On Hens, Eggs, Temperatures and CO2: Causal Links in Earth’s Atmosphere
December 13, 2023
By Paul Homewood
This paper came out in September:
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In short it finds that increasing levels of carbon dioxide in the atmosphere are the result of higher global temperature, and not the other way round:
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NOT A LOT OF PEOPLE KNOW THAT 
This has been known for years, but nobody is allowed to learn the truth or the climate change scam would end along with a lot of careers etc.
Judith Curry gave as an answer to the question as to why so many scientists support the AGW theory, ‘Fame and Fortune’.
It is interesting that once they have retired they adopt a more questioning attitude.
I thought that idea died during The Pause, when CO2 continued increasing at roughly the same rate as before.
It is a slow process not a sudden one. Just as if were it true that CO2 warms the planet then it was impossible for the surge in hot weather is Europe to be due to CO2.
“These developments include an advanced theoretical framework for testing causality based on the stochastic evaluation of a potentially causal link between two processes via the notion of the impulse response function”
That kind of sciency gobbledygook is normally deployed by the Attribution crowd, it sounds like BS to me.
Argumentum ad ignorantium.
Lack of evidence for one theory is not evidence for another theory.
“These developments include an advanced theoretical framework for testing causality based on the stochastic evaluation of a potentially causal link between two processes via the notion of the impulse response function”
Yep. That’s a long-winded name for, model.
This is describing a mathematical technique for testing causality – Koutsoyannis has published previously on the technique itself. It is NOT a model. The relevant papers are in the references of this paper, particularly #6 & #7.
Think of temperature as the fire, and CO2 as the fire engine.
Wasn’t this the outcome from the Vostok ice cores analysis? But as Phillip B states, blasphemy now to even think it.
I’ve read Koutsoyiannis et al 2023, and, like their previous work, it’s wrong.
(Frankly, I’m amazed by the number of people who seem confused by the fact that adding something to the atmosphere increases the amount of it in the atmosphere. That’s not exactly rocket science.)
Koutsoyiannis et al are apparently confused by short term fluctuations in CO2 levels, which are caused by natural factors. They think the phase relation between temperature and CO2 level fluctuations implies that temperatures drive CO2 level.
That’s incorrect. When periodic variations of different things are correlated, it is always a mistake to draw conclusions about causality without considering the underlying mechanisms — which Koutsoyiannis et al unfortunately ignore.
As it happens, the reason for the short term correlation between CO2 levels and temperature levels is obvious, and it does not imply causality in either direction.
Although CO2 and temperature do affect each other, those effects are too slight to significantly contribute to the observed short term correlation between them. Instead, the correlation is caused by the fact that both CO2 levels and temperature levels are affected by sunlight.
Increased sunlight during spring and summer obviously raises regional temperatures. It also also causes plant growth, which removes CO2 from the air, reducing CO2 levels. Conversely, reduced sunlight during fall and winter lowers temperatures, and causes leaves and grasses to rot and release CO2, raising CO2 levels.
So the phase-offset seasonal correlation between CO2 and temperature does not imply causality in either direction. Instead, the correlation is caused by the fact that both are affected by sunlight.
Humlum et al 2013 has similar issues, so I suggest that you read the “comment on” responses to it, which you can find here:
https://scholar.google.com/scholar?q=%22Comment+on%22+Humlum+%22Phase+relation%22
We know from the physics of the (poorly named) greenhouse effect that rising CO2 levels have a warming effect.
We also know from the temperature dependence of Henry’s Law that temperature changes slightly affect atmospheric CO2 levels, though that effect is dwarfed both by accelerated natural CO2 removals as CO2 levels rise, and by anthropogenic CO2 emissions.
The fact that temperatures and CO2 levels affect each other makes the relation between them a feedback loop, but it’s a very weak one. You can read about it here:
https://sealevel.info/feedbacks.html#co2watertemp
If you run the numbers you’ll find that ≥164% of the CO2 increase since 1958 (when precise measurements began) was due to human CO2 emissions. That’s not a typo. The amount of CO2 in the air increased much LESS than the amount we’ve added. That means Nature is removing CO2 from the atmosphere, not adding it.
