THIS POST IS A CRITICAL REVIEW OF CLAIMS IN AN EOS ARTICLE THAT FOSSIL FUEL EMISSIONS CAN BE TRACKED BY MEASURING THE C14 FRACTION IN ATMOSPHERIC CO2  [LINK TO EOS ARTICLE]  

PART-1: WHAT THE EOS ARTICLE SAYS

1. Radioactive Bookkeeping of Carbon Emissions: A new sampling method uses carbon-14 to single out which carbon dioxide molecules in the atmosphere derive from fossil fuels. The method could help track emissions goals for climate mitigation.
2. Estimating how much carbon dioxide (CO2) is released by burning fossil fuels has traditionally resembled a large-scale mathematics test. Accurately summing up the number and types of vehicles on the road, evaluating current emissions standards, adding in emissions from power plants, and accounting for efficiencies require detailed calculations and data.
3. Since the 1990s, scientists at the Environmental Protection Agency (EPA) have been estimating emissions using these complex accounting procedures. Now, a group of researchers has taken a different approach: measuring atmospheric CO2 directly. But first, they had to separate the fossil fuel–derived carbon from natural sources such as volcanic emissions. Using carbon-14 as a marker, the team parsed out CO2 sources, providing monthly to annual measurements of fossil fuel emissions.
4. They found CO2 fossil fuel emissions were about 5% higher than EPA estimates. They note their approach can give more frequent and focused measurements, which is useful in policy and climate modeling research.
5. Greenhouse gas emissions are a direct driver of climate change. International treaties like the 2015 Paris Agreement and the 1992 United Nations Framework Convention on Climate Change (UNFCCC) treaty have specific targets for reducing greenhouse gas emissions.
6. Since the UNFCCC treaty, the EPA has used a bottom-up approach to estimate emissions. They look at activities that produce CO2: use of cars, trucks, planes, power plants, and heating. Then they look at the emission factor, or how much CO2 is produced by each activity. In the end, researchers multiply activities and emission factors and sum up everything to get an estimate of CO2 emissions for the country. “These are very detailed statistics,” said Basu, adding that EPA researchers do a good job of trying to capture all ways CO2 is emitted. “This is a very hard job, but at the end of the day, it’s an accounting process,” he said. “It’s entirely possible to miss something.” For example, using the wrong emission factor—such as an outdated fuel efficiency for a car—can skew estimates.
7. Basu and his colleagues decided to do a top-down approach and take direct measurements of CO2 in the atmosphere. “If you just look at the atmospheric data, because everything that’s emitted has to show up in the atmosphere, you can construct an independent estimate of [emissions],” explained Basu.
8. The team has been setting up a sampling network across the country for almost 2 decades. The geographic coverage and number of stations make a “robust” sampling of total U.S. emissions, said Basu.
9. Parsing Out Carbon Dioxide: “Now we have great carbon isotope data that we can use to figure out how much fossil fuel emissions are coming from the U.S.”Atmospheric measurements of CO2 take all sources into account: those from fossil fuel combustion and carbon emissions from other sources. The trick is to figure out what part of the total emissions comes from fossil fuels.
10. Fossil fuels are made of carbon-based material (ancient plants and animals) that is millions of years old. The carbon in fossil fuels has long since stopped the process of radioactive decay. When the carbon gets to a fossil fuel state, it’s completely devoid of carbon-14. Carbon-14 is the only known radioactive isotope of carbon. Separating it out means the remaining carbon in an air sample is fossil fuel derived.
11. Now we have great carbon isotope data that we can use to figure out how much fossil fuel emissions are coming from the U.S. from the atmospheric data,” said Eri Saikawa, an atmospheric chemist at Emory University who was not involved with the study. That is extremely fascinating.
12. The team measured 1,000 air samples from 2010. Using a dual-tracer inverse modeling framework and measurements, the team found their top-down estimate was 5% larger than the EPA’s estimate: 1,653 teragrams of carbon per year from fossil fuels compared to about 1,581 teragrams of carbon per year.
