Continuous sterane and phytane δ<sup>13</sup>C record reveals a substantial pCO<sub>2</sub> decline since the mid-Miocene.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 38890288.
- Also identified by DOI 10.1038/s41467-024-47676-9 and PMC identifier 11189397.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Constraining the relationship between temperature and atmospheric concentrations of carbon dioxide (pCO<sub>2</sub>) is essential to model near-future climate. Here, we reconstruct pCO<sub>2</sub> values over the past 15 million years (Myr), providing a series of analogues for possible near-future temperatures and pCO<sub>2</sub>, from a single continuous site (DSDP Site 467, California coast). We reconstruct pCO<sub>2</sub> values using sterane and phytane, compounds that many phytoplankton produce and then become fossilised in sediment. From 15.0-0.3 Myr ago, our reconstructed pCO<sub>2</sub> values steadily decline from 650 ± 150 to 280 ± 75 ppmv, mirroring global temperature decline. Using our new range of pCO<sub>2</sub> values, we calculate average Earth system sensitivity and equilibrium climate sensitivity, resulting in 13.9 °C and 7.2 °C per doubling of pCO<sub>2</sub>, respectively. These values are significantly higher than IPCC global warming estimations, consistent or higher than some recent state-of-the-art climate models, and consistent with other proxy-based estimates.