Now I’ll show you the numbers, and the math. Buckle up!
First, consider the anthropogenic emissions:
Here’s a spreadsheet of data from the Global Carbon Project (except that I’ve converted their MtCO2 figures to MtC):
https://sealevel.info/carbon/global.1751_2021.ems13.txt
https://sealevel.info/carbon/global.1751_2021.ems13.xlsx
Here’s the same spreadsheet, to which I’ve added a couple of rows with summed emission data for 1959-2021 (rows 290 and 291):
https://sealevel.info/global.1751_2021.ems13_with_sums_for_1959-2021.xlsx
Aside (conversion factors):
1 PgC = 3.66419 Gt CO2.
1 ppmv CO2 ≅ 7.8024 Gt CO2 = 2.1294 PgC.
The GCP’s emission data shows:
185.58 ppmv of fossil carbon emissions.
(Note: only 5.56 ppmv of that is listed as CO2 from cement manufacturing. That’s the CO2 released from CaCO3 (limestone) as it’s baked in the kiln. It is commonly claimed that cement manufacturing is responsible for up to 8% of all anthropogenic CO2 emissions, but that figure includes an estimate of emissions from the fossil fuels which are burned to heat the kilns, typically accounting about half of the total CO2 emissions from cement manufacturing, though that varies according to how the kiln is fired.)
In addition to fossil CO2 (from burning fossil fuels and making cement), the GCP estimates that 24.67 to 53.20 ppmv of CO2 has been released since 1958 due to “Land Use Changes” (average of 3 studies = 39.98 ppmv). Obviously, those figures are poorly constrained.
185.58 + 24.67 = 210.25 ppmv (their smallest estimate which includes averaged land use emission estimates).
185.58 + 39.98 = 225.56 ppmv (their total including averaged land use emission estimates from 3 studies).
185.58 + 53.20 = 238.78 ppmv (their largest estimate which includes averaged land use emission estimates).
If we add a generous ±10% uncertainty to those figures, we can say with very high confidence that during the years 1959 through 2021 (inclusive) mankind added 167 to 263 ppmv of CO2 to the atmosphere.
Now, consider the atmospheric CO2 measurements. These are from Mauna Loa:
https://sealevel.info/co2.html
(Hover your mouse over the CO2 trace to see the data for any date.)
They show:
1958 CO2 level (extrapolated from a partial year of measurements): 315.34 ppmv
1959 CO2 level: 315.98 ppmv
Estimated seasonally adjusted CO2 level at start of 1959 = (315.34+315.98)/2 = 315.66 ppmv
2021 CO2 level: 416.45 ppmv
2022 CO2 level: 418.56 ppmv
Estimated seasonally adjusted CO2 level at start of 2022 = (416.45+418.56)/2 = 417.505 ppmv
Total increase in CO2 level from start of 1959 to start of 2022 = (417.505 – 315.66) = 101.845 ppmv
Now we’ll do the arithmetic:
Thus we now know that, since 1958 (through 2021):
● mankind has added 167 to 263 ppmv of CO2 to the atmosphere (probably between 185 and 239 ppmv).
● the amount of CO2 in the atmosphere increased by only 102 ppmv.
● So, nature has removed a net total of ((185 to 239) – 102) = 83 to 137 ppmv CO2 from the atmosphere.
(167/102) ≅ 164%
(263/102) ≅ 258%
So:
● 164% to 258% of the increase in atmospheric CO2 concentration since 1958 was anthropogenic.
That’s proof that more than the entire increase in atmospheric CO2 concentration since 1958 is man-made.
Q.E.D.
Note that to deduce that fact we don’t need any models (Bern, or any other). We don’t need isotope data. We don’t need to know residence times, turnover times, or adjustment times. We don’t need to estimate flows between individual carbon reservoirs. We don’t need to know anything at all about the many individual natural CO2 fluxes. And, since we’re using whole-year averages, we don’t need to know anything about vegetation-driven and temperature-driven seasonal patterns or how they differ with latitude.
Many of those things are interesting, and some of them are important for other reasons, but they are irrelevant to the proof of the fact that all of the increase in atmospheric CO2 concentration since 1958 is due to human emissions.
