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The Importance of Length-of-Record in Assessing Sea Level Change

Reference
Scafetta, N. 2013. Multi-scale dynamical analysis (MSDA) of sea level records versus PDO, AMO, and NAO indexes. Climate Dynamics: 10.1007/s00382-013-1771-3.
Scafetta (2013) writes that "long-term sea level variations are driven by numerous coupled processes arising from an interaction of eustatic sea level rise and glacial isostatic subsidence, long-term tidal and solar cycles, oscillations of ocean circulation, variations in temperature and/or salinity and other factors that can be also characteristic of the specific geographical location." And it thereby logically follows that all of these factors must be identified and their relative magnitudes determined in order to see what temperature change remains that might have been produced by anthropogenic activities.

Against this backdrop, Scafetta developed "a multi-scale dynamical analysis to facilitate the physical interpretation of tide gauge records," which technique employs graphical diagrams that he "applied to six secular-long tide gauge records representative of the world oceans," namely, "Sydney, Pacific coast of Australia; Fremantle, Indian Ocean coast of Australia; New York City, Atlantic coast of USA; Honolulu, US state of Hawaii; San Diego, US. State of California; and Venice, Mediterranean Sea, Italy." And with the knowledge that he gained from this exercise, he conducted equivalent analyses of the Pacific Decadal Oscillation (PDO), the Atlantic Multidecadal Oscillation (AMO), along with the global sea level reconstruction developed by Jevrejeva et al. (2008) and that of the North Atlantic Oscillation (NAO) produced by Luterbacher et al. (1999), all of which was done with the goal of ultimately determining what residual impact may have been caused by the activities of man.

The dedicated-to-detail researcher reports that "from the decadal to the secular scales (up to 110-year intervals) the tide gauge accelerations oscillate significantly from positive to negative values mostly following the PDO, AMO and NAO oscillations," adding that "the influence of a large quasi 60-70 year natural oscillation is clearly demonstrated in these records."

In light of his several findings, Scafetta concludes that "a 110-year-long record is necessary for fully filtering out a 60-year periodic cycle from a background quadratic polynomial trend," and on this basis he says "it is difficult to determine whether the late twentieth century anthropogenic warming had a significant effect on tide gauge records." Therefore, until such a determination can confidently be made, it is premature to place confidence in any particular prediction of sea level change for the year 2100 and beyond; and especially is this so in regard to the huge increases that are periodically touted by the IPCC and others.

Additional References
Jevrejeva, S., Moore, J.C., Grinsted, A. and Woodworth, P.L. 2008. Recent global sea level acceleration started over 200 years ago? Geophysical Research Letters 35: 10.1029/2008GL033611.

Luterbacher, J., Schmutz, C., Gyalistras, D., Xoplaki, E. and Wanner, H. 1999. Reconstruction of monthly NAO and EU indices back to AD 1675. Geophysical Research Letters 26: 2745-2748.

Archived 27 August 2013