Comparison of 14CO2, CO, and SF6 as tracers for recently added fossil fuel CO2 in the atmosphere and implications for biological CO2 exchange
TL;DR: In this article, the authors used the nearly ideal tracer 14CO2 to estimate the fossil fuel CO2 enhancement in boundary layer air at two sites in New England and Colorado.
Abstract: [1] We use the nearly ideal tracer 14CO2 to estimate the fossil fuel CO2 enhancement in boundary layer air at two sites in New England and Colorado Improved Δ14C measurement precision of 16–26‰ provides fossil fuel CO2 detection capability of 08–15 ppm Using the indirect tracers CO and SF6, we obtain two additional independent estimates of the fossil fuel CO2 component, and we assess the biases in these methods with respect to the 14CO2-based estimates The SF6-based estimates vary considerably from the 14CO2-based estimates, and are at times implausibly large The CO-based estimates are less variable, but show seasonally coherent biases with respect to the 14CO2 method
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TL;DR: In this paper, high-precision atmospheric Δ 14 CO 2 records covering the last two decades are presented, and evaluated in terms of changing (radio)carbon sources and sinks, using the coarse-grid carbon cycle model GRACE.
Abstract: Global high-precision atmospheric Δ 14 CO 2 records covering the last two decades are presented, and evaluated in terms of changing (radio)carbon sources and sinks, using the coarse-grid carbon cycle model GRACE. Dedicated simulations of global trends and interhemispheric differences with respect to atmospheric CO 2 as well as δ 13 CO 2 and Δ 14 CO 2 , are shown to be in good agreement with the available observations (1940–2008). While until the 1990s the decreasing trend of Δ 14 CO 2 was governed by equilibration of the atmospheric bomb 14 C perturbation with the oceans and terrestrial biosphere, the largest perturbation today are emissions of 14 C-free fossil fuel CO 2 . This source presently depletes global atmospheric Δ 14 CO 2 by 12–14‰ yr -1 , which is partially compensated by 14 CO 2 release from the biosphere, industrial 14 C emissions and natural 14 C production. Fossil fuel emissions also drive the changing north–south gradient, showing lower Δ 14 C in the northern hemisphere only since 2002. The fossil fuel-induced north–south (and also troposphere–stratosphere) Δ 14 CO 2 gradient today also drives the tropospheric Δ 14 CO 2 seasonality through variations of air mass exchange between these atmospheric compartments. Neither the observed temporal trend nor the Δ 14 CO 2 north–south gradient may constrain global fossil fuel CO 2 emissions to better than 25%, due to large uncertainties in other components of the (radio)carbon cycle.DOI: 10.1111/j.1600-0889.2009.00446.x
282 citations
Oak Ridge National Laboratory1, DSM2, Carnegie Institution for Science3, University of Colorado Boulder4, National Oceanic and Atmospheric Administration5, Appalachian State University6, Cooperative Institute for Research in the Atmosphere7, Netherlands Environmental Assessment Agency8, CSIRO Marine and Atmospheric Research9, University of Melbourne10, International Energy Agency11
TL;DR: In this article, the emissions of carbon dioxide from fossil fuel combustion and cement production are discussed and discussed in terms of why there is concern about them; how they are calculated; the major global efforts on inventory- ing them; their global, regional, and national totals at differ- ent spatial and temporal scales; how emissions are distributed on global grids; and the uncertainties associated with these different as- pects of the emissions.
Abstract: This synthesis discusses the emissions of carbon dioxide from fossil-fuel combustion and cement production. While much is known about these emissions, there is still much that is unknown about the details surrounding these emissions. This synthesis explores our knowledge of these emissions in terms of why there is concern about them; how they are calculated; the major global efforts on inventory- ing them; their global, regional, and national totals at differ- ent spatial and temporal scales; how they are distributed on global grids (i.e., maps); how they are transported in mod- els; and the uncertainties associated with these different as- pects of the emissions. The magnitude of emissions from the combustion of fossil fuels has been almost continuously in- creasing with time since fossil fuels were first used by hu- mans. Despite events in some nations specifically designed to reduce emissions, or which have had emissions reduction as a byproduct of other events, global total emissions con- tinue their general increase with time. Global total fossil- fuel carbon dioxide emissions are known to within 10 % un- certainty (95 % confidence interval). Uncertainty on individ- ual national total fossil-fuel carbon dioxide emissions range from a few percent to more than 50 %. This manuscript con- cludes that carbon dioxide emissions from fossil-fuel com- bustion continue to increase with time and that while much is known about the overall characteristics of these emissions, much is still to be learned about the detailed characteristics of these emissions.
