The world's oceans are becoming more acidic because of the amount of carbon dioxide they have absorbed, threatening sea life and the planet's fragile food chain, a climate expert said.
Oceans have already absorbed a third of the world's emissions of carbon dioxide, one of the heat-trapping gases blamed for global warming, leading to acidification that prevents vital sea life from forming properly.
"The oceans are rapidly changing," Professor Stefan Rahmstorf said on Thursday, on the sidelines of a UN conference on climate change that has drawn delegates from more than 100 countries to Kenya. "Ocean acidification is a major threat to marine organisms."
Fish stocks and the world's coral reefs could also be hit while acidification risks "fundamentally altering" the food chain, he said.
In a study titled "The Future Oceans -- Warming Up, Rising High, Turning Sour," Rahmstorf and eight other scientists warned that we are witnessing on a global scale problems similar to the acid rain phenomenon of the 1970s and 1980s.
The report was undertaken by the German Advisory Council on Global Change.
He says further research is urgently needed to assess the impact of ocean acidification.
David Santillo, a senior scientist at Greenpeace's Research Laboratories in Exeter, Britain, said it had come as a shock to scientists that the oceans are turning acidic because of carbon dioxide emissions.
"The knock on effect for humans is that some of these marine resources that we rely on may not be available in the future," the marine biologist, who was not involved in Rahmstorf's study said.
Rahmstorf also reiterated warnings of rising sea levels caused by global warming, saying that in 70 years temperature increases will lead to more frequent storms with 200 million people threatened by floods.
Scientists blame the past century's rise in average global temperatures at least in part on the accumulation of carbon dioxide, methane and other gases in the atmosphere -- byproducts of power plants, automobiles and other fossil fuel burners.
"Unabated continuation of this trend will lead to a level of ocean acidification that is without precedent in the past several million years and will be irreversible for millennia," said Rahmstorf, head of Germany's Potsdam Institute for Research into Climatic Effects.
Africa is the continent expected to suffer most from shifting climate zones and droughts, like the one now in its fourth year in East Africa.
He also called on industrialized nations to continue to reduce their greenhouse-gas emissions. Under the 1997 Kyoto accord, 35 industrialized countries agreed to reduce greenhouse gas emissions by 5 percent below 1990 levels by 2012.
In Nairobi, the Kyoto countries are continuing talks on what kind of emissions targets and timetables should follow 2012.