Sea level rise: Plenty of time for Noah to build the Ark

Guest essay by Albert Parker

We may consider all the tide gauges in the latest PSMSL survey of relative mean sea level secular trends (http://www.psmsl.org/products/trends/trends.txt ). The population changes year after year, and since 2015, also the method to compute the rates of rise has changed. As PSMSL says “Please note that we changed the method of calculating relative sea level trends in 2015. The trends displayed here are not directly comparable with any calculated before that date.” So, we will focus only on this survey.

The survey includes 722 tide gauges, some of them having not enough data to infer any reliable trend. The global data set has a naïve average rate of rise of 1.39 mm/year, maximum value of +10.25 mm/year and minimum value of -17.63 mm/year.

As we know the short and incomplete records overrate the relative rate of rise of sea levels, we may then consider subsets.

  • If we consider all the tide gauges that started recording before 1934 (S1) this subset of 158 tide gauges has a naïve average relative rate of rise of +0.03 mm/year, maximum +6.75 mm/year, minimum -8.09 mm/year.
  • If we consider all the tide gauges with at least 70 years of recorded data in 2014 (S2) this subset of 157 tide gauges has a naïve average relative rate of rise of +0.08 mm/year, maximum +6.75 mm/year, minimum -13.22 mm/year.
  • If we finally consider all the tide gauges with at least 60 years of recorded data in 2014 (S3), this subset of 212 tide gauges has a naïve average relative rate of rise of +0.41 mm/year, maximum +9.41 mm/year, minimum -13.22 mm/year.

The longer subsets may serve to assess the presence (or absence) of an acceleration, as the relative sea level rates of rise become significant only after the minimum 60 years of data are recorded. The different values only reflect the different populations, with more tide gauges recently being established in areas subject to subsidence rather than uplift. The subsidence of the instrument is still the most relevant component to sea level rise.

What we learn from this survey? The sea levels are not rising, but rising and falling. And in the best “spots” along the world coastlines where the sea level rises are measured and not computed, the naïve average rate of rise is a pretty constant value and a quite small value.

These naïve average relative rate of rise translate in a naïve average sea level rise over the first 15 years of this century no matter the anthropogenic carbon dixoide emission of a little bit less than half a millimetrie to little bit more than one millimetre in the 158 or the 157 long term tide gauges S1 and S2, or at the most in 6 millimetrs in the 212 tide gauges S3 satisfying the minimum requirement of 60 years to infer a reliable trend.

Figure 1 below is the histogram of the S2 data set (tide gauges with more than 70 years of recorded data), image from the Wessa online facility.

The naïve average is practically zero, somewhere the sea level rise, somewhere else the sea level falls. We do not need more and more layers of burocrats and more and more taxes with the excuse to save the world from the rising seas because we burn carbon and hydrocarbon fuels.

image

Wessa P., (2015), Histogram (v1.0.15) in Free Statistics Software (v1.1.23-r7), Office for Research Development and Education, URL http://www.wessa.net/rwasp_histogram.wasp/

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79 thoughts on “Sea level rise: Plenty of time for Noah to build the Ark

  1. ..Mr. Parker…spelling error ??

    ” These naïve average relative rate of rise translate in a naïve average sea level rise over the first 15 years of this century no matter the anthropogenic carbon dixoide emission of a little bit less than half a millimetrie ” = millimeter ..??

    • for those of us who can’t easily convert mm to inches, how about putting both in your posts. The vast % of Americans are in the same boat and converting mm’s to inches would serve a good purpose- – -plus exhibit how tiny the rise is- – –

      • Ok, I am an Aussie, there are 24.5 mm in an inch or to put it in mechanical engineering terms there are 40 thousands of an inch to the millemetre. I hope this helps.

    • Those gauges are not reasonably geostationary. Uplifting either from glacial isostatic rebound (e.g. Portland, Maine) or tectonic uplift (e.g. Juneau, Alaska). Essay PseudoPrecision.

      • Isostatic uplift speaks to the complexity of calculating something like a global sea level. In other locations you’re talking aquifer depletion and subsequent deflation, or river delta sediment contributing to gravimetric drag, or even huge earthquakes in recent years that have realigned the ocean floor, thereby changing the shape of the “bowl” being measured. Such calculations are just as reliable as dendrochronology.