70% of the Earth’s surface is ocean. Warmer waters absorb less CO2.
Yes, brew, the temperature dependence of Henry’s Law means that a 1° C increase in surface water temperature slows CO2 uptake by the oceans by about 3%. It is a form of positive climate feedback, albeit a minor one. It’s called “CO2 / Water Temperature Feedback.” I linked to a discussion of it, above:
https://sealevel.info/feedbacks.html#co2watertemp
The 50% increase in atmospheric CO2 concentration (280 → 420 ppmv) accelerates CO2 uptake by the oceans by 50%. Since 50% is much greater than 3%, the impact of CO2 / Water Temperature Feedback is very slight.
We know from ice cores that the warming from glacial maximums to peak interglacial optimums over the last 400,000 years has been associated with atmospheric CO2 level increases of only about 90 ppmv (from about 190 ppmv to about 280 ppmv), as global ice sheet expanse decreased by more than 60% and global average temperatures increased by 6±2°C.
Note that it took at least 4°C of global warming (probably more), over thousands of years, to yield just 90 ppmv of CO2 level increase.
In contrast, since 1910 the atmospheric CO2 level has increased by about 120 ppmv, even though average surface water temperatures increased by only about 1°C, and global ice sheet expanse didn’t decrease at all.
https://www.woodfortrees.org/plot/hadsst3gl/mean:12/plot/hadsst3gl/from:1910/trend
I want to thank Dave Burton
for writing a good article
disguised as a comment
My much simpler version
although less precise
because it starts with proxy
estimates rather than
direct real time measurements:
Manmade CO2 emissions since 1850 roughly +250ppm
Atmospheric CO2 increase since 1850 roughly +140ppm
Manmade CO2 emissions absorbed by nature roughly 110ppm. or 44%
Most scientists round the percentage to 50%
The important point is not where the extra CO2 came from
The important points are that more CO2 greened our planet, improved plant growth and mainly caused slightly warmer winter nights in cold places like Siberia.
All good news
More CO2 = more life on our planet
CO2 as a feedback in the ice core era
Approximately +/- 17ppm
atmospheric CO2 level change
for each +/- 1 degree C. change
of the average ocean temperature.
over about 100,000 years
Quoting pseudo precision of 5 significant figures in numbers that have considerable uncertainty is a tactic aimed at the ignorant. Start with the IPCC estimates of the stocks and flows (recognising that they are subject to errors of measurement).
We have known this from when the first Antarctic cores were drilled.
When CO2 is high, the world cools.
When CO2 is low, the world warms.
This would not happen, if CO2 was a powerful warming feedback agent.
R
The reason this happens is:
a. Cooling.
A Great Winter (Milankovitch Minima) can cause cooling and an ice age.
b. Warming.
Dust in ice sheets lowers their albedo and causes warming.
Note: Every interglacial is preceded by 10,000 years of dust.
R
If changes in planetary geometry cause the cooling then they also cause the warming. A full cycle takes about 100.00 years. It makes no sense to imply that a full cycle only causes cooling but no warming.
Not in this case.
The reverse feedback agent in this case is high Arctic ice sheet albedo, and this effect is SO strong it can easily prevent further warming.
This is why subsequent very strong Milankovitch Maxima often produce no warming whatsoever. See 170 kyr ago.
https://i0.wp.com/www.wmbriggs.com/wp-content/uploads/2023/03/iceage1.webp?fit=1173%2C431&ssl=1
R
I assume that this is data from just one site in Antarctica, homogenized to cover the whole planet. I would like to see error bars as well.
This is now from many sites in Antarctica, including Vostoks 1 to 5, Epica 1 to 3, and now Little Dome-C.
R.
It is not based on a temperature from one site. It is based (for temperature) on isotopic oxygen variations in ice formed from water vapour which is well mixed globally.
(mixed)
Another good point.
R
Dave Burton. You are right that abuse of stats and models has caused a lot of damage. The important aspect of this paper, and that by Humlum et al, is that Temperature rise is shown to precede CO2 rise. If it showed the opposite effect we would certainly have known IN CAPITALS. The proof for both claims is being hotly denied by the AGW advocates, but they have not disproved it, nor shown any evidence that CO2 rises first. While still debatable, the hypothesis that T precedes CO2 is better proven than the opposite, and accepting this as a theory would be the final stage of kicking out the “greenhouse farce”.
