In addition to causing smoggy skies and chronic coughs, soot or black carbon turns out to be the number two contributor to global warming. It's second only to carbon dioxide, according to a four-year assessment by an international panel.
The new study concludes that black carbon, the soot particles in smoke and smog, contributes about twice as much to global warming as previously estimated, even by the 2007 Intergovernmental Panel on Climate Change.
"We were surprised at its potential contribution to climate," said Sarah Doherty, a University of Washington atmospheric scientist and one of four coordinating lead authors.
The silver lining may be that controlling these emissions can deliver more immediate climate benefits than trying to control carbon dioxide, she said.
The paper was made freely available online today (Jan. 15) in the Journal of Geophysical Research-Atmospheres.
Some previous research had hinted that models were underestimating black-carbon emissions, Doherty said, from such things as open burning of forests, crops and grasslands, and from energy-related emissions in Southeast Asia and East Asia.
Black carbon's role in climate is complex. Dark particles in the air work to shade the Earth's surface while warming the atmosphere. Black carbon that settles on the surface of snow and ice darkens the surface to absorb more sunlight and increase melting. Finally, soot particles influence cloud formation in ways that can have either a cooling or warming impact.
The report surveyed past studies and included new research to quantify the sources of black carbon and better understand its overall effect on the climate.
Doherty was executive director of the International Global Atmospheric Chemistry Project in 2009 when policy groups were seeking better information on the benefits of reducing black-carbon emissions. The scientific body undertook a comprehensive assessment, supported by IGAC and the U.S. National
|Contact: Hannah Hickey|
University of Washington