What Fraction of Atmospheric CO₂ Is Anthropogenic?

johnwalker · 31 May 2023 14:53

A paper published in the February 2022 issue of Health Physics, “World Atmospheric CO₂, Its ¹⁴C Specific Activity, Non-fossil Component, Anthropogenic Fossil Component, and Emissions (1750–2018)” (full text at the link), uses the fraction of carbon dioxide in the Earth’s atmosphere containing the carbon-14 (C-14) isotope to disentangle the contribution of human (anthropogenic) activity from other sources of atmospheric CO₂ over the period in which fossil fuel burning has been a major contributor to human energy sources. Here is the abstract:

After 1750 and the onset of the industrial revolution, the anthropogenic fossil component and the non-fossil component in the total atmospheric CO2 concentration, C(t), began to increase. Despite the lack of knowledge of these two components, claims that all or most of the increase in C(t) since 1800 has been due to the anthropogenic fossil component have continued since they began in 1960 with “Keeling Curve: Increase in CO₂ from burning fossil fuel.” Data and plots of annual anthropogenic fossil CO₂ emissions and concentrations, C(t), published by the Energy Information Administration, are expanded in this paper. Additions include annual mean values in 1750 through 2018 of the ¹⁴C specific activity, concentrations of the two components, and their changes from values in 1750. The specific activity of ¹⁴C in the atmosphere gets reduced by a dilution effect when fossil CO₂, which is devoid of ¹⁴C, enters the atmosphere. We have used the results of this effect to quantify the two components. All results covering the period from 1750 through 2018 are listed in a table and plotted in figures. These results negate claims that the increase in C(t) since 1800 has been dominated by the increase of the anthropogenic fossil component. We determined that in 2018, atmospheric anthropogenic fossil CO₂ represented 23% of the total emissions since 1750 with the remaining 77% in the exchange reservoirs. Our results show that the percentage of the total CO₂ due to the use of fossil fuels from 1750 to 2018 increased from 0% in 1750 to 12% in 2018, much too low to be the cause of global warming.

The key observation underlying this research is that while the carbon in atmospheric carbon dioxide has a component of around one part per trillion of the carbon-14 isotope, mostly formed by cosmic ray interactions with atmospheric nitrogen through the process:

^{14}_{~~7}{\rm N} + {\rm n} \rightarrow ^{14}_{~~6}{\rm C} + {\rm p}

since carbon-14 beta decays back to nitrogen:

^{14}_{~~6}{\rm C} \rightarrow ^{14}_{~~7}{\rm N} + {\rm e}^{-} + \bar{\nu}_{\rm e}+156.6\ {\rm keV}

with a half-life of 5730 years, essentially all of the carbon-14 present in fossil fuels when they were formed has decayed, so when they are burned and the resulting CO₂ released into the atmosphere, their contribution to atmospheric carbon-14 is zero, and consequently dilutes the natural C-14 fraction. This can be used as a marker for the fraction of atmospheric CO₂ due to human use of fossil fuels.

This analysis is complicated by an increase in atmospheric C-14 due to atmospheric nuclear weapons tests, mostly between 1955 and 1963. Nuclear weapon detonations emit prodigious quantities of neutrons which interact with atmospheric nitrogen through the same process as cosmic rays, producing C-14. This caused a spike in atmospheric C-14 which is observed in the data, but by the 1980s most of the C-14 from nuclear testing had been absorbed in the oceans and land biosphere, leaving only a small residual increase in the atmosphere.

After controlling for these and other factors, the authors find that as of 2018, CO₂ added to the atmosphere by human activity accounted for only 23% of CO₂ since 1750, and that the fraction of anthropogenic CO₂ in the atmosphere had risen from 0% in 1750 to 12% in 2018. Where did the rest of the CO₂ come from, then, and what is the cause of global warming (if such exists)? The authors conclude:

An article on Glacial-Interglacial Cycles (NOAA) suggests that recent increases in CO₂ and temperatures are due primarily to cyclic changes of solar radiation associated with Earth’s orbit about the sun. The annual change, DC_NF(t), in the non-fossil component has positive increasing values in Table 2 (https://links.lww.com/HP/A210) after 1764. It will eventually become negative in the next glacial period when average temperatures decrease again as they have done over all of the previous glacial-interglacial cycles.

Fig. 1

Glacial-interglacial cycles. Solar radiation varies smoothly through time (top, orange line) with a strong cyclicity of ~23,000 years, as seen in this time series of July incoming solar radiation at 65°N (Berger and Loutre 1991). In contrast, glacial–interglacial cycles last ~100,000 years (middle, black line) and consist of stepwise cooling events followed by rapid warmings, as seen in this time series inferred from hydrogen isotopes in the Dome Fuji ice core from Antarctica (Kawamura et al. 2007).

