Very Strong Atmospheric Methane Growth in the 4 Years 2014–2017: Implications for the Paris Agreement

Abstract Atmospheric methane grew very rapidly in 2014 (12.7 ± 0.5 ppb/year), 2015 (10.1 ± 0.7 ppb/year), 2016 (7.0 ± 0.7 ppb/year), and 2017 (7.7 ± 0.7 ppb/year), 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 1,775 ppb in 2006 to 1,850 ppb in 2017. Simultaneously the 13 C/ 12 C isotopic ratio (expressed as δ 13 C CH4 ) has shifted, now trending negative for more than 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…

• SR
  Sight Research UK

  Awards: NE/I013342/1, NE/N016122/1, NE/R017638/1, NE/I02934X/1, NE/F006160/1, NE/S003657/1, NE/I014683/1, NE/P019641/1, NE/M001768/1, NE/K006045/1, NE/N018001/1, NE/N014375/1, NE/N015584/1, NE/K00221X/1, NE/N018028/1, NE/R01809X/1, NE/I028874/1, NE/N016211/1, ncas10014, NE/N015835/1, bas0100032, NE/S00159X/1, NE/M005836/1, NE/I029161/1, NE/N016238/1
• UH
  Universität Heidelberg
• NF
  Norges Forskningsråd
• NO
  National Oceanic and Atmospheric Administration
• NE
  Natural Environment Research Council

  Awards: NE/I02934X/1, bas0100032, NE/N015584/1, NE/I014683/1, NE/P019641/1, NE/I028874/1, NE/M005836/1, NE/N015835/1, NE/R01809X/1, NE/S00159X/1, NE/K00221X/1, NE/N016238/1, NE/P019641/1, NE/I029161/1, NE/N016122/1, NE/N018028/1, NE/I014683/1, NE/R017638/1, NE/S003657/1, NE/M001768/1, NE/N014375/1, NE/F006160/1, NE/I013342/1, NE/S00159X/1, NE/N016238/1, NE/I028874/1, NE/M001768/1, NE/N018001/1, NE/N016211/1, ncas10014, NE/K006045/1, NE/K006045/1
• RH
  Royal Holloway, University of London