Evolutionary History of Atmospheric CO2 during the Late Cenozoic from Fossilized Metasequoia Needles

Abstract

The change in ancient atmospheric CO2 concentrations provides important clues for understanding the relationship between the atmospheric CO2 concentration and global temperature. However, the lack of CO2 evolution curves estimated from a single terrestrial proxy prevents the understanding of climatic and environmental impacts due to variations in data. Thus, based on the stomatal index of fossilized Metasequoia needles, we reconstructed a history of atmospheric CO2 concentrations from middle Miocene to late Early Pleistocene when the climate changed dramatically. According to this research, atmospheric CO2 concentration was stabile around 330–350 ppmv in the middle and late Miocene, then it decreased to 278–284 ppmv during the Late Pliocene and to 277–279 ppmv during the Early Pleistocene, which was almost the same range as in preindustrial time. According to former research, this is a time when global temperature decreased sharply. Our results also indicated that from middle Miocene to Pleistocene, global CO2 level decreased by more than 50 ppmv, which may suggest that CO2 decrease and temperature decrease are coupled.

Early Pleistocene Obliquity‐Scale pCO2 Variability at ~1.5 Million Years Ago

“…If, on the other hand, the Pliocene T. sacculifer-based pCO 2 estimates are correct, Pliocene pCO 2 was less elevated relative to early Pleistocene pCO 2 values and the linear relationship between benthic δ 18 O and pCO 2 forcing extended into the Pliocene (Figure 9a). The T. sacculifer-based estimates, with pCO 2 likely <350-400 μatm, support the evidence for lower Pliocene pCO 2 from other proxies (Figure 8): alkenone δ 13 C, stomatal indices, and paleosols (e.g., Badger et al, 2013;Da et al, 2015;Wang et al, 2015) and implies that atmospheric pCO 2 was relatively similar between the late Pliocene and early Pleistocene, despite the descent into cooler polar temperatures. If correct, this record implies that Arctic temperatures declined at the Plio-Pleistocene transition due to factors other than direct radiative pCO 2 forcing, such as the thickening of northern hemisphere ice sheets or reduced poleward oceanic heat transport.…”

“…The text discusses potential offsets due to evolutionary changes in foraminiferal physiology and consequent species-differences between pH and pCO 2 reconstructions. Paleo-pCO 2 reconstructions from paleosols (Da et al, 2015), stomatal indices (Kürschner et al, 1996;Retallack, 2009;Stults et al, 2011;Wang et al, 2015), and alkenone δ 13 C (Badger et al, 2013;Seki et al, 2010;Zhang et al, 2013)…”

A 14.5 million-year record of East Antarctic Ice Sheet fluctuations from the central Transantarctic Mountains, constrained with cosmogenic &lt;sup&gt;3&lt;/sup&gt;He, &lt;sup&gt;10&lt;/sup&gt;Be, &lt;sup&gt;21&lt;/sup&gt;Ne, and &lt;sup&gt;26&lt;/sup&gt;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.…”

Middle and Late Holocene altitudinal distribution limit changes of Fagus crenata forest, Mt. Kurikoma, Japan indicated by stomatal evidence

“…2015; Wang et al . 2015, 2018b). Meanwhile, the altitudinal transportation of leaves before fossilization also causes more considerable SI variation than that observed in a modern population at a given altitude (Wang et al .…”