Rabl, A., and J.V. Spadaro, 2007: Environmental Impacts and 

Costs of Energy, Chapter 4 in: Handbook of Energy Efficiency and Renewable Energy, [F. Krieth and Y. Goswami (eds)], 

CRC Press, New York. 

SENER México, 2004: Balance Nacional de Energía 2003. Subsecretaría de Paneación Energética y Desarrollo Tecnológico. 

Secretaría de Energía, México D.F., 215 pp.

SENER México, 2005: Secretaria de Energia—Sistema de Información Energética. México D.F. Available at http://sie.energia.

gob.mx/sie/bdiController

USGBC (U.S. Green Building Council), 2005: LEED for New 

Construction—Rating System 2.2. U.S. Green Building Council, LEED (NC) 2.2, Washington, DC, 416 pp.

Wiel, S., and J.E. McMahon, 2005: Energy-Efficiency Labels 

and Standards: A Guidebook for Appliances, Equipment, and 

Lighting, 2nd Edition. Collaborative Labeling and Standards 

Program, Washington, DC, 218 pp.

PART III OVERVIEW REFERENCES

Bradley, B.A., R.A. Houghton, J.F. Mustard, and S.P. Hamburg, 

2006: Invasive grass reduces aboveground carbon stocks in 

shrublands of the Western US. Global Change Biology, 12(10), 

1815-1822.

Caspersen, J.P., S.W. Pacala, J.C. Jenkins, G.C. Hurtt, P.R. Moorcroft, and R.A. Birdsey, 2000: Contributions of land-use history to carbon accumulation in United States forests. Science, 

290(5494), 1148-1151.

Davidson, E.A., and I.A. Janssens, 2006: Temperature sensitivity 

of soil carbon decomposition and feedbacks to climate change. 

Nature, 440(7081), 165-173.
The U.S. Climate Change Science Program References

216 

Friedlingstein, P., P. Cox, R. Betts, L. Bopp, W. von Bloh, V. 

Brovkin, P. Cadule, S. Doney, M. Eby, I. Fung, G. Bala, J. 

John, C. Jones, F. Joos, T. Kato, M. Kawamiya, W. Knorr, K. 

Lindsay, H.D. Matthews, T. Raddatz, P. Rayner, C. Reick, E. 

Roeckner, K.-G. Schnitzler, R. Schnur, K. Strassmann, A.J. 

Weaver, C. Yoshikawa, and N. Zeng, 2006: Climate-carbon 

cycle feedback analysis: results from the C4

MIP model intercomparison. Journal of Climate, 19(14), 3337-3353.

Houghton, R.A., J.L. Hackler, and K.T. Lawrence, 1999: The U.S. 

carbon budget: contributions from land-use change. Science,

285(5427), 574-578.

Hurtt, G.C., S.W. Pacala, P.R. Moorcroft, J. Caspersen, E. Shevliakova, R.A. Houghton, and B. Moore III, 2002: Projecting 

the future of the U.S. carbon sink. Proceedings of the National 

Academy of Sciences, 99(3), 1389-1394.

Jones, C., C. McConnell, K. Coleman, P. Cox, P. Falloon, D. Jenkinson, and D. Powlson, 2005: Global climate change and soil 

carbon stocks; predictions from two contrasting models for the 

turnover of organic carbon in soil. Global Change Biology, 

11(1), 154-166.

Lal, R., 2001: Fate of eroded soil carbon: emission or sequestration. In: Soil Carbon Sequestration and the Greenhouse Effect

[R. Lal (ed.)]. Soil Science Society of America Special Publication, vol. 57; Madison, Wisconsin, pp. 173-181.

Osterkamp, T.E., and V.E. Romanovsky, 1999: Evidence for 

warming and thawing of discontinuous permafrost in Alaska. 

Permafrost and Periglacial Processes, 10(1), 17-37.

Osterkamp, T.E., L. Viereck, Y. Shur, M.T. Jorgenson, C. Racine, 

A. Doyle, and R.D. Boone, 2000: Observations of thermokarst 

and its impact on boreal forests in Alaska, United States. Arctic, Antarctic and Alpine Research, 32(3), 303-315.

Potter, C., P. Tan, V. Kumar, C. Kucharik, S. Klooster, V. Genovese, W. Cohen, and S. Healey, 2005. Recent history of largescale ecosystem disturbances in North America derived from 

the AVHRR satellite record. Ecosystems, 8(7), 808. 

Potter, C., S. Klooster, P. Tan, M. Steinbach, V. Kumar, and V. 

Genovese, 2003: Variability in terrestrial carbon sinks over 

two decades: Part 1—North America. Earth Interactions, 7, 

Paper 12.

Prentice, I.C., G.D. Farquhar, M.J.R. Fasham, M.L. Goulden, 

M. Heimann, V.J. Jaramillo, H.S. Kheshgi, C. Le Quéré, R.J. 

Scholes, and D.W.R. Wallace, 2001: The carbon cycle and 

atmospheric carbon dioxide. In: Climate Change 2001: The 

Scientific Basis. Contribution of Working Group I to the Third 

Assessment Report of the Intergovernmental Panel on Climate 

Change [J. T. Houghton, Y. Ding, D. J. Griggs, M. Noguer, P. J. 

van der Linden, X. Dai, K. Maskell, and C. A. Johnson (eds.)]. 

Cambridge University Press, Cambridge, United Kingdom and 

New York, pp. 183-237.

Schimel, D., J. Melillo, H. Tian, A.D. McGuire, D. Kicklighter, 

T. Kittel, N. Rosenbloom, S. Running, P. Thornton, D. Ojima, 

W. Parton, R. Kelly, M. Sykes, R. Neilson, and B. Rizzo, 2000: 

Contribution of increasing CO2 and climate to carbon storage 

by ecosystems in the United States. Science, 287(5460), 2004-

2006.

Smith, L.C., Y. Sheng, G.M. MacDonald, L.D. Hinzman, 2005a: 

Disappearing Arctic Lakes. Science, 308(5727), 1429.

Smith, S.L., M.M. Burgess, and F.M. Nixon, 2001: Response of 

active layer and permafrost temperatures to warming during 

1998 in the Mackenzie Delta, Northwest Territories and at Canadian Forces Station Alert and Baker Lake, Nunavut. Geological Survey of Canada Current Research, 2001-E5, 8 pp.

Smith, S.V., R.O. Sleezer, W.H. Renwick, and R.W. Buddemeier, 

2005b: Fates of eroded soil organic carbon: Mississippi Basin 

case study. Ecological Applications, 15(6), 1929-1940.

Stallard, R.F., 1998: Terrestrial sedimentation and the carbon cycle: coupling weathering and erosion to carbon burial. Global 

Biogeochemical Cycles, 12(2), 231-257.

Wienert, A., 2006: From forestland to house lot: carbon stock 

changes and greenhouse gas emissions from exurban land development in central New Hampshire. Master’s Thesis, Brown 

University, Providence, Rhode Island. 29 pp.

CHAPTER 10 references

Ågren, G.I. and E. Bosatta, 2002: Reconciling differences in predictions of temperature response of soil organic matter. Soil 

Biology and Biochemistry, 34(1), 129–132.

Agriculture and Agri-Food Canada, 1999: The health of our 

air: toward sustainable agriculture in Canada. In: Publication 

1981/E [Janzen, H.H., R.L. Desjardins, J.M.R. Asselin, and 

B. Grace (eds.)]. Agriculture and Agri-Foods Canada, Ottawa, 

Ontario, Canada, 40 pp.

Antle, J.M., S. Capalbo, S. Mooney, E.T. Elliott, and K. Paustian, 

2001: Economic analysis of agricultural soil carbon sequestration: an integrated assessment approach. Journal of Agricultural and Resource Economics, 26(2), 344–367.

Antle, J.M., S.M. Capalbo, S. Mooney, D.K. Elliott, and K.H. 

Paustian, 2003: Spatial heterogeneity, contract design, and 

the efficiency of carbon sequestration policies for agriculture. 

Journal of Environmental Economics and Management, 46(2), 

231–250.

Bellamy, P.H., P.J. Loveland, R.I. Bradley, R.M. Lark, and G.J.D. 

Kirk, 2005: Carbon losses from all soils across England and 

Wales 1978–2003. Nature, 437(7056), 245–248.

Boadi, D., C. Benchaar, J. Chiquette, and D. Masse, 2004: Mitigation strategies to reduce enteric methane emissions from dairy 

cows: Update review. Canadian Journal of Animal Science, 

84(3), 319–335.

Boehm, M., B. Junkins, R. Desjardins, S.N. Kulshreshtha, and W. 

Lindwall, 2004: Sink potential of Canadian agricultural soils. 

Climatic Change, 65(3), 297–314.

Bradley, B.A., R.A. Houghton, J.F. Mustard, and S.P. Hamburg, 

2006: Invasive grass reduces aboveground carbon stocks in 

shrublands of the Western US. Global Change Biology, 12(10), 

1815–1822.
217

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

Buyanovsky, G.A. and G.H. Wagner, 1998: Carbon cycling in 

cultivated land and its global significance. Global Change Biology, 4(2), 131–141.

CAST (Council for Agricultural Science and Technology), 2004: 

Climate Change and Greenhouse Gas Mitigation: Challenges and Opportunities for Agriculture. [Paustian, K., B.A. 

Babcock, J. Hatvield, C.L. Kling, R. Lal, B.A. McCarl, S. 

McLaughlin, A.R. Mosier, W.M. Post, C.W. Rice, G.P. Robertson, N.J. Rosenberg, C. Rosenzweig, W.H. Schlesinger, and D. 

Zilberman (Task Force Members)]. CAST, Ames, IA, 120 pp.

CISCC (Comité Intersecretarial Sobre Cambio Climático)., 2001: 

Second National Communication of Mexico to the UN Framework Convention on Climate Change. Secretaría de Medio Ambiente y Recursos Naturales: Instituto Nacional de Ecología, 

México, D.F. México 374 pp. Available at http://unfccc.int/resource/docs/natc/mexnc2.pdf

Conant, R.T., S.J. Del Grosso, W.J. Parton, and K. Paustian, 2005: 

Nitrogen pools and fluxes in grassland soils sequestering carbon. Nutrient Cycling in Agroecosystems, 71(3), 239–248.

Conant, R.T. and K. Paustian, 2002: Potential soil carbon sequestration in overgrazed grassland ecosystems. Global Biogeochemical Cycles, 16(4), 1143.

Conant, R.T., K. Paustian, and E.T. Elliott, 2001: Grassland management and conversion into grassland: Effects on soil carbon. 

Ecological Applications, 11(2), 343–355.

Cox, P.M., R.A. Betts, C.D. Jones, S.A. Spall, and I.J. Totterdell, 

2000: Acceleration of global warming due to carbon-cycle 

feedbacks in a coupled climate model. Nature, 408(6809), 

184–187.

Davidson, E.A. and I.L. Ackerman, 1993: Change in soil carbon 

inventories following cultivation of previously untilled soils. 

Biogeochemistry, 20(3), 161–193.

Enquete Commission, 1995: Protecting our Green Earth: How 

to Manage Global Warming Through Environmentally Sound 

Farming and Preservation of the World’s Forests. Economica 

Verlag, Bonn, Germany, 683 pp.

EPA (U.S. Environmental Protection Agency), 2000: Options for 

Reducing Methane Emissions Internationally. USEPA #430-R90-006, EPA, Washington, DC.

EPA (U.S. Environmental Protection Agency), 2005: Greenhouse 

Gas Mitigation Potential in U.S. Forestry and Agriculture. 

USEPA #430-R-05-006, EPA Office of Atmospheric Programs, Washington, DC, 154 pp. Available at http://www.epa.

gov/sequestration/greenhouse_gas.html

EPA (U.S. Environmental Protection Agency), 2006: Inventory of 

U.S. Greenhouse Gas Emissions and Sinks: 1990–2004. USEPA #430-R-06-002, EPA, Washington, DC, 459 pp. Available 

at http://epa.gov/climatechange/emissions/usgginv_archive.

html

Eve, M.D., M. Sperow, K. Paustian, and R.F. Follett, 2002: National-scale estimation of changes in soil carbon stocks on agricultural lands. Environmental Pollution, 116(3), 431–438.

Follett, R.F., J.M. Kimble, and R. Lal, 2001a: The Potential of 

U.S. Grazing Lands to Sequester Carbon and Mitigate the 

Greenhouse Effect. CRC Press, Chelsea, MI, 442 pp.

Follett, R.F., E.G. Pruessner, S. Samson-Liebig, J.M. Kimble, and 

S. Waltman, 2001b: Carbon sequestration under the Conservation Reserve Program in the historical grassland soils of the 

United States of America. In: Soil Management for Enhancing 

Carbon Sequestration [Lal, R. and K. McSweeney (eds.)]. Soil 

Science Society of America, Madison, WI, pp. 1–14.

Friedl, M.A., A.H. Strahler, X. Zhang, and J. Hodges, 2002: The 

MODIS land cover product: multi-attribute mapping of global 

vegetation and land cover properties from time series MODIS 

data. Proceedings of the International Geoscience and Remote 

Sensing Symposium, 4, 3199–3201.

Frye, W.W., 1984: Energy requirements in no-tillage. In: No Tillage Agricultural Principles And Practices [Phillips, R.E. and 

S.H. Phillips (eds.)]. Van Nostrand Reinhold, New York, pp. 

127–151.

Giardina, C.P. and M.G. Ryan, 2000: Evidence that decomposition rates of organic carbon in mineral soil do not vary with 

temperature. Nature, 404(6780), 858–861.

Gregorich, E.G., P. Rochette, A.J. VandenBygaart, and D.A. Angers, 2005: Greenhouse gas contributions of agricultural soils 

and potential mitigation practices in Eastern Canada. Soil & 

Tillage Research, 83(1), 53–72.

Helgason, B. L., H.H. Janzen, M.H. Chantigny, C.F. Drury, B.H. 

Ellert, E.G. Gregorich, R.L. Lemke, E. Pattey, P. Rochette, and 

C. Wagner-Riddle, 2005: Toward improved coefficients for 

predicting direct N2O emissions from soil in Canadian agroecosystems. Nutrient Cycling in Agroecosystems, 72(1), 87–99.

Houghton, R.A. and C.L. Goodale, 2004: Effects of land-use 

change on the carbon balance of terrestrial ecosystems. In: Ecosystems and Land Use Change [DeFries, R.S., G. P. Asner, and 

R.A. Houghton (eds.)]. Geophysical Monograph Series 153, 

American Geophysical Union, Washington DC, pp 85–98.

Houghton, R. A., J.L. Hackler, and K.T. Lawrence, 1999: The 

U.S. carbon budget: contributions from land-use change. Science, 285(5427), 574–578.

IPCC, 2001: Third Assessment Report. Cambridge University 

Press, Cambridge, United Kingdom, 87 pp.

ISRIC (International Soil Reference and Information Centre) 

2002: FAO Soil Database. CD ROM, Rome, Italy.

Jackson, R.B., J.L. Banner, E.G. Jobbagy, W.T. Pockman, and 

D.H. Wall, 2002: Ecosystem carbon loss with woody plant invasion of grasslands. Nature, 418(6898), 623–626.

Jenkinson, D.S., D.E. Adams, and A. Wild, 1991: Model estimates of CO2 emissions from soil in response to global warming. Nature, 351(6324), 304–306.

Johnson, K.A. and D.E. Johnson, 1995: Methane emissions from 

cattle. Journal of Animal Science, 73(8), 2483–2492.

Kätterer, T., M. Reichstein, O. Andren, and A. Lomander, 1998: 

Temperature dependence of organic matter decomposition: 

a critical review using literature data analyzed with different 

models. Biology and Fertility of Soils, 27(3), 258–262.
The U.S. Climate Change Science Program References

218 

Keppler, F., J.T.G. Hamilton, M. Brass, and T. Rockmann, 2006: 

Methane emissions from terrestrial plants under aerobic conditions. Nature, 439(7073), 187–191.

Knorr, W., I.C. Prentice, J.I. House, and E.A. Holland, 2005: 

Long-term sensitivity of soil carbon turnover to warming. Nature, 433(7023), 298–301.

Kulshreshtha, S.N., B. Junkins, and R. Desjardins, 2000: Prioritizing greenhouse gas emission mitigation measures for agriculture. Agricultural Systems, 66(3), 145–166.

Lal, R., 2002: Why carbon sequestration in agricultural soils? In: 

Agricultural Practices and Policies for Carbon Sequestration 

in Soil [Kimble, J., R. Lal, and R.F. Follett (eds.)]. CRC Press, 

Boca Raton, FL, pp. 21–30.

Lal, R., 2004: Carbon emission from farm operations. Environment International, 30(7), 981–990.

Lal, R., R.F. Follett, and J.M. Kimble, 2003: Achieving soil carbon sequestration in the United States: a challenge to policy 

makers. Soil Science, 168, 827–845.

Lal, R., J.M. Kimble, R.F. Follett, and C.V. Cole, 1998: The Potential of U.S. Cropland to Sequester Carbon and Mitigate the 

Greenhouse Effect. Ann Arbor Press, Chelsea, MI, 128 pp.

Lewandrowski, J., M. Peters, C. Jones, R. House, M. Sperow, 

M.D. Eve, and K. Paustian, 2004: Economics of Sequestering 

Carbon in the U.S. Agricultural Sector. Technical Bulletin No. 

TB 1909, Economic Research Service, Washington, DC.

Long, S.P., E.A. Ainsworth, A.D.B. Leakey, J. Nösberger and 

D.R. Ort, 2006: Food for thought: lower-than-expected crop 

yield stimulation with rising CO2 concentrations. Science, 

312(5782), 1918–1921.

Lynch, D.H., R.D.H. Cohen, A. Fredeen, G. Patterson, and R.C. 

Martin, 2005: Management of Canadian prairie region 

grazed grasslands: Soil C sequestration, livestock productivity and profitability. Canadian Journal of Soil Science, 

85(2), 183–192.

Matin, A., P. Collas, D. Blain, C. Ha, C. Liang, L. MacDonald, S. 

McKibbon, C. Palmer, and R. Kerry, 2004: Canada’s Greenhouse Gas Inventory: 1990–2002. Greenhouse Gas Division, 

Environment Canada, 13 pp.

Ministry of the Environment, 2006: National Inventory Report. 

In: Trends in GHG Sources and Sinks in Canada, 1990-2004. 

Greenhouse Gas Division, Environment Canada, 16 pp.. 

McCarl, B.A. and E.K. Schneider, 2001: The Cost of Greenhouse 

Gas Mitigation in U.S. Agriculture and Forestry. Science, 

294(5551), 2481–2482.

Mosier, A., C. Kroeze, C. Nevison, O. Oenema, S. Seitzinger, and 

O. van Cleemput, 1998a: Closing the global N2O budget: nitrous oxide emissions through the agricultural nitrogen cycle 

- OECD/IPCC/IEA phase II development of IPCC guidelines 

for national greenhouse gas inventory methodology. Nutrient 

Cycling in Agroecosystems, 52(2-3), 225–248.

Mosier, A.R., J.M. Duxbury, J.R. Freney, O. Heinemeyer, K. Minami, and D.E. Johnson, 1998b: Mitigating agricultural emissions of methane. Climatic Change, 40(1), 39–80.

Murray, B.C., B.A. McCarl, and H.C. Lee, 2004: Estimating 

leakage from forest carbon sequestration programs. Land Economics, 80(1), 109–124.

Nabuurs, G.-J., N.H. Ravindranath, K. Paustian, A. Freibauer, B. 

Hohenstein, W. Makundi, H. Aalde, A.Y. Abdelgadir, S.A.K. 

Anwar, J. Barton, K. Bickel, S. Bin-Musa, D. Blain, R. Boer, 

K. Byrne, C.C. Cerri, L. Ciccarese, D.-C. Choque, E. Duchemin, L. Dja, J. Ford-Robertson, W. Galinski, J.C. Germon, 

H. Ginzo, M. Gytarsky, L. Heath, D. Loustau, T. Mandouri, J. 

Mindas, K. Pingoud, J. Raison, V. Savchenko, D. Schone, R. 

Sievanen, K. Skog, K.A. Smith, D. Xu, M. Bakker, M. Bernoux, J. Bhatti, R.T. Conant, M.E. Harmon, Y. Hirakawa, T. 

Iehara, M. Ishizuka, E.G. Jobbagy, J. Laine, M. van der Merwe, I.K. Murthy, D. Nowak, S.M. Ogle, P. Sudha, R.J. Scholes, 

and X. Zhang, 2004: LUCF-sector good practice guidance. In: 

IPCC Good Practice Guidance for LULUCF [Penman, J., M. 

