Photo: Dimitar Dilkoff
Scientists have found that the dense plumes of wildfire smoke in recent years are contributing to the warming of the Arctic through “brown carbon” in the smoke drifting north and attracting heat to the region.
They added that the increasing number of wildfires explains why heat dissipates faster in the Arctic than in the rest of the world, leading to concerns about whether this effect will increase.
Smoke resulting from the wildfires in Australia, Portugal, Siberia, and the US has changed the color of the skies over the past ten years, affecting human health. The carbon released by the burning has also pushed emissions to record levels.
The burning is contributing to the loss of sea ice in the Arctic, scientists add.
The second-largest contributor to global warming, the “black carbon,” has been well-documented, alongside its impact on the Arctic. Black carbon is the particles emitted from diesel engines, coal burning, cooking stoves, and other sources. They absorb sunlight and turn it into heat.
But little is known for brown carbon, which mainly comes from the burning of trees and vegetation and is also created from fossil fuels to some degree. Climate models have either ignored or underestimated the warming effect of this less dense substance.
Scientists traveled around the Arctic ocean on the Chinese icebreaker, Xue Long, in 2017 to learn more about these impacts, wherein they found that brown carbon, previously estimated to be causing just 3% of the warming effect, is causing more damage to the region than they thought.
“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% of that of black carbon,” says senior author Pingqing Fu, an atmospheric chemist at Tianjin University in China.
The study says the main source of this brown material is wildfires, the study says, and it is contributing twice as much to the warming effect in the Arctic than what came from fossil fuels.
Black carbon plays the major role in this, but scientists say that brown carbon is also exceptionally warming the Arctic in the last few decades. It has been warming at three times the rate of the rest of the planet over the last 50 years, and the main factor causing this is what’s termed as the Arctic amplification. Ice and snow on the surface of Arctic waters normally reflect more sunlight back to space, but with Arctic amplification, the darker waters absorb much more heat as the ice melts even quicker.
But the new study finds that as wildfires in mid and northern latitudes increase, the brown carbon from this source has a growing impact on the Arctic, which is considered a feedback loop: as the warmer world experiences more fires, there will be less ice and more heat.
“The increase in brown carbon aerosols will lead to global or regional warming, which increases the probability and frequency of wildfires,” says Dr. Fu, explaining how the feedback loop works.
“Increased wildfire events will emit more brown carbon aerosols, further heating the earth, thus making wildfires more frequent.”
Wildfires are expected to increase by up to 50% by the middle of the century, a recent UN study says, so the authors of the study believe that the trend of brown carbon will increase.
The scientists also add that this shows how important managing vegetation fires is. It is not just about saving lives and limiting the damage, but it also has a role in limiting the warming of the plant.
The study has been published in One Earth.