Wildfires raging in the Arctic Circle smashed last year's records for carbon dioxide emissions, according to scientists at the Copernicus Atmosphere Monitoring Service (CAMS).

Using CAMS' Global Fire Assimilation System (GFAS) data, scientists estimated that CO2 emissions from fires in the Arctic Circle have increased by more than a third, compared to 2019, with 244 megatonnes of carbon produced from Jan. 1 to Au. 31. By comparison, 181 megatonnes of carbon were produced for the whole of 2019.

Most of the increased wildfire activity took place in Russia's Sakha Republic, scientists said, ravaging millions of acres of land, and causing a spike in CO2 emissions.

"Last summer we discovered from our data that there was very persistent fire activity in the Arctic circle, particularly in the Siberian Arctic," Mark Parrington, senior scientist at CAMS, part of the European Centre for Medium-Range Weather Forecasts, told CNN.

"What's been different this year is that we saw through the second half of July and the first couple of weeks of August, a very large cluster of fires burning very far into the Arctic circle and Siberia," he said.

Hazardous smoke plumes from the blazes covered an area equivalent to more than a third of Canada, scientists said.

The peak of the Arctic fire season was in July and early August, the data showed. Sakha Republic and the remote Russian Chukotka region saw "above average" daily total wildfire intensity in August.

Fires in the Eastern Federal District of Russia between June and August emitted approximately 540 megatonnes of carbon dioxide -- overtaking the previous total highest emissions dataset, recorded in 2003.

Though experts said the fires' ignition sources were uncertain, some fires earlier in the season are thought to have been so-called "zombie fires" -- blazes also known as holdover fires -- which can burn at low temperatures underground, and could have been alight during the winter.

The fires are a symptom of how the climate and the environment are changing in the Arctic, Parrington said.

"We've known for quite a few years now that the rate of change of temperature and climate variables in the high northern latitude is faster -- two to three times faster -- than the global average," he said.

"What we're seeing now is that these fires are symptomatic of that: It's warmer, dryer, so the vegetation and fuel is in the right conditions, and so when these fires are being ignited, they are able to burn for a long period of time uninterrupted, and grow as well," he said.

"Depending on the meteorology at the time, the huge amount of smoke and pollution that these fires produce doesn't necessarily stay there -- it is subject to long-range transport," Parrington added.

This could prove hazardous to both local populations and those further afield: Wildfire smoke contains a number of pollutants including carbon monoxide, nitrogen oxides, volatile organic compounds, and solid aerosol particles.

"You can see smoke heading out across the Arctic Ocean, you can see it heading out to North America," Parrington said. "Pollution and smoke doesn't know about international boundaries, those fires can affect a much larger population, thousands of kilometers away," he added.

The Arctic Circle is not alone in experiencing problem wildfires -- CAMS noted that a large portion of the southwestern United States has been ravaged by wildfires because of heatwave conditions, with California experiencing widespread fire activity.

The fires, mostly situated in California and Colorado, are thought to have been caused by lightning, according to the monitoring service.

Meanwhile, large plumes of smoke have been observed moving eastward across the Great Lakes, towards the North Atlantic.