'Unprecedented Rapidity of CO2' Causing Worst Ocean Acidification in 300 Million Years

The Earth's oceans are becoming more acidic at a faster rate than at any time in the past 300 million years due to increased levels of CO2 in the atmosphere, a new study shows.

The study, published in the journal Science, details the work of 21 scientists from the U.S. and Europe.

"The geological record suggests that the current acidification is potentially unparalleled in at least the last 300 million years of Earth history, and raises the possibility that we are entering an unknown territory of marine ecosystem change," said co-author Andy Ridgwell of Bristol University.

The Albany Times Union explains:

Ocean acidification works like this: Burning of fossil fuels like oil, coal and natural gas releases the greenhouse gas carbon dioxide (CO2) into the atmosphere, There, the gas keeps more of the heat from the sun from radiating back into space, a process that an international scientific consensus says is gradually raising the planet's temperature.

At the same time, about a quarter of the increasing CO2 is being absorbed by the oceans, where it is converted into carbonic acid. This is steadily making the ocean more acidic, which among other things can harm the ability of sea creatures to thrive, or make hard shells or skeletons. Rising acidification can also affect marine organisms by causing slower growth, fewer offspring, muscle wastage and dwarfism.

Some scientists have called this gradual process the "evil twin" of climate change.

The study "raises the possibility that we are entering an unknown territory of marine ecosystem change," said Andy Ridgwell, a professor of planetary modeling at the University of Bristol who took part in the study.

Agence France-Presse reports on the study:

The acidification may be worse than during four major mass extinctions in history when natural pulses of carbon from asteroid impacts and volcanic eruptions caused global temperatures to soar, said the study in the journal Science. [...]

They found only one time in history that came close to what scientists are seeing today in terms of ocean life die-off -- a mysterious period known as the Paleocene-Eocene Thermal Maximum about 56 million years ago.

Though the reason for the carbon upsurge back then remains a source of debate, scientists believe that the doubling of harmful emissions drove up global temperatures by about six degrees Celsius and caused big losses of ocean life. [...]

"We know that life during past ocean acidification events was not wiped out -- new species evolved to replace those that died off," said lead author Barbel Honisch, a paleoceanographer at Columbia University's Lamont-Doherty Earth Observatory.

"But if industrial carbon emissions continue at the current pace, we may lose organisms we care about -- coral reefs, oysters, salmon."

Honish and colleagues said the current rate of ocean acidification is at least 10 times faster than it was 56 million years ago.

Ars Technica adds:

While the authors frequently point out the difficulty in teasing apart the effects of ocean acidification and climate change, they argue that this is really an academic exercise. It's more useful to consider the witches' brew with all the ingredients--acidification, temperature change, and changes in dissolved oxygen--since, historically, those have come together. That combination produces unequivocally bad news.

The authors conclude, "[T]he current rate of (mainly fossil fuel) CO2 release stands out as capable of driving a combination and magnitude of ocean geochemical changes potentially unparalleled in at least the last ~300 [million years] of Earth history, raising the possibility that we are entering an unknown territory of marine ecosystem change."