Buying some time on climate change with methane and soot

When it comes to climate change, fossil fuels nab most of the headlines. But a new study suggests the world should also pay closer attention to smaller steps to curb soot and methane. In fact, those measures could make all the difference in whether the world makes or misses its climate targets.

The paper, appearing in the journal Science, focused on 14 fairly straightforward steps to curb soot and methane emissions using existing, proven technologies. This included measures like patching up leaks in natural-gas pipelines and promoting cleaner cookstoves in Africa and Asia. What the researchers discovered was that these measures would have a shockingly large impact almost immediately, reducing global warming by about 0.5ºC (0.9ºF) below current projections in 2050. As a companion chart from NASA shows, that could buy us invaluable time in preventing the world from heating up more than 2ºC:

The green line shows the temperature increase we can expect if emissions continue rising at their usual pace. The yellow line shows warming if all of the methane- and soot-reduction measures were adopted.

Now, in terms of warming the planet, carbon dioxide — the byproduct of burning coal, oil, and natural gas — is still the most important man-made driver. But methane and black carbon (soot) also play a large, if less-appreciated role. Soot particles, for instance, absorb radiation from the sun and can hasten the melting of snow and ice cover when they fall to the ground. Some scientists think that soot is accelerating ice melt in the Arctic. What’s more, because methane and soot cycle out of the air fairly rapidly (soot can wash out in a matter of days), clamping down on these pollutants would have an immediate impact.

Here’s a list of the methods that the Science authors recommend for curbing methane: “capturing gas currently escaping from coal mines and oil- and gas-producing facilities; reducing leakage from long-distance pipelines; preventing emissions from landfills; updating wastewater treatment plants; draining rice paddies more often; and limiting emissions from manure on farms.” And here are the anti-soot strategies: “installing more filters on diesel vehicles; taking the worst-polluting vehicles off the road; upgrading family cookstoves with cleaner-burning models; building more efficient brick kilns, boilers and coke ovens; and banning the routine burning of agricultural lands now common in many parts of the tropics.”

As a side benefit, the authors point out, curbing soot and methane could have considerable side benefits. The measures listed could prevent 700,000 to 4.7 million premature deaths and also boost crop yields, thanks largely to reductions in ground-level ozone, which is formed when methane interacts with other gases in the air. (Scientists also suspect that soot pollution is disrupting the Asian monsoon cycle, which could have additional effects on farm production.)

What’s more, while these measures aren’t a substitute for cutting fossil-fuel emissions, they might be more politically palatable in the near term. Sen. James Inhofe (R-Okla.), for instance, is famous for his climate denialism, but he’s also concerned with the health and air-pollution effects of soot in the developing world. (Of course, as my colleagues Juliet Eilperin and Brian Vastag point out, not all of these soot-cutting strategies are a snap — pilot programs to promote clean stoves in Uganda and India, for instance, have had trouble getting off the ground.)

In any case, this is a reminder that the ongoing U.N. talks over greenhouse-gas emissions aren’t the only path for averting climate change. Right now, assuming all countries follow their stated pledges to cut carbon pollution, the world is still on track to warm some 3.5ºC above pre-industrial levels by 2100, a level that many scientists consider dangerous. But as this handy infographic from New Scientist lays out, there are all sorts of side strategies — from preventing deforestation to regulating aviation and shipping emissions — that could help close the “emissions gap” by 2020 and buy the world some time. Methane and soot turn out to be a very large piece of that puzzle.


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