Coral reef bleaching with world-renowned expert Terry Hughes - and a Gish Gallop from "science" quack, Jim Steele

Bleached staghorn coral
on the Great Barrier Reef
between Townsville and Cairns, March 2017,
Credit: Bette Willis, Source: JCU

Some years ago I visited the Great Barrier Reef offshore from the resort town of Port Douglas. It was a magical experience (and I think the only time I've scuba dived in the ocean). Later I had the privilege of swimming over part of the Great Barrier Reef again from the seas around the Whitsundays, staying at Airlie Beach. Apart from some snorkelling over coral reefs in a few other places, such as Bali, and doing some work with the fishing industry, I know very little about coral reefs. Any knowledge I do have is thanks to experts.

What I do know is that coral reefs are extremely critical ecosystems for maintaining marine life and protecting coastal environments, and for all sorts of human activities too, such as fishing, tourism and more.

I also know that our actions are killing many corals and even entire reefs.

Although I've written about them in the past, I'm reluctant to delve too deeply into a topic as complex and specialised as coral reefs for risk of giving wrong information. However the sort of nonsense that you read by deniers and disinformers, who seem to want to kill the reefs off as quickly as possible, has prompted me again. That plus the fact that governments in Australia (the Australian Government and the Queensland Government), a suspect coal company from India, and less prominent players are doing all they can to speed up the death of the Great Barrier Reef by giving our hard earned money, plus permits, for Adani to mine coal and wreck the reef (and use up our precious water).

On top of all that, the Great Barrier Reef is suffering another bleaching event this year, hot on the heels of the worst mass bleaching ever that happened last year.

What finally got me going was an article at WUWT by Jim Steele, in which he tried to tell his readers that the 2016 coral bleaching wasn't really widespread (it was the worst ever), and was caused by any of a whole number of different reasons he offered up, except the real cause - excessive ocean heat. Jim Steele's a global warming denier, in case you've not heard of him.

See update below, too.

Because of all this, I've read more and made contact with a couple of experts and this article is the result. All errors are mine - so if you see some, let me know and I'll correct them.

We are the biggest threat to coral reefs

The biggest threat to coral reefs is us. People. Human activity.

The causes of the present-day demise of coral reefs are varied. One of the biggest causes is global warming. This is having both direct and indirect effects on coral reefs.

Coral bleaching

Mass bleaching is causing huge damage to coral reefs around the world. There was a recent paper in Nature by Professor Terry Hughes and a team of scientists. Corals are marine animals that have a symbiotic relationship with particular algae. They rely on each other to live. The authors of the paper explained how heat stress disrupts this symbiotic relationship and this is evident when corals lose their colour - hence the term "bleaching". The authors wrote:

Bleached corals are physiologically damaged, and prolonged bleaching often leads to high levels of coral mortality.

That's it in a nutshell. Bleached corals don't necessarily die. They are sick, and sometimes recover. Depending on the severity of an event, or how often it's repeated, and other factors, corals and coral reefs can die - or they may recover.

Other factors affecting corals

Corals can be damaged and die from causes other than bleaching. There was a paper recently in Biogeosciences that was about how a drop in sea level caused mortality in shallow coral reefs in Bunaken Island in North Sulawesi. That is, not bleaching but death. The authors stated (my emphasis and paras):

This study reports coral mortality in Indonesia after an El Niño-induced sea level fall. The fact that sea level fall, or extremely low tides, induces coral mortality is not new, but this study demonstrates that through rapid sea level fall, the 2015–2016 El Niño has impacted Indonesian shallow coral reefs well before high sea surface temperature could trigger any coral bleaching. Sea level fall appears as a major mortality factor for Bunaken Island in North Sulawesi, and altimetry suggests similar impact throughout Indonesia.

Our findings confirm that El Niño impacts are multiple and the different processes need to be understood for an accurate diagnostic of the vulnerability of Indonesian coral reefs to climate disturbances. This study also illustrates how to monitor local sea level to interpret changes in a particular coastal location.

