Remember when they told us coral bleaching was a sure result of recent man-made global warming? Never mind.

From the “science eventually self-corrects” department, new science showing coral bleaching of the Great Barrier Reef is a centuries-old problem, well before “climate change” became a buzzword and rising CO2 levels were blamed.

Marc Hendrickx writes:

New paper shows coral bleaching in GBR extending back 400+ years.

[This] busts myths promulgated by alarmist Dr. Ove Hoegh-Guldberg see for instance

“The science tells us that exceeding 2°C in average global temperature will largely exceed the thermal tolerance of corals today. It is already happening. Rolling mass bleaching events, unknown to science before 1979, are increasing in frequency and severity.”


Also see the news report from The Australian

Here is the paper: (open access)

Reconstructing Four Centuries of Temperature-Induced Coral Bleaching on the Great Barrier Reef


Mass coral bleaching events during the last 20 years have caused major concern over the future of coral reefs worldwide. Despite damage to key ecosystem engineers, little is known about bleaching frequency prior to 1979 when regular modern systematic scientific observations began on the Great Barrier Reef (GBR). To understand the longer-term relevance of current bleaching trajectories, the likelihood of future coral acclimatization and adaptation, and thus persistence of corals, records, and drivers of natural pre-industrial bleaching frequency and prevalence are needed. Here, we use linear extensions from 44 overlapping GBR coral cores to extend the observational bleaching record by reconstructing temperature-induced bleaching patterns over 381 years spanning 1620–2001. Porites spp. corals exhibited variable bleaching patterns with bleaching frequency (number of bleaching years per decade) increasing (1620–1753), decreasing (1754–1820), and increasing (1821–2001) again. Bleaching prevalence (the proportion of cores exhibiting bleaching) fell (1670–1774) before increasing by 10% since the late 1790s concurrent with positive temperature anomalies, placing recently observed increases in GBR coral bleaching into a wider context. Spatial inconsistency along with historically diverging patterns of bleaching frequency and prevalence provide queries over the capacity for holobiont (the coral host, the symbiotic microalgae and associated microorganisms) acclimatization and adaptation via bleaching, but reconstructed increases in bleaching frequency and prevalence, may suggest coral populations are reaching an upper bleaching threshold, a “tipping point” beyond which coral survival is uncertain.

This figure (especially panel B) suggests that there was bigger bleaching events in the past:

Figure 4. Massive Porites spp. bleaching frequency and prevalence. NOAA extended sea surface temperature (SST) for Great Barrier Reef (GBR) (A) from ship and buoy data (1854–2000, 11 yr moving average, red line) (Smith et al., 2008). Southern hemisphere surface temperature anomaly (ocean and land) reconstruction (Mann et al., 2008) (solid line) with the uncertainty (0.23°C) on the reconstruction indicated (the reconstruction includes coral extension rates so is not fully independent of our reconstruction). Dashed line indicates mean temperature over record length (1570–1995). Bleaching frequency (B) (number of years per decadal bin in which bleaching occurred) and prevalence (C) (% of corals bleached per decade) observed in at least 20% of coral for the GBR denoted by blue bars. Red color bars indicate years in which less than 2 (frequency)/3 (prevalence) coral cores were available; those years were excluded from further analysis (see Supplementary Material). Number of coral cores available in each decade indicated by solid black line. Dashed black line indicates breakpoint determined linear trend in bleaching and horizontal solid black lines represent breakpoint location 95%CI. For (B) decade notation marks the start of the bin for frequency and each coral core (n = 44) contributed up to 10 annual growth extensions per decadal bin.

In the discussion section they say:

Both our reconstructed and the observational GBR bleaching records show maximum bleaching during 1998 across the whole GBR (Figure 3) although this is not scaled for observational effort.

Gosh, what happened in 1998? A super El-Niño, that’s what, and that natural cycle event wasn’t caused by man. Note all the warm ocean water near Eastern Australia where the GBR is located.

