Synthesis of methane emissions estimates from the Nord Stream subsea pipeline leaks

Abstract

The Nord Stream subsea pipeline leaks in September 2022 resulted in an unprecedented amount of methane to be released to the atmosphere. However, the total amount emitted remains ambiguous, reflected in a wide range of pipeline volumetric estimates (bottom-up) and measurement-based (top-down) emissions estimates.To derive a conclusive estimate of emissions, the United Nations Environment Programme’s International Methane Emissions Observatory (UNEP’s IMEO) has brought together a multitude of research groups spanning several disciplines to synthesise, contextualise and, where possible, reanalyse modelled emissions estimates. In this presentation, we present new pipeline rupture emission rate simulations and compare them with various top-down quantification approaches applied to the Nord Stream pipeline leaks. We show that our simulated bottom-upemissions are reconciled with airborne, satellite and tall tower estimates over various points throughout the emission event, indicating our cumulative total is a robust estimate of emissions.UNEP’s IMEO’s approach of synthesising and reanalysing existing data from all available sources assists in overcoming the methodological limitations of the individual approaches and provides a more holistic quantification of methane emissions from the Nord Stream pipeline leaks. This approach demonstrates how sharing data generated from various disciplines and quantification platforms can be used to overcome key assumptions when modelling and quantifying emissions. More generally, this study highlights the benefits of applying diverse measurement approaches to quantifying methane emissions in support of reduction commitments such as the Global Methane Pledge. Affiliations1-20 listed in Authors' Affiliations section21. Deutscher Wetterdienst, Frankfurter Strasse 135, 63067 Offenbach, Germany22. National Centre for Earth Observation, STFC Rutherford Appleton Laboratory (RAL), Chilton, UK23. Remote Sensing Group, STFC Rutherford Appleton Laboratory, Chilton, UK24. Technische Universität Braunschweig, Institute of Flight Guidance, Braunschweig, Germany25. Enagás Transporte SAU, Madrid, Spain26. GHGSat Inc., Montreal, Canada27. Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany28. National Centre for Earth Observation, University of Leicester, Leicester, UK29. School of Physics and Astronomy, University of Leicester, Leicester, UK30. School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, United States31. Key Laboratory of Coastal Environment and Resources of Zhejiang Province, School of Engineering, Westlake University, Hangzhou, Zhejiang Province, 310030, China