The authors of the Indonesian study point to a range of factors that can adversely affect corals. In addition to a rapid fall in sea level, the authors list things corals can be seriously damaged by (I've added more information in italics):

• coral bleaching through thermal stress
• diseases - this term can cover a large range such as toxins etc, not just microbes
• predator outbreaks, such as the crown of thorns starfish
• storms, which harm but can also help - e.g. Winston saved the southern GBR last year. The current bleaching might not have been as bad if Debbie had arrived sooner
• sea level rise, when it rises more quickly than a reef build up, etc.

Terry Hughes' on coral reefs TedTalk

In the talk below, Terry Hughes talks about the damage to reefs and yet how he retains some optimism that we can save the world's coral reefs. He also describes the research that he reported in his Nature paper. It's less than 15 minutes long. If you've time and even if you're short of time, it's well worth watching.

Note how Professor Hughes distinguishes between the time needed for different corals to recover, and the risk of more bleaching events preventing some from being able to do so. (about 10 minutes in). "If you lose a 100 year old coral, you cannot replace it in a few years."

The pseudo-science nonsense from climate disinformer, Jim Steele

You may have come across Jim Steele before. He's a wannabe scientist who has never published any scientific research papers as far as I can tell. He's retired now, I believe, after working part-time as a manager of a field station for a college in California, where he organised nature walks or something. These days he spends his time writing disinformation for WUWT so he can promote his vanity-published denier book, and conducting personal vendettas on a small number of individual scientists.  He's seems to be very jealous of their success, and just as clearly is a scientific ignoramus with a history of blatant lying.

This week Anthony Watts, who runs a climate conspiracy blog WUWT, chose to publish another article by Jim Steele (archived here). In this one Jim did his usual misrepresentation of science, mixed with his denial of global warming.

Remember how the second paper I referred above to was about mortality (not bleaching) from sea level fall? Well, Jim Steele started off badly, with a headline "Falling Sea Level: The Critical Factor in 2016 Great Barrier Reef Bleaching!". Jim wrote:

In contrast in Coral Mortality Induced by the 2015–2016 El-Niño in Indonesia: The Effect Of Rapid Sea Level Fall by Ampou 2017, Indonesian biologists had reported that a drop in sea level had bleached the upper 15 cm of the reefs before temperatures had reached NOAA’ Coral Reef Watch’s bleaching thresholds.

The paper he referred to is about coral mortality on a reef shelf from a sudden drop in sea level. The authors didn't mention the word "bleaching" except in references to mass bleaching events from marine heat stress. As the authors state in the abstract, the rapid fall in sea level resulted in substantial death of the corals "likely by higher daily aerial exposure, at least during low tide period".  

Still on page one of the paper, the authors wrote about what happens when corals are heat stressed. The symbiosis between the coral and the algae is disrupted and the coral turns white:

El Niño increases temperature in several coral reef regions and induces zooxanthellae expulsion from the coral polyp, resulting in a coral colony looking white, hence “bleaching”. If the situation persists the coral colony eventually dies.

…Thus, it is assumed that coral bleaching induced by ocean warming will be the main culprit if post-El Niño surveys report coral mortalities.

Jim didn't mention that part of the paper. How could he have missed it?

What the authors were focused on in their research was what happened in the lead up to the severe El Nino temperatures of 2016 (but before the hottest temperatures). They attributed the coral deaths to a severe drop in sea level. Below is Figure 1. from Ampou17, which shows pictures of the coral on Bukanen reef before and after this extreme drop.

