One of the fall back positions of climate alarmists is that even if we are able to fend off warming using some geoengineering hack, and even if we are able to scrub the air of the accumulated CO2 so that concentrations fall back to earlier levels, that the oceans will still have become acidic due to their absorption of CO2. It has been argued that this will dissolve reefs and the carbonate shells of seas creatures (the polar bears daddy!).

As noted in earlier posts ^1,2,3 there are defects in this argument.

First, the seas are alkaline now and will remain alkaline. They will not become acidic though they can become less alkaline. It just isn't as scary to say that they are becoming less alkaline than it is to say that they are becoming acidic.

How much does it matter? That depends. The argument that the concentration of the carbonate ions from which shells are made is balanced by the fact that the total amount of carbon available is increased, which means larger sea creatures and more shells.

The earlier post Truer Knowledge made this point.

The laboratory findings agree with what has been observed in the oceans. Over the past 220 years, the average mass of a coccolithophore increased 40 percent as ocean pH levels dropped.

This points out a defect in the argument the seas can't process increased CO2. In fact, they do. It's food and building materials for sea creatures. If we succeed in lowering atmospheric concentrations the seas will process the dissolved carbon and become increasingly alkaline, as before.

One of the reasons that the older studies failed to grasp the reality is poor experimental design. To simulate expected decreases in alkalinity they just poured some acid into the water. Sure enough, shells dissolved. But when they decreased alkalinity by bubbling CO2 through the water in a more realistic experiment they discovered that the carbon was a benefit in some ways. It's complicated:

a team led by former WHOI postdoctoral researcher Justin B. Ries found that seven of the 18 shelled species they observed actually built more shell when exposed to varying levels of increased acidification. This may be because the total amount of dissolved inorganic carbon available to them is actually increased when the ocean becomes more acidic, even though the concentration of carbonate ions is decreased.

"Most likely the organisms that responded positively were somehow able to manipulate…dissolved inorganic carbon in the fluid from which they precipitated their skeleton in a way that was beneficial to them," said Ries, now an assistant professor in marine sciences at the University of North Carolina. "They were somehow able to manipulate CO2…to build their skeletons."

Organisms displaying such improvement also included calcifying red and green algae, limpets and temperate urchins. Mussels showed no effect.

"We were surprised that some organisms didn't behave in the way we expected under elevated CO2," said Anne L. Cohen, a research specialist at WHOI and one of the study's co-authors. "What was really interesting was that some of the creatures, the coral, the hard clam and the lobster, for example, didn't seem to care about CO2 until it was higher than about 1,000 parts per million [ppm]." Current atmospheric CO2 levels are about 380 ppm, she said. Above this level, calcification was reduced in the coral and the hard clam, but elevated in the lobster

The "take-home message, " says Cohen, is that "we can't assume that elevated CO2 causes a proportionate decline in calcification of all calcifying organisms." WHOI and the National Science Foundation funded the work.

1,000 ppm! Let's not go there.

As noted in the previous post: "Science never writes closed textbooks." We are just beginning to grasp how these things work, and we really do need a better sort of scientist with much improved experimental skills in order to gain better understanding rapidly. More openness would help greatly since hare brained ideas like pouring acid into sea water to change PH would never pass scrutiny, and progress would accelerate.