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Soot and Ozone, Two Overlooked Climate Culprits

Greenhouse gases get all the fame and attention nowadays, but there are actually a few other pollutants out there that are warming the planet as well, and many of them might even be cheaper and easier to clean up in the very short term. An essay in the latest issue of Foreign Affairs, by climatologist Veerabhadran Ramanathan and economist Jessica Wallack, looks at black carbon soot and ground-level ozone in particular—what they call the "low-hanging fruit" of the climate problem.

Black carbon is starting to get the broader scrutiny it deserves. The black carbon soot comes primarily from diesel vehicles and biomass-burning cookstoves in developing countries. Scientists have recently realized that the soot particles travel widely in the air, settling on glaciers and speeding up ice melt by absorbing the sun's heat. By some estimates, 50 percent of current Arctic warming is caused by black carbon, and the soot's also sizzling right through the glaciers in the Himalayas, imperiling water supplies for some one billion people.

Not only that, but black carbon pollution has been linked to a rash of respiratory infections in the developing world—by some counts causing 7 percent of child deaths worldwide. It's nasty stuff. What's more, it's remarkably easy to ameliorate: Diesel particulate filters for vehicles already exist, as do cleaner cookstoves that either run on solar power or burn the fuel cleanly. This is such a no-brainer concept that even James Inhofe, the Senate's most prominent climate-change denier, has co-sponsored a bill to aid black-carbon reduction projects abroad.

Then there's ground-level ozone (which acts differently from the ozone up in the ozone layer that protects us from UV rays). Ozone's created by gases such as carbon monoxide or nitrogen oxides that are emitted by various industrial processes. Down in the troposphere, ozone acts much like heat-trapnnig greenhouse gases—the IPCC has estimated that it's about 25 percent as potent as carbon-dioxide—but it's also been linked to increases in asthma and can take a toll on agriculture, with one 2000 study blaming ozone for some $15 billion to $20 billion worth of crop damage annually.

In any case, mopping up black carbon and ozone certainly isn't a substitute for reducing greenhouse-gas emissions. But it makes sense to start with the cheapest, easiest measures right away. (To give an example of cost-effectiveness, just retrofitting one million diesel trucks with filters to remove soot would be equivalent to taking 5.7 million cars off the road, from a climate standpoint.) And, since black carbon particles and ozone molecules persist in the atmosphere for less time than, say, carbon-dioxide does, phasing them out as quickly as possible could help slow down the current—and alarming—warming trends we're already seeing and buy the world some more time to focus on the harder reductions.

(Flickr photo credit: Manny Pabla)