The Paleocene-Eocene Thermal Maximum
Thousands of gigatonnes of carbon enter the atmosphere and the world warms 5 to 8 degrees in a few thousand years.
- When
- —
- Duration
- 200 thousand years
- Known to
- ± 100 thousand years
- Era
- Eocene, Cenozoic
At 56 million years ago the carbon isotope record drops sharply worldwide — the signature of a vast injection of isotopically light carbon, on the order of thousands of gigatonnes. Global temperatures rise 5 to 8 degrees Celsius, the Arctic Ocean reaches subtropical warmth, and the excursion takes roughly 200,000 years to fully recover. The source is debated between volcanic intrusion into organic sediments in the North Atlantic, destabilised methane hydrates, and burning peat. It is the closest natural analogue we have to the present, and the comparison is not reassuring: the PETM released its carbon over thousands of years, and industrial civilisation is doing something comparable in a couple of centuries.