This global cooling has been periodically disrupted by warm events such as the Paleocene-Eocene Thermal Maximum.

An example of a previous tipping point is that which preceded the rapid warming leading up to the Paleocene-Eocene Thermal Maximum.

By contrast, the Paleocene-Eocene Thermal Maximum may have initiated anywhere between a few decades and several thousand years.

At the start of the Eocene the Palaeocene-Eocene Thermal Maximum was reached.

The Paleocene-Eocene Thermal Maximum was an instance of geologically sudden climate change that occurred about 55 million years ago.

The period was after the Palaeocene-Eocene Thermal Maximum, and the climate and ecology of the site were very different from today.

The most dramatic example of sustained warming is the Paleocene-Eocene Thermal Maximum, which was associated with one of the smaller mass extinctions.

The climate there and then was tropical, consistent with the Paleocene-Eocene Thermal Maximum.

The period was very close to the Paleocene-Eocene Thermal Maximum and the climate and ecology of the site were very different.

Two events possibly linked in this way are the Permian-Triassic extinction event and the Paleocene-Eocene Thermal Maximum.