      • I live in the Tidewater area of Virginia. Our politicians are very concerned with Sea Level Rise (SLR). The Navy is concerned that the Big Naval base in Norfolk will be underwater soon. This is all blamed on CAGW. It is never reported in the press or by our politicians that the area is sinking into a massive impact crater that hit the mouth of the Chesapeake Bay 35 million years ago. Below is an excerpt from the USGS Fact Sheet 049-98. Note that the Fact sheet mentions that the shoreline of Virginia was near the Richmond area.

        Maybe if we stop burning fossil fuels the subsidence will magically stop.

        USGS Fact Sheet 049-98
        PAGE CONTENT
        Bolide Impact

        Figure 1. Location of bolide impact and of shoreline when bolide hit.
        A spectacular geological event took place on the Atlantic margin of North America about 35 million years ago in the late part of the Eocene Epoch. Sea level was unusually high everywhere on Earth, and the ancient shoreline of the Virginia region was somewhere in the vicinity of where Richmond is today (fig. 1). Tropical rain forests covered the slopes of the Appalachians. To the east of a narrow coastal plain, a broad, lime (calcium carbonate)-covered continental shelf lay beneath the ocean. Suddenly, with an intense flash of light, that tranquil scene was transformed into a hellish cauldron of mass destruction. From the far reaches of space, a bolide (comet or asteroid), 3-5 kilometers in diameter, swooped through the Earth’s atmosphere and blasted an enormous crater into the continental shelf. The crater is now approximately 200 km southeast of Washington, D.C., and is buried 300-500 meters beneath the southern part of Chesapeake Bay and the peninsulas of southeastern Virginia (fig. 1).

      • changing the shape of the “bowl” being measured
        =================
        the ocean doesn’t end at the sea floor any more than a river ends at the river bottom. rivers and oceans are simply places where the water table is higher than the land.

        the oceans exist because water cannot sink into the earth’s interior. instead it turns to steam at the mantle boundary which holds the oceans above in place.

        the nonsense in measuring sea level is the assumption that the ocean basins are impermeable containers for sea water. without a hot interior, the oceans would have long ago drained away to deep within the earth.

      • Yes, but without a detailed study we can perhaps estimate that biases up and down average out. More important, tide gauges are where people live and are most affected. We could call the mean SLR 50 m per year, but if the tide gauges where everybody lives only show 1.4 mm per year, then this is the reality we are experiencing.

      • dendrochronology is very accurate
        dendroclimatology is a little bit accurate
        dendro-thermometers are worthless

      • Maybe it should be spelled burrocrat since they can be such stubborn mules.

        +1
        Although I was thinking “burro-crat” because they’re almost all a—es.

      • Hmmmm.
        Some, maybe, merit a terminal papa, not tango.

        Yet there are fine ones too.
        My good lady and I had a – smallish – problem at the local hospital, and the intervention of one ‘bureaucrat’ sorted what (potentially) could have become a significant problem – in minutes!

        Auto

  2. We do not need more and more layers of burocrats and more and more taxes with the excuse to save the world from the rising seas because we burn carbon and hydrocarbon fuels.

    Also, Jericho, the bibilical city founded 11000 years ago, is 258 meters (846 ft) below sea level. Should the citizens of Jericho be worried?

    • Possibly all the ice that would melt as a result of the interglacial has been turned into water by now and, therefore, the increase is infinitesimal over the last 60 years. Perhaps Jericho will be habitable again at the start of the next interglacial in around a 100,000 years time.

  3. So the best evidence shows the lowest sea level rise. I do wonder if the trend that newer gauges show the most rise has a selection bias–that people worrying about rising sea level are more likely to install and monitor a gauge.

  4. Sea level rise must be understood within the context of temperature rise.
    Manhattan remains above sea level only because the tide gauge data has not been adjusted yet. Once adjusted by NOAA we will realize that sea level rise is “worse than we thought” and the evacuation of New York will begin.

  5. Here in the US, people seldom realize that our capitol city, Washington DC, is a seaport. Shipping crosses the Chesapeake Bay, and goes up the Potomac river. If people knew that Washington DC was vulnerable to sea level rise, there would be a massive undertaking to melt the Antarctic ice cap.

    • I’ve been personally calling for every concerned person in the world to flush their toilet at precisely 12:00 pm GMT on May 1st for exactly this reason. Together I believe we can flood both London and Washington D.C. in a global protest. I call it the “Flush the Bureaucrats” day.

      • I’m in. Got it on my calendar, Bartleby, marked ‘Good deed for the day… flush toilet.’

