One of the most remarkable global warming events in the history of the Earth was the Palaeocene–Eocene Thermal Maximum (PETM), 56 million years ago, which is thought to have been caused by the release of greenhouse gases from mineral weathering. Several other, less severe warming periods occurred around 6–8 million years after the PETM. This paper shows that these smaller events were brief and surprisingly frequent, to a tempo paced by the Earth's orbit. Their rapid onset and recovery indicates a mechanism primarily dependent on shuffling carbon between the atmosphere and a dissolved, organic form in the ocean, in sharp contrast to the PETM's more sluggish greenhouse gas release from buried carbon reservoirs.
- Philip F. Sexton
- Richard D. Norris
- Samantha Gibbs