Old Rocks
Diamond Member
According to this study, it appears that the present CO2 level is the highest it has been since the Miocene.
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RESEARCH ARTICLE| MAY 29, 2020
Brian A. Schubert;
A. Hope Jahren
Geology (2020) 48 (9): 888–892.
A 23 m.y. record of low atmospheric CO2 | Geology | GeoScienceWorld
Article history
Skip Nav Destination
RESEARCH ARTICLE| MAY 29, 2020
A 23 m.y. record of low atmospheric CO2
Ying Cui;Brian A. Schubert;
A. Hope Jahren
Geology (2020) 48 (9): 888–892.
A 23 m.y. record of low atmospheric CO2 | Geology | GeoScienceWorld
Article history
Abstract
Current atmospheric CO2 concentration is known to be higher than it has been during the past ∼800 k.y. of Earth history, based on direct measurement of CO2 within ice cores. A comparison to the more ancient past is complicated by a deficit of CO2 proxies that may be applied across very long spans of geologic time. Here, we present a new CO2 record across the past 23 m.y. of Earth history based on the δ13C value of terrestrial C3 plant remains, using a method applicable to the entire ∼400 m.y. history of C3 photosynthesis on land. Across the past 23 m.y., CO2 likely ranged between ∼230 ppmv and 350 ppmv (68% confidence interval: ∼170–540 ppm). CO2 was found to be highest during the early and middle Miocene and likely below present-day levels during the middle Pliocene (84th percentile: ∼400 ppmv). These data suggest present-day CO2 (412 ppmv) exceeds the highest levels that Earth experienced at least since the Miocene, further highlighting the present-day disruption of long-established CO2 trends within Earth’s atmosphere.A 23 m.y. record of low atmospheric CO2 | Geology | GeoScienceWorld
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