Gytarsky, T. Hirishi, T. Krug, and D. Kruger (eds.)]. Institute 

for Global Environmental Strategies, Hayama, Japan.

NAS (National Academy of Sciences), 2001: Climate Change Science: An Analysis of Some Key Questions. NAS, Committee 

on the Science of Climate Change, National Research Council, 

Washington, DC. 29 pp.

Nowak, R.S., D.S. Ellsworth, and S.D. Smith, 2004: Functional 

responses of plants to elevated atmospheric CO2- do photosynthetic and productivity data from FACE experiments support 

early predictions? New Phytologist, 162(2), 253–280.

NRCS (Natural Resources Conservation Service), 2005: Anaerobic Digestion Practice Standards. U.S. Department of Agriculture, Washington, DC.

Ogle, S.M., F.J. Breidt, M.D. Eve, and K. Paustian, 2003: Uncertainty in estimating land use and management impacts on 

soil organic carbon storage for U.S. agricultural lands between 

1982 and 1997. Global Change Biology, 9(11), 1521–1542.

Ogle, S.M., R.T. Conant, and K. Paustian, 2004: Deriving grassland management factors for a carbon accounting method developed by the Intergovernmental Panel on Climate Change. 

Environmental Management, 33(4), 474–484.

Pacala, S.W., G.C. Hurtt, D. Baker, P. Peylin, R.A. Houghton, 

R.A. Birdsey, L. Heath, E.T. Sundquist, R.F. Stallard, P. Ciais, P. Moorcroft, J.P. Caspersen, E. Shevliakova, B. Moore, 

G. Kohlmaier, E. Holland, M. Gloor, M.E. Harmon, S.M. Fan, 

J.L. Sarmiento, C.L. Goodale, D. Schimel, and C.B. Field, 

2001: Consistent land- and atmosphere-based U.S. carbon sink 

estimates. Science, 292(5525), 2316-2320.

Paustian, K., O. Andren, H.H. Janzen, R. Lal, P. Smith, G. Tian, 

H. Tiessen, M. Van Noordwijk, and P.L. Woomer, 1997: Agricultural soils as a sink to mitigate CO2 emissions. Soil Use and 

Management, 13(s4), 230–244.

Paustian, K., J.M. Antle, J. Sheehan, and E.A. Paul, 2006: Agriculture’s Role in Greenhouse Gas Mitigation. Pew Center on 

Global Climate Change, Washington, DC, 76 pp.

Paustian, K., C.V. Cole, D. Sauerbeck, and N. Sampson, 1998: 

CO2 mitigation by agriculture: an overview. Climatic Change, 

40(1), 135–162.
219

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

Peoples, M.B., E.W. Boyer, K.W.T. Goulding, P. Heffer, V.A. Ochwoh, B. Vanlauwe, S. Wood, K. Yagi, and O. van Cleemput, 

2004: Pathways of nitrogen loss and their impacts on human 

health and the environment. In: Agriculture and the Nitrogen 

Cycle [Mosier, A.R., J.K. Syers, and J.R. Freney (eds.)]. Island 

Press, Washington, DC, pp. 53–69.

Pimentel, D., P. Hepperly, J. Hanson, D. Douds, and R. Seidel, 

2005: Environmental, energetic, and economic comparisons of 

organic and conventional farming systems. Bioscience, 55(7), 

573–582.

Post, W.M. and K.C. Kwon, 2000: Soil carbon sequestration and 

land-use change: processes and potential. Global Change Biology, 6(3), 317–327.

Raymond, P.A. and J.J. Cole, 2003: Increase in the export of alkalinity from North America’s largest river. Science, 301, 88–91.

Reilly, J.M. and K.O. Fuglie, 1998: Future yield growth in field 

crops: what evidence exists? Soil Tillage Research, 47, 

275–290.

Robertson, G.P. and P.R. Grace, 2004: Greenhouse gas fluxes in 

tropical and temperate agriculture: the need for a full-cost accounting of global warming potentials. Environment, Development and Sustainability, 6, 51–63.

Robertson, G.P., E.A. Paul, and R.R. Harwood, 2000: Greenhouse 

gases in intensive agriculture: contributions of individual gases 

to the radiative forcing of the atmosphere. Science, 289(5486), 

1922–1925.

Sheinbaum, C. and O. Masera, 2000: Mitigating carbon emissions 

while advancing national development priorities: the case of 

Mexico. Climatic Change, 47(3), 259–282.

Six, J., S.M. Ogle, F.J. Briedt, R.T. Conant, A.R. Mosier, and K. 

Paustian, 2004: The potential to mitigate global warming with 

no-tillage management is only realized when practiced in the 

long term. Global Change Biology, 10(2), 155–160.

Smith, K.A. and F. Conen, 2004: Impacts of land management on 

fluxes of trace greenhouse gases. Soil Use and Management, 

20, 255–263.

Smith, P., K.W. Goulding, K.A. Smith, D.S. Powlson, J.U. Smith, 

P. Falloon, and K. Coleman, 2001: Enhancing the carbon sink 

in European agricultural soils: including trace gas flux estimates of carbon mitigation potential. Nutrient Cycling in Agroecosystems, 60(1-3), 237–252. 

Smith, S.V., R.O. Sleezer, W.H. Renwick, and R.W. Buddemeier, 

2005: Fates of eroded soil organic carbon: Mississippi basin 

case study. Ecological Applications, 15(6), 1929–1940. 

Sobool, D. and S. Kulshreshtha, 2005: Greenhouse Gas Emissions 

from Agriculture and Agri-Food Systems in Canada. Department of Agricultural Economics, University of Saskatchewan, 

Saskatoon, Saskatchewan, Canada, 156 pp.

Sombroek, W.G., F.O. Nachtergaele, and A. Hebel, 1993: 

Amounts, dynamics and sequestering of carbon in tropical and 

subtropical soils. Ambio, 22(7), 417–426.

Sperow, M., M.D. Eve, and K. Paustian, 2003: Potential soil C sequestration on U.S. agricultural soils. Climatic Change, 57(3), 

319–339.

Van Auken, O.W., 2000: Shrub invasions of North American 

semiarid grasslands. Annual Review of Ecology and Systematics, 31, 197–205.

VandenBygaart, A.J., E.G. Gregorich, and D.A. Angers, 2003: 

Influence of agricultural management on soil organic carbon: 

A compendium and assessment of Canadian studies. Canadian 

Journal of Soil Science, 83(4), 363–380.

West, T.O. and G. Marland, 2003: Net carbon flux from agriculture: Carbon emissions, carbon sequestration, crop yield, and 

land-use change. Biogeochemistry, 63(1), 73–83.

West, T.O., G. Marland, A.W. King, W.M. Post, A.K. Jain, and 

K. Andrasko, 2004: Carbon management response curves: estimates of temporal soil carbon dynamics. Environmental Management, 33(4), 507–518.

Yoo, K., R. Amundson, A.M. Heimsath, and W.E. Dietrich, 

2005: Erosion of upland hillslope soil organic carbon: coupling field measurements with a sediment transport model. 

Global Biogeochemical Cycles, 19(3), GB3003, doi:10.1029/

2004GB002271.

CHAPTER 11 REFERENCES

Aber, J., R.P. Neilson, S. McNulty, J.M. Lenihan, D. Bachelet, 

and R.J. Drapek, 2001: Forest processes and global change: 

predicting the effects of individual and multiple stressors. BioScience 51(9), 735-751.

Albrecht, A. and S.T. Kandji, 2003: Carbon sequestration in tropical agroforestry systems. Agriculture, Ecosystems and Environments, 99(1-3), 15-27.

Amiro, B.D., J.B. Todd, B.M. Wotton, K.A. Logan, M.D. Flannigan, B.J. Stocks, J.A. Mason, D.L. Martell and K.G. Hirsch, 

2001: Direct carbon emissions from Canadian forest fires, 

1959-1999. Canadian Journal of Forest Research, 31(3), 

512-525.

Apps, M.J., W.A. Kurz, S.J. Beukema, and J.S. Bhatti, 1999: Carbon budget of the Canadian forest product sector. Environmental Science & Policy, 2(1), 25-41.

Bachelet, D., R.P. Neilson, J.M. Lenihan, and R.J. Drapek, 2001: 

Climate change effects on vegetation distribution and carbon 

budget in the United States. Ecosystems, 4(3), 164-185.

Baldocchi, D.D. and J.S. Amthor, 2001: Canopy photosynthesis: 

history, measurements and models. In: Terrestrial Global Productivity [Roy, J., B. Saugier, and H. Mooney (eds.)]. Academic Press, San Diego, CA, pp. 9-31.

Barford, C.C., S.C. Wofsy, M.L. Goulden, J.W. Munger, E.H. 

Pyle, S.P. Urbanski, L. Hutyra, S.R. Saleska, D. Fitzjarrald, 

and K. Moore, 2001: Factors controlling long- and short-term 

sequestration of atmospheric CO2 in a mid-latitude forest. Science, 294(5547), 1688-1691.

Bechtold, W.A. and P.L. Patterson (eds.), 2005: The Enhanced 

Forest Inventory and Analysis Program - National Sampling 

Design and Estimation Procedures. General Technical Report SRS-80, U.S. Department of Agriculture, Forest Service, 

Southern Research Station, Asheville, NC, 85 pp.
The U.S. Climate Change Science Program References

220 

Birdsey, R.A. and L.S. Heath, 1995: Carbon changes in U.S. forests. In: Productivity Of America’s Forests and Climate Change 

[Joyce, L.A. (ed.)]. General Technical Report RM-GTR-271, 

U.S. Department of Agriculture, Forest Service, Rocky 

Mountain Forest and Range Experiment Station, Fort Collins, 

CO, pp. 56-70.

Birdsey, R.A., R. Alig, and D. Adams, 2000: Mitigation activities in the forest sector to reduce emissions and enhance sinks 

of greenhouse gases. In: The Impact of Climate Change on 

America’s Forests: A Technical Document Supporting the 2000 

USDA Forest Service RPA Assessment [Joyce, L.A. and R.A. 

Birdsey (eds.)]. RMRS-GTR-59, U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fort 

Collins, CO, pp. 112-131.

Birdsey, R.A., 2004: Data gaps for monitoring forest carbon in 

the United States: an inventory perspective. In: Environmental 

Management [Mickler, R.A. (ed.)]. 33(Suppl. 1), S1-S8.

Birdsey, R.A. and G.M. Lewis, 2003: Current and historical 

trends in use, management, and disturbance of U.S. forestlands. In: The Potential of U.S. Forest Soils to Sequester Carbon and Mitigate the Greenhouse Effect [Kimble, J.M., L.S. 

Heath, and R.A. Birdsey (eds.)]. CRC Press LLC, New York, 

pp. 15-33.

Birdsey, R., K. Pregitzer, and A. Lucier, 2006: Forest carbon management in the United States, 1600-2100. Journal of Environmental Quality, 35(4), 1461-1469.

Caldeira, K., M.G. Morgan, D. Baldocchi, P.G. Brewer, C.-T.A. 

Chen, G.-J. Nabuurs, N. Nakicenovic, and G.P. Robertson, 

2004: A portfolio of carbon management options. In: The 

Global Carbon Cycle: Integrating Humans, Climate, and the 

Natural World [Field, C.B. and M.R. Raupach (eds.)]. Island 

Press, Washington, DC, pp. 103-129.

Canadian Forest Service, 2005: State of the Forest Report, 2004-

2005. Canadian Forest Service, Natural Resources Canada, Ottawa, Ontario, Canada. Available at http://www.nrcan-rncan.

gc.ca/cfs-scf/national/what-quoi/sof/latest_e.html 

Caspersen, J.P., S.W. Pacala, J.C. Jenkins, G.C. Hurtt, P.R. Moorcraft, and R.A. Birdsey, 2000: Contributions of land-use history to carbon accumulation in U.S. forests. Science, 290(5494), 

1148-1151.

Chen, J.M., W. Ju, J. Cihlar, D. Price, J. Liu, W. Chen, J. Pan, A. 

Black, and A. Barr, 2003: Spatial distribution of carbon sources 

and sinks in Canada’s forests. Tellus B, 55(2), 622-641.

Dale, V.H., L.A. Joyce, S. McNulty, R.P. Neilson, M.P. Ayres, 

M.D. Flannigan, P.J. Hanson, L.C. Irland, A.E. Lugo, C.J. Peterson, D. Simberloff, F.J. Swanson, B.J. Stocks, and B. Wotton, 2001: Climate change and forest disturbances. Bioscience, 

51(9), 723-734.

De Jong, B.H.J., S. Ochoa-Gaona, M.A. Castillo-Santiago, N. Ramirez-Marcial, and M.A. Cairns, 2000: Carbon fluxes and patterns of land-use/land-cover change in the Selva Lacandona, 

Mexico. Ambio, 29(8), 504-511.

Environment Canada, 2006: National Inventory Report, 1990-

2004: Greenhouse Gas Sources and Sinks in Canada, Environment Canada, Ottawa, Ontario. Available at http://unfccc.

int/national_reports/annex_i_ghg_inventories/national_inventories_submissions/items/3734.php 

EPA (U.S. Environmental Protection Agency), 2005: Greenhouse 

Gas Mitigation Potential in U.S. Forestry and Agriculture. 

EPA, Washington, DC, 154 pp.

Finzi, A.C., D.J.P. Moore, E.H. DeLucia, J. Lichter, K.S. Hofmockel, R.P. Jackson, H.-S. Kim, R. Matamala, H.R. McCarthy, R. Oren, J.S. Pippen, and W.H. Schlesinger, 2006: Progressive nitrogen limitation of ecosystem processes under elevated 

CO2 in a warm-temperate forest. Ecology, 87(1), 15-25.

Flannigan, M.D., K.A. Logan, B.D. Amiro, W.R. Skinner, and 

B.J. Stocks, 2005: Future area burned in Canada. Climatic 

Change, 72(1-2), 1-16.

Foley, J.A. and N. Ramankutty, 2004: A primer on the terrestrial 

carbon cycle: what we don’t know but should. In: The Global 

Carbon Cycle: Integrating Humans, Climate and the Natural 

World. [Field, C.B. and M.R. Raupauch, (eds.)] Island Press, 

Washington DC, pp. 279-294.

FAO (Food and Agriculture Organization), 2001: Global Forest 

Resources Assessment 2000. Main Report. FAO Forestry Paper 

140, Rome, Italy, 481 pp.

Goetz, S.J., A.G. Bunn, G.J. Fiske, and R.A. Houghton, 2005: 

Satellite-observed photosynthetic trends across boreal North 

America associated with climate and fire disturbance. Proceedings of the National Academy of Sciences, 102(38), 13521-

13525.

Goodale, C.L., M.J. Apps, R.A. Birdsey, C.B. Field, L.S. Heath, 

R.A. Houghton, J.C. Jenkins, G.H. Kohlmaier, W. Kurz, S. Liu, 

G.-J. Nabuurs, S. Nilsson, and A.Z. Shvidenko, 2002: Forest 

carbon sinks in the Northern Hemisphere. Ecological Applications, 12(3), 891-899.

Haynes, R.W. (ed.), 2003: An Analysis of the Timber Situation in 

the United States: 1952-2050. General Technical Report PNWGTR-560, U.S. Department of Agriculture, Forest Service, 

Portland, OR, 254 pp.

Heath, L.S. and J.E. Smith, 2004: Criterion 5, indicator 26: total 

forest ecosystem biomass and carbon pool, and if appropriate, 

by forest type, age class and successional change. In: Data Report: A Supplement to the National Report on Sustainable Forests—2003 [Darr, D.R. (coord.)]. FS-766A, U.S. Department of 

Agriculture, Washington, DC, 14 pp. Available at http://www.

fs.fed.us/research/sustain/contents.htm

Heath, L.S. and J. E. Smith, 2000: An assessment of uncertainty 

in forest carbon budget projections. Environmental Science & 

Policy, 3(2-3), 73-82.

Hogg, E.H. and P.Y. Bernier, 2005: Climate change impacts on 

drought-prone forests in western Canada. Forestry Chronicle,

81(5), 675-682.

Houghton, R.A., J.L. Hackler, and K.T. Lawrence, 1999: The 

U.S. carbon budget: contributions from land-use change, Science, 285(5427), 574-578.

Johnson, D.W., R.B. Thomas, K.L. Griffen, and D.T. Tissue, J.T. 

Ball, B.R. Strain, and R.F. Walker, 1998: Effects of carbon di-
221

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

oxide and nitrogen on growth and nitrogen uptake in ponderosa 

and loblolly pine. Journal of Environmental Quality, 27, 414-

425.

Johnston, M. and T. Williamson, 2005: Climate change implications for stand yields and soil expectation values: a northern 

Saskatchewan case study. Forestry Chronicle, 81, 683-690.

Joyce, L., J. Baer, S. McNulty, V. Dale, A. Hansen, L. Irland, R. 

Neilson, and K. Skog, 2001: Potential consequences of climate 

variability and change for the forests of the United States. In: 

Climate Change Impacts in the United States. Report for the 

U.S Global Change Research Program. Cambridge University 

Press, Cambridge, United Kingdom, pp. 489-521.

Karnosky, D.F., D.R. Zak, K.S. Pregitzer, C.S. Awmack, J.G. 

Bockheim, R.E. Dickson, G.R. Hendrey, G.E. Host, J.S. King, 

B.J. Kopper, E.L. Kruger, M.E. Kubiske, R.L. Lindroth, W.J. 

Mattson, E.P. Mcdonald, A. Noormets, E. Oksanen, W.F.J. 

Parsons, K.E. Percy, G.K. Podila, D.E. Riemenschneider, P. 

Sharma, R. Thakur, A. Sôber, J. Sôber, W.S. Jones, S. Anttonen, 

E. Vapaavuori, B. Mankovska, W. Heilman, J.G. Isebrands, 

2003: Tropospheric ozone moderates responses of temperate 

hardwood forests to elevated CO2: a synthesis of molecular to 

ecosystem results from the Aspen FACE project. Functional 

Ecology, 17(3), 289-304.

Körner, C., 2000: Biosphere responses to CO2 enrichment. Ecological Applications, 10(6), 1590-1619.

Körner, C., R. Asshoff, O. Bignucolo, S. Hättenschwiler, S.G. 

Keel, S. Peláez-Riedl, S. Pepin, R.T.W. Siegwolf, and G. Zotz, 

2005: Carbon flux and growth in mature deciduous forest trees 

exposed to elevated CO2. Science, 309(5739), 1360-1362.

Kurz, W.A., M.J. Apps, T.M. Webb, and P.J. McNamee, 1992: 

The Carbon Budget of the Canadian Forest Sector: Phase 1. 

Information Report NOR-X-326, Forestry Canada, Northern 

Forestry Centre, Edmonton, Alberta, Canada, 93pp.

Kurz, W.A., S. Beukema, and M.J. Apps, 1998: Carbon budget 

implications of the transition from natural to managed disturbance regimes in forest landscapes. Mitigation and Adaptation 

Strategies for Global Change, 2(4), 405-421.

Kurz, W.A. and M.J. Apps, 1999: A 70-year retrospective analysis 

of carbon fluxes in the Canadian forest sector. Ecological Applications, 9(2), 526-547.

Kurz, W., M. Apps, E. Banfield, and G. Stinson, 2002: Forest carbon accounting at the operational scale. The Forestry Chronicle, 78, 672-679.

Leenhouts, B., 1998: Assessment of biomass burning in the conterminous United States. Conservation Ecology, 2(1), 1.

Lewandrowski, J., M. Sperow, M. Peters, M. Eve, C. Jones, K. 

Paustian, and R. House, 2004: Economics of Sequestering Carbon in the U.S. Agricultural Sector. Technical Bulletin 1909, 

U.S. Department of Agriculture, Economic Research Service, 

Washington, DC, 61 pp. 

Lichter, J., S.H. Barron, C.E. Bevacqua, A.C. Finzi, K.F. Irving, 

E.A. Stemmler, and W.H. Schlesinger, 2005: Soil carbon sequestration and turnover in a pine forest after six years of atmospheric CO2 enrichment. Ecology, 86(7), 1835-1847. 

Lippke, B., J. Wilson, J. Perez-Garcia, J. Bowyer, and J. Miel, 

2004: CORRIM: Life cycle environmental performance of renewable building materials. Forest Products Journal, 54(6), 

8-19.

Loya, W.M., K.S. Pregitzer, N.J. Karberg, J.S. King, and C.P. 

Giardina, 2003: Reduction of soil carbon formation by tropospheric ozone under increased carbon dioxide levels. Nature, 

425(6959), 705-707. 

Masera, O., M.J. Ordóñez, and R. Dirzo, 1997: Carbon emissions 

from Mexican forests: the current situation and long-term scenarios. Climatic Change, 35(3), 265-295.

