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Ocean deoxygenation and acidification

The ocean absorbs about 30% of the CO₂ we emit, which makes seawater more acidic, and warmer water holds less oxygen. Together they stress corals, shellfish and fisheries. The worry is a slow loss of ocean life that people depend on for food, not a sudden event.

The tier rates the quality of the evidence, not how likely the event is.

How it could unfold

1. 1More CO₂ dissolves in the ocean, lowering pH● strong evidence
2. 2Warming and layering of the ocean reduce oxygen (a decline of more than 2% over 1960-2010)● strong evidence
3. 3Stress on coral reefs and shell-forming organisms; shifts in fish distribution◐ moderate evidence
4. 4Effects on fisheries and coastal food security◐ moderate evidence

Historical anchors

• Past ocean anoxic events in the geological record.

What experts and models say

Expert estimates are personal judgements, not measurements, and experts disagree. This site never adds its own probabilities.

What you can do

• Little personal action applies. Sustainable seafood choices and coastal planning are collective.

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Related scenarios

• Climate tipping cascade

References

1. Schmidtko, S., Stramma, L. & Visbeck, M. (2017). Decline in global oceanic oxygen content during the past five decades. Nature 542:335-339. link ↗
2. NOAA National Ocean Service: What is ocean acidification? (the ocean absorbs about 30% of the CO₂ released into the atmosphere). link ↗