Climate change: Wildfire smoke linked to Arctic melting

Dense plumes of wildfire smoke seen in recent years are contributing to Arctic warming, scientists say.

Their study says that “brown carbon” particles in the smoke drift north and draw heat to the polar region.

The authors believe that the increasing number of wildfires helps explain why the Arctic is warming faster than the rest of the planet.

They are concerned that this effect is likely to increase.

Over the past decade, smoke from wildfires in Australia, Portugal, Siberia, and the US has changed the color of skies. The smoke has affected human health and the amount of carbon released by burning has helped drive emissions to record levels.

But now scientists say all this burning has contributed to another serious problem: the loss of sea ice in the Arctic.

Researchers have long known about “black carbon,” the soot particles emitted from diesel engines, burning coal, cooking stoves and other sources.

These aerosols, which absorb sunlight and convert it into heat, are known to be the second largest contributor to global warming.

The impact of these particles in the Arctic and in the clouds has been well documented.

However, the same cannot be said for brown carbon, which comes primarily from the burning of trees and vegetation, but is also created, to a lesser degree, from fossil fuels. The warming effect of this less dense substance has been ignored or estimated with great uncertainty in climate models.

To develop a better understanding of the impacts, researchers traveled around the Arctic Ocean on the Chinese icebreaker, Xue Long, in 2017.

While some previous estimates had shown that brown carbon was responsible for just 3% of the warming effect compared to black carbon, the scientists found that it is doing much more damage in the region.

“To our surprise, observational analyzes and numerical simulations show that the warming effect of brown carbon aerosols over the Arctic is up to about 30% that of black carbon,” says lead author Pingqing Fu, an atmospheric chemist at Tianjin University in China.

The study found that wildfires were the main source of this brown material, contributing twice as much to the warming effect of brown carbon in the Arctic as fossil fuels.

The authors believe that while black soot has played the main role, brown carbon has contributed to the exceptional warming that has been felt in the Arctic region in recent decades.

Over the last 50 years, the frozen north has been warming at three times the rate of the rest of the planet.

The main factor driving this difference is what is called arctic amplification.

What happens is that the ice and snow on the surface of Arctic waters normally reflect most of the sunlight back into space, but as the ice melts, the darker waters absorb much more heat, which in turn melts the ice even faster.

But as wildfires in the mid- and northern latitudes have increased as the world warms, this new study finds that brown carbon from this source is having a growing impact in the Arctic.

This is what scientists describe as a feedback loop, where the warmer world causes more fires, which in turn leads to less ice and more heat.

“Increased brown carbon aerosols will lead to global or regional warming, which increases the probability and frequency of wildfires,” says Dr Fu, explaining the way the feedback loop works.

“Increased wildfire events will emit more brown carbon aerosols, further warming the land, making wildfires more frequent.”

As a recent UN study has shown, wildfires are likely to increase by up to 50% by the middle of this century, so the authors believe this brown carbon trend is likely to increase.

The scientists involved in the study say their work shows that the importance of controlling wildfires is not just about saving lives and limiting the damage caused by burning, but also has a role in limiting global warming.

The study has been published in the journal One Earth.

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