Industrial agriculture and GMOs are major purveyors of man-made CO2

These organisms are responsible for breaking down organic matter and other complex molecules that contain nutrients necessary for feeding plants, including those we grow for food. When this process is obstructed, the soil becomes "dead," unable to support life without artificial injections of synthetic fertilizers and pesticides. Perhaps not surprisingly, if industrial agriculture was halted immediately, CO2 emissions of the kind constantly being warned about in the media would cease to exist within about three years.

Website:  http://www.arjonline.org/agricultural-sciences/american-research-journal-of-agriculture/