Brown carbon released from wildfires is warming the Arctic

In a new study published in the journal One Earth, experts have identified a positive feedback loop in the northern hemisphere in which brown carbon released by burning biomass is accelerating warming in the Arctic. The researchers warn that this could lead to even more wildfires in the future. 

The year of 2021 saw land across the world destroyed from a record breaking wildfire season. Last month, a UN report warned that wildfires are on track to increase by 50 percent over the next couple of decades. Wildfires can be devastating, destroying homes, displacing families, and killing plant and animal life

During wildfires, vast plumes of smoke containing brown carbon particles are suspended in the air. Beyond the human health impacts of brown smoke, experts have long suspected that it contributes to global warming. 

In 2017, scientists boarded a Chinese icebreaker vessel Xue Long in the Arctic Ocean to examine the aerosols that could be polluting the pristine Arctic air. The researchers considered how brown carbon released by wildfires affects the climate. This was compared to denser black carbon from fossil fuels, the second most powerful warming agent after carbon dioxide. The study revealed that brown carbon contributes more to global warming than previously estimated. 

“To our surprise, observational analyses and numerical simulations show that the warming effect of brown carbon aerosols over the Arctic is up to about 30 percent of that of black carbon,” said study senior author Pingqing Fu, an atmospheric chemist at Tianjin University.

Over the last 50 years, the Arctic has been warming three times faster than the rest of the planet. The study found that brown carbon from burning biomass was responsible for twice as much warming as carbon from fossil fuels, identifying that wildfires are driving this discrepancy. 

Brown carbon warms the planet by absorbing solar radiation and warming temperatures result in a rise of wildfires. This leads to a positive feedback loop. 

“The increase in brown carbon aerosols will lead to global or regional warming, which increases the probability and frequency of wildfires,” said Fu. “Increased wildfire events will emit more brown carbon aerosols, further heating the earth, thus making wildfires more frequent.”

In the future, the researchers plan to dive deeper and investigate the effects of other sources of carbon released by wildfires. Specifically, the research team plans to analyze bioaerosols, which originate from plants and animals and can contain living organisms, including pathogens. 

The researchers are hopeful that decision makers remain focused on mitigating wildfires. “Our findings highlight just how important it is to control wildfires,” said Fu. The study was supported by the National Natural Science Foundation of China.

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By Katherine Bucko, Earth.com Staff Writer