I learned alot from a recent extended discussion at Climate Etc. Causality and Climate responding to a paper Demetris Koutsoyiannis et al. (2023) On Hens, Eggs, Temperatures and CO2: Causal Links in Earth’s Atmosphere.   My previous post on this paper was:

Confirmed: Temperature Drives CO2, not the Reverse

I recommend the discussion thread at climate etc. (on going) as a tutorial for the competing paradigms regarding the CO2 cycle.  I gained clarity from the lead author (a frequent and constructive participant) as well others on the core misunderstanding that has plagued such discussions for decades. Some comments are below in italics with my bolds.

First, note that the paper had a narrowly defined scope:  to demonstrate from available data that changes in atmospheric CO2 lag rather than lead temperature changes.  Because the authors recognized that this finding is contrary to IPCC consensus climate science, appendices were supplied to counter the expected objections crediting human CO2 emissions from hydrocarbons as the main, or sole source of rising CO2 since the Little Ice Age (LIA).  As Koutsoyiannis explained in a summary comment near the end:

Demetris Koutsoyiannis September 29, 2023 at 4:54 pm

I think I have rebutted all the different critiques ON MY PAPERS. I am not going to reply to critiques on any other issues related to the issue of climate. Please make your critiques SPECIFIC, by quoting phrases in my papers that you think are incorrect. And before it, please read the papers.

For example you say:

> And that would be the cause of the CO2 increase in the atmosphere?

If you read the paper you will see that we write (p. 17): *What is the cause of the modern increase in temperature? Apparently, this question is much more difficult to reply to, as we can no longer attribute everything to any single agent. We do not claim to have the answer to this question, whose study is far beyond the article’s scope. Neither do we believe that mainstream climatic theory, which is focused upon human CO2 emissions as the main cause and regards everything else as feedback of the single main cause, can explain what happened on Earth for 4.5 billion years of changing climate.*

We have proposed a necessary condition for causality, which is time precedence of the cause over the effect. I hope you accept that necessary condition, am I wrong? We make our inference based on this necessary condition. Your numbers make no reference of time succession. When you find a way to test whether the direction in time is reversed, that will be great. But for now, all this looks to me an unproven conjecture. I hope you can excuse me that, being a Greek, I have to stick to Aristotelian logic.

You also say:

> While there is an elephant in the room, human emissions that released twice as much CO2 as measured in the atmosphere…

If this is the elephant, what is (copying from our paper, p. 25), *a total global increase in the respiration rate of ΔR = 31.6 Gt C/year. This rate, which is a result of natural processes, is 3.4 times greater than the CO2 emission by fossil fuel combustion (9.4 Gt C /year including cement production)*.

My Comment: The confounding issue in all this was identified as the mistaken analogy treating CO2 fluxes as though they are cash transactions between bank accounts.  Within that notion, a natural source/sink must net out intakes and releases.  Yet as others commented, geobiologists know that both absorption and release can be increasing or can be decreasing.  The source/sinks function dynamically, not statically as assumed by the analogy.

clydehspencer | September 29, 2023 at 3:07 pm | 

“Our knowledge of net global uptake over this period is good to 15%.”

How do you justify making such an assertion when no one has mentioned what is happening in the Arctic, the NASA observation of ‘greening,’ and the utterly unknown situation of submarine volcanic emissions?

How do you propose to identify and dismiss spurious correlations?

Ferdinand Engelbeen | September 29, 2023 at 4:13 pm |

Clyde as said elsewhere, we do not need any natural flow for the carbon balance: that is exactly known from human emissions minus increase in the atmosphere: that is exactly what nature did in the same year: always more sink than source in the past 60 years…

Agnostic | October 1, 2023 at 4:23 am |

“In detail: both the oceans and vegetation are proven, increasing (!) sinks for CO2, thus these two can’t be cause of the increase in the atmosphere.
It really is that simple…”

And ironically, this is exactly where you are wrong. Just because they are increasing as sinks does not mean they cannot be increasing as sources. I think you are too stuck on the idea of a “budget”, it’s a linear view. It’s the “net” thing that is where the misunderstanding is.