The UUIC writes:

Droughts in the Western Pacific Islands and Indonesia as well as in Mexico and Central America were the early (and sometimes constant) victims of this El Niño. These locations were consistent with early season El Niños in the past. A global view of the normal climatic effects of El Niño can be seen below.

Image by: CPC ENSO Main Page

But, Dr. Ove Hoegh-Guldberg makes his living blaming man-made climate change for just about every ill associated with the GBR, so I’m pretty sure he won’t like this paper as it draws attention to the obvious: Coral bleaching of the GBR is not a new problem unique to our time-frame.



102 thoughts on “Remember when they told us coral bleaching was a sure result of recent man-made global warming? Never mind.

  1. The historical record on coral bleaching is fairly short, and this sort of paleo record gives some sort of perspective. But it almost certainly will not really affect those using bleaching as an indicator of doom.

    • The dangers of climate change are a religion not a science – don’t expect facts to matter with the coreligionists.

      • Shutting The Conversation down….’because its getting worse’

        This from the British edition of The Conversation ( Academic rigour, journalistic flair) –
        Academic rigour ???

        ” Will de Freitas

        Environment + Energy Editor, The Conversation
        In reply to Peter Campbell

        yep I’m going to delete any further “this means it’s not global warming!!” nonsense. Clearly these commenters didn’t even manage to read as far as the second half of the headline (or more likely they did but don’t care).”

        6 comments (35%) removed by moderator.
        So now only pro CAGW or CACC views are allowed; a true religion indeed.

        • Interesting article, however as mentioned it is not merely ocean temperatures which stress corals it is the presence of coastal habitation and all its attendant pollution as well as off shore activity directly at the reef.

          Gee…what could have changed along the eastern coast of Australia around the 1800’s?
          I’ll give you 3 guesses. and the first 2 don’t count.

          • This paper fails to address the elephant in the room … the GBR bleaching is coincident with strong El Nino weather events … sea levels fall, extreme low tides occur, high pressure cells get stuck over the crystal clear waters of the Coral Sea … cloudless skies, windless days and calm seas expose the reef to extended maximum UV solar radiation doses … UV reaches metres below sea surface in these conditions … the corals get sunburnt! …

    • 15000 years ago the present location of the GBR was extremely well bleached as it was many metres above sea level. Nothing to be alarmed about!

      • Yes, sea level increased by about 500 feet at the end of the last ice age. Coral survived nicely. And, of course, before that, the sea level fell that same 500 feet and yet the coral survived. The point is that coral has been around through glacials and interglacials, so any minute change in water temperature now is unlikely to have ANY discernable effect.

  2. Who is the ‘expert’ being investigated in Oz for making coral related stuff up for ‘papers’? Over years/decades? I saw mention but can’t find relevant/recent news. TIA.

  3. Some good evidence shuts down all kinds of speculation.

    This is very similar to the polar bear story. Once it is pointed out that polar bears survived warmer times, and they’re still thriving, the alarmists have to shut up.

    • I hate to say it…but this is horrible evidence…and this paper is a crock

      They tried to core porites…like tree rings…and date and growth them like tree rings.
      Corals host more than one clade of zoox…not only do zoox leave no trace…no one fully understands them
      Which zoox were the corals hosting at the time they were growing slower…or faster?
      Clade C is the most common on the GBR..but clade D preforms better at higher temps but D makes them grow slower…
      Are they marking what they think was a bleaching event because the coral was hosting C and it really was a bleaching event?….or are they marking one because the coral was swapping back to C from D and growth was slower?…the possibilities and combinations are limitless because corals can host not just one..but more than one clade at a time

      In a round about way…they admit to it…..they found incidences with “no correlation”..well, of course they did

      • “I hate to say it…but this is horrible evidence…and this paper is a crock”

        Pretty much the situation with any proxy. We really don’t know with any certainty what paleo temperatures were. Error bars are just about always larger than the purported differences between then and now.

        Dendro master Ed Cook even said as much (with some rather colorful language) in the CRU emails.

