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Sea levels aren't rising

The skeptic argument...

"We are told sea level is rising and will soon swamp all of our cities. Everybody knows that the Pacific island of Tuvalu is sinking. Around 1990 it became obvious the local tide-gauge did not agree - there was no evidence of 'sinking.' So scientists at Flinders University, Adelaide, set up new, modern, tide-gauges in 12 Pacific islands. Recently, the whole project was abandoned as there was no sign of a change in sea level at any of the 12 islands for the past 16 years." (Vincent Gray).

What the science says...

Sea levels are measured by a variety of methods that show close agreement - sediment cores, tidal gauges, satellite measurements. What they find is sea level rise has been steadily accelerating over the past century.

A common error in climate debate is drawing conclusions from narrow pieces of data while neglecting the whole picture. A good example is the recent claim that sea level rise is slowing. The data cited is satellite altimeter measurements of global mean sea level over the past 16 years (Figure 1). The 60 day smoothed average (blue line) seems to indicate sea level  peaked around the start of 2006. So one might argue that sea levels haven't risen for 3 years. Could one conclude that the long term trend in sea level rise has ended?


Figure 1: Satellite altimeter measurements of the change global mean sea level with inverse barometer effect (University of Colorado).

To answer this question, all one has to do is view the entire 16 year dataset. A noisy signal is imposed over the long term trend of sea level rise. These fluctuations mean there will be short periods where sea level shows no trend. For example, 1993 to 1996 or 1998 to 2000. In other words, there have been several short periods of several years over the last 16 years of steady sea level rise where sea level appears not to rise.

This is inevitably the case when you have a noisy signal imposed over a long term trend. We see exactly the same phenomenon occur in the temperature record (which is why we also see the same erroneous conclusions). The lesson from this is to treat with skepticism anyone who concludes long term trends from several years of a noisy signal (after all, skepticism should cut both ways).

In addition to this, Figure 1 is a particularly noisy signal because it displays unfiltered data. Sea level is subject to the "Inverse Barometer" Effect. This is where sea level is depressed in areas of high atmospheric pressure, and raised in areas of low pressure. When barometric pressure effects are filtered out, the result is a less noisy signal and a clearer picture of what's happening with sea level.


Figure 2: Satellite altimeter measurements of the change global mean sea level with inverse barometer effect filtered out (University of Colorado).

A broader view of sea level rise

Global mean sea level (eg - the global average height of the ocean) has typically been calculated from tidal gauges. Tide gauges measure the height of the sea surface relative to coastal benchmarks. The problem with this is the height of the land is not always constant. Tectonic movements can alter it, as well as Glacial Isostatic Adjustment. This is where land which was formerly pressed down by massive ice sheets, rebounds now that the ice sheets are gone.

To construct a global historical record of sea levels, tide gauge records are taken from locations away from plate boundaries and subject to little isostatic rebound. This has been done in A 20th century acceleration in global sea-level rise (Church 2006) which reconstructs global sea level rise from tide gauges across the globe. An updated version of the sea level plot is displayed in Figure 3:


Figure 3: Global mean sea level from 1870 to 2006 with one standard deviation error estimates (Church 2008).

Tidal estimates from sediment cores go even further back to the 1300's. They find sea level rise is close to zero in the early part of the sedimentary record. They then observe an acceleration in sea-level rise during the 19th and early 20th century. Over the period where the two datasets overlap, there is good agreement between sedimentary records and tidal gauge data (Donnelly 2004, Gehrels 2006).

What we're most interested in is the long term trends. Figure 2 shows 20 year trends from the tidal data. From 1880 to the early 1900's, sea level was rising at around 1mm per year. Throughout most of the 20th century, sea levels have been rising at around 2mm per year. In the latter 20th century, it's reached 3mm per year. The five most recent 20-year trends also happen to be the highest values.


Figure 4: The linear trends in sea level over 20-year periods, with one sigma error on the trend estimates shown by the dotted lines. From 1963 to 1991, there were a series of volcanic eruptions which caused cooling and hence contraction of the upper ocean. This temporarily slowed the rate of sea level rise.

So a broader view of the historical record reveals that sea level is not just rising. The rate of sea level rise has been increasing since the late 19th century.

