William Happer, Professor of Physics, Princeton University - He is a strong supporter of a clean environment. We need to be vigilant to keep land, air and waters free of real pollution, particulates, heavy metals, pathogens, but carbon dioxide (CO2) is not one of these pollutants. Carbon is the stuff of life. Our bodies are made of carbon. Every day a normal human exhales around 1 kg of CO2 - the simplest chemically stable molecule of carbon in the earth's atmosphere.