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Soot second biggest contributor to climate change

Soot, the black carbon that triggers smog and bouts of coughing, is also the biggest contributor to global warming after carbon dioxide, says a four-year assessment by US researchers.

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, University of Washington (UW) atmospheric scientist and one of four coordinating lead authors, the Journal of Geophysical Research-Atmospheres reports.

Black carbon contributes to climate change in the mid to high latitudes, including the northern US, Canada, northern Europe and northern Asia, as well as affecting rainfall patterns of the Asian monsoon.

The silver lining may be that controlling these emissions can deliver more immediate climate benefits than trying to control carbon dioxide, she said, according to a Washington statement.

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.

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.

‘Because of a lack of action to reduce carbon dioxide emissions, the policy community is asking what else we can do, particularly to help places like the Arctic that are melting much more quickly than we had anticipated,’ Doherty said.