Human pollution is turning seas acidic so quickly the coming decades will recreate conditions not seen on Earth since the era of the dinosaurs, scientists have warned.
The rapid acidification is caused by CO2 belched from chimneys and exhausts that dissolve in the ocean. The chemical change is placing unprecedented pressure on marine life and could cause widespread extinctions, the experts say.
The study, by scientists at Bristol University in south-west England, was presented at a special three-day summit of climate scientists in Copenhagen this month. The conference was intended to update the science of global warming and move politicians into acting on carbon emissions.
The study predicts “dangerous” levels of ocean acidification and severe consequences for organisms called marine calcifiers, which form chalky shells. It says: “We find the future rate of surface ocean acidification and environmental pressure on marine calcifiers very likely unprecedented in the past 65mn years.”
The situation in the deep sea is of greater concern, the scientists say.
The researchers compared the current acidification rate with a giant prehistoric release of greenhouse gas, which geologists know caused widespread extinction of deep water species.
The summary reads: “Because the rates of acidification between past and future are comparable, and (because) there was widespread extinction of benthic (lowest living) organisms, one must conclude that a similar level of extinction is more likely than not in the future.”
Concern about ocean acidification from CO2 has grown in recent years, but the issue receives less attention than global warming – also caused by humans.
The Bristol study is one of the first to predict the consequences of acidic waters by looking at past events. It says future deep sea acidification must be limited to 0.2 pH units to avoid the worst effects. The pH of surface waters, where the CO2 is absorbed from the atmosphere, has fallen by about 0.1 units since the industrial revolution, though it will take longer for the acid to reach deeper water.
Ocean acidification was one of the key topics at the Copenhagen summit. Ken Caldeira, an expert on ocean acidification at the Carnegie Institution in California, told the conference that the next few decades could produce profound changes in the oceans.
He said: “If we do not cut carbon dioxide emissions deeply, and soon, the consequences of ocean acidification will stand out against the broad reaches of geologic time.
“Those consequences will remain embedded in the geologic record as testimony from a civilisation that had the wisdom to develop high technology but did not develop the wisdom to use it wisely.”
Other experts reported that acidification was already affecting marine life in the Arctic and Antarctic. They also discussed a finding that acid waters carried sound more efficiently, so the oceans would become noisier in future.
The conference came during a year of high-level political discussions on climate change, which culminate in international negotiations in Copenhagen in December, where officials will try to hammer out a successor to the Kyoto protocol.
Katherine Richardson, a marine biologist at the University of Copenhagen, who organised the conference, has described it as “a deliberate attempt to influence policy”. She said many scientists were concerned that politicians had not grasped the seriousness of the situation, despite a string of increasingly gloomy predictions.
The meeting updated the 2007 report of the Intergovernmental Panel on Climate Change (IPCC). A number of studies published since the IPCC report was prepared show that carbon emissions are rising faster than expected and that existing greenhouse gas targets may not be enough to prevent catastrophic temperature rise. It also assessed whether projected sea level rises had been underestimated, and if there was still a realistic chance that average global temperature rise could be limited to 2C.
David Adam, Gulf Times, 18 March 2009. Article.
