The rate at which the world's oceans are acidifying is "unprecedented," scientists warn in a new report.
The rate may be faster than at any time in the last 300 million years, they say.
The report, which will be launched Monday at the UN climate talks in Warsaw, is based on research presented by over 500 international experts on ocean acidification who convened at The Third Symposium on the Ocean in a High CO2 World in September 2012.
According to their summary of findings, human-caused CO2 emissions have already caused a 26 percent-increase in ocean acidification since the start of the Industrial Revolution. If current rates of CO2 emissions continue, the report projects a 170 percent-increase in acidity levels by 2100.
The report states that "The most comparable event 55 million years ago was linked to mass extinctions of calcareous deep-sea organisms and significant changes to the surface ocean ecosystem. At that time, though the rate of change of ocean pH was rapid, it may have been 10 times slower than current change."
With increased acidification, the scientists predict "far-reaching effects." Ecologically and commercially valuable species like coral communities and mollusks are likely to suffer, and that will bring "cascading" effects, some of which are already noticeable.
Prof Jean-Pierre Gattuso, from CNRS, the French national research agency, told the BBC, "In the Southern Ocean, we already see corrosion of pteropods which are like sea snails, in the ocean we see corrosion of the shell."
"They are a key component in the food chain, they are eaten by fish, birds and whales, so if one element is going then there is a cascading impact on the whole food chain," Gattuso said.
Among the findings the scientists agreed on with very high levels of confidence: "The legacy of historical fossil fuel emissions on ocean acidification will be felt for centuries."
"What we can now say with high levels of confidence about ocean acidification sends a clear message," one of the lead authors, Ulf Riebesell of GEOMAR Helmholtz Centre for Ocean Research Kiel, said in a statement. "Globally we have to be prepared for significant economic and ecosystem service losses. But we also know that reducing the rate of carbon dioxide emissions will slow acidification. That has to be the major message for the COP19 meeting."
* * *