Just as a spitballing exercise, do me one favor and investigate for yourself from additional sources if the "CO2 absorption is saturated at 400ppm” claim really holds in the way you propose. Provide URLs to the reviews or summarize the details in your own words the pros or cons arguments you find. And then I’ll forward links I’ve seen to discussions about that claim.
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In analytical chemistry is it called Beer’s Law. There is a longer title in the link below. Basically, the more of something that is in the path of radiation, the more of that radiation will be absorbed. Meaning that is enough stuff is absorbing, at some point the radiation will all be absorbed.
arXiv:2103.16465v1 [physics.ao-ph] 30 Mar 2021
arXiv:2303.00808v1 [physics.ao-ph] 1 Mar 2023
The claim that CO₂ absorption is “saturated” at 400 ppm is misleading. While the effect is logarithmic—meaning each additional unit has less impact—the greenhouse effect continues to increase with rising CO₂ levels.
Here’s a breakdown of the science and the controversy:
What “Saturation” Means in Climate Physics
- CO₂ absorbs infrared radiation in specific bands. These bands become increasingly opaque as concentrations rise.
- Saturation refers to the idea that once these bands are fully absorbed, adding more CO₂ won’t trap more heat.
- However, this is not entirely accurate. While absorption in the center of the bands is strong, the edges (“wings”) of the bands continue to absorb more as CO₂ increases.
Logarithmic, Not Linear
- The greenhouse effect of CO₂ follows a logarithmic curve:
- The first 100 ppm has a large warming effect.
- Each doubling of CO₂ (e.g., from 280 to 560 ppm) adds roughly the same amount of warming, though less per ppm.
- This means warming continues, just at a slower rate per unit.
Scientific Consensus
- Studies using radiative transfer models (like MODTRAN) show:
- CO₂ is not fully saturated at 400 ppm.
- Doubling CO₂ from preindustrial levels (280 to 560 ppm) is expected to cause ~1.2°C warming from CO₂ alone, and ~3°C with feedbacks like water vapor and clouds holoceneclimate.com scienceunderattack.com.
Misuse of “Saturation”
- Some sources claiming saturation (e.g., CO₂ Coalition, Climate Change Dispatch) are associated with climate skepticism thegreatclimatecon.com CO2 Coalition climatechangedispatch.com.
- Their arguments often ignore the physics of band broadening and feedback mechanisms.
Summary
- CO₂ absorption is not saturated at 400 ppm.
- Warming continues, though each additional ppm has diminishing direct effect.
- Feedbacks amplify the impact, making continued emissions a concern.
Would you like to see a visual model of CO₂ absorption curves or a comparison of radiative forcing across greenhouse gases?
Sources: thegreatclimatecon.com CO2 Coalition holoceneclimate.com scienceunderattack.com climatechangedispatch.com
GPT5
- Infrared absorption bands of CO₂ are centered around 15 microns. While the center becomes saturated, the “wings” of the band continue to absorb more as CO₂ increases.
- Radiative forcing increases logarithmically, not linearly. Each doubling of CO₂ adds roughly the same warming effect, even if the per-ppm impact diminishes.
- Overlap with water vapor does not negate CO₂’s role. CO₂ absorbs in regions where water vapor is less dominant, especially in the upper atmosphere.
Scientific Consensus
- Models like MODTRAN and data from the HITRAN spectroscopic archive confirm that CO₂ is not fully saturated at 400 ppm.
- Doubling CO₂ from preindustrial levels (280 to 560 ppm) is expected to cause ~1.2°C warming from CO₂ alone, and ~3°C with feedbacks.
Clarifying the “Saturation” Myth
- The idea that CO₂’s effect is capped at 400 ppm is a misinterpretation of radiative physics.
- While absorption at the center of the band is strong, band broadening ensures continued heat trapping.
ib.
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Here are some interesting URLs:
And a paste of a part of an article in the University of Illinois news today concerning wind energy. Lo and behold, they find that the winds over Illinois are slowing down. In the Royal Society study it is reported that a study of historical records indicates low wind velocity can last for periods of up to 3 years. Then there is a court document whose first statement is that “the climate is always changing”.
Case 3:17-cv-06011-WHA Document 157-1 Filed 03/19/18 Page 1 of 26
What? So keep burning carbon. For 30 years.
