New Global Warming Source: Oceans

By: By Terrell Johnson

Published: August 27,2013

 

 

 

 

AP Photo/Nick Ut

The world's oceans absorb much of the carbon dioxide that humans pump into the atmosphere, which comes largely from the burning of fossil fuels. But soaking up all of that carbon is slowly changing the chemistry of the oceans, which could amplify the effects of global warming in decades to come.
That's the conclusion reached in a study released last week in the science journal Nature Climate Change, which found that as the oceans become more acidic, they cause tiny marine organisms to release less of a gas that helps protect Earth from the sun's radiation.
The gas is produced by tiny, single-celled animals called phytoplankton, which drift throughout the seas and form the base of the food chain for all larger marine life. They release a compound called dimethylsulfide (DMS), some of which floats into the atmosphere and clumps with other molecules to create atmospheric sulfur, which combines with other aerosols and water vapor to make clouds.
Clouds play a role in the Earth's albedo -- its ability to reflect solar radiation back into space from surfaces like snow, ice and clouds -- which means they also play a role in cooling the planet. But the scientists who published the study found that as the oceans become more acidic, phytoplankton release less DMS.
"On a global scale, a fall in DMS emissions due to acidification could have a major effect on climate, creating a positive-feedback loop and enhancing [global] warming," the journal Nature notes in a press release announcing the study.
They have such a big impact because phytoplankton are the biggest natural source of DMS emissions, Time Magazine notes. By the end of the century, the world's oceans are expected to release about 18 percent less DMS than before the start of the Industrial Revolution some 150 years ago.
With less DMS in the atmosphere, the study's authors say, sunlight that could have been reflected back into space would instead make it all the way to Earth's surface.
If the concentration of carbon dioxide in the atmosphere doubles by 2100, as many models project, ocean acidification could contribute as much as 0.8 degrees to the expected rise in global temperatures by then of between 3.6 and 8.1 Fahrenheit degrees.
"We were surprised that the effect was so large," Katharina Six of Germany's Max Planck Institute for Meteorology told New Scientist. "It certainly speeds up the warming."
Read the full study in Nature Climate Change.

 

MORE: Greenland, Ground Zero for Global Warming

22 / 178

A seagull stands on an iceberg that broke off from the Jakobshavn Glacier on July 23, 2013, in Ilulissat, Greenland. (Joe Raedle/Getty Images)