    • Nah! That would screw up the whole country, or at least the East Coast.

      Just dam the outlet of Chesapeake Bay al let the water from the Potomac turn Washington back into the swamp it once was (still is).

  6. No matter the record length, the only valid gauges to sample are those that are reasonably geostationary. The rest reflect shoreline uplift or subsidence. There are only between 70-80 of these globally with sufficiently long records to be useful. Originally determined by geology and reference to other gauges. Can now be done with some precision by differential GPS. Depending on the set sampled, the SLR works out to about 1.8-2mm/year. The sat altimetry number without GIA is about 2.8-3mm/year. The discrepancy is in part Sat accuracy (waves, humidity affecting signal timing, instrument drift [Jason 2 spec was randomly notnmore than 1mm/year]) and in part because measuring the entire ocean rather than shorelines. It is ‘known’ high because presents the closure problem: Sat SLR is higher by about 1/3 than the estimated sums of ice sheet mass loss plus ocean thermosteric rise. Former from IceSat and Grace, latter from ARGO. The new GIA estimates for Antarctica mean the corrected GRACE estimate shows less to no mass loss (details at Climate Audit). That makes the closure problem worse. There is no closure problem with a 2mm geostationary tide gauge when the new Antarctica estimates are used (IceSat, corrected Grace). Meltwater ~1.5 plus thermosteric ~0.6, total ~2.1. Close enough.

    • “Depending on the set sampled, the SLR works out to about 1.8-2mm/year”
      ========================================
      Is this sans the meaningless to SL adjustment for the ocean basins sinking.

      Also, as I pointed out above, Tide gauges are where people live, and if you are determining probable impacts and costs, then tide gauges are by far the more accurate data.

    • There are two distinct things: the science of “where is the water and what is it doing” and the Scare of “the great cities of the world will drown!” For the scare, which is about shore line movement and not really about sea levels per se, the tide gauges are practically the only thing that matters and whether the land is rising or falling as such is of no interest. If the local sea level is rising fast, the Scare is true there, even if the global sea level is falling. For the question of whether my town is at risk, I don’t give a continental what the sea level is doing anywhere else. Failing to distinguish the science from the Scare has led to much confusion. For the science, ristvan is right. For the Scare, he’s very wrong. For the safety of your town it is only the difference between land rise and sea rise that matters, and that is what all tide gauges show.

      • How true, how true. But, that does make predicting the scare a bit difficult. All you have to go on is the history. And, you then have no way to tie it to CO2, or whoever/whatever the current Boogie man is.

    • > Can now be done with some precision by differential GPS.

      Rud, I’m not trying to be picky, but I’m genuinely curious. Differential GPS is quite remarkable. I believe that it works by comparing the phase difference between satellite signals received at two receivers — a target and a reference. Think of it as very fast, very accurate, surveying without the folks wandering around with sticks and obscure optical instruments and waving their arms a lot.

      Unfortunately, it is subject to many of the same constraints as surveying. Most important, you can’t use it to measure elevation change unless you know the rate of elevation change at the reference. Which is pretty much impossible given that everything on the planet’s surface seems to be moving constantly.

      So, I think to measure elevation change at a tidal gauge, I think you need to do it the old fashioned way. Plant a GPS receiver with all the corrections enabled, then make millions of measurements over a long enough time base that the many small uncertainties (hopefully) average out. Tangentially, you could presumably use differential GPS to do your measurements at a more convenient and secure location — say the backyard of the nearest pub — then correct for any differential GPS measured difference in elevation change rate between the gauge and the pub.

      I’d like to be wrong about that. If I am, please let me know.

      BTW — as far as I know everything else in your comment is correct. And furthermore the 50% difference between satellite and everything else is, I believe, unique to Topex-Poseidon. IIRC the last paper I saw on the now defunct ERS instruments came in around 2mm/yr, but with a very large error margin due to uncertainties in tropospheric delay models.

  7. Those places with tectonic uplift, like Seattle, Anchorage should be worried, very worried.

    The last major movement of the Juan de Fuca plate was in January 1700. It may also be associated with the Tseax volcanic cone in BC Canada. Geologists believe the the Tseax Cone could reawaken at any time. The previous eruption has been estimated at 1325 AD.

    The major slip of the JdF plate happens about every 300-500 years. When it does again, Seattle and every community in the Puget Sound, as well as north to Vancouver and around around Vancouver and Victoria will be devasted by the ground lateral movements and will drop vertically 3-8 meters in a matter of minutes. The tsnami that will comes ashore within 20 minutes will look like those videos of the great 9.0 Tohoku earthquake in 2011.

