Eye roller: we measured sea levels in the wrong places, therefore it’s ‘worse than we thought’

From the UNIVERSITY OF HAWAII AT MANOA

This image shows the pattern of sea level change or 'fingerprint' resulting from one millimeter per year of Greenland ice melt derived from NASA GRACE measurements. The black circles show locations of the best historical water level records, which mostly fall in the blue areas that are less than one millimeter per year. As a result, these records underestimate global average sea level rise due to Greenland melt by about 25 percent. CREDIT Thompson, et al., 2016

This image shows the pattern of sea level change or ‘fingerprint’ resulting from one millimeter per year of Greenland ice melt derived from NASA GRACE measurements. The black circles show locations of the best historical water level records, which mostly fall in the blue areas that are less than one millimeter per year. As a result, these records underestimate global average sea level rise due to Greenland melt by about 25 percent. CREDIT Thompson, et al., 2016

Historical records may underestimate global sea level rise

New research published in Geophysical Research Letters shows that the longest and highest-quality records of historical ocean water levels may underestimate the amount of global average sea level rise that occurred during the 20th century. Dr. Philip Thompson, associate director of the University of Hawai’i Sea Level Center in the School of Ocean and Earth Science and Technology (SOEST), led the study.

“It’s not that there’s something wrong with the instruments or the data,” said Thompson, “but for a variety of reasons, sea level does not change at the same pace everywhere at the same time. As it turns out, our best historical sea level records tend to be located where past sea level rise was most likely less than the true global average.”

A team of earth scientists from the University of Hawai’i at Mānoa, Old Dominion University, and the NASA Jet Propulsion Laboratory worked together to evaluate how various processes that cause sea level to change differently in different places may have affected past measurements. One particularly important concept is the existence of “ice melt fingerprints”, which are global patterns of sea level change caused by deviations in Earth’s rotation and local gravity that occur when a large ice mass melts. Each glacier, ice cap, or ice sheet has a unique melt fingerprint that can be determined using NASA’s GRACE satellite measurements of Earth’s changing gravitational field.

During the 20th century, the dominant sources of global ice melt were in the Northern Hemisphere. The results of this study showed that many of the highest-quality historical water level records are taken from places where the melt fingerprints of Northern Hemisphere sources result in reduced local sea level change compared to the global average. Furthermore, the scientists found that factors capable of enhancing sea level rise at these locations, such as wind or Southern Hemisphere melt, were not likely to have counteracted the impact of fingerprints from Northern Hemisphere ice melt.

“This is really important, because it is possible that certain melt fingerprints or the influence of wind on ocean circulation might cause us to overestimate past sea level rise,” said Thompson, “but these results suggest that is not likely and allow us to establish the minimum amount of global sea level rose that could have occurred during the last century.”

The investigation concludes that it is highly unlikely that global average sea level rose less than 14 centimeters during the 20th century, while the most likely amount was closer to 17 centimeters.

The full paper can be found here, and more information about sea level change can be found on the University of Hawai’i Sea Level Center website and the NASA sea level change website.

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108 thoughts on “Eye roller: we measured sea levels in the wrong places, therefore it’s ‘worse than we thought’

  1. So, an extra 3 cm. Is this any bg deal, especially when a realistic margin of error is added to measurements which are instrinsically very difficult to perform accurately.

    • Big deal or not, they’re likely to use this as an excuse to adjust sea-level measurements higher and then claim there’s been an unprecedented acceleration in sea-level rise.

    • I’d like to see Dr Philip Thompson’s inverted barometer correction going back to the beginning of the 20th century.

      Then we can start talking.

      It’s funny how, according to GRACE, the water always piles up in the middle of the ocean where there are no tide gages.

    • As I said before, “It’s wurst that we thought.” The stuff that goes into the sausage making of the Eschatological Cargo Cult of the CAGW is nothing that you want to learn about.

    • How do you misunderestimate something that you already know exactly what happened.

      It’s the future that we most often misunderestimate.

      g

      • Is “misunderestimate” a generalization for both “over underestimate” and “under estimate” while excluding “exactly underestimate?”

  2. And in a few more years they will discover that we have been wrong about hydrostatics and that in fact water runs up hill. More not likelys and coulds. Must be grant time.

  3. So if it rose less than we thought in the past it must be worse now.. LMAO and how do we make a fluid body rise in one spot and not distribute evenly. It would seem we are defying the laws of nature now.

