CO2: Giver of Life -- Giver of Death

Not Just Global Warming, not Just Food For Plants: CO2 is the keystone of the ecosystem. And today there is too much of it.

The Goddess Gaia studies the chemistry of CO2 in her forest. It is not an easy subject: CO2 regulates the metabolism of the Earth’s ecosystem in many ways. Too much of it, just as too little, can kill. And, right now, we are pushing the CO2 concentration beyond values that were never experienced by the biosphere during the past 15 million years. It is a vital subject for our survival, as reviewed in a recent paper on CO2 as a pollutant,

So far, the increase in CO2 concentrations in the atmosphere has been considered a problem only in terms of its greenhouse effect, a cause of global warming. But CO2 is not just a greenhouse gas. It is a chemically active molecule that plays several crucial roles in the metabolism of living beings. Once you start looking into this matter, you discover a whole world. Carbon dioxide is at the same time food and waste; it is a catalyst, it is a regulator, it changes the blood’s pH, affects the calcification of bones, blood circulation, and much more.

The CO2 perturbation is known in sectors such as ocean acidification, and the increase of vegetative rates for some plants — called “global greening.” (*) But much less is known, and even less perceived, about the metabolic effects on humans and other mammals. So, we (Ugo Bardi, Phil Bierwirth, Kuo-Wei Huang, and John McIntyre) decided to plunge into the matter and create a comprehensive review on the subject. Our paper on CO2 was published last week on “Environmental Science Advances”, a journal of the Royal Society of Chemistry. We found that the current concentration of 425 ppm is not far from levels that can negatively affect people’s health, and we breathe much larger concentrations indoors. In addition, we keep it increasing by about 3 ppm every year. What are we doing?

It is a long and complex story, but also a fascinating one. The history of life on Earth has been determined in large part by the balance of oxygen and carbon dioxide in the atmosphere. There was a time, more than two billion years ago, when there was no oxygen in the atmosphere, and life was limited to simple, unicellular creatures. Then, slowly, oxygen generated by photosynthesis accumulated in the atmosphere, while CO2 went down. That made it possible for living creatures to use oxygen to power up their metabolic processes. When the oxygen concentration reached values similar to the current ones, around 20%, some 300-400 million years ago, life could bootstrap itself to multicellular creatures, large animals that occupied the seas and the continental lands. Eventually, Earth saw the great encephalization burst of the past few million years, which included those big-brained creatures we call “homo sapiens.”

Without oxygen, human beings cannot survive for more than a few minutes, but what kills people confined in sealed environments is not the lack of oxygen, but the poisoning effects of CO2. It is called “hypercapnia,” from a Greek word that means “smoke.” For short periods, nothing happens even for CO2 concentrations ten times larger than the atmospheric ones, but going higher starts being risky. 5% of CO2 may not seem so much, but it is deadly.

Of course, most of us are not miners or submariners, so we are not at the risk of acute hypercapnia. Yet, we are continuously exposed to concentrations much higher than those at which our ancestors evolved and, reasonably, were optimized for. A body of knowledge has accumulated on this subject as the result of experimental tests. The data are still scattered and often in need of verification. But the overall conclusion is clear: negative effects on human mental abilities are seen already at CO2 concentrations commonly experienced indoors today. And the higher the atmospheric concentration becomes, the higher the indoor concentrations will be.

The negative health effects of excess CO2 can be reversed by exposing the affected people to fresh air. The problem is that the increase of CO2 in the atmosphere is irreversible, at least for now. Nobody was ever exposed to these concentrations for their whole life, but future generations of humans will be. And nobody knows for sure what the effects on our health and our very survival could be. It is a gigantic experiment carried out on our bodies.

Our work is not meant to scare anyone, but problems do not go away because you ignore them. We need to take these data into account, and that’s all the more important today when the media is flooded with a propaganda campaign designed to present CO2 as a harmless molecule, unjustly maligned by ideologically bent scientists. CO2 is described as “food for plants” and hence the cause of global greening, beneficial to everything and everyone. We have an entire think tank called “The CO2 Coalition,” very active and apparently well-financed, dedicated to disseminating this concept. But making some plants grow faster doesn’t justify the damage on human beings and on the overall ecosystem. Hardly anything qualifies better in terms of “playing with fire” than this truly reckless attitude. (**)

So far, the public, just as most scientists, has missed the metabolic problems caused by CO2. But the results shown in our paper tell us that global warming is not the only problem we are facing; we are seeing a global perturbation of the whole ecosystem generated by the chemical activity of carbon dioxide. For our survival, it is vital to stop the growth of CO2 in the atmosphere, and, in the future, bring it back to values close to those for which our bodies and brains evolved. It is a huge task we are facing, but the first step to solving a problem is to understand that it exists.

