NOTICE (September 2017): Data previously stored at the CDIAC archive are being transitioned to the new, ESS-DIVE archive. This website provides access to the CDAIC data during the transition. If you have any questions regarding the new archive or the data transition, please contact

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Carbon-13 in CH4

Carbon-13 in CH4 has decreased since 2008, but the short record (only back to 1998) combined with multiple sources precludes any simple explanation at this point. Ratios of 13C/12C in CH4 tend to be lower in the Northern Hemisphere.