Photo: Dimitar Dilkoff
Scientists say that the dense plumes of wildfire smoke seen in recent years contribute to the warming of the Arctic. According to their study, particles of “brown carbon” in the smoke are drifting north and attracting heat to the Arctic region.
The scientists added that the growing number of wildfires could explain why heat dissipates faster in the Arctic than the rest of the planet. They expressed concerns that this effect will likely increase.
Smoke from raging wildfires in Australia, Portugal, Siberia, and the US has changed the color of the skies over the past decade. This has affected human health, and the carbon released by the burning has pushed emissions to record levels.
Now scientists add that the burning is contributing to the loss of sea ice in the Arctic.
“Black carbon,” the sooty particles that are emitted from diesel engines, burning coal, cooking stoves, and other related sources, and that which absorb sunlight and turn it into heat, are known to be the second largest contributor to global warming and their impact on the Arctic has been well-documented.
But the case is different for brown carbon, which primarily comes from the burning of trees and vegetation and is also created from fossil fuels to a lesser degree. The warming effect of this less dense substance has been either ignored or underestimated in climate models.
To learn more about these impacts, scientists traveled around the Arctic ocean on the Chinese icebreaker, Xue Long, in 2017. They found that brown carbon is doing more damage to the region than the previous estimates of brown carbon causing just 3% of the warming effect than black carbon.
“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.
Wildfires were the main source of this brown material, according to the study, which is contributing twice as much to the warming effect in the Arctic than what was coming from fossil fuels.
While black carbon plays the major role, scientists believed that brown carbon is exceptionally warming the Arctic in recent decades.
The Arctic 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 difference is what is called the Arctic amplification, where ice and snow on the surface of the Arctic waters normally reflect more sunlight back to space, but as the ice melts, the darker waters absorb much more heat and melts ice even quicker.
But the new study finds that brown carbon from this source is having a rising impact on the Arctic even as wildfires in mid and northern latitudes have increased.
This is considered a feedback loop, as the warmer world causes more fires, leading to 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 likely 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 their work shows how important managing vegetation fires is, and it is not just about saving lives and limiting the damage done by burning, but it also has a role in limiting the warming of the plant.
The study has been published in One Earth.