human Co2 causes? I was thinking about Co2 causes that were never listed and thought about increaseing population. Everybody talkes about global warming from Co2, but I was thought about something I never thought of before. Everybody when they breathe, breathes in oxygen and when they breathe out , they breathe out carbon dioxide (CO2), with increasing population could cause even more increasing CO2 as the population increases due to more people breatheing out CO2. I do not know much about this, but at least have this as a discussion. THanks!!