Paleocene–Eocene thermal maximum

A long time ago, the Earth got very hot.

This happened about 56 million years ago. Huge amounts of carbon went into the air. This made the world warm for a long time.

The heat changed the oceans too. Many tiny sea creatures died out. On land, new kinds of mammals appeared. Even the North Pole had no ice. It was a time of big changes for our planet.

About 55.8 million years ago, Earth went through a big change. This time is called the Paleocene–Eocene thermal maximum, or PETM.

During this time, the world got much warmer. This happened because huge amounts of carbon went into the air and the ocean. Scientists think this added between 2,000 and 7,000 gigatons of carbon.

The heat caused big changes for living things. In the deep ocean, many tiny creatures called benthic foraminifera died out.

On land, many new kinds of mammals appeared in Europe and North America. These included early primates.

The world looked different then. There was no ice at the North or South Poles. The oceans were also different. The Panama Isthmus did not connect North and South America yet. This let water flow easily between the Pacific and Atlantic Oceans. The PETM lasted for about 200,000 years. It helps us study how carbon and heat work together on our planet.

The Paleocene–Eocene thermal maximum, or PETM, was a huge change for our planet.

It happened about 55.8 million years ago. This event marks the boundary between two geological times called the Paleocene and the Eocene. During this brief period, the Earth got much warmer. A massive amount of carbon entered the ocean and the atmosphere. This carbon release caused the global temperature to rise quickly. Scientists study this time to understand how carbon and heat work together. It is one of our best ways to look at a greenhouse world.

This warming worked through a massive change in the carbon cycle. Large amounts of carbon were injected into the air and sea. This addition of carbon was likely between 2,000 and 7,000 gigatons.

Because of this carbon, the ocean and atmosphere changed deeply. Scientists see this through a change in carbon isotopes in rocks. This is a special way of measuring carbon in different places. The carbon change is visible in hundreds of locations around the globe. This process caused the sea to become more acidic in some areas. This is why some carbonate shells dissolved on the seafloor.

Researchers have studied these changes for many decades. They found the PETM by looking at sediment cores from the ocean floor. One famous core was taken in 1987 from a place called Maud Rise. This core was found at a site called Hole 690B in the South Atlantic. By looking at these layers, scientists can see how long the event lasted. They estimate the whole event lasted about 200,000 years. This includes the time when carbon levels rose and then slowly went back to normal. Finding these clues helps us map out the history of our climate.

Many specific numbers help us see how hot the world became. The temperature rise was likely between 3 and 8 degrees Celsius.

In the tropical western Pacific, ocean temperatures reached about 40 degrees Celsius. In the North Sea, the water reached highs of about 33 degrees Celsius. Even in Antarctica, temperatures were at least 15 degrees Celsius for part of the year. There were no large ice sheets on land during this time. The Arctic Ocean was also completely ice-free. These numbers show just how different the climate was back then.

These changes moved living things to new places. In the ocean, many tiny creatures called benthic foraminifera went extinct. Many new types of mammals also appeared on land. These included early primates in Europe and North America. The world looked different because the continents were in different spots. The Panama Isthmus did not connect North and South America yet. This allowed water to flow between the Pacific and Atlantic Oceans. Understanding the PETM helps us see how life reacts to a changing world.

The Paleocene–Eocene thermal maximum, often called the PETM, was a massive geological event. It occurred approximately 55.8 million years ago. This event marks the boundary between the Paleocene and Eocene epochs. During this time, the Earth experienced a rapid rise in global temperatures. A huge amount of carbon was released into the atmosphere and the oceans. Scientists study the PETM to understand how the carbon cycle works. It serves as a primary analogue for modern greenhouse worlds.

The mechanism behind this warming involved a massive carbon injection. This injection caused a negative carbon isotope excursion, or CIE. A CIE is a measurable drop in the ratio of carbon isotopes. This change is visible in marine and terrestrial carbonates across the globe. Researchers estimate that between 2,000 and 7,000 gigatons of carbon were added. This massive addition caused significant changes to ocean chemistry. In many deep-sea areas, the carbon caused carbonate dissolution. This means the shells of marine organisms actually dissolved on the seafloor.

Scientists identify several distinct stages and types of warming. The PETM was the most extreme of several "hyperthermals." Hyperthermals are geologically brief events lasting less than 200,000 years. These events feature rapid warming and massive carbon additions. Other hyperthermals occurred at different times in the Eocene. These include the ETM-2 event at 53.7 million years ago. Other events, like ETM-3, occurred around 52.8 million years ago. Each of these events changed the geochemical composition of Earth's sediments.

Our understanding of the PETM grew through decades of research. A major discovery happened in 1987 during the Ocean Drilling Program. Scientists recovered a famous sediment core from Hole 690B at Maud Rise. This location is in the South Atlantic Ocean. By studying this core, researchers could estimate the event's duration. They found the CIE lasted about 200,000 years at this site. This timeframe helps scientists understand how the carbon cycle recovers. It shows how slow the "flushing" of carbon is through natural processes.

The temperature rise during the PETM was quite intense. Estimates suggest a global temperature increase of 3 to 8 degrees Celsius.

In the tropical western Pacific, sea surface temperatures reached 40 degrees Celsius. The North Sea saw temperatures climb to about 33 degrees Celsius. Even Antarctica was much warmer than it is today. At least part of the year, temperatures there reached 15 degrees Celsius. The Arctic Ocean remained completely ice-free during this entire period. These extreme temperatures caused heat stress for many marine species.

These climate changes led to significant biological shifts. In the oceans, there was a mass extinction of benthic foraminifera. These are tiny organisms that live on the seafloor. At the same time, subtropical dinoflagellates expanded globally. On land, many modern mammal orders suddenly appeared. This included the appearance of early primates in Europe and North America. The changing environment forced many species to migrate or face extinction. These biological turnovers are a hallmark of the PETM boundary.

The PETM is deeply connected to the physical layout of the Earth. During this time, the continents were in different positions. The Panama Isthmus did not yet connect North and South America. This allowed water to circulate directly between the Pacific and Atlantic Oceans. The Drake Passage was also closed at this time. This configuration likely prevented the thermal isolation of Antarctica. Understanding these connections helps scientists model how oceans and continents influence climate.