    • Prof Humlum explains it at the excellent Climate4you website:
      “Temperature-driven ocean water expansion will therefore not in itself lead to lateral displacement of water, but only lift the ocean surface locally. Near the coast, where people are living, the depth of water approaches zero, so no temperature-driven expansion will take place here (Mörner 2015). Mechanism 3 is for that reason not important for coastal regions …”.
      The sea level change in the middle of oceans could be due to thermal expansion while that around Greenland may be due to deglaciation.

      • Baloney ! at the coast the water level REACHES zero, and most people live on the dry side of the water, and not the wet side.

        g

      • Call the Guiness Book of World Records! This is the stupidest answer ever given! The middle of the ocean expands its depth and that has no effect at the coasts? Ridiculous!

      • I dont buy that argument. The surface of the oceans must be in level perpendicular to the gravity.
        The gravity changes hardly by some warmer water, so the mid ocean expanded water flows out and also into the coasts. I wonder how Mörner could come up with that idea.

    • It IS worse now – not the Sea-Level, but its reporting!

      In tectonically inert areas, which neither subside or experience uplift, SLR hovers around the 12cm per century range, and now that Antarctica is gaining snow and ice that reduces SLR by 0.23mm per year (see Zwally, Li et al Journal of Glaciology, Vol. 61, No. 230, 2015), the net rise is subject to further reduction, as opposed to increase.

      • Svend wrote, “The surface of the oceans must be in level perpendicular to the gravity,” and George wrote, “They’re right at sea level. How could they be taller?”

        Gravity balances mass, not volume. So, when a section of the open ocean expands due to temperature change, the water does not “run downhill” to another, cooler, part of the ocean. Rather, it bulges up, in place. The most dramatic example is ice:

        The displacement of that ice is exactly the same when it melts. No lateral water flows result, and sea-level is not affected elsewhere (other than through an insignificant effect on salinity).

        Here’s some more information:
        http://www.sealevel.info/resources.html#steric

      • Happens all the time. That’s how the satellites spot great pools of warm water. They’re “taller” than the surrounding waters.

      • “They’re right at sea level. How could they be taller ??”

        It is a mistake to think the sea is flat. The sea is about 13 miles higher at the equator than the poles, for instance. Sea level rise varies with position, as well. That is how the average sea level can increase but nowhere becomes flooded.

    • Fluid in a rest state will displace laterally in a container. The rub is that the ocean is not a giant glass of room temperature water. Lots of different external forces are acting on it constantly–it’s never in a rest state.

    • No it’s 57% one for each State of the USA, and one for each gender not counting hermaphrodites.

      g

  4. Wait until they figure out that it is just like the Gilligan’s Island episode where Gilligan’s kept moving the professor’s gauge stick

  5. Can’t wait for UAH and RSS to take their 1979-onward satellite data and use it for 1879-1978 conclusions about temperature trends.

  6. One bright day in the middle of the night,
    Two dead men got up to fight.
    Back to back they faced each other,
    Drew their swords and shot each other.
    If you don’t believe the story’s true
    Ask the blind man, he saw it too!

    • At the risk of boring people (sorry), I’m reminded of my dear departed Mother’s variation – perhaps predated to the 19th Century!?! An unexpected summary of the CAGW phenomenon:

      One dark night in the middle of the day
      A fire broke out in the ocean.
      A blind man saw it.
      A deaf man heard it.
      A man with no legs, ran to fetch the engine.
      The engine came with two dead horses, ran over two dead cats and half killed them!

  7. With the NOAA sea level rise maps showing worldwide variations in SLR, almost everywhere has subsidence or rise. How does one tell the difference, and sort out true SLR?

    • In real science, sea level is either regional or eustatic (globally apparent sea level change). Eustatic sea level change is when ALL (or at least all but the extreme exception) regional sea levels are all rising or falling, i.e. end of last glacial period. Otherwise, it is said that sea level is at stand still. The important thing to remember in this is that sea level is actually just a relative term, as the shifting of sediments and changes in ocean floor bathymetry are constantly changing the volume of the Earth’s basins — sometimes significant enough to cause eustatic change themselves.

      In pseudoscience, sea level is imagined as a quantitative measurement entirely due to the crysosphere, and the number given is derived by statistics and then said to be rising or falling compared to an arbitrarily chosen 19th century average. From that single basic misunderstanding and ignorance, there you have it, one branch of climastrology.

  8. Isn’t this a variation of trying to rationalize why the actual data is not as high as you hoped it would be?
    Will they now “adjust” the data to meet their expectations?

    • wait a minute…I’m in the market for a good cherry picker – I’ve loads of trees that need pruning! A good cherry picker would be very handy.