Figure 1 | Bunaken reef flats. (a) Close-up of one Heliopora coerula colony with clear tissue mortality on the upper part of the colonies; (b) same for a Porites lutea colony; (c) reef flat Porites colonies observed at low spring tide in May 2014. Even partially above water a few hours per month in similar conditions, the entire colonies were alive. (d) A living Heliopora coerula (blue coral) community in 2015 in a keep-up position relative to mean low sea level, with almost all the space occupied by corals. In that case, a 15 cm sea level fall will impact most of the reef flat. (e–h) Before–after comparison of coral status for colonies visible in (c). In (e), healthy Porites lutea (yellow and pink massive corals) reef flat colonies in May 2014, observed at low spring tide. The upper part of colonies is above water, yet healthy; (f) same colonies in February 2016. The white lines visualize tissue mortality limit. Large Porites colonies (P1, P2) at low tide levels in 2014 are affected, while lower colonies (P3) are not. (g) P1 colony in 2014. (h) Viewed from another angle, the P1 colony in February 2016. (i) Reef flat community with scattered Heliopora colonies in February 2016, with tissue mortality and algal turf overgrowth. 

Source: Ampou17

Other causes of coral damage and death

As you can see from the above, in particular regions different factors can cause coral reef damage. At the very local level, bleaching response and coral mortality can be from various causes. For example, in a short article in Coral Reefs (2006), Leggat et al described coral mortality in a section of the Great Barrier Reef on Heron Island, back in 2005. They said how it was probably caused by high winds combined with aerial exposure, noting that the maximum water temperatures at the time were not sufficient by themselves to cause bleaching. Corals on the eastern side weren't affected. The authors wrote:

Although solar radiation cannot be ruled out in the present case, the direction of the bleaching (west-north-west) is more consistent with the observed wind direction, rather than the sun azimuth (west-south-west) during the preceding low-tide periods. It appears that the stress of high winds and aerial exposure, possibly together with the sub-bleaching water temperature, prompted the observed bleaching pattern.

Interestingly, that article, about how wind and aerial exposure probably led to bleaching, was co-authored by another coral expert, Ove Hoegh-Guldberg, who Jim Steele had added to his list of personal vendettees. 

More on mass bleaching from marine heat stress

However, when you come across mass bleaching over the vast extent seen in the 2015/16 El Nino, it's much more likely to be from the obvious cause - very high ocean temperatures.

Compare these charts from Figure 1 of Hughes17, which show the differences in the reefs affected by coral bleaching in 1998, 2002 and 2016.

Figure 2 | The footprint of bleaching on the Great Barrier Reef in 1998, 2002 and 2016, measured by extensive aerial   surveys: dark green (<  1% of corals bleached), light green (1–10%), yellow   (10–30%), orange (30–60%), red (>  60%). The number of reefs surveyed   in each year was 638 (1998), 631 (2002), and 1,156 (2016). Source: Hughes17

Compare Figure 2 above with the spatial pattern of temperature stress, recorded as degree heating weeks (DHW). As you can see, in each bleaching event (1998, 2002 and 2016), the greatest coral damage was where there was the greatest heat stress.

Figure 3 | Spatial pattern of heat stress (DHWs; °C-weeks) during each mass-bleaching event. Dark blue indicates 0 DHW, and red is the maximum DHW for each year (7, 10 and 16, respectively). Orange and yellow indicate intermediate levels of heat exposure on a continuous scale. Source: Hughes17

Huge increase in Degree Heating Weeks

Degree Heating Weeks (DHW) are a bit complicated. The concept is best described in some detail in Liu et al (2003) in EOS. What DHW shows is how much heat stress has accumulated in an area. It is measured as HotSpot anomalies, which are departures from the "climatological mean temperature of the climatological hottest month". That means it is region specific, though it's not like a normal sea surface temperature anomaly (which uses a different mean as a baseline). Essentially it is an indicator of the departure from the bleaching temperature threshold for coral reefs. The bigger the departure and the longer the duration the greater the risk of severe damage to the coral. From Liu03:

Field observations (most of which are subjective measurements presented as informal reports) with coincident satellite data are only available for a limited number of years; these observations indicate that there is a correlation with bleached corals when DHW values of 4.0 have been reached. By the time DHW values reach 8.0, widespread bleaching is likely and some mortality can be expected.

