Quantifying the annual atmospheric CO2 burden from biomass burning and its transport time to monitoring sites.
Journal Article
Overview
abstract
In the backdrop of increasing global temperatures, carbon dioxide (CO2) emissions from biomass burning contribute to positive climate feedback under the failure of forest regrowth, leading to a long-term loss of carbon sinks. This study assesses biomass burning CO2 contributions and transport times using the NIES-TM model (2003-2019) with GFEDv5 and GFAS emissions across 16 biomes. The Tropical & Subtropical Grasslands, Savannas and Shrublands (TSG) and Tropical & Subtropical Moist Broadleaf Forests (TSM) biomes contributed the highest, 10.74 ppm and 6.13 ppm respectively over 17 years with the GFED-based estimates. Global annual surface CO2 burden in the atmosphere from biomass burning was 1.5 ± 0.07 ppm yr-1 (GFED) and 1.01 ± 0.08 ppm yr-1 (GFAS), while XCO₂ values were slightly lower. Trend analysis revealed a significant decreasing trend in TSG and TSM, and an increasing trend in boreal forests (BOF). The mean transport time of CO2 to monitoring stations ranged between 6 and 10 days, with regional variation influenced by biome proximity and atmospheric dynamics. Periodogram based spectral analysis showed multiple peaks at several stations, indicating contributions from various biomes spread and seasonality. A Random Forest model trained on biome-wise mean age and driven by 850 hPa winds and biome proximity revealed that zonal wind mainly controls transport time, while proximity dominates in Temperate Coniferous Forest (TCF) and BOF. The study finds that annual fire driven CO2 enhancement (> 1.0 ppm) exceeds ground-based detection uncertainty, matches the satellite XCO2 retrieval uncertainty and detectable within an average of 6-8 days. These quantifications imply the importance of the need for accurate fire emissions in the top-down flux estimates and support the use of a 7 day back- trajectory window in regional inversions. Our findings underscore the shifting patterns in burning biomes and emphasize the importance of considering the spatial extent of each biome when evaluating the impact of biomass burning on atmospheric CO2 levels.
