Low CO(2) levels of the entire Pleistocene epoch

Quantifying ancient atmospheric pCO(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 pCO(2) changes remain among different proxy-derived results. The traditional paleosol pCO(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 pCO(2) during 2.6–0.9 Ma, which documents overall low pCO(2) levels (<300 ppm) comparable with ice core records, indicating that the Earth system has operated under late Pleistocene pCO(2) levels for an extended period. The pCO(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.