        “Without trying to prejudice this work, but also because of what I
        almost think I know to be the case, the results of this study will
        show that we can probably say a fair bit about >100 year variability was like with any certainty (i.e. we know
        with certainty that we know fuck-all).”

  4. Who’s the Australian academic who was fired for pointing out that coral bleaching wasn’t as bad as some had been claiming?

  5. “coral populations are reaching an upper bleaching threshold, a “tipping point” beyond which coral survival is uncertain”

    Somebody will put this statement alongside the IPCC projections (or are they predictions … let’s just call them “thingumabobs” for clarity). Then the wailing will begin.

    (ps If anybody from the BBC is reading this, my commission is very reasonable.)

  6. So what is the status of the GBR? NatGeo says half of it died in 2016-2017. Is it really half dead?

    Should tourists stay home?

  7. So, once again Fake News Network is out done by Fake Science Academy. The kids in “journalism” are really going to have to up their game to be in the same league as “climate scientists”! This makes Jim Acosta look like a little beeatch compared to Ove Hoegh-Guldberg. I would feel bad for them, except I am too busy laughing at them all.

    • The GBR has been suffering ever since he bumped into it in 1770. Proof – he hit it near Cooktown, just where the bleaching is the worst.

    • Shortly thereafter Australia saw far more coastal habitation and population growth. Not so much causing climate change, but a heck of a lot more environmental impact than the area had seen before.

  8. As we find so often in life smart and pretty don’t often go together. Corals are a beautiful case in point. They colonize areas where their long term viability is marginal simply because the slightly better near by ares are already occupied. Like beautiful people living in mansions of the side of unstable California hillsides.
    When the inevitable happens, the inevitable happens. I wonder if Proff. Ove Hoegh-Guldberg is beautiful, because he/she certainly isn’t very bright!

    • I suspect he feeds on colourful publications and citations, in a symbiotic relation with others who are in the game. The problem with the Great Bloody Ripoff is that the food comes from the state, directly or indirectly. When that food supply is cut off, the various life forms will all start eating each other. It won’t be a pretty sight.

    • John, or better yet…imagine coral reefs as gardens
      You have the plants that grow slowly and actually build reefs….brain corals, etc
      …then you also have the weeds, that can over grow the slower corals, smother them out and kill them….acroporas, etc…if something….bleaching events, hurricanes, etc…doesn’t kill the weeds…they take over
      What most people see as beautiful coral reefs…are the weeds

  9. “Advances in reconstructing bleaching beyond the observational record have highlighted that there may have been at least 2 mass bleaching events since the last glacial maximum which occurred ~20 kyr BP and prior to the industrial revolution (Dishon et al., 2015)”

  10. Apparently, coral bleaching isn’t a problem, period. It seems to be part of coral’s natural life cycle.

    • “It seems to be part of coral’s natural life cycle.”….

      of course it is…..over millions of years corals evolved to change their zoox…..zoox evolved into many different clades to give the corals choices…some zoox work better in the shade..some in bright light….some in cooler water…..and some in warmer water

      Here’s a perfect example of heat stress on a coral hosting more than one clade of zoox…
      The zoox down the side and towards the bottom dominated in the shady cooler parts of the coral….it bleached
      The zoox on the top are different…they dominated in the brighter sunnier warmer parts of the coral…and did not bleach
      …all the bleached part has to do is recruit the other zoox…which they’s probably clade D
      If the heat stress is short lived….it will just recruit the same old zoox it had before

      • I feel “recruit” is the wrong word here. Clade D is heat tolerant, given an increase in temperature, Clade D flourishes, while Clade C dies off. If the temperature stays elevated, Clade C cannot recover, and Clade D takes over all the areas where Clade C died off and left vacant. But when returning back to the lower temperatures, while it doesn’t instantly kill off Clade D, the lower temperature apparently favors Clade C, so after a period of time, Clade C survived better and crowded out Clade D. Or Clade D died out and left vacant spaces for Clade C to fill. Same thing, but it sounds more brutal. Now, since it’s a symbiotic relationship, the coral must have one or the other to thrive and grow, so without either I guess it dies off, too.

