As usual no hard examples - just more ad hominem smears ..... yawn.

I am a recently retired software engineer, for those that care about facts.

RR - 'avowed catastrophist' is ad hominem and adds precisely zero to the 'debate'.

You are very good at finding folk who are good with evocative language, but rather short of scientific facts,

The facts are there, however they are generally published in academic journals, such as Nature for example, which you have decided is unreliable. No reasons given for dismissing one of the pre-eminent publications on the planet naturally. Perhaps you could furnish an example of a Nature article getting it badly wrong?

Would these people who are concerned about the corals, but you have deemed 'short of scientific facts' include Professor Ove Hoegh-Guldberg, whose PhD thesis was on coral biology and as of 5 October 2009, had published 236 journal articles, and been cited 3,373 times? Or Distinguished Professor Terry Hughes (awarded the Einstein Professorship) whose publications (why did he bother?) have been cited over 43,000 times, or Professor Simon Donner, curator of the coral bleaching database, who has been engaging in public outreach and engagement, public speaking and blogging for decades? There are, of course, many more, for example Professor Hughes was lead author on the paper on the 2016 bleaching event on which enterprise he had 15 coauthors.

Passionate and expert these people are, but they do not strike me as factually challenged.

I fear Ridd's travails are of his own making. He has been making a contrarian case in the literature and the media since at least 2007. But his views have not gained much traction. For example his recent assertion that Great Barrier Reef observations were not of sufficient quality to underpin policy were shown to be unfounded …

This is a response to the published Viewpoint by Larcombe and Ridd (2018). We agree with Larcombe and Ridd (2018) that scientific merit goes hand in hand with rigorous quality control. However, we are responding here to several points raised by Larcombe and Ridd (2018) which in our view were misrepresented. We describe the formal and effective science review, synthesis and advice processes that are in place for science supporting decision-making in the Great Barrier Reef. We also respond in detail to critiques of selected publications that were used by Larcombe and Ridd (2018) as a case study to illustrate shortcomings in science quality control. We provide evidence that their representation of the published research and arguments to support the statement that “many (…) conclusions are demonstrably incorrect” is based on misinterpretation, selective use of data and over-simplification, and also ignores formal responses to previously published critiques.

https://www.sciencedirect.com/science/article/pii/S0025326X18301425

Like it or not, all Universities have a policy on engaging with the media, and going to the press and describing colleagues as 'untrustworthy', as Ridd did, oversteps that mark. He was censured, and warned that he was in breach of the University Code of Conduct. And yet he persisted, further alleging the Australian Institute of Marine Science of being untrustworthy. The University really had no option but to act.

Naturally, this is being spun as an example of a contrarian voice being suppressed. But this is really not a freedom of speech issue; for a decade the University has tolerated Ridd writing things like 'there is a swindle by scientists, politicians and most green organisations regarding the health of the Great Barrier Reef' but supplying little or no supporting evidence. None of his supporters seem to have entertained the fairly obvious proposition that he is simply wrong.

More here

as it is an attempt to explain why the persons involved have determined the causes and effects of what they are observing, in spite of the evidence.

Please point to some of this evidence? Where do you get your evidence from if you believe that the literature, including the editors of Nature are part of the conspiracy?

For those who subscribe to the risible notion that the Australian academic community is a hotbed of blinkered alarmism, here's a recent literature review from um, Wales.

https://link.springer.com/article/10.1007%2Fs40641-018-0087-0

Denier
NOUN

A person who denies something, especially someone who refuses to admit the truth of a concept or proposition that is supported by the majority of scientific or historical evidence.

https://en.oxforddictionaries.com/definition/denier

Perfectly good word, I generally avoid it as it has connotations that enable people to claim persecution, and avoid dealing with the argument: as just happened. So, linguistic objections aside, I think the onus is on you to point out the factual or logical errors in what Redfearn or I have written about the Ridd case.

My prediction is that his legal action will fail; he continued to breach his employers' Code of Conduct despite plentiful warnings, and he will deservedly descend into obscurity.

"So, while they are prepared to acknowledge that they have incomplete knowledge, they remain fully prepared to continue with their presumptions that any bleaching is being caused by warming oceans, and that, somehow, it is humans that are the cause."

