Originally published January 12, 2012 at 10:06 PM | Page modified January 13, 2012 at 6:16 AM
Scientists say cut soot, methane: simple steps to cool globe
An international team of scientists says the key to slowing global warming in the short run is to reduce emissions of methane and soot.
The Washington Post
DONNA MCWILLIAM / AP
Capping landfills to trap methane, like this one in Ferris, Texas, might be too costly for poorer nations.
Simple, inexpensive measures to cut emissions of two common pollutants will slow global warming, save millions of lives and boost crop production around the world, a large international team of scientists reported Thursday.
The climate-change debate has centered on carbon dioxide, a gas that wafts in the atmosphere for decades, trapping heat. But scientists in recent years have pointed to two other, shorter-term pollutants — methane and soot, also known as black carbon — that also drive climate change.
Slashing emissions of these twin threats would be a "win-win-win" for climate, human health and agriculture, said NASA climate scientist Drew Shindell, who led the study published in the journal Science. "Even if you don't believe climate change is a problem, these things are worth doing."
Reducing methane and soot would slow global warming substantially — by almost 1 degree Fahrenheit — by midcentury, according to computer simulations run by the 24-member international team.
At the same time, the simulations show such actions would save 700,000 to 4.7 million lives annually, as better air quality would prevent lung and cardiovascular diseases.
Global crop yields also would increase, by 30 to 135 metric tons annually, as rice, corn, wheat and soybean plants would have an easier time absorbing nutrients from the air, according to the report.
"In the absence of a global carbon-dioxide agreement, it makes sense to move ahead on global efforts to reduce these other gases," said Joyce Penner, a University of Michigan scientist who has studied the climate impacts of soot but was not involved in the new research.
Previous studies have noted benefits of reducing methane and soot, but the new study looked at the specific impact of about 400 measures policymakers could take. Of those, 14 interventions — such as eliminating wood-burning stoves, dampening emissions from diesel vehicles and capturing methane released from coal mines — would offer big benefits.
"They're all things we know how to do, and have done; we just haven't done them worldwide," said Shindell, who works at the NASA Goddard Institute for Space Studies in New York.
About 3 billion people in the developing world rely on stoves that burn wood, dung and other fuels that throw off soot. Cleaner-burning stoves would help reduce short-term global warming while quickly improving local air quality. Soot particles fall out of the air in less than a week.
But persuading people to switch to cleaner-burning stoves is "easier said than done," said Elizabeth Ransom, a spokeswoman for University Research. The group recently doled out $1.3 million in grants to three groups studying how to persuade people in Uganda and India to adopt cleaner-burning stoves, as some projects to introduce modern stoves "just didn't take off."
Many measures would be inexpensive, Shindell said. For instance, farmers in the developing world often burn agricultural waste, but plowing it under instead would cost almost nothing.
Other interventions, such as capping landfills to trap methane, would be more costly, presenting a barrier to poorer nations.
But several experts said that, in the absence of a global treaty to reduce carbon-dioxide emissions, the new study should spur national governments to smaller actions.
"This great news could not come at a better time for climate protection," said Durwood Zaelke, president of the Institute of Governance and Sustainable Development.
Zaelke said the proposed measures are particularly important for the most vulnerable regions, such as the Arctic, which has warmed twice as quickly as the rest of the world over the past half-century, and the Himalayas, which have warmed three times as fast.
Shindell and Brooks Yeager, executive vice president for policy for the advocacy group Clean Air-Cool Planet, said reducing methane and soot, while laudable as a short-term strategy for dampening global warming, would not solve the long-term problem.
"I think it's a little dangerous to think you can do this instead of reducing carbon dioxide," Yaeger said. "If you don't reduce carbon dioxide, the benefits of reducing these (pollutants) will recede into the background and be overwhelmed by carbon."