The biosphere is indifferent to our contribution. If there is more CO2 available it will expand regardless of where it came from. Temperature increase, particularly in winter, means that more CO2 is released in biodegradation than normal. If it releases more than is fixed during the summer growing season, then atmospheric CO2 levels will increase.

During the growing season, if there is more CO2 available, then the biosphere can grow more vigorously and expand. Some of this is semi-permanently fixed, and some will only fix during the growing season to be available to be released as CO2 during the next winter.

If the humans made no contribution, the atmospheric CO2 would still go up, though perhaps not by as much, just as it did in other warm periods during the holocene. This “budget” idea is what is causing the confusion.

Agnostic October 1, 2023 at 4:02 am 

Ferdinand writes: “If humans are not to blame, what is the “other” source (both oceans and vegetation are increasing net sinks) and where resides all that human CO2?”

The same question has to be asked to explain the high variability of CO2 atmospheric concentration prior to industrialisation. The CO2 had to come from somewhere: during the MWP it was as high as 380-390ppm before dropping to 285ppm. During the Bolling-Allerod CO2 increased to as much as 420ppm while temps were actually cooling, a break in the pattern of Temp leading CO2 which holds over all timescales.

The answer is that the biosphere is massively more complex than you are appreciating. You claim that the biosphere is net sink because our emissions are grater than the amount that atmospheric CO2 is rising, but that thinking is too simplistic. It is likely, almost certain given previous periods of warming, that atmospheric CO2 would have risen anyway, but perhaps by not as much, which is our contribution.

The biosphere is expanding because more CO2 is available and is therefore a source as well as a sink. Were we not contributing our share, it would be a net source.

Agnostic | October 1, 2023 at 5:38 am |

“All the variability is in the net sink (not source!) rate of CO2 into nature, while sinks are increasingly negative and temperature is slightly increasing over the same time 60+ years time span…
Thus temperature is NOT the cause of the increase.”

No – this is where you are completely wrong.

The source is ALSO variable. Highly variable. The sinks which you describe as “variable” are ALSO sources, they are interdependent and non-linear in their relationship.

During the growing season, some of the growth fixed via photosynthesis is trapped and some decays during the winter. How much decays is predominantly temperature dependent. The is why you see CO2 follow temperature on ALL timescales that we reliably measure.

Agnostic | October 1, 2023 at 5:33 am | 

Processes that release C into the atmosphere (biodegradation) are far more temperature dependent than processes that fix it (photosynthesis). So there is already a systematic imbalance regardless of anything we do. It is not just a linear “budget”.

During cooler periods, the rate at which CO2 is removed is greater than the rate at which it is released, leading to lowering of CO2 in atmosphere such as LIA. During periods of warmth, especially winter, more CO2 is released than is fixed leading to an increase. But the relationship is not linear.

As more CO2 is available, the transient biosphere expands and grows more vigorously. Some is trapped and some is released at the end of the season. How much is released is dependent on warmth (and to a lesser extent moisture in soils).

We hear the biosphere being described as a “net sink” which is growing because humans emit more C than is remaining in the atmosphere. But it is faulty thinking.

If we did not contribute, then atmosCO2 would still go up, making the biosphere a “net source”. That’s because the biosphere expands and contracts depending on how much CO2 is available and how warm it is. The CO2 comes from trapped sources particularly in the soils, released by increased temperatures which is a much larger overall source than human emissions.

IMO, it is better to think of carbon sources and sinks as dynamic reservoirs that are never perfectly in balance and which have a non-linear relationship with each other. We contribute to the source side, but the biosphere can’t tell the difference between man’s CO2 and naturally emitted, so characterising it as “budget” is where the confusion arises. The “budget” is always changing in non-linear interdependent way. It is not fixed.

Agnostic | October 1, 2023 at 7:59 am |

I have read other similar papers that came to the same conclusion, one in particular by statistician. They were adamant that from a statistical POV you cannot claim causality the way round it is traditionally viewed.

I am NO expert on the carbon cycle, by any means. But it has been bone stuck in my head for a long time because I AM interested in paleoclimatological record. Ice core data is what is generally used to show that CO2 levels are at “unprecedented levels”, yet we know that ice core data is unreliable and too low resolution to speak about short intervals of warming of 300 to 400 years which we appear to be in.