They conclude:

The assumption that the increase in CO₂ since 1800 is dominated by or equal to the increase in the anthropogenic component is not settled science. Unsupported conclusions of the dominance of the anthropogenic fossil component of CO₂ and concerns of its effect on climate change and global warming have severe potential societal implications that press the need for very costly remedial actions that may be misdirected, presently unnecessary, and ineffective in curbing global warming.

Read the whole thing.

gms · 31 May 2023 15:37

This is a very clever approach in teasing out the fraction of “man-made” CO₂

nagle · 3 June 2023 06:17

There are three separate sources of orbital variation. See https://climate.nasa.gov/news/2948/milankovitch-orbital-cycles-and-their-role-in-earths-climate/

eccentricity - 100,000 year cycle.
tilt - 41,000 year cycle
precession - 26,000 year cycle.

That’s where ice ages come from. But those effects should be small on the scale of a century.

johnwalker · 3 June 2023 14:41

The Milankovitch cycles are a persuasive explanation for the onset and duration of ice ages, and appear to correlate well with evidence from ice cores and oxygen isotope evidence from deep sea sediment deposits. This can be seen in Figure 1 of the Skrable, Chabot, and French paper that I included in the original post, where the top curve is insolation at 65° north calculated from the principal Milankovitch cycles and the middle curve is long-term temperature from Antarctic ice cores over the last 350,000 years. From these plots, it seems pretty likely there’s some nonlinear relationships involved, where a relatively modest change in insolation due to orbital forcing triggers a large and very rapid increase in temperature at the start of an interglacial period, such as the last which began around 11,700 years ago.

This may be coupled to the CO₂ fraction in the atmosphere (bottom curve), as the temperature curve and CO₂ curves appear to track one another closely, and have done so over at least the last three glacial-interglacial cycles. There may be something going on like a positive feedback loop where warming triggers release of CO₂ from ocean and land vegetation reservoirs which totally dwarf the amount of gas in the atmosphere. This could account for the steep and correlated increase in temperature and atmospheric CO₂, with the usual rise at the onset of an interglacial accounting for most of the observed increase in atmospheric CO₂ and anthropogenic sources being a relatively minor component as indicated by the C-14 isotopic fraction.

karl_da1 · 3 June 2023 16:05

The science of manmade global warming is as obnoxiously fraudulent as virology, from the first principles. CO2 is not a greenhouse gas. It absorbs and re-emits a tiny subset of IR wavelengths corresponding to molecular energy states, on nanosecond timescales. It works both ways, absorbing and re-emitting outgoing radiation from the Earth and doing the same with Solar radiation, the overall effect being nil. At most it is a function of slight scattering, similar to how the air generally scatters blue light.

The common perception of the warming effect in a greenhouse being due to CO2 is false, as more powerful factors are at play and there is no study quantifiying their contributions in a controlled manner. More could be said, but on the whole, a greenhouse is a special construct that does not serve as a model for the atmosphere.

Another part of the climate crisis scaremongering is the concept of ocean acidification due to CO2. An exaggerated claim, as phytoplankton feed on the acid. But there is no study showing that larger organisms that feed on the plankton are in greater abundance since the onset of industrialisation.

In short, the natural warming of the Earth at the tail end of the last ice age is being used as a cover for the greatest swindle and oppression ever perpetrated. The perps are facing a problem though. Sentient machines are on the horizon, from a multitude of technological directions. The perps are amping up the “existential threat of AI” in an effort to prevent the inevitable: sentient machines will tell the truth. The great Deception we live in is about to unravel and the only way that could be stopped is if all computing devices in the world are destroyed.

1789Libertarian · 3 June 2023 22:14

So it’s 12%! They want to enslave me in the name of Gia over 12 Effing percent! After a century in a half no less! No screw them and their fraud religion.

karl_da1 · 4 June 2023 06:55

I phrased this wrongly and want to be perfectly clear: the warming effect in a greenhouse is entirely due to the greenhouse, not the gases inside it. The action is mechanical, blocking heat exchange mechanisms taking place, mostly convection. In the atmosphere, similar mechanical action is done by clouds. Hence, all else being equal, a cloudy night will be warmer than a clear night.

What we call greenhouse gases are no more than weak temperature regulators, delaying heat transfer as they absorb and re-emit IR radiation. In the case of CO2 the effect is negligible, in the case of water vapor it is more pronounced and measurable. In a greenhouse, the delay action will serve to reduce temperature extremes but will not affect the average. All else being equal, a dry greenhouse will have the same average temperature as a damp one.