    Unlike CAGW, this disaster will happen.

    • Cascadia fault. Portland to Vancouver. 700 miles. Now overdue based on average of past several quakes. FEMA ‘optimistic’ planning is 100,000 fatalities, at least 1 million displaced if whole fault goes rather than just a portion. Both quake and tsunami likely worse than Tohoku. Japanese have written records of when the tsunami hit all of eastern Japan after the last (Jan 26, 1700, estimated 9.0) quake. From which Japanese records it has been deduced that the last quake did indeed involve the entire length of the fault.

    • will drop vertically 3-8 meters
      ==================
      still not enough to give me waterfront. 9 times out of 10 when a zillionaires waterfront house is swallowed up by sea level rise the crowd is secretly cheering.

  8. The USGS says sea level was 410 ft lower than today’s level at the LGM (about 21000 ybp). So the average sea level rise since then has been about a quarter inch per year. Looks to me like we’re well below that average.

    To me the interesting question is, will we ever be able to identify the “bottom”?

    • Much more recently SL was likely over one meter higher then it is currently. We have had several warm periods, warmer then currently.

  9. My property is at 15 feet above sea level only one mile from the Gulf of Mexico. I really don’t care about a few mm/yr sea level rise. Let them eat coquinas.

  10. It is OK to try to measure sea level rise, but it is unnecessary, as sea level rise follows temperature rise.

    This is a sea level reconstruction based on data from 1700 and on a model based on temperatures prior to that.

    But more importantly, we know that the rate of sea level change follows very closely the rate of temperatures change. This is an overlay of two official graphs. Bottom graph is IPCC AR5 WGI Fig. 3-14. “18 Year mean global sea level trends”. Top graph is “Rate of change of global average temperature” from the European Environment Agency, here:
    http://www.eea.europa.eu/data-and-maps/indicators/global-and-european-temperature-1/assessment

    So this is the overlay:

    As global average temperature increase is not accelerating, sea level rise is not accelerating either. There is no basis for any alarmism regarding sea level rise. We should be more worried about subsidence in heavily developed coastal areas.

    • the PSMSL tide gauges are not all located in areas of uplift. As Morner wrote, the glacial isostatic adjustment is local and not global. In the vast majority of the world coastline there is subsidence, not isostasy. As there is no average uplift of +3 mm/year in the 158 locations of the oldest tide gauges, then there is no geodetic sea level rise of +3 mm/year.

      • It is really irrelevant if sea level rise is 3 mm/year or 1.5 mm/year. The important thing is that it follows temperatures and thus it is not accelerating.

    • Most importantly here is that the ocean temperature rise lags the atmospheric temperature rise by centuries due to the massive difference in scale of total enthalpy between the two.Whatever humans do over the course of 2 or 3 centuries will not even move the needle in ocean temps or volume. Those who howl at the moon about ocean warming and acidification just can’t do math. Grant worms!

  11. Albert, thank you for all your work on this analysis. Unfortunately, the claim that the longest records have the lowest rate is heavily biased by an oddity, which is that many of the long-term gauges are from Northern Europe. That area is rising due to the removal of billions of tonnes of ice at the end of the ice age, so in many areas those tide gauges show radical drops in relative sea level.

    And when you average those out with fewer gauges from the rest of the world, you get lower rates.

    As a result, I fear that this study does NOT show what you seem to think it shows … you can’t simply average raw rates of relative sea level changes and get a valid number.

    w.

    • If you look at the list of the 158 tide gauges, they are not all located in Northern Europe …. Sydney has a sea level rate of rise of +0.65 mm/year but is not located in Northern Europe …. and Sydney has no uplift, but it is rather stable …. The GPS suggests a subsidence of 0.89 mm/year larger than the relative sea level rise

    • the histogram gives you the individual values …. the relative sea level rises are below the absolute satellite estimate of +3.2 mm/year in about 150 locations of 158 ….. now, not all the 158 locations are subjected to isostasy … conversely, the 8 are located in high subsidence areas as Galveston …

    • So the alternative is the use of proxies in the SH, or what?

      We already know that sea levels have been higher in the past than they are today — when is irrelevant to the fact that they have been. It’s only within the construct of fallible human belief that sea levels should be static because we’ve built right up to the water’s edge with our infrastructure, and then act surprised when Mother Nature gives us a wake-up call.

