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

中文翻译：

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使用大气乙烷观测和不确定的排放比量化化石燃料甲烷排放

摘要。我们提出了一种使用甲烷和乙烷的观测来估算化石燃料甲烷排放量的方法，考虑到它们排放率的不确定性。乙烷：甲烷排放比作为贝叶斯模型中的一个可变参数，具有自己的先验分布和不确定性。我们发现使用排放比率分布可以减轻使用固定的、可能不正确的排放比率的偏差，并且该比率的不确定性会传播到排放的后验估计中。合成数据测试用于显示假设错误的乙烷：甲烷排放比的影响，并演示我们的可变参数模型如何更好地量化整体不确定性。我们还使用这种方法来估算来自英国与气候变化相关的排放量 (DECC) 网络中甲烷和乙烷的高频观测的英国甲烷排放量。使用联合甲烷-乙烷反演模型，我们估计来自化石燃料来源的年平均英国甲烷排放量约为 0.27（95% 不确定性区间 0.26-0.29）Tg 和每年来自非化石燃料的 2.06（1.99-2.15）Tg来源，在 2015-2019 年期间。与仅使用甲烷的反演结果相比，当将乙烷纳入反演模型时，英国化石燃料排放估算的不确定性平均减少 15%，最多可减少 35%。29) 2015-2019 年期间，化石燃料来源的每年 Tg 和非化石燃料来源的每年 2.06 (1.99-2.15) Tg。与仅使用甲烷的反演结果相比，当将乙烷纳入反演模型时，英国化石燃料排放估算的不确定性平均减少 15%，最多可减少 35%。29) 2015-2019 年期间，化石燃料来源的每年 Tg 和非化石燃料来源的每年 2.06 (1.99-2.15) Tg。与仅使用甲烷的反演结果相比，当将乙烷纳入反演模型时，英国化石燃料排放估算的不确定性平均减少 15%，最多可减少 35%。