Two Decades of Satellite Observations of Carbon Monoxide Confirm the Increase in Northern Hemispheric Wildfires

Biomass burning is an important and changing component of global and hemispheric carbon cycles. Boreal forest fires in Russia and Canada are significant sources of the greenhouse gases carbon dioxide (CO2) and methane (CH4). The influence of carbon monoxide (CO) on the greenhouse effect is practically absent; its main absorption bands of 4.6 and 2.3 mu m are far away from the climatically important spectral regions. Meanwhile, CO concentrations in fire plumes are closely related to CO2 and CH4 emissions from fires. On the other hand, satellite measurements of CO are much simpler than those of the aforementioned gases. The Atmospheric Infrared Sounder (AIRS) operating in the Thermal IR spectral region has provided a satellite-based CO data set since October 2002. This satellite data allow to estimate CO emissions from biomass burning north of 30 degrees N using a simple two-box mass-balance model. These results correlate closely with independently estimated CO emissions from the GFED4c bottom-up database. In 2021, both estimate record high emissions throughout the preceding two decades, double the annual emissions compared to previous periods. There have been two years with extremely high emissions (2003 and 2021) but for the rest of the data, an upward trend with a rate of 3.6 +/- 2.2 Tg CO yr(-2) (4.8 +/- 2.7% yr(-1)) was found. A similar rate of CO emissions can be seen in the GFED4c data.

Automated summary

Biomass burning has a significant impact on global and hemispheric carbon cycles, and boreal forest fires in Russia and Canada are major sources of carbon dioxide and methane emissions. Although carbon monoxide has minimal greenhouse effect, its concentrations are closely related to CO2 and CH4 emissions. Satellite measurements of CO provide a simple method for estimating emissions. Recent studies have shown record-high CO emissions from biomass burning, with a steady growth rate over the past two decades.