High resolution proxies clearly show similar concentrations of CO2 in the atmosphere
to today, yet that is not put into context. Where did THAT CO2 come from?

The other thing that bothers me is the “budget” approach to CO2 as if there was a fixed amount of C that can be released or absorbed yearly. Yet just the tiniest forays into biodegradation and soil hydrology shows how an incredibly complex and interdependent picture it is, and that’s to say nothing of the oceans.

As usual with climate science, conclusions are made to support a narrative
or a pre-existing conviction and the complexity be damned.

Footnote:  What It Means:  CO2 flows through Dynamic Reservoirs

The other puzzle piece is described by Ed Berry following his peer-reviewed paper Nature Controls the CO2 Increase II.  A summary comment ties his analysis into the above discussion.  Early in the thread the point was made that all CO2 sources are involved in supporting the level of atmospheric concentration at any point in time. Ed Berry made this point  in this way.

He explained that when you look at the flow of carbon dioxide—”flow” meaning the carbon moving from one carbon reservoir to another, i.e., through photosynthesis, the eating of plants, and back out through respiration—a 140 ppm constant level requires a continual inflow of 40 ppm per year of carbon dioxide, because, according to the IPCC, carbon dioxide has a turnover time of 3.5 years (meaning carbon dioxide molecules stay in the atmosphere for about 3 1/2 years).  140 ppm divided by 3.5 is 40 ppm CO2.

“A level of 280 ppm is twice that—80 ppm of inflow. Now, we’re saying that the inflow of human carbon dioxide is one-third of the total. Even IPCC data says, ‘No, human carbon dioxide inflow is about 5 percent to 7 percent of the total carbon dioxide inflow into the atmosphere,’” he said.

[Today’s level of nearly 420 ppm means that 120 ppm of inflow is required annually, or 120 +2 ppm if it is to increase as it has been.  Where does 122 ppm of CO2 come from?  Well, let’s say we can count on 6 ppm of FF CO2 (5%) and  the other 116 being non-human emissions.]

So, to make up for the lack of necessary human-caused carbon dioxide flowing into the atmosphere, the IPCC claims that instead of having a turnover time of 3.5 years, human CO2 stays in the atmosphere for hundreds or even thousands of years.

“The removal of human-emitted CO2 from the atmosphere by natural processes will take a few hundred thousand years (high confidence). Depending on the RCP scenario considered, about 15 to 40% of emitted CO2 will remain in the atmosphere longer than 1,000 years. This very long time required by sinks to remove anthropogenic CO2 makes climate change caused by elevated CO2 irreversible on human time scale.” Source:Chapter 6 Working Group 1 AR5

“[The IPCC is] saying that something is different about human carbon dioxide and that it can’t flow as fast out of the atmosphere as natural carbon dioxide,” Mr. Berry said. “Well, IPCC scientists—when they’ve gone through, what, billions of dollars?—should have asked a simple question:

‘Is a human carbon dioxide molecule exactly identical to a natural
carbon dioxide molecule?’ And the answer is yes. Of course!

“Well, if human and natural CO2 molecules are identical, their outflow times must be identical. So, the whole idea where they say it’s in there for hundreds, or thousands, of years, is wrong.”

Footnote: 

A commenter summed up the discussion this way:

Botanist | November 2, 2023 at 9:09 pm |

Until a few weeks ago I’d always thought like Ferdinand. This elegant paradigm (below) now seems so simple and obvious, I’m not sure how I did not see it before reading the Hens paper and the article hereabove and contemplating certain helpful comments hereabove. Am I crazy; this strikes me as genius. Can something so simple be.

” My premise is that nature does not make individual balance per source but works holistically. Hence, my version of the carbon balance is roughly this:

Ins: 4% human, 96% natural
Outs: 0% human, 98% natural.
Atmospheric storage difference: +2%
(so that: Ins = Outs + Atmospheric storage difference)

Balance = Atmospheric storage difference: 2%, of which,
Humans: 2% X 4% = 0.08%
Nature: 2% X 96 % = 1.92%
where 1.92% : 0.08% = 2400% “