1. SOCCR CCSP SAP 2.2 State of the Carbon Cycle Report Slide 1 A Pre-NACP Assessment of the North American Terrestrial Carbon Sink 2007 AGU Fall Meeting 13 December 2007 San Francisco, CA Anthony King Oak Ridge National Laboratory And the SOCCR SAP 2.2 Scientific Coordination Team Anthony King (ORNL)Lisa Dilling (U. Colorado/NCAR) David Fairman (CBI)R.A. “Skee” Houghton (WHRC) Gregg Marland (ORNL)Adam Rose (USC) Tom Wilbanks (ORNL)Greg Zimmerman (ORNL)

2. SOCCR CCSP SAP 2.2 State of the Carbon Cycle Report Slide 2 The U.S. Climate Change Science Program (CCSP) Strategic Plan of July 2003 calls for the creation of a series of more than 20 synthesis and assessment reports “These products will support both policymaking and adaptive management.”

3. SOCCR CCSP SAP 2.2 State of the Carbon Cycle Report Slide 3 Under CCSP Goal 2: Improve quantification of the forces bringing about changes in the Earth's climate and related systems. Topics for Priority CCSP Synthesis Products included --- North American carbon budget and implications for the global carbon cycle. U.S. Carbon Cycle Interagency Working Group had already started an initiative to produce a potentially periodic State of the Carbon Cycle Report (SOCCR)

4. SOCCR CCSP SAP 2.2 State of the Carbon Cycle Report Slide 4 The First State of the Carbon Cycle Report. SOCCR was Initiated in 2004… Released as www.climatescience.gov/Library/sap/sap2-2/final-report/default.htm U.S. CCSP Synthesis and Assessment Product 2.2 The First State of the Carbon Cycle Report (SOCCR): North American Carbon Budget and Implications for the Global Carbon Cycle November 13, 2007 cdiac.ornl.gov/SOCCR/

5. SOCCR CCSP SAP 2.2 State of the Carbon Cycle Report Slide 5 A community document with over 90 authors from Canada, USA, Mexico, and significant involvement of stakeholders Part I: The Carbon Cycle in North America (Chs. 1-5) Gives overview of the North American carbon cycle and its global context, summarizes options and measures and how to improve the relevance of carbon cycle science Part II: Energy, Industry and Waste Management (Chs. 6-9) Details budgets for emissions from various sectoral activities, including energy, transportation, industry, waste management and buildings Part III: Land and Water Systems (Chs. 10-15) Details budgets for agricultural and forest lands, permafrost, wetlands, urban areas, and coastal regions.

6. SOCCR CCSP SAP 2.2 State of the Carbon Cycle Report Slide 6 A pre-NACP North American Carbon Budget (ca. 2003) A net terrestrial sink of 500  250 Mt C yr -1 is equivalent to about 30% of North American fossil fuel emissions in 2003.

7. SOCCR CCSP SAP 2.2 State of the Carbon Cycle Report Slide 7 North America is currently a net source of CO 2 to the atmosphere. The combustion of fossil-fuels in North America released nearly two billion metric tons of carbon to the atmosphere in 2003. Fossil-fuel emissions are dominated by emissions from the United States (85% in 2003, Canada 9% and Mexico 6%). Combustion of fossil fuel to produce energy commodities (primarily electricity) is the largest contributor (42% in 2003), transportation the second (31%). To summarize: The sources

8. SOCCR CCSP SAP 2.2 State of the Carbon Cycle Report Slide 8 A pre-NACP North American Carbon Budget (ca. 2003) A net terrestrial sink of 500  250 Mt C yr -1 is equivalent to about 30% of North American fossil fuel emissions in 2003.

9. SOCCR CCSP SAP 2.2 State of the Carbon Cycle Report Slide 9 Summarizing: The sinks A terrestrial sink of 500 (  50%) Mt C/year removed the equivalent of nearly 30% of North American fossil fuel emissions in 2003. The terrestrial sink is primarily associated with regrowing forests in the United States (  50% of the sink). The second largest sink, woody encroachment, is also the least well known.

10. SOCCR CCSP SAP 2.2 State of the Carbon Cycle Report Slide 10 How does this sink compare with other estimates? “Bottom-up” estimates ReferenceSink Estimate (Pg C y -1 ) Period SOCCR, 20070.5 ± 0.25ca. 2003 Pacala et al., 20010.30 – 0.581980-1989 (cont. USA only) Denman et al., 20070.3 – 0.61990’s

11. SOCCR CCSP SAP 2.2 State of the Carbon Cycle Report Slide 11 How does this sink compare with other estimates? “top-down” estimates ReferenceSink Estimate (Pg C y -1 )Period SOCCR, 20070.67 ± 0.33ca. 2003 Fan et al., 19981.71988-92 Schimel et al., 20010.8 (2.1 – source of 0.1)1990-94 Denman et al., 2007 0.6 – 1.11992-96 Peters et al., 20070.65 (0.4 – 1.0)2000-05

12. SOCCR CCSP SAP 2.2 State of the Carbon Cycle Report Slide 12 Gurney et al. 2004 Stephens et al. 2007 N mid-latitudes-2.4 + 1.1-1.5 + 0.6* Tropics 1.8 + 1.7 0.1 + 0.8 North America ~20% ~33% (10-30%) (15-50%) * -1.2 with correction for rivers Top-down estimates

13. SOCCR CCSP SAP 2.2 State of the Carbon Cycle Report Slide 13 A pre-NACP North American Carbon Budget (ca. 2003) A net terrestrial sink of 500  250 Mt C yr -1 is equivalent to about 30% of North American fossil fuel emissions in 2003.

