Apocalyptic warnings about the effect of global warming on the oceans now embrace ocean acidification as well as sea level rise and ocean heating, both of which I’ve examined in previous posts. Acidification is a potential issue because the oceans absorb up to 30% of our CO₂ emissions, according to the UN’s IPCC (Intergovernmental Panel on Climate Change). The extra CO₂ increases the acidity of seawater.

But there’s no sign that any of the multitude of ocean inhabitants is suffering from the slightly more acidic conditions, although some species are affected by the warming itself. The average pH – a measure of acidity – of ocean surface water is currently falling by only 0.02 to 0.03 pH units per decade, and has dropped by only 0.1 pH units over the whole period since industrialization and CO₂ emissions began in the 18th century. These almost imperceptible changes pale in comparison with the natural worldwide variation in ocean pH, which ranges from a low of 7.8 in coastal waters to a high of 8.4 in upper latitudes.

The primary concern with ocean acidification is its effect on marine creatures – such as corals, some plankton, and shellfish – that form skeletons and shells made from calcium carbonate. The dissolution of CO₂ in seawater produces carbonic acid (H₂CO₃), which in turn produces hydrogen ions (H⁺) that eat up any carbonate ions (CO₃^2-) that were already present, depleting the supply of carbonate available to calcifying organisms, such as mussels and krill, for shell building.

A 2011 study of coral formation in Papua New Guinea at underwater volcanic vents that exude CO₂ found that coral reef formation ceased at pH values less than 7.7, which is 0.5 units below the pre-industrial ocean surface average of 8.2 units and 216% more acidic. However, at the present rate of pH decline, that point won’t be reached for at least another 130 to 200 years. In any case, there’s empirical evidence that existing corals are hardy enough to survive even lower pH values.

Australia’s Great Barrier Reef periodically endures surges of pronouncedly acid rainwater at the low pH of about 5.6 that pours onto the Reef from flooding of the Brisbane River, which has occurred 11 times since 1840. But the delicate corals have withstood the onslaught each time. And there have been several epochs in the distant past when the CO₂ level in the atmosphere was much higher than now, yet marine species that calcify were able to persist for millions of years.

Nonetheless, advocates of the climate change narrative insist that marine animals and plants are headed for extinction if the CO₂ level continues to rise, supposedly because of reduced fertility and growth rates. However, there’s a paucity of research conducted under realistic conditions that accurately simulates the actual environment of marine organisms. Acidification studies often fail to provide the organisms with a period of acclimation to lowered seawater pH, as they would experience in their natural surroundings, and ignore the chemical buffering effect of neighboring organisms on acidification.