Ocean carbon models and the sediment record both indicate that chemical recovery from projected CO2 emissions will require thousands of years (chemical equilibration with carbonate minerals) to hundreds of thousands of years (equilibration with the carbonate-silicate cycle) [4]. This means that the chemical effects of CO2 released from anthropogenic sources are not confined to a century time scale.

Diversity of the sea bed dwelling organisms after the acidification event 55 Ma ago took several hundreds of thousands of years to recover. In contrast, there is evidence that planktonic calcifiers tracked their habitat during this event (e.g. tropical species migrated towards the poles), thereby avoiding extinction [88]. The geological record also shows that Scleractinian corals have survived several mass extinction events, likely due to perturbations in the carbon cycle, but they took several millions of years to recover [89 91]. These lessons from the past indicate that should increasing ocean acidification lead to significant loss of biodiversity and even extinction, biological systems may not 'recover' to pre-industrial ecosystems, but rather may 'transition' to a new state.

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