276 citations
Cites background from "Comparison of 14CO2, CO, and SF6 as..."
...…labor intensive, but small sets of observations have been used to partition total CO2 into fossil and terrestrial biological components (e.g., Miller et al., 2012; Graven et al., 2009; Turnbull et al., 2006) and directly estimate fossil fuel emissions (Turnbull et al., 2011; Levin et al., 2003)....
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TL;DR: A carbon flux model based on Network Environ Analysis (NEA) was developed and found to be better at revealing details from a mechanistic aspect, which is crucial for informed sustainable urban management.
Abstract: Cities are considered major contributors to global warming, where carbon emissions are highly embedded in the overall urban metabolism. To examine urban metabolic processes and emission trajectories we developed a carbon flux model based on Network Environ Analysis (NEA). The mutual interactions and control situation within the urban ecosystem of Vienna were examined, and the system-level properties of the city's carbon metabolism were assessed. Regulatory strategies to minimize carbon emissions were identified through the tracking of the possible pathways that affect these emission trajectories. Our findings suggest that indirect flows have a strong bearing on the mutual and control relationships between urban sectors. The metabolism of a city is considered self-mutualistic and sustainable only when the local and distal environments are embraced. Energy production and construction were found to be two factors with a major impact on carbon emissions, and whose regulation is only effective via ad-hoc pathways. In comparison with the original life-cycle tracking, the application of NEA was better at revealing details from a mechanistic aspect, which is crucial for informed sustainable urban management.
224 citations
TL;DR: Strong seasonal variations of the fossil fuel CO2 offsets indicate a strong seasonality of emissions but also of atmospheric dilution of ground level emissions by vertical mixing.
208 citations
TL;DR: The first attempt to estimate urban-scale CO2 from atmospheric radiocarbon measurements shows that CO2ff can be used to verify and improve emission inventories for many poorly known anthropogenic species, separate biospheric CO2, and indicates the potential to constrain CO 2ff emissions if transport uncertainties are reduced as discussed by the authors.
Abstract: . Direct quantification of fossil fuel CO2 (CO2ff) in atmospheric samples can be used to examine several carbon cycle and air quality questions. We collected in situ CO2, CO, and CH4 measurements and flask samples in the boundary layer and free troposphere over Sacramento, California, USA, during two aircraft flights over and downwind of this urban area during spring of 2009. The flask samples were analyzed for Δ14CO2 and CO2 to determine the recently added CO2ff mole fraction. A suite of greenhouse and other trace gases, including hydrocarbons and halocarbons, were measured in the same samples. Strong correlations were observed between CO2ff and numerous trace gases associated with urban emissions. From these correlations we estimate emission ratios between CO2ff and these species, and compare these with bottom-up inventory-derived estimates. Recent county level inventory estimates for carbon monoxide (CO) and benzene from the California Air Resources Board CEPAM database are in good agreement with our measured emission ratios, whereas older emissions inventories appear to overestimate emissions of these gases by a factor of two. For most other trace species, there are substantial differences (200–500%) between our measured emission ratios and those derived from available emission inventories. For the first flight, we combine in situ CO measurements with the measured CO:CO2ff emission ratio of 14 ± 2 ppbCO/ppmCO2 to derive an estimate of CO2ff mole fraction throughout this flight, and also estimate the biospheric CO2 mixing ratio (CO2bio) from the difference of total and fossil CO2. The resulting CO2bio varies dramatically from up to 8 ± 2 ppm in the urban plume to −6 ± 1 ppm in the surrounding boundary layer air. Finally, we use the in situ estimates of CO2ff mole fraction to infer total fossil fuel CO2 emissions from the Sacramento region, using a mass balance approach. The resulting emissions are uncertain to within a factor of two due to uncertainties in wind speed and boundary layer height. Nevertheless, this first attempt to estimate urban-scale CO2ff from atmospheric radiocarbon measurements shows that CO2ff can be used to verify and improve emission inventories for many poorly known anthropogenic species, separate biospheric CO2, and indicates the potential to constrain CO2ff emissions if transport uncertainties are reduced.