Masera, O., A. Delia Cerón, and A. Ordóñez, 2001: Forestry mitigation options for Mexico: finding synergies between national 

sustainable development priorities and global concerns. Mitigation and Adaptation Strategies for Global Change, 6(3-4), 

291-312.

McNulty, S.G., 2002: Hurricane impacts on U.S. forest carbon 

sequestration. Environmental Pollution, 116(Supplement 1), 

S17-S24.

Nair, P.K.R. and V.D. Nair, 2003: Carbon storage in North American agroforestry systems. In: The Potential of U.S. Forest Soils 

to Sequester Carbon and Mitigate the Greenhouse Gas Effect. 

[Kimble, J., L.S. Heath, R.A. Birdsey, and R. Lal (eds.)]. CRC 

Press, Boca Raton, FL, pp. 333-346.

NRCan (Natural Resources Canada), 2005: The State of Canada’s Forests. Canadian Forest Service, NRC, Ottawa, Ontario, 

Canada. Available at http://www.nrcan-rncan.gc.ca/cfs-scf/national/what-quoi/sof/latest_e.html 

Neilson, R.P., I.C. Prentice, B. Smith, T.G.F. Kittel, and D. Viner, 

1998: Simulated changes in vegetation distribution under global warming. In: The Regional Impacts of Climate Change: An 

Assessment of Vulnerability [Watson, R.T., M.C. Zinyowera, 

R.H. Moss, and D.J. Dokken (eds.)]. Cambridge University 

Press, Cambridge, United Kingdom, pp. 439-456.

Nelson, K.C. and B.H.J. de Jong, 2003: Making global initiatives 

local realities: carbon mitigation projects in Chiapas, Mexico. 

Global Environmental Change, 13(1), 19-30.

NFDP (National Forestry Database Program), 2005: Compendium 

of Canadian Forestry Statistics. National Forestry Database 

Program, Canadian Council of Forest Ministers, Ottawa, Ontario, Canada. Available at http://nfdp.ccfm.org/compendium/

index_e.php 

Norby, R.J., E.H. DeLucia, B. Gielen, C. Calfapietra, C.P. Giardina, J.S. King, J. Ledford, H.R. McCarthy, D.J.P. Moore, R. 

Ceulemans, P. De Angelis, A.C. Finzi, D.F. Karnosky, M.E. 

Kubiske, M. Lukac, K.S. Pregitzer, G.E. Scarascia-Mugnozza, 

W.H. Schlesinger, and R. Oren, 2005: Forest response to elevated CO2 is conserved across a broad range of productivity. 

Proceedings of the National Academy of Sciences, 102(50), 

18052-18056.

Nowak, R.S., D.S. Ellsworth, and S.D. Smith, 2004: Functional 

responses of plants to elevated atmospheric CO2- do photosynthetic and productivity data from FACE experiments support 

early predictions? New Phytologist, 162(2), 253-280.
The U.S. Climate Change Science Program References

222 

Ollinger, S.V., J.D. Aber, P.B. Reich, and R.J. Freuder, 2002: Interactive effects of nitrogen deposition, tropospheric ozone, elevated CO2 land use history on the carbon dynamics of northern hardwood forests. Global Change Biology, 8(6), 545-562.

Oren, R., D.S. Ellsworth, K.H. Johnsen, N. Phillips, B.E. Ewers, C. Maier, K.V.R. Schäfer, H. McCarthy, G. Hendrey, S.G. 

McNulty, and G.G. Katul, 2001: Soil fertility limits carbon 

sequestration by forest ecosystems in a CO2-enriched atmosphere. Nature, 411(6836), 469-472.

Osher, L.J., P.A. Matson, and R. Amundson, 2003: Effect of land 

use change on soil carbon in Hawaii. Biogeochemistry, 65(2), 

213-232.

Pacala, S.W., G.C. Hurtt, D. Baker, P. Peylin, R.A. Houghton, 

R.A. Birdsey, L. Heath, E.T. Sundquist, R.F. Stallard, P. Ciais, P. Moorcroft, J.P. Caspersen, E. Shevliakova, B. Moore, 

G. Kohlmaier, E. Holland, M. Gloor, M.E. Harmon, S.M. Fan, 

J.L. Sarmiento, C.L. Goodale, D. Schimel, and C.B. Field, 

2001: Consistent land- and atmosphere-based U.S. carbon sink 

estimates. Science, 292(5525), 2316-2320.

Palacio-Prieto, J.L., G. Bocco, A. Velázquez, J.-F. Mas, F. TakakiTakaki, A. Victoria, L. Luna-González, G. Gómez-Rodríguez, 

J. López-Garcia, M.P. Muñoz, I. Trejo-Vázquez, A.P. Higuera, 

J. Prado-Molina, A. Rodriguez-Aguilar, R. Mayorga-Saucedo, 

and F.G. Medrano, 2000: La condición actual de los recursos 

forestales en México: resultados del Inventario Forestal Nacional 2000. Investigaciones Geográficas, Boletín del Instituto de Geografía, UNAM, 43, 183-203.

Pan, Y., J. Melillo, A.D. McGuire, D. Kicklighter, L.F. Pitelka, 

K.A. Hibbard, L.L. Pierce, S.W. Running, D.S. Ojima, W.J. 

Parton, and D.S. Schimel, 1998: Modeled responses of terrestrial ecosystems to elevated atmospheric CO2: a comparison of 

simulations by the biogeochemistry models of the Vegetation/

Ecosystem Modeling and Analysis Project (VEMAP). Oecologia, 114(4), 389-404.

Parisien, M.-A., V. Kafka, N. Flynn, K.G. Hirsch, J.B. Todd, and 

M.D. Flannigan, 2005: Fire Behavior Potential in Central Saskatchewan Under Predicted Climate Change. PARC Summary 

Document 05-01, PARC (Prairie Adaptation Research Collaborative), Regina, Saskatchewan, Canada, 12 pp.

Potter, C., S.A. Klooster, R. Myneni, V. Genovese, P. Tan, and V. 

Kumar, 2003: Continental scale comparisons of terrestrial carbon sinks estimated from satellite data and ecosystem modeling 1982-98. Global and Planetary Change, 39(3-4), 201-213.

Price, D.T., D.H. Halliwell, M.J. Apps, W.A. Kurz, and S.R. 

Curry, 1997: Comprehensive assessment of carbon stocks and 

fluxes in a Boreal-Cordilleran forest management unit. Canadian Journal of Forest Research, 27(12), 2005-2016.

Price, D.T., D.W. McKenney, P. Papadopol, T. Logan, and M.F. 

Hutchinson, 2004: High Resolution Future Scenario Climate 

Data for North America. Proceedings of the American Meteorological Society 26th Conference on Agricultural and Forest 

Meteorology, Vancouver, British Columbia, Canada, 23-26 

August 2004, 13 pp. 

Price, D.T., C.H. Peng, M.J. Apps, and D.H. Halliwell, 1999: 

Simulating effects of climate change on boreal ecosystem 

carbon pools in central Canada. Journal of Biogeography, 

26(6), 1237-1248.

Proctor, P., L.S. Heath, P.C. Van Deusen, J.H. Gove, and J.E. 

Smith, 2005: COLE: a web-based tool for interfacing with forest inventory data. In: Proceedings of the Fourth Annual Forest Inventory and Analysis Symposium [McRoberts, R.E., G.A. 

Reams, P.C. Van Deusen, W.H. McWilliams, C.J. Cieszewski 

(eds.)]. GTR-NC-252, U.S. Department of Agriculture, Forest 

Service. St. Paul, MN, 258 pp.

Running, S.W., R.R. Nemani, F.A. Heinsch, M.S. Zhao, M. 

Reeves, and H. Hashimoto, 2004: A continuous satellite-derived measure of global terrestrial primary production. Bioscience, 54(6), 547-560.

Schimel, D., J. Melillo, H. Tian, A.D. McGuire, D. Kicklighter, 

T. Kittel, N. Rosenbloom, S. Running, P. Thornton, D. Ojima, 

W. Parton, R. Kelly, M. Sykes, R. Neilson, and B. Rizzo, 2000: 

Contribution of increasing CO2 and climate to carbon storage 

by ecosystems in the United States. Science, 287(5460), 2004-

2006.

Schoene, D. and M. Netto, 2005: The Kyoto Protocol: what does it 

mean for forests and forestry? Unasylva, 222(56), 3-11.

Secretaría de Medio Ambiente, Recursos Naturales y Pesca 

(SEMARNAP), 1996: Programa Forestal y de Suelo 1995-

2000. Poder ejecutivo Federal, SEMARNAP, México City, 

79 pp.

Skog, K.E. and G.A. Nicholson, 1998: Carbon cycling through 

wood products: the role of wood and paper products in carbon 

sequestration. Forest Products Journal, 48(7), 75-83. Available 

at http://www.fpl.fs.fed.us/documnts/pdf1998/skog98a.pdf

Smith, W.B., P.D. Miles, J.S. Vissage, and S.A. Pugh, 2004: Forest Resources of the United States, 2002. General Technical 

Report NC-241, U.S. Department of Agriculture, Forest Service, North Central Research Station, St. Paul, MN, 137 pp.

Smith, J.E. and L.S. Heath, 2005: Land use change and forestry 

and related sections. In: Inventory of U.S. Greenhouse Gas 

Emissions and Sinks: 1990-2003. Excerpted, EPA 430-R05-003, U.S. Environmental Protection Agency. Available at 

http://yosemite.epa.gov/oar/globalwarming.nsf/content/ResourceCenterPublicationsGHGEmissions.html

Smith, J.E. and L.S. Heath, 2000: Considerations for interpreting probabilistic estimates of uncertainty of forest carbon. In: 

The Impact of Climate Change on America’s Forests [Joyce, 

L.A. and R. Birdsey (eds.)]. General Technical Report RMRSGTR-59, U.S. Department of Agriculture, Forest Service, pp. 

102-111.

Smith, J.E., L.S. Heath, K.E. Skog, and R.A. Birdsey, 2006: Methods for Calculating Forest Ecosystem and Harvested Carbon 

with Standard Estimates for Forest Types of the United States. 

General Technical Report NE-343 U.S. Department of Agriculture, Forest Service, Newtown Square, PA. 216 pp.

Soto-Pinto, L., G. Jimenez-Ferrer, A.V. Guillen, B. de Jong Bergsma, and E. Esquivel-Bazan, 2001: Experiencia agroforestral 
223

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

para la captura de carbono en comunidades indigenas de Mexico. Revista Forestal Iberoamericana, 1, 44-50.

Stavins, R.N. and K.R. Richards, 2005: The Cost of U.S. ForestBased Carbon Sequestration. The Pew Center on Global Climate Change, Arlington, VA, 40 pp. Available at http://www.

pewclimate.org 

Torres, R.J.M., 2004: Estudio de tendencias y perspectivas del 

sector forestal en América Latina al año 2020. Informe Nacional México, FAO. Available at http://www.fao.org/documents/

show_cdr.asp?url_file=/docrep/006/j2215s/j2215s11.htm 

Totten, M., 1999: Getting it Right: Emerging Markets for Storing Carbon in Forests. World Resources Institute, Washington, 

DC, 49 pp.

Turner, D.P., W.D. Ritts, W.B. Cohen, S.T. Gower, S.W. Running, 

M. Zhao, M.H. Costa, A. Kirschbaum, J. Ham, S. Saleska, and 

D.E. Ahl, 2006: Evaluation of MODIS NPP and GPP products across multiple biomes. Remote Sensing of Environment, 

102(3-4), 282-292.

U.S. Climate Change Science Program, 2003: Strategic Plan for 

the Climate Change Science Program. Washington, DC. Available at http://www.climatescience.gov/Library/stratplan2003/

default.htm 

Van Tuyl, S., B.E. Law, D.P. Turner, and A.I. Gitelman, 2005: 

Variability in net primary production and carbon storage across 

Oregon forests - an assessment integrating data from forest inventories, intensive sites, and remote sensing. Forest Ecology 

and Management, 209(3), 273-291.

VEMAP Members (Melillo, J. M., J. Borchers, J. Chaney, H. 

Fisher, S. Fox, A. Haxeltine, A, Janetos, D.W. Kicklighter, 

T.G.F. Kittel, A.D. McGuire, R. McKeown, R. Neilson, 

R. Nemani, D.S. Ojima, T. Painter, Y. Pan, W.J. Parton, L. 

Pierce, L. Pitelka, C. Prentice, B. Rizzo, N.A. Rosenbloom, S. 

Running, D.S. Schimel, S. Sitch, .S. T.; Smith, I. Woodward, 

(VEMAP Members) 1995: Vegetation/ecosystem modeling 

and analysis project (VEMAP): comparing biogeography and 

biogeochemistry models in a continental-scale study of terrestrial ecosystem responses to climate change and CO2 doubling. 

Global Biogeochemical Cycles, 9(4), 407-437.

Volney, J.A.W. and K. Hirsch, 2005: Disturbing forest disturbances. Forestry Chronicle, 81(5), 662-668.

Weber, M.G. and M.D. Flannigan, 1997: Canadian boreal forest 

ecosystem structure and function in a changing climate: impact 

on fire regimes. Environmental Reviews, 5(3-4), 145-166.

Winrock International, 2005: Ecosystem Services. Date accessed 

unknown. Available at http://www.winrock.org/what/projects.

cfm?BU=9086 

CHAPTER 12 REFERENCES

AMAP (Arctic Monitoring and Assessment Programme), 2004: 

AMAP Assessment 2002: Persistent Organic Pollutants in the 

Arctic. AMAP, Oslo, Norway, 310 pp.

Bailey, R. and C.T. Cushwa, 1981: Ecoregions of North America. 

1:12 million scale map, U.S. Forest Service and U.S. Fish and 

Wildlife Service.

Bockheim, J.G. and C. Tarnocai, 1998: Recognition of cryoturbation for classifying permafrost-affected soils. Geoderma, 81(3-

4), 281-293.

Brown, J., O.J. Ferrians, Jr., J.A. Heginbottom, and E.S. Melnikov, 1997: Circum-Arctic Map of Permafrost and Ground Ice 

Conditions. 1:10 million scale map, International Permafrost 

Association.

Burgess, M.M. and C. Tarnocai, 1997: Peatlands in the discontinuous permafrost zone along the Norman Wells pipeline, 

Canada. In: Proceedings of the International Symposium on 

Physics, Chemistry, and Ecology of Seasonally Frozen Soils 

Fairbanks, Alaska, June 10-12, 1997 [Iskandr, I.K., E.A. 

Wright, J.K. Radke, B.S. Sharratt, P.H. Groenevelt, and L.D. 

Hinzman (eds.)]. Special Report 97-10, U.S. Army Cold Regions Research and Engineering Laboratory, Hanover, NH, pp. 

417-424.

Christensen, T., 1991: Arctic and sub-Arctic soil emissions: possible implications for global climate change. Polar Record, 27, 

205-210.

Cryosol Working Group, 2001: Northern and Mid Latitudes Soil 

Database, Version 1. National Soil Database, Research Branch, 

Agriculture and Agri-Food Canada, Ottawa, Ontario, Canada.

Davidson, E.A. and I.A. Janssens, 2006: Temperature sensitivity 

of soil carbon decomposition and feedbacks to climate change. 

Nature, 440(7081), 165-173.

Driscoll, C.T., J. Holsapple, C.L. Schofield, and R. Munson, 1998: 

The chemistry and transport of mercury in a small wetland in 

the Adirondack region of New York, USA. Biogeochemistry,

40(2/3), 137-146.

Ecoregions Working Group, 1989: Ecoclimatic Regions of Canada, First Approximation. Ecoregions Working Group of the 

Canada Committee on Ecological Land Classification, Ecological Land Classification Series, No. 23, Sustainable Development Branch, Canadian Wildlife Service, Conservation and 

Protection, Environment Canada, Ottawa, Ontario, Canada, 

119 pp.

Gorham, E., 1988: Canada’s peatlands: their importance for the 

global carbon cycle and possible effect of “greenhouse” climate warming. Transactions of the Royal Society of Canada, 

Series V, 3, 21-23.

Hengeveld, H.G., 2000: Projections for Canada’s climate future: a 

discussion of recent simulations with the Canadian Global Climate Model. In: Climate Change Digest. CCD 00-01, Special 

Edition, 27 pp. Last accessed April 6, 2005, Meteorological 

Service of Canada, Environment Canada, Downsview, Ontario, Canada. Available at http://www.msc.ec.gc.ca/saib/climate/

docs/ccd_00-01.pdf 

Jorgenson, M.T., C.H. Racine, J.C. Walters, and T.E. Osterkamp, 

2001: Permafrost degradation and ecological changes associated with a warming climate in central Alaska. Climatic Change, 

48(4), 551-579.

Jorgenson, M.Y. and J. Brown. 2005: Classification of the Alaskan 

Beaufort Sea Coast and estimation of carbon and sediment inputs from coastal erosion. Geo-marine Letters. 25(2-3), 69-80.
The U.S. Climate Change Science Program References

224 

Kettles, I.M. and C. Tarnocai, 1999: Development of a model 

for estimating the sensitivity of Canadian peatlands to climate 

warming. Géographie physique et Quaternaire, 53(3), 323-338.

Kokelj, S.V. and C.R. Burn, 2005: Geochemistry of the active 

layer and near-surface permafrost, Mackenzie delta region, 

Northwest Territories, Canada. Canadian Journal of Earth Sciences, 42(1), 37-48.

Kuhry, G.P., 1994: The role of fire in the development of Sphagnum-dominated peatlands in the western boreal Canada. Journal of Ecology, 82(4), 899-910.

Lacelle, B., C. Tarnocai, S. Waltman, J. Kimble, N. Bliss, B. 

Worstell, F. Orozco-Chavez, and B. Jakobsen, 2000: North 

American Soil Organic Carbon Map. 1:10 million scale map, 

Agriculture and Agri-Food Canada, USDA, USGS, INEGI and 

Institute of Geography, University of Copenhagen.

Liblik, L.K., T.R. Moore, J.L. Bubier, and S.D. Robinson, 1997: 

Methane emissions from wetlands in the zone of discontinuous permafrost: Fort Simpson, Northwest Territories, Canada. 

Global Biogeochemical Cycles, 11(4), 485-494.

Mackay, J.R., 1980: The origin of hummocks, western Arctic 

coast, Canada. Canadian Journal of Earth Sciences, 13(7), 

889-897.

Melillo, J.M., T.V. Callaghan, F.I. Woodward, E. Salati, and S.K. 

Sinha, 1990: Climate change - effects on ecosystems (Chapter 10). In: Climate Change: The IPCC Scientific Assessment

[Houghton, J.T., G.J. Jenkins, and J.J. Ephraums (eds.)]. Cambridge University Press, New York, pp. 283-310.

Michaelson, G.J., C.L. Ping, and J.M. Kimble, 1996: Carbon storage and distribution in tundra soils of Arctic Alaska, U.S.A. 

Arctic and Alpine Research, 28(4), 414-424.

Moore, T.R., 1997: Dissolved organic carbon: sources, sinks, and 

fluxes and role in the soil carbon cycle (Chapter 19). In: Soil 

Processes and the Carbon Cycle [Lal, R., J.M. Kimble, R.F. 

Follett, and B.A. Stewart (eds.)]. Advances in Soil Science, 

CRC Press, Boca Raton, FL, pp. 281-292.

Moore, T.R. and N.T. Roulet, 1995: Methane emissions from Canadian peatlands (Chapter 12). In: Soils and Global Change

[Lal, R., J. Kimble, E. Levine, and B.A. Stewart (eds.)]. CRC 

Lewis Publishers, Boca Raton, FL, pp. 153-164.

National Wetlands Working Group, 1988: Wetlands of Canada. 

Ecological Land Classification Series No. 24, Sustainable Development Branch, Environment Canada, Ottawa, Ontario, and 

Polyscience Publications, Inc., Montreal, Quebec. 452 pp.

Oechel, W. and G.L. Vourlitis, 1994: The effect of climate change 

on land-atmosphere feedbacks in arctic tundra regions. Trends 

in Ecology and Evolution, 9(9), 324-329.

Peterson, R.A. and W.B. Krantz, 2003: A mechanism for differential frost heave and its implications for patterned-ground formation. Journal of Glaciology, 49(164), 69-80.

Ping, C.L., T. Jorgenson, J. Brown, L.D. Guo, and Y. Shur, 2006: 

Coastal erosion across northern Alaska and community action. 

Arctic Forum 2006, Arctic Research Consortium of the U.S. 

(ARCUS), Fairbanks, AK, p 53.

