Increased CO2 Levels Negatively Affect Our Brains

Something that isn't often discussed is the non-greenhouse impacts of increasing atmospheric CO2. One of those is that increased CO2 levels affect human cognition, so I've summarized some of the research here.

Increasing CO2 levels worsens human decision making

Two studies directly tested cognitive function vs CO2 level, and both found that performance drops as CO2 levels increase. They both tested many different aspects of cognition, and the results are best summarized in the two images below:

The first one has a legend that documents the CO2 levels. The second one uses aliases for them, so to translate, conventional is ~950 ppm, green is ~750 ppm, and green+ is ~550 ppm. To summarize the results in text:
  • increasing CO2 levels led to worse performance in 7 of the 9 tasks tested in the first study
  • the average drop in performance is ~20% for a 400 ppm increase in CO2 in the second study

Increasing CO2 levels lowers sleep quality

CO2 levels for students in a dorm were set at either ~600 ppm or ~2500 ppm throughout the night. Sleep quality was measured by wrist monitors, reported sleepiness, and ability to concentrate. The lower CO2 levels led to improved sleep quality according to those metrics.

Increased CO2 levels in classrooms are associated with more student absences

A 1000 ppm increase in CO2 levels was associated with a 10-20% increase in absences in 434 classrooms in 22 schools.

Increased CO2 levels in the space station are associated with more astronaut headaches

A 1300 ppm increase in CO2 levels was associated with a doubling of the chance that an astronaut reported a headache.

Increased cockpit CO2 levels lower pilot performance

30 pilots were tested at 700, 1500, and 2500 ppm, and their performance declined with increasing CO2 concentrations.

Why does this matter?

CO2 levels have been in the 150-300 ppm range for basically all of human history and definitely all of modern history:

In the past couple hundred years, we have pumped huge amounts of carbon into the atmosphere and raised these levels. We are continuing to do so. We are currently over 400 ppm and are raising the level by ~2 ppm per year. The rate at which we raise it is increasing:

Since indoor levels are higher than outdoor levels, we are raising the minimum CO2 level in the air we breathe, and the sources above paint a clear picture of how negative that is for us.

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