The Dutch experience of sea-level rise

Following on from the prompting of Hans Errin, I took a look at his links on climate change in his country. The Dutch National Institute for Coastal and Marine Management (KNMI) produced the following picture (taken from this document).

As you can see, sea levels were higher during the Medieval Warm Period (1000 years ago) than the depths of the Little Ice Age (550 years ago) and are currently between those two extremes today. It’s also apparent that the sea-levels have been broadly rising since at least the end of the last Ice Age.

In the conclusions, the author notes:

"De waterstandswaarnemingen laten nog geen versnelde zeespiegelstijging zien"

which translates as "The water level measurements show no acceleration in sea level rise" and

"Het is niet altijd goed gedocumenteerd of te achterhalen waarop de getallen voor de scenario’s gebaseerd zijn"

which I transliterate as "It’s not always well documented where the measurements for the data on which the [IPCC] scenarios are based ". (I think Steve has mentioned similar reservations about data archiving and model assumptions)

So the Dutch, who have most to lose from accelerating sea-level rise, see no evidence such an acceleration and find the climate models which suggest such an acceleration for the future unconvincing and poorly documented. Bear in mind that the part of the Netherlands which is below sea-level (more than half of the country and where most people live), is sinking as a result of post-glacial rebound (as is the Southern part of the UK).


  1. Posted Feb 14, 2005 at 7:16 AM | Permalink

    Nice graph. I’m afraid that it won’t become too popular even though it seems to say a lot. One of the features of the proponents of the doomsday is that they heavily underestimate the natural variations of everything. They say that the world is living on the edge, and if you change the sea level by half a meter or the temperature by 1 degree, everything collapses. They have not looked at these graphs – especially the more historical ones. The biosphere was very happy 3 million years ago when the temperature was 2-3 degrees higher – in fact, the humans were born (the last “global warming” was 2 million years ago, in the middle of creation of homo XXX). Also, 100 million years ago, the mammals were born, and the temperature were 10 degrees higher while the CO2 was probably above 3,000 ppm. But today we have air-conditioning, and therefore 0.5 degree is just far too much!

  2. Scot Wilcoxon
    Posted Feb 14, 2005 at 3:45 PM | Permalink

    That graph is also in

    Màƒ⵲ner has a number of works and I haven’t found the original context.

  3. John A.
    Posted Feb 15, 2005 at 4:48 AM | Permalink

    I seem to remember a similar graph was put into a comment on The reaction was predictable – disbelief. I think some of the posters could not comprehend such a simple graph could so completely contradict some of their most basic assumptions about climate change.

  4. Hans Erren
    Posted Feb 16, 2005 at 4:49 PM | Permalink

    John, It was me who put it there 🙂

    Anyone interested in the data:
    I digitised the Moerner graph and uploaded the data here:
    (NB not equidistant in time, height unit m)

    Detailed Amsterdam data (annual, height unit mm):

    Den Helder Data (monthly, height unit mm):

  5. John A.
    Posted Feb 17, 2005 at 3:31 AM | Permalink

    Hans, I thought it was you 😉 I’m just grateful you didn’t criticize my Dutch translation skills.

    It’s a shame there is no English translation of the document. I’m sure it should reach a larger audience.

    Two days ago, I watched an item on the BBC News about the Kyoto Protocol. It seamlessly talked about climate change and then immediately cut to the Netherlands and talked about the new Dutch approach to flooding by building up defences in some areas and allowing other areas to flood. It also showed floating houses on the river (which is something some Dutch people have been living in for centuries) Nowhere did the BBC mention the Dutch attitude to "climate change", as demonstrated by this document.

    There’s a weblog waiting to be written on the junk science pouring out of the BBC.

  6. Hans Erren
    Posted Feb 17, 2005 at 3:35 PM | Permalink

    The impact of the IPCC TAR is starting to reach Holland though, today it was announced in the news that coastal areas need to be prepared for a sea level rise of 50 cm in the next 50 years. Now that is a full 100 cm/century or a fivefold increase of the current observed trend, which is still not accellerating…

    John writes: Well, at least you’ll be prepared for the next 200 years….

