I’ve been at this climate communication game for a while now, and I’ve heard just about every bad argument the climate science deniers have come up with. There are all sorts, with varying degrees of sophistication, but perhaps the most absurd is the bold assertion that CO2 is not a poison gas. It’s generally paired with the reminder that plants need CO2 to live, and some derision of the notion that rising atmospheric CO2 levels would kill us all. Which has never been the claim.
The “rising CO2 will kill us all” line comes from the disastrous effects of a destabilized climate that we’re now seeing on a yearly basis. The jury’s still out on whether it will kill us all, but it certainly has the potential to destroy civilization as we know it, and our species’ survival is not guaranteed. We have no mystical destiny to reach the stars or anything like that, and rapid global warming is a known recipe for extinction. Nobody was claiming that it would kill us all by poisoning us!
In other news, the rise in atmospheric CO2 is poisoning us.
Rising carbon dioxide levels are being detected within the human body, with new research warning a key blood marker for the gas could near its healthy limit within decades if current trends continue. The findings are especially relevant for children and adolescents, whose developing bodies will experience the longest cumulative exposure to rising atmospheric CO₂.
In a study published in Air Quality, Atmosphere and Health, researchers from The Kids Research Institute Australia, Curtin University and The Australian National University (ANU) analysed more than two decades of U.S. population data and found steady shifts in blood chemistry that closely track the rise in atmospheric CO₂.
Using data from the U.S. National Health and Nutrition Examination Survey (NHANES), the team examined blood results from around 7,000 people every two years between 1999 and 2020.
Average levels of serum bicarbonate – a marker closely linked to carbon dioxide in the body – have risen by approximately seven per cent since 1999. Over the same period, average calcium and phosphorus levels have declined.
These changes mirror the rise in atmospheric CO₂, which has increased from about 369 parts per million (ppm) in 2000 to more than 420 ppm today.
Author Associate Professor Alexander Larcombe said the findings suggest the human body may already be compensating for a changing atmosphere.
“What we’re seeing is a gradual shift in blood chemistry that mirrors the rise in atmospheric carbon dioxide which is driving climate change,” A/Prof Larcombe said.
I have to admit I didn’t see this one coming, but now that I think it through, I should have. This may be one of those times when the rhetoric of my opponents successfully guided me away from actually considering an angle of the whole thing. Our bodies use chemical reactions to take what we need from our air, water, and food, and get rid of the rest. CO2 is no exception.
And that change in blood chemistry is not without consequences. The associated decline in calcium and phosphorus may not be a big issue now, but these findings present us with a future in which much of humanity will need to be on supplements to counteract the fact that we have literally been poisoning our atmosphere (in a different way from all the other ways we’ve been poisoning our atmosphere).
Bicarbonate plays a central role in maintaining the body’s acid–base balance. When CO₂ levels rise, the body retains more bicarbonate to stabilise blood pH. Over time, however, sustained compensation may carry physiological consequences.
“If current trends continue, modelling indicates average bicarbonate levels could approach the upper limit of today’s accepted healthy range within 50 years,” A/Prof Larcombe said
“Calcium and phosphorus levels could also reach the lower end of their healthy ranges later this century.”
Humans evolved in an atmosphere containing roughly 280–300 ppm of CO₂. The average annual increase over the past decade has been about 2.6 ppm per year, with 2024 recording a 3.5 ppm rise.
Fellow Author Dr Phil Bierwirth, a retired environmental geoscientist who is affiliated with the ANU Emeritus Faculty, said while the study does not prove direct causation, the consistent, population-wide trends are difficult to ignore.
“I actually think that what we are seeing is because our bodies are not adapting,” Dr Bierwirth said.
“It appears we are adapted to a range of CO2 in the air that may now have been surpassed.
“The normal range maintains a delicate balance between how much CO2 is in the air, our blood pH, our breathing rate and bicarbonate levels in the blood.
