Eventually I found an article that addresses this question: https://www.nrdc.org/stories/do-we-exhale-carbon https://www.nrdc.org/stories/do-we-exhale-carbon

Eventually I found an article that addresses this question: https://www.nrdc.org/stories/do-we-exhale-carbon https://www.nrdc.org/stories/do-we-exhale-carbon It calculates that "a population of 7 billion people, breathing away for 365.25 days per year, and you get an annual CO2 output of 2.94 billion tons." It then points out that " human respiration is part of a “closed loop cycle” in which our carbon dioxide output is matched by the carbon dioxide taken in by the wheat, corn, celery, and Ugli fruit that we eat." Except, of course, for weight we add to our bodies. Of course that doesn't stop each of us from combusting 5 tons of CO2 each year.