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Soot, hydrofluorocarbs 'low-hanging fruit' to fight warming

Federal boffins insist heat tree be picked bare, though

Government-funded boffins in the USA say that "low-hanging fruit" plans to tackle climate change must be considered alongside CO2 reductions: in particular they say that emissions of black soot and shortlived greenhouse gases must be tackled in order to offset the warming caused by clean-air regulations.

Veerabhadran Ramanathan and Yangyang Xu, researchers at the Scripps Institution in San Diego, produce their results "using a synthesis of National Science Foundation (NSF)-funded research performed over the last 20 years", according to the NSF.

"They stress that carbon dioxide control alone is not enough," says an NSF statement released this week.

According to Ramanathan and Xu, there are other significant human-driven causes of warming besides CO2. In particular, one of these is clean-air law introduced in many industrial nations to put a stop to acid rain and related problems.

This is done by cutting down on emissions of sulphate aerosols, for instance by cleaning up the exhaust from coal-fired power stations. Unfortunately, sulphates in the atmosphere actually work against global warming, by reflecting heat away into space. Thus the clean-air rules mean that the warming tendency gets stronger.

And it gets worse (or better, depending on viewpoint). There's another kind of aerosol pollution, which warms rather than cooling - black soot, which has lately been rising in profile amid the climate debate to much acrimony. Many greens don't want it discussed, fearing that an emphasis on soot might detract from the push to cut CO2 emissions, but nonetheless scientists whose eco-credentials are impeccable have lately acknowledged that soot is a problem on the same level as carbon dioxide.

James Hansen of NASA, for instance, the world high priest of human-driven warming, lately stated that "black soot is probably responsible for as much as half" of the melting effect exerted by humans on the Himalayan glaciers, the planet's so-called "Third Pole". (In fact it is now admitted that the IPCC's suggestion that the glaciers would all be gone in decades was baseless. Even so, the admission by Hansen that soot is a big deal is very significant.)

The good thing about black soot is that like sulphates it disappears from the atmosphere quickly, washed away by rain, unlike CO2, which mainly hangs about until a carbon sink of some sort absorbs it. Thus cutting soot can have a big effect right away: and better still, cutting soot emissions is easy and cheap compared to cutting CO2. Ramanathan and Xu refer to this measure as "low-hanging fruit", in fact.

Soot comes primarily from inefficient burning of fuels, as in poorly adjusted diesel engines and primitive biomass stoves or cooking fires. Filtering diesel exhausts and handing out cleaner cooking gear to the developing world would cost almost nothing compared to major CO2 cuts, and would have big effects.

Some have suggested that the human race should simply press on and cut soot emissions, as binding agreement on carbon dioxide is proving elusive. This usually angers the harder-green lobby, who tend to see such a plan as merely postponing the problem.

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