Acidic seas could worsen warming


Oceans that grow more acidic through emissions from burning fossil fuels can amplify global warming by releasing less of a gas that helps shield Earth from radiation, a study said Sunday. The potentially vast effect that the authors uncovered is not currently factored into climate change projections.

Emissions of carbon dioxide contribute to planetary warming by trapping heat energy radiating from the surface, creating a greenhouse effect.

The study said they also lower the pH balance of the oceans and hamper production of dimethyl sulfide (DMS), a sulfur compound, by plankton. DMS released into the atmosphere helps reflect radiation from the sun, reducing surface temperatures on Earth.

Using climate simulations, the team said an 18 percent decline in DMS emissions by 2100 could contribute as much as 0.48 degree Celsius to the global temperature.

“To our knowledge, we are the first to highlight the potential climate impact due to changes in the global sulfur cycle triggered by ocean acidification,” wrote Katharina Six at the Max Planck Institute for Meteorology in Hamburg, Germany, and her colleagues. “Our result emphasizes that this potential climate impact mechanism of ocean acidification should be considered in projections of future climate change.”

They warned that ocean acidification may also have other, yet unseen, impacts on marine biology that may provoke further declines in DMS emissions. Their paper is published in the new issue of Nature Climate Change.