January 16th, 2013 by James Ayre
Black carbon, commonly known as ‘soot’, turns out to be a much more potent contributor to climate change than was previously thought, new research has found. So, in addition to the numerous health problems it causes, and the environmental destruction and deforestation that it is associated with, it is also a main driver of the climate change.
The new research has found that soot is second only to carbon dioxide with regards to how much it contributes to global warming. The research was based on an extremely extensive four-year assessment done by an international panel.
“We were surprised at its potential contribution to climate,” said Sarah Doherty, a University of Washington atmospheric scientist and one of the primary authors. “The silver lining may be that controlling these emissions can deliver more immediate climate benefits than trying to control carbon dioxide.”
There have been hints in recent years that the most commonly used models were underestimating the level of black-carbon emissions. The models didn’t accurately account for the truly enormous scale that fire-caused deforestation is occurring on (caused by slash-and-burn agriculture, but also by the increasing regularity of forest fires), and for the enormous emissions caused by the burning of organic material for heat throughout much of Southeast Asia.
“Black carbon’s role in climate is complex. Dark particles in the air work to shade 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. “We hope reducing black-carbon emissions buys us some time. But it doesn’t replace cutting back on CO2 emissions.”
“While carbon dioxide has a half-life of 100 years, black carbon stays in the atmosphere for only a few days. The authors investigated various sources of black carbon to see which reductions might have the most short-term cooling impact. Regulating emissions from diesel engines followed by replacing some wood- and coal-burning household stoves, authors find, would have the greatest immediate cooling impact.”
“If you’re just thinking about impact on climate, you would want to be strategic about which sources you cut back on,” Doherty said. “We looked at the overall impact because some of these sources also emit associated particles that can have counteracting effects.”
Soot contributes to global warming primarily “in the mid to high latitudes, including the northern United States, Canada, northern Europe and northern Asia, as well as affecting rainfall patterns of the Asian Monsoon.”
“The report incorporates data that Doherty and co-author Stephen Warren, a UW professor of atmospheric sciences, gathered between 2007 and 2009 to measure soot on Arctic snow. Calculating black carbon deposits in the Arctic is difficult, so data are essential for testing and correcting models.”
“Mitigating black carbon is good for curbing short-term climate change, but to really solve the long-term climate problem, carbon dioxide emissions must also be reduced,” Bond said.
While effective limitations on black carbon pollution would be much better than nothing, without very rapidly cutting down on carbon dioxide emissions the worst effects of climate change are bound to happen. And if anyone is really being realistic, they are bound to far eclipse the very conservative predictions that have been made so far.
The new research was just published, and is available for free, online in the Journal of Geophysical Research-Atmospheres.
Source: University of Washington
Image Credits: University of Washington; Soot Diesel via Wikimedia Commons
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