"Changes of PH in the ocean are so small they can't be directly measured. Ask your oceanographer friends. Again, the people working on this stuff are relying on computer models, which means any prediction of the future is worthless, because of the uncertainty involved."
I haven't gotten together with my friend recently, but will in the next week or so. Pending that, I have included a list of links to studies dealing with increasing acidification of the oceans. They are all from reputable universities and 2 scientific publications, also reputable. The studies do, indeed, rely on models, but I disagree with you when you say they are worthless as predictive tools. They all agree that the Ph of the oceans has dropped something on the order of .1 since the beginning of the Industrial Revolution, and that the likely increase in the next century will be .3 to .4. This is a very large increase in acidity and the main area of uncertainty seems to be how, and whether, the oceans' biota, beginning with phytoplankton and progressing up the food chain, will be able to adapt. They do not deal directly with the impact on O2 production by phytoplankton, but the connection is obvious: If phytoplankton suffer a massive die off, the result is fairly obvious to my mind. I suspect anything my friend , and his sources, have to add to this will not differ by much. To have this many disparate groups of scholars in agreement is, to me, compelling. And, PLEASE, Rog, spare me the scornful dismissal of the work of any reputable scientist that you disagree with as fraud perpetrated by Warmista or Acidista(my word) conspiring with the world's governments to impose a carbon tax on the benighted masses. Were I on your side of The Pond, I would probably call it balderdash, or some such Anglicism.; over here we call it BS. At any rate, I think my concern about O2 depletion is as reasonably grounded as your dismissal of it with a patronizing "try not to worry too much about it".
"If you are sufficiently interested, read this page, and then the comments from Ken Griffith near the bottom, which go unanswered...
I found the article you cite, with Mr Griffin's comments, very interesting because it dealt more directly with declining atmospheric O2, quite convincingly to my mind, Mr Griffin's comments notwithstanding. I found the section "The Mystery of the Oxygen Sink" particularly interesting in that it made a case for O2 depletion based on changes in the nature of the earth's flora brought about primarily by deforestation and modern agricultural practices. The decomposition(oxidation) of plants(trees) composed primarily of lignins and lipids, rich in reduced carbon, requires atmospheric O2 not contained in those materials. To the degree that deforestation proceeds and organic matter of similar composition in the soil is exposed to the air by plowing, there will be a reduction in atmospheric O2 as the material is oxicdized. To this I might add that, as desertification and salting of agricultural soils due poor irrigation techniques increases, less O2 will be returned to the atmosphere by photosynthesis, simply because nothing will grow, further augmenting O2 depletion. I did not see anything in Mr Griffin's comments that addressed these issues. Perhaps you could tell me what I am missing here.
There was another article I read a couple days ago, which I didn't locate this time due to slightly different search parameters, that indicated a fall in Ph can cause dissolved iron compounds to bind to particulate organic matter suspended in sea water, rendering it unavailable to phytoplankton. Sound familiar?
A list of links to ocean acidification studies.