Everyone knows that carbon dioxide is critical for life on earth. CO2 is where humans get their oxygen and plants get their food. No CO2, no life on earth. Implicit in your Climate Change argument is that at some point, CO2 stops being critical for life and becomes a pollutant. At what CO2 concentration in the atmosphere is your inflection point? That is, what is the CO2 concentration in the atmosphere where CO2 stops being life sustaining and becomes dangerous to the planet? You need to know the answer. It is literally a life or death question.