Climate feedback of forest fires amplified by atmospheric chemistry

The recent surge in forest fires has significantly impacted atmospheric chemistry, carbon cycles, and climate. Wildfires release CO₂ along with various reactive species such as CO, volatile organics, and nitrogen oxides. While the effects of CO₂ emissions on the carbon cycle and climate, as well as the impact of reactive species emissions on air quality and health, have been extensively studied, this research demonstrates that reactive species emitted from wildfires create a positive climate feedback through the “fire-chemistry-methane” mechanism. In this process, chemical reactions of reactive carbon species suppress the concentration of hydroxyl radicals, extending the lifetime of heat-trapping methane. The significance of this feedback is suggested by observations of multiple proxy gases for global atmospheric oxidation (i.e., methyl chloroform, methane, and CO) during recent extreme forest fire events. By coupling a fire-ecosystem model and an atmospheric chemistry model, we quantify the effect of this feedback in the future. We find that additional warming caused by this mechanism rivals that of wetland methane feedback and fire CO₂ feedback by the 2050s under an intermediate climate scenario. Our analysis highlights the critical role of atmospheric chemistry in regulating fire-climate interactions and the methane budget.