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50-Year Sea Level Trends At Newlyn & North Shields

July 22, 2017
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By Paul Homewood

As promised, I have also run some charts showing 50-year trends for sea level rise at Newlyn and North Shields.

As any half competent oceanographer will tell you, you need to be looking at trends of at least 50 years, as Bruce Douglas points out:

It is well established that sea level trends obtained from tide gauge records shorter than about 50-60 years are corrupted by interdecadal sea level variation.

 

As with the 10-year trends I presented yesterday, the charts below give 50-year trends on an overlapping monthly basis:

image

image

http://www.psmsl.org/data/obtaining/

 

Both stations show accelerating sea level rise culminating in 1970, before dropping away, and then recovering again in the 1990s.

There is a subtle difference though. The trend at Newlyn is slightly higher now than its peak in 1970, whereas at North Shields it is still well below.

Newlyn is of course heavily influenced by what happens in the Atlantic, so that may be a factor.

Either way, there is no evidence of anything alarming happening to sea levels at these two stations at least.

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17 Comments
  1. HotScot permalink
    July 22, 2017 5:26 pm

    What do I take for sea level sickness? 🙂

    • Juliet 46 permalink
      July 22, 2017 5:43 pm

      Sea Legs and Plimsolls….

    • Athelstan permalink
      July 22, 2017 9:06 pm

      Some good company, a good old chat and some grub, a few bottles of old puke and just let the mood float away your boat.

  2. quaesoveritas permalink
    July 22, 2017 6:04 pm

    What did you do about the periods of missing data at North Shields, in particular Jan 1975 to July 1978?
    Did you interpolate those?

    • July 23, 2017 9:15 am

      No, I’ve left them blank

      • quaesoveritas permalink
        July 23, 2017 10:15 am

        Do you mean zeros?
        Won’t that effect the trend?
        Having said that, I have used interpolated figures and my trends look very similar to yours.
        OTOH when I used the last figure available for all of the missing data it produced different results.
        Did you use Excel ?
        Maybe that handles it automatically somehow.

      • quaesoveritas permalink
        July 23, 2017 10:32 am

        I tried it with blanks and Excel produced similar but not identical results to using interpolated figures.
        I can’t really say which is the most accurate or “correct”.

  3. Green Sand permalink
    July 22, 2017 6:33 pm

    The problem with hypothetical model predictions is they impact on real lives, today!

    Ask the residents of Fairbourne and somewhat more difficult, the bloke who built Harlech Castle 40 mls up the coast, which due to changing sea/land levels no longer has a sea gate.

    http://www.dailymail.co.uk/news/article-3442264/Welsh-village-decommissioned-warnings-lost-sea.html

    https://en.wikipedia.org/wiki/Harlech_Castle

  4. bushwalker permalink
    July 22, 2017 6:47 pm

    Is there some reason you aren’t fitting a quadratic trend to the whole data? The acceleration is then just twice the quadratic coefficient.

    • quaesoveritas permalink
      July 22, 2017 7:38 pm

      What would that give us?
      Would it be a single figure or a figure which changes over time?
      Paul’s overlapping trend shows us how the trend has changed.
      It’s as if you did a 50 year trend in 1944 and updated it every month as data became available.

      • bushwalker permalink
        July 22, 2017 8:17 pm

        It would give you a single figure for the acceleration over the whole data range.

        Looking at the data, I’d guess it would be a very small number which would indicate that the trend was actually linear.

      • quaesoveritas permalink
        July 22, 2017 9:22 pm

        I’m not sure that is what we are interested.
        Personally i am more interested in what the acceleration is now, compared to the past, to see whether the claims that it is increasing are valid.
        The rolling trend shows how acceleration is evolving with time.

    • July 23, 2017 9:23 am

      Dave Burton’s website has tools for this.

      The quadratic trend looks very similar to the linear

      http://www.sealevel.info/MSL_graph.php?id=newlyn&quadratic=1&co2=0&lin_ci=0

      • quaesoveritas permalink
        July 23, 2017 10:19 am

        Yes, I don’t find that particularly useful for judging how the trend is changing with time.

  5. July 24, 2017 2:59 pm

    Northern Britain is still rising after the ice age, while southern Britain is dropping. This could account for the difference.

  6. Jack Broughton permalink
    July 24, 2017 8:40 pm

    If anyone in the world was really threatened by a global rise in levels surely it would be “the low countries”. They have coped for generations with sea levels and are not shouting about threats, surely that is enough demonstration of a non-problem for anyone.

    It is doubtful whether the average level changes have any significance: it is a high level change that would cause flooding, are these reported?

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