Wildfires Release Powerful Organic Particles that Contribute to Climate Warming

Scientists have discovered that wildfires have a more significant warming impact than previously estimated by climate researchers. The study emphasizes the importance of ‘dark brown carbon,’ a previously unidentified group of particles released during wildfire smoke. This finding underlines the necessity for immediate revisions to climate models and updated strategies to address the evolving environmental conditions.

The ongoing impact of Canadian wildfire smoke on vast areas of the United States is leading to poor air quality and adverse health effects for millions of Americans, making them increasingly aware of the consequences of prolonged fire seasons and a changing climate. New research conducted by scientists at Washington University in St. Louis reveals that wildfires may have even more significant climate effects than previously believed.

Research Uncovers “Dark Brown Carbon” in Wildfire Smoke, Prompting Updates to Climate Models

A research study led by Rajan Chakrabarty, an associate professor in the Department of Energy, Environmental & Chemical Engineering at the McKelvey School of Engineering, and published in Nature Geoscience on August 7, focuses on investigating a previously unknown class of particles emitted during wildfire smoke, known as “dark brown carbon.” This discovery has highlighted the immediate need to update climate models and strategies to adapt to the changing environmental conditions.

To comprehensively understand the composition of wildfire smoke plumes, Chakrabarty’s team conducted a 45-day study at various wildfire locations in the western United States. They collected samples of gaseous smoke and aerosol species and analyzed their chemical and optical properties. This research was part of the Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) field campaign, jointly led by the National Aeronautics and Space Administration and the National Oceanic and Atmospheric Administration.

Wildfire smoke

Traditionally, it was believed that dark wildfire smoke mainly contained black carbon soot, which absorbs solar radiation, while lighter plumes were thought to consist mostly of organic carbon that scatters sunlight, offsetting the warming effect of soot. However, the researchers found that the situation is more complex, as they observed a significantly strong light absorber in the plumes that was not black carbon but contributed to more than half of the total absorption.

To delve into the properties of this unknown material, Chakrabarty collaborated with Rohan Mishra, an associate professor of mechanical engineering and materials science. Using a sophisticated electron microscope housed at the Center for Nanophase Materials Sciences, a U.S. Department of Energy facility at Oak Ridge National Laboratory (ORNL), Arashdeep Thind, who earned a doctorate in materials science and also engineering while working in Mishra’s lab in 2021, measured the optical properties of individual particles from the smoke samples collected by Chakrabarty’s team.

Atomic structure of the dark brown particles

Mishra stated that they noticed peculiar characteristics in the composition, structure, and absorption properties of this material. By examining the local atomic structure of the dark brown particles, which were only a few tens of nanometers in size, and simultaneously measuring their optical properties using the electron microscope at ORNL, they discovered that these particles are similar to black carbon and likely form similarly to soot in the high-temperature flames along the leading edges of wildfires.

Mishra and Chakrabarty’s research revealed that dark brown carbon absorbs slightly less light than black carbon per particle but is four times more abundant in wildfire plumes. This suggests that these hidden dark brown carbon particles might contribute significantly more to climate warming than previously recognized.

Furthermore, the researchers found that these particles absorb light across a wide range of wavelengths, covering the entire visible spectrum from ultraviolet to near-infrared. Surprisingly, this potent brown carbon is resistant to sunlight-driven photochemical bleaching, which is typically responsible for reducing the absorptivity of light-absorbing organic aerosols in the atmosphere.

The implications of these findings are profound. With global wildfire occurrences predicted to increase in the coming decades, the role of dark brown carbon produced in fires will have an even greater impact.

Chakrabarty and Mishra emphasize the importance of multidisciplinary collaboration to update existing climate models and account for the unexpected effects of brown carbon in wildfire smoke. Failing to make this crucial adjustment runs the risk of underestimating the global warming effects of wildfires and downplaying the urgency of climate change mitigation efforts.

Read the original article on: Science Daily

Read more: How Smoke Produced From Large Wildfires Can Affect Local Weather And Make Fires Worse