A humid climate state during the Palaeocene/Eocene thermal maximum

Area of Science:

• Paleoclimatology
• Geochemistry
• Climate modeling

Background:

• The Paleocene/Eocene Thermal Maximum (PETM), 55 million years ago, was marked by rapid global warming (5-10°C).
• This event is associated with a massive release of carbon (1,050-2,100 Gt) from methane hydrate reservoirs.
• Previous explanations involving direct greenhouse forcing from methane oxidation struggle to fully account for the observed warming magnitude and timing.

Purpose of the Study:

• To investigate the discrepancies between marine and terrestrial carbon isotope records during the PETM.
• To identify the underlying causes of these isotopic differences using carbon cycle models.
• To understand the mechanisms driving the abrupt climate change during the PETM.

Main Methods:

• Analysis of marine and terrestrial carbon isotope records across the PETM.
• Application of computational models simulating key carbon cycle processes.
• Comparison of model outputs with geological evidence to infer climate system dynamics.

Main Results:

• Significant differences were identified between marine and terrestrial carbon isotope datasets from the PETM.
• Model simulations suggest a distinct shift in the climate system state during the PETM.
• Evidence points to increased mid-latitude tropospheric humidity and heightened terrestrial carbon cycling.

Conclusions:

• The PETM warming cannot be solely explained by direct greenhouse gas forcing from methane hydrate release.
• A significant climate system shift, including increased atmospheric humidity, played a crucial role in PETM warming.
• The fundamental drivers of this climate system shift remain an open area for future research.