Dinosaur Teeth Provide Key Clues to Earth’s Climate Past, Revealing High Levels of Carbon Dioxide
A new study finds that the Mesozoic Era saw significantly higher quantities of the greenhouse gas than both pre-industrial and modern levels, likely due to volcanic activity
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Researchers have inferred the prehistoric composition of Earth’s atmosphere during the Mesozoic Era (from 252 million to 66 million years ago) by investigating something unexpected: dinosaur teeth.
By breathing, dinosaurs absorbed oxygen from the atmosphere into their hard tissues—and today’s vertebrates do the same. That stored oxygen contains chemical clues that preserve conditions about the atmosphere at the time. Fortunately for scientists, tooth enamel is a hard tissue that can survive for millions of years, making dinosaur teeth “a robust time capsule” for learning about the ancient climate, according to the study published last week in the journal PNAS.
Researchers specifically looked at the ratio of certain oxygen isotopes, or versions of that same element with slightly different properties, contained in the teeth. Zeroing in on one called oxygen-17 let the team predict the amount of carbon dioxide in the atmosphere, because changes in atmospheric carbon dioxide and plant photosynthesis can impact oxygen isotopes.
They investigated Late Jurassic (145 million to 164 million years ago) and Late Cretaceous (66 million to 101 million years ago) dinosaur teeth from North America, Africa and Europe to piece together what the climate looked like at those times.
Did you know? Insights from ancient tooth enamel
Because teeth and bones can stand the test of time much better than soft tissues can, paleontologists are turning to preserved tooth enamel to recover proteins and DNA that can shed light on the biology of the past.
The analysis revealed that the Late Jurassic saw four times the amount of atmospheric carbon dioxide compared to pre-industrial levels—around 1,200 parts per million (ppm), compared to 280 ppm before the Industrial Revolution. The Late Cretaceous level was slightly lower, at about 750 ppm. Both figures are also significantly higher than today’s carbon dioxide concentration, which is currently around 425 ppm.
Overall, these higher levels of carbon dioxide were probably related to volcanic activity, the research suggests. In fact, the oxygen isotopes in two of the analyzed teeth—one belonging to a Tyrannosaurus rex and the other to a Kaatedocus siberi—point to carbon dioxide spikes that may have been caused by large eruptions, such as those in the Deccan Traps of modern-day India at the end of the Cretaceous.
“Our findings provide a new research avenue to reconstruct a direct link between land-living vertebrates and the atmosphere they breathed,” study co-author Thomas Tutken, a paleontologist and geochemist from Johannes Gutenberg University Mainz in Germany, tells ScienceAlert’s Michelle Starr.
Dinosaur teeth “recorded the climate more than 150 million years ago—and at last we are able to read that record,” says study lead author Dingsu Feng, a geochemist at the University of Gottingen in Germany, in a statement.
Furthermore, the study finds that the total photosynthesis carried out by plants globally during the Mesozoic Era was twice as high as it is today. According to another statement, the higher levels of photosynthesis were likely related to the elevated atmospheric carbon dioxide and higher average annual temperatures. Since research suggests that more photosynthesis means more plant growth, understanding prehistoric photosynthesis levels can shed light on Mesozoic vegetation, as well as the broader ecological web.
“The information obtained through our study on the global primary production [photosynthesis] provides important evidence of both marine and terrestrial food webs that would otherwise be difficult to obtain,” Eva M. Griebeler, co-author of the study and an ecologist from Johannes Gutenberg University Mainz, says in a statement.
Traditionally, researchers study bygone climates by investigating materials in soil and marine features that can be used as environmental proxies. But studying these sorts of remains tends to come with more uncertainty. The team’s dinosaur tooth-based approach opens a new avenue in paleoclimatology.
“Our method gives us a completely new view of the Earth’s past,” Feng says in a statement. Investigating the “composition of the early Earth’s atmosphere and the productivity of plants at that time,” she adds, “is crucial for understanding long-term climate dynamics.”
Editor’s Note, August 20, 2025: The lead image caption and credit have been updated with new details to reflect the origin of the object pictured.
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