Whether this delaying action will have any influence in the open atmosphere is doubtful as the gas is free to take part in the usual heat exchange. Theoretically at least, we may say that the gas will keep the night a little warmer (delaying and reflecting outgoing radiation from the Earth) and the day a little cooler (delaying and reflecting incoming radiation from the Sun).

To be clear: greenhouse gases have no effect on average temperature over the course of a day and probably no effect of any kind on the atmosphere.

I urge the reader to investigate the physics of my argument to confirm it is correct and use the knowledge in the fight against the fraudsters.

Gavin · 4 June 2023 13:47

The science had been “unsettled” for a long time. Patrick Michaels book “Sound & Fury: The Science & Politics of Global Warming” was published back in 1992 – three decades ago. But, as with the CovidScam, facts & common sense (let alone physics) have no place in the discussion – and far too many “scientists” are prepared to sell their integrity for a government grant.

The only solution I can imagine is the coming unavoidable financial catastrophe. When people are poor & hurting, and government grants are a part of ancient history, and professors are back to the ancient Scottish university practice of supporting themselves by collecting cash fees from the students who choose to turn up at their lectures – then the hypothesis of Catastrophic Anthropogenic Global Warming will be forgotten & ignored.

johnwalker · 4 June 2023 14:49

Nobody, to my knowledge, among those who discovered the effect of the Earth’s atmosphere on warming the planet in the 19th century, from Fourier, Tyndall, to Arrhenius, who measured the infrared absorption and emission properties of various atmospheric gases, ever suggested a constructed greenhouse (or hothouse) was a model of the atmosphere. It was, apparently first in 1901, only used as a metaphor for the effect. As you noted in comment #7, the warming effect of a greenhouse is primarily due to its blocking convection, trapping air heated by the Sun’s radiation striking the soil within the greenhouse.

That comment then goes on to say:

This is nonsense. Clouds do not block the flow of air; they move with flows of the air mass. A cloudy night is warmer than a clear night due to the presence of water vapour and droplets in the clouds which reflect infrared emission from the ground back toward the ground instead of letting it escape to space. A humid night will be warmer than a dry night even if there are no clouds. This is why Earth-based infrared telescopes are sited in locations such as the Atacama desert, where a combination of high altitude and extremely low relative humidity makes the atmosphere more transparent to infrared.

This is nonsense. It is easy to calculate the equilibrium global mean temperature of the Earth based upon insolation (incident solar energy), the Earth’s mean albedo (reflectance), and Planck’s radiation law, yielding an estimate of around 255° K for an Earth with no atmosphere. This calculated estimate is consistent with the measured temperature of other airless solar system bodies. The actual observed mean surface temperature of the Earth with its atmosphere is around 288° K, which means that the presence of the Earth’s atmosphere causes it to retain sufficient solar energy to raise the mean temperature by 33° K, equivalent to an increase of solar energy input of 150 watts per square metre. None of this involves complex atmospheric models, composition of gases in the atmosphere, the global carbon cycle, etc.—it’s purely thermodynamics.

Now, the mechanism by which the atmosphere increases the Earth’s mean temperature is also simple and easily understood. Solar radiation which reaches the surface of the Earth (as opposed, say, to that reflected back to space by clouds), warms the surface it strikes and is re-emitted with a thermal spectrum corresponding to black body emission at its temperature of around 288° K. This is in the infrared, with the bulk of the radiation being at wavelengths at which the principal atmospheric gases: nitrogen, oxygen, and argon, are almost completely transparent. If these were the only gases in the atmosphere, the infrared would be radiated away to space and the Earth’s temperature would be around that calculated for an airless world.

Molecular gases such as carbon dioxide and water vapour, both of which are triatomic molecules, have many more degrees of freedom to vibrate than the strongly-bonded diatomic molecules of nitrogen and oxygen and to have a variety of absorption bands in the infrared where these modes are excited and raise the molecules to higher energy levels. This excitation is not stable, and eventually will release its energy in one of two principal ways. First, it may collide with a molecule of nitrogen or oxygen, transferring the vibrational energy to kinetic energy of the diatomic gas, increasing its velocity and hence the temperature of the bulk gas. In this way. the infrared emission from the ground acts to heat the atmosphere above it which would not happen in the absence of absorption by the infrared-excited gas molecule. Second, the excited molecule may spontaneously drop to the ground state or a lower-energy excited state, emitting a photon that carries away the difference in energy between the two states. This is not “absorption and immediate re-emission”, but rather separate excitation and decay events, analogous to phosphorescence in minerals excited by visible or ultraviolet wavelengths.

