The Supreme Court, in a burst of scientific ignorance, recently proclaimed that CO2 is a pollutant. The reason is alleged global temperature increase due to the greenhouse gas effect. Of course, the primary greenhouse gas in water vapor, and the assumption that a temperature increase due to increased CO2 concentration would also increase the amount of water vapor in the air as relative humidity would remain constant. So far this assertion has not been borne out by actual experience. At the same time, the Supreme Court and the EPA appear to take no note of the fact that plant life could not exist without CO2 in the atmosphere. Nor, that increasing the amount of CO2 in the air increases the rate of plant growth, and makes plant growth more robust with less water, resulting in plant growth in arid areas. Here is an article that discusses this. By the way, I am still looking for the explanation of how James Hansen, Al Gore, and others determined that the ideal atmospheric CO2 concentration is 280 ppm(v).