New study suggests we’re vastly underestimating megafire methane emissions

A new detection method for methane emissions has found that massive amounts of the gas are being released from California’s megafires.

Methane is the second most abundant greenhouse gas in our atmosphere and is 25 times as potent at trapping heat as carbon dioxide, in the short term.  

However, some methane goes untracked, both in Australia and overseas. For example, last year Cosmos published a story highlighting that one mine in Queensland could be emitting 35 times more methane than it’s reporting to authorities.

In California, wildfires are a significant issue, with climate change and drought to blame. But methane from these fires is currently not being accounted for by state air quality managers.

“Fires are getting bigger and more intense, and correspondingly, more emissions are coming from them,” said University of California Riverside environmental scientist Professor Francesca Hopkins.

“The fires in 2020 emitted what would have been 14 percent of the state’s methane budget if it was being tracked.”

Read more: UN announces new methane monitoring program – challenging Australia’s coal industry

This is partially because methane from fires is relatively hard to measure – traditionally it’s done by aircraft collecting wildfire air samples.

But the researchers in this new paper used observations taken on the ground and measured the methane and carbon dioxide levels by sun absorption. This is because gases absorb and then emit the sun’s heat energy.

This method allowed the researchers to measure a plume from a dangerous series of fires in 2020, without being in harm’s way.

“The plume, or atmospheric column, is like a mixed signal of the whole fire, capturing the active as well as the smouldering phases,” Hopkins said. “That makes these measurements unique.”

The researchers also suggest their data matches measurements from the European Space Agency’s TROPOMI data, which took a more sweeping, global view of the burned areas.

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, according to the study. The research has been published in Atmospheric Chemistry and Physics.