Final answer:
The PETM, or Paleocene-Eocene Thermal Maximum, refers to a significant period of global warming that occurred approximately 56 million years ago and is studied for its impact on climate, ecosystems, and the carbon cycle.
Step-by-step explanation:
PETM stands for the Paleocene-Eocene Thermal Maximum, which is a significant geological event known for a dramatic global warming period. This event occurred about 56 million years ago (56 Ma), and is particularly noteworthy for geologists and paleoclimatologists studying past climates and extinctions. During the PETM, there was a rapid spike in Earth's temperature, which had profound effects on the planet's climate, ecosystems, and carbon cycle. Geologists have recognized it by studying sediment layers and finding a distinct carbon isotope signature corresponding to this time period. The PETM is often mentioned in discussions on climate change, as it may provide insights into how Earth's climate system responds to large influxes of greenhouse gases.