Report: Soot 2nd Biggest Contributor to Global Warming

Soot from diesel engines and coal smoke was a main culprit in the recent Beijing smog crisis.

Now a new report says soot is also a much bigger contributor to global warming than had been thought.

Host Marco Werman gets the latest on soot from The World’s environment Editor Peter Thomson.

MARCO WERMAN: Remember the blanket of smog that smothered Beijing a few days ago?

It caused a massive public health crisis, not to mention a wave of anger across the city.

A big part of the problem was soot from diesel exhaust and coal smoke.

And the nasty effects of soot aren’t just a problem for the residents of Beijing.

Soot also is a huge contributor to global warming.

So says a new scientific study that came out yesterday.

The World’s environment editor Peter Thomson is here now. So, a lot of people have been suffering the health effects of soot for decades, Peter, all the way back to the Victorian era and Charles Dickens in England. Now the whole planet is feeling effects as well. Explain this.

PETER THOMSON: Yeah, well, scientists have known for a long time that soot has a powerful warming effect on the atmosphere. Some of that’s fairly simple physics. Soot particles are black—in fact another term scientists use for soot is “black carbon”—and it can have a lot of surface area. So it just absorbs a lot of light and heat that might otherwise just be radiated back into space. But there’s been a lot of uncertainty over just how much soot from things like diesel engines and the burning of things like wood and coal contributes to climate change.

Well, now a group of nearly 30 scientists from around the world has done an exhaustive analysis—pardon the pun but it’s actually an apt description of a report that runs 230 pages in the latest issue of the Journal of Geophysical Research. So they’ve done this exhaustive analysis of sources and impacts of soot and they’ve found that at least in the short run, soot particles are the second-biggest source of global warming today.

WERMAN: Wow!

THOMSON: Number two in impact after carbon dioxide, and twice as big an impact as most climate scientists had figured before.

WERMAN: Double the impact—that’s shocking!

THOMSON: Well, yes and no. Like I said, this is something that scientists have been concerned about for a long time, but they’ve had a hard time pinning down the details because the science of soot and what produces it is extremely complex. And I should add that this study still leaves a lot of those questions unanswered. But having said that, at least one prominent scientist had ballparked soot as the number two contributor to global warming as far back as 2008. A lot of folks said then that his study was way too limited to be useful, but this study clearly vindicates that one in a big way.

WERMAN: So now that we know this, Peter, how does it help us? I mean, what can we do with the information?

THOMSON: Well, it tells us a couple of things. One is that one of the biggest contributors to global warming, at least in the short term, is relatively easy to deal with. Soot, like you said, is sort of the classic industrial age pollution—you mentioned Victorian England, where smog from factories is sort of the iconic image of the industrial revolution. It comes from burning coal, and diesel fuel. Another big source is wood smoke from cook stoves and burning of forests in the tropics and elsewhere. And we know how to stop these things—like they say, “we have the technology.” I mean there’s clear evidence of this in the fact that soot emissions are way down in the western world but still very high in developing countries. The difference is technology. So compared to the challenges of cutting carbon dioxide and methane pollution, which we’re clearly having a very hard time dealing with, getting rid of most of the world’s sources of soot would be a fairly simple fix. One of the authors of this study called it a “no-brainer.” And it could reduce the rate of warming of the atmosphere at least a bit and buy us some time while we deal with those bigger challenges.

WERMAN: And of course there’d be a big public health benefit I would imagine.

THOMSON: Yeah, that’s the second thing, and another reason that study author called getting rid of it a “no-brainer.” It’s kind of an environmental two-fer. In fact that scientist I mentioned earlier, who did the 2008 study on the warming effects of soot—his name is V. Ramanathan and our science correspondent Rhitu Chatterjee reported a couple of years ago on his efforts to introduce new cookstoves to rural communities in India as a way to hit those two birds with one stone—to cut down on respiratory diseases locally but also really reduce global soot pollution.

So this study really drives home the dual benefits of getting rid of sources of soot.

WERMAN: Alright, The World’s environment editor Peter Thomson. Thank you.

THOMSON: You’re welcome Marco.

WERMAN: We have a link to that new study on soot and climate—all 232 pages of it—on the web. You can also hear Rhitu Chatterjee’s story on soot and cookstoves in India. That’s at the world dot org.