  7. Hans Erren
    Posted Feb 17, 2005 at 3:40 PM | Permalink

    PS This is the authoritative publication on recent sea level change in the Netherlands:

    K.I. van Onselen, The influence of data quality on the detectability of sea-level height variations, Publications on Geodesy 49, Delft, 2000. 220 pages. ISBN 90 6123 273 1.

  8. Posted Mar 1, 2005 at 11:29 PM | Permalink

    I think you should treat the “Morner” graph of sea level rise with some caution. I would firstly ask how he achieved such superb temporal resolution (e.g. detecting oscillations of period a few centuries over a time span of 7000 years) — to adequately resolve these oscillations would require samples every few decades. I strongly suspect that, if you saw the original data you would see what Morner has done before (e.g. in his recent paper on the Maldives in Global and Planetary Change), which is to draw a smooth line through every one of his data points, without any indication of the uncertainty of each point (so that the maxima and minima indicate the actual data points). In other words, I suspect that most of the wiggles are just an indication that the uncertainty in the historical sea level is around +/- 1 metre. Therefore to say that “sea levels were higher during the Medieval Warm Period (1000 years ago) than the depths of the Little Ice Age (550 years ago) and are currently between those two extremes today” is incorrect. The best you can say is that sea level was rising in response to melting at the end of the last glaciation and flattened out (ie. with a trend of less than around 0.2 mm/year) about 2000 years ago. The 0.18 metres rise during the 20th century (1.8 mm/year, which is pretty well accepted now) is not shown on Morner’s graph and of course turns the last 2 millennia into another “hockeystick”.

    I’ll just add the comment that I find it strange how contrarians readily accept a plot such as the one shown here with hardly any details of the original reference, the actual data points, the analysis technique or the estimated uncertainty, while at the same time putting the “hockeystick” of Mann et al. under such heavy scrutiny!

  9. TCO
    Posted Sep 10, 2005 at 7:54 PM | Permalink

    That was a great comment John.

  10. Hans Erren
    Posted Dec 12, 2005 at 3:32 PM | Permalink

    re 4:
    updated link after webserver crash:

  11. Hans Erren
    Posted Jan 28, 2006 at 4:10 PM | Permalink

    The Dillingh presentation is removed from the KNMI websity but is surviving in the waybackmachine:

    Click to access RIKZ+Dillingh.pdf

  12. Brooks Hurd
    Posted Jan 28, 2006 at 4:47 PM | Permalink

    The Dillingh presentation seems to contradict the recent GRL paper by John Church et al. There is an article about this paper on the BBC website today. According to the BBC story, the GRL article only went back to 1870. This would correspond to the end of the LIA period when the sea levels listed by Dillingh were at the lowest point of the past 2,500 years.

  13. John A
    Posted Jan 28, 2006 at 5:29 PM | Permalink

    It’s amazing how history changes before our eyes, isn’t it?

  14. JerryB
    Posted Jan 28, 2006 at 5:52 PM | Permalink

    “Climate change science” in action!

  15. Hans Erren
    Posted Jan 28, 2006 at 6:12 PM | Permalink

    re 12:
    a sobering graph for holland.

  16. Dave Dardinger
    Posted Jan 28, 2006 at 6:31 PM | Permalink

    Well Hans,

    I sure don’t see any acceleration of sea level rise in Den Helder. And after you’ve subtracted the subsidence the 0.9-1.0 cm/decade is less than I’ve seen elsewhere as to a rise from ocean warming, glacial melting etc. So my sober analysis is the the Dutch don’t have much to worry about for quite a while.

  17. Pat Frank
    Posted Jan 28, 2006 at 9:11 PM | Permalink

    There’s something I’ve been wondering about awhile and since sea level is the current topic, maybe someone here can comment. It occurred to me that a constant sea level rise on a sphere must reflect a constant acceleration rather than a constant velocity. That’s because each successive constant linear increase in radius sweeps out a successively larger volume element on the surface of a growing sphere. The linear positively sloped sea level plots therefore imply that sea volume increase has been accelerating at a constant rate over the 20th century, all the while the rate of sea level rise has been constant. Am I wrong? And if not, has this been overlooked?

    A caveat in context here is that a constant acceleration of sea volume since 1900 does no more to validate AGW than does a constant velocity in sea rise.