Have a look at the charts below, from Hughes17, showing DHW for each of the three bleaching events. In 2002 there were a lot of reefs where DHW values were greater than 8.0. In 2016 there were many more:

Figure 4 | Frequency distribution of maximum DHWs on the Great Barrier Reef, in 1998, 2002 and 2016. White bars indicate 0–4 °C-weeks; grey bars, 4–8 °C-weeks; black bars, >8 °C-weeks. Source: Hughes17

Jim Steele and his pseudo-science Gish gallop

If you are a discerning reader, you'll immediately see that Jim Steele's article at WUWT is suspect. He spends time trying to discredit some experts and misrepresents or cherry-picks from others. He gives no solid evidence for his claim that falling sea levels were responsible for bleaching over the entirety of the bleached areas in 2016 (or at any time). (This is an area the size of Italy that we're talking about, not a lone reef on the edge of a small tropical island.) He hits his readers with every notion he can think of as an alternative to the actual cause of the mass coral bleachings described in Hughes17.

Aerial and underwater surveys

Hughes17 is based on data collected from extensive aerial and underwater surveys. Jim Steele implies that the researchers of Hughes17 relied only on aerial surveys, ignoring the fact that the scientists assessed the accuracy of the scores applied from the aerial surveys by ground-truthing. As the authors wrote:

To ground-truth the accuracy of aerial scores of bleaching on the Great Barrier Reef (Fig. 1a), we conducted in-water surveys on 104 reefs during March and April 2016 (Extended Data Fig. 5).  We also measured differential species responses (winners versus losers; Fig. 4) on 83 reefs, spanning the 1,200-km-long central and northern Great Barrier Reef, from 10–19° S. We surveyed two sites per reef, using five 10 × 1 m belt transects placed on the reef crest at a depth of 2 m at each site. Observers identified and counted each coral colony and recorded a categorical bleaching score for each individual: 1, no bleaching; 2, pale; 3, 1–50% bleached; 4, 51–99% bleached; 5, 100% bleached; 6, bleached and recently dead. The site-level amount of bleaching for each taxon in Fig. 4 is the sum of categories 2–5. The number of colonies assessed was  58,414. A similar standardized protocol was used to measure amounts of bleaching for the Coral Sea, on sub-tropical reefs south of the Great Barrier Reef, and across 18° of latitude along the west coast of Australia (Fig. 1g).

If only disinformers were as particular.

Anything but hot water

When Jim wrote the following Gish gallop of suggestions, he shows no logic, and wants the bleaching (that he doesn't believe in) to be anything but hot water. He wrote:

Aerial surveys, on which Hughes 2017 based their analyses, cannot discriminate between the various causes of bleaching. To determine the cause of coral mortality, careful examination of bleached coral by divers is required to distinguish whether bleached coral were the result of storms, crown-of-thorns attacks, disease, aerial exposure during low tides, or anomalously warmer ocean waters. 

Is he really suggesting that all these different events came to pass at exactly the same time as the excessively hot waters, and that it was the above events, not hot water, that caused the massive bleaching, covering umpteen thousand square kilometres of reef?

Unlike the researchers, Jim provides not a jot or hint that he has any evidence to support his implied claim, apart from showing a chart of sea level in one single spot off the coast of northern Queenland, Lizard Island, which only goes, with gaps, from 1960 to the end of 2015. (Here's a blog article from March 2016 from the Lizard Island Research Centre, about the coral bleaching there.) Jim's chart doesn't show that the 2015 sea level was any lower than it's been in the past, when there was no bleaching.

I did ask Terry Hughes about this, and his response, in part, was:

We also showed that the amount of bleaching measured below water ranged from 0-100%, and was tightly correlated with DHW (Figure 3). If sea level was responsible why didn’t cooler reefs also bleach? We found bleaching down to 40m which can’t be explained by any tidal anomaly.

