A new paper in HEALTH PHYSICS asks this question.

World Atmospheric CO₂, Its ¹⁴C Specific Activity, Non-fossil Component, Anthropogenic Fossil Component, and Emissions (1750–2018)

Skrable, Kenneth; Chabot, George; French, Clayton¹

¹University of Massachusetts Lowell, 1 University Avenue, Lowell, MA 01854.

Health Physics: February 2022 – Volume 122 – Issue 2 – p 291-305

doi: 10.1097/HP.0000000000001485

Abstract

After 1750 and the onset of the industrial revolution, the anthropogenic fossil component and the non-fossil component in the total atmospheric CO₂ concentration, C(t), began to increase. Despite the lack of knowledge of these two components, claims that all or most of the increase in C(t) since 1800 has been due to the anthropogenic fossil component have continued since they began in 1960 with “Keeling Curve: Increase in CO₂ from burning fossil fuel.” Data and plots of annual anthropogenic fossil CO₂ emissions and concentrations, C(t), published by the Energy Information Administration, are expanded in this paper. Additions include annual mean values in 1750 through 2018 of the ¹⁴C specific activity, concentrations of the two components, and their changes from values in 1750. The specific activity of ¹⁴C in the atmosphere gets reduced by a dilution effect when fossil CO₂, which is devoid of ¹⁴C, enters the atmosphere. We have used the results of this effect to quantify the two components. All results covering the period from 1750 through 2018 are listed in a table and plotted in figures. These results negate claims that the increase in C(t) since 1800 has been dominated by the increase of the anthropogenic fossil component. We determined that in 2018, atmospheric anthropogenic fossil CO₂ represented 23% of the total emissions since 1750 with the remaining 77% in the exchange reservoirs. Our results show that the percentage of the total CO₂ due to the use of fossil fuels from 1750 to 2018 increased from 0% in 1750 to 12% in 2018, much too low to be the cause of global warming.

INTRODUCTION

At an elapsed time of t years since 1750 (the start of the industrial revolution with the onset of the use of fossil fuels in vehicles and power plants), atmospheric CO₂ concentrations, C(t), increased along with increases in temperatures. Atmospheric measurements of C(t) were not available until 1958 at the Mauna Loa, HI, observatory of the National Oceanic and Atmospheric Administration (NOAA), which has provided the longest record of atmospheric measurements of the total CO₂ initiated by Charles Keeling in 1958 at the Mauna Loa observatory (Keeling 1960). Based on our knowledge, the anthropogenic fossil component, C_F(t), and non-fossil component, C_NF(t), in C(t) have never been estimated by NOAA at its observatories or at any other observatory from atmospheric measurements of CO₂. Despite the lack of knowledge of the components of C(t), claims have been made in the scientific literature (^{CSIRO 2014}; ^{Rubino et al. 2013}, ²⁰¹⁹) that all or most of the increase in C(t) since 1800 has been due to the anthropogenic fossil component, C_F(t).

Other atmospheric measurements of C(t) began in 2003 at the NOAA observatory in Niwot Ridge, including measurements of the three isotopes of carbon: ¹²C, ¹³C, and ¹⁴C. Carbon-14 is a radioactive isotope of carbon having a half-life of 5,730 y. Carbon-14 atoms are produced in the atmosphere by interactions of cosmic rays, and they have reached an essentially constant steady state activity, i.e., disintegration rate, in the total world environment (^{Eisenbud and Gesell 1997}). The age of fossil fuels is much longer than the 5,730 y half-life of the ¹⁴C radioactive isotope; consequently, fossil fuels are devoid of the ¹⁴C isotope. When the anthropogenic fossil component of CO₂ is released to the atmosphere, the specific activity of ¹⁴C_,S(t) in C(t), decreases. The units of S(t) used in this paper are disintegrations per minute per gram of carbon abbreviated as dpm (gC)⁻¹, the common units used in ¹⁴C dating. The ratio R_S13 of the (¹³C/¹²C) atoms and the ratio R_S14 of the (¹⁴C/¹²C) atoms at the Niwot Ridge observatory are used to calculate two statistics designated respectively in this paper as d13C and D14C, both of which are said to decrease when the anthropogenic fossil component, C_F(t), increases in the atmosphere. As discussed later in Table 1, values of the annual mean specific activity, S(t), are calculated in this paper from annual mean values of the D14C statistic.

Both the d13C and D14C statistics represent 1,000 times the relative deviations of their respective (¹³C/¹²C) and (¹⁴C /¹²C) atom ratios from those of a 1950 standard (^{Karlen et al. 1964}) when expressed in per mil, given by the symbol ‰. This magnification increases their underlying relative deviations and slopes in plots by a factor 1,000. While such amplification techniques often are useful for displaying very small changes in quantities of interest, the interpretation of such magnified changes must be attended with some care. In the cases of concern here, the resultant steep slopes in plots likely have led persons throughout the world to conclude that the anthropogenic component has dominated the increase of CO₂ and caused global warming. We believe that both statistics have been misused to validate the anthropogenic fossil component, C_F(t), as the major cause of the increase of C(t).

Global carbon cycle and its effect on CO₂ quantities

The global carbon cycle for CO₂ is described by the Energy Information Administration (EIA 2020). Natural, two-way exchanges of CO₂ occur between the atmosphere and its two exchange reservoirs, the oceans and terrestrial biosphere. Two-way exchanges with the atmosphere also occur from changes in land use. The ocean is the largest reservoir of CO₂, and it contains 50 times that for the atmosphere and 19 times that for the terrestrial biosphere (^{Water Encyclopedia 2005}). All of the two way exchanges are considered in this paper to be comprised of both the non-fossil component and the anthropogenic fossil component. Annual changes, DC_NF(t) in C_NF(t), in the atmosphere relative to the 1750 initial value, C(0), can be positive or negative depending on the net flow of CO₂ between the atmosphere and its exchange reservoirs as well as on land use changes. A one-way pathway of anthropogenic fossil CO₂ into the atmosphere from fossil fuel combustion and industrial fuel processes since 1750 is represented by annual emissions, DE(t), of anthropogenic fossil CO₂ to the atmosphere, which have been increasing each year since 1750. These emissions over time t result in increasing annual mean anthropogenic fossil concentrations, C_F(t), that result in specific activities, S(t), of ¹⁴C in C(t) that are increasingly lower than the initial value, S(0). This dilution of S(0) in C(0) in 1750 by the presence of C_F(t) in C(t) corresponds to what is described as the Suess effect (^{Suess et al. 1967}).

Read the full unrestricted paper here.