Reader, R.J. and J.M. Stewart, 1972: The relationship between 

net primary production and accumulation for a peatland in 

southeastern Manitoba. Ecology, 53(6), 1024-1037.

Ritchie, J.C., 1987: Postglacial Vegetation of Canada. Cambridge 

University Press, New York, 178 pp.

Robinson, S.D. and T.R. Moore, 1999: Carbon and peat accumulation over the past 1200 years in a landscape with discontinuous permafrost, northwestern Canada. Global Biogeochemical 

Cycles, 13(2), 591-601.

Robinson, S.D. and T.R. Moore, 2000: The influence of permafrost and fire upon carbon accumulation in High Boreal peatlands, Northwest Territories, Canada. Arctic, Antarctic, and 

Alpine Research, 32(2), 155-166.

Robinson, S.D., M.R. Turetsky, I.M. Kettles, and R.K. Wieder, 

2003: Permafrost and peatland carbon sink capacity with increasing latitude. In: Permafrost [Phillips, M., S.M. Springman, and L.U. Arenson (eds.)]. Proceedings of the 8th International Conference on Permafrost, 21-25 July 2003, Zurich, 

Switzerland, 2, 965-970.

Soil Carbon Database Working Group, 1993: Soil Carbon for 

Canadian Soils. Digital database, Centre for Land and Biological Resources Research, Research Branch, Agriculture and 

Agri-Food Canada, Ottawa, Ontario, Canada, 137 pp.

Suchanek, T.H., P.J. Richerson, J.R. Flanders, D.C. Nelson, L.H. 

Mullen, L.L. Brester, and J.C. Becker, 2000: Monitoring interannual variability reveals sources of mercury contamination in 

Clear Lake, CA. Environmental Monitoring and Assessment, 

64(1), 299-310.

Tarnocai, C., 1998: The amount of organic carbon in various soil 

orders and ecological provinces in Canada. In: Soil Processes 

and the Carbon Cycle [Lal, R., J.M. Kimble, R.L.F. Follett, 

and B.A. Stewart (eds.)]. Advances in Soil Science, CRC Press, 

New York, 81-92.

Tarnocai, C., 1999: The effect of climate warming on the carbon 

balance of Cryosols in Canada. In: Cryosols and Cryogenic 

Environments [Tarnocai, C., R. King, and S. Smith (eds.)]. 

Special issue of Permafrost and Periglacial Processes, 10(3), 

251-263.

Tarnocai, C., 2000: Carbon pools in soils of the Arctic, Subarctic and Boreal regions of Canada. In: Global Climate Change 

and Cold Regions Ecosystems [Lal, R., J.M. Kimble, and B.A. 

Stewart (eds.)]. Advances in Soil Science, Lewis Publishers, 

Boca Raton, FL, pp. 91-103.

Tarnocai, C., 2006: The effect of climate change on carbon in 

Canadian peatlands. Global and Planetary Change, 53(3), 

222-232.

Tarnocai, C., I.M. Kettles, and B. Lacelle, 2005: Peatlands of 

Canada Database. Digital database, Agriculture and AgriFood Canada, Research Branch, Ottawa, Ontario, Canada.

Trumbore, S.E. and J.W. Harden, 1997: Accumulation and turnover of carbon in organic and mineral soils of the BOREAS 

(Boreal Ecosystem-Atmosphere Study) northern study area. 

Journal of Geophysical Research, 102(D24), 28817-28830.
225

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

Turetsky, M.R., B.D. Amiro, E. Bosch, and J.S. Bhatti, 2004: 

Historical burn area in western Canadian peatlands and its 

relationship to fire weather indices. Global Biogeochemical 

Cycles, 18, GB4014, doi:10.1029/2004GB002222.

Vandenberghe, J., 1992: Cryoturbations: a sediment structural 

analysis. Permafrost and Periglacial Processes, 4, 121-135.

Van Everdingen, R. (ed.), 1998 revised May 2005: Multi-language Glossary of Permafrost and Related Ground-Ice Terms. 

National Snow and Ice Data Center/World Data Center for 

Glaciology, Boulder, CO, 90 pp., Available at http://nsidc.org/

fgdc/glossary 

Van Vliet-Lanoë, B., 1991: Differential frost heave, load casting 

and convection: converging mechanisms; a discussion of the 

origin of cryoturbations. Permafrost and Periglacial Processes, 2, 123-139.

Vitt, D.H., L.A. Halsey, I.E. Bauer, and C. Campbell, 2000: Spatial 

and temporal trends in carbon storage of peatlands of continental western Canada through the Holocene. Canadian Journal of 

Earth Sciences, 37(5), 683-693.

Walker, D.A., V.E. Romanovsky, W.B. Krantz, C.L. Ping, R.A. 

Peterson, M.K. Raynolds, H.E. Epstein, J.G. Jia, and D.C. 

Wirth, 2002: Biocomplexity of Frost Boil Ecosystem on the 

Arctic Slope, Alaska. ARCUS 14th Annual Meeting and Arctic 

Forum 2002, Arlington, VA. Available at http://siempre.arcus.

org/4DACTION/wi_pos_displayAbstract/5/391 

Zoltai, S.C., C. Tarnocai, and W.W. Pettapiece, 1978: Age of Cryoturbated Organic Material in Earth Hummocks From the Canadian Arctic. Proceedings of the Third International Conference on Perma­frost, Edmonton, Alberta, Canada, pp. 325-331.

Zoltai, S.C., S. Taylor, J.K. Jeglum, G.F. Mills, and J.D. Johnson, 

1988: Wetlands of Boreal Canada. In: Wetlands of Canada. 

Ecological Land Classification Series, No. 24, National Wetlands Working Group, Sustainable Development Branch, Environment Canada, Ottawa, Canada, and Polyscience Publications, Montreal, Quebec, Canada, pp. 97-154.

CHAPTER 13 REFERENCES

Armentano, T.B. and E.S. Menges, 1986: Patterns of change in 

the carbon balance of organic soil-wetlands of the temperate 

zone. Journal of Ecology, 74(3), 755–774.

Aselmann, I. and P.J. Crutzen, 1989: Global distribution of natural 

freshwater wetlands and rice paddies, their net primary productivity, seasonality and possible methane emissions. Journal of 

Atmospheric Chemistry, 8(4), 307–359.

Barker, J.R., G.A. Baumgardner, D.P. Turner, and J.J. Lee, 1996: 

Carbon dynamics of the conservation and wetland reserve 

program. Journal of Soil and Water Conservation, 51(4), 340–

346.

Bartlett, K.B. and R.C. Harriss, 1993: Review and assessment 

of methane emissions from wetlands. Chemosphere, 26(1-4), 

261–320.

Blunier, T., J. Chappellaz, J. Schwander, B. Stauffer, and D. 

Raynaud, 1995: Variations in atmospheric methane concentration during the Holocene epoch. Nature, 374(6517), 46–49.

Bourne, J., 2000: Louisiana’s vanishing wetlands: going, going... 

Science, 289(5486), 1860–1863.

Bridgham, S.D., C.L. Ping, J.L. Richardson, and K. Updegraff, 

2000: Soils of northern peatlands: Histosols and Gelisols. In: 

Wetland Soils: Genesis, Hydrology, Landscapes, and Classification [Richardson, J.L. and M.J. Vepraskas (eds.)]. CRC 

Press, Boca Raton, FL, pp. 343–370.

Bridgham, S.D., K. Updegraff, and J. Pastor, 1998: Carbon, nitrogen, and phosphorus mineralization in northern wetlands. 

Ecology, 79(5), 1545–1561.

Cao, M., K. Gregson, and S. Marshall, 1998: Global methane 

emission from wetlands and its sensitivity to climate change. 

Atmospheric Environment, 32(19), 3293–3299.

Chappellaz, J., T. Bluniert, D. Raynaud, J.M. Barnola, J. 

Schwander, and B. Stauffert, 1993: Synchronous changes in 

atmospheric CH4 and Greenland climate between 40 and 8 kyr 

B.P. Nature, 366(6454), 443–445.

Cleary, J., N.T. Roulet, and T.R. Moore, 2005: Greenhouse gas 

emissions from Canadian peat extraction, 1990–2000: a lifecycle analysis. Ambio, 34(6), 456–461.

Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe, 1979: 

Classification of Wetlands and Deepwater Habitats of the 

United States. FWS/OBS-79/31, Fish and Wildlife Service, 

U.S. Department of the Interior, Washington, DC.

Dahl, T.E., 2000: Status and Trends of Wetlands in the Conterminous United States, 1986 to 1997. U.S. Department of the 

Interior, Fish and Wildlife Service, Washington, DC.

Day Jr., J.W., G.P. Shafer, L.D. Britsch, D.J. Reed, S.R. Hawes, 

and D. Cahoon, 2000: Pattern and process of land loss in the 

Mississippi Delta: a spatial and temporal analysis of wetland 

habitat change. Estuaries, 23(4), 425–438.

Day Jr., J.W., G.P. Shaffer, D.J. Reed, D.R. Cahoon, L.D. Britsch, 

and S.R. Hawes, 2001: Patterns and processes of wetland loss 

in coastal Louisiana are complex: a reply to Turner 2001. estimating the indirect effects of hydrologic change on wetland 

loss: if the earth is curved, then how would we know it? Estuaries, 24(4), 647–651.

Dugan, P. (ed.), 1993: Wetlands in Danger—A World Conservation Atlas. Oxford University Press, New York, 192 pp.

Ehhalt, D., M. Prather, F. Dentener, E. Dlugokencky, E. Holland, 

I. Isaksen, J. Katima, V. Kirchhoff, P. Matson, P. Midgley, and 

M. Wang, 2001: Atmospheric chemistry and greenhouse gases. 

In: Climate Change 2001: The Scientific Basis. Contribution 

of Working Group I to the Third Assessment Report of the 

Intergovernmental Panel on Climate Change [Houghton, J.T., 

Y. Ding, D.J. Griggs, M. Noguer, P.J. van der Linden, X. Dai, 

K. Maskell, and C.A. Johnson (eds.)]. Cambridge University 

Press, Cambridge, United Kingdom, pp. 239–287.

Euliss, N.H., R.A. Gleason, A. Olness, R.L. McDougal, H.R. 

Murkin, R.D. Robarts, R.A. Bourbonniere, and B.G. Warner, 

2006: North American prairie wetlands are important nonforested land-based carbon storage sites. Science of the Total Environment, 361(1-3), 179–188.
The U.S. Climate Change Science Program References

226 

Finlayson, C.M., N.C. Davidson, A.G. Spiers, and N.J. Stevenson, 1999: Global wetland inventory—current status and future 

priorities. Marine Freshwater Research, 50, 717–727.

Fletcher, S.E.M., P.P. Tans, L.M. Bruhwiler, J.B. Miller, and M. 

Heimann, 2004a: CH4 sources estimated from atmospheric 

observations of CH4 and its 13C/12C isotopic ratios: 1. inverse 

modeling of source processes. Global Biogeochemical Cycles, 

18, doi:10.1029/2004GB002223.

Fletcher, S.E.M., P.P. Tans, L.M. Bruhwiler, J.B. Miller, and M. 

Heimann, 2004b: CH4 sources estimated from atmospheric 

observations of CH4 and its 13C/12C isotopic ratios: 2. inverse 

modeling of CH4 fluxes from geographical regions. Global 

Biogeochemical Cycles, 18, doi:10.1029/2004GB002224.

Freeman, C., N. Fenner, N.J. Ostle, H. Kang, D.J. Dowrick, B. 

Reynolds, M.A. Lock, D. Sleep, S. Hughes, and J. Hudson, 

2004: Export of dissolved organic carbon from peatlands under 

elevated carbon dioxide levels. Nature, 430(6996), 195-198.

Frolking, S., N. Roulet, and J. Fuglestvedt, 2006: How northern peatlands influence the earth’s radiative budget: sustained 

methane emission versus sustained carbon sequestration. Journal of Geophysical Research-Biogeosciences, 111, G01008, 

doi:10.1029/2005JG000091.

Frolking, S., N.T. Roulet, T.R. Moore, P.M. Lafleur, J.L. Bubier, 

and P.M. Crill, 2002: Modeling seasonal to annual carbon balance of Mer Bleue Bog, Ontario, Canada. Global Biogeochemical Cycles, 16, doi:10.1029/2001GB001457.

Gauci, V., E. Matthews, N. Dise, B. Walter, D. Koch, G. Granberg, 

and M. Vile, 2004: Sulfur pollution suppression of the wetland 

methane source in the 20th and 21st centuries. Proceedings 

of the National Academy of Sciences, 101(34), 12583–12587, 

doi:10.1073/pnas.0404412101.

Gedney, N., P.M. Cox, and C. Huntingford, 2004: Climate feedbacks from methane emissions. Geophysical Research Letters, 

31, L20503, doi:20510.21029/22004GL020919.

Gorham, E., 1991: Northern peatlands: Role in the carbon cycle 

and probable responses to climatic warming. Ecological Applications, 1(2), 182–195.

Harden, J.W., J.M. Sharpe, W.J. Parton, D.S. Ojima, T.L. Fries, 

T.G. Huntington, and S.M. Dabney, 1999: Dynamic replacement and loss of soil carbon on eroding cropland. Global Biogeochemical Cycles, 13(4), 885-901.

Hines, M.E. and K.N. Duddleston, 2001: Carbon flow to acetate 

and C1 compounds in northern wetlands. Geophysical Research 

Letters, 28(22), 4251–4254.

Hoosbeek, M.R., N. van Breeman, F. Berendse, P. Brosvernier, H. 

Vasander, and B. Wallén, 2001: Limited effect of increased atmospheric CO2 concentration on ombrotrophic bog vegetation. 

New Phytologist, 150(2), 459-463.

Hoosbeek, M.R., M. Lukac, D. van Dam, D.L. Godbold, E.J. 

Velthorst, F.A. Biondi, A. Peressotti, M.F. Cotrufo, P. de Angelis, and G. Scarascia-Mugnozza, 2004: More new carbon in 

the mineral soil of a poplar plantation under Free Air Carbon 

Enrichment (POPFACE): Cause of increased priming effect? 

Global Biogeochemical Cycles, 18, GB1040, doi:10.1029/

2003GB002127.

Joosten, H. and D. Clarke, 2002: Wise Use of Mires and Peatlands 

- Background Principles Including a Framework for DecisionMaking. International Mire Conservation Group and International Peat Society, Saarijärvi, Finland, 253 pp.

Kearney, M.S., A.S. Rogers, J.R.G. Townshend, E. Rizzo, D. 

Stutzer, J.C. Stevenson, and K. Sundborg, 2002: Landsat imagery shows decline of coastal marshes in Chesapeake and Delaware Bays. EOS, 83, 173.

Kearney, M.S. and J.C. Stevenson, 1991: Island land loss and 

marsh vertical accretion rate evidence for historical sea-level 

changes in Chesapeake Bay. Journal of Coastal Research, 7, 

403–415.

Keller, J.K., S.D. Bridgham, C.T. Chapin, and C.M. Iversen, 

2005: Limited effects of six years of fertilization on carbon 

mineralization dynamics in a Minnesota fen. Soil Biology and 

Biochemistry, 37(6), 1197–1204.

Kim, H.Y., M. Lieffering, S. Miura, K. Kobayashi, and M. Okada, 

2001: Growth and nitrogen uptake of CO2-enriched rice under 

field conditions. New Phytologist, 150(2), 223-229.

Lichter, J., S.H. Barron, C.E. Bevacqua, A.C. Finzi, K.F. Irving, 

E.A. Stemmler, and W.H. Schlesinger, 2005: Soil carbon sequestration and turnover in a pine forest after six years of atmospheric CO2 enrichment. Ecology, 86(7), 1835-1847.

Lynch-Stewart, P., I. Kessel-Taylor, and C. Rubec, 1999: Wetlands and Government: Policy and Legislation for Wetland 

Conservation in Canada. Sustaining Wetlands Issue Paper 

No. 1999-1, North American Wetlands Conservation Council 

(Canada), 57 pp.

Maltby, E. and P. Immirzi, 1993: Carbon dynamics in peatlands 

and other wetland soils, regional and global perspectives. Chemosphere, 27(6), 999–1023.

Marsh, A.S., D.P. Rasse, B.G. Drake, and J.P. Megonigal, 2005: 

Effect of elevated CO2 on carbon pools and fluxes in a brackish 

marsh. Estuaries, 28(5), 694-704.

Matthews, E. and I. Fung, 1987: Methane emission from natural 

wetlands: global distribution, area, and environmental characteristics of sources. Global Biogeochemical Cycles, 1, 61–86.

Megonigal, J.P. and W.H. Schlesinger, 1997: Enhanced CH4 emissions from a wetland soil exposed to elevated CO2. Biogeochemistry, 37(1), 77–88.

Megonigal, J.P., C.D. Vann, and A.A. Wolf, 2005: Flooding constraints on tree (Taxodium distichum) and herb growth responses to elevated CO2. Wetlands, 25(2), 430–438.

Mitra, S., R. Wassmann, and P.L.G. Vlek, 2005: An appraisal of 

global wetland area and its organic carbon stock. Current Science, 88(1), 25–35.

Moore, T.R., 1997: Dissolved organic carbon: sources, sinks, and 

fluxes and role in the soil carbon cycle. In: Soil Processes and 

the Carbon Cycle. [Lal, R., J.M. Kimble, R.F. Follett, and 

B.A. Stewart (eds.)]. Lewis Publishers, Boca Raton, FL, pp: 

281-292.
227

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

Moore, T.R. and N.T. Roulet, 1995: Methane emissions from 

Canadian peatlands. In: Soils and Global Change [Lal, R., J. 

Kimble, E. Levine, and B. A. Stewart (eds.)]. Lewis Publishers, 

Boca Raton, FL, pp. 153–164.

Moore, T.R., N.T. Roulet, and J.M. Waddington, 1998: Uncertainty in predicting the effect of climatic change on the carbon cycling of Canadian peatlands. Climatic Change, 40(2), 

229–245.

Moser, M., C. Prentice, and S. Frazier, 1996: A global overview of 

wetland loss and degradation. In: Proceedings of the 6th Meeting of the Conference of the Contracting Parties, Brisbane, 

Australia, Papers, Technical Session B, Vol 10/12B, 19-27 

March 1996, Ramsar Convention Bureau, Gland, Switzerland, 

21-31.

Najjar, R.G., H.A. Walker, P.J. Anderson, E.J. Barron, R.J. Bord, 

J.R. Gibson, V.S. Kennedy, C.G. Knight, J.P. Megonigal, R.E. 

O’Conner, C.D. Polsky, N.P. Psuty, B.A. Richards, L.G. Sorenson, E.M. Steele, and R.S. Swanson, 2000: The potential 

impacts of climate change on the mid-Atlantic coastal region. 

Climate Research, 14(3), 219–233.

NRC (National Research Council), 1995: Wetlands: Characteristics and Boundaries. National Academy Press, Washington, 

DC, 307 pp.

NRC (National Research Council), 2001: Compensating for Wetland Losses Under the Clean Water Act. National Academy 

Press, Washington, DC, 322 pp.

National Wetlands Working Group, 1997: The Canadian Wetland Classification System, Second Edition [Warner, B.G. and 

C.D.A. Rubec (eds.)]. Wetlands Research Centre, University of 

Waterloo, Waterloo, Ontario, Canada, 68 pp.

OECD (Organization for Economic Co-operation and Development), 1996: Guidelines for Aid Agencies for Improved Conservation and Sustainable Use of Tropical and Sub-tropical 

Wetlands. OECD, Paris, France, 69 pp.

Oechel, W.C., S. Cowles, N. Grulke, S.J. Hastings, B. Lawrence, 

T. Prudhomme, G. Riechers, B. Strain, D. Tissue, and G. Vourlitis, 1994: Transient nature of CO2 fertilzation in arctic tundra. 

Nature, 371(6497), 500-502.

Petit, J.R., J. Jouzel, D. Raynaud, N.I. Barkov, J.-M. Barnola, I. 

Basile, M. Bender, J. Chappellaz, M. Davis, G. Delaygue, M. 

Delmotte, V.M. Kotlyakov, M. Legrand, V.Y. Lipenkov, C. Lorius, L. Pepin, C. Ritz, E. Saltzman, and M. Stievenard, 1999: 

Climate and atmospheric history of the past 420,000 years from 

the Vostok ice core, Antarctica. Nature, 399(6735), 429-436.

Ramaswamy, V., O. Boucher, J. Haigh, D. Hauglustaine, J. Haywood, G. Myhre, T. Nakajima, G.Y. Shi, and S. Solomon, 

2001: Radiative forcing of climate change. In: Climate Change 

2001: The Scientific Basis. Contribution of Working Group I to 

the Third Assessment Report of the Intergovernmental Panel 

on Climate Change [Houghton, J.T., Y. Ding, D.J. Griggs, M. 