153 citations
Cites background from "Comparison of 14CO2, CO, and SF6 as..."
...…potential proxy for CO2ff (e.g. Rivier et al., 2006; Potosnak et al., 1999; Bakwin et al., 1998; Wofsy et al., 1994), atmospheric measurements suggest that the point source nature of SF6 results in a variable SF6:CO2ff emission ratio (RSF6/CO2ff), especially at small scales (Turnbull et al., 2006)....
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...We estimate this correction as −0.2 ± 0.1 ppm (the correction is subtracted, hence increasing CO2ff) for samples collected at this location and time of year (Turnbull et al., 2006, 2009)....
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...…the NEI inventories are a factor of two too high at several locations in the US (Graven et al., 2009; Hudman et al., 2008; Parrish et al., 2006; Turnbull et al., 2006; Warneke et al., 2006), and suggest that the CEPAM CO inventory is a substantial improvement over the older bottom-up CO…...
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References
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TL;DR: In this article, standards for reporting C-14 age determinations are discussed, and the statistical uncertainty (plus or minus one standard deviation) expresses counting errors, inaccuracies in voltage, pressure, temperature, dilution, and should include errors in C-13 ratios.
Abstract: Standards for reporting C-14 age determinations are discussed. All dates should be related either directly or indirectly to the NBS oxalic acid standard. Corrections for isotopic fractionation are also desirable. For some materials, particularly marine shell, corrections for reservoir effect are necessary, but these should always be reported separately from the conventional radiocarbon age. The statistical uncertainty (plus or minus one standard deviation) expresses counting errors, inaccuracies in voltage, pressure, temperature, dilution, and should include errors in C-13 ratios. Errors can be significant when isotope ratios are estimated rather than measured directly. The error in the conventional C-14 half life is not included. The article includes tables indicating what data should be reported.
5,579 citations
"Comparison of 14CO2, CO, and SF6 as..." refers methods in this paper
...[5] We use D14C to describe the 14C concentration [Stuiver and Polach, 1977]....
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University of New Hampshire1, Princeton University2, Centre national de la recherche scientifique3, Woods Hole Research Center4, United States Department of Agriculture5, United States Geological Survey6, Goethe University Frankfurt7, Max Planck Society8, Oregon State University9, Carnegie Institution for Science10
TL;DR: Land- and atmosphere-based estimates of the carbon sink in the coterminous United States for 1980–89 are consistent, within the large ranges of uncertainty for both methods, indicating a relatively stable U.S. sink throughout the period.
Abstract: For the period 1980-89, we estimate a carbon sink in the coterminous United States between 0.30 and 0.58 petagrams of carbon per year (petagrams of carbon = 10(15) grams of carbon). The net carbon flux from the atmosphere to the land was higher, 0.37 to 0.71 petagrams of carbon per year, because a net flux of 0.07 to 0.13 petagrams of carbon per year was exported by rivers and commerce and returned to the atmosphere elsewhere. These land-based estimates are larger than those from previous studies (0.08 to 0.35 petagrams of carbon per year) because of the inclusion of additional processes and revised estimates of some component fluxes. Although component estimates are uncertain, about one-half of the total is outside the forest sector. We also estimated the sink using atmospheric models and the atmospheric concentration of carbon dioxide (the tracer-transport inversion method). The range of results from the atmosphere-based inversions contains the land-based estimates. Atmosphere- and land-based estimates are thus consistent, within the large ranges of uncertainty for both methods. Atmosphere-based results for 1980-89 are similar to those for 1985-89 and 1990-94, indicating a relatively stable U.S. sink throughout the period.
804 citations
TL;DR: A comprehensive tropospheric (super 14) CO (sub 2) data set of quasi-continuous observations covering the time span from 1959 to 2003 is presented in this article, where samples were collected at 3 European mountain sites at height levels of 1205 m (Schauinsland), 1800 m (Vermunt), and 3450 m asl (Jungfraujoch).