Below is the Figure 3 that Dr Hughes mentioned, showing the relationship between heat exposure and bleaching in March/April 2016:

Figure 5 | The relationship between heat exposure (satellite-based DHWs in 2016) and the amount of bleaching measured underwater (per cent of corals bleached) in March/April. Each data point represents an individual reef (n = 69). The fitted line is y = 48.6ln(x) – 21.6, R² = 0.545.
Source: Hughes17

It's not just the correlation of bleaching and DHW, I expect most of you will have picked up this next point, too. In the study that Jim Steele looked at in which aerial exposure caused coral mortality, the coral at depth wasn't harmed. Jim Steele even noted that in his article. (In fact, the scientists unsurprisingly reported that many corals in that region are often exposed to the air without harm. It was the extent of exposure that made the difference in 2015.) So how can he possibly try to argue that reefs at 40 metres below the sea surface were killed by low sea level rather than the obvious culprit - excessive exposure to hot water?

Interestingly, in an article in the Guardian today, it was stated that a couple of groups have suggested to the Australian Government that cold water should be pushed onto a couple of reefs to protect them from coral bleaching. Most experts didn't much like the idea for various reasons, but it does mean that people accept the evidence that bleaching is caused by excessively warm water.

It's El Nino - good for Jim - he's partly right

After trying that hotch potch of notions, Jim shifted to El Nino as the cause. He's correct to a point. However it was El Nino on top of global warming. There have been El Ninos for centuries and it's only in recent times that they've heated up the oceans so much that they've caused mass bleaching. The other point is that there is no El Nino right now, yet the Great Barrier Reef is suffering another hit of coral bleaching this year, 2017.

Global scale or "patchy"?

Later in his article, Jim wrote:

Hughes 2017 wanted to emphasize GBR bleaching as a “global-scale event” in keeping with his greenhouse gas/global warming attribution, but bleaching and mortality was patchy on both local and regional scales. 

He's not serious, is he? The 2016 mass bleaching was the worst ever. Perhaps by "patchy" Jim meant that there were some reefs somewhere in the tropics that escaped mass bleaching.

The authors of Hughes17 reported that in 2016, the proportion of extreme bleaching in the Great Barrier Reef (more than 60% of corals bleached) was four times higher that the mass bleachings of 1998 and 2002. They wrote that in 2016:

...only 8.9% of 1,156 surveyed reefs escaped with no bleaching, compared to 42.4% of 631 reefs in 2002 and 44.7% of 638 in 1998. The cumulative, combined footprint of all three major bleaching events now covers almost the entire Great Barrier Reef Marine Park, with the exception of southern, offshore reefs (Fig. 1d).

Jim added this next bit, which was him practicing deception or lack of comprehension:

The lack of mortality in 2016 across the southern and Central GBR, was explained as a result of the cooling effects of tropical storm Winston, but that does not explain why individual reefs in those regions have not bleached at all, while others bleached only once, and still others bleached twice or three times since 1998. 

Jim should have looked at Figure 1 in the paper, which illustrates how heat stress affected different areas of the Great Barrier Reef at different times (see Figures 2, 3 and 4 above, especially Figure 3 that shows the lack of heat stress in the southern portion in 2016).

Cherry-picking and more

There's more. After arguing that mass bleaching probably isn't getting worse because of hotter seas as the world warms, Jim cites different studies, but ignores the parts where the authors talk about mass bleaching from heat stress. One of these is Wooldridge13, where the author is explaining the mechanism that causes mass coral bleaching, would you believe. Jim should take note of the last sentence in Wooldridge13, which is (my emphasis):

Future testing and refinement of the ideas presented within this paper thus offers considerable hope for developing further insights into tack[l]ing the climate-induced demise of coral-algae symbioses and the reefs they construct.

