Long-term daily observations of methane and ammonia from space offer powerful constraints on emissions when ingested into data assimilation systems. In this presentation, I will present global emissions estimates for these two reactive gases capturing seasonal cycles and inter-annual variability. These gases are of interest because recent concentration trends have defied what would be expected from emissions inventory estimates. Methane concentrations surged in 2020-21 for reasons that remain debated in the literature, and I will present evidence that the surge was driven by emissions caused by record inundation of eastern Africa related to an Indian Ocean Dipole anomaly; I will also present detailed analysis of China's increasing methane emissions. While ammonia is not well-mixed, concentrations have been trending upwards in many regions. I will argue that ammonia emissions are increasing and will use a novel machine-learning method to suggest that agricultural sources (principally livestock) are the primary driver but climate variables also are non-negligible. I then use my data-driven results to project the climate-driven ammonia emissions penalty to 2100 and show that my estimates are comparable to results from mechanistic land models.
Quantifying biogenic emissions from space and interpreting drivers of change with machine learning
Host: Ceren Demirci