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Tim Arnold

Tim Arnold

Associate Professor

Tim Arnold

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

Author

  • Alice E. Ramsden
  • Anita L. Ganesan
  • Luke M. Western
  • Matthew Rigby
  • Alistair J. Manning
  • Amy Foulds
  • James L. France
  • Patrick Barker
  • Peter Levy
  • Daniel Say
  • Adam Wisher
  • Tim Arnold
  • Chris Rennick
  • Kieran M. Stanley
  • Dickon Young
  • Simon O'Doherty
Show all

Summary, in English

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 spatially and temporally 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 0.27ĝ€¯(95ĝ€¯% uncertainty interval 0.26-0.29)ĝ€¯Tgyr-1 from fossil fuel sources and 2.06ĝ€¯(1.99-2.15)ĝ€¯Tgyr-1 from non-fossil fuel sources, during the period 2015-2019. Uncertainties in UK fossil fuel emissions estimates are reduced on average by 15ĝ€¯% and up to 35ĝ€¯% when incorporating ethane into the inverse model, in comparison to results from the methane-only inversion.

Publishing year

2022-03-25

Language

English

Pages

3911-3929

Publication/Series

Atmospheric Chemistry and Physics

Volume

22

Issue

6

Document type

Journal article

Publisher

Copernicus GmbH

Status

Published

ISBN/ISSN/Other

  • ISSN: 1680-7316