Quantifying fossil fuel methane emissions using observations of atmospheric ethane and an uncertain emission ratio

Abstract. We present a method for estimating fossil fuel methane emissions using observations of and ethane, accounting uncertainty in their emission ratio. The ethane:methane ratio is incorporated as spatially temporally variable parameter Bayesian model, with its own prior distribution uncertainty. find that an mitigates bias from fixed, potentially incorrect this propagated into posterior estimates emissions. A synthetic data test used to show the impact assuming demonstrate how our model can better quantify overall also use estimate UK high-frequency ethane Deriving Emissions linked Climate Change (DECC) network. Using joint methane–ethane inverse we annual mean approximately 0.27 (95 % interval 0.26–0.29) Tg yr−1 sources 2.06 (1.99–2.15) non-fossil sources, during period 2015–2019. Uncertainties are reduced on average by 15 up 35 when incorporating comparison results methane-only inversion.