Not actually the case, this paper is about the need for a bleaching database and is not primarily about attribution, however I can only suggest you read the papers referenced by this one; especially references 1 (Coral bleaching: causes and consequences) which discusses bleaching due to disease and solar irradiance, as well as thermal stress, and references 5 and 6 which do indeed discuss attribution of bleaching to anthropogenic warming.

Um, the pH scale is logarithmic, with 7 being neutral. An increment of 1 in pH value corresponds to a ten-fold change in concentration of hydrogen ions (aka acidity). The observed change from pH8.2 to pH8.1 therefore indicates something like a 25% increase in acidity. This maybe small compared to the diurnal range in some locations, but it represents a substantial increase over the baseline level that has obtained for at least 800,000 years. If atmospheric CO2 concentrations increase as projected, by 2100 we will see a further 0.5 point rise in pH, an increase in of 150% - to levels not seen for at least 20 million years, and at a rate of change almost certainly unprecedented and effectively irreversible for thousands of years. This has serious implications for corals and other calcifying marine organisms that require seawater supersaturated with respect to calcium carbonate minerals. Studies have found that a doubling of CO2 produces a decrease in calcification of 11-40% depending on species, making the reefs less able to cope with the other stresses they are encountering.

As the Royal Society has been warning for over a decade.

Effect of elevated CO2 on the community metabolism of an experimental coral reef

Any slight change of temperatures, well within any natural variability, especially as we are basing our observations in a time of relative cold (the little ice age), while it might hurt a few of the more sensitive organisms, it will really be as nothing to the reef.

Trouble is, an El Nino can add several degrees to sea temperatures, when this occurs on top of a gradual warming trend, it pushes corals well out of their thermal tolerance range, each event causing progressively more damage.

Two-thirds of the corals in the northern part of the Great Barrier Reef have died in the reef’s worst-ever bleaching event, according to our latest underwater surveys.

On some reefs in the north, nearly all the corals have died. However the impact of bleaching eases as we move south, and reefs in the central and southern regions (around Cairns and Townsville and southwards) were much less affected, and are now recovering.

In 2015 and 2016, the hottest years on record, we have witnessed at first hand the threat posed by human-caused climate change to the world’s coral reefs.

Heat stress from record high summer temperatures damages the microscopic algae (zooxanthellae) that live in the tissues of corals, turning them white.
After they bleach, these stressed corals either slowly regain their zooxanthellae and colour as temperatures cool off, or else they die.

The Great Barrier Reef bleached severely for the first time in 1998, then in 2002, and now again in 2016. This year’s event was more extreme than the two previous mass bleachings.

http://theconversation.com/how-much-coral-has-died-in-the-great-barrier-reefs-worst-bleaching-event-69494

It doesn't matter how beautiful your theory is, it doesn't matter how smart you are. If it doesn't agree with experiment, it's wrong.

Richard Feynman

https://www.newscientist.com/article/dn28468-growing-corals-turn-water-more-acidic-without-suffering-damage/

Also less than 7 is acidic. More than 7 is alkaline. Something that is alkaline cannot be more or less acidic.

On the other hand —

"When I use a word," Humpty Dumpty said, in rather a scornful tone, "it means just what I choose it to mean- neither more nor less."
"The question is," said Alice, "whether you can make words mean so many different things."
"The question is," said Humpty Dumpty, "which is to be master-that's all."

The obfuscation mendacity of the average eco-warrior no longer amazes me!

Ditto the ability of contrarians to make irrelevant linguistic nitpicks while ignoring the damage already observed from warmer seas and more acidic , sorry, less alkaline waters.

Funny, even the article you linked to talks of 'more acidic' waters, heck even wikipedia knows that in this context the word means reduced pH.

Ocean acidification is the ongoing decrease in the pH of the Earth's oceans, caused by the uptake of carbon dioxide (CO2) from the atmosphere.[2]Seawater is slightly basic (meaning pH > 7), and ocean acidification involves a shift towards pH-neutral conditions rather than a transition to acidic conditions (pH < 7). An estimated 30–40% of the carbon dioxide from human activity released into the atmosphere dissolves into oceans, rivers and lakes. To achieve chemical equilibrium, some of it reacts with the water to form carbonic acid. Some of the resulting carbonic acid molecules dissociate into a bicarbonate ion and a hydrogen ion, thus increasing ocean acidity (H+ ion concentration). Between 1751 and 1996, surface ocean pH is estimated to have decreased from approximately 8.25 to 8.14, representing an increase of almost 30% in H+ ion concentration in the world's oceans

From <https://en.wikipedia.org/wiki/Ocean_acidification>

As I indicated earlier, for over a decade those scientific illiterates at the Royal Society have been perfectly comfortable with the term.

