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California wildfires hit CTRL+Z on 18 years of CO2e removal

Time to start considering forest blazes alongside industrial sources of greenhouse gases, say scientists

Researchers studying the effects of California's record-breaking 2020 wildfire season have uncovered some unsettling evidence. The fires in that single year undid all the state's greenhouse gas emission reductions since 2003 by a factor of two.

Researchers at the University of California, Los Angeles and the University of Chicago reported the findings in a brief paper that examined three fire emissions estimates to arrive at their number for 2020 wildfire emissions: 127 million metric tons (mmt) of carbon dioxide equivalent (CO2e).

Between 2003 and 2019, the researchers said, California's greenhouse gas (GHG) emissions declined by 13 percent, or around 65 mmt of CO2e. Those reductions were largely due to a shift to renewable energy and adopting other forms of emissions slashing by the energy generation sector, the team said. 

To put that 127 mmt in perspective, California's total GHG emissions in 2019 was 418 mmt of CO2e. When accounting for wildfire emissions, "this amounts to a 30 percent increase in total emissions by all sectors," the researchers said. 

The abstract of their report is stark:

We estimate that California's wildfire carbon dioxide equivalent (CO2e) emissions from 2020 are approximately two times higher than California's total greenhouse gas (GHG) emission reductions since 2003. Without considering future vegetation regrowth, CO2e emissions from the 2020 wildfires could be the second most important source in the state above either industry or electrical power generation.

"Essentially, the positive impact of all that hard work over almost two decades is at risk of being swept aside by the smoke produced in a single year of record-breaking wildfires," said lead author, Dr Michael Jerrett.

An emerging 'industry' to account for

Wildfires released so much GHG in 2020 that, when considered alongside other polluting industries in California, wildfires take a close second. Only the transportation industry in the state emits more GHGs.

When averaging out wildfire emissions for the past five years, the accidental discharges of CO2e "ranks above the most recent individual contributions from the Commercial & Residential, Agriculture, Recycling & Waste, and High Global Warming Potential sectors," the researchers found. 

Despite wildfires in California undoing the state's efforts to lead on climate change mitigation, Jerrett said they aren't getting attention despite emitting the same, or greater, amounts of GHGs. 

"Although wildfires are to some extent natural occurrences, human activity contributes to making wildfires 'unnatural disasters' through man-made climate change and development … in fire prone areas," Jerrett said.

The study didn't account for the growth of new vegetation in fire-swept areas, meaning it's an upper bound on the potential GHG emissions from wildfires. That said, even if vegetation is regrowing in burned regions the researchers don't think it will happen fast enough "to meet near and medium-term emission targets needed to avert passing the 1.5 degree C threshold." 

If the world is going to stay on track to meet climate goals, the researchers conclude, it's time to track wildfire emissions alongside other key sectors like transportation, industry and energy generation. As the paper notes, 18 of California's 20 most destructive fires have happened since 2000, and five of those in 2020 alone. ®

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