Ocean surface pH declined from 8.2 to below 8.1 over the industrial era as a result of an increase in atmospheric CO 2 concentrations. This decline corresponds to an increase in oceanic acidity of about 30%. Reductions in surface water pH are observed across the global ocean. Ocean acidification has impacts on marine organisms and has already affected the deep ocean, particularly at high latitudes. Models project further ocean acidification worldwide. The target under United Nations Sustainable Development Goal 14.3 is to minimise the impacts of this by 2030.