Reduction of atmospheric radiocarbon concentration by fossil fuel carbon dioxide and the mean life of carbon dioxide in the atmosphere

It is generally accepted that the combustion of fossil fuels over the period 1860 to 1954 has produced an amount of carbon dioxide, containing no radiocarbon, that is equal to approxi­mately 13% of the carbon dioxide in the atmosphere. The addition of this 4 'old' carbon dioxide to the atmosphere has observably disturbed the steady-state distribution of carbon-14 in nature. In the present paper measurements are described of the carbon-14 concentration in sets of wood samples from the northern and southern hemispheres, and these show that the carbon-14 specific activity of atmospheric carbon dioxide has decreased by 2.03 ± 0.15% over the period 1860 to 1954, and that the present-day difference between the decrease in the northern and southern hemispheres is less than 0.50%. The response of various mathematical models of the carbon cycle in nature to the addition of ‘old’ carbon dioxide at an exponential rate has been considered. Using the above data in conjunction with these models it is deduced that: (1) The mean life of a carbon dioxide molecule in the atmosphere before it is absorbed into other reservoirs of carbon must be less than 7 yr, and is probably of the order of 2 yr. (2) The exchange time for mixing of the atmospheres of the two hemispheres (i. e. the mean life of a carbon dioxide molecule in the atmosphere of one hemisphere before trans-ferrence to the other hemisphere) is less than 2 yr.

From a theoretical study of the production and distribution of fossil-fuel carbon dioxide released since the beginning of the Industrial Revolution calculations have been made of the resultant decreases in atmospheric carbon-14 specific activities (Suess effect). The calculations are based on recent advances in the assessment of parameters which control carbon circulation and a re-evaluation of the combustion rates of fossil fuels. Results show that the reduction in carbon-14 specific activities amounted to -0.5, -3.2 and -5.9 % in A. D. 1890, 1950 and 1969 respectively. Analyses of biospheric materials of known age show good agreement between the predicted and observed atmospheric carbon -14 concentrations although the possibility exists of a perturbation of natural origin. The incorporation of significant amounts of fossil fuel carbon into 1890 wood indicates the possibility of error in radiocarbon analyses based on the conventional modern reference material. The study also enables corrections to be made for the Suess effect to observations of carbon -14 activities of samples grown during the past century. Predictions of future consumption of fossil fuels have permitted evaluation of the approximate magnitude of the future Suess effect. The results imply that the effect will be of increasing importance, reaching about -23% by 2000 and -50 % by 2025. The Suess effect, which is in competition with the nuclear bomb effect, may therefore reduce atmospheric carbon -14 concentration to the natural level again by 1990. Future increase in atmospheric carbon dioxide levels could have significant climatological consequences, but the magnitude of these changes remains speculative.


2001 ◽  
Vol 77 (2) ◽  
pp. 259-264 ◽  
Author(s):  
Gerald A. Tuskan ◽  
Marie E. Walsh

Atmospheric concentrations of carbon dioxide (CO2) are increasing along with global use of fossil fuels and worldwide rates of deforestation. These trends have led international panels and organizations to devise carbon management strategies in an effort to curb increases in CO2. The goal of this paper is to explore the potential role of short-rotation woody crops (SRWC) in the U.S. as one option in a carbon-managed future economy. On a scale of 40 × 106 ha, and at an average productivity rate of 21 Mg oven-dry biomass ha−1 yr−1, SRWC systems could account for an average of 0.30 Pg of C yr−1 when prorated over the 50-year deployment life of a typical SRWC system. Most of the accounted carbon (76%) would come from fossil fuel displacement as opposed to direct carbon sequestration. The proportion of accounted carbon associated with fossil fuel displacement increases with longer time frames due to the relatively rapid saturation of the carbon sequestration pool. Key words: Populus, biomass, carbon sequestration, carbon displacement, Kyoto Protocol, CO2


2012 ◽  
Vol 9 (9) ◽  
pp. 12259-12308 ◽  
Author(s):  
V. Haverd ◽  
M. R. Raupach ◽  
P. R. Briggs ◽  
J. G. Canadell ◽  
S. J. Davis ◽  
...  

Abstract. This paper reports a study of the full carbon (C-CO2) budget of the Australian continent, focussing on 1990–2011 in the context of estimates over two centuries. The work is a contribution to the RECCAP (REgional Carbon Cycle Assessment and Processes) project, as one of numerous regional studies being synthesised in RECCAP. In constructing the budget, we estimate the following component carbon fluxes: Net Primary Production (NPP); Net Ecosystem Production (NEP); fire; Land Use Change (LUC); riverine export; dust export; harvest (wood, crop and livestock) and fossil fuel emissions (both territorial and non-territorial). The mean NEP reveals that climate variability and rising CO2 contributed 12 ± 29 (1σ error on mean) and 68 ± 35 Tg C yr−1 respectively. However these gains were partially offset by fire and LUC (along with other minor fluxes), which caused net losses of 31 ± 5 Tg C yr−1 and 18 ± 7 Tg C yr−1 respectively. The resultant Net Biome Production (NBP) of 31 ± 35 Tg C yr−1 offset fossil fuel emissions (95 ± 6 Tg C yr−1) by 32 ± 36%. The interannual variability (IAV) in the Australian carbon budget exceeds Australia's total carbon emissions by fossil fuel combustion and is dominated by IAV in NEP. Territorial fossil fuel emissions are significantly smaller than the rapidly growing fossil fuel exports: in 2009–2010, Australia exported 2.5 times more carbon in fossil fuels than it emitted by burning fossil fuels.


