August 30, 2013
New Wildfire Insights May Change Climate Predictions
Brett Smith for redOrbit.com - Your Universe Online
According to a new study from researchers at Michigan Technological University, forest fires emit massive quantities of two different kinds of particles – soot and tar balls. These particles remain in the atmosphere and should be taken into account when creating climate change models, the researchers said.
In the study, which was publish in Nature Communications, scientists examined two types of particles taken from the 2011 Las Conchas fire in New Mexico: soot – similar to diesel exhaust, and tar balls – small, round organic blobs that are abundant during a biomass fire. The team determined that tar balls made up 80 percent of the particles from the Las Conchas fire.
Using a field emission scanning electron microscope, the team was able to enhance the differences among the various particles. Under the microscope, tar balls were seen as either “dark” or “bright.” The two types have a differing impact on climate change since they absorb and scatter radiation from the sun differently. The team was able to identify four categories of soot, ranging from bare to heavily-coated. Each type of soot particle has different optical properties.
To better understand the particles’ composition and properties, the scientists heated tar balls and soot in a special chamber, essentially baking off their exterior.
The scientists said that determining how these particles affect climate would mean understanding much more than how much heat they can retain. For instance, water vapor condenses more easily on oxidized particles to eventually form clouds. The researchers added that they are not yet able to determine what role these particles play with respect to climate.
“We don’t have an answer to that,” said study author Claudio Mazzoleni, an associate professor of physics at Michigan Technological University. “The particles might be warming in and of themselves, but if they don’t let solar radiation come down through the atmosphere, they could cool the surface. They may have strong effects, but at this point, it’s not wise to say what.”
“However, our study does provide modelers new insights on the smoke particle properties, and accounting for these properties in models might provide an answer to that question,” he added.
“The big thing we learned is that we should not forget about tar balls in climate models,” said co-author Swarup China, a graduate student at MTU, “especially since those models are predicting more and more wildfires.”
The study findings are being published just as California’s Rim fire has been declared the fifth-largest wildfire in state history. According to reports, the fire has grown to almost 200,000 acres.
Some of the acreage consumed in the blaze can be attributed to backfire operations by firefighters. The technique involves lighting low-intensity fires to rob the main fire of potential fuel.
“The fire is not having erratic growth like it was before,” reported Alison Hesterly, a Rim fire information officer. “And the forward spread of the fire is slowing, which is a good thing.”