The oceans are absorbing carbon dioxide (CO2) from the atmosphere and this is causing chemical changes by making them more acidic (that is, decreasing the pH of the oceans).

https://royalsociety.org/~/media/Royal_Society_Content/policy/publications/2005/9634.pdf

Following the links from the NS article I discover that

That’s not to say coral reefs are safe. From the Caribbean to the Indian Ocean, human activities are taking their toll. But if we take the right steps now, they might just see out the end of the century.

Very reassuring. It is almost as if you're just making noise in an attempt to distract from the problem...

There is no pH problem, Phil Clarke. There are many reasons for this. Too many to recount here without an overly-long post.

The best analogy I can think of at the moment is actually the 'Polar Bear problem'. They may live in a region that might have, say, an annual average temperature of -20.0 degrees Celsius (imagine another number if you wish). It gets a lot colder in winter, and warmer in summer. If the annual average rises to -19.9 degrees Celsius it changes almost nothing. They are still warm-blooded mammals living in a cold environment. Yet they can also live comfortably if you move them to London Zoo. They may actually live better and need less food there, everything else being equal. Of course nothing ever is equal, but those studies haven't been done because they are too expensive and take too long.

Now, back to pH. Most of creation, including the animals of the sea, have an internal pH which is much more acidic than the oceans and most of the natural environment. Yet it is not a problem. Simple rainfall is usually about a 1000 times more acidic than seawater, but you don't notice your eyes watering, do you? How about I change that to %? OK, simple rainfall is usually about a 100000% more acidic than seawater, but you don't notice your eyes watering, do you? Such small pH changes as proposed, but certainly not proven, for the oceans are smaller than biochemists would normally concern themselves with in the lab. In most cases (not all) they simply wouldn't believe that they could extract useful information above statistical noise. (And no, I won't buy someone reporting a one-off "simulated-ocean" experiment where they didn't even have a control fish-tank. Biologists/biochemists do multiple repeat experiments in 96-well plates for good reasons: Biology is horrifically un-reproducible.)

A competent and honest biochemist will tell you that pH variations within these limits is usually utterly meaningless. You said so yourself when you noted that daily variations are much larger. And, as you correctly note, pH is a log scale. Such small environmental changes mean little. As meaningless as raising the temperature of the Polar Bear's environment by a fraction of a degree. And if it has any effect at all, it may well be beneficial. Also, just because the polar bear is adapted to cold environments, it doesn't mean that such cold environments are necessarily optimal for such warm blooded mammals. So it is with pH and most life forms.

Even many of the oceanographic pH alarmists quietly admit this and don't carp on about pH problems for most life forms. They concentrate on things where it might possibly have an effect, such as the ability of calcifying organisms to spread and re-populate if the Aragonite super-saturation were to drop in seawater. But once again this oversimplifies: Many calcifying organisms thrive in waters where higher pH and lower calcium means that Aragonite is not supersaturated. This is because, once again, many organisms are able to control their own local environment above and beyond any small changes in their 'global' environment. But not all. I'm sure there will be at least one that suffers, even if a hundred others benefit.

Biologists/biochemists routinely grow single-cell populations of diverse lifeforms in the laboratory, and they frequently do it in an artificial atmosphere of 40000 ppm CO2, not 400 ppm. This is because life generally likes it that way.
Biochemists know that modestly increased levels of CO2 causes no problems in the short term.
Geologists look back in time at the White Cliffs of Dover and know that much, much, higher levels of CO2 caused no problems in the long term.
But somehow, global warmers come to the conclusion that modestly increased levels of CO2 will cause severe problems in the medium term? I don't think so. Both the extravagantly raised future levels of atmospheric/oceanic CO2, and its extravagant effects remain "postulated". That is "imagined" in normal language.

Nice comforting theory Michael. But not supported by observation.