  18. Dave Dardinger
    Posted Jan 28, 2006 at 9:33 PM | Permalink

    It’s not that you’re wrong, Pat, just that the difference is indectable. The circumference of a circle is Pi x 2r. Therefore if we’re talking a difference of say 1 meter in ocean surface level we’re talking 6.28 meters of additional circumference in 40,000 kilometers, or one part in 6 million. Such a difference isn’t worth worrying about. It’s a little more if you use area, but we’re actually only talking a couple of centimeter ocean rise a decade, not a meter, so it’s still trivial.

  19. John A
    Posted Jan 29, 2006 at 3:49 AM | Permalink

    Re #15,16

    Yes, but these direct measurements are mere anecdotes unless they are multiplied by several climate models and published in “peer-reviewed academic journals”

    And of course, the Dutch have a vested interest in suppressing news of acclerating sea-level rise.

  20. Barclay E. MacDonald
    Posted Mar 7, 2007 at 12:46 PM | Permalink

    #8, With all due respect you make a good point, while exactly missing the point, which is that this contrary information is not even acknowledged, let alone dissected. First step, is there a reasonable, contrary, limiting or clarifying point of view. Then, is it valid? There is nothing strange about this!

  21. Steve Sadlov
    Posted Mar 7, 2007 at 6:23 PM | Permalink

    Those who are in the know here in California worry about (relative) sea level fall. Our parts are marginally capable and require lots of dredging. The bar off of the Golden Gate, over which Oakland shipping must pass, is at times beset with breakers. Socal Ports of LA and Long Beach fight a constant battle with sand moved by long shore currents (those ports are breakwater demarkated, not natural). San Diego never really invested much in container shipment too close to LA/Long Beach. There was a sort of lame attempt to turn Eureka into a port by expanding the bar/spit plagued mouth bay mouth using massive breakwaters – new spits and bars formed all around them. At some point, some of these “ports” will be fully silted in / emerged and we’ll have only Houston Ship Channel style access.

  22. Posted Mar 8, 2007 at 3:28 AM | Permalink

    The measurement of sea level is, I would guess, as difficult as measuring temperature. Presumably wave height is automatically compensated for by the use of stilling wells.

    Does anyone have practical experience of stilling wells? I’m particularly interested in their performance during rough weather — do they under-read during storms?


  23. Willis Eschenbach
    Posted Mar 8, 2007 at 7:28 AM | Permalink

    John A., the link to the original of the graph is broken. Any chance that you can fix it?


  24. Steve Sadlov
    Posted Mar 8, 2007 at 12:13 PM | Permalink

    RE: #22 – I think you presume a degree of diligence that is simply not there. Most of the so called “MSL” measurements are taken from existing tide gages with various “corrections” reminiscent of Jones vis a vis surface temps. More recently there have been attempts to measure the absolute instantaneous zero potential surface using satellites, this is also obviously frought with all sorts of issues given impacts of atmospheric pressure and the decided non repeatabilty of actual gravity fields imposing the tides and distorting the surface – sure the Sun and Moon are the majority of the attraction but not all of it, and their positions are not completely repeatable. What a rat hole. Like attempts to mine surface temperature records, attempts to “measure” MSL are a crock.

  25. Harold Pierce Jr
    Posted Jun 4, 2007 at 7:19 PM | Permalink

    RE: Determination of Global Temperature

    You climatologist seem to expended an enormous amount of time, effort and electricity trying to determine global temperature. What a waste of watts. You should report two temperatures averages: one for the N hemisphere and one for the S. hemisphere since there is great disparty in land mass between these. Why not use remote deserts such as in western Australia where any land use effects are absent. How about lighthouses as global therometers? These are located in remote sites and usually have reliable temperature records for air and water temperatures. Land-based temperatures are now longer reliable due to the enormous amount of heat released.

    My household energy use is 24 kwh per day and the lot area is 700 sq. meters. Thus on average 1.4 watts/sq m is being emitted. This is like have 24 100 watt light bulbs running 24/7. BTW, the cost of electricity here in BC is only 5.56 cents per kwh.

