Correcting an Error in Some Interpretations of Atmospheric <sup>14</sup>C Data

Abstract

The variable "∆ 14 C", commonly used in radiocarbon dating and tracing applications to quantify 14 C levels, is a measure of the ratio of the radioisotope 14 C to other carbon in a sample. After atmospheric nuclear testing in the 1950's and 1960's nearly doubled atmospheric 14 C, the later evolution of ∆ 14 C allowed insights into the dynamics of carbon exchange between the atmosphere and terrestrial and marine sinks. But a few authors without backgrounds in isotope measurements have confused ∆ 14 C with excess 14 C concentration. They erroneously interpret the present recovery of ∆ 14 C to near its pre bomb test value as evidence that atmospheric 14 C concentration has returned to its earlier value. From this they reach further incorrect conclusions about the fate of anthropogenic CO 2 introduced into the atmosphere by fossil fuel burning. An estimate of the true time dependence of atmospheric 14 C concentration over the past century, calculated from averaged atmospheric ∆ 14 C and CO 2 data is presented. The data show that 14 C concentrations remain over 30% above 1950 values, and have begun to increase, even as ∆ 14 C continues to fall. This confirms the prediction of a conventional model of the carbon cycle. The unconventional models of carbon dynamics motivated by the mistake, on the other hand, are excluded by the properly interpreted 14 C data.

DISCUSSION: PRESENTATION OF ATMOSPHERIC 14CO2 DATA

“…In contrast to Δ 14 CO 2 , x 14CO2 reached a minimum around 2000, increasing thereafter. This contrast in the time series of the relative and absolute amounts of Δ 14 CO 2 versus x 14CO2 over this time period, presented recently also by Andrews (2020) and Andrews and Tans (2022), highlights the distinction between these two measures of the amount of 14 CO 2 in Earth’s atmosphere.…”

Comments on Skrable et al. (2022)

“…2 of total content or total activity are only occasionally found, as in Caldeira et al (1998). Skrable et al are not the first to have been tripped up by this (Andrews 2020). Skrable et al (2022) quote Wikipedia as saying the total atmospheric content of 14 C is 140 PBq.…”