The Revelle factor is a measure of the resistance to atmospheric carbon dioxide

Carbon dioxide

Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

 being absorbed by the ocean surface layer posed by bicarbonate

Bicarbonate

In inorganic chemistry, bicarbonate is an intermediate form in the deprotonation of carbonic acid...

 chemistry. It is named after the oceanographer Roger Revelle

Roger Revelle

Roger Randall Dougan Revelle was a scientist and scholar who was instrumental in the formative years of the University of California, San Diego and was one of the first scientists to study global warming and the movement of Earth's tectonic plates...

.

Thermodynamics

In order to enter the ocean, carbon dioxide gas has to partition into one of the components of carbonic acid

Carbonic acid

Carbonic acid is the inorganic compound with the formula H2CO3 . It is also a name sometimes given to solutions of carbon dioxide in water, because such solutions contain small amounts of H2CO3. Carbonic acid forms two kinds of salts, the carbonates and the bicarbonates...

: carbonate

Carbonate

In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, . The name may also mean an ester of carbonic acid, an organic compound containing the carbonate group C2....

 ion, bicarbonate

Bicarbonate

In inorganic chemistry, bicarbonate is an intermediate form in the deprotonation of carbonic acid...

 ion, or protonated carbonic acid, and the product of these many chemical dissociation constant

Dissociation constant

In chemistry, biochemistry, and pharmacology, a dissociation constant is a specific type of equilibrium constant that measures the propensity of a larger object to separate reversibly into smaller components, as when a complex falls apart into its component molecules, or when a salt splits up into...

s factors into a "back-pressure" that limits how fast the carbon dioxide can enter the surface ocean.

Revelle factors and Anthropogenic CO₂

The capacity of the ocean waters to take up surplus (anthropogenic

Anthropogenic

Human impact on the environment or anthropogenic impact on the environment includes impacts on biophysical environments, biodiversity and other resources. The term anthropogenic designates an effect or object resulting from human activity. The term was first used in the technical sense by Russian...

) CO₂ is inversely proportional to the value of the Revelle factor. Hence, in modern day oceans, it is possible to see the concentrations of anthropogenic CO₂ by measuring the Revelle factor; the lower the Revelle factor, the greater the amount of anthropogenic CO₂. Low Revelle factors are typically found in the warmer tropical to subtropical waters, whereas higher Revelle factors are found in the colder high latitude waters. The North Pacific has much greater Revelle factors due to its greater alkalinity

Alkalinity

Alkalinity or AT measures the ability of a solution to neutralize acids to the equivalence point of carbonate or bicarbonate. The alkalinity is equal to the stoichiometric sum of the bases in solution...

, and hence has lower anthropogenic CO2.

The Revelle Effect

If CO₂ in the atmosphere is increased by one part per million, the CO₂ in the ocean is increased by only a tenth of a part per million, because of the way that the carbon dioxide in the water is partitioned between carbonate ions and bicarbonate ions and free CO₂. As additional CO₂ is added, it tips the equilibrium between these three kinds of carbon dioxide, so because of the Revelle Factor, it means that you can add a large amount of CO₂ to the air without adding much to the water. This is known as the Revelle Effect.