BURNING QUESTIONS ON CARBON EMISSIONS FROM FIRES (BURNQUEST)

Landscape fires, whether natural or human-induced, have a key impact on the Earth system via the release of pollutants, greenhouse gases and aerosols, affecting human health and climate. Over the next decades their role may increase related to drier and warmer conditions, exacerbating biome shifts and lowering biodiversity. In addition, this may provide one of the most detrimental climate-carbon feedbacks raising CO2-levels. The past two decades have seen gradual improvements in quantifying fire emissions, including those from CO2, with global emission estimates converging to around 2 Pg C per year, equivalent to 20% of global fossil fuel emissions. New emerging information on burned area and emissions modeling indicates this estimate may be a gross underestimation with recent insights indicating global fire emission estimates may be closer to 4 Pg C per year. Parallel to these new developments,thespace-based TROPOMI instrument, onboard ESA Sentinel-5p mission,is now providing unprecedented top-down constraints on fire emissions, in particular those of carbon monoxide (CO). We propose to build a modeling framework to address fire emission underestimation by solving for an inverse problem: calculating improved fire emissions using observations of CO from space. We will apply this framework with specific focus on the African sub-Saharan savanna and Indonesian peatland fires. These regions are of interest because they are responsible for a staggering 60% of the global fire CO2 output, but the emissions may even be much larger in reality. Alongside TROPOMI, we include in our study other important datasets, such as NO2 from TROPOMI to learn more about the combustion efficiency, and new high resolution burned area information derived from ESA’s Sentinel-2 images that provide alternative fire emissions that should better reflect the contributions of smaller sized fires. The novelty of our work is not only reflected in our attempt to improve and better understand the uncertainties of fire emissions of CO-and indirectly CO2-but also to provide a much-needed independent benchmark to which we can compare current and new emerging fire emission estimates against.