Don’t invest in HVDC power transmission? Nuclear (including the thorium cycle)? Don’t pave the deserts with greening PV? Don’t cover the coastal waters with wind and water turbines? Don’t pump lakes uphill? Don’t desalinate? Don’t irrigate? Don’t give humanity unlimited, clean, sustainable energy?
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Yes. Beer’s law. In college, we made a T-shirt for us chem majors that said “Always obeying Beer’s Law” over a sketch of a full beer mug. It include a beam of light passing through the mug along with the Beer-Lambert equation. We sold dozens of them, even to non-chem majors and that paid for a round of drinks when Henry Taube visited for a lecture.
Yep, ground level CO2 is efficient at absorbing CO2. As my long worn out T-shirt says, Beer’s law is obeyed, but that’s not the whole story in atmospheric heat trapping. What about the portions of the absorbance spectrum that are not ‘saturated’? (The effect of spectral bands is discussed in the second article referenced below). The consequence is that 300-400ppm of CO2 for the full absorbance bands do not ‘saturate’ for heat retention in the atmospheric column at the concentrations we’re discussing. How does this additional information affect your assessment of the source material? Should we recommend reading more and ‘look under the carpet’ to assess possible complicating details?
Also, one related question: Did you pull up and read the 1971 Science paper you cited? It looks like you posted a picture from another source. Could you forward a link to wherever you got the image? That paper is referenced in a number of later publications which further examine the conclusions relative to other models.
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Thanks for sharing. Could we post those to a separate thread to reduce clutter in this one?
Keep burning carbon for the next 250 years as in the past 250 years. Before 1750 it was wood, and light came from burning olive oil.
Below is a link to the resources needed to power Germany from solar panels in Spain. Clean? unlimited? sustainable?
So they should carry on burning the filthiest brown coal.
Not pave the Spanish sierras, and Morocco, and the Med. Use HVDC to transmit. And turbines on all coasts and on inland wilderness. Not a problem. The PV will green the deserts. Well worth the investment. A grain belt back after millennia in north Africa. We can re-green the Earth. Easily feed ten billion. A hundred in arcologies. All with sufficient. A post-scarcity world. Full utilitarianism. Store as potential energy. Pave the Thar. The Sahara. Arabia. Make everybody happy.
On “adding terms to equations”:
When scientists discover what actually caused something (Dust Bowl = plowing up native grasslands), they include it in models. That’s not fudging data - that’s how science works. It’s like saying “doctors added smoking to explain lung cancer, so they’re just making stuff up.”
On the Christy graph:
Same John Christy from the Alabama graphs. Climate scientists found his graphs use specific choices - baseline selection, inconsistent smoothing, hiding uncertainty - that make “the visual discrepancy between models and observations larger, misleading the reader” as @Argon already said. THIS SHOULD CONCERN YOU that your source, John Christy, is intentionally making graphs to mislead people, and he tricked you, @wbwane . Don’t let him trick you again.
The smoking gun - stratospheric cooling:
Here’s what matters most: the stratosphere (upper atmosphere) is COOLING while the surface warms.
Why does this matter? If the sun was causing warming, it would warm the entire atmosphere. The pattern we see - lower atmosphere warming, upper atmosphere cooling - is the exact fingerprint of greenhouse gas warming, not solar forcing.
A 2023 study found greenhouse gases cooled the stratosphere by 1.8-2.2°C from 1986-2022. Benjamin Santer notes: "This is the clearest evidence of a human fingerprint on the climate system I’ve seen in 30 years.”
This pattern was predicted in 1967 based on CO2 physics. 1967!! As Santer et al. argue:
Our results explain why extending “vertical fingerprinting” to the mid to upper stratosphere yields incontrovertible evidence of human effects on the thermal structure of Earth’s atmosphere.
You can’t fake this. It’s the thermal signature proving CO2 is the driver.
On Russian model conspiracy:
Russian climate scientists publish in the same journals as everyone else. One model matching one metric better doesn’t make it correct - models are validated against dozens of metrics. If they’re secretly keeping the “truth” from the West, they’re doing a terrible job since their scientists keep confirming the same findings as everyone else.
Bottom line:
Models accurately predict global surface temps, sea level rise, Arctic ice loss, ocean heat, stratospheric cooling, and extreme weather. If they were fundamentally wrong about CO₂, they wouldn’t correctly predict all these other things.
