Toward a Cenozoic history of atmospheric CO.

The geological record encodes the relationship between climate and atmospheric carbon dioxide (CO) over long and short timescales, as well as potential drivers of evolutionary transitions. However, reconstructing CO beyond direct measurements requires the use of paleoproxies and herein lies the challenge, as proxies differ in their assumptions, degree of understanding, and even reconstructed values. In this study, we critically evaluated, categorized, and integrated available proxies to create a high-fidelity and transparently constructed atmospheric CO record spanning the past 66 million years.

Molecular fossils from phytoplankton reveal secular co trend over the Phanerozoic.

Past changes in the atmospheric concentration of carbon dioxide (co) have had a major impact on earth system dynamics; yet, reconstructing secular trends of past co remains a prevalent challenge in paleoclimate studies. The current long-term co reconstructions rely largely on the compilation of many different proxies, often with discrepancies among proxies, particularly for periods older than 100 million years (Ma). Here, we reconstructed Phanerozoic co from a single proxy: the stable carbon isotopic fractionation associated with photosynthesis (Ɛ) that increases as co increases.