Abstract: A comprehensive tropospheric (super 14) CO (sub 2) data set of quasi-continuous observations covering the time span from 1959 to 2003 is presented. Samples were collected at 3 European mountain sites at height levels of 1205 m (Schauinsland), 1800 m (Vermunt), and 3450 m asl (Jungfraujoch), and analyzed in the Heidelberg Radiocarbon Laboratory. The data set from Jungfraujoch (1986-2003) is considered to represent the free tropospheric background level at mid-latitudes of the Northern Hemisphere, as it compares well with recent (yet unpublished) measurements made at the marine baseline station Mace Head (west coast of Ireland). The Vermunt and Schauinsland records are significantly influenced by regional European fossil fuel CO (sub 2) emissions. The respective delta (super 14) CO (sub 2) depletions, on an annual mean basis, are, however, only 5 ppm less than at Jungfraujoch. Vermunt and Schauinsland both represent the mean continental European troposphere.
511 citations
Colorado State University1, Commonwealth Scientific and Industrial Research Organisation2, National Center for Atmospheric Research3, National Oceanic and Atmospheric Administration4, Massachusetts Institute of Technology5, Princeton University6, University of California, Berkeley7, Max Planck Society8, Environment Canada9, Japan Agency for Marine-Earth Science and Technology10, University of California, Irvine11, National Institute of Advanced Industrial Science and Technology12, Columbia University13
TL;DR: In this paper, the authors conducted a set of annual mean inversion experiments in which 17 different transport models or model variants were used to calculate regional carbon sources and sinks from the same data with a standardized method.
Abstract: Spatial and temporal variations of atmospheric CO2 concentrations contain information about surface sources and sinks, which can be quantitatively interpreted through tracer transport inversion. Previous CO2 inversion calculations obtained differing results due to different data, methods and transport models used. To isolate the sources of uncertainty, we have conducted a set of annual mean inversion experiments in which 17 different transport models or model variants were used to calculate regional carbon sources and sinks from the same data with a standardized method. Simulated transport is a significant source of uncertainty in these calculations, particularly in the response to prescribed “background” fluxes due to fossil fuel combustion, a balanced terrestrial biosphere, and air‐sea gas exchange. Individual model-estimated fluxes are often a direct reflection of their response to these background fluxes. Models that generate strong surface maxima near background exchange locations tend to require larger uptake near those locations. Models with weak surface maxima tend to have less uptake in those same regions but may infer small sources downwind. In some cases, individual model flux estimates cannot be analyzed through simple relationships to background flux responses but are
305 citations
TL;DR: In this paper, the Radon-Tracer-Method is applied to quantify fossil fuel derived CO2 concentrations at a regional polluted site, and at a continental mountain station in south-west Germany.
Abstract: Long-term atmospheric 14CO2 observations are deployed to quantify fossil fuel derived CO2 concentrations at a regional polluted site, and at a continental mountain station in south-west Germany. Fossil fuel CO2 emission rates for the relevant catchment areas are obtained by applying the Radon-Tracer-Method. They are shown to compare well with statistical emissions inventories but reveal a larger seasonality than assumed earlier, thus contributing significantly to the observed CO2 seasonal cycle over Europe. Based on the present approach, emissions reductions on the order of 5-10% are detectable for catchment areas of several hundred kilometres radius, as anticipated within a five-years commitment period of the Kyoto Protocol. Still no significant change of fossil fuel CO2 emissions is observed at the two sites over the last 16 years.
263 citations
"Comparison of 14CO2, CO, and SF6 as..." refers background in this paper
...[3] The fossil fuel contribution to the atmospheric CO2 signature can be constrained using economic emissions inventories [e.g., Gurney et al., 2003; Pacala et al., 2001] with an estimated annual global uncertainty of 10–15% [Marland et al., 2003]....
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...Globally, these contributions are estimated to be 1 to 2 GtC/yr [Gurney et al., 2003] and 6.6 GtC/yr (for 2002 [Marland et al., 2003]), respectively....
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