Fossils Reveal the Cause of One of the Greatest Climate Changes
Atmospheric carbon dioxide (CO2) is a key greenhouse gas of the Earth, influencing climate and living conditions on land and in oceans. While its role in current climate changes is relatively well understood, its long-term impact in geological history has been poorly documented so far. This is because reconstructing ancient CO2 levels based on rock records is not straightforward. An international team of scientists, led by Slovak researcher Hana Jurikova from the University of St. Andrews in Scotland, has for the first time clarified the role of carbon dioxide in the prolonged glaciation of the Earth at the end of the Paleozoic era. The team also answered questions about the conditions under which the world emerged from this ice age.
“We found that the Permo-Carboniferous glaciation (the so-called Late Paleozoic Ice Age, which occurred between 370 and 294 million years ago) was characterized by long-term low CO2 levels (~200-300 ppm). Atmospheric CO2 then suddenly rose during the early Permian (294 million years ago) due to extensive volcanic eruptions, warming the planet and melting the ice,” explains Dr. Hana Jurikova, the lead author of the study.
By combining boron isotopes with isotopes of strontium, carbon, and oxygen preserved in the calcite shells of fossilized brachiopods, the scientific team was able to calculate how much CO2 was present in the Earth's atmosphere in the past and how these levels changed over time. These organisms first appeared during the Cambrian period and continue to inhabit marine environments today. Their calcite shells crystallize in partial equilibrium with the chemical composition of seawater, making their geochemical composition an excellent indicator of climatic conditions in the distant past.
Dr. Jurikova collaborated with colleagues from eight other universities and institutions worldwide, including the Slovak Academy of Sciences. “The end of the Permo-Carboniferous glaciation marked a turning point in the evolution of terrestrial and marine ecosystems. We now know that atmospheric CO2 significantly contributed to this transition,” says Dr. Adam Tomašových from the Earth Science Institute of the Slovak Academy of Sciences, one of the study's co-authors.
CO2 plays a crucial role in the atmosphere by absorbing infrared radiation, which warms the atmosphere. Thus, when atmospheric CO2 levels rise, Earth's climate warms. Low atmospheric CO2 levels during the Carboniferous and early Permian significantly contributed to the onset of a vast ice age, while increased CO2 levels at the beginning of the Permian led to global warming and the melting of ice sheets. As the Late Paleozoic period demonstrated, certain levels of CO2 are necessary to maintain Earth's habitability and prevent it from freezing. However, a significant increase in CO2 caused global warming, rising sea levels, and may result in similar effects in the future.
The new study, published in early January in the prestigious scientific journal Nature Geoscience, reveals for the first time a critical part of the geological record documenting one of the Earth's greatest climatic transformations in its long history. It provides substantial evidence that CO2 has influenced Earth's climate and living conditions for hundreds of millions of years.
Processed: Monika Tináková
Source and contact information: Adam Tomašových, Earth Science Institute, SAS, adam.tomasovych@savba.sk;
Hana Jurikova, School of Earth and Environmental Sciences, University of St Andrews, hj43@st-andrews.ac.uk
Collective of authors:
Jurikova H., Garbelli C., Whiteford R., Reeves T., Laker G.M., Liebetrau V., Gutjahr M., Eisenhauer A., Savickaite K., Leng M.J., Iurino D.A., Viaretti M., Tomašových A., Zhang Y., Wang W. Shi G.R., Shen S., Rae J.W.B., Angiolini L. Rapid rise in atmospheric CO2 marked the end of the Late Palaeozoic Ice Age. Nature Geoscience 18, 91–97 (2025). https://doi.org/10.1038/s41561-024-01610-2.