Caldeira Lab Research:Ocean acidification and ocean carbon cycle

Anthropogenic carbon and ocean pH

Ken Caldeira & Michael E. Wickett

Anthropogenic CO2 release from use of fossil fuels does not only affect the carbon concentration in the atmosphere. Most of this carbon enters the ocean, altering its overall chemistry. Here the effects of CO2 on ocean pH are quantified and compared to estimates from the historical record.

Caldeira, K., and M.E. Wickett, Anthropogenic carbon and ocean pH, Nature 425, 365-365, 2003.

The effects of CO2 on ocean acidity: Maximum predicted pH changes graphed against depth (a) and atmospheric CO2 concentration (b). A .7 reduction in pH could be quite dangerous for marine life.


Most carbon dioxide released into the atmosphere as a result of the burning of fossil fuels will eventually be absorbed by the ocean, with potentially adverse consequences for marine biology. Here we quantify the changes in ocean pH that may result from this continued release of CO2 and compare these with pH changes estimated from geological and historical records. We find that oceanic absorption of CO2 from fossil fuels may result in larger pH changes over the next several centuries than any inferred from the geological record of the past 300 million years, with the possible exception of those resulting from rare, extreme events such as bolide impacts or catastrophic methane hydrate degassing.