July 10, 2013
Wildfire Emissions Plays Greater Role In Climate Change Than Previously Believed
redOrbit Staff & Wire Reports - Your Universe Online
Emissions produced as a result of wildfires could be playing a greater role in global warming than experts had previously believed, according to new research published Tuesday in the journal Nature Communications.
Climate scientists had long known that wildfires produce a mixture of carbon-containing particles. However, measurements taken by researchers from the Los Alamos National Laboratory (LANL) and Michigan Technological University during the massive 2011 Las Conchas fire in New Mexico revealed that those carbonaceous aerosols are actually quite different from those features in current computer simulations.
As a result, the results of those computer climate models could be inaccurate. Based on their findings, the researchers believe that scientists need to establish a framework to include a realistic representation of these carbon-containing particles in climate models. Furthermore, they suggest that wildfire emissions could contribute far more to global warming trends than current estimates suggest.
"We've found that substances resembling tar balls dominate, and even the soot is coated by organics that focus sunlight. Both components can potentially increase climate warming by increased light absorption," LANL senior laboratory scientist Manvendra Dubey said in a statement.
"The fact that we are experiencing more fires and that climate change may increase fire frequency underscores the need to include these specialized particles in the computer models, and our results show how this can be done," added Dubey, who worked on the study along with Allison Aiken and Kyle Gorkowski of LANL and Claudio Mazzoleni and Swarup China of Michigan Tech.
Scientists currently believe that fire-driven particles contain soot or black carbon that absorbs sunlight and warms the climate, and organic carbon or smoke that reflects sunlight to cool the climate. However, after analyzing the morphology and composition of specific aerosols emitted by the Las Conchas fire, Dubey and his colleagues discovered that those two opposing components aren't present in equal quantities.
The LANL/Michigan Tech team established a comprehensive aerosol sampling system to monitor the smoke from the fire for a period of more than 10 days. They used field-emission scanning electron microscopy and energy dispersive X-ray spectroscopy to analyze the aerosol samples, and found that the spherical carbonaceous particles known as tar balls were actually 10 times more abundant than soot particles.
"Furthermore, the bare soot particles, which are composite porous fractal structures made of tiny spherical carbon, are modified significantly by the organics emitted by the fire," officials from the laboratory said. "About 96 percent of the soot from the fire is coated by other organics substances, with 50 percent being totally coated. "
In addition, the US Department of Energy Office of Science-funded study found that the complexity of the soot could be categorized into four different morphological structures: embedded, partly coated, with inclusions, and bare. Those discoveries could be extremely important for climate, according to Dubey.
"Most climate assessment models treat fire emissions as a mixture of pure soot and organic carbon aerosols that offset the respective warming and cooling effects of one another on climate," he explained. "However Las Conchas results show that tar balls exceed soot by a factor of 10 and the soot gets coated by organics in fire emissions, each resulting in more of a warming effect than is currently assumed."
"Tar balls can absorb sunlight at shorter blue and ultraviolet wavelengths (also called brown carbon due to the color) and can cause substantial warming," the LANL researcher added. "Furthermore, organic coatings on soot act like lenses that focus sunlight, amplifying the absorption and warming by soot by a factor of 2 or more. This has a huge impact on how they should be treated in computer models."