  9. As I was saying…. I spent some time at sea. Well actually I spent a lot of time at sea. To tell the truth I spent most of my working life at sea. The thing is this. A ship at sea, will develop an easy rolling action, and an easy pitching action. So in fact the ship sort of corkscrews. And of course everyone in the ship knows all about this and lives with it, easily and comfortably. Whether it is walking along a long, long deck, where the ship can be seen to be flexing longitudinally as well as corkscrewing, or eating the very fine soup they serve in ships, or sleeping soundly in a bed which is always arranged in a fore & aft position. But wherever, or whenever, we always experience sudden, unexpected jerks (even of mighty vessels) or shakings, or bl**dy great bangs, slamming of the forefoot down into an unexpected sea. You imagine the movement, you name it, all ships will have done it thousands of time before the idea entered your head. What is happening is that the sea is constantly moving up and down, and sideways, and whatever way it wills, without cease.
    When the great ships move, the sea moves equally and oppositely.

    • continuing “As I was saying”.
      When the sea moves in such unpredictable manners, how on earth does one measure the change in the sea level height? To within centimetres?

  10. It’s always “worse than we thought”. Clearly, the problem is in the thinking. Evidently thinking is not a strong suit for climate scientologists.

  11. How come with CAGW its ALWAYS worse than we thought? And yet meanwhile we enjoyed a beautiful summer here in Texas, the best since…well the end of the other El Ninos.

    One would think if EVERYTHING is worse than we thought, someone would have noticed without a (pseudo) scientific study!

  12. So our best and longest established measures are understating sea level rise but his new and short term measures are much better than the best. Say what? Rubbish!

  13. Ah so a glacier melts in the Himalayas or the Alps and the closest coast line has a “melt fingerprint”.

    FFS, maybe there is an LSD fingerprint on their brains, but pretending that there are measurable gravitational effects on regional sea level from glacier melt is laughable. Did they account for gravitational changes in groundwater, sedimentation, biomass, volcanism, and human infrastructure? I’d love to know what numbers they used to show the biomass-fingerprint for the Northern Hemisphere vs South, and what numbers did they use for Antarctic melt for that matter.

      • When Einstein developed his theory of gravitation, usually called general relativity, he found a problem. The universe, which he thought was static, could not be static according to his equations. Instead of predicting that the universe was changing, he modified his equations to introduce a cosmological constant that would support his theory. When physicist Edwin Hubble discovered that the universe was not static but was expanding, Einstein called his cosmological constant “the greatest mistake of my life”.

        And yet, I’ve never seen you admit any mistake, Mosh.

        To quote you, “Raw data is crap data.”

        How many thousands of times have you modified your data?”

        People who live in government funding glass houses shouldn’t throw stones.

      • Mosh has a point.

        The theory was put forward, and then we went looking for the data to support it.

        The most astonishing thing is, that while the theory was looking a bit dodgy in the beginning, it has turned out that all of our old, previously collected data was wrong, and has had to be adjusted.

        Everywhere we look, it is obvious that the data has NOT been keeping up with the theory, and armed with the knowledge of what the data should be, it is a relatively simple matter to find the faults.

        Even as we predict the dire theorized outcomes, and these are contradicted by actual events, we find it a simple matter to remodel the situation, and soon enough, we can come up with a new set of dire outcomes to match the observed results.

        It ain’t rocket science.

      • markx said:

        “Mosh has a point.

        The theory was put forward, and then we went looking for the data to support it.

        The most astonishing thing is, that while the theory was looking a bit dodgy in the beginning, it has turned out that all of our old, previously collected data was wrong, and has had to be adjusted.”

        If more people understood the logic behind that statement, we’d see a lot more genuinely skeptical thinking applied to both sides of the argument.

      • Mosh: Your link to changing values for the Hubble constant was fascinating, especially the error bars. We need to remember that statistics can only tell us about random error (in measurements), not systematic errors in converting those measurements into H0.

        I hope to see a plot of ECS versus time that declines. A factor of 2 would be enough.

      • Dear Reg: Edwin Hubble was an astronomer, not a physicist (though astronomers understand and work with physics). He discovered a systematic galaxy redshift proportional to their distance…but he never interpreted it as a redshift due to Doppler shift (of recession velocity, implying universal expansion). The Doppler shift explanation was a supposition, which crystalized into “settled science.” Hubble argued against it.

        For the rest of the story, read the work by Halton Arp.

      • Actually, Mosher, Einstein changed his theory because he didn’t like the conclusion. He DID NOT change any data.

        And, unlike some, when data came in that showed his personal belief was wrong, Einstein promptly admitted it.

        Face it, Mosh, not only are a lot of people smarter than you, they also tend to be honest.

