CLIMATE × EARTH

The Last Time Carbon Rose This Fast

~56 million years ago

Phanerozoic · Cenozoic · Paleogene · Eocene

More than ten thousand billion tonnes of carbon entered the ocean and the air over a few thousand years. Boron in fossil shells shows the surface of the sea acid throughout, and points at the source: volcanism along the opening North Atlantic, rather than the methane frozen in seafloor sediments that had long been blamed. Temperature rose about five degrees, and the foraminifera of the deep sea suffered their worst extinction of the last 66 million years.

Why it matters

Burning fossil fuels has no closer natural parallel. The difference is the rate: we are releasing carbon faster than that episode did, and the planet took 200,000 years to clear it.

Dating & uncertainty

The carbon release lasted a few thousand years and the warm interval about 200,000. Estimates of how much carbon entered the ocean and atmosphere, and from which source, still vary widely.

Sources

1. Zachos et al. (2005), Science · Rapid acidification of the ocean during the Paleocene-Eocene thermal maximum
2. Gutjahr et al. (2017), Nature · Very large release of mostly volcanic carbon during the Palaeocene-Eocene Thermal Maximum
3. Zeebe et al. (2016), Nature Geoscience · Anthropogenic carbon release rate unprecedented during the past 66 million years
4. Li et al. (2024), Nature Geoscience · Coupled decline in ocean pH and carbonate saturation during the Palaeocene-Eocene Thermal Maximum

Earth history as one day

23:42:1417 min 46 s before midnight

if Earth’s 4.54 billion years were compressed into a single day