    • My understanding is GIA, aka post-glacial rebound is already taken into account… somewhere.
      https://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch5s5-5-2.html
      ‘Trends in tide gauge records are corrected for GIA using models, but not for other land motions’

      Now, I’m not positive whether ‘corrected’ here means the data for the tide gauges themselves, or the reanalyses. If it’s the latter, then it’s true that a new reanalysis (such as the one in this article) would be biased low by failing to account for GIA.

  12. possibly, the “best shot” for a “global” sea level rate of rise is the +0.4 mm/year in the 212 worldwide locations with more than 60 years of data. PSMSL has an online facility to locate these 212 tide gauges, and the most part of them are subjected to subsidence, not uplift, being quite far from the polar area

  13. more importantly, who cares of the geodetic sea level rise when you may have floods only where there is a relative sea level rise? around the world, there are very few spots with relative sea level rises higher than the satellite value. and only in areas of very high subsidence as Galveston

  14. The South Pacific Sea Level and Climate Monitoring Project developed as an Australian response to concerns raised by members of the South Pacific Forum countries over the potential impacts of the Greenhouse Effect on climate and sea levels in the region. In 1991, the National Tidal Facility (NTF) of the Flinders University of South Australia was awarded the contract to undertake the management of the project.

    Eleven monitoring stations were established in the Cook Islands, Fiji, Kiribati, Marshall Islands, Nauru, Papua New Guinea, Solomon Islands, Tonga, Tuvalu, Vanuatu, and Western Samoa, to provide a wide coverage across the Pacific Basin. Each of theses SEA Level Fine Resolution Acoustic Measuring Equipment (SEAFRAME) stations in the Pacific region are continuously monitoring the Sea Level, Wind Speed and Direction, Wind Gust, Air and Water Temperatures and Atmospheric Pressure.

    In addition to its system of tide gauge facilities, the Pacific Sea-Level Monitoring (PSLM) Network also includes a network of earth monitoring stations for geodetic observations, implemented and maintained by Geoscience Australia. The earth monitoring installations provide Global Navigation Satellite System (GNSS) measurements to allow absolute determination of the vertical height of the tide gauges that measure sea level.
    Data is here:
    http://www.bom.gov.au/pacific/projects/pslm/

    • the long term tide gauges of the South Pacific (as Sydney or Auckland) were providing data since almost 100 years when the pacific monitoring project started … and everybody knew the sea levels oscillate as the SOI with a periodicity of about 20 years … so what to do to defocus from the independent tide gauges run by port authorities? better to establish new tide gauges controlled by climate change monitoring projects, incidentally all starting record at the time of a valley of the peaks and valleys oscillations … and then start using the data from these novel tide gauges after few years … the perfect alarmist project !

  15. Satellite-measured sea level rise is being reported to a “precision” or 0.1mm, which is one part in 23+ billion. Impressive, if plausible.

  16. the reconstruction of global mean sea levels have been produced so far by cherry picking the individual tide gauge records of different subsidence and different start year to produce a continuously accelerating result by stacking not accelerating tide gauge records. The hot spots of positive sea level acceleration along the east coast of the US is what could have produced cold spot of sea level deceleration along the west coast of the US and Alaska. The naïve average is basically the average of everything. The cherry picking is the consideration of what is important for the narrative.

  17. Albert, Have you seen any of the claimed acceleration in the rate of sea level rise, particularly after 1945 when man’s CO2 emissions increased greatly? … or is 0.08 mm pa the dramatic impact of man?

  18. Hmmm “722 tide guages say…The global data set has a naïve average rate of rise of 1.39 mm/year,…”
    that’s 5.47244 inches per century…just what many experts have been saying for years…

  19. I don’t understand this article at all. It is vague, obscurely written, uses undefined terms, and is not put in context with other analyses of sea level rise.

  20. I do not understand how anyone can infer the sea is rising faster when what they are measuring is relative to the location it is measured at. All they can say for any one location is that the sea is measured as higher or lower to a specific spot, but one cannot infer the land didn’t change elevation as opposed to the sea level changing.

    I guess one could infer the sea level is rising faster if it accelerates everywhere by the same amount, or at least by a certain amount.

    The extraction of gas, oil, and/or water will impact land elevation. So will will continental drift, rising plumes of magma, and earthquakes. So will the rebound of large bodies of rock from glacial loads. So will natural or unnatural changes in river sediment, the settling of ancient sediment, etc.

