Executive summary
Human activities are altering the chemistry of the seas at a fundamental level. Atmospheric concentrations of carbon dioxide are increasing as a result of burning of fossil fuels. As CO2 from the atmosphere dissolves in the surface ocean, seawater becomes more CO2-rich and more acidic (increased hydrogen ion levels and lower pH), resulting in substantial changes in a host of chemical properties. The pH of the oceans has been relatively constant for more than 20 million years but is now changing very quickly and will decrease from on average pH 8.1 to pH 7.8 by the end of the century – probably at least a 10 times more rapid change than anything over that period of time.
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