Ocean acidity has been relatively stable for over 20 million years.

The ocean is becoming more acidic as increasing atmospheric carbon dioxide (CO₂) is absorbed at the sea surface. Models suggest that surface pH has decreased by 0.1 pH unit since pre-industrial times.

Model projections suggest that the change in average pH in UK waters this century will exceed its current range of variation.

The full impacts of acidification remain largely unknown but organisms such as corals, some plankton, shellfish and sea urchins are expected to become less able to produce calcareous parts, such as shells, by the middle of this century.

HIGH

(for pH change)