As countries around the world become more committed to carbon neutrality, the question of the quantity of carbon dioxide being emitted into the atmosphere and its sources is becoming ever more important. A study entitled "Record-high CO2 emissions from boreal fires in 2021" recently published in Science by Bo Zheng, assistant professor from the Tsinghua SIGS Institute of Environment and Ecology, and a team of international researchers brings us closer to these answers.
The research team has found that boreal fires – wildfires taking place in boreal forests which are located in high-latitude environments like Canada and Russia and typically account for 10% of global fire carbon dioxide emissions – contributed 23% (0.48 billion metric tons of carbon) in 2021, by far the highest fraction since 2000. This number of emissions is comparable to the anthropogenic emissions produced by Japan in a single year (which ranks fifth in total carbon emissions). It is also the highest number of emissions recorded from a wildfire event in this century.
Fig. 1 Atmospheric inversion-based estimates of annual and seasonal variation of boreal fire emissions and the comparisons with tropical fire emissions.
"Our study has raised the alarm. The issue of boreal forest fires is getting more and more severe,” Professor Zheng said.
Currently, human sources of carbon dioxide emissions are greater than natural ones. “With the global conversation around carbon neutrality, the carbon dioxide emissions from humans will decrease. Under these circumstances, the emissions created by natural wildfires will become more prominent," Professor Zheng said.
Boreal fires are extreme events, but climate change is creating conditions for these extreme events to occur more frequently. "As the climate warms, more plants grow. As temperatures rise in the boreal forests, the environment becomes drier. These conditions are fuel for boreal fires," said Professor Zheng. The increased occurrence of boreal fires will create a positive feedback loop wherein a larger number of fires means more carbon dioxide emitted into the atmosphere which will worsen global warming which in turn will increase the chances of boreal fires occurring.
While bringing attention to the severity of boreal fires with this study, the research team has also introduced innovation into measuring carbon dioxide emitted by wildfires with its satellite-based atmospheric inversion system. Instead of directly measuring CO2 which is hard to measure directly – CO2 concentrations can stay in the atmosphere for centuries – the team’s system uses CO concentrations gathered from satellite data to calculate the carbon dioxide emitted from a specific wildfire event. The system addresses shortcomings in other methods which use satellite data to calculate carbon emissions based on the area burned and may overlook the impact of smaller-scale wildfires on the total number of carbon dioxide emissions.
Fig. 2 The 2021 fire season anomaly (relative to the 2000–2020 fire season mean) of CO columns, wildfire CO2 emissions, and weather variables in the boreal region (> 50°N).
In the future, Professor Zheng’s team will continue to focus on this important global issue. "We hope to be able to give a more dynamic assessment of what is happening every year. We also hope to be able to give a more comprehensive assessment of the impact of the boreal fires, analyzing the impact on the environment, climate, and human beings."
Fig. 3 Fire CO2 emissions and climatic water deficit over the forest zones in boreal North America and boreal Eurasia.
"Climate change is complicated and there are a lot of aspects to focus on in this research. Our work strives to bring more attention to one of these important aspects," said Professor Zheng.
"Record-high CO2 emissions from boreal fires in 2021" was recently published in Science in the journal’s Research Highlights. The researchers also recently shared their findings at a news briefing at the 2023 American Association for the Advancement of Science (AAAS) Annual Meeting. The study has received both international and domestic media coverage.
Link to full article:
https://www.science.org/doi/10.1126/science.ade0805
Written by Alena Shish
Edited by Bo Zheng & Yuan Yang
Photos provided by Bo Zheng
