I think ocean acidification should stop being considered just one of the effects of GHGs and give it top-line billing. That the oceans are acidifying faster than anytime in the last 300 million years received moderate press (I think Wired had the best pop-science coverage, would love links to other good pieces). People had to read fairly deeply into coverage to read that we only stop at 300 million years because there's no decent geological record before then. Those denialists who point out that temperatures were warmer than present way back when the earth was a growing ball of lava might not have an irrelevant precedent to point to in this case.
Not only are the oceans acidifying faster, they're doing at a much faster pace, with pleasant information like this at the link:
The boundary between the Triassic and Jurassic included a large increase in atmospheric CO2 (adding as much as 1,300 to 2,400 ppm) over a relatively short period of time, perhaps just 20,000 years. The authors write, “A calcification crisis amongst hypercalcifying taxa is inferred for this period, with reefs and scleractinian corals experiencing a near-total collapse.” Again, though, it’s unclear how much of the catastrophe can be blamed on acidification rather than warming.While our CO2 level won't go as high, it's moving much faster, and the rate of change is what drives acidification and the loss of carbonates needed by calcifying species.
Additional niceties, our current ocean chemistry is even more vulnerable to change:
The ratio of magnesium to calcium in ocean water changes over time due to differences in volcanic activity along the mid-ocean ridges, among other things. When magnesium is high (as it is today), a form of calcium carbonate called aragonite becomes dominant. Aragonite is more soluble than calcite, so “aragonite seas” are more susceptible to the effects of acidification. Even though the PETM did not feature aragonite seas, it was a tumultuous time for many marine species.I haven't seen much discussion about how ocean acidification will affect climate, possibly because we have no idea. Maybe it'll be wonderful! I imagine tho that drastically changing the ocean biosphere is likely to have an effect, and because we're adjusted to the biosphere that we have, that effect is unlikely to be wonderful.
I'm sure that effect will be studied further. Wiki links to a paywalled article about potential albedo decreases due loss of oceanic clouds, presumably from reduced nucleation particles from calcifying organisms getting into the atmosphere. Wiki also speculates that acidification will help the ocean draw out more CO2 from the atmosphere.
David Archer sez calcifying plankton scatter light on their own, so their reduction can reduce albedo (Long Thaw, p. 118). OTOH I vaguely recall somewhere in his book he said that our killing off coral through acidification would leave more carbonate in solution, assisting the ocean's absorption of CO2. I interpret that as part of the road to victory in the battle against Mother Earth, but others may differ.
I almost titled this post, "Time to panic over acidification" but tried to go with something slightly more constructive. Time to get worried, at least.