What percentage of the total carbon in the land, ocean, and atmosphere (excluding the sedimentary rocks) is in the atmosphere? 9. considering this answer, why is the level of carbon in the atmosphere considered so important? 10. scientists monitoring carbon dioxide in the atmosphere estimate that of the 7.1 gt of carbon dioxide released annually by human activities, approximately 3.2 gt remain there. another 2 gt diffuse into the ocean. how many gt of carbon are unaccounted for? what are some of the hypotheses to explain what happens to this missing carbon? 7