Thank you for linking some studies! This is very interesting to me, since I have noticed CO2 levels having a major effect on my work routine.

There is a CO2 sensor on my desk for 10 years already. Generally it is around 650 ppm during a working day but occasionally the building's ventilation system's power trips and air movement suddenly decreases. This causes CO2 levels to rise fast - once they hit 900-1000 ppm, I can definitely feel a decrease in my ability to focus and think clearly (and yes, I feel it even before looking at the numbers, ha!).

Obviously silly single anecdote but subjectively the link is very strong for me!

PS. On a sad note is that I remember the days when coming to work in the morning meant the CO2 level was at 350 ppm. These days clean air is 450 ppm in this city!