    How the heck do you untangle all of these variables to come up with a meaning worldwide measurement of tiny accelerations in sea level rise? My guess is that they guess. LOL

  21. It is hard to make sense of all those varying limits as well as the fact that some gauges show a sea level drop. That is normal for formerly glaciated areas like Scandinavia, Canada and such inland locations like the great lakes. I personally like to stick with Chao, Yu anf Li that came out in February 2008. What they did was to correct all published sea level data for water held in all reservoirs built since 1900. When this correction was done they had a sea level curve that was linear for the previous 80 years. Its slope was 2.46 millimeters per year. Something that has been linear that long is not about to change anytime soon. 2.46 millimeters per year works out to just under ten inches per century. It is likely that the true centenarian sea rise will be close to ten inches, give or take perhaps an inch. Compare this to the twenty feet Al Gore pronounced in his famous movie that brought him the Nobel Prize. Twenty feet, he said, would wipe Florida off the map. He even showed a map of Florida under water and the Nobel Committee said, yeah, verrily, though dos’t know the future and deserve our prize for that.

  22. The question is not what is the average sea level rise from the tide gauges over the last 60 years, the issue is what is happening in the recent 25 years – since the adjusted satellite record says that sea level rise increased from about 1.4 mm/year to about 3.2 mms/year.

    The tide gauge database from PMSL is deliberately structured so that one cannot really get into the annual numbers and say what the tide gauges record is for 1992, 1993, 1994, …. 2013, 2014. This is what we should be concerned about.

    And then there is the issue of the local subsidence/uplift rates of each individual tide gauge station. Fortunately, this seems to be a relatively stable number over many decades if not centuries.

    Many of the tide gauge stations are now co-located with a GPS station that can nail down the local subsidence/uplift level after about 4 years of continuous operation.

    Sonel.org has been maintaining a database of these tide gauge / GPS co-located stations.

    For example, Sydney Australia, has a tide gauge recording 1.15 mm/year of sea level rise (and there has not been any recent or historical acceleration) and the co-located GPS station is saying that Sydney harbour is sinking by 0.89 mms/year. Thus the real sea level increase is only about 0.26 mm/year at Sydney.

    http://www.sonel.org/spip.php?page=gps&idStation=2405

    http://www.psmsl.org/data/obtaining/stations/196.php

    Let’s take a northern Europe example as Willis noted; FURUOGRUND on the Baltic Sea which has a tide gauge measuring -6.46 mm/year of sea level decline but the land is rebounding from the last ice age at a rate of about +10.58 mms/year so the net sea level rise here is 4.12 mm/year (one of the highest net sea level rise numbers).

    http://www.sonel.org/spip.php?page=gps&idStation=844

    http://www.psmsl.org/data/obtaining/stations/203.php

    Basically, one would really need to do this same thing for about 300 stations and then calculate what the net sea level rise really is for all 300 stations to get a really robust result. And then we need that data by YEAR. This is a lot of manual data entry and calculation.

    Sonel has calculated the net sea level rise from 1983 to 2013 (they will only provide 30 year averages) for 106 stations which have tide gauges and co-located-robust-data-GPS stations …

    http://www.sonel.org/-Sea-level-trends-.html?lang=en

    (one needs to play around here a little to figure out to download the data]

    AND …

    … the net sea level rise from these 106 stations is only 1.86 mm/year. [1983 to 2013 – which means the satellites can not possibly be correct at 3.2 mms/year.

    • “Sonel has calculated the net sea level rise from 1983 to 2013 (they will only provide 30 year averages) for 106 stations which have tide gauges and co-located-robust-data-GPS stations …”

      The 30 year averaging appears to be a 1st order attempt to handle ocean circulation patterns, wind patterns, etc. However, I’ll accept the number they derive for SLR when they get the same (corrected) reading from each gauge in their network within the accuracy and precision of the gauge. Until then they have neither defined nor adjusted for all variables other than SLR that may effect the readings. Until then they don’t know what they are actually measuring.

    • The PSMSL surveys (as the NOAA surveys) of relative sea level rises are extremely relevant.

      These surveys tell you where along the coast the sea levels are rising or falling, and if they are accelerating (just compare the relative rates of rise of different surveys in the same tide gauges where only few more years of data are added).

      What the PSMSL and NOAA surveys tell you is that almost nowhere there is a need to cope by coastal management with the rising seas.

