Understanding the glacial methane cycle

Research output: Contribution to journalArticle

Authors

  • Peter Hopcroft
  • Paul J. Valdes
  • Fiona M. O'Connor
  • Jed O. Kaplan
  • David J. Beerling

Colleges, School and Institutes

External organisations

  • Met Office
  • BRISTOL UNIVERSITY
  • Institute of Earth Surface Dynamics, University of Lausanne
  • Department of Animal and Plant Sciences, University of Sheffield

Abstract

Atmospheric methane (CH 4) varied with climate during the Quaternary, rising from a concentration of 375 p.p.b.v. during the last glacial maximum (LGM) 21,000 years ago, to 680 p.p.b.v. at the beginning of the industrial revolution. However, the causes of this increase remain unclear; proposed hypotheses rely on fluctuations in either the magnitude of CH 4 sources or CH 4 atmospheric lifetime, or both. Here we use an Earth System model to provide a comprehensive assessment of these competing hypotheses, including estimates of uncertainty. We show that in this model, the global LGM CH 4 source was reduced by 28-46%, and the lifetime increased by 2-8%, with a best-estimate LGM CH 4 concentration of 463-480 p.p.b.v. Simulating the observed LGM concentration requires a 46-49% reduction in sources, indicating that we cannot reconcile the observed amplitude. This highlights the need for better understanding of the effects of low CO 2 and cooler climate on wetlands and other natural CH 4 sources.

Details

Original languageEnglish
Article number14383
JournalNature Communications
Volume8
Publication statusPublished - 21 Feb 2017