Jim's Gish gallop continues into how it's not just sea level, crown of thorns, storms, disease, low tides - he next tosses into his mix of distractions high nutrient loading that caused the mass bleaching that Jim thinks didn't happen anyway. Sure - as Terry Hughes said in the video above, replacing bad water with good water will help, and all these these things affect coral, but they didn't all happen everywhere all over the tropics, in the same short time interval, just when the oceans happen to be excessively hot, and not at any other time. It's the heat stress that clearly caused the coral bleaching in the periods described in Hughes17.

Jim's real message - denying global warming

I won't bother with the rest of Jim's article, except this bit where he shows his underlying rejection of climate science, if not his motivation for rejecting science and the knowledge of experts. He wrote:

After perusing Hughes 2017, it was clear they had been led to incorrectly embrace the prevailing bias of CO2-induced catastrophic bleaching because they failed to address the fall in sea level before and during the 2016 El Niño, and likewise they failed to address how weather created by El Niños promotes clear skies and increased solar heating. 

I dare any normal sane person (i.e. not a hard-core conspiracy theorising climate "hoax" crank) to read Hughes17 and not be convinced that mass bleaching is the result of excessive ocean heat, and that it is causing real and already has probably caused irrevocable damage to one of Australia's most precious resources.

I dare the same people to read Jim Steele's article and not be amazed at the red herrings, snide insinuations, pseudo-scientific crap, misdirection, misrepresentation, cherry-picking, and disinformation he's managed to cram into a single article. It is quite a challenge to wade through his diatribes and I don't recommend it. Jim is getting more practiced at diluting some good science with loads of pseudo-science, while rejecting the elephant in the room.

Weeping for a lost reef

Jim Steele claims he wept, which I expect is a snarky reference to a tweet by Terry Hughes, lead author of the Nature paper that Jim tried to trash:

I showed the results of aerial surveys of #bleaching on the #GreatBarrierReef to my students, And then we wept. pic.twitter.com/bry5cMmzdn

— Terry Hughes (@ProfTerryHughes) April 19, 2016

Jim Steele isn't weeping. He is doing his utmost to kill coral reefs as quickly as he and his anti-environmental vandals can.

The experts in coral reef science are doing their best to save it. Unfortunately, as Terry Hughes said: "Now, tragically, the GBR is severely bleaching again in 2017 in regions that got too hot."

As a final note, the prestigious general science journal Nature included Professor Terry Hughes, as one of the top ten people who mattered in 2016. (I didn't see Jim Steele's name in the list.)

Update - an ethical issue

I've just been made aware that the Townsville Bulletin has unbelievably presented the crank denier nonsense of Jim Steele as being as credible, or more so, than rigorous science from the foremost coral experts in the world. So I've decided to add some from the email from one of the authors of Ampou17, whose work the Townsville Bulletin mentioned, hoping he doesn't mind.

I suggested: Your paper does not refute the work that has shown that excessive warmth of some duration can cause coral bleaching.

Response: Of course not. Bleaching is caused primarily by excess temperature.

And more:

...we never contradict that bleaching can be caused by warming. It's silly to pretend otherwise.

...if someone is manipulating and transforming the content of paper to push his ideas, that's an ethical issue. I can just condemn this.

From the WUWT comments

Climate conspiracy wackos at WUWT only like articles that reassure them that the world isn't really warming. They don't care much about nature, and some despise it. The "thoughts" show no-one capable of critical thinking. None of them saw that Jim was jumping all over from one excuse to another trying to find a cause for mass bleaching that didn't involve heat. Nor that he dismissed the mass bleaching as pretty well inconsequential. If these people had their way there'd be no coral reefs at all.

jfpittman falls hook line and sinker for Jim's fib about Terry Hughes, nutrients and coral reefs, which I'm sure will cause Jim Steele some sadistic pleasure. See the video in the article above, when Dr Hughes talks about the bad things that people do to coral reefs reefs around the world. The very first item that he mentions is pollution, run-off from nutrients etc.  (see it on YouTube at 1m38s). Disinformers are shameless. Their fans are stupid, gullible or disinformers pretending to be gullible - or maybe a combination of all three.