13. Although there was a 5% increase using the top-down method, Saikawa said that statistically, it was not much different than the bottom-up approach. “Actually, the bottom-up and the top-down [methods] are overlapping,” she noted. “I thought that was a pretty good result.” Saikawa noted both methods have uncertainties. “Nothing is perfect,” she said.
14. But I think having both sets to work with to see how we can improve is very important. I think that’s the most exciting point,” said Saikawa. “We might actually be able to reduce the uncertainty that we currently have, in terms of the CO2 emissions estimates.
15. The team wants to expand their work to include multiple years to note any trends in estimates or emissions over time. Accurately estimating the amount of CO2 emissions is important for long-term climate policy and planning, especially related to the Paris Agreement.
16. The thing is, even though we as a country might be thinking of withdrawing from the Paris accord, there are several entities within this country who have decided, ‘No, we are going to have [our own trajectories] anyway,’” said Basu. “But in order to independently verify those trajectories using our atmospheric measurement–based method, we need more measurements.
17. I hope that we can use this type of great work as a way to increase the network [of sampling] and then make sure that we have a good set of measurements available,” said Saikawa. “I would love for them to be able to get data not at the national level, but then at the state level,” she said. “That could potentially show a much more difference in a specific region.

PART-2:  CRITICAL COMMENTARY

1. The principal finding of the paper:  A novel fossil fuel emissions estimation procedure is proposed. It consists of measuring the CO2 concentration=x1 of a sample air and also the fraction of the CO2 that contains no-C14=x2. The fraction that contains no C14 is assumed to be from fossil fuels. Thus, x1*x2*(the total mass of the atmosphere) = the total fossil fuel emissions currently in the atmosphere based on the assumption that the only source of C14-free CO2 is fossil fuels.
2. The difference between successive measurements year to year is then proposed as the measurement metric that will yield the figures for annual fossil fuel emissions. This measurement is thought to be of greater precision and with less uncertainty than the current survey methods used by the EPA. 
3. About Anthropogenic Global Warming  (AGW):  The benefits of fossil fuels come with the fear that carbon dioxide emissions from fossil fuels taken from deep below the surface of the earth are an extraneous perturbation of the delicately balanced surface-atmosphere carbon cycle. The long term consequences of this perturbation could be devastating in terms of climate change by way of altered atmospheric composition and its greenhouse effect. Our use of fossil fuels has risen exponentially since the Industrial Revolution and concurrently, atmospheric CO2 has risen steadily from 280 ppm to over 400 ppm. At the same time there has been a long term warming trend in global surface temperature. The science of anthropogenic global warming and climate change (AGW) is based on the assumption that these concurrent changes are causally related such that all of these changes are ultimately driven by fossil fuel emissions. 
4. A cornerstone of AGW theory is that the observed increase in atmospheric CO2 since the Industrial Revolution derives completely from CO2 generated by the combustion of fossil fuels. One line of empirical evidence for this relationship is proposed in terms of changes in the Radiocarbon fraction of atmospheric CO2 (Suess, 1953) (Levin, 2000) (Stuiver, 1981) (IPCC, 2014).
5. About Radiocarbon: Carbon-14 forms naturally in the atmosphere by the action of cosmic rays on nitrogen but being radioactive, once formed, 14C decays exponentially with a half life of 5,700 years. Radioactive decay is balanced by new cosmogenic synthesis and at equilibrium roughly one part per trillion of atmospheric carbon dioxide is made with radiocarbon. The equilibrium radiocarbon ratio is not constant but varies over long periods of time. This variation is the reason that radiocarbon dating must be calibrated against the prevailing carbon-14 ratio at the time that the organic matter being tested had died {Reference: My paper on Uncertainty in Radiocarbon Dating [LINK] .
6. About Radiocarbon Dating: All carbon life-forms contain the prevailing equilibrium ratio of atmospheric carbon-14 as long as they are alive and their bodily carbon is being replenished. When they die, however, the radiocarbon fraction in their body begins an exponential decay and this fraction may be used to determine how long dead matter has been dead. This dating procedure, properly calibrated for the prevailing equilibrium carbon-14 ratio at the time of death, serves a useful purpose in establishing the age of pottery-based strata in archaeological excavations.
