Soot is the second largest contributor to global warming

Carbon dioxide still leads, but black carbon is warming the world twice as much as we thought. Cutting emissions would have fast cooling effects, while saving lives: a "no brainer," researcher says.

The result of a 4-year, 232-page climate assessment is in. Dirty burning, it turns out, is the second most important man-made contributor to global warming, behind carbon dioxide.

In fact, soot appears to be warming the world twice as much as previously thought. And since these fine particles cause heart and respiratory problems, the same soot-reducing actions would also improve the health of billions of people.

Neither new observations nor new climate model runs were made for the study, ScienceNOW reports. Instead, thirty-one scientists from nine countries looked at data from ground-based sensors, satellite observations, and global emissions inventories.

  • Atmospheric soot particles 100 nanometers or so in diameter are absorbing enough solar energy to warm the atmosphere with about 1.1 Watts per square meter.
  • That’s double most previous estimates of the warming that occurs when fine carbon particles absorb radiation from the sun.
  • Black carbon’s impact on climate is about two-thirds that of the principle greenhouse gas, carbon dioxide. Methane from landfills and other sources comes in third.
  • Although carbon dioxide dominates the long-term effect, Nature News explains, reducing black carbon gives you immediate cooling.

Major sources of soot (pictured below) are diesel emissions and agricultural fires in industrialized countries, and biomass burning and wood-fired stoves for cooking and heat in developing countries. The study points to two leading targets for policymakers: diesel engines and wood and coal burning in small industries and homes.

"If we did everything we could to reduce these emissions," says study coauthor Piers Forster of the University of Leeds in a statement, "we could buy ourselves up to half a degree (Celsius) less warming -- or a couple of decades of respite."

Reducing emissions, he adds, “is a no brainer, as there are tandem health and climate benefits.”

The report was published online by the Journal of Geophysical Research today.

[Via ScienceNOW, Nature News, Washington Post]

Image: Above, diesel smoke from EPA via Wikimedia. Below, black carbon processes and sources from Bond et al., 2013

This post was originally published on Smartplanet.com

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