Zichong Chen, Harvard: Understanding Methane Emissions

COMPASS 2024-04-19: Zichong Chen, Harvard University
"Understanding Methane Emissions With Satellite Observations: Sources, Trends, and Implications for Climate Action"

Methane (CH4) is a potent greenhouse gas with a relatively short atmospheric lifetime. Decreasing methane is a powerful lever to mitigate near-term warming and thereby give the world time to "bend the curve" on carbon dioxide (CO2) emissions and adapt to climate change. Current methane emission inventories are highly uncertain, difficult to be used as basis for mitigation strategies. I seek to better understand methane emissions at various scales by utilizing satellite observations and chemical transport models. My talk covers three topics driven by three questions. First, how can we use satellite observations of atmospheric methane to quantify regional methane emissions? Using the Middle East and North Africa region as an illustration, we utilize 2019 TROPOMI satellite observations in a high-resolution inversion to infer methane emissions from this region at up to 25 km × 25 km resolution, with an emphasis on the contributions from individual countries and from the oil and gas sector. Second, how well can we explain the recent rise in atmospheric methane mixing ratios? Interestingly, we find that rapidly increasing rice emissions in sub-Saharan Africa, driven by a widespread rice farming revolution, is a substantial but previously unrecognized contributor to the global methane trend. Third, can Earth observing (EO) satellites, which do not measure atmospheric methane, be used to better understand methane emissions? We use Landsat satellite imagery to develop a global high-resolution methane inventory from rice paddies with resolved seasonality. Compared to existing inventories, our rice methane emission inventory shows large improvements in both seasonality and spatial patterns in major rice-producing regions.