The effects of the increase in carbon dioxide have nothing to do with the quantity of oxygen. CO2 is by no means inert and has serious metabolic effects all on its own. Indeed, a concentration of 1% CO2 is used as a pesticide…
Please read this next link for more information:
CO 2 is produced by all aerobic organisms when they metabolize carbohydrates and lipids to produce energy by…en.wikipedia.org
Tell me — when you read the original article which has a half a dozen links to serious peer reviewed papers, what goes through your mind? Do you think, “All of these scientists and journals are fake”? Or do you just ignore the references entirely?