      Where they are measured properly, the relative sea level rises are everything but dramatic and they are about constant.

      So the 2 meters sea level rise added everywhere in the United States as per the TMAC report are a disgrace for science.

      If somebody tell you that 2 m sea walls are needed along the west coast of the United States and Alaska, you may answer in Alaska the sea levels are mostly falling, and along the west coast of the United States and Alaska the sea levels are rising about 1 mm something on average … so it may take forever to make plausible the 2 m sea walls in Alaska and possibly 2,000 year in California, Oregon and Washington state.

      Please do NOT get trapped in the “absolute” sea level rise. You cannot know with accuracy the “absolute” sea level, and what flood the land is the relative sea level …

      final remark, just to be precise about Sydney

      I do not know where the claim the relative sea levels in Sydney are rising 1.15 mm/year.

      If you look at the PSMSL survey I proposed, it says +0.65 mm/year in Fort Denison 1 (longer) and +0.96 mm/year in Fort Denison 2 (shorter). The two tide gauges are leveled each other and overlapping, so you can make a composite record with pretty much same results of Fort Denison 1, only little bit more 1886 to 2013.

      If you look at the SONEL GPS velocity of an inland GPS dome, this is not the vertical velocity of the tide gauge, but the vertical velocity of an inland GPS dome. Fort Denison is a small island in the bay.
      SONEL says -0.89 mm/year. This means strong subsidence. for the same GPS dome, JPL says -0.465 mm/year, so subsidence but less. Not to discourage you guys, but Australia is not subjected to subsidence. The problem of the GPS is a constrained computation, and if you want to overrate the uplift of Europe (SONEL) or the uplift of the United States (JPL) to claim “absolute” sea level rate of rise exceeding the relative, somewhere else, for example Australia, you do have negative absolute rates of rise in Sydney and Fremantle when the relative rates of rise are actually positive.

      This is the principle of the short blanket. you cant cover shoulders and foots.

      Again, please do NOT get trapped in the “absolute” sea level rise. You cannot know with accuracy the “absolute” sea level, and what flood the land is the relative sea level … and please remember to support the integrity of the data sets in PSMSL and NOAA to avoid the administrative adjustments we already experienced in many products.

      I hope you enjoyed the latest PSMSL survey, with only the records too short or too incomplete removed.

  23. The PSMSL surveys (as the NOAA surveys) of relative sea level rises are extremely relevant.

    These surveys tell you where along the coast the sea levels are rising or falling, and if they are accelerating (just compare the relative rates of rise of different surveys in the same tide gauges where only few more years of data are added).

    What the PSMSL and NOAA surveys tell you is that almost nowhere there is a need to cope by coastal management with the rising seas.

    Where they are measured properly, the relative sea level rises are everything but dramatic and they are about constant.

    So the 2 meters sea level rise added everywhere in the United States as per the TMAC report are a disgrace for science.

    If somebody tell you that 2 m sea walls are needed along the west coast of the United States and Alaska, you may answer in Alaska the sea levels are mostly falling, and along the west coast of the United States and Alaska the sea levels are rising about 1 mm something on average … so it may take forever to make plausible the 2 m sea walls in Alaska and possibly 2,000 year in California, Oregon and Washington state.

    Please do NOT get trapped in the “absolute” sea level rise. You cannot know with accuracy the “absolute” sea level, and what flood the land is the relative sea level …

    final remark, just to be precise about Sydney

    I do not know where the claim the relative sea levels in Sydney are rising 1.15 mm/year.

    If you look at the PSMSL survey I proposed, it says +0.65 mm/year in Fort Denison 1 (longer) and +0.96 mm/year in Fort Denison 2 (shorter). The two tide gauges are leveled each other and overlapping, so you can make a composite record with pretty much same results of Fort Denison 1, only little bit more 1886 to 2013.

    If you look at the SONEL GPS velocity of an inland GPS dome, this is not the vertical velocity of the tide gauge, but the vertical velocity of an inland GPS dome. Fort Denison is a small island in the bay.
    SONEL says -0.89 mm/year. This means strong subsidence. for the same GPS dome, JPL says -0.465 mm/year, so subsidence but less. Not to discourage you guys, but Australia is not subjected to subsidence. The problem of the GPS is a constrained computation, and if you want to overrate the uplift of Europe (SONEL) or the uplift of the United States (JPL) to claim “absolute” sea level rate of rise exceeding the relative, somewhere else, for example Australia, you do have negative absolute rates of rise in Sydney and Fremantle when the relative rates of rise are actually positive.

