<p>The NOAA has used carbon-14 to identify <em>local sources</em> of anthropogenic carbon dioxide, which would suffer less interference from  factors acting elsewhere around the globe, such as nuclear testing. The map below, showing yellow and red areas where the near-surface atmosphere is depleted of carbon-14, matches with the most densely populated and heavily industrialized areas of North America.</p>
<p><a href="https://research.noaa.gov/article/ArtMID/587/ArticleID/2631/Fingerprinting-fossil-fuel-emissions-with-carbon-14" rel="nofollow noreferrer">Reference and figure source</a></p>
<p><a href="https://i.sstatic.net/Gz5At.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/Gz5At.png" alt="enter image description here" /></a></p>

CC BY-SA 4.0
2022-05-24T11:40:29.693Z
Thanks that looks interesting, but it is just showing the locations of anthropogenic sources, rather than the anthropogenic contribution to the post-industrial rise in CO2 (which is not the same as the proportion of CO2 directly from anthropogenic sources, because of the large exchange fluxes between reservoirs).
Dikran Marsupial
CC BY-SA 4.0
2022-05-24T10:42:36.927Z
2022-05-24T10:42:36.927Z
Oscar Lanzi
<p>There have been several papers [failures of the review process] that have argued that the post-industrial rise in atmospheric <span class="math-container">$\ce{CO2}$</span> is primarily a natural phenomenon, or have sought to minimise the anthropogenic contribution.  This is a recent example:</p>
<blockquote>
<p>K. Skrable, G. Chabot and Clayton French, &quot;World Atmospheric CO2, Its
14C Specific Activity, Non-fossil Component, Anthropogenic Fossil
Component, and Emissions (1750–2018)&quot;, Health Physics: February 2022 -
Volume 122 - Issue 2 - p 291-305 doi: <a href="https://dx.doi.org/10.1097/HP.0000000000001485" rel="nofollow noreferrer">10.1097/HP.0000000000001485</a></p>
<p><strong>Abstract</strong></p>
<p>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.</p>
</blockquote>
<hr />
<p>Fossil <span class="math-container">$\ce{CO2}$</span> will be essentially depleted of <span class="math-container">$^{14}\ce{C}$</span> as it has been in the lithosphere for millions of years, far longer than the half-life of <span class="math-container">$^{14}\ce{C}$</span>, so obviously fossil fuel emissions will have had an effect on the <em>relative</em> concentrations of 14C in the atmosphere.  However, that is likely obscured by the <span class="math-container">$^{14}\ce{C}$</span> from nuclear testing in the 1950s and 60s.  Also when <span class="math-container">$^{14}\ce{C}$</span> is removed from the atmosphere, the amount of CO2 has not been reduced, it is just that the <span class="math-container">$^{14}\ce{C}$</span> from the atmosphere has been exchanged with <span class="math-container">$\ce{C}$</span> from the other reservoirs, at the mixing ratio found in those reservoirs.  This means it is more informative of the residence time (the average time a molecule of CO2 remains in the atmosphere before being exchanged) than the adjustment time (the time scale on which atmospheric <span class="math-container">$\ce{CO2}$</span> decays towards it's equilibrium value).</p>
<p><span class="math-container">$\color{red}{\star}$</span> Is it possible to reliably infer the anthropogenic contribution to the post-industrial rise in atmospheric <span class="math-container">$\ce{CO2}$</span> from <span class="math-container">$^{14}\ce{C}$</span> observations?</p>
<p>A reference to a paper where this is demonstrated would be greatly appreciated!</p>

<climate-change><carbon-cycle><anthropogenic>
Is it possible to reliably infer the anthropogenic contribution to the post-industrial rise in $\ce{CO2}$ from $^{14}\ce{C}$ observations?
Dikran Marsupial
# Is it possible to reliably infer the anthropogenic contribution to the post-industrial rise in $\ce{CO2}$ from $^{14}\ce{C}$ observations?

(Asked by: username_0 on 2022-05-14)

There have been several papers [failures of the review process] that have argued that the post-industrial rise in atmospheric $\ce{CO2}$ is primarily a natural phenomenon, or have sought to minimise the anthropogenic contribution. This is a recent example:

> K. Skrable, G. Chabot and Clayton French, "World Atmospheric CO2, Its
> 14C Specific Activity, Non-fossil Component, Anthropogenic Fossil
> Component, and Emissions (1750–2018)", Health Physics: February 2022 -
> Volume 122 - Issue 2 - p 291-305 doi: [10.1097/HP.0000000000001485](https://dx.doi.org/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.

---

Fossil $\ce{CO2}$ will be essentially depleted of $^{14}\ce{C}$ as it has been in the lithosphere for millions of years, far longer than the half-life of $^{14}\ce{C}$, so obviously fossil fuel emissions will have had an effect on the *relative* concentrations of 14C in the atmosphere. However, that is likely obscured by the $^{14}\ce{C}$ from nuclear testing in the 1950s and 60s. Also when $^{14}\ce{C}$ is removed from the atmosphere, the amount of CO2 has not been reduced, it is just that the $^{14}\ce{C}$ from the atmosphere has been exchanged with $\ce{C}$ from the other reservoirs, at the mixing ratio found in those reservoirs. This means it is more informative of the residence time (the average time a molecule of CO2 remains in the atmosphere before being exchanged) than the adjustment time (the time scale on which atmospheric $\ce{CO2}$ decays towards it's equilibrium value).

$\color{red}{\star}$ Is it possible to reliably infer the anthropogenic contribution to the post-industrial rise in atmospheric $\ce{CO2}$ from $^{14}\ce{C}$ observations?

A reference to a paper where this is demonstrated would be greatly appreciated!

**Tags:** climate-change, carbon-cycle, anthropogenic


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## 1 answers

### Answer by username_1 on 2022-05-24. Score: 3

The NOAA has used carbon-14 to identify *local sources* of anthropogenic carbon dioxide, which would suffer less interference from factors acting elsewhere around the globe, such as nuclear testing. The map below, showing yellow and red areas where the near-surface atmosphere is depleted of carbon-14, matches with the most densely populated and heavily industrialized areas of North America.

[Reference and figure source](https://research.noaa.gov/article/ArtMID/587/ArticleID/2631/Fingerprinting-fossil-fuel-emissions-with-carbon-14)

[![enter image description here](https://i.sstatic.net/Gz5At.png)](https://i.sstatic.net/Gz5At.png)

> **Comments:**
> **username_0**: Thanks that looks interesting, but it is just showing the locations of anthropogenic sources, rather than the anthropogenic contribution to the post-industrial rise in CO2 (which is not the same as the proportion of CO2 directly from anthropogenic sources, because of the large exchange fluxes between reservoirs).  

---

