The Paleocene–Eocene Thermal Maximum (PETM), alternatively (ETM1), and formerly known as the "Initial Eocene" or "", a climate event, began at the temporal boundary between the Paleocene and Eocene epochs. The exact age and duration of the event remain uncertain, with an estimation on the age of about 55.5 ma (million years ago). According to McInerney and Wing 2011, a period of massive carbon injection has been estimated to have lasted <20 ka, with an entire duration of the event at ∼200 ka., with global temperatures increasing by 5–8◦C. A study in 2015 isolated two distinct pulses of carbon release, the first lasting less than 2,000 years. Repeated catastrophic carbon release is also more in line with current global warming, involving more than one carbon reservoir. However, a main difference is that during the time of the PETM, the planet was essentially ice free.

The Paleocene–Eocene Thermal Maximum (PETM), alternatively (ETM1), and formerly known as the "Initial Eocene" or "", a climate event, began at the temporal boundary between the Paleocene and Eocene epochs. The exact age and duration of the event remain uncertain, with an estimation on the age of about 55.5 ma (million years ago). According to McInerney and Wing 2011, a period of massive carbon injection has been estimated to have lasted <20 ka, with an entire duration of the event at ∼200 ka., with global temperatures increasing by 5–8◦C. A study in 2015 isolated two distinct pulses of carbon release, the first lasting less than 2,000 years. Repeated catastrophic carbon release is also more in line with current global warming, involving more than one carbon reservoir. However, a main difference is that during the time of the PETM, the planet was essentially ice free.