  26. Steve Sadlov
    Posted Jun 4, 2007 at 7:47 PM | Permalink

    On the topic of sea level, as a proxy, as “evidence” of “killer AGW,” here is something fun:

  27. Nicholas
    Posted Jun 4, 2007 at 10:32 PM | Permalink

    My household energy use is 24 kwh per day and the lot area is 700 sq. meters. Thus on average 1.4 watts/sq m is being emitted. This is like have 24 100 watt light bulbs running 24/7.

    Check your calculations. 24kWh = 1kW * 24h. So, more like 10 x 100W light bulbs running continuously by my reckoning.

  28. Steve Sadlov
    Posted Jun 5, 2007 at 10:18 AM | Permalink

    RE: #26 – I realize there are more than enough data sets for everyone here to audit. That having been said, I would be willing to bet that the sea level data are rife with low hanging fruit.

  29. Joe Ellebracht
    Posted Jun 5, 2007 at 9:39 PM | Permalink

    Re #28, and looking at the summary of the research mentioned in the BBC article mentioned in #12.
    Here is the BBC text

    The data was obtained from locations throughout the globe, although the number of tidal gauges increased and their locations changed over the 130-year period.

    These records show that the sea level has risen, and suggest that the rate of rise is increasing.

    Over the entire period from 1870 the average rate of rise was 1.44mm per year.

    Over the 20th Century it averaged 1.7mm per year; while the figure for the period since 1950 is 1.75mm per year

    Looking at he website mentioned in #26 shows that there are large variation in the rate of rise in sea level at various locations, most probably due to subsidence variations. Hawaii has low sealevel rise (rising land?) while Galveston has high sealevel rise (sinking land?). In any case, a major problem for the study has to be that the scientists did not use the same places throughout the 130 years. You can get almost any result you want by selecting the places (im)properly.

    From the BBC summary, simple math suggests the average rise found during the 1870-1900 period was .57mm per year, while the first half of the 20th century is 1.65mm per year and the second half of the 20th century, as stated, is 1.75 mm per year. The 1870-2000 figure is surprisingly low, and suggests (unless there was a jump-shift) the early part of the first half of the 20th century probably had low figures too, holding down the 1900-1950 average. This would be enough to produce the “growth” claimed in the 20th centuy. It will be good to see the data sources.

    The site referenced in #26 has some long term graphs, and analysis of individual locations. My eyeball does not see a general trend toward growth in the rate of rise in the second half of the 20th century for most places, although perhaps for some. As the graph on the top of this topic shows, current rates of sea rise are very small compared to past rates over the last several thousand years. These past rates were not significantly affected by fossil fuel consumption. The Amsterdam data quoted in the post #11 reference shows about a 1mm per year rise 1870-1925, which is not far from the what you get when you take an average of the 1870-2000 and the 1900-1950 data mentioned in the BBC article. It looks to me right now like the acceleration, if real, was in the early part of the 20th century, not the recent part. For those keeping score (baseball reference) greenhouse gas emissions were much lower in the early part of the twentieth century.

    At the current rate of sea level rise and earth subsidence, the rise within the next 100 years will be about 17-20 cms. The Dutch data show 17cm over the last 100 years for the 6 locations shown. According to the Dutch analysis, the IPCC best estimate of sea level rise over the next 100 years has come down with each iteration, from 66 in the first to 48 in the third (TAR). The BBC quotes the Church et al paper as predicting much less than 48 (but more than 17-20). The third IPCC report has a range of 9 to 88 cms. sea level rise for the next 100 yeaars which means it is probably going to be right (or at least in the range), as it claims the sea rise might decrease by half or go up several times. Absent a repeat of the little ice age (possible of course) this range is wide enough to capture pertty much the entire range of results expected. It is a little like predicting that the Americans will elect a Republican or a Democrat for President in 2008.

  30. Terence Hale
    Posted Jul 5, 2007 at 9:03 PM | Permalink

    It very difficult to make a scientific indication of what’s happening to sea levels in Holland. The standardization of measurement is not well defined: The effect of counter measures such a dredging which is performed intensively in Holland is difficult to asses.
    What I noticed in Zandvoort, although intensive dredging is performed to flatten the sea bed and thus keep the waves low; is the periodic nature of the tide distance between low and high tide seems to be increasing. It must be noted the water level of the Dutch long sand coastline is easier to control than say Dalmatian coastline. I have also noticed an increase of the water table, for example in Zandvoort at the end of spring we had about six to seven weeks of nice weather but many of the cafes and restaurants were complaining of flooded cellars. Problems with drainage which normally occur in winter seem to now be a year constant. An addition point should be taken in consideration we are not only dealing with melting ice but climate change. Clouds are changing the day of the “rainy day” is coming to an end. The clouds seem to “tokenizing” there downfall in short intense loads. We are getting daily variation in temperature all the year through. One day hot the next cold even in winter one day freezing the next day spring temperature. The wind has taken an obvious change which also may distort sea level measurements. May be the Dutch KNMI should talk to the rain and listen to the wind.

