It would be interesting if the study could be duplicated. More importantly it does not seem to distinguish between the acute effect of a sudden increase in CO2

It would be interesting if the study could be duplicated. More importantly it does not seem to distinguish between the acute effect of a sudden increase in CO2 in an experimental setting and the chronic effect of gradually rising ambient rates over the span of years. It stands to reason that the body would adapt to higher CO2 levels over longer time ranges vs. just injecting a sudden pulse of 2500 ppm into a closed chamber.