CO2 has regulated Earth’s climate for millions of years

The story of Earth’s climate can be found locked away in tiny shells that are scattered across ancient rocks. These seemingly modest remains have just helped scientists crack open one of the most significant climate mysteries in our planet’s history.

Researchers at the University of St Andrews have made remarkable discoveries about the fundamental role of carbon dioxide (CO₂) in shaping Earth’s climate.

The study provides new insights into how CO₂ regulated Earth’s warming and cooling over hundreds of millions of years.

CO₂: Earth’s climate architect

CO₂ is the most influential greenhouse gas on Earth. It traps heat from the Sun by absorbing it and radiating some of it back toward the planet’s surface.

This natural process keeps the Earth warm enough to sustain life. However, when CO₂ levels in the atmosphere increase, the planet becomes warmer, leading to significant climate changes.

While scientists understand how CO₂ affects the climate today, its role in shaping Earth’s climate millions of years ago has been harder to uncover.

Much of this information on CO₂ is hidden in geological records in the form of layers of rock and fossils that act like time capsules of Earth’s past environments.

Fossils reveal climate secrets

A team of scientists, led by Dr. Hana Jurikova at the University of St Andrews, has made a breakthrough in understanding this history.

The researchers studied a crucial period called the Late Paleozoic Ice Age, which occurred between 335 and 265 million years ago. This was a time of dramatic climate change when the Earth experienced extensive glaciation (ice ages) and subsequent warming.

The research revealed that CO₂ levels played a central role in driving these massive climatic transitions. By unlocking the secrets of this ancient period, the team showed how CO₂ fluctuations caused Earth to cool into ice ages and then warm as CO₂ levels rose again.

This discovery sheds light on how CO₂ has been a powerful driver of climate shifts throughout Earth’s history, influencing both the environment and the evolution of life on the planet.

Reconstructing past CO₂ levels

The team used the fossilized shells of brachiopods – ancient, clam-like organisms that date back hundreds of millions of years – to reconstruct past atmospheric CO₂ levels.

These shells, which are preserved across geological time, store chemical fingerprints of Earth’s past climate. By analyzing these fingerprints, the researchers determined how atmospheric CO₂ fluctuated during the Carboniferous and Permian periods.

“This showed that the Late Paleozoic Ice Age had prolonged low CO₂ levels, unprecedented in Earth’s history,” explained Dr. Jurikova. “Atmospheric CO₂ then rose abruptly, 294 million years ago, due to large-scale volcanic eruptions, warming the planet and melting back the ice.”

The study demonstrates that these CO₂ changes were instrumental in transitioning Earth out of an ice age and spurring the evolution of reptiles.

“The end of the Late Paleozoic Ice Age was a turning point in the evolution of life and the environment, leading to the rise of reptiles. Now we know it was paced by carbon dioxide,” said Dr. Jurikova.

Lessons for the present and future

The findings highlight the central role that CO₂ has played in regulating Earth’s climate over geological timescales.

Low CO₂ levels during the Carboniferous period triggered extensive glaciation, while higher levels in the Permian period led to global warming and ice sheet melting.

“This time interval gives a potential geological analog for the impact of CO₂ on our planet. CO₂ emissions in the past caused major global warming and sea level rise, and if left unchecked, they will do so again in the future,” noted Dr. James Rae, a co-author of the study.

CO₂ drives major climate transitions

This research highlights the immense power of CO₂ levels in shaping Earth’s climate over millions of years. CO₂ has been a key driver of major climate transitions, including ice ages and periods of significant warming.

By studying how CO₂ influenced the planet’s ancient climate, scientists have gained valuable insights into the ways greenhouse gases affect Earth’s environment over long timescales.

Today, humanity faces a similar challenge: rising CO₂ levels due to human activities like burning fossil fuels and deforestation. This modern surge in greenhouse gases is causing global temperatures to rise, leading to melting ice caps, rising sea levels, and extreme weather events.

The findings from this research serve as a stark reminder that unchecked CO₂ emissions can have dramatic and lasting impacts on our planet.

Understanding CO₂‘s role in Earth’s past climate transitions offers crucial lessons for addressing climate change today and highlights the urgent need for action to prevent further damage to the environment.

The study is published in the journal Nature Geoscience.

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