Fire carbon emission constraints from space-based carbon monoxide retrievals during the 2019 intense burning season in Brazil

Abstract. In 2019, Brazil experienced an intensive fire season, despite the absence of major climate anomalies to enhance fire activity. Existing carbon monoxide (CO) emission estimates from state-of-the-art fire emission inventories differ by a factor two for the period and region. We provide a top-down estimate on CO emissions from these fires using the new CarbonTracker Europe – Long/Short Window (CTE-LW/SW) inverse modelling framework driven by column-averaged dry air CO mole fractions (XCO) from the MOPITT and TROPOMI satellite instruments. Our analysis indicates that the 2019 fires in Brazil released approximately 47 TgCO. Although structural atmospheric-chemistry related uncertainties remain (±15 TgCO), the inversions converged strongly to a common posterior (46–48 TgCO) independent of the prior emission inventory (GFED5.1, GFAS v1.2) or assimilated dataset (TROPOMI, MOPITT). Posterior fire emissions closely resemble the newly released GFED5.1, supporting recent advances in bottom-up fire modelling. Nonetheless, at the biome level, our results reveal a systematic underestimation—by roughly a factor of two—in the Cerrado and Caatinga savannas relative to both fire emission priors. While more targeted uncertainty assessments are required, we speculate that this emission gap unlikely stems from inversion choices alone and may indicate an underestimation of fuel loads or emission factors. Overall, we demonstrate CTE-LW/SW effectively leverages XCO to complement existing fire emission monitoring capacities at increasingly fine spatial resolution—a capability that is especially valuable in Brazil, where different fire regimes occur in close proximity and fire activity has intensified in recent years.