Observing megacity greenhouse gas emissions from space

Emissions of greenhouse gases (GHG) from megacities represent a significant and increasing contributor to anthropogenic GHG release. In efforts aimed at mitigation, some cities have enacted emissions reduction policies, but lack observation-based methods for verifying their efficacy. Atmospheric abundances in and around megacities are strongly impacted by anthropogenic GHG emissions, and therefore have the potential to provide objective, independent assessment of GHG emissions trends. Here we demonstrate the potential of satellites to provide accurate global monitoring of megacity GHG emissions. Specifically, we find GOSAT observations of column averaged CO2 and CH4 dry air mole fractions exhibit statistically significant enhancements over some representative megacities. We will discuss how these enhancements can be exploited to track anthropogenic emission trends with time. We will additionally examine the impact of these findings on regional and global flux inversions using satellite observations. Finally, we will discuss the limitations of current space-based observations, and the potential of future satellite missions to monitor global megacity emissions.