CNN: “Climate change endangers dozens of World Heritage sites”… Unmitigated horst schist

Guest slam dunk by David Middleton

For those with sensitive ears (or eyes):

horst

Horst (USGS)

Schist (Michael C. Rygel via Wikimedia Commons)

 

Climate change endangers dozens of World Heritage sites

By Sandee LaMotte, CNN

October 16, 2018

(CNN)Pull out your passport and pack your bags for the sunny Mediterranean. But hurry.

You’ve got a lot of traveling to do if you’re going to see some of the historical wonders of the world before climate change further damages them, according to a study published Tuesday in the journal Nature Communications.

Across the Mediterranean region, flood risk may increase by 50% and erosion risk by 13% by the year 2100, the study found, with considerably higher increases at specific World Heritage sites, areas chosen to be preserved due to their importance in human history.

The impact on those historical icons would be significant, the study warned, unless actions are taken quickly.

“Adaptation planning is urgently needed,” said lead author Lena Reimann, a doctoral researcher for the Coastal Risks and Sea-Level Rise Research Group in Germany. “If our common heritage is destroyed or lost, it is not possible to replace or rebuild it.”

[…]

[Blah, blah, blah]

CNN

The Nature Communications paper is not behind a paywall.

Figure 1 from Reinman et al, 2018

Reinman et al., 2018 is boiler plate RCP8.5 bad science fiction.

 

Holocene Sea Level

I didn’t take the time to look up the dates of these World Heritage sites… But I’m going to guess they’re OLD.  Many of them probably date back to the Early to Mid-Holocene.  [My bad… That was a bad guess.  The Late Holocene (Meghalayan Age) begins in 4200 BP (2250 BC)]  Here’s a Holocene sea level reconstruction for the Arabian Gulf, with a recent reconstruction of global sea level since 1800 (Jevrejeva et al., 2014) and the satellite sea level trend from CU…

Arabian Gulf sea level reconstruction from Jameson and Strohmenger (2012). Note the insignificance of modern sea level rise .

While this sea level reconstruction is for the Arabian Gulf, the Holocene High Stand was a global phenomenon.

Stormy Weather

Abstract
A high-resolution record of paleostorm events along the French Mediterranean coast over the past 7000 years was established from a lagoonal sediment core in the Gulf of Lions. Integrating grain size, faunal analysis, clay mineralogy and geochemistry data with a chronology derived from radiocarbon dating, we recorded seven periods of increased storm activity at 6300–6100, 5650–5400, 4400–4050, 3650–3200, 2800–2600, 1950–1400 and 400–50 cal yr BP (in the Little Ice Age). In contrast, our results show that the Medieval Climate Anomaly (1150–650 cal yr BP) was characterised by low storm activity.

The evidence for high storm activity in the NW Mediterranean Sea is in agreement with the changes in coastal hydrodynamics observed over the Eastern North Atlantic and seems to correspond to Holocene cooling in the North Atlantic. Periods of low SSTs there may have led to a stronger meridional temperature gradient and a southward migration of the westerlies. We hypothesise that the increase in storm activity during Holocene cold events over the North Atlantic and Mediterranean regions was probably due to an increase in the thermal gradient that led to an enhanced lower tropospheric baroclinicity over a large Central Atlantic–European domain.

Sabatier et al., 2012

Figure 1 from Reinman et al, 2018 with the location of Medeiterranean paleostorm study highlighted.

The paleostorrn data were available from NOAA’s paleoclimatology library.

Most of the past 7,000 years was far stormier in the Mediterranean than today… And all that ancient schist survived.

I don’t have a full copy of Sabatier, but the full text of Yu et al., 2016 is available and they provide a good discussion of clay mineralogy as a proxy for paleostorm activity.  Smectite, illite and chlorite are clay minerals.

Conclusion

References

Bard, E., B. Hamelin, M. Arnold, L. Montaggioni, G. Cabioch, G. Faure & F. Rougerie. Deglacial sea-level record from Tahiti corals and the timing of global meltwater discharge.Nature 382, 241 – 244 (18 July 1996); doi:10.1038/382241a0

Blum, M.D., A.E. Carter,T. Zayac, and R. Goble. Middle Holocene Sea-Level and Evolution of The Gulf of Mexico Coast (USA). Journal of Coastal Research, Special Issue 36, 2002.

Grant, K.M. E.J. Rohling, M. Bar-Matthews, A. Ayalon, M. Medina-Elizalde, C. Bronk Ramsey, C. Satow and A.P. Roberts. 2012.  Rapid coupling between ice volume and polar temperature over the past 150,000  years.  Nature, Vol. 491, No. 7246, pp. 744-747.DOI: 10.1038/nature11593  NOAA Study Page:https://www.ncdc.noaa.gov/paleo/study/13685

Jameson, J., C. Strohmenger. Late Pleistocene to Holocene Sea-Level History of Qatar: Implications for Eustasy and Tectonics. AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California.

Reimann, Lena,  Athanasios T. Vafeidis, Sally Brown, Jochen Hinkel, Richard S. J. Tol. Mediterranean UNESCO World Heritage at risk from coastal flooding and erosion due to sea-level rise. Nature Communications, 2018; 9 (1) DOI: 10.1038/s41467-018-06645-9

Sabatier, P., L. Dezileau, C. Colin, L. Briqueu, F. Bouchette, P. Martinez, G. Siani, O. Raynal, and U. Von Grafenstein. 2012. 7000 years of paleostorm activity in the NW Mediterranean Sea in response to Holocene climate events.  Quaternary Research, Vol. 77, Issue 1, January 2012, pp. 1-11.  doi: 10.1016/j.yqres.2011.09.002  NOAA Study Pagehttps://www.ncdc.noaa.gov/paleo/study/12504

Zhaqjie Yu & Wan, Shiming & Colin, Christophe & Yan, Hong & Bonneau, Lucile & Liu, Zhifei & Song, Lina & Sun, Hanjie & Xu, Zhaokai & Jiang, Xuejun & Li, Anchun & Li, Tiegang. (2016). Co-evolution of monsoonal precipitation in East Asia and the tropical Pacific ENSO system since 2.36 Ma: New insights from high-resolution clay mineral records in the West Philippine Sea. Earth and Planetary Science Letters. 446. 45-55. 10.1016/j.epsl.2016.04.022.

 

 

 

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80 thoughts on “CNN: “Climate change endangers dozens of World Heritage sites”… Unmitigated horst schist

  1. But…But…But…if all the Mediterranean Beaches vanish, where will all the tourists go?
    I know…when the tides recede again (and they will) the tourists can all go to the old beaches offsprings … the Sons of Beaches

    • if all the Mediterranean Beaches vanish, where will all the tourists go?

      …to the artificial islands China is building in the South China Sea

      • The manmade islands are only a few feet above sea level they would be under, which sort of tells you how much China believes the sea level rise.

    • Bryan A, ‘sons of beaches!, like it! Let’s hope no one mentions which seaport the Romans landed their main invasion force when they invaded England. That would be the one that’s no longer a seaport but well inland now. Bloody Celts and their fossil furled chariots!

  2. They worry about preserving cultural heritage while letting in millions of immigrants from alien cultures?

    • After the Talibandals blew up the 100ft high statue of Buddha (over which I cried with no skin in the game) I made a prediction that the Mona Lisa, and countless treasures of our amazing civilization are eventually toast in the Merkelobcene age. Look what the Demovandals in tn America have done destroying monuments and history they judge Politically Incorrect. I’m certain Alexander, the Caesars, Charlemagne, Plato, the ‘Henrys’, ‘Louis’ Montezuma, Darius,….were racists, tribalists… even approptiators of cultures! General Robert E Lee was a Democrat for crysakes and so was the whole Confederate shebang.

  3. 4-6K years ago the Gulf of Mexico shoreline was 50 miles north of where it is presently. The oceans are down two meters and we’re supposed to worry about it rising 3.3cm a century? Not.

      • In actuality its 2mm. Inflation in climate science is rampant. Its 1995 projections which were 90% “certain” using their iconic CO2 warming formula turned out to be 300% greater than observations. They were so shocked they took the ‘likely’ warming by 2100, divided it by 3 and then proclaimed that 2C by 2100 was a serious concern.

        Then we had the “Dreaded Pause^TM” that lasted as long as the warming that inaugurated the whole warmo industry. A poker player’s “tell” twigged me to what most likely followed.

        Remember the “Pause” engendered unwanted thoughts among the more honest but more fragile researchers that led to the knockout “Climate Blues” that actually terminated careers. A number of scientists came down psychologically ill. Oh they rationalized that they were depressed because they were seeing the horror of future climate warming and no one would listen. They even had psychologists enabling this false cause (ironically, it is one of psychology’s few solid diagnoses, ahem … being in Dnile! ). Its of significant scientific and philosophical interest that if your brain comes up with the right answer and you don’t like it and you suppress it and reject it, it makes you sick! Wow!

        The Pause became the elephant until mighty white hunter Karl of NOAA, days before his retirement, Karlized it in 2015. The few brighter lights among skittish Climateers, set to wondering if even burning fossil fuels unrestrained might not result in reaching 2C by 2100. They secretly then pushed the starting gate for warming due to mankind from 1950 to 1850, thereby banking 1C of dangerous warming and trimed another 0.5C off, so that they gave themselves 80yrs to get 0.5 more warming and hyped the hell out of 1.5C over two and a half centuries as dangerous enough! They knew that the clinate had warmed 0.6C in one century, so put that in your future observed temperatures and smoke it.

        • Gary, I think the technical term for what you are describing is “cognitive dissonance”. Made famous by the book “When Prophecy Fails” by Leon Festinger. https://www.amazon.com/When-Prophecy-Fails-Leon-Festinger/dp/1578988527 Festinger and others observed a saucer cult that predicted the end times at a certain date. When the date came and passed with no apocalypse, you would think that the true believers would change their minds.

          On the contrary, in many cases the beliefs were strengthened and elaborated. Strange irrational excuses replaced the earlier confident predictions and the cult carried on.

          Never underestimate the ability of the human mind to cling to a belief in the face of clear and obvious contrary evidence. The phenomenon called the “sunk cost fallacy” makes it hard to change, and the mind-bending effects of cognitive dissonance make it hard to see the facts even when they are right in front of you. Especially when your paycheck and reputation depends on it.

  4. Talking about world heritage sites …

    Today’s Speed Bump cartoon has two folks in native costume commenting on a guy in a suit who is watching a volcano erupting.

    This guy says 97% of the climate scientists are making the gods angry.

    Even the gods are skeptical.

  5. “I didn’t take the time to look up the dates of these World Heritage sites… But I’m going to guess they’re OLD. Many of them probably date back to the Early to Mid-Holocene.”

    Had you taken the time (or known something about history), you would have known that these sites are much younger than that …

  6. I’m sorry but there is a much bigger problem, the internet. KEY INTERNET CONNECTIONS AND LOCATIONS ARE AT RISK FROM RISING SEAS. From the November-December soon to be like Scientific American American Scientist. The preceding article is CLIMATE-DISTURBED LANDSCAPE that shows a burned southern California car as the poster example of climate change danger from hydrocarbons. The article before that TRASHING THE TANKS says “It is time to develop visual rhetoric that shocks viewers into understanding their personal responsibility for our deteriorating ocean…” using comparisons between Monterey Bay and Bali. For “A Need for Honest Visual Rhetoric.”

    Argument is that we are not showing the oceans properly in the Monterey Bay Aquarium and the Texas State Aquarium (Islands of Steel) which shows a clean oil platform with lots of fish. They are too clean so Zoos and Aquariums need to trash them with trash. Article does not even “know” that ‘Coral Bleaching’ is supposed to be caused by temperature not ‘acidification.’

    These articles are available— https://www.americanscientist.org/article/trashing-the-tanks
    and a good article– https://www.americanscientist.org/article/americas-cat-is-on-the-comeback
    Others apparently not but searching might turn something up. Its raining here today on a high water table so this might not show up!

  7. I’ve been to many of these sites. They are miles from shore, literally miles from shore and many meters – they used to be at the shore but today…. Heritage sites Tiryns is far out and farther out than later ones, even Pompey is back a bunch, look where the beach launches are. Been all over that area and all the sites are back from the shore many meters higher either through plate movements from deglaciation or sea level lowering. Anyone who has been around that area would know they aren’t threatened by sea level rise.

  8. I think the old horst schist comment is in need of a good nappe.

    R W Fairbridge first mapped the Holocence Highstand back in the 1950’s. All the subsequent work bears this out.

    He was a pioneer in his time and a good one at that.

  9. David, you show the reader that geological training and experience can’t be beat when it comes to solving “crimes” 100s to billions of yesrs old (or hours in the case of a geological former classmate of mine who became a forensic scientist at the Royal Canadian MP headquarters). A good geologist has a keen forensic mind and an eye for detail. The science is a wonderful window into pasts so different from our own, its as if earlier inhabitants simply disembarked and we got on a thoroughly renovated earth for our ride. Even as a student, I thought that anyone who fancied himself a philosopher or even well educated must take historical geology.

    Only with aquaintance with this sterling subject and its methods can one see fully how terribly handicapped the big names in climate science are, nevermind the minions of sociologists, psychologists, political scientists, philosophers-lite, astronomers, journalists and the like who are bulldozing horst schist they vaguely understand.

    Hansen shot his confident mouth off and THEN learned about the LIA, MWP and all the other cold and warm periods and has spent a lifetime spunning and backpedalling. The Hubris of thinking other scholars in different fields had done so much work on climate that it would have tempered his zealotry to know about.

    David, you are a superb researcher that appears to be able to take on the dark side almost single handedly. No wonder it only takes 3% to blow the 97% climate clones away.

    • But… even I lose track of the relationship between geologic time and human history. The Late Holocene begins in 4200 BP (2250 BC)… Most really old archaeology is younger than that. It didn’t even cross my mind until I read Richard Tol’s comment.

      • No Crime committed by you there. Tol didnt have the good manners to compliment you for your excellent work before offering his criticism. Or, more ironically, he may not know he was looking at somethong good. He’s displayed the kind of hubris on other occasions that suggests he he has all the knowledge he needs from book learning. You, a gentleman thanked him. That’s real class.

  10. All a bit of a nonsense. I know well some of the places on the map (I was born and grew-up only few miles away from no. 125 on the map Figure 1 from Reinman et al) All this coast line is still tectonically very active due to the ongoing collision between African and Eurasians plates.
    Along Adriatic coastline with a large of numbers on the map, some places go up while others sink. I know an area where an old Roman road that is now well below low tide line. Here is an image of rocks next to the beach I use to go as teenager (the Getty Images copyright available at price £375.00, about US$450, LOL) Not for reproduction !
    Further east in the Aegean sea many ancient Greek settlements sunk long time ago.

    • The coastal city of Ephesus is now well inland. Paphos in Cyprus (79) is shaken by earthquakes from time to time. Do these fear-mongers know anything? I wish they would open their eyes and realise the earth is not a never-changing entity.

      • Yes and the next global glaciation will be here before any of these sites will be under threat from rising sea levels at the current rise rate.

      • Ephesus is an old harbour which lost its function to accretion. Sea level rise would reverse that. Recently accreted material can erode quickly. The more impressive stuff is elevated on rocks (those ancients weren’t fools) but you could be looking at a Venice of Ephesus in the future.

    • Both Old Dubrovnik and the Bay of Kotor are built up right to the sea front, with an itty-bitty ancient sea wall in places.

      There is no space for a dyke, and that would ruin the site.

      You can build a barrier to protect Kotor. For Dubrovnik, a glass seawall is probably the best option.

      • Both towns, need protecting from people in the first place, but they are more likely to be damaged by earthquakes long before the global warming sea rise arives.
        In 1667 Dubrovnik was almost completely destroyed and thousands of people were killed, it was subsequently rebuild to what you see today. In April of 1979 Dubrovnik was hit by another strong earthquake, 7.2 on the Richter scale badly damaging more than 1,000 buildings. The last earthquake rumbled the town in July of this year.
        Kotor was also hit by major earthquakes in: 1537, 1563, 1667, 1729, and most recently in 1979 when many buildings inside and outside fortifications were badly damaged.
        p.s.
        Lord Byron wrote: “At the moment of the creation of our planet, the most beautiful merging of land and sea occurred at the Montenegrin seaside… When the pearls of nature were sworn, an abundance of them were strewn all over this area.”

  11. Now that my delicate sensibilities have recovered from your pictorials of “horst” and “schist”, can I just say that you are (like it or not) teaching me things.

  12. San Pietro a Grado is a church marking the spot where St Peter disembarked after crossing the Mediterranean Sea on his way to Rome in 44AD. It now sits high & dry, 3 miles inland. A few miles further east (even higher & drier) stands the famous Leaning Tower. Within a few hundred yards of that stands the medieval Naval Arsenal, originally built in the 16th century–on the coast. Near to that, a few yrs ago, excavations revealed several buried ancient Roman ships where the harbor dating back to Etruscan times was situated.

    • Roman forts on the SE English coast are now farther inland than when built, even though southern Britain has been sinking as northern Britain rebounds from the loss of its heavy ice load during the last glaciation.

      Not just structures from the Roman Warm Period, but those formerly at sea level during the Medieval WP as well are now high and dry. For instance, Harlech Castle, Wales. Built by Edward I from AD 1282 to ’89, the sea originally came much closer to the fortification than now. A watergate and a long flight of steps leads down from the castle to the former shore, which allowed it to be resupplied by sea during sieges. Today the stairs end on dry ground.

      • However due to erosion huge bits of Britain’s EAST coast have vanished. Along with Doggerland.

        Loss of southern ports inland is more about silt deposition than sea level changes

        • Doggerland where oil exploration pulled up mammoth ivory. It was a steppe, before catastrophic “hyperflooding” (2 times) which produced the Netherlands.
          See, England already had Brexit!

      • “Accretion would turn to erosion if sea levels rise.”

        Yes and no. Accretion can occur on a sinking coast as well. Southeastern Britain is a good example. Lympne (Lemanis) was an important roman seaport. Or the roman Saxon Shore fort at Pevensey (Anderida), now almost a mile inland.
        And conversely a rising coast can erode. It is all a matter of exposure currents and sediment supply.

  13. Ozymandias
    Percy Bysshe Shelley, 1792 – 1822

    I met a traveller from an antique land
    Who said: “Two vast and trunkless legs of stone
    Stand in the desert . . . Near them, on the sand,
    Half sunk, a shattered visage lies, whose frown,
    And wrinkled lip, and sneer of cold command,
    Tell that its sculptor well those passions read
    Which yet survive, stamped on these lifeless things,
    The hand that mocked them, and the heart that fed:
    And on the pedestal these words appear:
    ‘My name is Ozymandias, king of kings:
    Look on my works, ye Mighty, and despair!’
    Nothing beside remains. Round the decay

    Tonyb
    Of that colossal wreck, boundless and bare
    The lone and level sands stretch far away.”

  14. Step 1: Make a list of stuff people think are important or that they just like.
    Examples: Beer, Historical Sites, Butterflies, etc.
    Step 2: Write articles warning how they are in danger from Climate Change.
    Step 3: Make sure the only experts you consult for quotes in your article are pre-approved.
    Step 4: Print these articles timed once per day, except more frequently just before elections.

    • Step 1: Make a list of stuff people think are important or that they just like.
      Examples: Beer, Historical Sites, Butterflies, etc.

      Step 2: Ask people how much they are personally prepared to spend now on protecting those things from something that may or may not happen over the next 80 years. Then tell them that there is a high probability that what they spend today won’t alter future weather.

  15. A number of important ancient Egyptian monuments were relocated to preserve them from flooding as part of the Aswan Dam construction, it can be done if necessary.

      • I’m certainly no expert but many, probably most, archaeologically important sites are temples citadels and the like and although many sites appear located on coasts on the map they are in fact sited on high promontories or in fact inland on hills, even burial sites were usually on high ground.
        For instance the ancient harbour of Byblos is now built over but the temple is on adjacent high ground about 15 meters above sea level, at the current rate of sea level rise it will take a long time for it to be threatened if ever.

        • I was just suggesting that if you move a historical site to preserve it… you might actually have not preserved it.

          • It is only from the short-term view of humans, who generally wear out before 100 years, that trying to preserve man-made things makes sense, even temporarily. But if you take the long-term geological view, land is always changing, just as the climate is always changing. Eventually, all those sites will be recycled along with the crust they reside on.

      • Lets hope Paul Revere doesnt turn out to have been anti diversity or thought wonen don’t have penises!

        • Well… Even the Alamo is a UNESCO World Heritage site… Last I checked, Travis, Bowie & Crockett hadn’t been erased yet.

          • I take that back… The history has been erased by the UN…

            San Antonio Missions

            The site encompasses a group of five frontier mission complexes situated along a stretch of the San Antonio River basin in southern Texas, as well as a ranch located 37 kilometres to the south. It includes architectural and archaeological structures, farmlands, residencies, churches and granaries, as well as water distribution systems. The complexes were built by Franciscan missionaries in the 18th century and illustrate the Spanish Crown’s efforts to colonize, evangelize and defend the northern frontier of New Spain. The San Antonio Missions are also an example of the interweaving of Spanish and Coahuiltecan cultures, illustrated by a variety of features, including the decorative elements of churches, which combine Catholic symbols with indigenous designs inspired by nature.

            https://whc.unesco.org/en/list/1466

        • Actually, just as men have breasts and nipples (male and female were created from a common design) women have penises. It just happens that they are minature, have no urethra, and are called clitorises. What’s in a name?

  16. This world heritage concept is a threat to freedom when you look at it in depth and with some hindsight.
    My comments are qualified with the fact that through Court action in Australia, I once delayed the listing on the world heritage register of a significant part of our country. The secondary, driving purpose then was that corporately, we had been granted mineral leases to develop new uranium mines in the area. The UN through world heritage was ruthless in squashing this. We never did get to mine there. Nor did we get a penny of compoensation for the millions spent and the billions that could have been earned through uranium exports.
    This note is to rncourage readers to view the world heritage concept not through tear-filled eyes as an example of governments working together to preserve places of beauty for future generations. It should be viewed as yet another plank in the UN plans to control, vis national laws and regulations, the effective ownership of land and its features and to control futher use.
    If you doubt this, ask why the UN needs to be involved. Each country on the globe has primary responsibility for its assets. The UN is only there as a policeman to cast shame on countries that step out of line and threaten vague concepts like ‘the enjoyment of future generations’. The success record of the world heritage concept is rather low, because countries have to find the money to manage the sites the way the UN wants. Often, this amount to an exercise in how little money a country can spend, to avoid the shaming process. There are invariably better ways to spend the money. Geoff.
    p.s. Also, watch the gullibility of of Judges world-wide on this one. It is so easy to be self-comforting with the money of other people.

  17.  
    “The Budget should be balanced, the Treasury should be refilled, public debt should be reduced, the arrogance of officialdom should be tempered and controlled, and the assistance to foreign lands should be curtailed , lest Rome will become bankrupt.  
    People must again learn to work instead of living on public assistance .”  –  Cicero, 55 BC

     So, evidently we’ve learned absolutely nothing over the past 2,073 years.

  18. At least they touched on erosion which is my analogy for demonstrating the debate tactics of Chinese-funded enviros. Erosion is evidence of change and with some strawman add-on arguments you get human-caused erosion that must be stopped with an erosion tax. Denying it brings forth the static, flat earth attack gems.

  19. So …… sacrifice our Today to preserve monuments of a long dead yesterday?
    What will our monuments be?
    Broken pinwheels in a third-world world?

  20. Talk about heritage!
    Have a look at a place 6000 years before Stonehenge, Göbekli Tepe in Anatolia, Turkey, not too far from the Med, and appearing soon after the sudden Med flooding of the Black Sea (Bosphoros breakthrough).
    https://thumbs-prod.si-cdn.com/tiwf6eaETBVkAlEmwFmoVq7BZnk=/800×600/filters:no_upscale()/https://public-media.smithsonianmag.com/filer/gobeklitepe_nov08_631.jpg

    Russian marine archaeos found the ancient beach of that freshwater Black sea and some objects. Fisheries today do not trawl too deep there!

  21. Not to mention the Sphynx – likely much older than Cheops, with evidence of water erosion. Dated using its equinox orientation, being a large cat (originally, before the Rameses’ facelift). The sun rising in Leo was last at 10,000BP, right at the end of the “ice age”.

  22. There is no need to worry. The next ice age will cause sea levels to plummet as ice sheets reform on the continents. The start of the next ice age may be only a few thousand years off so we need to enjoy the current inter glacial period while it lasts. Lower sea levers will cause current port facilities to be high and dry.

  23. David: Please look more closely at the graph of the putative Holocene Highstand. The first thing to notice is the drop of 2 m over about 8000 years; -0.25 mm/yr = -0.25 cm/decade = -0.1 inch/decade = -1 inch/century. This rate of SLR is about 1/5 of the average rate of the 20th century or about 1/10 the current rate (about +1 inch/decade in units whose physical significance is easy to grasp. 20th century SLR is roughly an order of magnitude larger than the tiny changes you are discussing.

    The different locations on your graph disagree about SLR by about 10 m 7000 years ago. Obviously none of these are likely to represent “global” sea level. The standard reconstructions use data from locations that a supposed to be geologically stable. The Mediterranean is not such a region. There are numerous archeological sites (such as Alexandria) that are now under water, while other ports are now miles from the sea (Ostia Antica, Troy, Ephesus). Port cities on rivers are particularly tricky since the river deposits sediments that are shaped by coastal currents. It certainly makes sense to me that some of the GIS melted during the Holocene Climate Optimum, producing sea level higher than today. However, I don’t think we have the ability to compensate for local vertical land motion and other geological processes and accurately detect global changes occurring at rates well below 1 m/millennia.

    https://listovative.com/10-lost-underwater-cities-of-ancient-world/

    • Also note that the “Global” Sea Level is far from flat, and that the effect of e. g. melting glaciers will vary strongly depending on where the glaciers are. In the “near zone” (within a few thousand kilometers) melting glaciers will even result in lower sea-levels.

      • TTY: The best composite record of sea level comes from locations in the stable center of tectonic plates far from changing ice caps. Nevertheless, sea level during the Holocene at such optimal sites disagrees by a few meters. We currently don’t have the ability to accurately track rates of sea level rise or fall over millennia that a significantly lower than the current rate: 2.5 mm/yr (today?) = 2.5 m/millennium, which would probably be an unambiguous 5 m if it persisted over 2 millennia. 0.5 mm/yr – 0.5 m/millennium, unambiguous detection unlikely. 10 mm/year = 10 m/millennium, the rate of SLR for 10 millennia as the last ice age ended.

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