HR: 11:00h
AN: B42C-03    [Abstracts]
TI: A Pre-NACP Assessment of the North American Terrestrial Carbon Sink
AU: * King, A W
EM: kingaw@ornl.gov
AF: Environmental Sciences Division, Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37830-6335, United States
AU: Dilling, L
EM: ldilling@cires.colorado.edu
AF: Center for Science and Technology Policy Research, University of Colorado, 1333 Grandview Avenue, Campus Box 488, Boulder, CO 80309-0488, United States
AU: Zimmerman, G P
EM: zimmermangp@ornl.gov
AF: Environmental Sciences Division, Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37830-6335, United States
AU: Fairman, D M
EM: dfairman@cbuilding.org
AF: Consensus Building Institute, 238 Main Street, Suite 400, Cambridge, MA 02142, United States
AU: Houghton, R A
EM: rhoughton@whrc.org
AF: Woods Hole Research Center, 149 Woods Hole Road, Falmouth, MA 02540-1644, United States
AU: Marland, G H
EM: marlandgh@ornl.gov
AF: Environmental Sciences Division, Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37830-6335, United States
AU: Rose, A Z
EM: adamzros@sppd.usc.edu
AF: School of Policy, Planing and Development, University of Southern California, Lewis Hall 312, Los Angeles, CA 90089-0626, United States
AU: Wilbanks, T J
EM: wilbankstj@ornl.gov
AF: Environmental Sciences Division, Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37830-6335, United States
AB: A pre-North American Carbon Program (pre-NACP) evaluation of North American carbon sources and sinks was generated as part of the U.S. Climate Change Science Program's 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. The report found that 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. 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 conversion of fossil fuels to 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. Circa 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 27% of the fossil-fuel emissions from North America. The imbalance between the fossil-fuel source and the sink on land (a source:sink ratio of nearly 4:1) 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 timber land recovering from harvest. The second largest sink (approximately 25% of the North American sink) is associated with woody encroachment into grasslands and shrublands but is highly uncertain, known to no better than ± 100%, and may actually represent a small source. Other sinks are relatively small (individually 1-10% of the continental sink) 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, this expectation is confounded by uncertainty in how regrowing forests and other sinks will respond to changes in climate and elevated atmospheric carbon dioxide concentrations.
UR: http://cdiac.ornl.gov/SOCCR
DE: 0428 Carbon cycling (4806)
DE: 0485 Science policy (6620)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting