2 New Studies Affirm Coral Bleaching Events Are Natural – More Bleaching In 1750s, 1890s Than Today

Coral reef bleaching events occur after exposure to unusually warm water temperatures or excessive sunlight.  Activists claim that today’s coral bleaching events are not only unprecedented, but reefs will soon disappear.  In contrast, scientists have determined that modern-day bleaching events are not unusual or unprecedented, but only a continuation of a naturally-occurring phenomenon.

A few thousand years ago, sea surface temperatures in the South China Sea were at least 2°C warmer than they are today.  Mass coral death events routinely occurred due to severe bleaching (Xu et al., 2018).

In more recent centuries, a new study reveals that there were more bleaching events in the 1750s and 1890s — during a period encompassing the Little Ice Age — than there have been in recent decades (Kamenose and Hennige, 2018).

Obviously, corals were able to survive past bleaching events, which are naturally-occurring and “by no means a new ecological phenomenon of current global warming” (Xu et al., 2018).

What Activists Write About ‘Unprecedented’ Coral Bleaching

Image Source: Popular Science

Image Source: Mother Jones

What Newly Published Science Says…

Xu et al., 2018

Evidence for the Thermal Bleaching of Porites Corals

From 4.0 ka B.P. in the Northern South China Sea

This study provides evidence that thermal coral bleaching events have occurred in the warmer mid-Holocene (where maximum monthly summer SST was 2 °C higher than at present) in Hainan island.  … We carried out this pilot study to explore the responses of corals to abnormally warm conditions in prehistoric periods. Four massive Porites coral fossils that died 3800 – 4200 years ago were collected from the Wenchang fringing reef, Hainan Island, NSCS. The reconstructed SST just prior to the mortality surfaces and growth discontinuities were higher than the [modern] maximum summer SSTs in the NSCS [Northern South China Sea]. This indicated that the corals’ deaths and interruptions in growth – which were observed to be in summer – were accompanied by an anomalously high SST [sea surface temperature]. Enhanced Δδ18O suggested increased evaporation and high-SSS conditions, attributable to warm sea surface temperatures.”

“A significant negative shift in δ13C just prior to mortality surfaces and growth discontinuities indicated a reduced photosynthetic intensity of symbiotic zooxanthellae. Together, this evidence for increased SST and SSS and decreased photosynthetic intensity strongly suggest that the growth hiatuses and coral deaths observed were the results of severe coral bleaching. This in turn indicates that coral bleaching events under high SST conditions have already occurred in the mid-Holocene and are by no means a new ecological phenomenon of current global warming.”

Kamenose and Hennige, 2018

Reconstructing Four Centuries of Temperature-Induced

Coral Bleaching on the Great Barrier Reef

Reconstructed bleaching was evident through the entire available record from 1575 to 2001. To determine any GBR-wide bleaching patterns, corals were pooled from all regions in the GBR spanning 15.13 to 22.23°S. Quantitative assessments of bleaching were conducted between 1620 and 2001 for frequency and 1640–2001 for prevalence. Outside of these periods, while we have documented historic bleaching, it is possible that the number of cores available drove the patterns observed.”

Reconstructed bleaching frequency demonstrated three trends; (1) frequency increased from 1620 to 1753 ± 31 (years) reaching up to 6 years of each decade showing evidence of bleaching in at least 20% of coral cores. (2) Bleaching frequency decreased to 1820 ± 31 when only 1 year of every decade had evidence of bleaching in at least 20% of coral cores. (3) Bleaching frequency increased again from 1820 ± 31 to 2001. The 1890 and 1750 decades were notable for unusually high bleaching frequencies. In contrast to bleaching frequency, bleaching prevalence only demonstrated two trends; (1) a negative trend from 1640 – 1774 ± 78, with prevalence falling from 41 to 21%. 2) An increase in bleaching prevalence from 21% in 1774 ± 78 to 31 % in 2001.”

30 responses to “2 New Studies Affirm Coral Bleaching Events Are Natural – More Bleaching In 1750s, 1890s Than Today”

  1. Yonason

    FYI – Not necessary to post.

    What’s going on with your website, Pierre? It’s suddenly not compatible with my browser (Firefox), though I tried it with Chrome, and it seemed normal there. But I don’t use Chrome, so while I will still be dropping by, I’ll probably not be commenting much until it gets fixed.

    Best Regards

    1. P Gosselin

      I’ve gotten complaints over the day. I’m not sure what’s going on. I’m hoping the problem goes away on its own. Must be Russian hackers

      1. steve

        Hi Pierre, Is SebH a Russian interloper come hacker?

      2. Yonason

        Since then the NOAA hurricane website was behaving the same for me, so it’s not just you. Yeah, must be the Russians 😉

    2. spike55

      I’m getting an annoying log-in request from the server.

      Hides itself behind other windows and you can’t type until you get rid of it.

      That’s ‘puters for ya. ! 😉

      1. Yonason

        Same for me on Firefox, spike, but on Chrome it doesn’t. Not going to switch, just for that, though.

      2. Yonason


        newsmax.com is also affected, and the error msg I get is…

        “Please disable your Ad Blocker to view this site properly.”

        Uh, no, but I might for Pierre in a bit, just to see if that helps.

  2. Bitter&twisted

    More “settled science” being undermined by reality.
    Unfortunately reality is something that climate “scientists” wouldn’t recognise if it leapt up and bit them.

  3. spike55

    The most recent GBR bleaching was because of 2 main factors.

    1. El Nino caused a DROP in sea level, leading to over -exposure to sunlight.

    2. The oceans currents were very still for a few weeks, that lead to warming and a lack of nutrients and dissolved oxygen and CO2, meaning that there was no food transported to the coral denizens.

    1. SebastianH

      There was an El Nino in 2017 or this year?

      1. spike55

        Poor seb. IGNORANT and attention-seeking as always. !

        1. SebastianH

          Perhaps you want to elaborate why you think I was ignorant here?

          The recent news about the Great Barrier Reef were about researchers finding that the coral cover has fallen between September 2017 and May 2018 compared to the year before. Was there an El Nino causing a drop in sea levels in that later period or not?

          1. spike55

            The last main bleach was during the El Nino.

            Reports from the Eye on the Reef network indicate that, following summer 2017/2018, there are currently minor levels of coral bleaching, disease and damage in the Marine Park. Severe active outbreaks of the coral-eating crown-of-thorns starfish continue in the northern and central management areas, as well as in the southern Swain Reefs.

            The full impacts of the major flooding on the tropical northern coast, and cyclone Iris on the central and southern management areas, are yet to be determined.

            You are such a GULLIBLE little troll, seb. Totally un-sceptical of far-left newspaper reports. A true “believer”.

  4. Yonason

    Oh, yes. I do want to get these out there.



    I’m surprised there’s anything at all positive about coral bleaching, after the chilling news of attempts to stifle research in that area that exposes the false narrative.

    The world may or may not be warming, but the climate of intellectual freedom is in the deep freeze.

  5. Yonason

    OK, back to almost normal.

    NOAA, and others, too.

    Internet hiccup, I guess.

  6. SebastianH
    1. spike55

      WOW, lots of model “predictions” based on shoddy fanciful climate predictions.

      WOW, lots of ocean acidification (which isn’t happening)

      WOW, a study that shows coral doesn’t like copper

      Yet all seem TOTALLY IGNORANCE that bleaching has happened like FOREVER,

      And if bleaching is cause by warmer ocean then it is DEFINITELY NOT anything to do with atmospheric CO2, because atmospheric CO2 cannot cause warming of oceans.

      You are aware that coral produce their own acids to make their shells, aren’t you seb???

      Those doing that “acidification studies seem blissfully unaware of coral biological activity.

      Do you DENY that during the first 9000+ years of the Holocene, oceans were MUCH warmer.. and yet coral reefs are still here, in fact, many reefs actually came into being during those times when the oceans were MUCH WARMER.


      Again, your manic CLIMATE CHANGE DENIAL causes you to faceplant in the most hilarious manner. 🙂

      1. SebastianH

        And if bleaching is cause by warmer ocean then it is DEFINITELY NOT anything to do with atmospheric CO2, because atmospheric CO2 cannot cause warming of oceans.


        Yes it can and yet it does. Please be so kind and provide proof that shows that the observed warming (the increased OHC) is not caused by the imbalance caused by higher CO2 concentrations.

        Those doing that “acidification studies seem blissfully unaware of coral biological activity.

        Well, it seems like you are an expert. Feel free to step up anytime and tell those “real” experts how stuff really works. Apparently, they don’t know yet …

        Again, your manic CLIMATE CHANGE DENIAL causes you to faceplant in the most hilarious manner. 🙂

        Actually, your behavior caused me to wear a helmet recently, to not hurt myself from all the faceplanting …

        1. spike55

          “*sigh*” Like a little girl.

          gees you are a pathetic little attention-seeker.

          Do you have ANY evidence that atmospheric CO2 causes ocean warming ??? You are totally DEVOID/EMPTY so far.

          Its YOUR fantasy you provide the evidence.

          And that TINY OHC increase that causes a piddling temperature rise of 0.08ºC in 55 years. ROFLMAO

          Its amazing there wasn’t much more ocean warming given the strong solar cycles during that period.

          And again ZERO evidence of ocean neutralisation.

          Do you DENY that corals produce their own acids, even after science has actually MEASURED that fact??

          Continued DENIAL of measured facts makes your ranting very non-credible, seb.

          You remain NOTHING but a brain-hosed troll who cannot back up anything he says with any actual scientific evidence.

          Q1. In what way has the climate changed in the last 40 years, that can be scientifically attributable to human CO2 ?

          Q2. Do you have ANY EMPIRICAL EVIDENCE at all that humans have changed the global climate in ANYWAY WHATSOEVER?

        2. spike55

          “to wear a helmet recently”

          You don’t need just a helmet,

          You need a whole padded cell..

          .. oops.. your mind is already in one. !!

        3. spike55

          Agincourt Reef was one area that was hit hard by bleaching in 2016

          Let’s have a look at the actual SST and air temp during that period


          and some others areas for good measure




          NO SIGN OF ANY WARMING !!!

          Real data, seb, not MYTHS !!!

          The areas most affected in the 2016 bleaching had a 0.2m drop in Sea level over a couple of years

          That’s an 8″ drop in sea level seb. !!!

          http://ift.tt/2xaWOer (vertical axis is in cm)

          There are numerous papers out there about the effects of sea level drop on coral bleaching.
          (I can provide links if need)

  7. Don from OZ

    Seriously, why are we talking about CO2 concentrations reaching 500 ppm or 600 ppm? When it easily surpassed 2000 ppm in the past.
    Indeed SebH Why are you not accepting of your own statement? Confused? Determined to remain convinced regardless of facts?
    Please explain

By continuing to use the site, you agree to the use of cookies. more information

The cookie settings on this website are set to "allow cookies" to give you the best browsing experience possible. If you continue to use this website without changing your cookie settings or you click "Accept" below then you are consenting to this. More information at our Data Privacy Policy