This wildfire season so far in California has been extraordinary, causing thousands of fires — including one that, on… nearly a million acres burned, is the largest single fire in state history — spewing so much smoke that air quality has been affected thousands of miles away.
Wildfires can also have a global climate impact, as burning vegetation releases carbon dioxide that warms the earth. And from June to August, California fires emitted twice as much CO2 as the same period last year, and far more than any other summer in nearly two decades.
That is the conclusion of the Copernicus Atmospheric Monitoring Service, a European Union funded agency that estimates emissions based on satellite measurements available since 2003. During the three months, fires in California emitted more than 75 million tons of carbon dioxide.
That’s a small amount compared to annual global CO2 emissions from burning fossil fuels, which are expected to total about 33 billion tons this year. And most of the CO2 emitted by wildfires can be offset over time, as vegetation recolonizing those burned areas uses CO2 to grow. Still, any additional amount of CO2 in the atmosphere contributes to warming.
In total, fires across the western United States have emitted 130 million tons of CO2 this summer, according to the agency’s estimates. This included about 17 million tons in Oregon, more than 10 times the amount released last year. The Bootleg fire, which destroyed more than 400,000 acres in July and August, was one of the largest in Oregon’s history. The Dixie fire in Northern California is the largest in that state.
The erratic summer temperatures across much of the West, coupled with severe drought, together caused the fires to grow rapidly, sometimes engulfing tens of thousands of acres in a matter of hours.
“The ground is drier, the vegetation is drier,” said Mark Parrington, senior scientist and wildfire expert with the Copernicus Atmosphere Monitoring Service. “Add to that the drought, and that accelerates the size of the fire.”
So far, California wildfires have burned about 2.3 million acres, which is lower than last year’s totals as of this date. But dr. Parrington said emissions for June to August were higher this year because, due to the drought, severe fires generally started earlier than last year.
The wildfire season has been severe and emissions have set records, including in other parts of the Northern Hemisphere, the agency said.
There were major fires in western Canada and around the Mediterranean, including one in Greece, which grew from a few acres to more than 120,000 acres in less than three weeks.
In the Sakha Republic in northeastern Siberia, where major summer fires are not uncommon, this summer has been particularly bad, with fierce fires starting as early as June.
The burnt area in Sakha is much larger than in California, so emissions are much higher. The agency estimated CO2 emissions over the three months at more than 750 million tons, double the amount from the previous year.
Most of the fires in Siberia were below the Arctic Circle, unlike last year when much of the burned area was in the Arctic. This year, Arctic wildfires released about 65 million tons of CO2 in the summer, the agency said.
Copernicus uses data from sensors on several NASA satellites that measure the temperature of the surface brightness in near real time. It then looks for deviations from normal temperatures that indicate a fire, and estimates how much energy the fire radiates. Based on that, it estimates how much carbon dioxide and other gases are emitted from information about vegetation types.
Other groups estimate fire emissions after the season is over, using aerial or satellite images of burns and other data. dr. Parrington said his agency’s estimates historically “aligned pretty well” with the others.