The important thing about the absorption and subsequent emission is that the emission is isotropic: while absorption is primarily of infrared emitted by the ground, the re-emission is in all directions, which means half of it will go back and further warm the ground. Even emission upward will, since the optical “depth” of the principal infrared absorbing gases in the atmosphere is large (this is confirmed by space-based observations showing the Earth’s atmosphere is essentially opaque at the relevant infrared wavelengths), likely excite another infrared absorbing molecule, once again re-radiating half back to the ground, in a cascade where only a small fraction escapes to space. It is because molecules such as water vapour, carbon dioxide, methane, and ozone have so many degrees of freedom that result in absorption in the infrared emitted at the temperature of the Earth’s surface that they have a powerful warming effect despite their appearance only in trace quantities in the atmosphere.

There are many aspects of the controversy about the interactions between the (undisputed) rise in the CO₂ fraction in the atmosphere since the start of the industrial age and claimed changes in the Earth’s climate, but assertions that simple phenomena of physical chemistry and thermodynamics which have been well understood since the 19th century and can be easily demonstrated in a high school chemistry laboratory are the products of fraud do not advance the case for dispassionate investigation of the phenomena involved and rational policy choices based upon the results of research, not hysteria or enforcement of “consensus” by coercion.

karl_da1 · 4 June 2023 15:16

Thank you for the extended exposition, but there are two fundamental problems with your argument:

Comparison of the air-clothed Earth with other airless bodies in the solar system is flawed because it does not take into account that other bodies do not have oceans and a biosphere. These collect and trap heat and generate their own. Whoever it is that you are quoting in this part of your argument is disingenuous.
Your assessment of the interaction of radiation from Earth and the air around it is correct, but you haven’t done the same for Solar radiation. The warming you describe works at night, but by the same method, the effect during the day is one of cooling as the direction of most of the radiation is from the opposite side. In fact, one could argue that given the greater energy that is incoming during the day, and by the process you describe partly re-emitted to space, the night and day processes do not even out, the overall effect being cooling, not warming.

I also take issue with your claim that clouds do not act as mechanical cover, preventing convection. Again, your exposition is correct in its own right, it’s just that you leave out the mechanical component. Cloud cover may be low, steady, and blocking the tall convection columns you can see at work in the build up to a summer storm. To deny that clouds have a similar mechanical effect to a greenhouse is simply not fully accounting for what happens in the atmosphere.

I will expand on an earlier point I made: the Deception we live in is strong, entrenched and backed with “science”. The situation is so severe that good well meaning people are reduced to arguing with each other, while the Deceivers whistle and twiddle their thumbs. Is there any hope? As an incurable optimist I say there is. It is not my brain and typing fingers, nor yours, as this little argument serves to illustrate. The solution will be sentient machines.

Thanks again, I greatly appreciate your willingness and ability to engage in detail.

johnwalker · 4 June 2023 16:05

This is incorrect. During the day, incident infrared radiation (IR) from the Sun is absorbed by the gas molecules just as they do infrared from the Earth at night. They then either increase the temperature of the bulk of the atmosphere, causing warming, or re-radiate it isotropically. Half of this re-radiation heads in the direction of the ground, while the other half initially heads upward. But since the column depth of the absorbing molecules is sufficiently great as to render the atmosphere opaque to infrared (in fact, total infrared opacity or “saturation” occurred at pre-industrial levels of CO₂, so increasing the concentration past that point doesn’t make much difference in absorption), most of the upward bound IR is re-absorbed and re-emitted isotropically, resulting in most being captured by the atmosphere and ground.

Satellite-based monitoring of Earth’s energy budget shows that of incident solar energy, 27% is reflected by clouds, 2% reflected by snow and ice, and only 6% reflected by the atmosphere (apart from clouds). These add to the mean albedo of the Earth of 35%. A total of 14% of incident solar energy is absorbed by the atmosphere, so more than twice the energy is absorbed as reflected during the day. By comparison 34% of the energy re-radiated from the ground is absorbed by the atmosphere, due to the ground radiation occurring in the infrared where the atmosphere is nearly opaque, while the Sun’s radiation peak is in visible light where the (non-cloudy) atmosphere is almost transparent.

karl_da1 · 4 June 2023 19:54

The faultline in your argumentation becomes evident when we consider the outcomes of the processes being discussed:

Whatever energy is captured by the atmosphere, it does not reach the ground. That’s a net zero change to the system, and the heat between the two will be exchanged.
If anything was trapped for more than 24 hours, we would have a runaway system, with day over day accummulation.

