A Palaeogene perspective on climate sensitivity and methane hydrate instability.

Area of Science:

• Paleoclimatology
• Geochemistry
• Climate modeling

Background:

• The Paleocene-Eocene Thermal Maximum (PETM) was a significant global warming event and carbon cycle perturbation.
• It is characterized by a rapid negative carbon isotope excursion and a ~5-6°C global temperature rise.
• The PETM serves as a crucial natural experiment for testing climate and carbon cycle models.

Purpose of the Study:

• To synthesize carbon cycle model estimates for the PETM's carbon input and atmospheric CO2 perturbation.
• To review evidence for methane hydrate dissociation during the PETM.
• To assess PETM climate sensitivities in the context of modern climate models.

Main Methods:

• Synthesis of existing carbon cycle model estimates for PETM carbon input.
• Review of theoretical mass balance and sedimentary evidence for methane hydrate dissociation.
• Comparison of estimated PETM pCO2 increases with proxy temperature data.

Main Results:

• Estimated carbon mass input during the PETM ranges from 4000-7000 PgC.
• This substantial carbon input suggests a major source beyond methane hydrates.
• PETM pCO2 increases and temperature anomalies are consistent with current climate model sensitivities.

Conclusions:

• The PETM's carbon budget points to significant sources beyond methane hydrates.
• Climate sensitivities derived from the PETM event do not necessarily exceed those predicted by current climate models.
• The PETM provides valuable insights into transient climate change dynamics and model validation.