What is happening now - High
The uptake of anthropogenicA change within part of the climate system that can be attributed to human action, rather than natural causes. carbon since 1750 has led to the oceans becoming more acidic with an average decrease in ph of 0.1 units (IPCC, 2007a) (High certainty). However, the effects of current, observed ocean acidification on the marine biosphere are as yet undocumented (IPCC, 2007b) due, in part, to lack of research in this area and long term time series.
High confidence, that ocean pH is changing and will change in the future and unless we substantially and urgently reduce CO2 emissions that these will have major impacts on aragonitic organismsOrganisms that use the aragonite or calcite form of calcium carbonate to form their mineral parts, such as shells. this century.
What could happen in the future - Medium
We have a moderate level of confidence that this will have a knock-on effect on marine ecosystems and foodwebs, according to evidence from modelling and experimental observations.
Impacts of pH on other organisms than aragonitic and calcitic organisms is theoretically serious (e.g. impact on nutrient speciationHow the main element is contained within a nutrient molecule e.g. Nitrogen may be in nitrate, nitrite or other forms. and therefore primary production and biodiversity) but there has been little research on this.
We have a high degree of confidence that reducing emissions is the only way of reducing ocean acidification.