Since the beginning of the industrial revolution, the ocean has absorbed about one third of the carbon dioxide (CO2) released by human activities. This results in ocean acidification, often referred to as "the other CO2 problem", alongside global warming.
Ocean acidification is a change in sea water chemistry; CO2 reacts with water molecules (H2O) and forms the weak acid H2CO3 (carbonic acid). It is estimated that if CO2 continues to be released at the same rate as today, ocean acidity will increase by 170% compared to pre-industrial levels. The changes are happening at least 10 times faster than at any moment in the geological past.
The biological impacts of ocean acidification are still poorly understood. One of the most likely consequences is the slower growth of organisms forming calcareous skeletons or shells, such as corals and mollusks.