Global warming is causing a silent storm in the oceans by acidifying waters at a record rate, threatening marine life from coral reefs to fish stocks, an international study showed on Thursday.
The report, by 540 experts in 37 nations, said the seas could become 170 percent more acidic by 2100 compared to levels before the Industrial Revolution. Carbon dioxide, the main greenhouse gas, can become a mild acid when mixed with water.
Acidification is combining with a warming of ocean waters, also caused by a build-up of greenhouse gases in the atmosphere, and other man-made factors such as higher pollution and overfishing, the report said.
"It is like the silent storm - you can't hear it, you can't feel it," Carol Turley, a senior scientist at the Plymouth Marine Laboratory in England, told Reuters.
The study, released on the sidelines of a meeting of almost 200 nations in Warsaw on ways to slow global warming, estimated that acidity of the oceans had already increased by 26 percent since the Industrial Revolution in the 18th and 19th centuries.
A 170 percent increase in acidity is equivalent to cutting the Ph level of the ocean, a scale of acidity and alkalinity, to 7.9 from 8.2 on a logarithmic scale. Battery acid rates about 1 and soap, an alkaline, is about 10.
The pace of acidification was the fastest in at least 55 million years, the scientists said. Acidification undermines the ability of everything from corals to crabs to build protective shells and has knock-on effects on the food web.
"Marine ecosystems and biodiversity are likely to change as a result of ocean acidification, with far-reaching consequences for society," according to the summary led by the International Geosphere-Biosphere Programme.
"Economic losses from declines in shellfish aquaculture and the degradation of tropical coral reefs may be substantial owing to the sensitivity of molluscs and corals to ocean acidification," it said.
And some studies have found that young clown fish, made famous by the movie "Finding Nemo", behaved as if drunk in more acidic waters, their brains apparently disoriented.
Another study found that rockfish can become more anxious.
"A normal fish will swim equally in light and dark areas in a tank ... an anxious one on high carbon dioxide spends more time in the darker side, the more protected side," said Lauren Linsmayer of the University of California, San Diego.
"If society continues on the current high emissions trajectory, cold water coral reefs, located in the deep sea, may be unsustainable and tropical coral reef erosion is likely to outpace reef building this century," the report said.
Deep cuts in emissions of greenhouse gases, from power plants, factories and cars, would limit acidification.
The Warsaw talks are working on plans for a global deal, due to be agreed in 2015, to limit climate change.