"One of the key arguments wielded by the alarmists is that the bulk of CO2 emitted by fossil fuel usage has remained in the atmosphere, will keep doing so for more than a century and that its ominous effect will be deferred and felt by the future generations,
... therefore trying to put the blame on us right now so that immediate action be taken in order to curb emissions ASAP, whatever the dire economic consequences might be.
This does not resist even a quick fact checking.
In fact, the flux out-gassed by warm oceans between the tropics and by the soils where organic matter decomposes is of the same order of magnitude as the flux absorbed by cold oceans at high latitudes and by vegetation,
... but never quite equal because these absorbed and degassed fluxes depend on temperatures, precipitation and winds in the corresponding zones, and on the volume of vegetation which increases as per the carbon dioxide content of the air.
The ratio (annual stock / flux) of the atmospheric carbon stock (in the CO2 of the air) to the flux absorbed each year by the vegetation and by the oceans at high latitudes is in the range of four to five, hence an average lifespan of a molecule of CO2 in the air from 4 to 5 years.
One fifth of the CO2 in the air is absorbed every year, roughly half by vegetation and the other half by cold oceans at high latitudes on their surface; almost as much is degassed by the soils where the vegetation decomposes and by the warm oceans on their surface.
It appears that fossil fuels make up only 6% of the CO2 in the air (compared to 2% in 1958), the other 94% come from natural out-gassing of the oceans and soil, in billions of tonnes of carbon, Gt-C or gigatons of carbon: 10 Gt-C / year "fossils" against some 170 Gt-C / year "natural degassing" (Moranne, 2000)."
Here he does an interesting calculation that shows that only 6% of the CO2 entering the atmosphere is from fossil fuels.
The additional CO2 from both nature and fossil fuels has encouraged more plant growth. Net primary productivity of plants has increased 33% since 1900 and continues to increase with additional CO2. We put about 5 ppm/year (molecules per million) into the atmosphere using fossil fuels. Recent warming has increased out-gassing of CO2 from nature to about 80 ppm/year, for a total add of 85 ppm per year.
The net increase in the Mauna Loa records each year is less than 2 ppm.
We cannot tell which CO2 molecules are taken up by plants and which are not, but plants prefer the carbon isotope 12C over 13C and fossil fuels have more 12C per unit volume than the atmosphere, so fossil fuel CO2 is preferred by plants.
The 13C to 12C average ratio in coal, oil, and natural gas relative to the atmosphere is about -29 ‰ (parts per thousand).
Monitoring the change in the isotopes in the atmosphere through time allows us to show that the average residence time of a CO2 molecule in the atmosphere is four to five years.
This is dramatically different than what the IPCC reports in AR5, where they say:
“About half of the [fossil fuel] emissions remained in the atmosphere (240 ± 10 PgC) since 1750.” (IPCC, 2013, p. 467).
They also say:
The removal of human-emitted CO2 from the atmosphere by natural processes will take a few hundred thousand years (high confidence). (IPCC, 2013, p. 469).
Neither of these statements fit the Mauna Loa CO2 observations.
Using Poyet’s calculations, the ratio of 13C to 12C has declined by 7 ‰. The above statements would require a drop of 13 ‰ or more.
Hermann Harde came to the same conclusion in 2019 (Harde, 2019). He examined the components of the IPCC calculations and concluded that humans are not the primary cause of the recent increase in CO2, the dominant cause is recent warming.
Harde shows that human fossil fuel emissions contributed no more than 17 ppm (15%) of the estimated CO2 increase of 113 ppm since 1750.
As Poyet says, the IPCC calculation is both inaccurate and deceptive.
The IPCC focusses on the amount of CO2 that is stored in rocks, especially carbonates, over geological time and ignores intermediate storage.
The atmosphere only contains about 2% of the total surface CO2.
We define surface as from the ocean floor to the top of the atmosphere.
Most of the rest is in the oceans and in the muddy sediments below the ocean water, which we include in the surface if the mud is in full communication with the ocean water above it.
Poyet shows that his calculation of a 5-year CO2
atmospheric residence time can be integrated easily to show that, over
the period from 1959 to 2018, where we have good data, only 52 Gt-C
(gigatons of carbon) or 6% of total atmospheric CO2 and 14% of the CO2 emissions are left at the end of 2018, using emissions according to OurWorldinData.org."