Government Panel Releases Report on North America's Carbon BudgetGovernment Panel Releases Report on North America's Carbon Budget

On Nov. 13, the U.S. Climate Change Science Program (CCSP) announced the publication of a report that quantifies North America's net contribution of carbon to the atmosphere and catalogues sources and sinks of carbon on the continent.

"The North American Carbon Budget and Implications for the Global Carbon Cycle" is the latest report by the CCSP, which will publish 21 reports by the end of 2008. The report analyzes the amounts of carbon emitted by industry sector, the amount absorbed naturally and how these amounts relate to the global carbon budget influenced by other regions of the globe, with particular attention given to characterizing the certainty and uncertainty with which these budget elements are known.

"This information is critical to understanding the factors that shape our global climate," said Bill Brennan, acting CCSP director and deputy assistant secretary for international affairs for the National Oceanic and Atmospheric Administration (NOAA). "The 21 CCSP reports are designed to help scientists answer key questions about climate change, provide the best possible science to stimulate public discussion and assist decision-making on key climate-related issues. We now have a comprehensive understanding of how our continent is contributing to greenhouse gases overall."

According to the report, North America's fossil fuel emissions are greater than 25 percent of global emissions. The conversion of fossil fuels to energy, such as electricity generation, is the single largest carbon contributor, with transportation second. The report provides information on how the growth of North America's vegetation absorbs large amounts of carbon from the atmosphere.

The report points out a greater than three-to-one imbalance between the fossil fuel sources and the ability of vegetation to absorb carbon. This results in a net release to the atmosphere (more than one gigaton of carbon per year in 2003), but there is still some uncertainty in quantifying the North American sink compared to the carbon emission sources. The carbon absorption by vegetation, primarily in the form of forest growth, is expected to decline as maturing forests grow more slowly and take up less carbon dioxide from the atmosphere.

The report's authors find it unclear how rapidly this carbon storage "sink" will decline and whether it might potentially become a source since changes in climate and atmospheric carbon dioxide could affect forest growth differently in different regions. Further warming, for example, could exacerbate drought, increasing carbon release through vegetation dieback and increased fire and insect disturbances.

"This report serves an important function beyond being a critical part of the CCSP's synthesis and assessment structure," said Tony King, report team lead and staff scientist at the U.S. Energy Department's Oak Ridge National Laboratory.

A variety of local, regional and national policy approaches could affect the overall North American carbon contribution, according to the report's authors. These include changing the rates of emissions through energy efficiency improvement and fuel switching, enhancing sinks in vegetation and soil, and implementing carbon capture and geological storage.

Additional information on the report can be accessed at http://climatescience.gov/Library/sap/sap2-2/final-report/default.htm.

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