What's The Effect Of So Many Wildfires On Global Warming?

Sep 15, 2017

The tricky part of installing such highly calibrated instruments is keeping them that way over miles of rough gravel roads as the mobile lab chases the fires.
Credit Kate Foster

It’s another day of hazy skies at the airport outside Laramie. A team of atmospheric scientists from the University of Wyoming are busy unloading from a recent trip to Montana to study the fires where all this smoke originated. For weeks, skies across the west have been filled with this billowing white smoke. Many scientists agree that the warming climate is causing more extreme fires, but it’s hazy whether all that smoke is generating even more global warming as part of a self-perpetuating cycle. Scientists like these guys are scrambling to find out.

Researcher Kate Foster says her job on the recent trip to Montana was to collect samples of smoke particles in the air. She points up at the roof of the large van where some metal scaffolding juts out in front.

“So this mobile lab has an inlet on the mast out in front of it and that inlet comes in through the roof,” she says. “And then we build our own plumbing to disperse the airflow to all the different instruments.”

And, wow, does this van hold a lot of instruments. Six to be exact, all studying the smoke as the plumbing sucks it in.

“Some people are only able to go out with one of these type of instruments and make a measurement. And so we’re really fortunate that we have this amazing suite of instruments with which we can kind of build a more complete picture.”

A picture of two different kinds of emissions: black and brown carbon. Everybody knows black carbon. It’s soot that spews from cars and power plants. Its dark color is known to be the third largest cause of atmospheric warming after carbon dioxide and methane. Brown carbon, though, is light colored. Think of it as white smoke, like when you burn wet wood in a campfire. It’s not as efficiently burned up as soot.

“Right now, climate models don’t really include brown carbon,” says UW atmospheric science professor Shane Murphy. “Right now there’s a lot of uncertainty on how important it is, how long does it last, does it evaporate, does it get aged out as the smoke goes downwind? So we’re trying to figure those things out.”

UW Atmospheric Professor Shane Murphy, Researcher Rudra Pokhrel, Engineer Mathew Burkhart and Technician Ben Heesen.
Credit Melodie Edwards

Murphy says, they’re doing that by driving the mobile lab around collecting smoke samples from different distances from the fire to find out if brown carbon becomes more absorbent and warming over time. Technically, brown carbon is actually just black carbon in disguise. It’s coated in organics that break down as it blows away. The question is whether it becomes darker and starts heating things up. That’s what the mobile lab’s instruments are here for.  

Murphy invites me into the mobile lab for a tour.

“This is our mass spectrometer,” he says, pointing at an inconspicuous looking instrument that doesn’t live up to its imposing name. “These measure the particle size distributions so we heat up some of the particles to try to burn off that brown carbon and so we measure it before and after we burn it up.”

If these machines sound a little like something from a sci-fi flick, they kind of are. Another instrument, a photoacoustic, shoots a laser at the smoke to check how much light the brown carbon absorbs. Absorbent particles warm the climate. So if the laser hits something absorbent, it sings.

“Sings?” I ask.

Murphy looks at his crew. “What tone is that, it’s like…”

The lab’s engineer, Matt Burkhart, whistles a high-pitched note, imitating the 1350 hertz tuning fork sound the particles make when zapped by the laser. Burkhart says, this machine will help pinpoint how far away from a fire brown carbon starts become warming instead of cooling.

The mobile lab collects smoke particles from different distances from wildfires.
Credit Melodie Edwards

Today, though, the team is loading all these instruments in an airplane to also find out how it acts at different heights.

“This is a research aircraft taking off for a test flight,” yells Professor Murphy over the plane’s noise.

It’s a test flight for a NOAA study. Meanwhile, Murphy and his team are working on two different studies, one for the Environmental Protection Agency, another for the National Science Foundation.

“This is the only place in the entire United States where you can come, make measurements on the ground, make measurements in the air,” says Murphy.

He says all this research is really ramping up because as the climate warms, there’s going to be lots more wildfires and everyone recognizes there’s only so much you can do to control nature. It’s much easier to control car and methane emissions.

“Unlike the other sources you control, [wildfires are] probably going to increase in the future. It’s not going to go away and it might be getting worse.”

Right, this minute, 137 fires are burning around the country, a huge number this late in September. And it’s puffing a lot of brown carbon up into the atmosphere. Murphy says the common theory is that fires have zero warming effect on the climate because it’s light in color and reflects light, unlike black carbon that absorbs light, warming things up.

“If it turns out forest fires are quite cooling, right now you might think that’s good. But in some ways that’s not good because it means they’re masking some other warming from human sources,” Murphy says. “And so if we cut down on forest fires, we might actually see more warming.”

But Murphy says, the idea that brown carbon cools has never been proven scientifically. And that’s why scientists around the west including those at UW are joining forces to solve the mystery of brown carbon’s role in climate change, once and for all. Over the next few months, these guys will be very busy digesting all the data they’ve collected about white smoke during this very volatile wildfire season.