    • doesn’t really matter….they found no correlation…because it’s impossible with coral paleoclimatology

    • @Steven Mosher at August 17, 2018 4:28 pm that’s never held you back from making a comment.

  11. The issue of observational bias in reporting coral bleaching has been completely ignored by researchers like Ove Hoegh-Guldberg. No one was looking closely at corals until the 1960s. Here is another comment from the blinkered Guldberg indicating a lack of appreciation of the history of bleaching all too obvious to everyone else and now confirmed by the paper above. Also from The Con in 2016…

    Is coral bleaching new?
    Mass coral bleaching was first reported in the early 1980s. Before that, there were no scientific reports of corals bleaching en masse across entire reef systems and regions.

    Did scientists accidentally overlook earlier bleaching events? With a rich history of coral reef ecology going back to the 1930s at least, the idea that we could have missed one of the most visual changes to coral reefs seems implausible. It also seems odd that filmmakers such as Valerie Taylor and Jacques-Yves Cousteau could have missed filming these spectacular events.

    The first global bleaching event was recorded in 1998. In the lead-up to that event, strong El Niño conditions developed on top of already warm ocean waters in the Pacific. During the 1998 event the world lost 16% of its coral reefs.

    Must be hard when one of your long held world views comes crashing down.

    • If you think anybody around this blog is going to be excited by another non-scientific magazine blog article you cite, forget it. As an aside, a number of researchers in the last few years have gone back to sites reportedly bleached earlier and found the coral was doing just fine.

      I realized bleaching was just part of the overblown doomsday AGW scenario when I watched a greenie film on the GBR bleaching. The narration let slip that the current reef is sitting on multiple layers of fossilized reefs going back millennia. So older versions of the GBR going back millennia have been killed off only to have the next reef begin growing on the dead carcass of the last when conditions permitted. Think on that one.

      • Of course. During ice-ages the GBR is a low limestone mountain range miles inland. A new one grows every interglacial. The reason the GBR exists is that the last 8 interglacial have reached more or less the same sea-level so a big reef has had time to form there. In Florida the last interglacial had a rather higher sea-level so that reef is now the Florida Keys, and a new reef is building a few meters lower.

  12. How can reefs be at a tipping point, if there have been larger bleaching events in the past? Politispeak.

    • This Earth has no “Tipping Points™”. This Earth has been around for 4.5 billion years, greater than 80% of that time with life on it. That alone is proof enough that the Earth climate, although chaotic, is a self-correcting mechanism. Given any change, a feedback kicks in to reduce or reverse the effects of said change. If it were not so we would not be here.

  13. Seriously? The planet has been much warmer during much of the last 600 million years and the coral reefs laid down the Cliffs of Dover. Wow. Coral reefs and rain forests are the most resilient ecosystems on the planet and have been around for 600 million years, more or less. These clowns have a truly slanted view of things, mostly politically tainted it appears.

  14. It also should be pointed out that they consider natural coral bleaching, before any human influences, to be a “problem.” It’s not a problem that we can solve if it’s natural and going to happen anyhow.

  15. When you see a paper with all but one citation (1972 , chronometer) clustered so recently (unless you think the world of science started after you were born) you have to wonder, not necessarily proving, lack of homework, but could be. I never studied coral reefs, but have known some who have. There was a quite a bit of work on Bikini and other reefs soon after WWII with a great deal of that war in coral country (Battle of the Coral Sea). They survived not only that but going dry during the glacial periods. Like oil pollution you don’t hear hardly anything about how the ocean survived the war.

    If you look at Fig. 3A, it looks like there may be a plateau. Could that be clade adaptation with rising temperatures?

  16. Ffs you didn’t put the reference of the scientific paper, that’s so frustrating. We are just supposed to believe you without questions?

  17. The article does not at all debunk the scientific prognosis for the GBR (or Hoegh-Guldberg;s work)- that ocean heating presents an existential threat to coral reefs everywhere. You are cherry picking as usual.

