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Ocean acidification


  • Surface-ocean pH has declined from 8.2 to below 8.1 over the industrial era due to the growth of atmospheric CO2 concentrations. This decline corresponds to an increase in oceanic acidity of about 30%.
  • Observed reductions in surface-water pH are nearly identical across the global ocean and throughout Europe’s seas.
  • Ocean acidification in recent decades is occurring a hundred times faster than during past natural events over the last 55 million years.
  • Ocean acidification already reaches into the deep ocean, particularly in the high latitudes.
  • Models consistently project further ocean acidification worldwide. Surface ocean pH is projected to decrease to values between 8.05 and 7.75 by the end of 21st century depending on future CO2 emission levels. The largest projected decline represents more than a doubling in acidity.
  • Ocean acidification may affect many marine organisms within the next 20 years and could alter marine ecosystems and fisheries.

Reference information



acidity, clim043, ocean

Climate impacts

Extreme Temperatures, Water Scarcity


Observations and Scenarios


Marine and Fisheries

Geographic characterization


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