7. The relevance of these relationships in climate science:  derives from the idea that fossil fuels are dead matter that has been dead for millions of years and therefore contain no radiocarbon. It is thus postulated that the release of fossil fuel emissions into the atmosphere reduces the radiocarbon portion of atmospheric carbon dioxide and that therefore the degree of such radiocarbon dilution serves as a measure of the contribution of fossil fuel emissions to the observed increase in atmospheric carbon dioxide (Stuiver, 1981) (Suess, 1953) (Revelle, 1957) (Tans, 1979).
8. The Stuiver and Quay paper (Stuiver, 1981) presents carbon-14 measurements in tree rings of two Douglas Firs in the Pacific Northwest that grew from 1815 to 1975. The now famous graphic representation of these data taken from their paper is reproduced below. The figure shows a fairly steady 14C ratio from 1820 to 1900 and then a steep decline of about 20% from 1900 to 1950. The authors attributed the decline to dilution of natural atmospheric carbon dioxide with CO2 from fossil fuels that contain no 14C. These data are the foundation of the generally accepted idea that the observed increase in atmospheric CO2 since the Industrial Revolution is derived from fossil fuel emissions (IPCC, 2007) (IPCC, 2014).
9. The flaw in Stuiver and Quay: However, as shown in a related post, the Stuiver and Quay study contains a fatal mass balance flaw. The Stuiver and Quay tree ring data imply that from 1900 to 1950, fossil fuel emissions, being free of radiocarbon, caused the radiocarbon portion of atmospheric CO2 to decline by 20%. In terms of fossil fuel emissions during this period , a total of 50 gigatons of carbon (GTC) or about 180 gigatons of CO2 were released into the atmosphere. At the same time atmospheric CO2 concentration rose 15.6 ppm or 5.38% from 296 ppm to 311 ppm. The increase of 15.6 ppm is equivalent to 33 GTC or 120 gigatons of CO2. Even if all of the emissions had gone into increasing atmospheric CO2 concentration, the dilution of 14C could not have been more than 8%. The dilution of 20% claimed by Stuiver and Quay is an impossibility in this context. These results imply that the Stuiver and Quay data do not have a simple interpretation in terms of dilution of atmospheric CO2 with fossil fuel emissions and therefore do not provide evidence that rising atmospheric CO2 concentration can be explained in terms of fossil fuel emissions.
   
10. The value of these pre-bomb data is that almost immediately following the end of their sample period in 1950, atmospheric tests of nuclear weapons sharply increased the 14C ratio in atmospheric carbon dioxide and following the cessation of such tests after the nuclear test ban treaty the 14C ratio began a natural exponential decay. The so called bomb spike data in shown below are taken from the measuring station in Wellington, NZ for the period 1955 to 1993. 
11. It would be difficult in the context of the bomb spike shown above to detect the effect of dilution by fossil fuel emissions. Nevertheless, several measurement stations were set up around the world to measure the 14C ratio in atmospheric carbon dioxide. These direct measurements provided by NOAA/ESRL are shown below. It is claimed that these data support the Stuiver and Quay findings and prove that the observed increase in atmospheric CO2 is attributable to fossil fuel emissions (NOAA/ESRL, 2010).
12. After the nuclear test ban treaty in 1963, atmospheric 14C began its expected  exponential decay. The decay curve is provided by The Wellington 14C measuring station and it is shown in the chart below. Because of the natural decay of the bomb spike, the decline in atmospheric 14C measured by NOAA cannot be assumed to be caused by dilution with fossil fuels in the post bomb spike era. Evidence is needed to attribute observed declines in atmospheric 14C to fossil fuel emissions.