Noguer, P.J. van der Linden, X. Dai, K. Maskell, and C.A. 

Johnson (eds.)]. Cambridge University Press, Cambridge, 

United Kingdom, pp. 349–416.

Rasse, D.P., G. Peresta, and B.G. Drake, 2005: Seventeen years 

of elevated CO2 exposure in a Chesapeake Bay wetland: sustained but contrasting responses of plant growth and CO2 uptake. Global Change Biology, 11(3), 369-377.

Roulet, N.T., 2000: Peatlands, carbon storage, greenhouse gases, 

and the Kyoto Protocol: prospects and significance for Canada. 

Wetlands, 20(4), 605–615.

Rubec, C., 1996: The status of peatland resources in Canada. In: 

Global Peat Resources [Lappalainen, E. (ed.)]. International 

Peat Society and Geological Survey of Finland, Jyskä, Finland, 

pp. 243–252.

Smith, S.V., W.H. Renwick, R.W. Buddemeier, and C.J. Crossland, 2001: Budgets of soil erosion and deposition for sediments and sedimentary organic carbon across the conterminous 

United States. Global Biogeochemical Cycles, 15(3), 697-707.

Stallard, R.F., 1998: Terrestrial sedimentation and the carbon cycle: coupling weathering and erosion to carbon burial. Global 

Biogeochemical Cycles, 12(2), 231-257.

Strack, M., J.M. Waddington, and E.S. Tuittila, 2004: Effect of 

water table drawdown on northern peatland methane dynamics: implications for climate change. Global Biogeochemical 

Cycles, 18, GB4003, doi:4010.1029/2003GB002209.

Tissue, D.T. and W.C. Oechel, 1987: Response of Eriophorum 

vaginatum to elevated CO2 and temperature in the Alaskan tussock tundra, Ecology, 68(2), 401-410.

Turetsky, M.R., B.D. Amiro, E. Bosch, and J.S. Bhatti, 2004: 

Historical burn area in western Canadian peatlands and its 

relationship to fire weather indices. Global Biogeochemical 

Cycles, 18, GB4014, doi:1029/2004GB002222.

Turner, R.E., 1997: Wetland loss in the Northern Gulf of Mexico: 

multiple working hypotheses. Estuaries, 20(1), 1–13.

Updegraff, K., S.D. Bridgham, J. Pastor, P. Weishampel, and C. 

Harth, 2001: Response of CO2 and CH4 emissions in peatlands 

to warming and water-table manipulation. Ecological Applications, 11(2), 311–326.

Vann, C.D. and J.P. Megonigal, 2003: Elevated CO2 and water 

depth regulation of methane emissions: comparison of woody 

and non-woody wetland plant species. Biogeochemistry, 63(2), 

117–134.

Vile, M.A., S.D. Bridgham, R.K. Wieder, and M. Novák, 2003: 

Atmospheric sulfur deposition alters pathways of gaseous carbon production in peatlands. Global Biogeochemical Cycles, 

17(2), 1058–1064.

Wang, J.S., J.A. Logan, M.B. McElroy, B.N. Duncan, I.A. Megretskaia, and R.M. Yantosca, 2004: A 3-D model analysis of 

the slowdown and interannual variability in the methane growth 

rate from 1988 to 1997. Global Biogeochemical Cycles, 18, 

GB3011, doi:101029/102003GB002180.

Watson, R.T., I.R. Noble, B. Bolin, N.H. Ravindranath, D.J. Verardo, and D.J. Dokken, 2000: IPCC Special Report on Land 

Use, Land-Use Change and Forestry. Cambridge University 

Press, Cambridge, United Kingdom, 377 pp.
The U.S. Climate Change Science Program References

228 

Whiting, G.J. and J.P. Chanton, 1993: Primary production control of methane emissions from wetlands. Nature, 364(6440), 

794–795.

Wylynko, D. (ed.), 1999: Prairie Wetlands and Carbon Sequestration: Assessing Sinks Under the Kyoto Protocol. Institute 

for Sustainable Development, Ducks Unlimited Canada, and 

Wetlands International, Winnipeg, Manitoba, Canada.

Zedler, J.B. and S. Kercher, 2005: Wetland resources: status, 

trends, ecosystem services, and restorability. Annual Review of 

Environmental Resources, 30, 39-74.

Zhuang, Q., J.M. Melillo, D.W. Kicklighter, R.G. Prin, A.D. 

McGuire, P.A. Steudler, B. Felzer, and S. Hu, 2004: Methane 

fluxes between terrestrial ecosystems and the atmosphere at 

northern high latitudes during the past century: a restrospective analysis with a process-based biogeochemistry model. 

Global Biogeochemical Cycles, 18, GB 3010, doi:3010.1029/

2004GB002239.

CHAPTER 14 REFERENCES

Agarwal, C., G.M. Green, J.M. Grove, T.P. Evans, and C.M. Schweik, 2000: A Review and Assessment of Land-Use Change 

Models: Dynamics of Space, Time and Human Choice. CIPEC 

Collaborative Report Series No. 1, Center for the Study of Institutions, Populations, and Environmental Change, Indiana 

University and the USDA Forest Service, 61 pp. 

Akbari, H., 2002: Shade trees reduce building energy use and 

CO2 emissions from power plants. Environmental Pollution, 

116(Supplement 1), S119-S126.

Akbari, H. and S. Konopacki, 2005: Calculating energy-saving 

potentials of heat-island reduction strategies. Energy Policy, 

33(6), 721-756.

Akbari, H., D.M. Kurn, S.E. Bretz, and J.W. Hanford, 1997: Peak 

power and cooling energy savings of shade trees. Energy and 

Buildings, 25(2), 139-148.

Akbari, H. and H. Taha, 1992: The impact of trees and white surfaces on residential heating and cooling energy use in four Canadian cities. Energy, 17(2), 141-149.

Alig, R.J., J.D. Kline, and M. Lichtenstein, 2004: Urbanization on 

the U.S. landscape: Looking ahead in the 21st century. Landscape and Urban Planning, 69(2-3), 219-234.

Alig, R.J., A. Plantinga, S. Ahn, and J.D. Kline, 2003: Land Use 

Changes Involving Forestry for the United States: 1952 to 

1997, With Projections to 2050. General Technical Report 587, 

USDA Forest Service, Pacific Northwest Research Station, 

Portland, OR, 92 pp.

Anderson, W.P., P.S. Kanaroglou, E.J. Miller, 1996: Urban form, 

energy and the environment: a review of issues, evidence and 

policy. Urban Studies, 33(1), 7-35.

Betsill, M.M., 2001: Mitigating climate change in U.S. cities: opportunities and obstacles. Local Environment, 6(4), 393-406.

CEC (Commission for Environmental Cooperation), 2001: The 

North American Mosaic: A State of the Environment Report. 

CEC, Montreal, Canada, 100 pp.

CIESIN (Center for International Earth Science Network), Columbia University, International Food Policy Research Institute (IPFRI), the World Bank, Centro Internacional de Agricultura Tropical (CIAT), 2004: Global Rural-Urban Mapping 

Project (GRUMP): Urban Extents. Last accessed 3 Dec 2005. 

Available at http://sedac.ciesin.columbia.edu/gpw

Cifuentes, L., V.H. Borja-Aburto, N. Gouveia, G. Thurston, and 

D.L. Davis, 2001: Assessing health benefits of urban air pollution reductions associated with climate change mitigation 

(2000-2020): Santiago, Sao Paulo, Mexico City, and New York 

City. Environmental Health Perspectives, 109(4), 419-425.

Decker, E.H., S. Elliot, F.A. Smith, D.R. Blake, and F.S. Rowland, 

2000: Energy and material flow through the urban ecosystem. 

Annual Review of Energy and the Environment, 25, 685-740.

Easterling, W.E., C. Polsky, D.G. Goodin, M.W. Mayfield, W.A. 

Muraco, and B. Yarnal, 2003: Changing places and changing 

emissions: comparing local, state, and United States emissions. 

In: Global Change and Local Places: Estimating, Understanding and Reducing Greenhouse Gases [Association of American 

Geographers Global Change in Local Places Research Group 

(eds.)]. Cambridge University Press, Cambridge, United Kingdom, pp. 143-157.

EPA (U.S. Environmental Protection Agency), 2000: Projecting 

Land-Use Change: A Summary of Models for Assessing the 

Effects of Community Growth and Change on Land-Use Patterns. EPA/600/R-00/098, Washington, DC, 142 pp.

Ewing, R., R. Pendall, and D. Chen, 2003: Measuring sprawl and 

its transportation impacts. Transportation Research Record, 

1831, 175-183.

Folke, C., A. Jansson, J. Larsson, and R. Costanza, 1997: Ecosystem appropriation by cites. Ambio, 26, 167-172.

Golubiewski, N.E., 2006: Urbanization transforms prairie carbon 

pools: effects of landscaping in Colorado’s Front Range. Ecological Applications, 16(2), 555-51.

Gomez-Ibanez, J.A., 1991: A global view of automobile dependence. Journal of the American Planning Association, 57(3), 

376-379.

Gonzalez, G.A., 2005: Urban sprawl, global warming and the limits of ecological modernisation. Environmental Politics, 14(3), 

344-362.

Gordon, P. and H.W. Richardson, 1989: Gasoline consumption 

and cities: a reply. Journal of the American Planning Association, 55, 342-346.

Grimm, N.B., J.M. Grove, S.T.A. Pickett, and C.L. Redman, 

2000: Integrated approaches to long-term studies of urban ecological systems. Bioscience, 50(7), 571-584.

Grimmond, C.S.B, T.S. King, F.D. Cropley, D.J. Nowak, and 

C. Souch, 2002: Local-scale fluxes of carbon dioxide in urban environments: methodological challenges and results from 

Chicago. Environmental Pollution, 116(Supplement 1), S243-

S254.

Grimmond, C.S.B., J.A. Salmond, T.R. Oke, B. Offerle, and 

A. Lemonsu, 2004: Flux and turbulence measurements at a 
229

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

densely built-up site in Marseille: heat, mass (water and carbon 

dioxide), and momentum. Journal of Geophysical ResearchAtmospheres, 109, doi:10.1029/2004JD004936.

Huang, Y.J., H. Akbari, H. Taha, and H. Rosenfeld, 1987: The 

potential of vegetation in reducing summer cooling loads in 

residential buildings. Journal of Climate and Applied Meteorology, 26(9), 1103-1116.

Hunt, J.D., D.S. Kriger, and E.J. Miller, 2005: Current operation urban land-use-transport modeling frameworks: a review. 

Transport Reviews, 25(3), 329-376.

ICLEI (The International Council for Local Environmental Initiatives), 1993: Cities for Climate Protection: An International 

Campaign to Reduce Urban Emissions of Greenhouse Gases.

Last accessed 30 Mar 2006. Available at http://www.iclei.org/

index.php?id=1651 

ICLEI (The International Council for Local Environmental Initiatives), 2000: Best Practices for Climate Protection: A Local 

Government Guide. ICLEI, Berkeley, CA.

Imhoff, M.L., L. Bounoua, R.S. DeFries, W.T. Lawrence, D. 

Stutzer, J.T. Compton, and T. Ricketts, 2004: The consequences of urban land transformations on net primary productivity in 

the United States. Remote Sensing of the Environment, 89(4), 

434-443.

Ironmonger, D.S., C.K. Aitken, and B. Erbas, 1995: Economies 

of scale in energy use in adult-only households. Energy Economics, 17(4), 301-310.

Jaccard, M., L. Failing, and T. Berry, 1997: From equipment to 

infrastructure: community energy management and greenhouse 

gas emission reduction. Energy Policy, 25(13), 1065-1074.

Kaye, J.P., I.C. Burke, A.R. Mosier, and J.P. Guerschman, 2004: 

Methane and nitrous oxide fluxes from urban soils to the atmosphere. Ecological Applications, 14(4), 975-981.

Kaye, J.P., R.L. McCulley, and I.C. Burke, 2005: Carbon fluxes, 

nitrogen cycling, and soil microbial communities in adjacent 

urban, native and agricultural ecosystems. Global Change Biology, 11(4), 575-587.

Kenworthy, J.R. and P.W.G. Newman, 1990: Cities and transport 

energy: lessons from a global survey. Ekistics, 34, 258-268.

Koerner, B. and J Klopatek, 2002: Anthropogenic and natural 

CO2 emission sources in an arid urban environment. Environmental Pollution, 116(Supplement 1), S45-S51.

Kousky, C. and S.H. Schneider, 2003: Global climate policy: will 

cities lead the way? Climate Policy, 3(4), 359-372.

Lin, J.C., C. Gerbig, S.C. Wofsy, A.E. Andrews, B.C. Daube, B.C. 

Grainger, B.B. Stephens, P.S. Bakwin, and D.Y. Hollinger, 

2004: Measuring fluxes of trace gases at regional scales by 

Lagrangian observations: application to the CO2 budget and 

rectification airborne (COBRA study). Journal of Geophysical 

Research-Atmospheres, 109, doi:10.1029/2004JD004754.

Liu, J., G.C. Daily, P.R. Ehrich, G.W. Luck, 2003: Effects of 

household dynamics on resource consumption and biodiversity. Nature, 421(6922), 530-533.

MacKellar, F.L., W. Lutz, C. Prinz, and A. Goujon, 1995: Population, households, and CO2 emissions. Population and Development Review, 21(4), 849-865.

McPherson, E.G., J.R. Simpson, P.F. Peper, S.E. Maco, and Q. 

Xiao, 2005: Municipal forest benefits and costs in five U.S. 

cities. Journal of Forestry, 103(8), 411-416.

Mindali, O., A. Raveh, and I. Saloman, 2004: Urban density and 

energy consumption: a new look at old statistics. Transportation Research Record Part A, 38(2), 143-162.

NAHB (National Association of Home Builders), 2005: Housing 

Facts, Figures and Trends., Washington, DC.

Nemitz, E., K. Hargreaves, A.G. McDonald, J.R. Dorsey, and D. 

Fowler, 2002: Micrometeorological measurements of the urban 

heat budget and CO2 emissions on a city scale. Environmental 

Science and Technology, 36(14), 3139-3146.

Newman, P.W.G., 1999: Sustainability and cities: extending the 

metabolism model. Landscape and Urban Planning, 44(4), 

219-226.

Nowak, D.J. and D.E. Crane, 2002: Carbon storage and sequestration by urban trees in the USA. Environmental Pollution, 

116(3), 381-389.

Nowak, D.J., J.T. Walton, J.F. Dwyer, L.G. Kaya, and S. Myeong, 

2005: The increasing influence of urban environments on U.S. 

forest management. Journal of Forestry, 103(8), 377-382.

Oke, T.R., 1989: The micrometeorology of the urban forest. Philosophical Transactions of the Royal Society of London, Series B, 

324(1223), 335-349.

Pataki, D.E., R.J. Alig, A.S. Fung, N.E. Golubiewski, C.A. Kennedy, E.G. McPherson, D.J. Nowak, R.V. Pouyat, and P. Romero Lankao, 2006a: Urban ecosystems and the North American 

carbon cycle. Global Change Biology 12(11), 2092-2102.

Pataki, D.E., D.R. Bowling, and J.R. Ehleringer, 2003: The seasonal cycle of carbon dioxide and its isotopic composition in an 

urban atmosphere: anthropogenic and biogenic effects. Journal 

of Geophysical Research-Atmospheres, 108(D23), 4735.

Pataki, D.E., D.R. Bowling, J.R. Ehleringer, and J.M. Zobitz, 2006b: High resolution monitoring of urban carbon dioxide sources. Geophysical Research Letters, 33, L03813, 

doi:10.1029/2005GL024822.

Pickett, S.T.A., M.L. Cadenasso, J.M. Grove, C.H. Nilon, R.V. 

Pouyat, W.C. Zipperer, and R. Costanza, 2001: Urban ecological systems: linking terrestrial ecological, physical, and socioeconomic components of metropolitan areas. Annual Review of 

Ecology and Systematics, 32, 127-157.

Pouyat, R., P. Groffman, I. Yesilonis, and L. Hernandez, 2002: 

Soil carbon pools and fluxes in urban ecosystems. Environmental Pollution, 116(Supplement 1), S107-S118.

Pouyat, R.V., I. Yesilonis, and D.J. Nowak, 2006: Carbon storage 

by urban soils in the USA. Journal of Environmental Quality, 

35(4), 1566-1575.

Qian, Y. and R.F. Follet, 2002: Assessing soil carbon sequestration 

in turfgrass systems using long-term soil testing data. Agronomy Journal, 94(4), 930-935.
The U.S. Climate Change Science Program References

230 

Romero Lankao, P., H. Lopez, A. Rosas, G. Gunther, and Z. Correa, 2004: Can Cities Reduce Global Warming? Urban Development and the Carbon Cycle in Latin America. IAI, UAM-X, 

IHDP, GCP, Mexico City, 92 pp. Available at http//www.globalcarbonproject.org/global/pdf/MeetingAgenda.pdf

Sahely, H.R., S. Dudding, and C.A. Kennedy, 2003: Estimating 

the urban metabolism of Canadian cities: Greater Toronto 

Area case study. Canadian Journal of Civil Engineering, 

30(2), 468-483.

Soegaard, H. and L. Moller-Jensen, 2003: Toward a spatial CO2 

budget of metropolitan region based on textural image classification and flux measurements. Remote Sensing of the Environment, 87(2-3), 283-294.

Taha, H., 1997: Urban climates and heat islands: albedo, evapotranspiration, and anthropogenic heat. Energy and Buildings, 

25(2), 99-103.

United Nations, 2002: Demographic Yearbook. Available at http://

unstats.un.org/unsd/demographic/products/dyb/default.htm 

United Nations, 2004: World Urbanization Prospects: The 2003 

Revision. E.04.XIII.6, U.N. Dept. of Economic and Social Affairs, Population Division, New York, 323 pp.

United Nations Habitat, 2003: Global Observatory Database. 

Last accessed 10 Nov 2005. Available at http://www.unchs.

org/programmes/guo

Warren-Rhodes, K. and A. Koenig, 2001: Ecosystem appropriation by Hong Kong and its implications for sustainable development. Ecological Economics, 39(2), 347-359.

West, J.J., P. Osnaya, I. Laguna, J. Martinez, and A. Fernandez, 

2004: Co-control of urban air pollutants and greenhouse gases in Mexico City. Environmental Science and Technology, 

38(13), 3474-3481.

CHAPTER 15 REFERENCES

Bakker, D.C.E., A.J. Watson, and C.S. Law, 2001: Southern 

Ocean iron enrichment promotes inorganic carbon drawdown. 

Deep-Sea Research II, 48(11-12), 2483-2507.

Bates, N.R., 2006: Fluxes and the continental shelf pump of carbon in the Chukchi Sea adjacent to the Arctic Ocean. Journal of Geophysical Research, 111, C10013, doi:10.1029/

2005JC003083.

Battle, M., M.L. Bender, P.P. Tans, J.W.C. White, J.T. Ellis, T. 

Conway, and R.J. Francey, 2000: Global carbon sinks and their 

variability inferred from atmospheric O2 and δ 13C. Science, 

287(5462), 2467-2470.

Bender, M.L., D.T. Ho, M.B. Hendricks, R. Mika, M.O. Bazttle, 

P.P. Tans, T.J. Conway, B. Sturtevant, and N. Cassar, 2005: 

Atmospheric O2/N2 changes, 1993-2002: implications for the 

partitioning of fossil fuel CO2 sequestration. Global Biogeochemical Cycles, 19, GB4017, doi:10.1029/2004GB002410.

Benner, R. and S. Opsahl, 2001: Molecular indicators of the 

sources and transformations of dissolved organic matter in the 

Mississippi River plume. Organic Geochemistry, 32(4), 597-

611.

Boehme, S.E., C.L. Sabine, and C.E. Reimers, 1998: CO2 fluxes 

from a coastal transect: a time-series approach. Marine Chemistry, 63(1-2), 49-67.

Borges, A.V., 2005: Do we have enough pieces of the jigsaw to 

integrate CO2 fluxes in the Coastal Ocean? Estuaries, 28(1), 

3-27.

Borges, A.V., B. Delille, and M. Frankignoulle, 2005: Budgeting sinks and sources of CO2 in the coastal ocean: diversity 

of ecosystems counts. Geophysical Research Letters, 32(14), 

L14601, doi:10.1029/2005GL023053.

Boyd P.W., A.J. Watson, C.S. Law, E.R. Abraham, T. Trull, R. 

Murdoch, D.C.E. Bakker, A.R. Bowie, K.O. Buesseler, H. 

