This summary for policymakers reports on the state of scientific knowledge on ocean acidification, based on the latest research presented at The Third Symposium on the Ocean in a High-CO2 World, held in Monterey, California, in September 2012. Experts present the projected changes from ocean acidification for ecosystems and the people who rely on them, according to levels of confidence for these outcomes.
Ocean Acidification Summary for Policymakers
Third Symposium on the Ocean in a High-CO2 World
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Download the summary here, as well as the infographics that illustrate the problems that ecosystems and humans face as ocean acidification increases over the next century. The summary addresses outcomes based on whether humans continue to emit carbon dioxide at current rates to the atmosphere, or what could happen if policymakers take action to mitigate these emissions.
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.