Skip to content

What Will Rising Carbon Dioxide Levels Do To Our Brains and Thinking Abilities?

Notice that the carbon dioxide levels in the air keep rising and rising? Along with the world getting hotter, the carbon dioxide levels are rising, and last year it hit 414.7 parts per million (ppm). This is the highest it has been in at least 800,000 years, and maybe for millions of years! (It's from the burning of fossil fuels.) Soo... the big question is: What will increasingly higher CO2 levels mean for our brains - for our thinking and cognition?

Ever notice that in rooms filled with people, that the air gets stuffier over time? Well, that's the effect of carbon dioxide - as the carbon dioxide levels rise (from us simply exhaling), the air in the room feels stuffier. It can already feel stuffy at 600 ppm. Rooms with people in them (classrooms, office meetings, etc) easily hit over 1000 ppm of carbon dioxide.

Studies suggest that at certain levels of carbon dioxide our thinking gets worse. While study results vary, there does seem to be agreement that "mental processes in the domain of decision making and planning appear to be robustly affected".  And yes, a growing number of studies do find pretty scary results.

For example, one 2016 study that looked at indoor air in office buildings found that: " of nine cognitive function domains tested in a strategic management simulation decreased as CO2 increased. Employee scores were 15 percent lower in a day spent working at 945 ppm, and 50 percent lower at 1,400 ppm." It means that the people weren't thinking all that well as the CO2 levels rose in the air they were breathing.

Research looking at carbon dioxide effects have generally studied the problem as an "indoor pollutant" and used the outdoor air as a comparison. But what happens when the outdoor air of the future is the "high CO2" level studied today?

Some physical effects of rising carbon dioxide exposure in humans: increased CO2 in the lungs, in the blood, and in the brain (which is associated with reduced oxygen and brain activity), increased sleepiness and anxiety (both of which harm cognitive function), and acidosis (lowered blood pH - which leads to symptoms such as restlessness and a rise in blood pressure). One study in juvenile rats found "reduced levels of neuroprotective growth factor", which harmed brain development and impaired learning and memory.

What about babies and children? Developing fetuses? The elderly? The sick?  All unknown. Also, studies looking at effects are short term, but our future (if not changed) will have us exposed to higher and higher levels of CO2 all the time.

Keep in mind that as outdoor carbon dioxide levels rise, indoor levels will also rise.  Think about it - opening a window to let in some fresh air will only give you the CO2 levels in the outside air. If that is high and feels stuffy, that's what you'll get. All the time. Why isn't everyone discussing this issue? 

Excerpts from Robinson Meyer's article at The Atlantic: The Human Brain Evolved When Carbon Dioxide Was Lower  

SAN FRANCISCO—Kris Karnauskas, a professor of ocean sciences at the University of Colorado, has started walking around campus with a pocket-size carbon-dioxide detector. He’s not doing it to measure the amount of carbon pollution in the atmosphere. He’s interested in the amount of CO₂ in each room.

“I did this at home, just having fun with it, and in a bedroom overnight it can get over 1,000 parts per million very quickly,” he told me. Even here, he added—gesturing at the city-block-size basement of the Moscone Convention Center, filled with thousands of earth scientists milling about their discipline’s giant annual science fair—the CO₂ probably exceeds 500 parts per million.

The indoor concentration of carbon dioxide concerns him—and not only for the usual reason. Karnauskas is worried that indoor CO₂ levels are getting so high that they are starting to impair human cognition. In other words: Carbon dioxide, the same odorless and invisible gas that causes global warming, may be making us dumber.

He proposed the idea last week at the American Geophysical Union’s fall meeting, the largest annual gathering of earth and space scientists in the world. He also previewed it in an online paper written with Shelly Miller, a mechanical-engineering professor at the University of Colorado, and Anna Schapiro, a neuroscience professor at the University of Pennsylvania. 

The science is, at first glance, surprisingly fundamental. Researchers have long believed that carbon dioxide harms the brain at very high concentrations. Anyone who’s seen the film Apollo 13 (or knows the real-life story behind it) may remember a moment when the mission’s three astronauts watch a gauge monitoring their cabin start to report dangerous levels of a gas. That gauge was measuring carbon dioxide. As one of the film’s NASA engineers remarks, if CO₂ levels rise too high, “you get impaired judgement, blackouts, the beginning of brain asphyxia.

