Late Cenozoic atmospheric CO₂ reconstruction

As the nearest geologic time period, the late Cenozoic witnessed major climate transitions such as the Northern Hemisphere Glaciation and the Mid-Pleistocene Transition, as well as time periods widely recognized as analogs of near-future climate such as the Mid-Miocene Climate Optimum and the Mid-Pliocene Warm Period. However, the role of CO₂ in these climate events remain unresolved, mainly due to the lack of high-resolution, high-precision CO₂ record.

Category 1 proxy-derived CO₂ estimates over the past 10 million years. Existing records suffer from large uncertainties, low agreements, and data gaps.¹

The Chinese Loess Plateau has been receiving eolian dust deposition since the late Oligocene. The paleosols developed on these eolian deposits hold valuable information of the long-term evolution of atmospheric CO₂ levels. Leveraging this unique archive, we improved the classic paleosol-CO₂ method by developing new constraint on the input parameter and new sampling method, allowing us to reconstruct a continuous Pleistocene CO₂ record with high fidelity.

Pleistocene loess-paleosol sequence on the Chinese Loess Plateau, characterized by light and dark layers formed during glacial and interglacial periods, respectively.²

The results show relatively stable CO₂ during the interglacial periods and long-term decline in glacial CO₂, highlighting the role of CO₂ in the amplification of the glacial cycles and the long-term global cooling. Moreover, our CO₂ data suggest increasing climate sensitivity under higher CO₂ levels, and overall higher climate sensitivity than model projections, indicating a potentially underestimated future warming.

Related Publications:

1. Da J, Zhang Y G, Wang H, et al. An Early Pleistocene atmospheric CO2 record based on pedogenic carbonate from the Chinese loess deposits[J]. Earth and Planetary Science Letters, 2015, 426: 69-75.
2. Da J, Zhang Y G, Li G, et al. Low CO2 levels of the entire Pleistocene epoch, Nat. Commun., 10, 4342[EB/OL].(2019)