Chang, M. Charette, P. Croot, K. Downing, R. Frew, M. Gall, 

M. Hadfield, J. Hall, M. Harvey, G. Jameson, J. LaRoche, M. 

Liddicoat, R. Ling, M.T. Maldonado, R.M. McKay, S. Nodder, 

S. Pickmere, R. Pridmore, S. Rintoul, K. Safi, P. Sutton, R. 

Strzepek, K. Tanneberger, S. Turner, A. Waite, and J. Zeldis, 

2000: A mesoscale phytoplankton bloom in the polar Southern Ocean stimulated by iron fertilization. Nature, 407(6805), 

695-702.

Brewer, P.G., 2003: Direct injection of carbon dioxide into the 

oceans. In: The Carbon Dioxide Dilemma: Promising Technologies and Policies. National Academies Press, pp. 43-51.

Cai, W.J., 2003: Riverine inorganic carbon flux and rate of biological uptake in the Mississippi River plume. Geophysical 

Research Letters, 30(2), 1032.

Cai, W.-J., Z.A. Wang, and Y.C. Wang, 2003: The role of marshdominated heterotrophic continental margins in transport 

of CO2 between the atmosphere, the land-sea interface and 

the oceans. Geophysical Research Letters, 30(16), 1849, 

doi:10.1029/2003GL017633.

Cai, W.J. and M. Dai, 2004: Comment on enhanced open ocean 

storage of CO2 from shelf sea pumping. Science, 306(5701), 

1477c.

Chavez, F.P., P.G. Strutton, G.E. Friederich, R.A. Feely, G.C. 

Feldman, D.G. Foley, and M.J. McPhaden, 1999: Biological 

and chemical response of the equatorial Pacific Ocean to 1997-

98 El Niño. Science, 286(5447), 2126-2131.

Chavez, F.P., J.T. Pennington, C.G. Castro, J.P. Ryan, R.M. Michisaki, B. Schlining, P. Walz, K.R. Buck, A. McFayden, and 

C.A. Collins, 2002: Biological and chemical consequences of 

the 1997-98 El Niño in central California waters. Progress in 

Oceanography, 54(1-4), 205-232.

Chavez, F.P., J. Ryan, S. Lluch-Cota, and M. Ñiquen C., 2003: 

From anchovies to sardines and back: multidecadal change in 

the Pacific Ocean. Science, 299(5604), 217-221.

Chisholm, S.W., P.G. Falkowski, and J. Cullen, 2001: Discrediting ocean fertilization. Science, 294(5541), 309-310.

Codispoti, L.A. and G.E. Friederich, 1986: Variability in the inorganic carbon system over the southeastern Bering Sea shelf 

during the spring of 1980 and spring-summer 1981. Continental Shelf Research, 5(1), 133-160.

Coale, K.H., K.S. Johnson, F.P. Chavez, K.O. Buesseler, R.T. 

Barber, M.A. Brzezinski, W.P. Cochlan, F.J. Millero, P.G. 
231

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

Falkowski, J.E. Bauer, R.H. Wanninkhof, R.M. Kudela, M.A. 

Altabet, B.E. Hales, T. Takahashi, M.R. Landry, R.R. Bidigare, 

X. Wang, Z. Chase, P.G. Strutton, G.E. Friederich, M.Y. Gorbunov, V. P. Lance, A.K. Hilting, M.R. Hiscock, M. Demarest, 

W.T. Hiscock, K.F. Sullivan, S.J. Tanner, R.M. Gordon, C.N. 

Hunter, V.A. Elrod, S.E. Fitzwater, J.L. Jones, S. Tozzi, M. Koblizek, A.E. Roberts, J. Herndon, J. Brewster, N. Ladizinsky, 

G. Smith, D. Cooper, D. Timothy, S.L. Brown, K.E. Selph, 

C.C. Sheridan, B.S. Twining, and Z.I. Johnson, 2004: Southern 

Ocean iron enrichment experiment: carbon cycling in highand low-Si waters. Science, 304(5669), 408-414.

DeGrandpre, M.D., T.R. Hammar, D.W.R. Wallace, and C.D. 

Wirick, 1997: Simultaneous mooring-based measurements of 

seawater CO2 and O2 off Cape Hatteras, North Carolina. Limnology and Oceanography, 42(1), 21-28.

DeGrandpre, M.D., G.J. Olbu, C.M. Beatty, and T.R. Hammar, 

2002: Air-sea CO2 fluxes on the U.S. Middle Atlantic Bight. 

Deep-Sea Research II, 49(20), 4355-4367.

Doney, S.C., R. Anderson, J. Bishop, K. Caldeira, C. Carlson, 

M.E. Carr, R. Feely, M. Hood, C. Hopkinson, R. Jahnke, D. 

Karl, J. Kleypas, C. Lee, R. Letelier, C. McClain, C. Sabine, J. 

Sarmiento, B. Stephens, and R. Weller, 2004: Ocean Carbon 

and Climate Change (OCCC): An Implementation Strategy 

for U.S. Ocean Carbon Cycle Science. UCAR, Boulder, 

CO, 108 pp.

Ducklow, H.W. and S.L. McCallister, 2004: The biogeochemistry 

of carbon dioxide in the coastal oceans. In: The Sea, Vol. 13 

[Robinson, A.R. and K.H. Brink (eds.)]. John Wiley & Sons, 

New York, pp. 269-315.

Feely, R.A., J. Boutin, C.E. Coasca, Y. Dandonneau, J. Etcheto, 

H. Inoue, M. Ishii, C. LeQuere, D.J. Mackey, M. McPhaden, 

N. Metzl, A. Poisson, and R. Wanninkhof, 2002: Seasonal and 

interannual variability of CO2 in the equatorial Pacific. DeepSea Research II, 49(13-14), 2443-2469.

Feely, R.A., T. Takahashi, R. Wanninkhof, M.J. McPhaden, C.E. 

Cosca, S.C. Sutherland, and M.E. Carr, 2006: Decadal variability of the air-sea CO2 fluxes in the equatorial Pacific Ocean. 

Journal of Geophysical Research, 111, C07S03, doi:10.1029/

2005jc003129.

Friederich, G.E., P.G. Brewer, R. Herlein, and F.P. Chavez, 1995: 

Measurement of sea surface partial pressure of CO2 from a 

moored buoy. Deep-Sea Research I, 42(7), 1175-1186.

Friederich, G., P. Walz, M. Burczynski, and F.P. Chavez, 2002: 

Inorganic carbon in the central California upwelling system 

during the 1997-1999 El Niño -La Niña Event. Progress in 

Oceanography, 54(1-4), 185-204.

Gattuso, J.M., M. Frankignoulle, and R. Wollast, 1998: Carbon 

and carbonate metabolism in coastal aquatic ecosystem. Annual Review of Ecology and Systematics, 29, 405-434.

Gervais, F., U. Riebesell, and M.Y. Gorbunov, 2002: Changes in 

primary productivity and chlorophyll: a in response to iron fertilization in the Southern Polar Frontal Zone. Limnology and 

Oceanography, 47(5), 1324.

Gruber, N. and J.L. Sarmiento, 2002: Large-scale biogeochemical-physical interactions in elemental cycles. In: The Sea, Vol. 

12 [Robinson, A.R., J. McCarthy, and B.J. Rothschild (eds.)]. 

John Wiley & Sons, New York, pp. 337-399.

Hales, B. and T. Takahashi, 2004: High-resolution biogeochemical 

investigation of the Ross Sea, Antarctica, during the AESOPS 

(U. S. JGOFS) Program. Global Biogeochemical Cycles, 18(3), 

GB3006, doi:10.1029/2003GB002165.

Hales, B., T. Takahashi, and L. Bandstra, 2005: Atmospheric CO2

uptake by a coastal upwelling system. Global Biogeochemical 

Cycles, 19, GB1009, doi:10.1029/2004GB002295.

Hare, S.R. and N.J. Mantua, 2000: Empirical evidence for North 

Pacific regime shifts in 1977 and 1989. Progress in Oceanography, 47(1), 103-145.

Hedges, J.I., R.G. Keil, and R. Benner, 1997: What happens to 

terrestrial organic matter in the ocean? Organic Geochemistry, 

27(5-6), 195-212.

Keeling, R.F. and H. Garcia, 2002: The change in oceanic O2 inventory associated with recent global warming. Proceedings of 

the National Academy of Sciences, 99(12), 7848-7853. 

Kleypas, J.A., R.A. Feely, V.J. Fabry, C. Langdon, C.L. Sabine, 

and L.Robbins, 2006: Impacts of ocean acidification on coral 

reefs and other marine calcifiers: A guide for future research. 

Report of a workshop held 18-20, April, 2005, St. Petersburg, 

FL Sponsored by NSF, NOAA and USGS, 88 pp. Available at 

http://www.issue.icar.edu/florida/ 

Körtzinger, A., 2003: A significant CO2 sink in the tropical Atlantic Ocean associated with the Amazon river plume. Geophysical Research Letters, 30, 2287, doi:10.1029/2003GL018841.

Liu, K.K., K. Iseki, and S.-Y. Chao, 2000: Continental margin carbon fluxes. In: The Changing Ocean Carbon Cycle [Hansen, 

R., H.W. Ducklow, and J.G. Field (eds.)]. Cambridge University Press, Cambridge, United Kingdom, pp. 187-239.

Lohrenz, S.E., M.J. Dagg, and T.E. Whitledge, 1999: Nutrients, 

irradiance, and mixing as factors regulating primary production in coastal waters impacted by the Mississippi River plume. 

Continental Shelf Research, 19(9), 1113-1141.

Martin, J.H., 1990: Glacial-interglacial CO2 change: the iron hypothesis. Paleoceanography, 5(1), 1-13.

Millero, F.J., W.T. Hiscock, F. Huang, M. Roche, and J.-Z. Zhang, 

2001: Seasonal variation of the carbonate system in Florida 

Bay. Bulletin of Marine Science, 68(1), 101-123.

Muller-Karger, F.E., R. Varela, R. Thunell, R. Luerssen, C. Hu, 

and J. J. Walsh, 2005. The importance of continental margins 

in the global carbon cycle. Geophysical Research Letters, 32, 

L01602, doi:10.1029/2004GL021346.

Park, P.K., L.I. Gordon, and S. Alvarez-Borrego, 1974: The carbon dioxide system of the Bering Sea. In: Oceanography of the 

Bering Sea [Hood, D.W. (ed.)]. Occasional Publication No. 2, 

Institute of Marine Science, University of Alaska, Fairbanks, 

AK, 623 pp.

Patra, P.K., S. Maksyutov, M. Ishizawa, T. Nakazawa, T. Takahashi, and J. Ukita, 2005: Interannual and decadal changes in 

the sea-air CO2 flux from atmospheric CO2 inverse modeling. 
The U.S. Climate Change Science Program References

232 

Global Biogeochemical Cycles, 19, GB4013, doi:10.1029/

2004GB002257.

Pennington, J.T., C.G. Castro, C.A. Collins, W.W. Evans IV, G.E. 

Friederich, R.P. Michisaki, and F.P. Chavez: A Carbon Budget 

for the Northern and Central California Coastal Upwelling 

System. Continental Margins Task Team, The Synthesis Book, 

Chapter 2.2, California Current System, Springer-Verlag, New 

York (in press), 32 mss. pp.

Quay, P., R. Sommerup, T. Westby, J. Sutsman, and A. McNichol, 

2003: Changes in the 13C/12C of dissolved inorganic carbon in 

the ocean as a tracer of anthropogenic CO2 uptake. Global Biogeochemical Cycles, 17(1), doi:10.1029/2001GB001817.

Sabine, C.L., R.A. Feely, N. Gruber, R.M. Key, K. Lee, J.L. 

Bullister, R. Wanninkhof, C.S. Wong, D.W.R. Wallace, B. 

Tilbrook, F.J. Millero, T.H. Peng, A. Kozyr, T. Ono, and A.F. 

Rios, 2004a: The oceanic sink for anthropogenic CO2. Science, 

305(5682), 367-371.

Sarmiento, J.L. and Gruber, N., 2006: Ocean Biogeochemical Dynamics, Princeton University Press, Princeton, NJ, pp. 503.

Sarmiento, J.L. and E.T. Sundquist, 1992: Revised budget for 

the oceanic uptake of anthropogenic carbon dioxide. Nature, 

356(6370), 589-593.

Sarmiento, J.L., P. Monfray, E. Maier-Reimer, O. Aumont, R.J. 

Murnane, and J.C. Orr, 2000: Sea-air CO2 fluxes and carbon 

transport: a comparison of three ocean general circulation 

models. Global Biogeochemical Cycles, 14(4), 1267-1282.

Simpson, J.J., 1985: Air-sea exchange of carbon dioxide and oxygen induced by phytoplankton: methods and interpretation. 

In: Mapping Strategies in Chemical Oceanography [Zirino, 

A. (ed.)]. American Chemical Society, Washington, DC, pp. 

409-450.

Smith, S.V. and J.T. Hollibaugh, 1993: Coastal metabolism and 

the oceanic organic carbon balance. Review of Geophysics, 

31(1), 75-89.

Takahashi, T., S.C. Sutherland, C. Sweeney, A. Poisson, N. Metzl, 

B. Tillbrook, N. Bates, R. Wanninkhof, R.A. Feely, C. Sabine, 

J. Olafsson, and Y. Nojiri, 2002: Global sea-air CO2 flux based 

on climatological surface ocean pCO2, and seasonal biological and temperature effects. Deep-Sea Research II, 49(9-10), 

1601-1622.

Takahashi, T., S.C. Sutherland, R.A. Feely, and C. Cosca, 2003: 

Decadal variation of the surface water pCO2 in the western and 

central Equatorial Pacific. Science, 302(5646), 852-856.

Thomas, H., Y. Bozec, K. Elkalay, and H.J.W. De Baar, 2004: 

Enhanced open ocean storage of CO2 from shelf sea pumping. 

Science, 304(5673), 1005-1008.

Tsunogai, S., S. Watanabe, and T. Sato, 1999: Is there a “continental shelf pump” for the absorption of atmospheric CO2? Tellus 

B, 5(3), 701-712.

van Geen, A., R.K. Takesue, J. Goddard, T. Takahashi, J.A. Barth, 

and R.L. Smith, 2000: Carbon and nutrient dynamics during 

upwelling off Cape Blanco, Oregon. Deep-Sea Research II, 

49(20), 4369-4385.

Wanninkhof, R., 1992: Relationship between wind speed and gas 

exchange. Journal of Geophysical Research, 97(C5), 7373-

7382.

Ware, D.M. and R.D. Thomson, 2005: Bottom-up ecosystem trophic dynamics determine fish production in the Northeast Pacific. Science, 308(5726), 1280-1284.

APPENDIX A REFERENCES 

Birdsey, R.A. and L.S. Heath, 1995: Carbon changes in U.S. forests. In: Productivity of America’s Forests and Climate Change

[Joyce, L.A. (ed.)]. General Technical Report RM-GTR-271, 

U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station, Fort Collins, CO, 

pp. 56-70.

Birdsey, R.A. and G.M. Lewis, 2003: Current and historical trends 

in use, management, and disturbance of U.S. forestlands. In: 

The Potential of U.S. Forest Soils to Sequester Carbon and 

Mitigate the Greenhouse Effect [Kimble, J.M., L.S. Heath, 

and R. A. Birdsey (eds.)]. CRC Press LLC, New York, pp. 

15-33.

Bradley, B.A., R.A. Houghton, J.F. Mustard, and S.P. Hamburg, 

2006: Invasive grass reduces aboveground carbon stocks in 

shrublands of the Western US. Global Change Biology, 12(10), 

1815-1822.

Cairns, M.A., P.K. Haggerty, R. Alvarez, B.H.J. De Jong, and I. 

Olmsted, 2000: Tropical Mexico’s recent land-use change: a 

region’s contribution to the global carbon cycle. Ecological 

Applications, 10(5), 1426-1441.

Caspersen, J.P., S.W. Pacala, J.C. Jenkins, G.C. Hurtt, P.R. Moorcroft, and R.A. Birdsey, 2000: Contributions of land-use history to carbon accumulation in U.S. forests. Science, 290(5494), 

1148-1151.

Environment Canada, 2005: Canada’s Greenhouse Gas Inventory 1990-2003: Initial Submission. Greenhouse Gas Division, 

Environment Canada, Ottawa, Ontario, Canada. Available at 

http://unfccc.int/national_reports/annex_i_ghg_inventories/

national_inventories_submissions/items/2761.php

Houghton, R.A., J.L. Hackler, and K.T. Lawrence, 1999: The 

U.S. carbon budget: contributions from land-use change. Science, 285(5427), 574-578.

Houghton, R.A. and J.L. Hackler, 2000: Changes in terrestrial carbon storage in the United States. 1. The roles of agriculture and 

forestry. Global Ecology and Biogeography, 9(2), 125-144.

Houghton, R.A., J.L. Hackler, and K.T. Lawrence, 2000: Changes 

in terrestrial carbon storage in the United States. 2. The role of 

fire and fire management. Global Ecology and Biogeography, 

9(2), 145-170.

Hurtt, G.C., S.W. Pacala, P.R. Moorcroft, J. Caspersen, E. Shevliakova, R.A. Houghton, and B. Moore III, 2002: Projecting 

the future of the U.S. carbon sink. Proceedings of the National Academy of Sciences, 99(3), 1389-1394.

Masera, O.R., M.J. Ordonez, and R. Dirzo, 1997: Carbon emissions from Mexican forests: current situation and long-term 

scenarios. Climatic Change, 35(3), 265-295.
233

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

Pacala, S.W., G.C. Hurtt, D. Baker, P. Peylin, R.A. Houghton, 

R.A. Birdsey, L. Heath, E.T. Sundquist, R.F. Stallard, P. Ciais, P. Moorcroft, J.P. Caspersen, E. Shevliakova, B. Moore, 

G. Kohlmaier, E. Holland, M. Gloor, M.E. Harmon, S.M. Fan, 

J.L. Sarmiento, C.L. Goodale, D. Schimel, and C.B. Field, 

2001: Consistent land- and atmosphere-based U.S. carbon sink 

estimates. Science, 292(5525), 2316-2320.

Smith, W.B., P.D. Miles, J.S. Vissage, and S.A. Pugh, 2004: Forest Resources of the United States, 2002. General Technical 

Report NC-241, U.S. Department of Agriculture, Forest Service, St. Paul, MN, 137 pp.

APPENDIX B REFERENCES

Baldocchi, D., E. Falge, L.H. Gu, R. Olson, D. Hollinger, S. Running, P. Anthoni, C. Bernhofer, K. Davis, R. Evans, J. Fuentes, 

A. Goldstein, G. Katul, B. Law, X.H. Lee, Y. Malhi, T. Meyers, W. Munger, W. Oechel, K.T. Paw U, K. Pilegaard, H.P. 

Schmid, R. Valentini, S. Verma, T. Vesala, K. Wilson, and S. 

Wofsy, 2001: FLUXNET: a new tool to study the temporal and 

spatial variability of ecosystem-scale carbon dioxide, water vapor, and energy flux densities, Bulletin of the American Meteorological Society, 82(11), 2415-2434.

Barford, C.C., S.C. Wofsy, M.L. Goulden, J.W. Munger, E.H. 

Pyle, S.P. Urbanski, L. Hutyra, S.R. Saleska, D. Fitzjarrald, 

and K. Moore, 2001: Factors controlling long- and short-term 

sequestration of atmospheric CO2 in a mid-latitude forest. Science, 294(5547), 1688-1691.

Canadell, J.G., H.A. Mooney, D.D. Baldocchi, J.A. Berry, J.R. 

Ehleringer, C.B. Field, S.T. Gower, D.Y. Hollinger, J.E. Hunt, 

R.B. Jackson, S.W. Running, G.R. Shaver, W. Steffen, S.E. 

Trumbore, R. Valentini, B.Y. Bond, 2000: Carbon metabolism 

of the terrestrial biosphere: a multitechnique approach for improved understanding. Ecosystems, 3(2), 115-130.

Cook, B.D., K.J. Davis, W. Wang, A. Desai, B.W. Berger, R.M. 

Teclaw, J.G. Martin, P.V. Bolstad, P.S. Bakwin, C. Yi, and W. 

Heilman, 2004: Carbon exchange and venting anomalies in an 

upland deciduous forest in northern Wisconsin, USA. Agricultural and Forest Meteorology, 126(3-4), 271-295.

Curtis, P.S., P.J. Hanson, P. Bolstad, C. Barford, J.C. Randolph, 

H.P. Schmid, and K.B. Wilson, 2002: Biometric and eddy-covariance based estimates of annual carbon storage in five eastern North American deciduous forests. Agricultural and Forest 

Meteorology, 113(1-4), 3-19.

