Very strong atmospheric methane growth in the four years 2014 - 2017: Implications for the Paris Agreement

Nisbet, EG; Manning, MR; Dlugokencky, EJ; Fisher, RE; Lowry, D; Michel, SE; Lund Myhre, C; Platt, SM; Allen, G; Bousquet, P; Brownlow, R; Cain, M; France, JL; Hermansen, O; Hossaini, R; Jones, Anna ORCID: https://orcid.org/0000-0002-2040-4841; Levin, I; Manning, AC; Myhre, G; Pyle, JA; Vaughn, B; Warwick, NJ; White, JWC. 2019 Very strong atmospheric methane growth in the four years 2014 - 2017: Implications for the Paris Agreement. Global Biogeochemical Cycles, 33 (3). 318-342. https://doi.org/10.1029/2018GB006009

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Abstract/Summary

Atmospheric methane grew very rapidly in 2014 (12.7±0.5 ppb/yr), 2015 (10.1±0.7 ppb/yr), 2016 (7.0± 0.7 ppb/yr) and 2017 (7.7±0.7 ppb/yr), at rates not observed since the 1980s. The increase in the methane burden began in 2007, with the mean global mole fraction in remote surface background air rising from about 1775 ppb in 2006 to 1850 ppb in 2017. Simultaneously the 13C/12C isotopic ratio (expressed as δ13CCH4) has shifted, in a new trend to more negative values that have been observed worldwide for over a decade. The causes of methane's recent mole fraction increase are therefore either a change in the relative proportions (and totals) of emissions from biogenic and thermogenic and pyrogenic sources, especially in the tropics and sub‐tropics, or a decline in the atmospheric sink of methane, or both. Unfortunately, with limited measurement data sets, it is not currently possible to be more definitive. The climate warming impact of the observed methane increase over the past decade, if continued at >5 ppb/yr in the coming decades, is sufficient to challenge the Paris Agreement, which requires sharp cuts in the atmospheric methane burden. However, anthropogenic methane emissions are relatively very large and thus offer attractive targets for rapid reduction, which are essential if the Paris Agreement aims are to be attained.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1029/2018GB006009
ISSN:	0886-6236
Additional Keywords:	Atmospheric methane, Methane isotopes, Wetland methane emissions, Fossil fuel methane emissions, OH destruction of methane, Paris Agreement
Date made live:	06 Mar 2019 11:57 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/522434

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