  14. Putting this into perspective, the PSMSL tide gauge network shows an average sea level rise (SLR) of 1.4 mm per year – roughly the thickness of a dime. Based upon the results of this study, you’re looking at a rate of 1.7 mm per year or 0.3 mm per year difference – the thickness of a business card.

    Per PSMSL, most of the sea level rise is concentrated in the Baltic and Adriatic seas, South East Asia and the Atlantic coast of the United States, accounting for an average of 3.8 mm per year, representing 35% of global tide gauges. Sea levels were stable in 61% of gauges, and fell on average of 6 mm per year in the remaining 4% of gauges. All based upon gauges with long records.

    This begs a statistical question… Given that some adjacent tide gauges showed opposite sign of SLR. And given sufficient samples (there were approx. 725 gauges in the network at its peak), wouldn’t the central theorem apply, making the need to adjust for some selected locations, as this study does, unnecessary?

  15. “The data do not support our hypothesis. After a lot of head-scratching, we have developed a hypothesis about where to find data to support our other hypothesis. So our original hypothesis is supported by the data our hypothetical new method would have produced. QED.”

  16. If they are so concerned about an error of only 3 cm. or so over a considerable period, could they explain how they are scientifically, accurately and adequately measuring the annual average sea/ocean surface levels, even for the last 30 years or so, let alone for, say 100-250 years. Everywhere and to varying extents and variously at different times, the sea surface swells with the crossing winds, its level adjacent to land varies with the changing tides, the sea bed level varies over time due to subsidence, ocean currents’ scouring and even geological/volcanic actions, and the sea water volumes alter with the extent of ice in the Arctic and Antarctic. From this they somehow calculate to a fine degree local annual average sea level changes with some supposed high level of accuracy and consistency sufficient to provide credible, meaningful and “substantiated” sea level changes. Then they somehow separate out the minute sea level changes supposedly caused by global warming and climate change.
    Credible? Or am I somehow missing something, or misunderstanding something?

  17. I know what i would say to any geologist who presented me with a model which showed all the high points of a variable far away from any actual data point……..

    These alarmists have no shame.

  18. ”As it turns out, our best historical sea level records tend to be located where past sea level rise was most likely less than the true global average.”

    So they are going to claim to know what the ”true” average is even though they are quite happy to admit their incompetence up to now. The highest quality records show, that sea levels were actually not as bad as the exaggerated average figure, that was picked out of the air.
    What they really need to observe is, things just aren’t as bad as they think. The total opposite to their usual mantra.

    Eamon.

  19. ”As it turns out, our best historical sea level records tend to be located where past sea level rise was most likely less than the true global average.”

    By the same token, most global warming takes place where there are few or no thermometers.

    You’ve just got to love climate “scientists”…

  20. “We were looking in the wrong places” is synonymous with…”We don’t understand this well enough to know where to look, but we still say the science is settled anyway”

    “Its worse than we thought” likewise means, “we don’t understand the mechanisms of thermal changes on our planet”

    To say the above is not a scientific analysis can be psychologically analyzed as DENIAL.

  21. Nope. Garbage paper. Locational SLR has to be corrected for local vertical land motion. GIA and tectonics. See essay PseudoPrecision for specific examples. There are about 40 long record tide gauges with a diff GPS land motion correction within 10 Km. (Admittedly, NH biased but for a couple in Australia). These show about 2.2 mm/yr SLR, and no acceleration in the past century. 1.4 to 1.7 is TOO LOW because estimated from an erroneous land motion uncorrected method. Does not close, on the low rather than high side. Closure is ~2.1-2.3 mm/yr. And still no SLR alarm. See recent SLR closure post at CE.

    • 1.4 to 1.7 is TOO LOW because estimated from an erroneous land motion uncorrected method.

      Good point. Let’s add in another factor to be considered… Some studies found that siting of many sea level gauges were close to larger cities for convenience sake where subsidence was more pronounced for geographic reasons (humans like to live in deltas, estuaries, and other similar geographic features where fish are easier to catch and land sinks) and could overrepresent the rate of sea level rise. The sinking city of New Orleans is a good example.

      In my own analysis, I found considerably more than 40 records that were statistically viable but agree that the most pristine contiguous records were around 40. Irrespective, wouldn’t it make sense, if you’re going to make adjustments, to also include an adjustment for population density or area GDP? In such case, the adjustment would result in a lower rate of SLR and make 1.4 to 1.7 a plausible figure as the adjustment would be 0.3 to 0.4 (per my calculation) decrease in SLR from raw measurements across the board.

      All to say, there’s lots to look at and consider such that I don’t think we have the bird in hand quite as well as these researchers seem to think.

      • I didn’t mean to imply you’re wrong. I agree. It’s a garbage paper as it is too exclusionary to other confounding factors.

  22. As it turns out, our best historical sea level records tend to be located where past sea level rise was most likely less than the true global average.

    I stopped reading right there. It’s astounding how they can refer to the “best historical sea level records” and then say they don’t represent the true global average in the same sentence. In other words, the data you don’t have but confirms your model is better than the actual data that you do have. WTF?

  23. So, if I read this correctly (debatable after two Harpoons) the sea rises LESS where the ice is melting and MORE in some unspecified location, thereby allowing us to fudge sea level rise upwards by an unspecified amount? I give up. Science is dead. Time for a third Harpoon.

  24. The late John Daly got interested in this area when he found sea level markers in Tasmania made by Captain Sir James Clark Ross in 1841. ( see: http://john-daly.com/ )
    That marker is now at least a foot above the current sea level, so unless Tasmania is experiencing impressive geostatic inflation, there is no rise in southern ocean sea levels, rather the contrary.

  25. Was there supposed to be a link to the actual research paper at the bottom of the article?

    Anyway:

    “Dr. Philip Thompson, associate director of the University of Hawai’i Sea Level Center in the School of Ocean and Earth Science and Technology (SOEST), led the study.

    “It’s not that there’s something wrong with the instruments or the data,” said Thompson, “but for a variety of reasons, sea level does not change at the same pace everywhere at the same time. As it turns out, our best historical sea level records tend to be located where past sea level rise was most likely less than the true global average.”

    Dr, Philip Thompson seems to have his facts confused with his fantasies.

    Surely, if they were serious about long term tide records, China and Japan must have some.

    But I’ll bet those long term records don’t agree with Dr. Thompson’s fantasies either. They could always send more teams of student researchers with blow torches to Greenland, during the winter.

  26. And if the data does not support your hypothesis you can always use a model. Models are very accommodating.

  27. I don’t see any evidence that aqny of these global sea level observers have bothered to make any corrections for the effect of water held in storage on the observed sea level. Chao, Yu, and Li (Science April 11, 2008) did just that. They checked out all available data on sea level rise and found the curve to be irregular. Then they corrected the available data for water held in storage by all reservoirs built since the year 1900. The effect was immediate: sea level curve became linear for the previous eight years. If nature has decided to keep something constant for eight years it is not likely to change anytime soon. And the slope of this linear sea level curve was 2.46 millimeters per year. This takes care of Al Gore’s fantasies and a few other extremists. But it is still a bit more than satellites have been showing. Projected for a century ahead it predicts a sea level rise just under ten inches. I am willing to bet that when the century mark is reached it will be no more than an inch off from their projected target.

    • Arno I’ve been studying sea level many, many years, and have a great deal of respect for one aspect related to those people known as ‘the greatest generation.’

      They were scientifically very, very rigorous, in general.

      Your remarks remind me of these people a great deal; highly intellectually developed, your capacity for remark on science is high quality in my opinion and I’ve read the scientific work of hundreds of men from all our classic scientific forbears to the period encompassing this era.

      One of the things notable about the work of a real applied scientist is he has a knack for knowing the level at which scientific information passes swiftly through (to) many people.

      When you work in applied systems and physical sciences for a long time you learn a lot about the typical human primate and how it it processes information. Contrary to the evolutionary paradigm we all know very well the psychology of a primate isn’t the highly honed, extremely rigorous steel trap, that one imagines is needed to ‘rise to the top of the evolutionary ladder through cunning and persistence.’

      A primate is the very antithesis of both these in many aspects and it creates among real applied scientists, even at high degrees of detail-oriented complexity, the natural tendency to try to drive down the level of apparent complexity in what they say.

      Over several years, in almost every applied scientist one will ever meet, this winds up being the kind of person who can explain exceptionally complex subjects, even to small children.

      One of the marks of the ‘climastrologist’ is the inability to communicate anything clearly, because his so-called science, is nothing but pseudo-scientific trash.

      Your words remind me of how few real applied scientists even bother coming near the climastrology scene due to the abysmally low level of intellectual rigor in communicating physical and mathematical principles to a wide audience.

      GHE nuts are legendarily obtuse, unable to process even simple standard physics, then having their faked mathematics and fake physics revealed as easily as tearing newspapers off an old window so light comes into a room.

      We can see the public’s low tolerance for GHE nuttery. To this very minute each and every one who tries to spread the poisonous pseudo-science wish they could somehow turn back the tide of people finding out how ignorant, and just plain inane, their scam was, is, and will be to every honest atmospheric and physical scientist who discovers it’s fakery and chicanery.

      All of us who are real applied atmospheric chemists and radiation scientists applaud you as well as all other scientists associated with publishing and academia, who stood at the gates and endured the despicable slings and arrows of the poison pseudo-science spreading GHE nutters.

      We cheer each other in our hearts each every day; we applied scientists whose bread and butter for – practically speaking all our lives – are fully behind those of you who stand with your shoulders to the door of science; and for myself, I teach my children and one day will be teaching my grandchildren the ins and outs of the fraud, known as GHE.

      The holiday season arrives yearly and we in the working scientific world wish each and every one of the skeptics who tell the truth about the fakery known as GHE warming,

      the warmest and finest of holiday seasons, with success and happiness wished upon you each quiet moment when we measure who our friends are,

      vs our antagonists in pseudo-science.

      You are one man I’d like to wish those warm holiday greetings toward and upon and know you are held in high esteem by many others around the world for your clear thinking and erudite observations on predictive science, vs the chaotic scrawls purported to be ‘projections not predictions’ by the Piltdown Movement of the late 20th and early 21st centuries.

    • It is possible that coastal Egyptian mummies may not be able to escape the rising seas. Oh, wait now…..no, they’ll make it.

  28. “This is really important, because it is possible that certain melt fingerprints or the influence of wind on ocean circulation might cause us to overestimate past sea level rise”

    Typical. What exactly constitutes a “fingerprint”? One that might “cause us to overestimate past a sea level rise?

    Might? Fingerprint? This passes for science? Here’s a clue; in the sciences, we don’t discuss “might” outside the pub.

  29. Ahhh don’t worry. I am sure that NOAA will make adjustments to the sea level rise since this paper gives them an excuse to do so. Once NOAA is through adjusting all the sea level measurements for the past century or more, we will find that what really happened is the we have accelerating sea level rise now and it really is worse than we thought.

  30. Did they reference any data from Nils-Axel Mörner?
    As far as I am concerned, he is the sea level rise expert, as he has data and more data than any of these guys. Do they use any of his data in their paper?

  31. I can’t remember which one it was but there was an Irish comedian who had a joke about the Irish water ski team looking for a lake that sloped to practice on. Maybe this “scientist” has found the ocean equivalent!
    Once the levels have been adjusted for this new research I’m sure we’ll find we’ve all been living underwater for years and just didn’t know.

    James Bull

  32. “We [CSIRO] have used a combination of historical tide-gauge data and satellite-altimeter data to estimate global averaged sea level change from 1880 to 2014. During this period, global-averaged sea level rose about 23 cm, with an average rate of rise of about 1.6 mm/yr over the 20th Century. The sea level record indicates a statistically significant increase in the rate of rise from 1880 to 2014.”
    http://www.cmar.csiro.au/sealevel/sl_hist_few_hundred.html

    But now let’s look at the geology of Hallett Cove a southern suburb of Adelaide in a very old, weathered and stable continent-
    http://www.sa.gsa.org.au/Brochures/HallettCoveBrochure.pdf
    and what do those very special rocks and the science reveal to us all-
    “During the Recent ice age about 20 000 years ago, sea level was about 130 metres lower than today and South Australia’s coastline was about 150 kilometres south of where Victor Harbor now is. The ice cap started to melt about 15 000 years ago. Sea level began to rise and reached its present level about 6000–7000 years ago.”

    Simple arithmetic shows us that could be an average sea level rise of 16.25 mm a year for EIGHT THOUSAND YEARS. Over TEN times what the CSIRO reckon the globe experienced over the 20th century. And these girlymen with the vapours are now quibbling over whether it was an average of 1.4mm or 1.7mm a year over the twentieth century?

    Conclusion: Western civilization should be seeking the best deal we can get from ISIS now.

  33. I look at the graphic in the article and note that the highest change rates seem to be banked up on the eastern side of continents whick for a planet that rotates towards the east and has all sorts of dynamic, oscillating phenomana like Rossby Waves and such like that hardly seems like anything to get too excited about. It could just as likely be associated with some tiny fluctuation in the moon’s orbit I suppose. As a pattern it does not seem to be likely linked to CO2 concentration…. or am I just being too skeptical?

  34. “As it turns out, our best historical sea level records tend to be located where past sea level rise was most likely less than the true global average.”

    Am I missing something ?

    This logic seems to be counter-productive to the AGW mantra. If SLR was less in the past it would create a false higher trend in more recent data.

  35. 82 comments so far – and I am surprise to discover that the word acceleration only features on 3 occasions.
    It is not the rate that is deduced from the long term seal level gauge records which should be of principal interest – it is the total absence of any change in the rate. i.e. the absence of acceleration of sea level rise.
    Clearly, the coastal sea level gauge monitoring stations were not intended to provide an absolute measure of that the surface of the sea was doing over all portions of the globe.
    They are not representative of the “average” sea level rise rate. At least, it would only be a coincidence if they were.
    But – we can be damned sure that they accurately inform us as to whether the rate of sea level rise has changed i.e. if significant acceleration has occurred. And what they tell us is – it hasn’t.
    The great deception is to focus everybody’s attention on the actual rate, such that nobody thinks to consider that the rate – as derived from all long term sea level monitoring stations – is more or less the same as it appears to have been back at the near end of the 1800’s.
    If anything – it is really quite astonishing to note just how exactly constant that rate has been,
    As shown by the average of all the high long term quality gauges.
    Warming catastrophists need acceleration. They can’t blame CO2 for a rate that existed in 1880 and persists to this day.
    https://wattsupwiththat.com/2014/07/16/latest-noaa-mean-sea-level-trend-data-through-2013-confirms-lack-of-sea-level-rise-acceleration-2/

    • Frog: If you look at the millennial record of SLR, you’ll see that the long slowdown in SLR after the end of the last ice age effectively reached zero (well below the 20th century’s 1.7 cm/decade) about 4000 years ago. So, there was an increase in SLR associated with the end of the LIA, which continued during the 20th-century warming that followed (some of which as due to rising GHGs).

      Detecting change in sea level is very difficult, especially with tide gauge data. One needs to perform a multiple linear regression of the data to a quadratic equation: h = at^2 + bt + c. That will give you values and confidence intervals for the parameters a, b and c. When the confidence intervals for a (acceleration of SLR) and b (rate of SLR) are bigger that their values, then we can’t say with any confidence whether OR NOT there is any acceleration in rise (a) or any rise at all (b). In the case of data from individual tide gauges, you need about 50 year of data to make the confidence interval for the rate (b) smaller than the rate. Detecting significant acceleration from tide gauge data (its confidence interval is smaller than a) is impossible. The satellite record is also short enough to make significant acceleration undetectable. In both cases, that doesn’t mean acceleration is zero. it just isn’t significantly different from zero. It is difficult to combine records of different length: A 100-year tide gauge record with an AVERAGE rate of SLR of 1.7 cm/decade can’t be compared with two decades of satellite data with an AVERAGE rate 3.0 cm/decade, because these averages don’t cover the same period. Nevertheless, the absence of evidence for significant acceleration does not prove acceleration is zero.

      The important question is: How big does acceleration need to be for threat of acceleration to be important to policymakers? If one believes the satellite record, SLR is about 1 inch/decade, not very different from what was experienced in the 20th century. Alarmists claim that sea level could rise 1 m by the end of the century. That would require an acceleration in the rate of SLR of 1 inch/decade/decade. In other words, the rate of SLR will need to be 2 inch/decade a decade from now to be 1 meter higher by the end of the century. So it currently doesn’t look like we need to be worried about the alarmist scenario today – and we will still have decades to prepare. Unfortunately, the data is noisy enough that even if SL were rising at a rate of 2 inches/decade in 2025, it would take another decade of noisy data to be sure. There is a lot of over-confidence on both sides of this issue.

  36. The effect of meltwater from grounded ice on sea-level is more complex than you might expect. (There’s nothing particularly new about this, and it’s long been taken into account when calculating globally averaged sea-level, so it’s not “worse than we thought.”) Here’s a good tide gauge which is not significantly affected by proximity to Greenland or PGR; the sea-level trend there is very close to the global average:

    If grounded ice melts and the meltwater finds its way into the ocean, of course it raises average global sea-level. But it also slightly changes the mass distribution on the Earth’s surface, which changes local gravity fields, which changes the distribution of water in the oceans, and has uneven regional effects on sea-level.

    Suppose that a substantial amount of ice were to melt from the Greenland Ice Sheet, and run into the ocean. The gravitational attraction by which the ice sheet attracts the surrounding ocean would be reduced, which would cause the ocean to recede in the vicinity of Greenland. It has been calculated by people who presumably know what they’re talking about that in the vicinity of Greenland (and apparently as far away as parts of Europe) this effect would exceed the rise in sea-level due to water added to the ocean, so that sea-level at Greenland and the surrounding region would actually fall, rather than rise, as the ice sheet melted.

    But that water which flows away from Greenland would also add to sea-level elsewhere, causing sea-level elsewhere around the globe to rise a bit faster than you would expect from a simple calculation from the amount of water added to the ocean.

