Reconstructing ancient climates is important, but it isn’t easy. A new paper published last month uses new techniques to measure ancient CO₂ levels, using dino teeth.
When dinosaurs breathed in oxygen, tiny atmospheric signatures were locked into their hard tissues like tooth enamel. Researchers can now read these signatures using modern scientific techniques. And it has made fossil tooth enamel an important clue in reconstructing ancient Earth’s atmosphere.
“Air-breathing vertebrates respire air O2 and incorporate its isotope signature via body water into their hard tissues”, wrote the researchers. “Fossil tooth enamel can thus serve as a robust time capsule for ancient air O2 isotope compositions.”
How does it work?
The oxygen in the atmosphere carries a rare “anomaly” in one isotope, oxygen-17. This presence of O-17 depends on atmospheric CO₂ levels (pCO₂). More CO₂ means greater observation of the O-17 isotope.
G ross primary productivity, or GPP, is another factor that impacts the presence of O-17. GPP is the total amount of carbon compounds that plants produce through photosynthesis. More photosynthesis means lower levels of the O-17 isotope.
By measuring the presence of O-17 in fossil enamel, scientists can reconstruct ancient CO₂ levels and even estimate how productive the biosphere was at the time.
Dinosaurs inhabited a hotter and greener Earth
In this study, researchers analyzed dinosaur tooth enamel from the Late Jurassic and Late Cretaceous. The results suggest atmospheric CO₂ levels were much higher than today, around 1,200 parts per million in the Late Jurassic and 750 ppm in the Late Cretaceous. That’s about 2.5 to 4 times higher than pre-industrial values.
Further, using comparisons with other CO₂ data, the scientists inferred that the world’s plants may have been more productive then. Their calculations show that global primary productivity (i.e. photosynthesis levels) in the Mesozoic could have been 20% to 120% higher than today.
Taken together, these findings reveal that dinosaur-era Earth was a hotter and greener world.