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DOE OSTI · 2581375

Discussion: Presentation of Atmospheric 14 C O2 data

Schwartz, Stephen (ORCID:000000016288310X)·Hua, Quan (ORCID:0000000301798539)·Andrews, David (ORCID:0000000187901474)·Keeling, Ralph (ORCID:0000000297492253)·Lehman, Scott (ORCID:0000000288659584)·Turnbull, Jocelyn (ORCID:0000000203069658)·Reimer, Paula (ORCID:0000000192382146)·Miller, John (ORCID:0000000186301610)·Meijer, Harro (ORCID:0000000187445632)
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Abstract

ABSTRACT Observations of radiocarbon ( 14 C) in Earth’s atmosphere and other carbon reservoirs are important to quantify exchanges of CO 2 between reservoirs. The amount of 14 C is commonly reported in the so-called Delta notation, i.e., Δ 14 C, the decay- and fractionation-corrected departure of the ratio of 14 C to total C from that ratio in an absolute international standard; this Delta notation permits direct comparison of 14 C/C ratios in the several reservoirs. However, as Δ 14 C of atmospheric CO 2 , Δ 14 CO 2 is based on the ratio of 14 CO 2 to total atmospheric CO 2 , its value can and does change not just because of change in the amount of atmospheric 14 CO 2 but also because of change in the amount of total atmospheric CO 2 , complicating ascription of change in Δ 14 CO 2 to change in one or the other quantity. Here we suggest that presentation of atmospheric 14 CO 2 amount as mole fraction relative to dry air (moles of 14 CO 2 per moles of dry air in Earth’s atmosphere), or as moles or molecules of 14 CO 2 in Earth’s atmosphere, all readily calculated from Δ 14 CO 2 and the amount of atmospheric CO 2 (with slight dependence on δ 13 CO 2 ), complements presentation only as Δ 14 CO 2 , and can provide valuable insight into the evolving budget and distribution of atmospheric 14 CO 2 .

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Schwartz, Stephen (ORCID:000000016288310X), Hua, Quan (ORCID:0000000301798539), Andrews, David (ORCID:0000000187901474), Keeling, Ralph (ORCID:0000000297492253), Lehman, Scott (ORCID:0000000288659584), Turnbull, Jocelyn (ORCID:0000000203069658), Reimer, Paula (ORCID:0000000192382146), Miller, John (ORCID:0000000186301610), Meijer, Harro (ORCID:0000000187445632). 2024-03-27. Discussion: Presentation of Atmospheric 14 C O2 data. https://doi.org/10.1017/rdc.2024.27

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