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Is There A 60-year Oscillation In Global Mean Sea Level?

November 5, 2012

By Paul Homewood


We are often told that the rate of sea level rise has been accelerating since satellite monitoring began in 1992. We already know that 1992 is not a very representative place to start from, as Church & White tell us :-

However, the reconstruction indicates there was little net change in sea level from 1990 to 1993, most likely as a result of the volcanic eruption of Mount Pinatubo in 1991.”

The University of Colorado claim that the rate of sea level rise since 1992 is 3.1mm/year, but this includes an isostatic adjustment of 0.3mm/year, meaning that the sea level, as measured on our coastline, is only rising by 2.8mm/year. (Basically, they argue the sea floor is sinking: more information here). Taking this  along with the Pinatubo factor, it is clear that the underlying rate of rise is not much greater than the generally accepted 20thC rise of about 190mm.


But a paper published last month in GRL by Chambers, Merrifield and Nerem, entitled “Is there a 60-year oscillation in global mean sea level?” questions whether there has in fact been any underlying acceleration in the rate of rise at all.



We examine long tide gauge records in every ocean basin to examine whether a quasi 60-year oscillation observed in global mean sea level (GMSL) reconstructions reflects a true global oscillation, or an artifact associated with a small number of gauges. We find that there is a significant oscillation with a period around 60-years in the majority of the tide gauges examined during the 20th Century, and that it appears in every ocean basin. Averaging of tide gauges over regions shows that the phase and amplitude of the fluctuations are similar in the North Atlantic, western North Pacific, and Indian Oceans, while the signal is shifted by 10 years in the western South Pacific. The only sampled region with no apparent 60-year fluctuation is the Central/Eastern North Pacific. The phase of the 60-year oscillation found in the tide gauge records is such that sea level in the North Atlantic, western North Pacific, Indian Ocean, and western South Pacific has been increasing since 1985-1990. Although the tide gauge data are still too limited, both in time and space, to determine conclusively that there is a 60-year oscillation in GMSL, the possibility should be considered when attempting to interpret the acceleration in the rate of global and regional mean sea level rise.


Of course, none of this should come as any real surprise. Leading expert, Bruce Douglas, warned us that “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”. It is also clear from his graph, below, that there have been periods during the 20thC when sea level has been increasing faster than at other times, notably in the 1970’s which were followed by a sea level falls in the 1980’s.


Will we hear about any of this from the team? Silly question really.

  1. John Williams permalink
    November 5, 2012 9:12 pm

    Not a lot of people know that GRACE has been used to justify the satellite SLR records, and now has come under scrutiny as being erroneous.

  2. Roger Andrews permalink
    November 7, 2012 3:01 am


    Here’s your 60-year sea level oscillation, a little ragged but there nonetheless. It’s more or less in phase with the AMO and the Scafetta 60-year planetary cycle:

    I constructed this series myself from PSMSL tide gauge records without applying any adjustments for vertical land movement, so what it shows is sea level rise relative to the global coastline rather than “absolute” SLR, i.e. SLR relative to the center of the earth. I did it this way because the vertical land movement adjustments that get applied to Church & White and other published “absolute” SLR series are based on crustal glacial rebound models that give the wrong answer over most of the earth and which generate far more sea level rise since 1900 than has actually occurred as a result.


  1. Is There A 60-year Oscillation In Global Mean Sea Level? | The Global Warming Policy Foundation (GWPF)

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