Methane, Monsoons, and Modulation of Millennial-Scale Climate

Kaustubh Thirumalai, Steven C. Clemens, Judson W. Partin

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


Earth's orbital geometry exerts a profound influence on climate by regulating changes in incoming solar radiation. Superimposed on orbitally paced climate change, Pleistocene records reveal substantial millennial-scale variability characterized by abrupt changes and rapid swings. However, the extent to which orbital forcing modulates the amplitude and timing of these millennial variations is unclear. Here we isolate the magnitude of millennial-scale variability (MMV) in two well-dated records, both linked to precession cycles (19,000- and 23,000-year periodicity): composite Chinese speleothem δ18O, commonly interpreted as a proxy for Asian monsoon intensity, and atmospheric methane. At the millennial timescale (1,000–10,000 years), we find a fundamental decoupling wherein precession directly modulates the MMV of methane but not that of speleothem δ18O, which is shown to be strikingly similar to the MMV of Antarctic ice core δ2H. One explanation is that the MMV of methane responds to changes in midlatitude to high-latitude insolation, whereas speleothem δ18O is modulated by internal climate feedbacks.

Original languageEnglish (US)
Article numbere2020GL087613
JournalGeophysical Research Letters
Issue number9
StatePublished - May 16 2020


  • late Pleistocene
  • methane
  • millennial-scale climate variability
  • modulation
  • monsoon
  • orbital forcing

ASJC Scopus subject areas

  • Geophysics
  • General Earth and Planetary Sciences


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