The Human Destructive Madness is Harming Everybody and Everything on Earth
In this moment of total madness, when humankind seems to have lost all reference points and even its very humanity, we must not forget that all human beings of this planet are victims of our destructive folly, just as all of its living creatures. This week, I am at the World Conference on Science and Art for Sustainability in Belgrade, Serbia, to present the results of the recent work by myself and my coworkers on the biochemical damage created by increasing CO2 concentrations in the atmosphere. A few days ago, I published a second, more in-depth paper on this subject on Qeios. Here, I am posting an excellent summary of our results by Eduardo Martinez de la Fe.
In this article on El Periódico de España, Eduardo Martinez de la Fe comments on the recent paper published by myself and my colleagues on the negative effects of CO2 on human health. -- Ugo Bardi
We Are Inhaling Stupidity: The Carbon Dioxide Threat to Our Brain
Madrid, September 10, 2025, 8:07 a.m. Updated SEPT 10, 2025 9:50
The increase of CO2 in the atmosphere not only heats up the planet, but it affects our blood, neurons, and ability to make decisions
By exceeding 420 parts per million of CO₂ in the atmosphere, we have crossed an unprecedented threshold for our species, forcing our biology to operate in a chemical environment for which it is not designed. This planetary experiment is already showing its effects, and the price could be our own mental acuity.
When we think of carbon dioxide (CO₂), the first image that usually comes to mind is global warming. We have come to see it as the main culprit behind climate change, a gas that traps heat and alters the planet's temperature. However, a critical analysis published in the journal Environmental Science Advances by a team of scientists led by Italian chemist Ugo Bardi forces us to broaden our view and consider CO₂ in a new light: that of a biochemical pollutant with direct and worrying effects on our health and the biosphere.
The central thesis of the study is that, while the greenhouse effect of CO₂ is a problem of enormous magnitude, focusing solely on it causes us to ignore its other facets. CO₂ is a chemically active molecule that, as its concentration in the atmosphere increases, triggers a series of consequences that go far beyond the climate.
Direct impact on our body and brain
Perhaps the most alarming warning in the report focuses on human health. Our bodies have evolved over millions of years in an atmosphere with CO₂ levels that rarely exceeded 300 parts per million (ppm). Today, we exceed 420 ppm, and the figure continues to rise. This alteration, unprecedented in the history of our species, interferes with a fundamental biological process: breathing.
The mechanism is subtle but powerful. The transport of oxygen in our blood, carried out by hemoglobin, is finely regulated by the concentration of CO₂. When CO₂ levels in the blood rise, hemoglobin's ability to bind oxygen and distribute it to tissues is compromised. This phenomenon, known as hypercapnia, has direct consequences.
Recent studies have shown that exposure to CO₂ concentrations between 1,000 and 2,000 ppm, levels that are easily reached in enclosed spaces such as offices, classrooms, or even in our poorly ventilated homes, causes a measurable decrease in cognitive performance. People exposed to these levels show a reduced ability to make decisions, solve problems, and think strategically. It essentially slows down our brain.
But the effects don't end there. Chronic exposure to high levels of CO₂ can cause acidosis and physiological stress: this occurs when the body tries to compensate for the increase in blood acidity (caused by dissolved CO₂) by mobilizing calcium from the bones, which in the long term can lead to calcification of the kidneys and arteries.
Increased inflammation, oxidative stress, and changes in heart rate and blood pressure have also been observed, even at moderate levels. Furthermore, studies in animals exposed to CO₂ concentrations predicted for the near future show problems with lung and muscle development, hyperactivity, and reduced attention, the researchers warn.
An evolutionary disconnect
The report raises a disturbing question: Are our large, complex brains adapted to function in the world we are creating? The evolution of hominids and the development of a brain with high neuronal density occurred during the Pleistocene, a time with very low CO₂ levels (between 180 and 280 ppm). We are forcing our biology, designed for a low-CO₂ environment, to operate in radically different conditions.
The authors suggest that this “evolutionary disconnect” could be related to recently observed trends, such as the “reverse Flynn effect” (a global decline in IQ scores) or the increase in the incidence of senile dementia, phenomena that until now were attributed to generic environmental factors.
Reference: Carbon dioxide as a pollutant: the risks on human health and the stability of the biosphere. Ugo Bardi et al. Environmental Science Advances, 2025, 4, 1364-1372. DOI:10.1039/D5VA00017C
The myth of “food for plants”
The report also addresses the argument that an increase in CO₂ is beneficial because it acts as a ‘fertilizer’ for plants. While it is true that higher concentrations can accelerate photosynthesis in some trees and plants (a phenomenon known as “global greening”), the study strongly qualifies this idea.
It clarifies that this fertilizing effect does not apply to vital crops such as corn, sugarcane, or millet (C4 plants), which have a different photosynthesis mechanism. It also points out that the increase in biomass due to CO₂ does not translate into higher nutritional content. Plants grow faster, but with fewer vitamins and minerals.
Finally, the report indicates that plants adapted to higher CO₂ reduce their transpiration, which can alter rainfall patterns and increase the risk of flooding by changing the functioning of the “biotic pump” that transports atmospheric moisture. Conclusion: the small agricultural benefits, if any, do not come close to offsetting the damage to human health and ecosystems from increased CO₂ emissions.
A redefined call to action
The report's conclusion is clear: treating the CO₂ crisis solely as a temperature problem is a dangerous mistake. Geoengineering solutions such as Solar Radiation Management (SRM), which propose cooling the planet by reflecting sunlight, would do nothing to curb the biochemical pollution of CO₂. We might live on a cooler planet, but with air that continues to negatively affect our cognitive abilities and health.
The only real solution, according to the authors, is to drastically reduce emissions and, in the long term, find ways to return atmospheric CO₂ concentrations to levels compatible with our biology.
We need to start seeing carbon dioxide not just as a gas that warms the planet, but as what it really is: a pollutant that, at current levels, is already compromising the health of the biosphere and our own.
