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Cutting Soot and Methane Alone Won't Slow Down Global Warming

New research shows that the reducing short-lived climate pollutants will have minimal climate benefits.
Photo: La Melodie/Flickr

Over the past several years a number of studies have touted the potential advantages in reducing global warming by reducing short-lived climate pollutants such as black carbon soot and methane.

Short-lived as compared to the main climate pollutant, carbon dioxide, that is. The prime advantage is that if we cut back on black carbon (primarily emitted from older cookstoves widely used in poorer nations and from older diesel engines) and methane (from cutting back on leakage from natural gas production and distribution, for example) we could potentially dial back increases in global temperatureby up to 0.5°C by 2050.

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That may not sound like much, but it is when you consider than it could mean that we delay crossing the critical 2°C temperature rise threshold, after which all sorts of highly disruptive climate-related things happen with all sorts of damaging and in some case crippling effects on civilization as we know it.

Well, a new study suggests that the hope of soot and methane being easy sources of temperature reduction is misguided.

Writing in the latest edition of the Proceedings of the National Academy of Sciencesscientists from the Joint Global Climate Change Research Institute say that cutting soot and methane alone will do very little to reduce warming by mid-century.

Rather than the 0.5°C reduction in temperature rise resulting from reducing this pollutants, we are more likely to only cut warming by 0.16°C by 2050—and that's taking a middle figure, with cutting these pollutants potentially only reducing emission by 0.04°C (next to nothing) or perhaps as much as 0.35°C (far better).

In either case, the scientists say,

Focusing on soot and methane may be worth targeting for health reasons, as previous studies have identified substantial health benefits from reducing those emissions. To stabilize the global climate, however, the focus needs to be on carbon dioxide and other greenhouse gases. Concentrating on soot and methane alone is not likely to offer much of a shortcut.

To be fair, I'm not sure any of the previous studies focusing on the effects of cutting soot or methane ever said they would be a shortcut to cutting carbon dioxide, only that doing so would buy human civilization some time in making deep carbon dioxide cuts. And anyone who ever said that making cuts in soot and methane alone would be sufficient is just inaccurate.

Nevertheless, from a policy perspective, even if cutting soot and methane really won't buy us any time, it's a very important thing to be aware of. As these scientists say, there are very important health benefits in reducing the sources of black carbon pollution, as well as potential benefits in reducing the amount that glaciers retreat in the Himalayas. But in terms of reducing warming we're back to focusing our efforts on reducing carbon—as politically unpalatable as that may be in nearly every nation on Earth.