Here are 5 common ways science denial works, and I’ve seen all five in this thread so far:
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Fake experts: presenting an unqualified person or institution as a source of credible information
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Logical fallacies: arguments where the conclusion doesn’t logically follow from the premise
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Impossible expectations: demanding unrealistic standards of certainty before acting on the science
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Cherry-picking: carefully selecting data that appear to confirm one position while ignoring other data that contradicts that position
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Conspiracy theories: an explanation for a situation that rejects the consensus view in favor of a secret plot by powerful groups with a malevolent goal
This should concern you @wbwane that your sources argue along these lines.
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You’re joking, right?
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The five common ways you mention are nearly identical to the components in playbook used by the Climate Alarm Industrial Complex to perpetuate their great HOAX on the general public. Surely the largely discredited “hockey-stick” graph is the poster child for cherry picked data. Claiming Richard Lindzen, John Christy, …..two Undersecretaries of Energy Research, Will Happer and Cal Tech Provost Steve Koonin, Nobelist John Clauser “lack expertise” is a fantastic fraud. There is one additional aspect employed by the Alarmist Complex….de-platforming of speakers, and the policy at Science Magazine to reject any papers that did not appear in the denier list. In other words, the HOAX stands on such shaky ground that logical dissent could not be tolerated.
One observation would be that the 35 years of Complex Alarm has FAILED. There was a discussion about the views of climate by pastors. How about lay people. Name the number of churches, especially in the south, that have turned off their air conditioning to “save the planet”. Perhaps a few. How many churches up north have drained their baptistries and turned off the heat in the winter to “save the planet”? Heat is a real luxury in northern climates. Those old monasteries were mostly unheated except for the monks copying the manuscripts. Russian serfs were taxed on the number of chimneys their dwelling used. Those that could not afford the tax lived in places were smoke only exited via hole in the roof and lived rather shortened lives in rather smoke-filled rooms.
In the same sense of Galileo……’yet it moves’ ……”there is no existential threat from climate change” or the burning of fossil fuels. Quoting another…..drill, drill, drill, dig, dig, dig, pump, pump, pump, burn, burn, burn.
One of many of Richard Feynman’s observations was”
Religion is about faith, science is about about doubt.
How did this point come about?
It is called the “heroin” effect of press attention
Professor XXXXXX:…Oceanographer at MIT
Even within the scientific community you see, it’s a problem.
If I run a complicated model and I do something to it like melt a lot of ice into the ocean and nothing happens, it’s not likely to get printed.
But if I run the same model, and I adjust it in such a way that something dramatic happens to the ocean circulation like the heat transport turns off, it will be published. People will say this is very exciting. It will even get picked by the media.
So there is a bias, there’s is a very powerful bias within the media, and within the science community itself, toward results which are dramatizable.
If Earth freezes over, that’s a much more interesting story than saying well you know it fluctuates around, sometimes the mass flux goes up by 10%, sometimes it goes down by 20%, but eventually it comes back. Well you know, which would you do a story on? That’s what it’s about.
Chill Bill. Only poor brown people will pay.
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This conversation felt familiar.
I believe I have seen this list of failed climate predictions before, looked up some of the articles and commented on them before.
In spite of the mode of expression of reporters - rather than scientists - Feynman was right. His dichotomy doesn’t capture the problems related reporting on science in the popular press, though. These articles are too many degrees removed from any actual science they refer to.
They are not relevant to the discussion, either.
Or my post: Surely you’re joking, Mr. Wbwane:
Excuse me for my feynmemian doubt. If this is how you see the situation, I certainly can’t help you see it differently.
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I need to point out what just happened here:
I provided:
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Specific scientific evidence with citations from NASA, NOAA, peer-reviewed studies
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Explanations of why the CO2 Coalition and John Christy graphs are misleading
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Data showing global temperatures are the warmest on record
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The stratospheric cooling fingerprint that proves CO2 is the driver
You responded with:
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Conspiracy theories about a “Climate Alarm Industrial Complex HOAX”
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Claims that credentialed skeptics are being “de-platformed” and “censored”
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The Galileo persecution narrative
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A bizarre tangent about churches, air conditioning, Russian serfs, and chimney taxes
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Political slogans: “drill, drill, drill”
This isn’t someone engaging with evidence. This is someone who’s decided it’s all a conspiracy and is working backwards to defend that belief.
