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Simulation proves that the anthropogenic CO2 portion in the atmosphere is 7.7 % - not 28 % as argued

Introduction: The common estimate of the increased amount of the atmospheric CO2 since 1750 is based on the CO2 concentration increase from 280 ppm to 396.5 ppm in 2013 totaling 234 GtC (= Gigatons of carbon). According to IPCC all of this increase has an anthropogenic origin corresponding to 28 % share of the total CO2 amount. It is not commonly known that this figure is false, because the direct CO2 isotope measurements show that the actual anthropogenic CO2 portion is only 7.7 %. This presentation is based on the peer-reviewed paper “Anthropogenic Carbon Dioxide (CO2) Amounts and Fluxes between the Atmosphere, the Ocean, and the Biosphere”. The paper presents reasons and a model explaining why the anthropogenic concentration in the atmosphere is surprisingly low and why IPCC wants to use much higher figure.

The majority of climate researchers and IPCC approves the fact that nearly 50 % of the carbon dioxide (CO2) produced by the mankind stays in the atmosphere and the other half is absorbed by the oceans. This situation is illustrated in Fig. 1.

Fig. 1 Yearly CO2 increase in the atmosphere and the temperature variations of the southern ocean i.e. the average of the sea temperatures of oceans 20N-20S and 30S-60S.

These figures are difficult to deny, as they are based on the direct measurements. There is one feature related to the CO2 concentration, which is not well-known even among the climate researchers being the portion of anthropogenic CO2 (caused by the actions of the mankind). The total CO2 concentration has been measured systematically and accurately since 1958 and the present level is about 400 ppm.

Firstly it is useful to describe in which way the anthropogenic CO2 concentration in the atmosphere or in the oceans can be measured, and then to differentiate it from the natural CO2. The measurement is based on the fact, that there are two isotopes of carbon in nature. The isotope with the atomic weight of 12 is more common, and it is marked by 12C. The portion of heavier isotope 13C is only about 1 %. The isotope measurements are extremely accurate and therefore even small differences can be measured.

For some reason the concentration of the isotope 13C is not indicated by the percentage numbers but, rather a special measurement unit is in use. It has many names: per mil, per mill, permil, permill, permille or ‰. This measurement unit is marked usually by as δ13C. In this description the ‰ – marking is used. The natural level of δ13C without the impact of the mankind, i.e. before the year 1750, has been -6.5 … -7.0 ‰ but is no longer so.

The anthropogenic portion of CO2 can be measured based on the fact that the plants prefer in some extent the isotope 12C. The direct δ13C measurements show that the present levels are: the atmosphere -8.2…-8.4 ‰, the oceans -9.0…-10.0 ‰, the biosphere (plants) -26.0 ‰, and the fossil fuels -28.0 ‰. Because the fossil fuels originate from the plants, they have almost the same δ13C level as the plants. The measurement unit values are all negative. Therefore it is useful to notice that the δ13C levels of the atmosphere and the oceans are greater than that of the biosphere but smaller than they used to be in the year 1750. The Austrian born American scientist Hans Suess noticed firstly that the anthropogenic CO2 dilutes the radioactive 14C concentration of the atmosphere. This dilution phenomenon has been enlarged also to 13C concentrations in the climate change science, and as such this phenomenon is called the Suess effect.

Permille values emphasize strongly the δ13C concentration differences. In reality δ13C value of -7.0 ‰ means 1.11585 % portion and δ13C of -26.0 ‰ means 1.10945 % portion. The δ13C value of the present atmosphere can be calculated according to the following formula

δ13C = (100 - PCTant)/100 * (-7.0) + (PCTant/100) * (-28),

in which PCTant is the percentage value of the anthropogenic CO2 in the atmosphere and the -28 is the δ13C of fossil fuels. If the percentage share of 28 % argued by IPCC were true, then according this formula δ13C would be -12.9 ‰. It is far away from the measured values of -8.2…-8.4 ‰. The percentage value 28 is based on the assumption that the increase of CO2 of 234 GtC would totally originate from the actions of the mankind, i.e. the increase from 616 GtC (year 1750) to 850 GtC (year 2013) = 100 * (850-616)/850 = 28 %.