    “post 1850 increases in bleaching frequency and prevalence suggest corals may struggle to survive in the future as conditions continue to rapidly change. Our results thus place recently observed increases in GBR coral bleaching into a wider temporal context; bleaching has been occurring on the GBR at least during the last 4 centuries, and has increased 10% in prevalence since the 1790s. Over the coming century, rapid environmental change will include multiple-stressors (Hoegh-Guldberg et al., 2007; Hofmann and Schellnhuber, 2009; Bay et al., 2017), and the increase in prevalence and frequency indicate that we may be coming to a tipping point beyond which survival in uncertain.”

    • If ocean heating presents a threat to coral reefs everywhere, why has it missed the coral reef in Eilat? This is growing despite higher temperatures, increased tourism and more pollution due to more maritime traffic at the adjoin port of Akaba?

      I am afraid that I cannot find the recent paper online but here is just one of the numerous recent reports.


      Coral reef in Eilat, the northernmost reef in the world, is growing

      In a world where coral reefs are shrinking rapidly, the coral reef in Eilat has grown thanks in part to the actions of the Ministry of Environmental Protection.

      The coral reef in the southern city Eilat, one of the world’s northernmost shallow-water reefs, is growing.

      In a world where coral reefs are shrinking rapidly, the coral reef in Eilat has grown thanks to the actions of the Ministry of Environmental Protection and the Israel Nature and National Parks Protection Authority, which minimize negative effects on the reef.

      According to Eilat’s official tourist website, the Coral Beach Nature Reserve in Eilat extends 1,200 meters under the sea off the coast of the city. The reserve is “one of the most beautiful and famous in the world due to the amazing coral reef,” the website adds.
      The Interuniversity Institute for Marine Sciences in Eilat published a report on Sunday emphasizing that protecting the reef should be at the top of any agenda to promote development in the Gulf of Eilat, in order to preserve it for future generations.

      In contrast to other reefs around the world, an annual multi-year statistical analysis showed an increase of about half a percent per year in animal concentration at the Eilat site.

  18. From the link above.
    Back in 2011 Dr. Hoegh-Guldberg said:

    At the current rate of ocean warming, we will soon exceed the critical temperature at which this happens every year, causing the Great Barrier Reef to rapidly degrade….Rolling mass bleaching events, unknown to science before 1979, are increasing in frequency and severity.

    All of which was true in 2011.

    “unknown to science” doesn’t mean it doesn’t exist. That is how science works.

    It is not the same as”
    “a new problem unique to our time-frame”

    That is a sneaky, made up strawman. No one said it was.

    “At the current rate of ocean warming, we will soon exceed the critical temperature at which this happens every year, causing the Great Barrier Reef to rapidly degrade.”

    Lets ignore this bit even though it is still true today after another serious bleaching event this recent summer.

  19. From the research paper:
    “Here we show that corals bleached pre-industrially, (surpirise, surprise) but subsequently, bleaching has intensified.”
    (My brackets)

    Here, it becomes:
    “[This] busts myths promulgated by alarmist Dr. Ove Hoegh-Guldberg…”

    Don’t let the truth get in your way will you.

  20. This is a logical fallacy – “we’ve just discovered this thing so it must be new”.
    Activist science is rife with this fallacy in many scientific fields.
    In radiation biology for instance, newly discovered molecular and genetic mechanisms of radiation damage become a “new threat” from radiation.
    Like – they didn’t happen before you discovered them?
    America didn’t exist before Columbus sighted it in 1492?

    • “we’ve just discovered this thing so it must be new”.

      Actually you have a comprehension fallacy. That is nothing like what he said (back in 2011).

