Oceans acidifying at unprecedented speed

Humanity's greenhouse gas emissions may be acidifying the oceans at a faster rate than at any time in the last 300 million years. The sheer speed of change means we do not know how severe the consequences will be.

As well as warming the planet, carbon dioxide seeps into the oceans and forms carbonic acid. As a result the water becomes more acidic.

The pH is currently dropping by about 0.1 per century. This ocean acidification harms organisms such as corals that rely on dissolved carbonate to make their shells. It also disrupts behaviour in some animals.

B?rbel H?nisch of Columbia University in Palisades, New York, and colleagues used the chemical record preserved in rocks to gauge previous ocean acidification events.

The best match for current changes was the Palaeocene-Eocene thermal maximum of 55 million years ago, when vast amounts of methane were released into the atmosphere causing rapid global warming, ocean acidification, and mass extinction. But even then, it took at least 3000 years for ocean pH to drop by 0.5. "That is an order of magnitude slower than today," H?nisch says.

The 300-million-year period that H?nisch and colleagues studied includes the biggest extinction of them all: the end-Permian extinction. This event, 252 million years ago, wiped out up to 96 per cent of marine species. But it probably had other causes.

Acidification is not the only threat to the oceans from greenhouse gases, says Nicolas Gruber of the Swiss Federal Institute of Technology Zurich in Switzerland. Marine life also faces a threat from rising water temperatures and less dissolved oxygen.

"We have to think about these effects co-occurring," Gruber says. While we have information on the consequences of each individual factor, we have no idea what the combined effect will be.

Journal reference: Science, DOI: 10.1126/science.1208277

If you would like to reuse any content from New Scientist, either in print or online, please contact the syndication department first for permission. New Scientist does not own rights to photos, but there are a variety of licensing options available for use of articles and graphics we own the copyright to.

Have your say

Only subscribers may leave comments on this article. Please log in.

Only personal subscribers may leave comments on this article

Subscribe now to comment.

All comments should respect the New Scientist House Rules. If you think a particular comment breaks these rules then please use the "Report" link in that comment to report it to us.

If you are having a technical problem posting a comment, please contact technical support.

Source: http://feeds.newscientist.com/c/749/f/10897/s/1d12edf1/l/0L0Snewscientist0N0Carticle0Cdn215340Eoceans0Eacidifying0Eat0Eunprecedented0Espeed0Bhtml0DDCMP0FOTC0Erss0Gnsref0Fonline0Enews/story01.htm

taco bell breakfast menu ener1 national chocolate cake day epstein joshua komisarjevsky barney frank barney frank