Before the year 1750, which is used as the starting point of burning the coal, the CO2 concentration was 280 ppm. A straightforward conclusion could be in the same way as argued by IPCC, that because the total increase of the atmospheric CO2 is caused by burning coal, oil and the natural gas, then also the whole increase has an anthropogenic origin. There is the evidence by the direct δ13C measurements that this is not true. IPCC does not approve this measurement result. A good question is, why IPCC denies the direct measurement result, because the warming capabilities of CO2 do not depend on the origin or the isotope relationship 13C/12C. I decided to find out the real mechanism of anthropogenic CO2 increase in the atmosphere. In this study I also learned in the end, what is likely the actual reason of IPCC in denying this fact and it is revealed in the end of this analysis.

As a first step to understand the atmospheric CO2 concentration dependencies, a flow chart is depicted in Fig. 2 revealing the qualitative explanations.

Fig. 2. A simple carbon cycle presentation. The reservoirs are in Giga tons of carbon (GtC=PgC) and fluxes in GtC/y.

As one can see in Fig. 2, the atmospheric CO2 amount is in an efficient recycling process. Yearly about 25 % of the atmospheric CO2 is recycled between the oceans and the biosphere. The oceans do not choose between the different CO2 isotopes but they absorb carbon dioxide isotopes in direct proportion as these molecules are in the atmosphere. The biosphere prefers 12C isotopes slightly but it has no practical meaning. I composed a four box model commonly used in describing this recycling process, Fig. 3.

Fig. 3. Four-box model applied for the atmosphere-ocean carbon cycle in development of 1DAOBM.

I named this model as 1DAOBM (One dimensional atmosphere-ocean-biosphere model) and it is based on the following selections and facts: 1) the anthropogenic and the natural CO2 are totally mixed in the atmosphere, 2) the oceans absorb and absolve carbon dioxide keeping the prevailing relationship 12C/13C of the atmosphere, 3) the biosphere recycles carbon dioxide keeping δ13C concentration in the value of -26 ‰, 4) the surface ocean (75 m deep) is fully mixed and absorbs and absolves CO2 according to Henry’s law, 5) the biosphere is described by four parallel tube reactors having four different residence times (0, 1, 8 and 50 years), 6) the CO2 amount moving into the intermediate and deep ocean is based on the encompassing empirical measurement results that by the year 1994, the oceans have absorbed 118 GtC of the anthropogenic CO2.

Because the absorption according to Henry’s law is strongly dependent on the atmospheric CO2 concentration and the ocean temperature, it explains, why the yearly amount of CO2 absorbed by the oceans varies as one can see in Fig 1. CO2 moves down into the intermediate and deep ocean by diffusion process and finally it precipitates on the ocean bed as calcium carbonate (CaCO3). The relationship between carbon in the atmosphere and in the oceans following Henry’s law, has been 1:63 before the year 1750 and at present it is about 1:45. In the long run the oceans are capable of almost recovering the original relationship. The diffusion step in the movement of the CO2 into the deep ocean controls this process.

The results of the simulations by 1DAOBM are depicted in Fig. 4. The calculations start from the year 1750 but Fig. 4 starts from the year 1850. The anthropogenic portion of CO2 in the atmosphere according to this study is 7.7 % in 2013. The simulation is based on the time period of 263 years, the information of the data banks, Henry’s law and one empirical formula. The starting value of δ13C in year 1750 has been assumed to be – 6.75 ‰ (the average value of different studies ranging from -6 to -7.0 ‰) and the δ13C value in the year 2013 is -8.4‰. It is exactly the measured δ13C value in the atmosphere.

Fig. 4. The calculated anthropogenic CO2 fluxes and amounts according to 1DAOBM.

This situation can be further illustrated by Fig. 5.

