The early atmosphere was comprised of a high amount of carbon dioxide and water vapor. These water vapors have undergone the process of condensation and resulted in the formation of oceans. The carbon dioxide gas was mostly consumed by primitive lives such as the blue-green algae, and cyanobacteria, and by carrying out the process of photosynthesis, it liberated oxygen.
Some amount of carbon dioxide was also brought down from the atmosphere by mixing up with the rainwater (acid rain), and are mostly concentrated in the deeper zone of the oceans forming limestones.
Currently, a total of about 0.03% of CO₂ is present in the atmosphere in today's world.