Variability of pH in coastal waters is considerably larger than that in the open ocean, partly driven by upwelling (17), freshwater input (18), eutrophication (19) and biogeochemical processes (20). Anthropogenic trends in biogeochemical variables— notably in pH, PCO2, and the saturation of calcite and aragonite—emerge from the noise of natural variability much faster than sea surface temperature (SST). The combined changes in these parameters will be distinguishable from natural fluctuations in 41% of the global ocean within a decade

Contrasting futures for ocean and society from different anthropogenic CO2 emissions scenarios

By the middle of the next century (now this century), an increased concentration of carbon dioxide will decrease the aragonite saturation state in the tropics by 30 percent and biogenic aragonite precipitation by 14 to 30 percent. Coral reefs are particularly threatened, because reef-building organisms secrete metastable forms of CaCO3, but the biogeochemical consequences on other calcifying marine ecosystems may be equally severe.

Geochemical Consequences of Increased Atmospheric Carbon Dioxide on Coral Reefs

We found that there were consistent and reproducible changes in the rate of calcification in response to our manipulations of the saturation state. We show that the net community calcification rate responds to manipulations in the concentrations of both Ca2+ and [CO3]2- and that the rate is well described as a linear function of the ion concentration product, [Ca2+]0.69[[CO3]2-]. This suggests that saturation state or a closely related quantity is a primary environmental factor that influences calcification on coral reefs at the ecosystem level. We compare the sensitivity of calcification to short-term (days) and long-term (months to years) changes in saturation state and found that the response was not significantly different. This indicates that coral reef organisms do not seem to be able to acclimate to changing saturation state. The predicted decrease in coral reef calcification between the years 1880 and 2065 A.D. based on our long-term results is 40%. Previous small-scale, short-term organismal studies predicted a calcification reduction of 14-30%. This much longer, community-scale study suggests that the impact on coral reefs may be greater than previously suspected. In the next century coral reefs will be less able to cope with rising sea level and other anthropogenic stresses.

Seawater carbonate chemistry and processes during an experiment with coral reef

This was not just a tank in a lab, this was the 2650 square metres of coral at the BIOSPHERE-2 facility, observed over nearly 4 years. 

using the average emission scenario (IS92a) of the Intergovernmental Panel on Climate Change, we predict that the calcification rate of scleractinian-dominated communities may decrease by 21% between the pre-industrial period (year 1880) and the time at which pCO2 will double (year 2065).

Seawater carbonate chemistry and calcification during experiments with coral communities

Seawater acidification decreased coral calcification by ca. 0.1-mg CaCO3 g−1 d−1 for a decrease of 0.1 pH units.

Coral calcification responds to seawater acidification: a working hypothesis towards a physiological mechanism

From the glacial experimental conditions (Ω = 5.05, pCO2 = 186) to those of the future (Ω = 2.25, pCO2 = 641), calcification dropped by 30%; from present day conditions (Ω = 3.64, pCO2 = 336) to those of the future, calcification dropped by 11%. This decrease in calcification rate occurred at all light levels, indicating that rising CO2 will impact corals living at all depths.

Dependence of calcification on light and carbonate ion concentration for the hermatypic coral Porites compressa

Georgiou et al 2015 provided a glimmer of hope when they found that the Porites genus of coral can regulate the pH in its immediate environment, increasing its resistance to acidifying waters, however the authors note this was a genus known to be resiliant to high CO2, the results are not applicable to all other genii and it is not known how sensitive this ability is to increasing temperature.

I find these studies a tad more credible than your Polyanna thesis.

Phil Clarke. Browsing through the recent posts on this thread I found you're still at it, spreading disinformation about marine calcification. You and I debated this matter ages ago until you left the stage. How can you have forgotten? Do you remember nothing about corals and other marine calcifiers using bicarbonate, not carbonate, that with organisms that photosynthsize (or consort with photosynthesizers) the liberated proton is used to boost this process, that bicarbonate increases as pH decreases, boosting both calcification and food production, that calcification has been shown to increase skeletal production or organism size when CO2 dissolves in seawater? No? Much of what is written about the topic is utter, utter rubbish! What you are writing is repeated garbage.

Yeah, peer-reviewed misinformation from the Royal Society amongst others. You share the credibility problem, my friend.

Phil Clarke. That's it??? That's all you have? Scuttling out the door into the bowels of the infallible Royal Society, as last time. Beneath contempt.

I thought Climate Science had given up, and switched from Ocean Acidification to Ocean Plasticification. The sustainability of funding is more durable than the theories at the moment.