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Comments

Comments 1 to 15:

  1. In an interview with Dr. Nils-Axel Mörner (head of the Paleogeophysics and Geodynamics department at Stockholm University in Sweden, past president (1999-2003) of the INQUA Commission on Sea Level Changes and Coastal Evolution, and leader of the Maldives Sea Level Project – he has been studying the sea level and its effects on coastal areas for some 35 years) by EIR (Argentine Foundation for a Scientific Ecology) [http://www.mitosyfraudes.org/Calen7/MornerEng.html] he talked about the IPCC misrepresentation of sea level data: “Then, in 2003, the same data set, which in their [IPCC's] publications,... was a straight line—suddenly it changed, and showed a very strong line of uplift, 2.3 mm per year, the same as from the tide gauge... It was the original one which they had suddenly twisted up, because they entered a “correction factor,” ... I accused them of this at the Academy of Sciences in Moscow —I said you have introduced factors from outside; it's not a measurement. It looks like it is measured from the satellite, but you don't say what really happened. And they answered, that we had to do it, because otherwise we would not have gotten any trend! That is terrible! As a matter of fact, it is a falsification of the data set. ... So all this talk that sea level is rising, this stems from the computer modeling, not from observations. The observations don't find it! I have been the expert reviewer for the IPCC, both in 2000 and last year. The first time I read it, I was exceptionally surprised.
  2. A recent ( June 2009 ) scientific paper by Cliff Ollier of the School of Earth and Environment, The University of Western Australia, states as follows :


    Abstract: Graphs of sea level for twelve locations in the southwest Pacific show stable sea level for about ten years over
    the region. The data are compared with results from elsewhere, all of which suggest that any rise of global sea level is
    negligible. The Darwin theory of coral formation, and subsidence ideas for guyots would suggest that we should see
    more land subsidence, and apparent sea level rise, than is actually occurring. Sea level studies have not been carried out
    for very long, but they can indicate major tectonic components such as isostatic rebound in Scandinavia. Attempts to
    manipulate the data by modelling to show alarming rates of sea level rise (associated with alleged global warming) are not
    supported by primary regional or global data. Even those places frequently said to be in grave danger of drowning, such as the Maldives.
  3. I got into an argument about sea level rise as an indicator of climate change and was told that all recent rise could be attributed to increased sedimentation rates. Whilst I expressed doubts that, given the global ocean surface area, it could affect overall sea levels that much I had to concede that a lot of river mouths and bays are being affected by both silt from erosion and from deliberate infilling to create waterfront building sites. Locally both can be quite extensive. I have struggled to find quantification of human induced sedimentation and infilling; if anyone can link to something that a layperson such as myself can view and provide some perspective on rates relative to sea level rise I would appreciate it. Thanks, Ken.
  4. Ken in Oz,
    as far as i can remember, sediment deposition is historically of the order of a few GTons, or a percent of current ice sheet loss. Negligible. Also, the sedimentation rate is on the decline due to the more and more dams that are bilt.
    I'd like to see where your friends got the numbers that explain sea level rise with sedimentation, i never heard about it.
  5. Riccardo, I'm not sure I really want to see where he got the argument and suspect it's not an argument based on any numbers; rather, it's an argument that appeals to something that sounds credible only as long as numbers are absent. Which is why I'd like to see some.
  6. Re: 1 & 2 - I can't find much on Morner other than his Wiki page which suggests his work was often cited and though now seemingly discredited he must have once been a leading authority on sea level rises or the lack of them. He certainly claimed to be the best in the world in the external links to interviews from Wiki in which he rages about the IPCC bringing in modellers rather than sea-level experts.
  7. Can I point out that your statement about rising sea level is false? B. F. Chao, Y. H. Yu, and Y. S. Li (Science, 320:212-214) have shown that sea level rise for the last eighty years has been linear, with a slope of 2.46 millimeters per year. Theirs is the sea level that has been corrected for the effect of water held in storage by all dams built since the year 1900. Something that has been linear this long is not likely to change anytime soon. Which means that you can be a futurist and predict that sea level will rise a little under ten inches in a century, not twenty feet that Al Gore is still peddling in his movie.
    Response: Arno, thanks for bringing our attention to that paper which actually shows that the situation is worse than I described. The paper is Impact of Artificial Reservoir Water Impoundment on Global Sea Level (Chao 2008). It reconstructs how much water has been impounded in water reservoirs since 1900. The amount of water stored skyrocketed after 1950. If this hadn't occured, sea level would've been even greater. Consequently, they calculate what global sea level should be after accounting for reservoir impoundment water. They then compare their results to actual observed sea level:



    What they find is the increase in the rate of sea level rise is actually greater when you factor in water impoundment. This increases the significance of retreating ice sheets. A sobering result, considering the accelerating ice loss from Antarctica and Greenland.
  8. Arno Arrak,
    we all know that Al Gore didn't quote any time span for the 20 feet rise. We all also know for sure that the sea level will not stabilze by the end of this century. Comparing Al Gores number with a one century rise is (intentionally?) misleading.
  9. I did not realize that you had posted a comment to my comment until now. I want to emphasize that factoring in water impoundment gives the true rate of sea level rise that would exist if no water were impounded. I don't know why you bring in the other curves especially since the slope, and hence the predicted rate or rise, is essentially the same. And none of this has any significance whatsoever on the fate of retreating ice sheets. That is a totally different issue and depends upon the causes of arctic warming. In the case of the Antarctic the West Antarctic ice sheet is melting because it is being undermined by warm water rising up from below in the Amundsen Sea. This is because prevailing winds are from land to sea and blow away the cold surface water which is then replaced by warmer Antarctic bottom water. It has collapsed before, most recently 1500 years ago, and may collapse again if this keeps up. In the Arctic we are now in the middle of more than a century long warming period that started abruptly at the start of the twentieth century. This abrupt beginning rules out any greenhouse effect as its cause and indicates that a rearrangement of North Atlantic current system that directed warm water to the north took place at the turn of the century. Since we know that the Gulf stream now brings warm water to the Arctic it is likely that it assumed its present northerly course at that time. It is futile to try to predict any of this from computer models using the old carbon dioxide global warming paradigm. They produce nothing but GIGO.
  10. Neil, I don't wish to be unkind to Dr. Mörner, just want to point out what he says elsewhere in that interview as a bit of a reality check. I'm not sure what exactly the situation with him is, but quite clearly this is wrong:

    "Always the same thing: In about 1970, the sea fell about 20 cm, for reasons involving probably evaporation or something. Not a change in volume or something like that- it was a rapid thing. The new level, which has been stable, has not changed in the last 35 years. You can trace it so very, very carefully. No rise at all is the answer there."

    Much of the rest of the piece consists of accusations of lies, coverups, falsifications, too much to be believable.

    It's actually pretty sad, and I say that with sincerity.

    Sometimes you need to look at a narrative in sum and ask yourself, how -likely- is this? If I'm confronted with one man's word against hundreds and there is coherent consistency between what those many say that is completely inconsistent with the beliefs of the lone individual, I'm afraid I'm not going to believe him. There are just too many eye-popping anecdotes in Dr. Mörner's story to hold water.
  11. doug_bostrom #10

    Back to my analogy with Galileo. Science is not a matter of votes. Politics is... in a democratic society of course.

    Thus your argument of "one man's word against hundreds" is, on the face of it, inconsistent with your statement earlier today that you did not want to follow me in the "wilderness", which I assumed was the wilderness of human psyche of which politics is the direct result.
  12. In #10 doug_bostrom hands us a quote from Dr Mörner, where he appears to be talking about a sudden (impossible) 20 cm fall of the sea level in 1970. Actually he is at the time talking about local changes in the Venice area, not about general sea level. It is, I think, misleading and dishonest to use a quote in this way.

    Also, it is not 'one man's word against hundreds'. He tells us that he was shocked, as an IPCC reviewer in 1999, to see the chapter on sea level in a forth-coming report. The chapter was written by 33 authors, and not a single one was a sea level specialist! He brought the report up in subsequent meetings in INQUA, where 300-400 experts on sea levels talked it over, and agreed that it was faulty. So it is more like hundreds of experts against 33 amateurs...
  13. Argus at 03:08 AM on 4 March 2010

    Actually the bit I referred to was in connection with Tuvalu. But I could have been more clear.

    Here's what I should have said more explicitly:

    It is questionable for Dr. Mörner to cite what is clearly a local drop in sea level, a change unconnected with events elsewhere, in connection with a general argument that global sea level is not subject to change due to AGW.
  14. Maybe we have heard different interviews. Anyway, I listened to a one-hour telephone (I think) interview on the site: http://itsrainmakingtime.com/2010/nilsaxelmorner/
    At about 33 minutes nto the recording he talks for only a minute or so about Venice specifically, mentioning the long range of measurements available. He did not use the temporary drop as an argument. He is also generally very clear about how you must separate local changes (both going up and down), around the world's coast lines, from overall changes in the oceans. He sounds very credible and knowledgeable to me.
  15. Argus at 05:07 AM on 4 March, 2010

    Ah, you're right, different interviews. Here's what I referred to:

    http://www.climatechangefacts.info/ClimateChangeDocuments/NilsAxelMornerinterview.pdf

    In this interview, Dr. Mörner makes a lot of accusations, statements that seem reckless and would not pass muster via this site's moderation policy. Beyond that, I find the sheer amount of falsity and misconduct Dr. Mörner claims he sees to be unlikely.

    Dr. Mörner has a distinguished publication record in his field, yet he's sneeringly dismissive of researchers working with methods he's not accustomed to using. I'll hazard a guess about why he's so upset about this matter and sees what can only be described as a fairly vast conspiracy among other scientists. Dr. Mörner is a geologist who likes getting up to his elbows in actual material things out in the field, no bad thing. But as well, he appears to have a fundamental mistrust of numerical methods he believes are "sophisticated" in the pejorative sense of the word. He's not comfortable with remote sensing and he's not comfortable with abstractions.

    As an example of how Dr. Mörner's seeming lack of insight into disciplines he does not appear to understand leads him into the weeds, he summarizes research conclusions about Greenland's ice volume trend as "falsification." For me, that's where his credibility on this matter flatlines; referring to the already large and growing body of research into Greenland's ice volume condition as "falsification" is not a persuasive argument.

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