Observing, Quantifying, and Mitigating Emissions of Methane to the Atmosphere using Multi-csale Atmospheric Measurements (Invited Presentation) (Core Science Keynote)

Atmospheric methane concentrations have nearly tripled since the 1700’s, leading to significant radiative forcing of climate change and to changes in global photochemistry. Concentrations are currently rising at rates that rival the peak growth in the 1970’s. Why is this happening? A wide range of human activities lie behind increases in atmospheric methane, including emissions from the oil and gas value chain, end use of natural gas, coal mining, solid waste disposal, wastewater treatment, livestock production, and rice agriculture. The diversity of sources, and their geographic dispersal, makes it especially challenging to identify and quantify emissions, develop effective mitigation strategies, and document progress towards emission reduction goals.

This talk will focus on the application of multi-scale atmospheric measurements, both remote sensing and in situ, to quantify emission rates of methane for the full range of spatial and temporal scales. Our observations are intended to diagnose the underlying operational, engineering, and management factors that drive emissions of methane. The goal is to help design strategies for emission reductions that actually work in the real world – cost effective, realizable, equitable, and attractive to the myriad stakeholders that have to implement them. We present an overview of recent results from global area mapping satellites (e.g. TROPOMI), point source mappers (Sentinel 2, EMIT, CarbonMapper), and a new system for regional and point source imaging (MethaneSAT). We assess the unique contributions of airborne remote sensing and in situ observations. We pay particular attention to the problem of quantification of emission rates and validation of the results, for both point sources and area sources, including understanding the role of transient emissions with their high instantaneous rates and low average rates.

We conclude with an assessment of the future directions for addressing the problem of methane emissions, and the search for solutions. We offer the view that success requires close linkage between measurements at many scales, small and large, sustained observations, rigorous testing of inferred emission rates against known emission sources, and closely linking top-down measurements with inventory methods.