“They knew they’re going to go nuts and not do 2+2 if that gauge gets too high,” Karnauskas said. The same general principle, he argues, could soon affect people here on Earth. Two centuries of rampant fossil-fuel use have already spiked the amount of CO₂ in the atmosphere from about 280 parts per million before the Industrial Revolution to about 410 parts per million today. For Earth as a whole, that pollution traps heat in the atmosphere and causes climate change. But more locally, it also sets a baseline for indoor levels of carbon dioxide: You cannot ventilate a room’s carbon-dioxide levels below the global average.

In fact, many rooms have a much higher CO₂ level than the atmosphere, since ventilation systems don’t work perfectly. On top of that, some rooms—in places such as offices, hospitals, and schools—are filled with many breathing people, that is, many people who are themselves exhaling carbon dioxide. As Karnauskas said: “We’re little CO₂-producing machines ourselves.” “Imagine a conference room,” he said. “You have middle-aged people—20 of them—sitting in a small room, breathing. That CO₂ easily exceeds 1,000 parts per million.”

And that leads to the final part of his and his colleagues’ argument: As the amount of atmospheric CO₂ keeps rising, indoor CO₂ will climb as well. They project that, in a worst-case emissions scenario, it may be impossible to ventilate a crowded room below about 1,300 parts per million. That could induce some real cognitive damage. In 2016, researchers at Harvard and Syracuse University found that human cognitive function declined by about 15 percent when indoor CO₂ reached 945 parts per million, and crashed by 50 percent when indoor CO₂ reached 1,400 parts per million.

Under a very high carbon-emissions scenario, “our complex decision-making functions could be reduced by as much as half by the end of the century,” Karnauskas said.

He and his colleagues admit that their calculations are back of the envelope. “There’s got to be a lot more work on this,” he told me. And I had to wonder: Is this for real? Why hadn’t I heard about it before? Is carbon pollution not only heating the planet but actually making us more sluggish thinkers?

In September, some of the issue’s leading scientists—including those from the Denmark lab mentioned above—reviewed all 10 studies on the topic since 2012. On moderate tests of cognition, they found, the evidence was very ambiguous: Sometimes higher CO₂ seemed to decrease ability, sometimes it didn’t at all. But more worryingly, they noted “substantial, but still inconsistent, evidence” that human performance can decline on especially challenging problems at moderate concentrations. Pilot performance on flight simulators, for instance, starts to fall at 1,200 parts per million. “The mechanisms underlying the reductions in performance are unknown,” they added.

In other words: There’s evidence that carbon-dioxide levels may impair only the most complex and challenging human cognitive tasks. And we still don’t know why.

In their September review, the authors noted that many aspects of the problem remain unexplored. For instance, does CO₂ make the effects of other brain-impairing pollutants worse? It’s unclear. No one has looked at the effects of indoor CO₂ on children, the elderly, or people with health problems. Likewise, studies have so far exposed people to very high carbon levels for only a few hours, leaving open the question of what days-long exposure could do.

Perhaps the most intriguing omission of the research is also the most ominous. Modern humans, as a species, are only about 300,000 years old, and the ambient CO₂ that we encountered for most of our evolutionary life—from the first breath of infants to the last rattle of a dying elder—was much lower than the ambient CO₂ today. I asked Gall: Has anyone looked to see if human cognition improves under lower carbon-dioxide levels? If you tested someone in a room that had only 250 parts per million of carbon dioxide—a level much closer to that of Earth’s atmosphere three centuries or three millennia ago—would their performance on tests improve? In other words, is it possible that human cognitive ability has already declined? Gall said he wasn’t aware of such an experiment.

But of course, a large-scale experiment is under way—it’s just not happening under clinical conditions. You and I are its subjects, and the CO₂ in the chamber rises with every passing year. Clock your baseline cognition now: In another 20 years, you might miss these clearheaded times.

Leave a Reply

Your email address will not be published. Required fields are marked *