Wildfires have increased in intensity and frequency in recent years, in part due to the effects of climate change on our planet. Beyond the destruction and chaos that widespread, frequent, and severe wildfires can bring, their emissions can have additional harmful effects on nearby communities. A recent study published in the journal Atmospheric Chemistry and Physics suggests that the recent increase in wildfire intensity and frequency may have produced larger-than-expected methane emissions — a byproduct that would only serve to perpetuate climate change and its effects.
Using a new remote sensing technique, the study’s authors — scientists from the University of California Riverside — measured the methane emitted from an entire plume of the Sequoia Lightning Fire Complex.
The new method is less costly and easier to deploy than the traditional method, which entailed capturing air samples via aircraft to analyze. The remote method is also safer and likely more accurate since it captures the entire plume of the fire rather than a small sample. "The plume, or atmospheric column, is like a mixed signal of the whole fire, capturing the active as well as the smoldering phases," said UCR environmental sciences professor and study co-author Francesca Hopkins.
The study revealed nearly 20 gigagrams of methane emitted by the Sequoia Lightning Fire Complex. Furthermore, the authors used existing estimates of the carbon dioxide released by the 2020 wildfires in California to calculate the accompanying methane emissions. California had a particularly intense year of wildfires in 2020, with greenhouse gas emissions to match. According to the California Air Resources Board, California’s 2020 wildfires released carbon dioxide emissions equivalent to about one-third of the state's carbon dioxide budget for the year.
The authors’ calculations estimated the accompanying methane emissions from the 20 largest fires to be more than 200 gigagrams, accounting for 13.7% of the state’s total human-caused methane emissions. This amount is greater than the methane produced by the state’s commercial and residential buildings, transportation, or electric power sectors. And the amount of methane from the top 20 fires in 2020 was more than seven times the average from wildfires in the previous 19 years.
If accounted for, the amount of methane produced by wildfires would have been the third biggest source of methane in the state. But currently, the state does not track wildfire-emitted methane — a fact that the study’s authors say is a major oversight. Methane is a powerful greenhouse gas, warming the planet 80 times more powerfully over a 20-year period than carbon dioxide.
"Typically, these sources have been hard to measure, and it's questionable whether they're under our control. But we have to try," Hopkins said. "They're offsetting what we're trying to reduce."
California recently set a target of a 40 percent reduction in greenhouse gas emissions by 2030. In 2016, Gov. Jerry Brown signed SB-32, codifying this into law.