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Global warming

Reconstructing Atmospheric CO2 Concentration in the Late Miocene

Strategic Insights

— 2 min read

Researchers have made significant findings in understanding the relationship between greenhouse gas concentrations and climate change in a warmer-than-modern world. By analyzing paleoceanography data, scientists have reconstructed atmospheric CO2 concentration in the Late Miocene, a period crucial for understanding Earth's climate history. The study highlights the importance of reliable surface ocean temperatures in calculating solubility and atmospheric CO2. The research also underscores the challenges of using different proxies to estimate CO2 concentrations, with some proxies yielding inconsistent results.

Key Takeaways:

  • The study emphasizes the significance of reconstructing atmospheric CO2 concentration in the Late Miocene to understand the relationship between greenhouse gas concentrations and climate change in a warmer-than-modern world.
  • Both delta B-11-based and alkenone-epsilon(p)-based CO2 estimates feature uncertainties due to poorly constrained past seawater chemistry and algal physiological processes, respectively.
  • The new study generates records of alkenone epsilon(p) and delta B-11 from the Western Tropical Atlantic ODP Site 926 during the Late Miocene, providing surface ocean temperature estimates from coccolith clumped isotope thermometry, alkenone undersaturation ratios, and planktonic foraminiferal Mg/Ca ratios.
  • The research found that new alkenone epsilon(p) CO2 estimates at 926 yield generally similar CO2 levels (400 ppm +/- 100 ppm) as the new and published delta B-11-based CO2 records (500 ppm +/- 100 ppm) for the site.
  • The study highlights the challenges of estimating delta C-13(DIC) from planktic foraminifera or variations in algal physiology, which may bias the epsilon(p)-based CO2 reconstructions in this interval at Site 926.
  • The research aims to evaluate which proxy indicators can best predict variations in algal physiology that may bias CO2 reconstructions.

Statistics:

  • 400 ppm: Atmospheric CO2 concentration estimated by new alkenone epsilon(p) records at ODP Site 926.
  • 500 ppm: Atmospheric CO2 concentration estimated by new and published delta B-11-based CO2 records at ODP Site 926.
  • 100-200 ppm: Difference between CO2 values from epsilon(p) and other records over the 7.3 to 7.8 Ma interval.
  • 7.3-7.8 Ma: Time period studied, highlighting the importance of understanding Earth's climate history in this interval.

Sources:

  • Paleoceanography and Paleoclimatology. (2025;40(9).
  • Stoll, H. (Swiss Federal Institute of Technology, Dept. of Earth Sciences, Zurich, Switzerland).
  • Tanner, T., Hernandez-Almeida, I., Zhang, H., Jaggi, M., Bernasconi, S. M., Rae, J., Dumont, M., & Jurikova, H. (2025). Multi-proxy Estimates of Sea Surface Temperature and Co 2 In the Western Atlantic During the Late Miocene.
  • Swiss Federal Institute of Technology. (2025).
  • Swiss National Science Foundation (SNSF), ETH core funding, Swiss National Science Foundation (SNSF).

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