    Here’s a short video from Boston University’s Maureen Raymo, explaining it.

    Additionally, the weight of the Greenland ice sheet on the ground beneath would be reduced, so the ground would then slowly rebound upward (“post-glacial rebound“), which would cause the sea-level at Greenland to continue to fall (or to rise at a reduced rate) for thousands of years into the future. That rebound (PGR) would, in turn, also change the gravity field, and thus the water distribution in the oceans, which would presumably reduce the rate of local sea-level fall near Greenland.

    Harvard’s Jerry Mitrovica explains it in greater detail here (after unfortunately spending 13½ minutes bludgeoning straw men, and just before erroneously conflating tide gauge and satellite data). Unfortunately, the video’s owners are censoring commentary on YouTube. They “fake-approved” but hid (“ghosted”) my critique.

      • Pretty lousy video – the Greenland ice sheet isn’t floating in the ocean.

        According to Wikipedia, the volume of the GIS is 2,850,000 cubic kilometres. Its mass is 2.85*10^16. The mass of the Earth is 6*10^24 according to the same source. So the ratio of these mass is 2*10^8 : 1 Given the inverse square law, something would need to be 14,500 times closer to the GIS than to the Earth to feel an equal pull (from the force of gravity) down toward the center of the earth and horizontally towards the GIS. Calculus tells us that spheric objects exert a force of gravity as if all their mass were located at their center, or 6371 km from the surface of the Earth. Let’s ignore the problem calculating the effective center of mass for the GIS; let’s simply hypothesize that it acts like a sphere in the middle of Greenland at sea level. So, 1 km from the center of mass of the GIS, the pull (acceleration) of gravity from the GIS will be 44% of that of the Earth or 0.44 g. 10 Km away it will be 0.0044 g. 200 km away (near the coast?), the acceleration will be .00001 g (10 ug). 2000 km away (Scotland?), the acceleration will be 10^7 g (0.1 ug).

        If there were no GIS and Greenland had the density of water, the ocean near Greenland coast would be “flat”. With the GIS, it should have a slope of 1:100,000 or 1 cm/km or 1 m/100 km. That is a fairly substantial slope. Near Scotland, the slope would be 10 cm/100 km. These values are non-trivial compared with SLR of about 2.5 cm/decade

        Like it or not, the gravitation force from the GIS appear to be pulling a significant amount of water uphill towards towards Greenland.

  37. How do they know it’s underestimated if they don’t have measurements for higher than average places?? Doesn’t make any sense, and so can only be unsubstantiated conjecture.

  38. Who knows the exact average incidence of the seafloor up or dowliftings (sometimes on very large areas) due to huge tectonic forces on the sea level rise ?
    Isn’it a too easy answer to say that the balance between ups and downs is probably ~ 0

  39. “The investigation concludes that it is highly unlikely that global average sea level rose less than 14 centimeters during the 20th century, while the most likely amount was closer to 17 centimeters.”
    I thought the rough guide we’d been using for some time was 2-3 millimetres per year, which would be 20-30 centimetres per year, so the conclusion of the paper is that global sea level rise is LESS than I thought.

    The thing that bugs me is that they are basically saying that the historic record is incapable of detecting something that MIGHT have happened therefore it DID happen. Have I got that right? Isn’t this a case of absence of evidence being taken as evidence of presence?

    If they are right, and the sea level is higher in places we aren’t interested in, does it matter to human society?

  40. As it turns out, our best historical sea level records tend to be located where past sea level rise was most likely less than the true global average.”

    translates to

    “We neither have data nor clue of what we are talking about. We’re standing here empty handed.”

  41. This paper is really just an academic tempest in a teapot. Statements like this: “…the longest and highest-quality records of historical ocean water levels may underestimate the amount of global average sea level rise that occurred during the 20th century” presuppose that the most important metric is “global average sea level”, which I take it is some average height of the ocean surface relative to the center of the (non-spherical) earth, as if that can actually be measured to sub-millimeter accuracy.

    But isn’t the only measure of sea level of real engineering or human significance the local measurement of sea level relative to land that people occupy? And isn’t that exactly what’s been measured by tide gauges for centuries–said measurements showing a constant rate of sea level rise?

    Academics can speculate and pontificate ad nauseum about complex motions of land, ice, and water which lack empirical support but somehow “might” or “could” magically deliver the observed zero acceleration of tide gauge readings, but so what? Occam’s Razor still applies. If tide gauges show no acceleration in sea level rise, there is no observable impact of CO2 on this most important metric, and no rational basis for a belief that expensive reductions in CO2 emissions would reduce nonexistent acceleration in sea level rise near land that humans occupy.

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