2021 ◽  
Author(s):  
Emily Dowd ◽  
Christopher Wilson ◽  
Martyn Chipperfield ◽  
Manuel Gloor

<p>Methane (CH<sub>4</sub>) is the second most important atmospheric greenhouse gas after carbon dioxide. Global concentrations of CH<sub>4</sub> have been rising in the last decade and our understanding of what is driving the increase remains incomplete. Natural sources, such as wetlands, contribute to the uncertainty of the methane budget. However, anthropogenic sources, such as fossil fuels, present an opportunity to mitigate the human contribution to climate change on a relatively short timescale, since CH<sub>4</sub> has a much shorter lifetime than carbon dioxide. Therefore, it is important to know the relative contributions of these sources in different regions.</p><p>We have investigated the inter-annual variation (IAV) and rising trend of CH<sub>4</sub> concentrations using a global 3-D chemical transport model, TOMCAT. We independently tagged several regional natural and anthropogenic CH<sub>4</sub> tracers in TOMCAT to identify their contribution to the atmospheric CH<sub>4</sub> concentrations over the period 2009 – 2018. The tagged regions were selected based on the land surface types and the predominant flux sector within each region and include subcontinental regions, such as tropical South America, boreal regions and anthropogenic regions such as Europe. We used surface CH<sub>4</sub> fluxes derived from a previous TOMCAT-based atmospheric inversion study (Wilson et al., 2020). These atmospheric inversions were constrained by satellite and surface flask observations of CH<sub>4</sub>, giving optimised monthly estimates for fossil fuel and non-fossil fuel emissions on a 5.6° horizontal grid. During the study period, the total optimised CH<sub>4</sub> flux grew from 552 Tg/yr to 593 Tg/yr. This increase in emissions, particularly in the tropics, contributed to the increase in atmospheric CH<sub>4 </sub>concentrations and added to the imbalance in the CH<sub>4</sub> budget. We will use the results of the regional tagged tracers to quantify the contribution of regional methane emissions at surface observation sites, and to quantify the contributions of the natural and anthropogenic emissions from the tagged regions to the IAV and the rising methane concentrations.</p><p>Wilson, C., Chipperfield, M. P., Gloor, M., Parker, R. J., Boesch, H., McNorton, J., Gatti, L. V., Miller, J. B., Basso, L. S., and Monks, S. A.: Large and increasing methane emissions from Eastern Amazonia derived from satellite data, 2010–2018, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2020-1136, in review, 2020.</p>


1963 ◽  
Vol 41 (1) ◽  
pp. 1-7 ◽  
Author(s):  
H. Reisener ◽  
A. J. Finlayson ◽  
W. B. McConnell

When uredospores of Puccinia graminis var. tritici race 15B were shaken in a medium containing M/30 phosphate buffer, pH 6.2, and valerate-2-C14, about 88% of the radioactivity was removed from the buffer solution in a period of 3 hours. About 40% of the carbon-14 taken from the buffer was found in a water-soluble extract of the spores and about 15% was respired as carbon dioxide. The result is compared with an earlier report that carbon 1 of valerate is more extensively released as carbon dioxide and less extensively incorporated into spore components. Glutamic acid, glutamine, γ-aminobutyric acid, and alanine of high specific activity were isolated. It was estimated from partial degradation that more than one-half of the carbon-14 of glutamic acid occurred in position 4 and that carbon 5 was very weakly labelled. Citric acid was also of high specific activity and was labelled predominantly in the internal carbons.It is concluded that respiring rust spores utilize externally supplied valerate by β-oxidation, which releases carbons 1 and 2 in a form which is metabolized as acetate by the tricarboxylic acid cycle.


1981 ◽  
Vol 8 (4) ◽  
pp. 285-297 ◽  
Author(s):  
Charles C. Coutant

Freshwater environments are expected to be particularly responsive to temperature rises and changed precipitation régimes that are anticipated to result from progressive increases in atmospheric carbon dioxide from fossil-fuel combustion. Recognition of potential impacts on aquatic systems should strengthen research and management planning for the future, and provide more confident estimates of the risks from CO2 elevation than those at present available. This report briefly evaluates those aquatic impacts that are believed to be important and worthy of investigation and quantitative forecasting.Priorities for additional research have been suggested for the issues discussed herein. These priorities vary according to the use of pertinent data, the credibility of presumed risk (which may change as, for example, climatic models are better refined), the timing in relation to prerequisite information, current efforts already under way, and the feasibility of obtaining the desired data. The ranking remains subjective, however, and debatable.


2007 ◽  
Vol 4 (1) ◽  
pp. 1-11 ◽  
Author(s):  
J. Henderiks ◽  
R. E. M. Rickaby

Abstract. An urgent question for future climate, in light of increased burning of fossil fuels, is the temperature sensitivity of the climate system to atmospheric carbon dioxide (pCO2). To date, no direct proxy for past levels of pCO2 exists beyond the reach of the polar ice core records. We propose a new methodology for placing an upper constraint on pCO2 over the Cenozoic based on the living geological record. Specifically, our premise is that the contrasting calcification tolerance of various extant species of coccolithophore to raised pCO2 reflects an "evolutionary memory" of past atmospheric composition. The different times of first emergence of each morphospecies allows an upper constraint of past pCO2 to be placed on Cenozoic timeslices. Further, our hypothesis has implications for the response of marine calcifiers to ocean acidification. Geologically "ancient" species, which have survived large changes in ocean chemistry, are likely more resilient to predicted acidification.


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