«

»

Print this Post

Upward revision of global fossil fuel methane emissions based on isotope database

Graph showing the revised and much higher than previously assumed amounts of methane emissions to the atmosphere.

Moving averages are shown; see Supplementary Fig. 18 for original mass balance results including inter-annual variability due to multiple components not accounted for in this model (see text). Dark and light grey bands mark the 25th/75th percentile and the 10th/90th percentile uncertainties, respectively. The dashed black line represents the linear trend of the means. Blue lines assume the mean δ13Csource values from the literature. (Graphic: Schwietzke S et al. (2016), Nature)

By revising the isotope source signatures this study finds that total fossil fuel methane emissions (fossil fuel industry plus natural geological seepage) are 60 to 110 per cent greater than current estimates suggest.

Abstract
Methane has the second-largest global radiative forcing impact of anthropogenic greenhouse gases after carbon dioxide, but our understanding of the global atmospheric methane budget is incomplete. The global fossil fuel industry (production and usage of natural gas, oil and coal) is thought to contribute 15 to 22 per cent of methane emissions to the total atmospheric methane budget. However, questions remain regarding methane emission trends as a result of fossil fuel industrial activity and the contribution to total methane emissions of sources from the fossil fuel industry and from natural geological seepage which are often co-located.

Here we re-evaluate the global methane budget and the contribution of the fossil fuel industry to methane emissions based on long-term global methane and methane carbon isotope records. We compile the largest isotopic methane source signature database so far, including fossil fuel, microbial and biomass-burning methane emission sources. We find that total fossil fuel methane emissions (fossil fuel industry plus natural geological seepage) are not increasing over time, but are 60 to 110 per cent greater than current estimates owing to large revisions in isotope source signatures. We show that this is consistent with the observed global latitudinal methane gradient. After accounting for natural geological methane seepage12, 13, we find that methane emissions from natural gas, oil and coal production and their usage are 20 to 60 per cent greater than inventories1, 2. Our findings imply a greater potential for the fossil fuel industry to mitigate anthropogenic climate forcing, but we also find that methane emissions from natural gas as a fraction of production have declined from approximately 8 per cent to approximately 2 per cent over the past three decades.

Bibliography:
Stefan Schwietzke, Owen A. Sherwood, Lori M. P. Bruhwiler, John B. Miller, Giuseppe Etiope, Edward J. Dlugokencky, Sylvia Englund Michel, Victoria A. Arling, Bruce H. Vaughn, James W. C. White, Pieter P. Tans
Upward revision of global fossil fuel methane emissions based on isotope database
Nature 538, 88–91 (06 October 2016) (Letter)
doi:10.1038/nature19797

Received 25 April 2016
Accepted 22 August 2016
Published online 05 October 2016

Similar articles

Facebooktwittergoogle_pluslinkedinmailby feather

Permanent link to this article: http://frack-free.rocks/upward-revision-of-global-fossil-fuel-methane-emissions-based-on-isotope-database/

Translate »