    This is the principle of the short blanket. you cant cover shoulders and foots.

    Again, please do NOT get trapped in the “absolute” sea level rise. You cannot know with accuracy the “absolute” sea level, and what flood the land is the relative sea level … and please remember to support the integrity of the data sets in PSMSL and NOAA to avoid the administrative adjustments we already experienced in many products.

    I hope you enjoyed the latest PSMSL survey, with only the records too short or too incomplete removed.

    • This is very interesting. Could you say what is the basis for the assertion that “Australia is not subjected to subsidence” ?

      Does this apply universally to all sites in Australia, does it apply to islands like Fort Denison?

      Neither do I follow your shortest blanket. If they want to rig Europe and N. Am. how does this make Oz go down. Calling GPS a short blanket is not a satisfactory account. Could you be clearer about what these assertions are based on?

  24. The naïve average is practically zero…

    It is practically zero and totally naïve. You’d have to be totally naïve to think it told us anything.

    I thought when the article stated with a statement about the naïve average, it was going to go on and say “BUT when we do XXXX we get ….. ”

    But no, it is totally naïve averages all the way down. IMO it was a waste of time writing it. There is no reason given for why we should look a naïve averages or why we should think they are better than more thorough analyses which attempt to make account for land movement.

    You’d have to be totally naïve to think it told us anything.

    • Also the histogram at the end shows that the data have a strongly skewed distribution, so taking a naïve average is not appropriate. The mean is only effective at removing ‘normally’ ( or gaussian ) distributed errors.

      In this case it will give a low biased result because of the long tail on the left of the distribution.

  25. Like temperature data, sea level data is averaged and manipulated beyond all usefulness.
    Since coastal flooding is likely to occur only when there are king tides, why not just measure and plot the level of king tides? The actual height can be plotted on a graph without any calculations.
    The data at the NZ and Australian sites I have checked show that the height of king tides has been reducing for some years now. Those sites are NOT rising or falling. So, no flooding.
    You will get the same result if you put a mark at king tide time on a large immovable object by the sea. You will observe the marks keep dropping each year.
    Please stop using “mean tide” as it’s useless at predicting anything.

    • There are two separate things that can be sought form sea level data.

      1. an increase in absolute mean sea level , a component of which can be compared to global mean sea temp. change.

      2. Local relative sea level which affects peoples lives.

      The alarmists take 1. , add a bit GAIA “correction” and ‘inverse barometer’ for good measure and then use it to make scare stories about 2.

      GAIA correction has ZERO effect on 2.

      The data at the NZ and Australian sites I have checked show that the height of king tides has been reducing for some years now.

      How many years? There are 18y cycles in tides, these are known and predictable. Hurricane Sandy coincided with just one such event.

  26. There are islands off Sumatra which dropped down after the 2004 and 2005 earthquakes, where the relative sea level rose up to a few metres within a few hours. Some villages were flooded at a rate far exceeding the current rate of sea level rise of around 1mm+ /year; and nobody died because of this subsidence. The villagers just packed up and moved further inland. Why is this such a big deal?

    Meanwhile, back in the real world, the rates of malaria, malnutrition, poverty, lack of education and infrastructure, preventable illness-related deaths and corruption on these islands, remains very high.

    Which of these issues above do you think that locals think is the least important?

  27. if you guys look at the latest TMAC report

    http://www.fema.gov/media-library-data/1454954261186-c348aa9b1768298c9eb66f84366f836e/TMAC_2015_Future_Conditions_Risk_Assessment_and_Modeling_Report.pdf

    you may find as “settled science” Highest Scenario SLR by 2100 (m) 2.0 (ft.) 6.6 …

    now, to get 6.6 ft. it will take much more than the 84 years left of this century ….

    in the 158 locations with record started before 1934, it will take on average 57,982 years, or better to say

    never ever this will happen in 54 locations where the sea level is reducing

    1,143 years in the 97 locations with average sea level rise 0-3.25 mm/year (average sea level rise 1.75 mm/year)

    381 years in the 7 locations with average sea level rise >3.25 mm/year (average sea level rise 5.25 mm/year)

    in the US, where the sea levels are rising or falling with an average well below 2 mm/year, why do you want to pay your insurances today big $$$$$$ for something that is unlikely to happen before 1,000 years from now?

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