Carbon Dioxide With Oceanic Concentration

The Earth's oceans contain a huge amount of carbon dioxide in the form of bicarbonate and carbonate ions — much more than the amount in the atmosphere. The bicarbonate is produced in reactions between rock, water, and carbon dioxide. One example is the dissolution of calcium carbonate:

CaCO₃ + CO₂ + H₂O ⇌ Ca²⁺ + 2 HCO−
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Reactions like this tend to buffer changes in atmospheric CO₂. Since the right-hand side of the reaction produces an acidic compound, adding CO₂ on the left-hand side decreases the pH of sea water, a process which has been termed ocean acidification. Reactions between carbon dioxide and non-carbonate rocks also add bicarbonate to the seas. This can later undergo the reverse of the above reaction to form carbonate rocks, releasing half of the bicarbonate as CO₂. Over hundreds of millions of years this has produced huge quantities of carbonate rocks.

Ultimately, most of the CO₂ emitted by human activities will dissolve in the ocean, however the rate at which the ocean will take it up in the future is less certain.