In greenhouses, the amount of CO2 is scaled up. By pumping extra CO2 in from gas plantsreddit.com or coal plants. That CO2 is not all taken up by the plants of course, and leaks through the cracks of the greenhouse. It looks very artificially. Also when talking about climate change we call CO2 a "greenhouse gas" because of the blanketing effect it has out in the upper atmosphere. Regular people could get confused and associate it with the literal greenhouses (as the source problem).
