What is the role for carbon dioxide on this earth?
We would die without carbon dioxide – carbon dioxide is essential to the production of oxygen! Trees and green plants ingest carbon dioxide from the atmosphere; plankton and green algae from the salt water (including ocean) or fresh water they live in. These green things produce oxygen as part of the process of photosynthesis. Oxidation produces some carbon dioxide, too, but the net effect is to give off less carbon dioxide, and produce more oxygen than they use. Carbon dioxide in the atmosphere forms part of the greenhouse effect, which, if its levels are not disturbed, keeps the earth pleasantly warm enough for life.