This is one scary report.
The more acidic the ocean becomes, the less calcium carbonate is available for corals.
"The new IPCC report, which is designed to give impetus to the negotiations, highlights the little-known acidification of the oceans, first reported in this newspaper more than three years ago. It concludes that emissions of carbon dioxide – the main cause of global warming – have already increased the acidity of ocean surface water by 30 per cent, and threaten to treble it by the end of the century.
Achim Steiner, the executive director of the United Nations Environment Programme (UNEP), said yesterday: "The report has put a spotlight on a threat to the marine environment that the world has hardly yet realised. The threat is immense as it can fundamentally alter the life of the seas, reducing the productivity of the oceans, while reinforcing global warming."
Scientists have found that the seas have already absorbed about half of all the carbon dioxide emitted by humanity since the start of the industrial revolution, a staggering 500 billion tons of it. This has so far helped slow global warming – which would have accelerated even faster if all this pollution had stayed in the atmosphere, already causing catastrophe – but at an increasingly severe cost.
The gas dissolves in the oceans to make dilute carbonic acid, which is increasingly souring the naturally alkali seawater. This, in turn, mops up calcium carbonate, a substance normally plentiful in the seas, which corals use to build their reefs, and marine creatures use to make the protective shells they need to survive. These include many of the plankton that form the base of the food chain on which all fish and other marine animals depend.
As the waters are growing more acid this process is decreasing, with incalculable consequences for the life of the seas, and for the fisheries on which a billion of the world's people depend for protein. Every single species that uses calcium in this way, that has so far been studied, has been found to be affected. And the seas are most acid near the surface, where most of their life is concentrated."
A world dying, but can we unite to save it? - Independent Online Edition > Climate Change
Ocean Surface Water 30% More Acidic 