Fig. 5. The illustration of the carbon cycle effects in diluting and removing the anthropogenic CO2 from the atmosphere. The numerical values correspond to the cumulative values of anthropogenic fluxes integrated from 1750 to 2013 and the reservoirs in 2013 (black font). The exception is the value 183 (blue font in brackets) corresponding to the natural CO2 flux from the ocean into the atmosphere. One dot represents 1 GtC of CO2. The black dots inside the arrows represent yearly anthropogenic flux rates in 2013. The blue dots represent the natural yearly CO2 flux rate in 2013 recycling back from the ocean into the atmosphere and replacing anthropogenic CO2.

As one can see in Fig. 5, the carbon pump removes 26.6 % of the anthropogenic CO2 in the year 2013 from the total anthropogenic CO2 amount of 65 GtC. As a result totally 17.2 GtC anthropogenic carbon is recycled into the oceans (7.9 GtC) and into the biosphere (9.3 GtC). This amount is greater than the annual fossil emission amount 9.9 GtC. Because at the same time totally 9.1 GtC anthropogenic carbon recycles back from the oceans and the biosphere, the net increase of the anthropogenic carbon in the atmosphere is only 9.9+9.1-17.2 = 1.8 GtC. Natural carbon dioxide moves from the oceans replacing the departing anthropogenic carbon from the atmosphere. This amount varies strongly at the yearly level according to the temperature variations of the oceans. This situation is illustrated in Fig. 6. The 1DAOBM also explains fairly well these yearly variations, as one can see in comparing the black and red graphs (r2=0.75). This result is better than the results achieved by complicated models and there is not a so called “missing CO2 problem”. According to more complicated models the oceans absorb about 1 GtC less carbon dioxide and therefore the carbon balance is not actually in balance.

Fig. 6. The measured and calculated CO2 fluxes into the atmosphere.

The 1DAOBN can easily be used to also simulate future projections assuming a yearly emission rate development. I selected one of the IPCC’s future projections by name RCP4.5, which means that in 2100 the climate forcing would have stabilized to the value of 4.5 Wm-2. In this projection the fossil fuel emissions increase from the present level 10 GtC/y to the value of 11.5 GtC/y up to 2040, decrease to the value of 4.1 GtC/y up to 2080, and thereafter they stay at this level. This simulation is depicted in Fig. 7.

Fig. 7. The simulation results of the fossil fuel emissions close to projection RCP4.5

In this figure one can see a distinct difference in comparison to the results of the IPCC’s projection. Even though the fossil fuel emissions decrease strongly after 2040, the atmospheric CO2 concentration according to IPCC does not start to decrease, rather it even increases slightly. The reason is the insight of IPCC about the behavior of the anthropogenic CO2 that “about a third to half of an initial pulse of anthropogenic CO2 goes into the land and ocean” but later on this “going” is reduced essentially because of the buffer capacity decrease of the oceans.

At this phase IPCC starts to imply its own long residence time of CO2 in the atmosphere, which is more than 100 years. In a survey study of 34 individual studies the residence time of CO2 varied in the range from 2 to 15 years and the average value was 7.5 years. My own simulation study gives the residence time of 15 years. Based on its own residence time more than 100 years, IPCC argues that the anthropogenic portion of CO2 in the atmosphere is already today 28 %. The measurements show that the real value is 7.7 % equaling δ13C value of -8.4 ‰. It looks like the effects of the carbon pump are not taken into account in the calculations of IPCC. The presentation way of IPCC is that the projection illustrations do not include the fossil fuel emission graphs. Because of this omission, a reader cannot question, why the CO2 concentration graph stays essentially constant, even though the emissions decrease strongly. The final motive behind these tricks is that IPCC wants to produce scary projections for the future. These projections are based on the very long residence times of CO2, which leads the phenomenon that CO2 seems to stay in the atmosphere “forever” even though the emissions decrease strongly. Finally, the warming is ensured by the high warming capacity of CO2, which is also an incorrect image produced by IPCC.

The original paper:

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