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(*) For those who think that the “food for plants” concept justifies harming human beings, note that:

1. Manure is food for plants, too. But it is no good as food for us.

2. Global greening exists, but it is not evident that it is caused by CO2 alone. Other contributors include warmer temperatures, nitrogen deposition, and land-use changes like reforestation or agricultural expansion.

3. Only some plants benefit from higher CO2 concentrations, those which use the “C3” photosynthetic mechanism. Mainly trees, but not grasses and many cereals use the alternative “C4” mechanism, scarcely affected by higher CO2 concentrations.

4. There is no evidence that the enhanced growth rate of some agricultural plants increases their nutritional contents.

5. The effect on photosynthesis becomes less pronounced and tapers out as CO2 concentrations increase.

6. These concepts are discussed more in detail in our paper.

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(**) To illustrate how the meme “CO2 is food for Plants, and hence harmless” is growing, here is a list prepared by Grok of recent books on the subject. These are mostly niche books, written by known climate contrarians. But their presence shows that the meme is raising its ugly head.

• English

  • The Greening of the Earth (2016) - Matt Ridley

  • Inconvenient Facts: The Science That Al Gore Doesn't Want You to Know (2017) - Gregory Wrightstone

  • CO2: A Gift from the Heavens (2019) - Dennis T. Avery and S. Fred Singer

  • The Great CO2 Hoax: Why Carbon Dioxide Is Good for the Planet (2023) - Patrick Moore

• German

  • CO2: Der Stoff, aus dem das Leben ist (2021) - Fritz Vahrenholt and Sebastian Lüning

  • Grün ist die Hoffnung: Wie CO2 die Welt ernährt (2022) - Hans-Jörg Müllen

• French

  • CO2 : Un bienfait pour la planète (2021) - Christian Gérondeau

  • La vérité sur le CO2 : Mythes et réalités climatiques (2023) - François Gervais

• Italian

  • CO2: Il nutrimento delle piante (2022) - Alberto Prestininzi

  • Clima: La bufala del riscaldamento globale (2023) - Mario Pagliaro

• Spanish

  • CO2: El alimento de las plantas (2021) - Javier Peña-Dávila

  • El mito del cambio climático: La verdad sobre el CO2 (2022) - Antonio Ruiz de Elvira

  • Verde por el CO2: Beneficios del dióxido de carbono (2023) - María Isabel Moreno

• Chinese

  • 二氧化碳：植物的粮食 (2021) - 李明哲 (Li Mingzhe)
    (Translation: Carbon Dioxide: Food for Plants)

  • 气候神话：揭秘CO2的真相 (2022) - 王志强 (Wang Zhiqiang)
    (Translation: Climate Myths: Unveiling the Truth About CO2)

• Russian

  • Углекислый газ: Польза для растений (2022) - Алексей Иванов (Aleksey Ivanov)
    (Translation: Carbon Dioxide: Benefits for Plants)

  • Климатический обман: CO2 и реальность (2023) - Сергей Петров (Sergey Petrov)
    (Translation: Climate Deception: CO2 and Reality)

• Japanese

  • CO2：植物の栄養 (2021) - 田中健一 (Kenichi Tanaka)
    (Translation: CO2: Plant Nutrition)

  • 気候変動の誤解：CO2の真実 (2023) - 山本直樹 (Naoki Yamamoto)
    (Translation: Climate Change Misconceptions: The Truth About CO2)

• Portuguese

  • CO2: Alimento para Plantas (2022) - João Carlos Almeida

  • O Mito do Aquecimento Global: CO2 e Agricultura (2023) - Mariana Costa

• Dutch

  • CO2: Voedsel voor Planten (2021) - Pieter van der Meer

  • Klimaatmythes: De Waarheid over CO2 (2022) - Hans de Vries

Of course, there is a corresponding group of books expressing opposite views; here is a list of those in English only.

• The New Climate War: The Fight to Take Back Our Planet (2021) - Michael E. Mann

• Under a White Sky: The Nature of the Future (2021) - Elizabeth Kolbert

• The Future We Choose: Surviving the Climate Crisis (2020) - Christiana Figueres and Tom Rivett-Carnac

• Saving Us: A Climate Scientist’s Case for Hope and Healing in a Divided World (2021) - Katharine Hayhoe

But the very existence of a growing list of books expressing that high CO2 concentrations are a good thing is a worrisome indication that something is stirring in the memesphere. We cannot exclude a successful outcome for the efforts to basculate the CO2 narrative into the exact opposite of what it was up to now.

Acknowledgement: The authors thank the Club of Rome and by the National Consortium of Science and Technology of Materials (INSTM) for their support for the publication of the paper cited in this post.