  31. Paul Linsay
    Posted Jul 6, 2007 at 5:30 AM | Permalink

    #30, Terence

    the periodic nature of the tide distance between low and high tide seems to be increasing

    Tides are very tricky and depend quite sensitively on local underwater topography. The tidal range in Boston Harbor is 9.5 feet. The range on Nantucket Island, 50 miles way, is only about 3 feet. A change in tidal range could easily be due to the dredging.

  32. michel
    Posted Sep 20, 2009 at 2:29 AM | Permalink

    In pursuit of examples of scientific irony for a course for the young, one comes upon this page.

    It appears that if you want to establish the maximum extent of some variable over time, the approved method is to have a correct sampling interval. The sampling interval should be frequent enough to ensure that one is not missing the peaks. It is not correct simply to take a series of infrequent measurements over a long period, and draw a smooth line through them, and conclude that one has captured all the highs and lows.

    This, comment 8 by Hunter, and approved by TCO, is the sin committed by Morner. Because of this, we cannot rely on a graph produced by Morner which shows there has been minimal recent sea rise, and no acceleration. It must be possible he has missed the peaks and the fluctuations.

    The question for the class is: how many samples are there in the Vostok CO2 series? And how long was the period? And how were they linked? And why exactly do we think we know that CO2 is higher now than it has been for many hundreds of thousands of years?

    The class will have to use Google to find the CO2 data from Vostok in tabular form, then try plotting it for themselves in a spreadsheet. This should be educational in itself. After they get through with this, they will then revisit the above comments, and some of them at least will have a Zen moment and become enlightened.

    Well, that’s what a sense of irony does for you.

  33. Peter
    Posted Nov 1, 2009 at 12:27 PM | Permalink

    The southern British coastline is sinking at the rate of slighly more than 2 mm/yr, due to post-glacial rebound of the crust. The central part of the Scottish highlands is correspondingly rising at the rate of 3 mm/yr. So 150 years will see 30 cm of sea-level rise on the southern coast of Britain (including the Thames Valley and the valley of the Severn in south Wales) even if there is no corresponding general rise in sea level over that period for the rest of the world.

    Immediately following the collapse of the Fennoscandian ice-sheet at the end of the ice-age, initial crustal rebound rates reached about 7.5 cm/yr. In the event of Greenland or Antarctica losing their ice, we can expect these rates of land-rise to be seen possibly for several decades. This in itself will displace a considerable amount of water, causing further sea-level rise.

  34. curious
    Posted Nov 1, 2009 at 1:55 PM | Permalink

    Peter – I’ve heard this before re: the southern British coastline – do you have a source you can point me to? It suggests the UK landmass is a rigid lever pivoting about a fulcrum? Is that realistic? Over the length of the UK that would suggest very impressive beam strength for a mixed non continous material?

    If one has had (say) a sponge with a weight on one end and one removes the weight the previously unweighted end does not fall – in fact it will also rise slightly as the compressive stresses will have been distributed through out the sponge. However if one has a rigid steel plate on top of the sponge and the weight is removed then the previously unweighted end of the plate could fall as it could have been effectively unsupported by the deformed sponge (which would also have been acting as the fulcrum) when the other end was in the weighted condition. Is the latter the correct analogy?

    Apologies if the above is geologically simplistic/uninformed – please point me to a reference. I have read the Wikipedia on this but the reference for the UK points to an insurance risk report which doesn’t give a reference for the claim. Thanks

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  1. […] The following link leads to a graph produced by the Dutch Govt sea level organisation- and confirm sea levels are stable and are somewhat lower than during the MWP. (This won’t stop them reacting to the IPCC by raising sea defences) Link 12 […]

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