April 5, 2017 at 7:03 am
I used to read Nature when it was the publication likely to have analysis like Jim’s.It seems so strange to see the work on eutrophication and its impact on biomes discarded. It took a lot of effort to get governments around the world to recognize that improper discharge of waste could harm species diversification, and change the fundamental relationships in the ecological microsystems. Assuming, and by that assumption throwing away so much hard won science by a scientist, seems so much worse than anything a non scientist can do from ignorance or purposeful stubbornness.

Greg doesn't understand that Centres of Excellence in Australia is the collective name given to collaborative efforts involving scientists from multiple organisations, working in a particular field. Or maybe, like everyone at WUWT, he just hates knowledge.

April 5, 2017 at 9:04 am
” the ARC Centre of Excellence for Coral Reef Studies”
Yet another of these bullshit “Centres of Excellence”. Who are they trying to con ? If you were a centre of excellence you would not need to put it on the letter head. Do Yale and Harvard have to put “excellence” in their names? No, because they ARE centres of excellence not bullshit merchants trying to dress politics as science.

Peter Ridd is a known disinformer from JCU (remember Bob Carter, the devil rest his soul?), who is a mate of Jennifer Marohasey and belongs to a denier/disinfomer club. He is an unethical one at that, claiming that random un-named tourism operators, who have a vested interest, are more trustworthy than methodical, rigorous, scientific research from his much more highly esteemed professional colleague.

April 5, 2017 at 4:20 pm
Jim,
you may be interested that there was a mass mortality of mangroves in the Gulf of Carpentaria last year also caused in part by a temporary drop in sea level associated with El Nino. It was a huge event. see link below or I can send you the original paper.
I should add that I have looked at many of the videos of the bleaching taken from aircraft and it is difficult to see how the figures that Hughes presents are credible. In addition a parallel survey of GBR bleaching done by tourist operators indicated far lower levels than reported by Hughes team.
It looks like another example of results we cannot trust.
Peter Ridd
James Cook University

(Peter Ridd linked to an article at The Conversation, which was based on research published by CSIRO. Low sea level was considered a likely a factor with the mangrove die-off, but so was unprecedented high temperature and severe drought. Global warming again!)

DaveR is unable to read critically. He mistakenly thinks that Jim's multiple excuses to avoid ocean warming and mass bleaching are "hypothesis" based on data. They aren't. There is no meaningful data from Jim. It's just a Gish gallop of the type you see every day on denier blogs.

April 5, 2017 at 6:20 pm
Its always refreshing to see a scientific article which looks at the data first, and then makes hypotheses second. There is not a lot of that approach in the climate fraternity. It even more refreshing when that study explodes a dogma well past its use-by date.
On a scientific point, a 120m sea level rise in the last 20ky after the last ice age peak means that all current corals down to 120m didnt exist 20k years ago, and the shallower colonies are very young.
I have a feeling that corals dog the current sea level and live/die as MSL moves. Isotopic age studies on corals must be particularly illuminating.

Peter s says he has some sort of story he wants money for, but I don't know what it is. His next snorkelling holiday perhaps? I figure he thinks that the sun bleaches coral just like it bleaches the sheets on the clothes line. He's wrong.

April 5, 2017 at 9:11 pm
I have snorkeled out there twice and it is breathtaking as you dive down deeper. The GBR is a living thing. In ideal conditions the coral grows wider and higher until it gets close to the surface where it is exposed to the sun more often during low tide. Naturally its vivid colours will become bleached. But of course there is no funding in this sort of story.

ptolemy2 mistakenly thought that sea levels are falling. What a nutter. She or he probably thinks the world is cooling, too.

