Oct 19 2009

Global Warming's Hidden Culprits

Posted by: Jonathan Marshall

Good news for a change from the scientists who study global warming: the Earth's thermostat can be held below dangerously high levels over the next few decades if we take collective action against highly potent but widely ignored agents of warming other than CO2.

Cutting harmful hydrofluorocarbons (HFCs) used in refrigeration, black carbon soot from dirty diesel engines and ovens, ozone smog and methane "can buy us about 40 years before we approach the dangerous threshold of 2°C (3.6°F) warming," said Veerabhadran Ramanathan, a leading expert on climate and atmospheric sciences at Scripps Institution of Oceanography at UC San Diego and co-author of a paper published last week in Proceedings of the National Academy of Sciences.

Reining in these pollutants shouldn't take a superhuman effort, the authors note. Substitutes already exist for HFCs--which are 350 times more potent than CO2--and could be promoted by expanded enforcement of the Montreal Protocol treaty that was adopted in the late 1980s to prevent destruction of the ozone layer. EPA today proposed phasing out HFCs in automobile air conditioners.

And black carbon soot, which absorbs sunlight and causes melting of glaciers and Arctic ice, could quickly be reduced by installing filters on diesel vehicles and replacing wood- or dung-burning stoves with solar cookstoves.

Meanwhile, more than three trillion cubic feet of methane escape into the atmosphere every year, mostly in Russia and the United States, from leaky natural gas wells, pipelines and tanks. Methane is about 25 times more potent than carbon dioxide as a heat-trapping gas.

Reversing the Bush administration's hands-off policy, the Obama administration may require oil and gas companies to begin reporting their carbon emissions, the first step toward mandating steps to seal such leaks. The EPA estimates that ordinary methane leaks at gas wells trap as much heat as the CO2 emitted by 8 million cars.

Engineers at BP have discovered that investing in measures to catch methane emissions at their wells saves three times as much as it costs, reports The New York Times.

"This for me is an absolute no-brainer, even more so than putting in those compact fluorescent bulbs in your house," said Al Armendariz, an engineer at Southern Methodist University.

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