14. SOCCR CCSP SAP 2.2 State of the Carbon Cycle Report Slide 14 Summarizing: The future of sources and sinks The fossil-fuel emissions source is likely to increase in the future. The future of the North American terrestrial sink is highly uncertain, with the expectation that the contribution of forest regrowth will decline as forests mature clouded by uncertainty in ecosystem response to CO 2 and climate. The current North American source:sink ratio of greater than 3:1 is likely to become larger

15. SOCCR CCSP SAP 2.2 State of the Carbon Cycle Report Slide 15 Significance of the first SOCCR (SAP 2.2) Effective management of North America’s contribution to global increases in atmospheric CO 2 would therefore need to focus on fossil fuel emissions. Provides a new baseline of knowledge for investigations like those of the North American Carbon Program (NACP) Provides a new bottom-up synthesis of the North American carbon budget. Sinks are collectively only 30% of fossil fuel emissions. Forest regrowth is currently the dominant sink. The future trajectory of this and other sinks is highly uncertain.

16. SOCCR CCSP SAP 2.2 State of the Carbon Cycle Report Slide 16 Acknowledgements Authors Stakeholders SOCCR Coordinating Team Our Agency Sponsors SOCCR Agency Executive Committee The NCDC Editors and Production Team Climate Change Science Program

17. SOCCR CCSP SAP 2.2 State of the Carbon Cycle Report Slide 17 SAP 2.2 Scientific Coordination Team Dr. Anthony King, Oak Ridge National Laboratory - Overall Lead Dr. Lisa Dilling, University of Colorado / National Center for Atmospheric Research - Co-Lead and Lead for Stakeholder Interaction Mr. Gregory Zimmerman, Oak Ridge National Laboratory - Project Coordinator Dr. David Fairman, Consensus Building Institute, Inc. - Stakeholder Interaction Dr. Richard (Skee) Houghton, Woods Hole Research Center - Scientific Content (Land Use) Dr. Gregg Marland, Oak Ridge National Laboratory - Scientific Content (Energy Emissions) Dr. Adam Rose, University of Southern California - Scientific Content (Economics) Dr. Thomas Wilbanks, Oak Ridge National Laboratory - Scientific Content (Human Dimensions)

18. SOCCR CCSP SAP 2.2 State of the Carbon Cycle Report Slide 18 SAP 2.2 Stakeholders Stakeholders participated from a wide variety of sectors: –Government –Academia –Fuel producers –Utilities –Forestry –Auto makers –Agriculture –Environmental advocates –Carbon traders 30 people were interviewed 28 attended workshops (some more than once) Some of the companies and institutions participating: Cinergy, Pew Center on Global Climate Change, Natural Resources Defense Council, Honda Motor Company, Western Fuels, National Council for Air and Stream Improvement, Chicago Climate Exchange, The Nature Conservancy, Edison Electric Institute, Resources for the Future, Saskatchewan Soil Conservation, American Forest and Paper Association, Iowa Farm Bureau, City of Denver, U.S. Department of the Treasury, U.S. Senate staff, Monsanto, CA Air Resources Board

19. SOCCR CCSP SAP 2.2 State of the Carbon Cycle Report Slide 19 Thank you

20. SOCCR CCSP SAP 2.2 State of the Carbon Cycle Report Slide 20 The First State of the Carbon Cycle Report. SOCCR was Initiated in 2004… Released as www.climatescience.gov/Library/sap/sap2-2/final-report/default.htm U.S. CCSP Synthesis and Assessment Product 2.2 The First State of the Carbon Cycle Report (SOCCR): North American Carbon Budget and Implications for the Global Carbon Cycle November 13, 2007 cdiac.ornl.gov/SOCCR/

21. SOCCR CCSP SAP 2.2 State of the Carbon Cycle Report Slide 21 Gurney et al. 2004 Stephens et al. 2007 N mid-latitudes-2.4 + 1.1-1.5 + 0.6* Tropics 1.8 + 1.7 0.1 + 0.8 * -1.2 with correction for rivers Top-down estimates

22. SOCCR CCSP SAP 2.2 State of the Carbon Cycle Report Slide 22 Treatment of uncertainty in SAP 2.2 Sources of uncertainty vary across sectors –Variation in time and space, measurement and sampling error, uncertainty in “expansion factors” and analytical models –Uncertainty about future socio-economics and the environment, in response to perturbation, in forecasting models To synthesize across this uncertainty and provide comparability we employed a characterization expressing relative confidence in a quantity –95% certain that the actual value is within 10% of the estimate reported –95% certain that the estimate is within 25% –within 50% –within 100% –uncertainty > 100%

23. SOCCR CCSP SAP 2.2 State of the Carbon Cycle Report Slide 23 SOCCR estimate of North American Terrestrial Sink % of Northern Hemisphere Terrestrial Sink by top-down bottom-up % of Global Residual Terrestrial Sink Low: 0.25 Pg C y -1 82% 66%28% Median: 0.50 Pg C y - 1 39% 51%19% High: 0.75 Pc C y -1 43% 47%17% Given the uncertainties, the North American terrestrial sink could be as little as 6% to as much as 83% of the global terrestrial sink. Comparison with IPCC AR4 Denman et al. (2007) Northern Hemisphere and global residual terrestrial sink