April 6, 2017 at 5:04 am
So sea level rise is levelling off and the Climagesterium is trying to conceal the fact.
This could get interesting.

The rate of rise has gone up to 3.4mm a year and despite the end of El Nino, it's still above the long term trend - from the CU Sea Level Research Group:

graphicconception expressed his thanks for all the "alternative causes", not caring that none of them were the primary cause of the mass bleachings last year or this year.  

April 6, 2017 at 5:56 am
Excellent article. Duly bookmarked.
The information I think the public needs includes the alternative causes for a particular effect. The AGW fraternity are happy to push the “warming causes everything” approach. It is only when you have an idea of the other things besides warming that can have an effect that you can counter their arguments successfully. This article provided that information. Thank you.

The rest are no better, and simply demonstrate yet again that WUWTers are not capable of understanding science,  unable to think or read critically, and willing to swallow anything they read on a denier blog as long as it pokes fun at real knowledge. And, of course, as long as it dismisses climate science as a "hoax".

References and further reading

Hughes, Terry P., James T. Kerry, Mariana Álvarez-Noriega, Jorge G. Álvarez-Romero, Kristen D. Anderson, Andrew H. Baird, Russell C. Babcock et al. "Global warming and recurrent mass bleaching of corals." Nature 543, no. 7645 (2017): 373-377. doi: 10.1038/nature21707 (pdf here)

• Large Sections of Australia’s Great Reef Are Now Dead, Scientists Find - article by Damien Cave and Justin Gillis at the New York Times, 15 March 2017
• How the Great Barrier Reef is responding to global warming. (Hint: not well) - article by Sean Greene at the Los Angeles Times, 17 March 2017
• Urgent action needed to save the reef while we still can, scientists warn - article by Gemma Chilton at Australian Geographic, March 2017
• Australia must share the blame for coral bleaching - article at the Financial Times

Eghbert Elvan Ampou, Ofri Johan, Christophe E. Menkes, Fernando Niño, Florence Birol, Sylvain Ouillon, and Serge Andréfouët. "Coral mortality induced by the 2015-2016 El-Niño in Indonesia: the effect of rapid sea level fall." Biogeosciences 14, no. 4 (2017): 817. doi:10.5194/bg-14-817-2017 (open access)

Leggat, William, Tracy D. Ainsworth, Sophie Dove, and Ove Hoegh-Guldberg. "Aerial exposure influences bleaching patterns." Coral Reefs 25, no. 3 (2006): 452-452. doi:10.1007/s00338-006-0128-3

Liu, Gang, Alan E. Strong, and William Skirving. "Remote sensing of sea surface temperatures during 2002 Barrier Reef coral bleaching." Eos, Transactions American Geophysical Union 84, no. 15 (2003): 137-141. doi: 10.1029/2003EO150001 (open access)

Global warming and repeated bouts of coral bleaching - Article by Terry Hughes in Nature Ecology and Evolution, March 2017

It’s either Adani or the Great Barrier Reef. Are we willing to fight for a wonder of the world? - article by Jeff Sparrow at The Guardian, 7 April 2017

Plan to pump cold water on to Barrier Reef to stop bleaching labelled 'band-aid' - article by Christopher Knaus at the Guardian, 7 April 2017

Importance of Coral Reefs - NOAA article with links to other general information about corals

From the HotWhopper archives

• Annual large scale coral bleaching: Eric Worrall @wattsupwiththat sez - who cares? - January 2017
• No honesty or diligence about #climate change or coral reef science from Bob Fernley-Jones at WUWT - February 2017
• The Great Barrier Reef: an unmitigated disaster - if only the Australian public knew... - June 2016
• Willis Eschenbach turns on the charm for NOAA's coral watch crew - July 2015
• Perennially Puzzled Bob Tisdale surfs the surface at Florida Keys - September 2014
• Other articles featuring Jim Steele