Low CO2 levels of the entire Pleistocene epoch

Abstract

Quantifying ancient atmospheric pCO2 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 pCO2 changes remain among different proxy-derived results. The traditional paleosol pCO2 paleobarometer suffers from largely unconstrained soil-respired CO2 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 pCO2 during 2.6–0.9 Ma, which documents overall low pCO2 levels (<300 ppm) comparable with ice core records, indicating that the Earth system has operated under late Pleistocene pCO2 levels for an extended period. The pCO2 levels do not show statistically significant differences across the mid-Pleistocene Transition (ca. 1.2–0.8 Ma), suggesting that CO2 is probably not the driver of this important climate change event.

A 14.5 million-year record of East Antarctic Ice Sheet fluctuations from the central Transantarctic Mountains, constrained with cosmogenic <sup>3</sup>He, <sup>10</sup>Be, <sup>21</sup>Ne, and <sup>26</sup>Al

“…CC BY 4.0 License. (Herbert et al, 2016); (b) Boron-isotope-, paleosol-, and stomataderived CO2 records (Beerling et al, 2009;Breecker and Retallack, 2014;Da et al, 2019;Dyez et al, 2018;Ji et al, 2018;Sosdian et al, 2018;Wang et al, 2015;Zhang et al, 2013) (d) benthic oxygen isotope stack (De Vleeschouwer et al, 2017), (e) Moraine age and uncertainty at Roberts Massif, plotted against deposit elevation. Note that deposition of the Misery moraines required ice to be > 300 m thicker than today, which is not reflected in the moraine elevation.…”

Interglacials of the Quaternary defined by northern hemispheric land ice distribution outside of Greenland

“…Proxy-based reconstructions of atmospheric CO 2 concentrations [10][11][12] (Fig. 4d) with the exception of paleosols 33 show a transition towards lower glacial values with time. These findings of stable interglacial CO 2 across the MPT, but higher glacial CO 2 before the MPT, are supported by snapshots of ice core data at 0.95 and 1.5 Myr BP from the Allan Hills blue ice area in Antarctica 34 .…”

“…c Sea level and d δ 18 O sw of different studies 29,48,49 . e Atmospheric CO 2 and its radiative forcing of ΔR ½CO 2 based on ice cores 37 , Allan Hills Blue Ice 34 , various marine proxies (δ 11 B from either T sacculifer 10,12,57 or G ruber 11,[58][59][60][61] , alkenones 58,62,63 ) paleosol 33 , model simulation 9 and data-based reconstruction 38,39 . Error bars show 1σ uncertainty.…”

“…4c); δ 18 O sw 29,49 (Fig. 4d); CO 2 reconstructions [9][10][11][12]33,34,37,39,[57][58][59][60][61][62][63] (Fig. 4e).…”

“…4 c); δ 18 O sw 29 , 49 (Fig. 4 d); CO 2 reconstructions 9 – 12 , 33 , 34 , 37 , 39 , 57 – 63 (Fig. 4 e).…”