Ehman, J.L., H.P. Schmid, C.S.B. Grimmond, J.C. Randolph, P.J. 

Hanson, C.A. Wayson, and F.D. Cropley, 2002: An initial intercomparison of micrometerological and ecological inventory 

estimates of carbon exchange in a mid-latitude deciduous forest. Global Change Biology, 8(6), 575-589.

Gough, C.M., P.S. Curtis, J.G. Vogel, H.P. Schmid, and H.B. Su: 

Annual carbon storage from 1999 to 2003 in a Northern hardwood forest assessed using eddy-covariance and biometric 

methods. Agricultural and Forest Meteorology (in review).

Horst, T.W. and J.C. Weil, 1994: How far is far enough? The fetch 

requirements for micrometeorological measurement of surface 

fluxes. Journal of Atmospheric and Oceanic Technology, 11(4), 

1018-1025.

Law, B.E., P.E. Thornton, J. Irvine, P.M. Anthoni, and S. Van 

Tuyl, 2001: Carbon storage and fluxes in ponderosa pine forests at different developmental stages. Global Change Biology, 

7(7), 755-777.

Verma, S.B., A. Dobermann, K.G. Cassman, D.T. Walters, J.M. 

Knops, T.J. Arkebauer, A.E. Suyker, G.G. Burba, B. Amos, 

H.S. Yang, D. Ginting, K.G. Hubbard, A.A. Gitelson, and E.A. 

Walter-Shea, 2005: Annual carbon dioxide exchange in irrigated and rainfed maize-based agroecosystems. Agricultural and 

Forest Meteorology, 131(1-2), 77-96.

Wofsy, S.C., M.L. Goulden, J.W. Munger, S.-M. Fan, P.S. Bakwin, B.C. Daube, S.L. Bassow, and F.A. Bazzaz, 1993: Net exchange of CO2 in a mid-latitude forest. Science, 260(5112), 

1314-1317.

APPENDIX D REFERENCES 

Amiro, B.D., A.G. Barr, T.A. Black, H. Iwashita, N. Kljun, J.H. 

McCaughey, K. Morgenstern, S. Murayama, Z. Nesic, A.L. Orchansky, and N. Saigusa, 2005: Carbon, energy and water fluxes at mature and disturbed forest sites, Saskatchewan, Canada. 

Agricultural and Forest Meteorology, 136(3-4), 237-251.

Arain, M.A. and N. Restrepo-Coupe, 2005: Net ecosystem production in an eastern white pine plantation in southern Canada. 

Agricultural and Forest Meteorology, 128(3-4), 223-241. 

Chapin, F.S. III, G.M. Woodwell, J.T. Randerson, G.M. Lovett, 

E.B. Rastetter, D.D. Baldocchi, D.A. Clark, M.E. Harmon, 

D.S. Schimel, R. Valentini, C. Wirth, J.D. Aber, J.J. Cole, M.L. 

Goulden, J.W. Harden, M. Heimann, R.W. Howarth, P.A. Matson, A.D. McGuire, J.M. Melillo, H.A. Mooney, J.C. Neff, 

R.A. Houghton, M.L. Pace, M.G. Ryan, S.W. Running, O.E. 

Sala, W.H. Schlesinger, E. D. Schulze, 2006. Reconciling carbon-cycle concepts, terminology, and methodology. Ecosystems 9(7), 1041-1050.

Clark, K.L., H.L. Gholz, and M.S. Castro, 2004: Carbon dynamics along a chronosequence of slash pine plantations in north 

Florida. Ecological Applications, 14(4), 1154-1171.

Giardina, C.P., D. Binkley, M.G. Ryan, J.H. Fownes, and R.S. 

Senock, 2004: Belowground carbon cycling in a humid tropical forest decreases with fertilization. Oecologia, 139(4), 545-

550.

Griffis, T.J., T.A. Black, K. Morgenstern, A.G. Barr, Z. Nesic, 

G.B. Drewitt, D. Gaumont-Guay, and J.H. McCaughey, 2003: 

Ecophysiological controls on the carbon balances of three 

southern boreal forests. Agricultural and Forest Meteorology, 

117(1-2), 53-71.

Humphreys, E.R., T.A. Black, K. Morgenstern, Z. Li, and Z. Nesic, 2005: Net ecosystem production of a Douglas-fir stand for 

three years following clearcut harvesting. Global Change Biology, 11(3), 450-464.

Law, B.E., E. Falge, D.D. Baldocchi, P. Bakwin, P. Berbigier, 

K. Davis, A.J. Dolman, M. Falk, J.D. Fuentes, A. Goldstein, 

A. Granier, A. Grelle, D. Hollinger, I.A. Janssens, P. Jarvis, 
The U.S. Climate Change Science Program References

234 

N.O. Jensen, G. Katul, Y. Mahli, G. Matteucci, R. Monson, W. 

Munger, W. Oechel, R. Olson, K. Pilegaard, K.T. Paw, H. Thorgeirsson, R. Valentini, S. Verma, T. Vesala, K. Wilson, and S. 

Wofsy, 2002: Environmental controls over carbon dioxide and 

water vapor exchange of terrestrial vegetation. Agricultural 

and Forest Meteorology, 113(1-2), 97-120.

Lugo, A.E., J.F. Colón, and F.N. Scatena, 1999: The Caribbean. 

In: North American Terrestrial Vegetation [Barbour, M.G. and 

W.D. Billings (eds.)]. Cambridge University Press, Cambridge, 

United Kingdom, 530 pp.

Osher, L.J., P.A. Matson, and R. Amundson, 2003: Effect of land 

use change on soil carbon in Hawaii. Biogeochemistry, 65(2), 

213-232. 

Randerson, J.T., F.S. Chapin, III, J.W. Hardin, J.C. Neff, and M.E. 

Harmon, 2002. Net ecosystem production: a comprehensive 

measure of net carbon accumulation by ecosystems. Ecological Applications 12(4): 937-947.

APPENDIX e REFERENCES 

Chapin, F.S. III, G.M. Woodwell, J.T. Randerson, G.M. Lovett, 

E.B. Rastetter, D.D. Baldocchi, D.A.Clark, M.E. Harmon, 

D.S. Schimel, R. Valentini, C. Wirth, J.D. Aber, J.J. Cole, M.L. 

Goulden, J.W. Harden, M. Heimann, R.W. Howarth, P.A. Matson, A.D. McGuire, J.M. Melillo, H.A. Mooney, J.C. Neff, R.A. 

Houghton, M.L. Pace, M.G. Ryan, S.W. Running, O.E. Sala, 

W.H. Schlesinger, E. D. Schulze, 2006. Reconciling carboncycle concepts, terminology, and methodology. Ecosystems 9, 

1041-1050.

Fitzsimmons, M.J., D.J. Pennock, and J. Thorpe, 2004: Effects 

of deforestation on ecosystem carbon densities in central Saskatchewan, Canada. Forest Ecology and Management, 188(1-

3), 349-361.

Harmon, M.E., J.M. Harmon, W.K. Ferrell, and D. Brooks, 1996: 

Modeling carbon stores in Oregon and Washington forest products: 1900-1992. Climatic Change, 33(4), 521-550.

Harmon, M., 2001: Carbon sequestration in forests - addressing 

the scale question. Journal of Forestry, 99, 24-29.

Harmon, M. and P. Marks, 2002: Effects of silvicultural practices 

on carbon stores in Douglas-fir-western hemlock forests in the 

Pacific Northwest, USA: results from a simulation model. Canadian Journal of Forest Research, 32(5), 863-877.

Janisch, J. and M. Harmon, 2002: Successional changes in live 

and dead wood carbon stores: implications for net ecosystem 

productivity. Tree Physiology, 22(2-3), 77-89.

Jenkins, J.C., D.C. Chojnacky, L.S. Heath, and R.A. Birdsey, 

2003: National-scale biomass estimators for United States tree 

species. Forest Science, 49(1), 12-35.

Peterson, E.B., G.M. Bonnor, G.C. Robinson, and N.M. Peterson, 1999: Carbon Sequestration Aspects of an Afforestation 

Program in Canada’s Prairie Provinces. Joint Forest Sector 

Table/Sinks Table, National Climate Change Process, Ottawa, 

Ontario, Canada. Available at http://www.nccp.ca/NCCP/national_process/issues/sinks_e.html

Pregitzer, K.S. and E.S. Euskirchen, 2004: Carbon cycling and 

storage in world forests: biomes patterns related to forest age. 

Global Change Biology, 10(12), 2052-2077.

Ryan, M.G., D. Binkley, and J.H. Fownes, 1997: Age-related decline in forest productivity: pattern and process. Advances in 

Ecological Research, 27, 213-262.

Schulze, E., J. Lloyd, F. Kelliher, C. Wirth, C. Rebmann, B. Luhker, M. Mund, A. Knohl, I. Milyukova, W. Schulze, W. Ziegler, 

A. Varlagin, A. Sogachev, R. Valentini, S. Dore, S. Grigoriev, 

O. Kolle, M. Panfyorov, N. Tchebakova, and N. Vygodskaya, 

1999: Productivity of forests in the Eurosiberian boreal region 

and their potential to act as a carbon sink - a synthesis. Global 

Change Biology, 5(6), 703-722.

Stainback, G.A. and J.R.R. Alavalapati, 2005: Effects of carbon 

markets on the optimal management of slash pine (Pinus elliottii) plantations. Southern Journal of Applied Forestry, 29(1), 

27-32.

Stanturf, J.A., R.C. Kellison, F.S. Broerman, and S.B. Jones, 

2003: Productivity of southern pine plantations - where we are 

and how did we get here? Journal of Forestry, 101(3), 26-31.

Woodwell, G. and R. Whittaker, 1968: Primary production in terrestrial communities. American Zoologist, 8, 19-30.

Appendix F REFERENCES

Alford, D.P., R.D. Delaune, and C.W. Lindau, 1997: Methane flux 

from Mississippi River deltaic plain wetlands. Biogeochemistry, 37(3), 227–236.

Armentano, T.B. and E.S. Menges, 1986: Patterns of change in 

the carbon balance of organic soil-wetlands of the temperate 

zone. Journal of Ecology, 74(3), 755–774.

Aselmann, I. and P.J. Crutzen, 1989: Global distribution of natural 

freshwater wetlands and rice paddies, their net primary productivity, seasonality and possible methane emissions. Journal of 

Atmospheric Chemistry, 8(4), 307–359.

Bartlett, D.S., K.B. Bartlett, J.M. Hartman, R.C. Harriss, D.I. Sebacher, R. Pelletier-Travis, D.D. Dow, and D.P. Brannon, 1989: 

Methane emissions from the Florida Everglades: patterns of 

variability in a regional wetland ecosystem. Global Biogeochemical Cycles, 3(4), 363–374.

Bartlett, K.B., D.S. Bartlett, R.C. Harriss, and D.I. Sebacher, 

1987: Methane emissions along a salt marsh salinity gradient. 

Biogeochemistry, 4(3), 183–202.

Bartlett, K.B. and R.C. Harriss, 1993: Review and assessment of 

methane emissions from wetlands. Chemosphere, 26(1-4), 

261–320.

Bartlett, K.B., R.C. Harriss, and D.I. Sebacher, 1985: Methane 

flux from coastal salt marshes. Journal of Geophysical Research, 90(D3), 5710–5720.

Batjes, N.H., 1996: Total carbon and nitrogen in the soils of the 

world. European Journal of Soil Science, 47(2), 151–163.

Birdsey, R.A., 1992: Carbon Storage and Accumulation in United 

States Forest Ecosystems. General Technical Report WO-59, 

USDA Forest Service, Washington, DC.
235

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

Bridgham, S.D., C.-L. Ping, J.L. Richardson, and K. Updegraff, 

2000: Soils of northern peatlands: Histosols and Gelisols. In: 

Wetland Soils: Genesis, Hydrology, Landscapes, and Classification [Richardson, J.L. and M.J. Vepraskas (eds.)]. CRC 

Press, Boca Raton, FL, pp. 343–370.

Bridgham, S.D., K. Updegraff, and J. Pastor, 1998: Carbon, nitrogen, and phosphorus mineralization in northern wetlands. 

Ecology, 79(5), 1545–1561.

Brown, M.J., G.M. Smith, and J. McCollum, 2001: Wetland Forest 

Statistics for the South Atlantic States. RB-SRS-062, Southern 

Research Station, U.S. Forest Service, Asheville, NC, 52 pp.

Burke, R.A., T.R. Barber, and W.M. Sackett, 1988: Methane flux 

and stable hydrogen and carbon isotope composition of sedimentary methane from the Florida Everglades. Global Biogeochemical Cycles, 2(4), 329–340.

Carroll, P.C. and P.M. Crill, 1997: Carbon balance of a temperate 

poor fen. Global Biogeochemical Cycles, 11(3), 349–356.

Chanton, J.P., G.J. Whiting, J.D. Happell, and G. Gerard, 1993: 

Contrasting rates and diurnal patterns of methane emission 

from emergent aquatic macrophytes. Aquatic Botany, 46(2), 

111–128.

Chanton, J.P., G.J. Whiting, W.J. Showers, and P.M. Crill, 1992: 

Methane flux from Peltandra virginica: stable isotope tracing and chamber effects. Global Biogeochemical Cycles, 6(1), 

15–31.

Chimner, R.A. and D.J. Cooper, 2003: Carbon dynamics of pristine and hydrologically modified fens in the southern Rocky 

Mountains. Canadian Journal of Botany, 81(5), 477–491.

Chmura, G.L., S.C. Anisfeld, D.R. Cahoon, and J.C. Lynch, 

2003: Global carbon sequestration in tidal, saline wetland soils. 

Global Biogeochemical Cycles, 17(4), 1111, doi:10.1029/

2002GB001917.

Cleary, J., N.T. Roulet, and T.R. Moore, 2005: Greenhouse gas 

emissions from Canadian peat extraction, 1990–2000: a lifecycle analysis. Ambio, 34(6), 456–461.

Clymo, R.S., J. Turunen, and K. Tolonen, 1998: Carbon accumulation in peatland. Oikos, 81(2), 368–388.

Coles, J.R.P. and J.B. Yavitt, 2004: Linking belowground carbon 

allocation to anaerobic CH4 and CO2 production in a forested 

peatland, New York State. Geomicrobiology Journal, 21(7), 

445–454.

Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe, 1979: 

Classification of Wetlands and Deepwater Habitats of the 

United States. FWS/OBS-79/31, Fish and Wildlife Service, 

U.S. Department of the Interior, Washington, DC, 131 pp.

Craft, C.B. and W.P. Casey, 2000: Sediment and nutrient accumulation in floodplain and depressional freshwater wetlands of 

Georgia, USA. Wetlands, 20(2), 323–332.

Dahl, T.E., 1990: Wetland Losses in the United States 1970’s to 

1980’s. U.S. Department of the Interior, Fish and Wildlife Service, Washington, DC, 13 pp.

Dahl, T.E., 2000: Status and Trends of Wetlands in the Conterminous United States, 1986 to 1997. U.S. Department of the 

Interior, Fish and Wildlife Service, Washington, DC, 82 pp.

Dahl, T.E. and C.E. Johnson, 1991: Status and Trends of Wetlands 

in the Conterminous United States, Mid-1970’s to Mid-1980’s. 

U.S. Department of the Interior, Fish and Wildlife Service, 

Washington, DC, 22 pp.

Davidson, I., R. Vanderkam, and M. Padilla, 1999: Review of 

wetland inventory information in North America. In: Global 

Review of Wetland Resources and Priorities for Wetland Inventory [Finlayson, C.M. and A.G. Spiers (eds.)]. Supervising 

Scientist Report 144, Supervising Scientist, Canberra, Australia, 35 pp.

DeLaune, R.D., C.J. Smith, and W.H. Patrick Jr., 1983: Methane 

release from Gulf coast wetlands. Tellus, 35B(1), 8–15.

Dise, N., 1993: Methane emissions from Minnesota peatlands: 

spatial and seasonal variability. Global Biogeochemical Cycles, 7(1), 123–142.

Dise, N.B. and E.S. Verry, 2001: Suppression of peatland methane 

emission by cumulative sulfate deposition in simulated acid 

rain. Biogeochemistry, 53(2), 143–160.

Ehhalt, D., M. Prather, F. Dentener, E. Dlugokencky, E. Holland, 

I. Isaksen, J. Katima, V. Kirchhoff, P. Matson, P. Midgley, and 

M. Wang, 2001: Atmospheric chemistry and greenhouse gases. 

In: Climate Change 2001: The Scientific Basis. Contribution 

of Working Group I to the Third Assessment Report of the 

Intergovernmental Panel on Climate Change [Houghton, J.T., 

Y. Ding, D.J. Griggs, M. Noguer, P.J. van der Linden, X. Dai, 

K. Maskell, and C.A. Johnson (eds.)]. Cambridge University 

Press, Cambridge, United Kingdom, pp. 239–287.

Eswaran, H., E. Van Den Berg, and J. Kimble, 1995: Global soil 

carbon resources. In: Soils and Global Change [Lal, R., J. 

Kimble, E. Levine, and B.A. Stewart (eds.)]. Lewis Publishers, 

Boca Raton, FL, pp. 27–43.

Euliss, N.H., R.A. Gleason, A. Olness, R.L. McDougal, H.R. 

Murkin, R.D. Robarts, R.A. Bourbonniere, and B.G. Warner, 

2006: North American prairie wetlands are important nonforested land-based carbon storage sites. Science of the Total Environment, 361(1-3), 179–188.

FAO (Food and Agriculture Organization of the United Nations), 

1991: The Digitized Soil Map of the World. World Soil Resource Report 67, FAO, Rome, Italy.

FAO-UNESCO (Food and Agriculture Organization, United Nations Educational, Scientific and Cultural Organization), 1974: 

Soil Map of the World. 1:5,000,000 scale map, UNESCO, Paris, France.

Field, D.W., A.J. Reyer, P.V. Genovese, and B.D. Shearer, 1991: 

Coastal Wetlands of the United States: An Accounting of a Valuable Natural Resource. Strategic Assessment Branch, Ocean 

Assessments Division, Office of Oceanography and Marine 

Assessment, National Ocean Service, National Oceanic and 

Atmospheric Administration, Washington, DC, 59 pp.

Frayer, W.E., T.J. Monahan, D.C. Bowden, and F.A. Graybill, 

1983: Status and Trends of Wetlands and Deepwater Habitats 

in the Conterminous United States, 1950s to 1970s. Department of Forest and Wood Sciences, Colorado State University, 

Fort Collins, CO, 31 pp.
The U.S. Climate Change Science Program References

236 

Frolking, S. and P. Crill, 1994: Climate controls on temporal variability of methane flux from a poor fen in southeastern New 

Hampshire: measurement and modeling. Global Biogeochemical Cycles, 8(4), 385–397.

Gorham, E., 1991: Northern peatlands: role in the carbon cycle 

and probable responses to climatic warming. Ecological Applications, 1(2), 182–195.

Gunnison, D., R.L. Chen, and J.M. Brannon, 1983: Relationship 

of materials in flooded soils and sediments to the water-quality 

of reservoirs. 1. Oxygen-consumption rates. Water Research, 

17(11), 1609–1617.

Hall, J.V., W.E. Frayer, and B.O. Wilen, 1994: Status of Alaska 

Wetlands. U.S. Fish and Wildlife Service, Anchorage, Alaska, 

32 pp.

Halsey, L.A., D.H. Vitt, and L.D. Gignac, 2000: Sphagnumdominated peatlands in North America since the last glacial 

maximum: their occurence and extent. The Bryologist, 103(2), 

334–352.

Hanson, A.R. and L. Calkins, 1996: Wetlands of the Maritime 

Provinces: Revised Documentation for the Wetlands Inventory. 

Technical Report No. 267, Canadian Wildlife Service, Atlantic 

Region, Sackville, New Brunswick, Canada, 67 pp.

Happell, J.D., J.P. Chanton, G.J. Whiting, and W.J. Showers, 

1993: Stable isotopes as tracers of methane dynamics in Everglades marshes with and without active populations of methane 

oxidizing bacteria. Journal of Geophysical Research, 98(D8), 

14771–14782.

Harden, J.W., J.M. Sharpe, W.J. Parton, D.S. Ojima, T.L. Fries, 

T.G. Huntington, and S.M. Dabney, 1999:. Dynamic replacement and loss of soil carbon on eroding cropland. Global Biogeochemical Cycles, 13(4), 885–901.

Harriss, R.C. and D.I. Sebacher, 1981: Methane flux in forested 

freshwater swamps of the southeastern United States. Geophysical Research Letters, 8(9), 1002–1004.

