The equivalent of ~25% of current anthropegenic CO2 additions to the atmospheric reservoir is buffered by the oceans:

Net moles CO2 m-2 yr-1

Dissolved CO2 exists as different species: CO2(aq), HCO3-(aq) and CO3=(aq). Ocean pH is the dominant control on this speciation, itself a function of pCO2:

Dissolved Inorganic Carbon ('DIC') speciation (in log(mol per litre) units) as a function of ocean pH. Partial pressure of CO2 (in log(pCO2, atm) units) also shown. {www.realfuture.org}

CO2 speciation greatly affects CO2 fluxing across the ocean-atmosphere boundary, as only non-ionized species (that is, CO2(aq)) are free to exchange with the atmosphere. Anthropogenic increases in ocean acidity can be expected to greatly lower the CO2 buffering capacity of our oceans.

~55 million years ago, the Paleocene/Eocene Thermal Maximum saw global temperature increase by ~5°C in ~15000 years:

Zachos (2001), 'Trends, Rhythms, and Aberrations in Global Climate', Science 292, p. 686.

Today, we face a similar ~5°C temperature increase, but wrought within ~one tenth the amount of time:

Solomon et al. (2009), 'Irreversible climate change due to carbon dioxide emissions', PNAS 106, p. 1704-1709.

How will the {Earth System}’s negative feedback cycles respond in the face of this unprecedented rate of change?