Ocean Acidification Summary for Policymakers 2013

Ocean pH in 2100

The average pH of ocean surface waters has fallen by about 0.1 units, from 8.2 to 8.1, since the beginning of the industrial revolution. This corresponds to a 26% increase in acidity. Please see original infographic for sources and further information.

Ocean pH in 1850

Compared with preindustrial levels shown here, the projected increase in ocean acidity is about 170% by 2100 if high CO2 emissions continue (RCP* 8.5).

Atmospheric CO2 and ocean pH

Observations of CO2 (parts per million) in the atmosphere and pH of surface seawater from Mauna Loa and Hawaii Ocean Time-series (HOT) Station Aloha, Hawaii, North Pacific.

Credit: Adapted from Richard Feely (NOAA), Pieter Tans, NOAA/ESRL (www.esrl.noaa.gov/gmd/ccgg/trends) and Ralph Keeling, Scripps Institution of Oceanography (scrippsco2.ucsd.edu)

Observed CO2 emissions and emissions scenarios to 2100

Global CO2 emissions (white dots, uncertainty in grey) from fossil fuel use is following the high emissions trajectory (red line, RCP* 8.5) predicted to lead to a significantly warmer world. Large and sustained emissions reductions (blue line, RCP* 2.6) are required to increase the likelihood of remaining within the internationally agreed policy target of 2°C. 

Credit: Glen Peters and Robbie Andrew (CICERO) and the Global Carbon Project, adapted from Peters et al., 2013 (reference 8). Historic data from Carbon Dioxide Information Analysis Center.

Ocean surface pH projections to 2100

Modelled global sea-surface pH from 1870 to 2100. The blue line reflects estimated pH change resulting from very low CO2 emissions to the atmosphere (IPCC Representative Concentration Pathway, RCP* 2.6). The red line reflects pH from high CO2 emissions (the current emissions trajectory, RCP* 8.5).

Credit: Adapted from Bopp et al., 2013 (reference 9).

Aragonite saturation in 2100

This map shows the “saturation state” for the mineral form of calcium carbonate called aragonite.

If Ω is less than 1 (Ω<1), conditions are corrosive (undersaturated) for aragonite-based shells and skeletons. Coral growth benefits from Ω≥3.

By 2100, computer model projections show that Ω will be less than 3 in surface waters around tropical reefs if CO2 emissions continue on the current trajectory.

Aragonite saturation 1850-1860

Aragonite saturation for surface ocean waters, at the beginning of the industrial revolution.