“As CO2 in the air is now higher than humans have ever experienced, it appears to be building up in our bodies. Maybe we can never adapt such that it is vitally important to limit atmospheric levels of CO2.”
Honestly, it’s getting hard to keep track of all the ways in which we’re poisoning ourselves. That makes it all the more ridiculous when people insist that things like a rise in chronic health problems, or a decline in fertility are solely a matter of personal lifestyle choices like diet. That’s not to say diet isn’t important, but a healthy diet won’t negate the effects of a planetary atmosphere for which we are simply not evolved. Dinosaurs lived with higher CO2 levels than this, but it turns out dinosaurs are not humans, and they had evolved to thrive in that atmosphere.
We need to start thinking about this as if we’re all on an alien planet. If we don’t terraform it to conditions conducive to human life, we’ll have to take medication to counteract the poisons in the air we breathe, or live in sealed environments with limited exposure to unprocessed air. That may sound dramatic for something that can be treated with dietary supplements, but it’s even easier to treat hunger, and we’ve decided instead to use it as a weapon to control or eliminate people.
People used to joke about rich people controlling access to breathable air, but now? Now I’m thinking of a Stargate SG-1 episode in which a nation of Nazi aliens tried to genocide everyone else by poisoning the entire planet’s atmosphere from within a sealed bunker.
A long time ago, I urged people to think about global warming in terms of science fiction, because dealing with it will require such a revolutionary change in our society that it opens up all sorts of possibilities for a new kind of existence. That remains true.
The old world is collapsing, and nothing can save it. If we try to cling on to the past, we’ll be buried under its rubble.
The only hope our species has for a real future is to let go of what we know, and build something new.
I mean, it’s sort of obvious that this could happen. Although…atmospheric CO2 went up 12% between 1999 and 2020, but serum bicarbonate only increased by 7%. So there must be more to the story. If I remember my physiology, diffusion of gases in the alveoli works because oxygen concentration in the atmosphere is higher than oxygen concentration in the blood, so it moves INTO the blood, while carbon dioxide concentration in the blood is higher than carbon dioxide concentration in the atmosphere, so it moves OUT of the blood. Thus, the increased partial pressure of CO2 in the air itself must be making the process less efficient, resulting in more of the CO2 produced in cellular respiration staying in the body, acidifying the blood and requiring the production of bicarbonate by the buffering system therein.
Is this a problem that is as consequential as the other serious issues climate change is causing? I seriously doubt it. But it’s worth keeping in mind. And I would be VERY interested to see how other mammals, as well as birds, reptiles, fish and insects (particularly insects) have responded to the increased atmospheric CO2. Because you would think that some animals would be better equipped to deal with these changes than others, but also that this signal SHOULD be visible in ALL living beings. I’m curious to see which ones are showing the most dramatic changes. Now that I think about it though, the answer is probably the anthozoan cnidarians (the animals that make up CORALS), but that’s because they both mineralize calcium carbonates, and lack a circulatory system – seawater IS THEIR BLOOD, and so they cannot buffer against pH changes the way we can (corals are small, in comparison to the entirety of the planet’s oceans). I wonder if there are other such “canaries in the coal mine,” uniquely badly-adapted to living with high carbon dioxide levels in the atmosphere.
Yeah, I feel like I should have known, I just never thought about it. It’s an example of how literally everything on the surface of the planet is changing, to the point where it’s impossible to keep track of all of it.It’s also a case of yes, this could have been(and probably was) predicted, but it’s another matter entirely to actually measure it.
Going back to whether it is directly a “poison”, if it wasn’t, why did Apollo 13 have to make scrubbers? It’s not like they were short of oxygen; it was an excess of CO2.
Going back to the argument that “CO2 is not a poison because plants use it to grow!”, one could say the same thing about urine and feces. Plants extract useful nutrients from them that they need to grow. That doesn’t make them any less toxic to animals, though.