The error in Friedlingstein et al (2021) is much larger than expected. Friedlingstein et al Page 4: “total anthropogenic CO2 emission of 10.2 ± 0.8 GtC yr-1 (37.4 ± 2.9 GtCO2).”
The amounts above are their calculation, not mine.
Friedlingstein et al reported their estimate for 1 year’s (2020) increase for human fossil fuel emissions, land use and cement = 37.4 +- 2.9 Gt CO2. This is their estimate of emissions not net emissions. Net CO2 absorption has not been subtracted.
Follow this simple arithmetic:
• Using NOAA Mauna Loa data only (no estimates, no theories, no models, no assumptions.) Reported in micromoles/mole = ppm.
• MLO did not report CO2 flask measurements on Jan 1, 2020
• 2 Jan 2020, MLO reported 4 CO2 flask measurements for Jan 2, 2020. Average 412.9875 ppm
• 31 Dec 2020, MLO reported 4 CO2 flask measurement for Dec 31, 2020. Average 415.5225 ppm
• CO2 increase due to all sources human and natural combined for year 2020 is 2.535 ppm, (i.e., 415.5 minus 412.9875)
• 2.535 ppm CO2 per year times 7.76 Gt CO2 per ppm of CO2 = 19.679 Gt CO2 added to the atmosphere in 2020 from all sources human and natural.
• Thus, net CO2 added by humans cannot exceed 19.679 Gt CO2 in 2020, because this amount includes net CO2 additions by all sources.
• Net global average CO2 concentration reported by Mauna Loa on 31 December 2020, the average of 4 measurements that day was 415.5225 ppm. Multiply by 7.76 Gt per ppm = 3224.455 Gt CO2 total CO2 in atmosphere.
• Then, 19.679 / 3224.455 = 0.006103. Multiply by 100 = 0.610%.
• Net Human CO2 added to air in 2020 cannot exceed 0.610% of total CO2 for 2020. This 0.61% includes net CO2 emissions and net CO2 absorptions from humans including cement, net CO2 from ocean, net CO2 from land, rivers, lakes, CO2 from rotting and decay, net CO2 from biosphere, etc.
37.4 Gt CO2 is the Friedlingstein et al estimate of human emissions only for 2020. It is an excessively complicated estimate. If you read the Friedlingstein et al paper you will see the complications, uncertainties, and assumptions. But that amount is human emissions only and only emissions, that is CO2 absorptions have not been subtracted from their estimated human CO2 emissions.
Net total CO2 added in 2020 was measured 19.679 Gt CO2. 37.4/19.7 = 52.7%, but this is an apples and oranges comparison. 19.7 is total emissions minus total absorption. 37.4 is human only and emissions only. Friedlingstein et al has a major problem. We do not know how much of that 37.4 Gt CO2 human emission was absorbed during 2020. But we do know that net human emissions cannot exceed 19.679 Gt CO2.
It is easily proven and observed that ocean is both a CO2 sink and a CO2 source. CO2 flux is non-stop in both directions, into and out of Earth’s surface. Earth’s surface is over 70% ocean. CO2 gas molecules continuously collide with ocean surface, day and night, regardless of season, temperature, or location; some of that CO2 is emitted back into air, and some is retained in the surface. The partition ratio of CO2 between gas in the surface versus gas above the surface is the Henry’s Law coefficient. The coefficient is a simple ratio of CO2 moles or mass; it varies with the local surface temperature. The resulting ratio is a dimensionless, intensive property of matter. Adding more CO2 to the air or to the ocean surface does not change the CO2 ratio. Diffusivity of a gas in a liquid is a function of the mass of the gas, specifically the inverse of the square root of the molecular weight of the gas. Humans, volcanoes, biosphere, etc., adding CO2 to the atmosphere does not change the Henry’s ratio or diffusivity of the CO2 gas into the ocean surface. The concentration of CO2 gas in the ocean surface and in the air at a given local surface temperature is given by the Henry’s Law coefficient plus or minus temporary perturbations due to alkalinity, surface or air disturbances due to winds, currents, and salinity at that location. The net amount of biosphere CO2 flux, another perturbation, is also non-stop in both directions when CO2 emissions due to decay are included. These perturbations adjust by CO2 emission or CO2 absorption and rapidly return to the Henry’s Law CO2 partition ratio.
