Thanks to notification from and email conversations with the lead author Denica Bozhinova of the paper "Simulating the integrated summertime Δ14CO2 signature from anthropogenic emissions over Western Europe, the claim made in the original Hockey Schtick post that ~3.75% of background atmospheric CO2 is man-made from burning of fossil fuels is hereby retracted due to a misinterpretation of the paper. The author has clarified that her paper does not address the mole fraction or concentration of CO2 of fossil fuel origin present in background levels of CO2, it addresses the mole fraction or concentration of CO2 of fossil fuel origin of recent emissions only.
Regarding the conclusion of the paper which states in part
"...the 6-month average CO2ff concentrations in the lower 1 km of the atmosphere across Western Europe are between 1 to 18 ppm."
I asked the author via email
"My understanding now is that CO2ff in your paper is referring to the concentration of CO2ff that is above background levels of CO2 rather than absolute concentrations of CO2ff, thus please confirm my understanding is correct that your conclusion may be stated as "...the 6-month average [CO2 concentrations of fossil-fuel origin that are above background concentrations of CO2] in the lower 1 km of the atmosphere across Western Europe are between 1 to 18 ppm," and that it is not possible to determine from your data the absolute concentrations of CO2 of fossil fuel origin [background + recently added]."and the lead author has replied in her 3rd email today
"Your last paragraph describing the complicated fossil fuel/background relationship used in study is in fact totally correct. I am sorry that probably it is not going to be of use for your draft, however I am certain that there are other studies that investigate the issue you were trying to address."I apologize for my misinterpretation of the paper, putting the post in draft mode during email conversations back and forth with the author, and all subsequent confusion which I caused. I'd like to thank lead author Denica Bozhinova for her kind and detailed emails [portions below], apologize for the time she has spent correcting my misinterpretation and that of several others in the blogosphere, and wish her all the best in her future career and research.
Original post follows with
According to the authors,
We find that the average gradients of fossil fuel CO2 in the lower 1200 meters of the atmosphere are close to 15 ppm at a 12 km × 12 km horizontal resolution.
Full paper open access:
Atmos. Chem. Phys., 14, 7273-7290, 2014
1Meteorology and Air Quality Group, Wageningen University, the Netherlands
2Institute for Marine and Atmospheric Research Utrecht, Utrecht, the Netherlands
3Centre for Isotope Research, University of Groningen, Groningen, the Netherlands
Abstract. Radiocarbon dioxide (14CO2, reported in Δ14CO2) can be used to determine the fossil fuel CO2 addition to the atmosphere, since fossil fuel CO2 no longer contains any 14C. After the release of CO2 at the source, atmospheric transport causes dilution of strong local signals into the background and detectable gradients of Δ14CO2 only remain in areas with high fossil fuel emissions. This fossil fuel signal can moreover be partially masked by the enriching effect that anthropogenic emissions of 14CO2 from the nuclear industry have on the atmospheric Δ14CO2 signature. In this paper, we investigate the regional gradients in 14CO2 over the European continent and quantify the effect of the emissions from nuclear industry. We simulate the emissions and transport of fossil fuel CO2and nuclear 14CO2 for Western Europe using the Weather Research and Forecast model (WRF-Chem) for a period covering 6 summer months in 2008. We evaluate the expected CO2 gradients and the resulting Δ14CO2 in simulated integrated air samples over this period, as well as in simulated plant samples.
We find that the average gradients of fossil fuel CO2 in the lower 1200 m of the atmosphere are close to 15 ppm at a 12 km × 12 km horizontal resolution. The nuclear influence on Δ14CO2 signatures varies considerably over the domain and for large areas in France and the UK it can range from 20 to more than 500% of the influence of fossil fuel emissions. Our simulations suggest that the resulting gradients in Δ14CO2 are well captured in plant samples, but due to their time-varying uptake of CO2, their signature can be different with over 3‰ from the atmospheric samples in some regions. We conclude that the framework presented will be well-suited for the interpretation of actual air and plant 14CO2 samples.
Excerpts from the conclusions:
In this work, we demonstrated the ability of our modeling
framework to simulate the atmospheric transport of CO2
and consequently the atmospheric 114CO2 signature in integrated
air and plant samples in Western Europe. Based on
our results we reach the following conclusions.
1. Simulated spatial gradients of 114CO2 are of measurable
size and the 6-month average CO2ff [CO2 from the burning of
fossil fuels] concentrations in the lower 1 km of the atmosphere
across Western Europe are between 1 to 18 ppm.