  21. Referring to figure 4B above, here is my published comment to the Australian Newspaper on 16/08/2018:

    “Choosing 1850 as your starting point and then claiming that coral bleaching is increasing, is a classic case of false logic called cherry-picking. Looking at the data, I could just as easily claim that coral bleaching is controlled by the level of solar activity. There have been two periods in the last 400 years where the level of sunspot activity on the Sun has dramatically decreased. They are the Maunder minimum and the Dalton minimum. Both were associated with distinct periods of cooling in the world’s mean ocean temperatures, with the Maunder minimum reaching its coolest temperatures in about 1660 and the Dalton minimum in 1820. This matches the observed minimums in coral bleaching observed around these same dates. If the world’s mean ocean temperatures are in fact affected by the level of sunspot activity, then we should expect the level of coral bleaching to decrease between about 2020 and 2050, matching the expected decrease in solar activity.”

  22. what really gets me is that apart from tourism what the hell matter is it if the entire damn thing turns white purple or brindle really?
    it wont all curl up n die and the fish will find smaller areas to live in
    and it really isnt “dying” just bits get seedy n recover as is perfectly natural in cycles of things
    its the HUGE money from tourism thats the driving force behind the moans
    oh and recently of course the insane funding for doing sfa and getting on media as an expert something or other
    Im so pd off by it all for at least 40 yrs i remember it always being someones pet whine
    Id frankly like it to get wiped out entirely and end the crap for good.

  23. Regarding coral bleaching, first its not the death of the coreal, only the greatures which live on iot. Second. What about hot places like Madang in New Guinea, I lived there way back and the water is very wrm and the corals are beautiful. What about the corals in the red sea, a shallow and very hot place, yet coral grows there too.

    Anyway the GBR is very long, from warm in the North and cooler in the South. If warm should be a problem the reef will slowly move to the South.


  24. Figure 4a gives the sea surface temperature as the red line (based on buoy and ship measurements), and anomaly for the sea surface temperature from Mann (based on a lot of proxies) as the black line, yet the two scales are not the same. The left spans 27.4 to 28.8°C, while the right spans -0.4 to 0.6°C. As they are both temperatures of the same area, they should both be plotted on the same scale. This is a bit deceptive to scale the two differently and then plot them on the same graph. I don’t believe the uncertainty of ±0.23°C either. Is that 1-sigma because it cannot be 3-sigma with the uncertainty of the measurements both accuracy and spatially, and the resolution of the instruments.

  25. I wonder if that Paragon of virtue th BBC will report this after their previous promotion of some truly junk science on this subject? No I thought not. Welcone to the well named Adjustocene.

  26. Living standards are increasing the world over, so what’s an “alarmist” to do when faced with a critical shortage of hobgoblins? The scary thing is that there is a vast army of these SJW types, whose entire existence is defined by their adherence to a “cult of doom” ideology. You could summarize it as: “Man bad, nature good.” and “Business bad, gov’t good.”

  27. All this sciencey stuff goes over my head but doesn’t global warming also affect El Nino? If so then surely this doesn’t prove it’s nothing to do with global warming

  28. I was taught at school that the Coral Reef is a living thing that grows upwards like a tree. As it grows upwards, it gets closer to the surface where it is vulnerable to Sun exposure, particularly at low tide where it can be above tide level. The exposed area becomes bleached and dies. The dead top section is then eroded away by high seas during storms, and ends up on our sandy shores. This then allows enough water cover for healthy Coral to grow again. This is no longer taught at Schools since the Green Brigade convinced the teachers otherwise…A natural cycle.

  29. But an El Nino blows warm surface waters away from Australia and reduces the sea level by up to 20 cm I have read. Temperature? More likely exposure to air/stronger sunlight is the cause.

  30. So because GBR bleaching occurred before global warming proves that global warming will not exacerbate GBR bleaching?

    Here’s what the authors concluded:

    Over the coming century, rapid environmental change will include multiple-stressors (Hoegh-Guldberg et al., 2007; Hofmann and Schellnhuber, 2009; Bay et al., 2017), and the increase in prevalence and frequency indicate that we may be coming to a tipping point beyond which survival in uncertain.

    And the fact that lung cancer existed before tobacco use was prevalent proves that smoking does not cause lung cancer!

    • *buzzzz* Flag on the play! Straw man and red herring rolled into one. 30 yard penalty and loss of down.

Comments are closed.