Bayesian analysis of the glacial-interglacial methane increase constrained by stable isotopes and Earth System modelling

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Colleges, School and Institutes

External organisations

  • University of Bristol
  • Max Planck Institute for the Science of Human History
  • ARVE Research SARL


The observed rise in atmospheric methane (CH4) from 375 ppbv during the last glacial maximum (LGM: 21,000 yr ago) to 680 ppbv during the late pre-industrial era is not well understood. Atmospheric chemistry considerations implicate an increase in CH4 sources, but process-based estimates fail to reproduce the required amplitude. CH4 stable isotopes provide complementary information that can help constrain the underlying causes of the increase. We combine Earth System model simulations of the late pre-industrial and LGM CH4 cycles, including process-based estimates of the isotopic discrimination of vegetation, in a box-model of atmospheric CH4 and its isotopes. Using a Bayesian approach, we show how model-based constraints and ice core observations may be combined in a consistent probabilistic framework. The resultant posterior distributions point to a strong reduction in wetland and other biogenic CH4 emissions during the LGM, with a modest increase in the geological source, or potentially natural or anthropogenic fires, accounting for the observed enrichment of δ13CH4.


Original languageEnglish
JournalGeophysical Research Letters
Early online date12 Mar 2018
Publication statusPublished - 22 Apr 2018


  • wetlanda , last glacial maximum , methane , 13CH4 , greenhouse gas , isotopic discrimination