Friedlingstein et al say on Page 9: “Global emissions and their partitioning among the atmosphere, ocean and land are in reality in balance.”
Friedlingstein et al calculate on page 32, section 3.4.2, “The observed stability of the airborne fraction over the 1960-2020 period indicates that the ocean and land CO2 sinks have been removing on average about 55% of the anthropogenic emissions (see sections 3.5 and 3.6).”
Apparently, Friedlingstein et al believe nature is in balance, except for humans. Apparently, they believe that nature, which balances 3224.455 Gt CO2 total CO2 in atmosphere by continuous emissions and absorptions, is unable to balance an additional estimated 37.4 Gt CO2 from humans. Nature is already balancing over 86 times more CO2 than their estimation of human emissions, (i.e., 3224.5/37.4) but for some unexplained reason they believe nature is unable to balance the relatively tiny human CO2 perturbation, a human amount which is much less than 0.61% of the total, (i.e., 19.7/3224.5) because that 0.61% includes net CO2 emissions from all sources and sinks, human and natural.
Even the above example understates the size of their error. Since net human emissions would be a cumulative net of two fluxes, if there were a method to measure it, and since net global average CO2 concentration (i.e., NOAA Mauna Loa) is the net of two giant CO2 fluxes in opposite vector directions, then we should compare these data as integral areas. (That is still an apples and oranges comparison because we only have the estimate of human emissions, not net human emissions. But at least the comparison would be in the right order of magnitude.)
Follow this simple arithmetic:
- Friedlingstein et al estimate 37.4 Gt human CO2 emissions for 2020. For avoidance of doubt, this is not emission minus absorption.)
- 1 ppm CO2 equals 7.76 Gt CO2
- 37.4 Gt divided by 7.76 = 4.8195 ppm human CO2 emissions for 2020, call it 4.8 ppm
Then the comparison between total CO2 versus Friedlingstein et al estimated human CO2 emission would look something like the following graphic. We compare the entire area of the orange quadrangle to the area of the thin blue quadrangle. Absorptions of human CO2 emissions have not been subtracted. Nevertheless, it should be obvious that B is not causing A, and the orange area is enormously larger than the blue area.
Human emissions cannot be driving the growth rate (slope) observed in net global average CO2 concentration.
Net global average CO2 concentration in air today is the same as it would be if humans never existed.

References
- Friedlingstein et al. (2021) https://essd.copernicus.org/preprints/essd-2021-386/essd-2021-386.pdf
- K.W. Thoning, A.M. Crotwell, and J.W. Mund (2022), Atmospheric Carbon Dioxide Dry Air Mole Fractions from continuous measurements at Mauna Loa, Hawaii, Barrow, Alaska, American Samoa and South Pole. 1973-2021, Version 2022-05 National Oceanic and Atmospheric Administration (NOAA), Global Monitoring Laboratory (GML), Boulder, Colorado, USA. https://doi.org/10.15138/yaf1-bk21
- Dlugokencky, E.J., J.W. Mund, A.M. Crotwell, M.J. Crotwell, and K.W. Thoning (2021), Atmospheric Carbon Dioxide Dry Air Mole Fractions from the NOAA GML Carbon Cycle Cooperative Global Air Sampling Network, 1968-2020, Version: 2021-07-30, https://doi.org/10.15138/wkgj-f215 download file here: https://budbromley.blog/wp-content/uploads/2022/11/raw-unparsed-daily-esrl-mlo-1973-to-2020-2.xlsx
- Bromley, B., & Tamarkin, T. (2022). Correcting misinformation on atmospheric carbon dioxide. https://budbromley.blog/2022/05/20/correcting-misinformation-on-atmospheric-carbon-dioxide/
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