Low CO2 levels of the entire Pleistocene epoch

Quantifying ancient atmospheric p CO 2 provides valuable insights into the interplay between greenhouse gases and global climate. Beyond the 800-ky history uncovered by ice cores, discrepancies in both the trend and magnitude of p CO 2 changes remain among different proxy-derived results. The traditional paleosol p CO 2 paleobarometer suffers from largely unconstrained soil-respired CO 2 concentration ( S (z)). Using finely disseminated carbonates precipitated in paleosols from the Chinese Loess Plateau, here we identified that their S (z) can be quantitatively constrained by soil magnetic susceptibility. Based on this approach, we reconstructed p CO 2 during 2.6–0.9 Ma, which documents overall low p CO 2 levels (<300 ppm) comparable with ice core records, indicating that the Earth system has operated under late Pleistocene p CO 2 levels for an extended period. The p CO 2 levels do not show statistically significant differences across the mid-Pleistocene Transition ( ca . 1.2–0.8 Ma), suggesting that CO 2 is probably not the driver of this important climate change event.