Wildfires released record-breaking amount of carbon dioxide in 2021 – study

Carbon dioxide emissions from wildfires that have been globally on the rise since 2000 spiked dramatically to a record high in 2021, according to a new study.

The research, published on Thursday in the journal Science, found that nearly half a gigaton of carbon – 1.76 billion tons of the greenhouse gas – was released from the burning of boreal forests in the high-latitude regions of North America and Eurasia in 2021.

This is about 150 per cent higher than annual mean CO₂ emissions between 2000 and 2020, according to the international team of scientists led by those from the University of California, Irvine.

“According to our measurements, boreal fires in 2021 shattered previous records,” study co-author Steven Davis said.

“These fires are two decades of rapid warming and extreme drought in Northern Canada and Siberia coming to roost, and unfortunately even this new record may not stand for long,” Dr Davis added.

Researchers warn that the worsening fires are part of a downward spiral of human-induced climate change in which carbon dioxide emissions warm the planet and create conditions conducive to more fires and more emissions.

Scientists, including study co-author Yang Chen, say the escalation of wildfires in the boreal region could accelerate the release of the large carbon storage in the tundra soil layer and contribute to the northward expansion of shrubs.

“These factors could potentially lead to further warming and create a more favorable climate for the occurrence of wildfires,” Dr Chen added.

The emissions from wildfires in 2021 were “nearly twice” as much CO₂ as global aviation that year, scientists say.

“If this scale of emissions from unmanaged lands becomes a new normal, stabilising Earth’s climate will be even more challenging than we thought,” Dr Davis added.

Until now, scientists say the estimation of carbon dioxide released during wildfires has been difficult due to several reasons.

Due to smoke-enshrouded terrains during wildfires, they say satellite observations do not provide a sufficiently fine resolution to analyse CO₂ emissions.

Models used to estimate fuel consumption and fire efficiency are not robust enough to assess extreme wildfires, researchers say.

“Earth’s atmosphere already contains large amounts of carbon dioxide from human fossil fuel burning, and the existing greenhouse gas is difficult to distinguish from that produced by forest fires,” Dr Chen added.

In the new study, using data on carbon monoxide (CO) emissions from the Measurements Of Pollution In The Troposphere (MOPITT) satellite instrument along with datasets on existing fire emissions and wind speed, researchers reconstructed changes in global fire CO₂ emissions from 2000-2021.

An anomalous abundance of CO provides evidence of fires.

Scientists also confirmed the occurrence of extreme fires in 2021 using data sets provided by NASA satellites.

“Combining these approaches can result in a more comprehensive understanding of wildfire patterns and their impacts,” Dr Chen said.

Researchers found that the higher northern latitudes and areas with larger tree cover fractions were especially vulnerable.

“Wildfire carbon emissions globally were relatively stable at about 2 gigatons per year for the first two decades of the 21st century, but 2021 was the year when emissions really took off,” Dr David said.

“About 80 per cent of these CO₂ emissions will be recovered through vegetation regrowth, but 20 percent are lost to the atmosphere in an almost irreversible way, so humans are going to have to find some way to remove that carbon from the air or substantially cut our own production of atmospheric carbon dioxide,” he added.