Scientists have revealed new evidence that carbon dioxide is making oceans acidic and dissolving the shells of sea animals.
Ocean acidification happens when carbon dioxide produced by burning fossil fuels reacts with seawater to form carbonic acid.
The British Antarctic Survey has found shells of molluscs called sea butterflies are being degraded by acidic water in the Southern Ocean.
Reporting their findings in the journal Nature Geoscience, the scientists say increasing acidification means these animals will probably become extinct in the next few decades.
It says this will damage the Antarctic food web because sea butterflies make up much of the plankton that feeds larger creatures such as toothfish, penguins and whales.