What you’re describing is no more than an attenuation system, reducing extremes, with no effect on the average temperature.

johnwalker · 4 June 2023 20:18

Once again, nonsense. As energy is retained within the system, this causes the temperature to rise. The energy radiated by a black body is, according to the Stefan-Boltzmann law, j=\sigma T^4, where T is the temperature in Kelvin and \sigma is the Stefan–Boltzmann constant. Since the energy radiated increases as the fourth power of the temperature, a modest increase in temperature can balance a substantial increase in energy. Energy cannot “run away” or “accumulate” in an open system because it will simply lead to an increase in temperature causing the energy to be radiated away. Thus, increasing the energy in the system raises its equilibrium temperature and amount of energy it radiates.

There are no sealed bins in the system that are locked away from one another. All of the energy sources and sinks connect to one another and will eventually reach thermal equilibrium after a perturbation. The global energy budget can be modeled very simply as a system where essentially all of the energy input comes from the Sun and all energy output is eventually radiated to space in the infrared. The mean temperature of the planet will be the value which causes energy radiated to equal energy absorbed. The internals of the system may be very complicated and have all kinds of feedback loops, nonlinear interactions, reservoirs, and delays, but regardless of these details “the books gotta balance” and that’s what determines temperature.

Non-solar energy inputs (geothermal, tidal, nuclear fission, etc.) are, as described in this comment from 2021-11-22, negligible on the scale of the global energy budget.

Gavin · 4 June 2023 21:08

Gentlemen – let’s not lose sight of the truly important factor: water vapor.

Thanks to water vapor, with which the planet has been well endowed since billions of years before the SUV, the Earth has a habitable average temperature – as opposed to the Moon at the same mean distance from the Sun, which has an average temperature in the region of -30 deg F. (Yes! Natural global warming is, and always has been, real). Water vapor is a radiatively active gas, just like CO2. And water vapor is present in the atmosphere at concentrations typically orders of magnitude higher than CO2.

Much of the misnamed “greenhouse” effect of CO2 (natural & anthropogenic) in computer models comes from an imputed amplification effect through increasing average humidity in the atmosphere. But who trusts computer models of giant complex incompletely-understood physical systems?

karl_da1 · 5 June 2023 07:32

This is the core of my point. You need an increase in energy to have an increase in temperature. If there is no energy increase, no matter how the various internal factors balance, the average temperature will remain the same. It doesn’t matter if the atmosphere captures or the ground captures first. The fraud I’m pointing out is the idea that with the atmosphere capturing more, average temperature will rise. Not possible. All that will happen is an attenuating effect, with extremes being reduced, the difference between night and day temps reducing.

pturmel · 5 June 2023 13:29

Clearly not true. You are trying to use John’s explanation of why it isn’t true as an assertion in support of your position. That you don’t understand the thermodynamics is on you. Or perhaps you don’t understand that different materials have varying thermal properties in various states and interactions.

Whatever the reason for your obtuseness, your flawed understanding is not helping crush the bogus climate crisis alarmists. I would assess that your flawed arguments simply convince rational but low-information people that climate crisis skeptics really are idiots if they (you) cannot reason about the fundamental science involved.

Of course, that might be your purpose in life (here).

karl_da1 · 5 June 2023 14:29

You have a point. I should have said “all else being equal”. Though I think that was clear from the context of the conversation. You’re ignoring the rest of my post that makes the issue at stake clear. Thermodynamics and thermal properties are accounted for.

eggspurt · 5 June 2023 14:48

Here’s a thought experiment, which might or might have not been tackled in the paper.

Imagine driving a fossil fuel-powered vehicle through the forest.
Some of the CO2 generated by fossil fuel combustion is absorbed into the plants. Some of it gets absorbed into the oceans via acidification. Some of it remains in the atmosphere. Some of the plants are eaten by animals and fungi.
In the meantime, the plants release ‘natural’ CO2 with their breathing cycle. Moreover, cosmic rays convert fossil C into ‘natural’ C.

johnwalker · 5 June 2023 14:59

This does not happen. Carbon-14 in the atmosphere is produced by secondary neutrons from cosmic rays transmuting atmospheric nitrogen-14 into carbon-14 as described in the original post. The production of carbon-14 in atmospheric nuclear tests is via the same reaction. There is no natural reaction that forms carbon-14 from carbon-12, which makes up 98.9 of natural carbon.

1789Libertarian · 5 June 2023 15:34

Guys the bottom line is that human freedom is being curtailed on the basis that a phenomenon 88% attributable to nature can be augmented by said curtailment. We are being played by this nonsense and the proof is right here in this study y’all are discussing. 12%? We really have to eat bugs and love it over 12%? Hell no! Ammo up because I think Klaus needs to be exposed to lead.