But since you brought up specific people and claims, here are the facts:
On the “discredited hockey stick”: It’s not discredited. Multiple independent reconstructions using completely different methods and datasets (including the PAGES 2K project with 78 researchers from 24 countries) show the same pattern: relatively stable temperatures for ~1800 years, then sharp modern warming. The basic finding has been replicated over and over.
On Lindzen, Christy, Happer, Koonin, Clauser: These are real scientists with real credentials, but they represent a tiny minority view, and their specific climate claims have been extensively critiqued in peer-reviewed literature. Having credentials doesn’t make you immune to being wrong. Linus Pauling won two Nobel Prizes, then spent his final decades promoting vitamin C megadoses as a cancer cure - he was wrong about that, despite his brilliance in chemistry. Being accomplished in one area doesn’t make you right about everything.
On “de-platforming” and journal censorship: Skeptic papers get published regularly. They often have methodological problems that get critiqued by other scientists - that’s not suppression, that’s peer review. Science isn’t a democracy where all opinions are equal; it’s a process where claims must be supported by evidence and survive scrutiny. Climate skeptic papers are scrutinized heavily, and many don’t hold up. That’s the system working. Here’s a great example of the peer-review process in action from 2015:
The Galileo gambit: Invoking Galileo doesn’t make you right. There’s an entire fallacy named after this rhetoritcal technique. Yes, Galileo was persecuted and correct. But for every Galileo, there are 10,000 people who were also rejected and were actually wrong. Being dismissed by mainstream science doesn’t automatically make you the misunderstood genius - usually it means your evidence isn’t convincing.
Here’s the bottom line:
I’ve provided specific scientific evidence multiple times - data, physics, peer-reviewed research, explanations of why those specific graphs mislead. You’ve responded with conspiracy theories, persecution narratives, and political slogans.
If you’re genuinely interested in understanding the evidence - why the stratosphere is cooling while the troposphere warms, why that’s the unique fingerprint of greenhouse gas forcing, why climate models match dozens of independent metrics - it’s all there in what I’ve shared.
But if you’ve already decided it’s a hoax and that everyone from NASA to NOAA to thousands of independent researchers across dozens of countries are all part of some vast conspiracy, then no amount of evidence will matter. At that point you’re not evaluating data - you’re defending a conclusion you’ve already reached for other reasons.
I’m going to bow out here. The science is solid, the evidence is overwhelming, and I’ve laid it out clearly. What you do with that information is up to you.
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Absolutely first class Matthew. BioLogos at its best. Unspun, disinterested, warranted, justified, true, intellectually honest, belief, aka knowledge.
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@Kendel the thread is back from the magic space of deleted threads 
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Sir! Kendel and I aren’t one and the same!
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Climate Policies Harm the World’s Poor
Guest Post by Vijay Jayaraj
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I’m often asked what motivates my work on climate and energy. The answer is simple: I grew up in India, a developing country where electricity blackouts were normal, where families cooked with kerosene, and where factories shut down because of fuel shortages. Those early experiences shaped my conviction that reliable, affordable energy is the foundation of human progress.
Today, as part of the CO₂ Coalition, I write about how misguided climate policies—often shaped in the halls of wealthy Western capitals—are deepening poverty in the Global South. My academic journey took me from an engineering degree in India to environmental and energy studies in the United Kingdom. That background taught me that science is often twisted by ideology. The global climate debate became detached from reality, ignoring the billions who still live without secure access to electricity.
Carbon dioxide is not the villain it’s made out to be. It is a life-giving molecule, the very foundation of photosynthesis, agriculture and ecosystem health. Modern prosperity—from hospitals to schools to clean drinking water—depends on energy and, for now, that energy overwhelmingly comes from hydrocarbons. Denying that truth does nothing beneficial for the environment; it simply prolongs suffering for the world’s poor and makes everybody’s energy more expensive.
My writing aims to restore balance and sanity to this conversation. Here are a few of my recent pieces that speak to this mission.
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1. The Media’s Green Deception Hurts the Poor
In “Media’s ‘Green’ Pandering Lures Developing World into Disaster” (CO₂ Coalition, March 2025), I explore how global media campaigns pressure poorer nations to abandon fossil fuels—even when renewables cannot sustain their economies. Energy poverty is not just a statistic; it’s the difference between life and death for millions who rely on diesel generators, coal plants, and gas grids. When journalists cheer for “net zero,” they ignore the child studying under candlelight and the mother walking miles for cooking fuel.
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