2. Enrichment by 14CO2 from nuclear sources can partly
mask the Suess effect close to nuclear emissions, particularly
in large parts of UK and northwestern France.
This is consistent with previous studies (Graven and
Gruber, 2011) and we show that in these regions the
strength of the nuclear influence can exceed the influence
from fossil fuel emissions.
3. The simulated plant 114CO2 signatures show spatial
gradients consistent with the simulated atmospheric
gradients. Plant growth variability induces differences
between the simulated plant and the daytime atmospheric
mean for the period of growth, of a magnitude
that is mostly within the measurement precision of
±2 ‰, but can be up to ±7‰ in some areas.
4. Integrated 114CO2 samples from areas outside the immediate
enrichment area of nuclear emission sources
are not sensitive to occasional advection of enriched air
due to their long absorption period. However, to properly
account for the nuclear enrichment term on smaller
time scales, improvements in temporal profiles of nuclear
emissions are needed.
5. New 114CO2 sampling strategies should take advantage
of different sampling methods, as their combined
use will provide a more comprehensive picture of the
atmospheric 114CO2 temporal and spatial distribution.
Additional details from selected excerpts of email conversations with the lead author Denica Bozhinova:
From the author:
...The background term in our equations, as I tried to explain in my
reply on the Hockey Schtick, includes all the CO2 and its respective
∆bg signature that has been in the atmosphere before our simulation
start or has been transported into our modeled area from outside
during the simulation. As such it combines all the previously emitted
and transported anthropogenic and natural CO2 and in our study we
cannot distinguish the fractions that can be attributed to the
different sources in this term. It defines the starting CO2 level in
our modeled area and how the transport from outside would affect it.
All the other terms (biospheric respiration, uptake, fossil fuel and
nuclear 14CO2 emissions) are implemented with surface fluxes only
(described explicitly in our section 2.2). That means that they are
the recently added or removed quantities with a particular source/sink
within the time and space of our simulation. And as such when we
average the results for the 6 months we obtain a spacial map (for
CO2ff much alike the one shown in Figure 4a, except there the scale is
in ∆14CO2) in which for the lower 1 km of the atmosphere the average
concentrations of CO2ff are between 1 and 18 ppm AND at the same time
the average (spatial, since we average over the time) gradients in the
concentrations of the CO2ff in the lower 1200 km are about 15 ppm.
...My understanding now is that CO2ff in your paper is referring to the concentration of CO2ff that is above background levels of CO2 rather than absolute concentrations of CO2ff, thus please confirm my understanding is correct that your conclusion may be stated as "...the 6-month average [CO2 concentrations of fossil-fuel origin that are above background concentrations of CO2] in the lower 1 km of the atmosphere across Western Europe are between 1 to 18 ppm.", and that it is not possible to determine from your data the absolute concentrations of CO2 of fossil fuel origin [background + recently added].
Thanks once again for your assistance and please accept my sincere apologies.
From the author:
Thank you for the apology and in my turn, I apologize if I have been a
bit too harsh in my response to you. Truth is, this is the first time
when I had to deal with so much publicity regarding one of my works
and it was very difficult to read the people's opinions of the article
and its scientific merit, even when I realized that they were based
mostly on the review only. As a scientist one must learn how to take
criticism to one's work, but it doesn't necessary mean it is easier to
I would also like to thank you for the general attempt to translate
scientific words and work for the wider audience. Even if the review
of my particular article was a bad example, a misstep, such work is
crucial for the future of science as communication between scientists
and the general public is a really important and extremely difficult
task. One that most of the scientists can't do themselves either or
are really poor at.
Your last paragraph describing the complicated fossil fuel/background
relationship used in study is in fact totally correct. I am sorry that
probably it is not going to be of use for your draft, however I am
certain that there are other studies that investigate the issue you
were trying to address.
I did mean that most authors would be eager to reply to questions
about their work, especially immediately after an article has come out
of publication. This is probably especially true for young researchers
like me (not a Dr. yet), for which such contact provides the almost
priceless feedback that their work is relevant or interesting for
someone else than just other scientists.
Dept. of Meteorology and Air Quality
Wageningen University and Research Center
Building 100 (Lumen), Room A1.16
Droevendaalsesteeg 3 6708 PB
P.O. Box 47, 6700 AA, Wageningen, The Netherlands