Jack, over the last 400K years, until mankind began adding CO2 to the atmosphere, the ice cores show that reversals in CO2 trend lagged temperature trend reversals by 100s of years.
But note the past tense (“lagged”). It is no longer the case that CO2 level trend reversals lag temperature trend reversals.
In fact, CO2 levels rose steadily from the 1940s through the 1970s, even as temperatures fell. That’s not because falling temperatures didn’t reduce atmospheric CO2 levels (slightly). It’s because falling temperatures didn’t reduce atmospheric CO2 levels as rapidly as anthropogenic CO2 emissions increased atmospheric CO2 levels.
Why do I have permanent notifications all over this page?
Is anyone else getting this?
R
More trees sacrificed on the green energy altar.
A new overhead power line to link wind farms to the electricity network will require 50 hectares (120 acres) of trees to be felled along its path.
Dumfries and Galloway Council has been advised not to oppose the six mile (9.2km) Glenmuckloch to Glenglass scheme.
https://www.bbc.co.uk/news/articles/c6pd2eqnv1go
Advised not to oppose, told not to. By whom? Would save legal fees for no chance of winning.
Signed
D and G Council tax payer
Similarly, via the well known BBC reporting funded from ‘Local Democracy Reporting Service’, journalist Donald Turvill reports
https://www.bbc.co.uk/news/articles/clkwgx2l2d7o
I take on board what Dave Burton is saying, although the maths etc is beyond me, but I have seen little scientific research that CO2 is responsible for global warming which is the crux of the argument in this climate debate. It’s undeniable that we are pumping out massive amounts of CO2 but to say that it is the only factor in the changes of climate is a stretch in my opinion.
Indeed. We know from the physics that additional CO2 must have a slight warming effect, but there’s no reason to suppose that it is harmful. In fact, scientists call the warmest climate periods “climate optimums,” because they’re objectively better than cold periods.
However, climate is more than just temperature. The 50% increase in atmospheric CO2 concentration has had only a small effect on temperatures, but it is of large benefit for crops, and other plants.
Old Days
Holocene Climate Optimum
at least +1 degree C. warmer
than the past decade
Modern IPCC Days
Future climate +1 degree C.
warmer than the past 10 years,
same as the Holocene Climate Optimum,
will NOT be another climate optimum,
but will be a climate emergency.
Same average temperature
Different name
This is modern climate science
Get with the program Mr. Burton!
Build an ark before it is too late
+2.0 degrees C. is no big deal
+2.1 degrees C. and your dog dies
+2.2 degrees C. and we all die
Thi is settled science
From big shot government bureaucrat Ph.D.’s
With really big computers
They’ve been warning us since 1979
Because they knew it would take 50 years
before we decided to listen to them
This is a serious post,
not satire.
Given that the warmists – some of them, at least – acknowledge that CO2 in Earth’s atmosphere is variable, why do some claim that without human interference there is balance in the carbon cycle. Is it not yet another example of their self contradiction.
Junk science claptrap not worthy of space on this website
CO2 can be a climate feedback and a climate forcing
Both DIFFERENT processes happen at the same time
As a feedback, the process is small; and gradual
As a forcing, the process is fast and moderate, but not harmful
There are so many good Paul Homewood articles that I hate to pick on this turkey of an article. But this is junk science mental mass turbation. The authors are clueless.
CO2 is a greenhouse gas and more greenhouse gases in the atmosphere impede earth’s ability to cool itself by some amount.
Known and proven over a century ago.
The authors must have been asleep for a century.
The battle against CAGW is a tough one and we Climate Realists are losing. Claptrap “studies” like this one and some of the science denying comments here will guarantee that no one will take us conservatives seriously
There are virtually no manmade CO2 emissions in the ice core records, therefore those climate reconstructions can not be used to prove anything about manmade CO2 emissions.
Richard Greene
Bingham, Farms, Michigan
My climate and energy blog with over 670,000 lifetime page views
https://honestclimatescience.blogspot.com/