New evidence changes key ideas about Earth’s climate history

A new study published in Science resolves a long-standing scientific debate and risks completely changing the way we think about Earth’s changing climate.

The research debunks the idea that the Earth’s surface (on land and sea) has experienced very warm temperatures over the past two billion years. Instead, it shows that Earth has experienced a relatively stable and mild climate.

Temperature is an important control over the chemical reactions that govern life and our environment. This groundbreaking work will have significant implications for scientists working on climate models or questions related to biological and climate evolution.

“Knowledge of past temperatures can help us understand how the Earth’s climate system works and better understand the conditions that allowed the origin and evolution of life,” says the geochemist and lead author from the University of Waikato , Dr. Terry Isson.

Understanding past temperatures and the evolution of life is not an exercise in history or pure intellectual curiosity. Research on past climate is important for researchers seeking to understand current climate and long-term future scenarios.

“We cannot use our planet as a large-scale laboratory. Looking to the past allows us to understand the processes that regulate Earth’s climate.”

In the work, Dr. Isson and Ph.D. student Sofia Rauzi adopted new methods to illuminate the history of Earth’s surface temperature.

They used five unique data records derived from different rock types, including shale, iron oxide, carbonate, silica and phosphate. Collectively, these “geochemical” records include more than 30,000 data points that span several billion years of Earth history.

To date, the study represents the most comprehensive collection and interpretation of one of the oldest geochemical records: oxygen isotopes. Oxygen isotopes are different forms of the element oxygen. It’s also the first study to use all five existing records to plot a consistent “map” of temperature over a huge portion of geologic time.

“By combining oxygen isotope records from different minerals, we were able to reconcile a unified temperature history on Earth, consistent across all five records, and the oxygen isotopic composition of seawater,” explains Dr. Isson.

The study refutes the idea that early oceans were warm with temperatures above 60°C around half a billion years ago, before the rise of land animals and plants. The data indicate relatively stable, temperate early oceans and temperatures of around 10°C, shaking up current thinking about the environment in which complex life evolved.

This work produces the first-ever record of the changing abundance of terrestrial (terrestrial) and marine clay throughout Earth’s history. This is the first direct evidence of an intimate connection between the evolution of plants, sea creatures that make skeletons and shells from silica (siliceous life forms), clay formation and climate global.

“The results suggest that the process of clay formation may have played a key role in regulating early Earth’s climate and maintaining the temperate conditions that allowed the evolution and proliferation of life on Earth “, explains Dr. Isson.

Overall, the work provides new evidence for Earth’s climate and geochemical history that needs to be better understood to inform and update current ideas and research on climate and evolution.

Dr Isson concludes: “The results give us an impetus to deepen our understanding of how life responds to and shapes climate on Earth. »