13. The observed decay rate is larger than theoretical radioactive decay and this difference is thought to derive from the exchange of atmospheric and oceanic CO2 (Sherrington, 2016) (Mearns, 2014). However, the relevant point here is that the later data presented by NOAA/ESRL are consistent with the observed decay following cessation of atmospheric testing of nuclear weapons with no evidence of a response to the exponential increase in fossil fuel emissions found in the data. In that context, what we find is that the 14C decay claimed by NOAA to be caused by fossil fuel emissions is better understood as a continuation of the post bomb natural decay of 14C. This pattern is seen in the charts below where each chart refers to a single NOAA measuring station identified with acronyms as follows: PTB=Point Barrow Alaska, MLO=Mauna Loa Hawaii, KUM=Cape Kumukahi, SPO=South Pole, NIWOT=Niwot Ridge, Colorado. A tabular summary of the data is provided. 
14. In each of the charts, the NOAA station data is appended to the Wellington bomb spike decay data and what we see is that the NOAA station data exactly matches the decay curve and that match is strongly supported by high values of R-squared. This pattern suggests that the observed decline in atmospheric 14C is best understood as simply a continuation of the bomb spike decay and not as being driven by fossil fuel emissions. This conclusion is further supported by the summary table above which shows that the second half of the decay curve contains a smaller decay than the first half whereas the fossil fuel emission data show that fossil fuel emissions were higher in the second half of the study period.
15. The analysis presented above shows that the data are inconsistent with their interpretation by NOAA/ESRL/IPCC as evidence of atmospheric 14C dilution by fossil fuel emissions.
16. Yet another consideration is that it is not possible for carbon isotopic ratios to identify fossil fuel emissions as the source of the rise in atmospheric CO2 because isotopic ratios are unable to distinguish between fossil carbon and geological carbon. The proposed methodology assumes that all natural sources of carbon contain C14 and that fossil fuel emissions are unique in that it is the only source of carbon available to the atmosphere that contains no C14. This assumption is not valid because geological sources of carbon derived from the mantle are also free of C14. Most of the planet’s carbon, 99.8%, is in the mantle and core with only 0.2% in the crust where we live and where we have things like ocean, atmosphere, carbon life forms, and climate. All of this 0.2% came from the mantle through geological processes that include rifts, volcanism, mantle plumes, hydrothermal vents, and seepage. Although we tend to think of volcanism in terms of volcanoes on land, more than 80% of the world’s volcanic activity is on the ocean floor. All of these geological activities transfer pure C12 carbon from the mantle to the crust. All of our carbon on the crust, including the carbon in carbon life forms such as humans, came from the mantle. There is no C14 in the mantle. The climate science assumption that changes in atmospheric CO2 concentration derive from fossil fuel emissions is tested in three related posts at this site.
17. CONCLUSIONS: IN VIEW OF THE ARGUMENTS PRESENTED ABOVE, THE CLAIM THAT THE FLOW RATE OF FOSSIL FUEL EMISSIONS CAN BE MEASURED IN TERMS OF THEIR IMPACT ON ATMOSPHERIC 14C CONCENTRATION IS NOT CREDIBLE. 
18. Related Post#1: A test for the hypothesis that atmospheric composition is responsive to fossil fuel emissions at an annual time scale:  [LINK] . FINDINGS:  We conclude that atmospheric composition specifically in relation to the CO2 concentration is not responsive to the rate of fossil fuel emissions. This finding is inconsistent with the theory of anthropogenic global warming by way of rising atmospheric CO2 attributed to the use of fossil fuels in the industrial economy; and of the “Climate Action proposition of the UN that reducing fossil fuel emissions will moderate the rate of warming by slowing the rise of atmospheric CO2. The finding also establishes that the climate action project of creating Climate Neutral Economies, that is Economies that have no impact on atmospheric CO2, is unnecessary because the global economy is already Climate Neutral. A rationale for the inability to relate changes in atmospheric CO2 to fossil fuel emissions is described by Geologist James Edward Kamis in terms of natural geological emissions due to plate tectonics [LINK] .
19. Related Post #2: Uncertainty in Carbon Cycle Flows  [LINK]  : Here we find that in the context of large uncertainties in carbon cycle flows, it is not possible to detect the effect on atmospheric composition of relatively much smaller flows of fossil fuel emissions.