Harriss, R.C., D.I. Sebacher, K.B. Bartlett, D.S. Bartlett, and 

P.M. Crill, 1988: Sources of atmospheric methane in the south 

Florida environment. Global Biogeochemical Cycles, 2(3), 

231–243.

Harriss, R.C., D.I. Sebacher, and F.P. Day, Jr., 1982: Methane flux 

in the Great Dismal Swamp. Nature, 297(5868), 673–674.

Johnston, C.A., 1991: Sediment and nutrient retention by freshwater wetlands: effects on surface water quality. Critical Reviews in Environmental Control, 21, 491–565.

Johnston, C.A., S.D. Bridgham, and J.P. Schubauer-Berigan, 

2001: Nutrient dynamics in relation to geomorphology of riverine wetlands. Soil Science Society of America Journal, 65(2), 

557–577.

Joosten, H. and D. Clarke, 2002: Wise Use of Mires and Peatlands 

- Background Principles Including a Framework for DecisionMaking. International Mire Conservation Group and International Peat Society, Saarijärvi, Finland, 304 pp.

Kelly, C.A., C.S. Martens, and W. Ussler III, 1995: Methane dynamics across a tidally flooded riverbank margin. Limnology 

and Oceanography, 40(6), 1112–1129.

Kelly, C.A., J.W.M. Rudd, R.A. Bodaly, N.T. Roulet, V.L. St. 

Louis, A. Heyes, T.R. Moore, S. Schiff, R. Aravena, K.J. Scott, 

B. Dyck, R. Harris, B. Warner, and G. Edwards, 1997: Increase 

in fluxes of greenhouse gases and methyl mercury following 

flooding of an experimental reservoir. Environmental Science 

& Technology, 31(5), 1334–1344.

Kim, J., S.B. Verma, and D.P. Billesbach, 1999: Seasonal variation 

in methane emission from a temperate Phragmites-dominated 

marsh: effect of growth stage and plant-mediated transport. 

Global Change Biology, 5(4), 433-440.

King, G.M. and W.J. Wiebe, 1978: Methane release from soils 

of a Georgia salt marsh. Geochimica et Cosmochimica Acta, 

42(4), 343–348.

Kivinen, E. and P. Pakarinen, 1981: Geographical distribution of 

peat resources and major peatland complex types in the world. 

Annales Academiae Scientiarum Fennicae, Series A, 3(132), 

1–28.

Kristensen, E., S.I. Ahmed, and A.H. Devol, 1995: Aerobic and 

anaerobic decomposition of organic matter in marine sediment: Which is fastest? Limnology and Oceanography, 40(9), 

1430–1437.

Lansdown, J., P. Quay, and S. King, 1992: CH4 production via 

CO2 reduction in a temperate bog: a source of 13C-depleted 

CH4. Geochimica et Comsochimica Acta, 56(9), 3493-3503.

Lappalainen, E., 1996: General review on world peatland and 

peat resources. In: Global Peat Resources [Lappalainen, E. 

(ed.)]. International Peat Society and Geological Survey of 

Finland, Jyskä, Finland, pp. 53–56.

Lugo, A.E. and S.C. Snedaker, 1974: The ecology of mangroves. 

Annual Review of Ecology and Systematics, 5, 39–64.

Maltby, E. and P. Immirzi, 1993: Carbon dynamics in peatlands 

and other wetland soils, regional and global perspectives. Chemosphere, 27(6), 999–1023.

Malterer, T.J., 1996: Peat resources of the United States. In: 

Global Peat Resources [Lappalainen, E. (ed.)]. International 

Peat Society and Geological Survey of Finland, Jyskä, Finland, 

pp. 253–260.

Matthews, E. and I. Fung, 1987: Methane emission from natural 

wetlands: global distribution, area, and environmental characteristics of sources. Global Biogeochemical Cycles, 1, 61–86.

Meade, R.H., T.R. Yuzyk, and T.J. Day, 1990: Movement and 

storage of sediments in rivers of the United States and Canada. 

In: Surface Water Hydrology. The Geology of North America, 

Vol. 0-1 [Wolman, M.G. and H.C. Riggs (eds.)]. Geological 

Society of America, Boulder, CO, pp. 255–280.

Megonigal, J.P. and W.H. Schlesinger, 2002: Methane-limited 

methanotrophy in tidal freshwater swamps. Global Biogeochemical Cycles, 16(4), 1088, doi:1010.1029/2001GB001594.

Mendelssohn, I.A. and K.L. McKee, 2000: Saltmarshes and mangroves. In: North American Terrestrial Vegetation [Barbour, 

M.G. and W.D. Billings (eds.)]. Cambridge University Press, 

Cambridge, United Kingdom, pp. 501–536.

Miller, D.N., W.C. Ghiorse, and J.B. Yavitt, 1999: Seasonal patterns and controls on methane and carbon dioxide fluxes in 
237

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

forested swamp pools. Geomicrobiology Journal, 16(4), 325–

331.

Mitsch, W.J. and J.G. Gosselink, 1993: Wetlands. Van Nostrand 

Reinhold, New York, 722 pp.

Moore, T.R. and N.T. Roulet, 1995: Methane emissions from 

Canadian peatlands. In: Soils and Global Change [Lal, R., J. 

Kimble, E. Levine, and B.A. Stewart (eds.)]. Lewis Publishers, 

Boca Raton, FL, pp. 153–164.

Moore, T.R., N.T. Roulet, and J.M. Waddington, 1998: Uncertainty in predicting the effect of climatic change on the carbon cycling of Canadian peatlands. Climatic Change, 40(2), 

229–245.

Moser, M., C. Prentice, and S. Frazier, 1996: A Global Overview 

of Wetland Loss and Degradation. Proceeding of the 6th Meeting of the Conference of Contracting Parties, Brisbane, Australia, Papers, Technical Session B, /Vol 10/12B, 19-27 March 

1996, Ramsar Convention Bureau, Gland, Switzerland, 21-31.

Naiman, R.J., T. Manning, and C.A. Johnston, 1991: Beaver 

population fluctuations and tropospheric methane emissions in 

boreal wetlands. Biogeochemistry, 12(1), 1–15.

National Wetlands Working Group, 1988: Wetlands of Canada. 

Sustainable Development Branch, Environment Canada, Ottawa, Ontario, and Polyscience Publications Inc, Montreal, 

Quebec, 452 pp.

Neff, J.C., W.D. Bowman, E.A. Holland, M.C. Fisk, and S.K. 

Schmidt, 1994: Fluxes of nitrous oxide and methane from nitrogen-amended soils in a Colorado alpine ecosystem. Biogeochemistry, 27(1), 23–33.

Neubauer, S.C., W.D. Miller, and I.C. Anderson, 2000: Carbon 

cycling in a tidal freshwater marsh ecosystem: a carbon gas 

flux study. Marine Ecology Progress Series, 199, 13–30.

NRCS (Natural Resources Conservation Service), 1999: Soil Taxonomy: A Basic System of Soil Classification for Making and 

Interpreting Soil Surveys, Second Edition. NRCS, U.S. Department of Agriculture, Washington, DC, 869 pp.

Odum, W.E., T.J. Smith, III, J.K. Hoover, and C.C. McIvor, 1984: 

The Ecology of Tidal Freshwater Marshes of the United States 

East Coast: A Community Profile. FWS/OBS-83/17, U.S. Fish 

and Wildlife Service, Washington, DC, 177 pp.

Olmsted, I., 1993: Wetlands of Mexico. In: Wetlands of the World

[Whigham, D.F., D. Dykjová, and S. Hejný (eds.)]. Kluwer Academic Publishers, Dordrecht, The Netherlands, pp. 637–677.

Ovenden, L., 1990: Peat accumulation in northern wetlands. Quaternary Research, 33(3), 377–386.

Pulliam, W.M., 1993: Carbon dioxide and methane exports from 

a southeastern floodplain swamp. Ecological Monographs, 63, 

29–53.

Rieger, S., D.B. Schoephoster, and C.E. Furbush, 1979: Exploratory Soil Survey of Alaska. U.S. Department of Agriculture 

Soil Conservation Service, Anchorage, Alaska, 213 pp.

Robinson, S.D. and T.R. Moore, 1999: Carbon and peat accumulation over the past 1200 years in a landscape with discontinuous permafrost, northwestern Canada. Global Biogeochemical 

Cycles, 13(2), 591–602.

Rubec, C., 1996: The status of peatland resources in Canada. In: 

Global Peat Resources [Lappalainen, E. (ed.)]. International 

Peat Society and Geological Survey of Finland, Jyskä, Finland, 

pp. 243–252.

Schipper, L.A. and K.R. Reddy, 1994: Methane production and 

emissions from four reclaimed and pristine wetlands of southeastern United States. Soil Science Society of America, 58, 

1270–1275.

Shannon, R.D. and J.R. White, 1994: A three year study of controls on methane emissions from two Michigan peatlands. Biogeochemistry, 27(1), 35–60.

Shurpali, N.J. and S.B. Verma, 1998: Micrometeorological measurements of methane flux in a Minnesota peatland during two 

growing seasons. Biogeochemistry, 40(1), 1–15.

Smith, L.K. and W.M. Lewis Jr., 1992: Seasonality of methane 

emissions from five lakes and associated wetlands of the Colorado Rockies. Global Biogeochemical Cycles, 6(4), 323–338.

Smith, S.V., W.H. Renwick, R.W. Buddemeier, and C.J. Crossland, 

2001: Budgets of soil erosion and deposition for sediments and 

sedimentary organic carbon across the conterminous United 

States. Global Biogeochemical Cycles, 15(3), 697–707.

Spalding, M., F. Blasco, and C. Field (eds.), 1997: World Mangrove Atlas. The International Society for Mangrove Ecosystems, Okinawa, Japan, 178 pp.

Spiers, A.G., 1999: Review of international/continental wetland 

resources. In: Global Review of Wetland Resources and Priorities for Wetland Inventory [Finlayson, C.M. and A.G. Spiers 

(eds.)]. Supervising Scientist Report 144, Supervising Scientist, Canberra, Australia.

Stallard, R.F., 1998: Terrestrial sedimentation and the carbon cycle: coupling weathering and erosion to carbon burial. Global 

Biogeochemical Cycles, 12(2), 231–257.

Tarnocai, C., 1998: The amount of organic carbon in various soil 

orders and ecological provinces in Canada. In: Soil Processes 

and the Carbon Cycle [Lal, R., J.M. Kimble, R.F. Follett, and 

B.A. Stewart (eds.)]. CRC Press, Boca Raton, FL, pp. 81–92.

Tarnocai, C., I.M. Kettles, and B. Lacelle, 2005: Peatlands of 

Canada. 1:6,500,000 scale map, Agriculture and Agri-Food 

Canada, Research Branch, Ottawa, Ontario, Canada.

Tolonen, K. and J. Turunen, 1996: Accumulation rates of carbon 

in mires in Finland and implications for climate change. Holocene, 6, 171–178.

Trimble, S.W. and P. Crosson, 2000: Land use - US soil erosion 

rates - Myth and reality. Science, 289(5477), 248–250.

Trumbore, S.E. and J.W. Harden, 1997: Accumulation and turnover of carbon in organic and mineral soils of the BOREAS 

northern study area. Journal of Geophysical Research, 

102(D24), 28817–28830.

Turetsky, M.R., R.K. Wieder, L.A. Halsey, and D. Vitt, 2002: Current disturbance and the diminishing peatland carbon sink. Geophysical Research Letters, 29, doi:10.1029/2001GL014000.

Turunen, J., N.T. Roulet, and T.R. Moore, 2004: Nitrogen deposition and increased carbon accumulation in ombrotrophic peat-
The U.S. Climate Change Science Program References

238 

lands in eastern Canada. Global Biogeochemical Cycles, 18, 

GB3002, doi:3010.1029/2003GB002154.

Twilley, R.R., R.H. Chen, and T. Hargis, 1992: Carbon sinks in 

mangroves and their implications to carbon budget of tropical coastal ecosystems. Water, Air and Soil Pollution, 64(1), 

265–288.

Valiela, I., J.L. Bowen, and J.K. York, 2001: Mangrove forests: 

one of the world’s threatened major tropical environments. 

BioScience, 51(10), 807–815.

Vitt, D.H., L.A. Halsey, I.E. Bauer, and C. Campbell, 2000: Spatial 

and temporal trends in carbon storage of peatlands of continental western Canada through the Holocene. Canadian Journal of 

Earth Sciences, 37(5), 683–693.

Vitt, D.H., L.A. Halsey, and S.C. Zoltai, 1994: The bog landforms 

of continental western Canada in relation to climate and permafrost patterns. Arctic and Alpine Research, 26(1), 1–13.

Webb, R.S. and T. Webb III, 1988: Rates of sediment accumulation in pollen cores from small lakes and mires of eastern North 

America. Quaternary Research, 30(3), 284–297.

WEC (World Energy Council), 2001: Survey of Energy Resources. http://www.worldenergy.org/wec-geis/publications/reports/

ser/peat/peat.asp

Werner, C., K. Davis, P. Bakwin, C. Yi, D. Hurst, and L. Lock, 

2003: Regional-scale measurements of CH4 exchange from a 

tall tower over a mixed temperate/boreal lowland and wetland 

forest. Global Change Biology, 9(9), 1251–1261.

West, A.E., P.D. Brooks, M.C. Fisk, L.K. Smith, E.A. Holland, 

C.H. Jaeger III, S. Babcock, R.S. Lai, and S.K. Schmidt, 1999: 

Landscape patterns of CH4 fluxes in an alpine tundra ecosystem. Biogeochemistry, 45(3), 243–264.

Wickland, K.P., R.G. Striegl, S.K. Schmidt, and M.A. Mast, 1999: 

Methane flux in subalpine wetland and unsaturated soils in the 

southern Rocky Mountains. Global Biogeochemical Cycles, 

13(1), 101–113.

Wilson, J.O., P.M. Crill, K.B. Bartlett, D.I. Sebacher, R.C. Harriss, 

and R.L. Sass, 1989: Seasonal variation of methane emissions 

from a temperate swamp. Biogeochemistry, 8(1), 55–71.

Yavitt, J.B., 1997: Methane and carbon dioxide dynamics in Typha latifolia (L.) wetlands in central New York state. Wetlands, 

17(3), 394–406.

Yavitt, J.B., G.E. Lang, and A.J. Sexstone, 1990: Methane fluxes in wetland and forest soils, beaver ponds, and low-order 

streams of a temperate forest ecosystem. Journal of Geophysical Research, 95(D13), 22463–22474.

Yavitt, J.B., R.K. Wieder, and G.E. Lang, 1993: CO2 and CH4

dynamcis of a Sphagnum-dominated peatland in West Virginia. 

Global Biogeochemical Cycles, 7(2), 259–274.

Zedler, J.B. and S. Kercher, 2005: Wetland resources: status, 

trends, ecosystem services, and restorability. Annual Review of 

Environmental Resources, 30, 39–74.

aPPENDIX G REFERENCES

DaSilva, A., C. Young, and S. Levitus, 1994: Atlas of Surface 

Marine Data 1994, Vol. 1: Algorithms and Procedures. NOAA 

Atlas NESDIS 6, U.S. Department of Commerce, Washington, 

DC. v6, 83pp.

Wanninkhof, R., 1992: Relationship between wind speed and gas 

exchange. Journal of Geophysical Research, 97(C5), 7373-

7382.

Photography Credits

Cover/Title Page/Table of Contents

Cover, table of contents, pg 95, Image for Chapter 9 (Aerial view), 

Grant Goodge, STG Inc., Asheville, N.C..

Executive Summary

Page 1, (CP & L stacks), Grant Goodge, STG. Inc., Asheville, 

N.C.

Page 7, (Autumnal pond), Dave McGuirk, NOAA, NCDC, Asheville, N.C.

Page 13, (Power plant), Grant Goodge, STG. Inc., Asheville, 

N.C.

Chapter 1

Page 19, (Nuclear power plant), Deborah Misch, STG Inc., Asheville, N.C.

Chapter 2

Page 21 (Inversion), Grant Goodge, STG. Inc., Asheville, N.C.

Page 24 (Low visibility), Grant Goodge, STG. Inc., Asheville, 

N.C.

Page 25 (Aerial view), Grant Goodge, STG. Inc., Asheville, N.C.

Page 27, (Creek), Sara Veasey, NOAA, NCDC, Asheville, N.C.

Chapter 3

Page 35, (Aerial view), Grant Goodge, STG. Inc., Asheville, N.C.

Chapter 4

Page 39, (Palm Springs Wind Farm), Grant Goodge, STG. Inc., 

Asheville, N.C.

Page 46, (Aerial view Fontana Dam), Grant Goodge, STG. Inc., 

Asheville, N.C.

Chapter 6

Page 67, (Plume smoke), Grant Goodge, STG. Inc., Asheville, 

N.C.

Page 70, (Coal fired plant), Grant Goodge, STG. Inc., Asheville, 

N.C.

Chapter 7

Page 83, (Jet plane), Grant Goodge, STG. Inc., Asheville, N.C.
239

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

Chapter 8

Page 85, (Paper mill aerial), Grant Goodge, STG. Inc., Asheville, 

N.C.

Page 89, (Clear cut aerial), Grant Goodge, STG. Inc., Asheville, 

N.C.

Chapter 9

Page 95, Chapter Heading, Aerial urban view, Grant Goodge, 

STG. Inc., Asheville, N.C.

Page 95, (San Francisco, Calif.), Grant Goodge, STG. Inc., Asheville, N.C.

Page 96, 99, 102 (Manhatten, NY), Anne Waple, STG. Inc., Asheville, N.C.

Chapter 11

Page 117, (Trees and contrails), Grant Goodge, STG. Inc., Asheville, N.C.

Page 121, (Damaged shrub), Deborah Misch, STG. Inc., Asheville, N.C.

Page 122, (Rockies and yellow flowers), Dave McGuirk, NOAA, 

NCDC, Asheville, N.C.

Chapter 12

Page 136, (Alaskan Pipeline), Grant Goodge, STG. Inc., Asheville, N.C.

Chapter 13

Page 139, (Cattails, wetlands), Grant Goodge, STG. Inc., Asheville, N.C.

Chapter 14

Page 152,153, (Aerial building and traffic), Grant Goodge, STG. 

Inc., Asheville, N.C.

Page 154,155, (Urban trees), Sara Veasey, NOAA, NCDC, Asheville, N.C.

Appendix A

Page 167, (Mountain waterfall), Dave McGuirk, NOAA, NCDC, 

Asheville, N.C.

Appendix F

Page 184, (Wetlands), Grant Goodge, STG. Inc., Asheville, N.C.
The U.S. Climate Change Science Program References

2440 
2441

The First State of the Carbon Cycle Report (SOCCR) 

The North American Carbon Budget and Implications for the Global Carbon Cycle

Contact Information

Global Change Research Information Office

c/o Climate Change Science Program Office

1717 Pennsylvania Avenue, NW

Suite 250

Washington, DC 20006

202-223-6262 (voice)

202-223-3065 (fax)

The Climate Change Science Program 

incorporates the U.S. Global Change Research 

Program and the Climate Change Research 

Initiative.

To obtain a copy of this document, place 

an order at the Global Change Research 

Information Office (GCRIO) web site: 

http://www.gcrio.org/orders

Climate Change Science Program and the 

Subcommittee on Global Change Research

William J. Brennan, Chair

Department of Commerce

National Oceanic and Atmospheric Administration

Acting Director, Climate Change Science Program

Jack Kaye, Vice Chair

National Aeronautics and Space Administration

Allen Dearry

Department of Health and Human Services

Jerry Elwood

Department of Energy

Mary Glackin

National Oceanic and Atmospheric Administration

Patricia Gruber

Department of Defense

William Hohenstein

Department of Agriculture

Linda Lawson

Department of Transportation

Mark Myers

U.S. Geological Survey

Jarvis Moyers

National Science Foundation

Patrick Neale

Smithsonian Institution

Jacqueline Schafer

U.S. Agency for International Development 

Joel Scheraga

Environmental Protection Agency

Harlan Watson

Department of State

EXECUTIVE OFFICE AND 

OTHER LIAISONS

Melissa Brandt

Office of Management and Budget

Stephen Eule

Department of Energy

Director, Climate Change Technology Program

Katharine Gebbie

National Institute of Standards & Technology

George Banks

Council on Environmental Quality

Gene Whitney

Office of Science and Technology Policy
The U.S. Climate Change Science Program References

242 

U.S. Climate Change Science Program

1717 Pennsylvania Avenue, NW • Suite 250 • Washington, D.C. 20006 USA

1-202-223-6262 (voice) • 1-202-223-3065 (fax)

http://www.climatescience.gov