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Ocean acidification increases warming

Increased effect Oceans that grow more acidic through increased carbon emissions, amplify global warming by releasing less of a gas that helps shield Earth from solar radiation, a new study reveals.

And the authors of the paper, which appears today in the journal Nature Climate Change, warn the potentially vast effect they uncovered is not currently factored into climate change projections.

Katharina Six of the Max Planck Institute for Meteorology, and colleagues, say human-induced carbon dioxide (CO2) emissions contribute to planetary warming by letting the Sun's heat through the atmosphere but trapping heat energy reflected back from Earth, so creating a greenhouse effect.

They also lower the pH balance of the world's oceans, making them less alkaline (acidification), and hamper production of dimethyl sulphide (DMS), a sulphur compound made by plankton, the researchers write.

DMS released into the atmosphere helps reflect incoming radiation from the Sun, reducing surface temperatures on Earth.

Using climate simulations, the team said an 18 per cent decline in DMS emissions by 2100 could contribute as much as 0.48°C to the global temperature.

"To our knowledge, we are the first to highlight the potential climate impact due to changes in the global sulphur cycle triggered by ocean acidification," the authors write.

"Our result emphasises that this potential climate impact mechanism of ocean acidification should be considered in projections of future climate change."

They warn that ocean acidification may also have other, yet unseen, impacts on marine biology that may provoke further declines in DMS emissions.