Nicola Scafetta: Major new sea level study – finds C21st rise likely to be less than a foot.

Congratulations to Nicola Scafetta, who has successfully published a new paper on sea level rise Multi-scale dynamical analysis (MSDA) of sea level recordsversus PDO, AMO, and NAO indexes in the  journal Climate Dynamics. This is a major paper, which undertakes a comprehensive review of recent studies, which diverge widely in their findings. He finds that the main reason for divergence is the length of records used in studies, and shows that the quasi-cyclic oscillations of the major ocean basins largely account for the differences in those studies conclusions. Developing a powerful analysis technique with strong visualisation, it is shown that the periodicity of the major oscillations, being 60 to 70 years, require a minimum record length of around 110 years in order to prevent polynomial fitting of long term secular trends being contaminated with shorter term quasi-cyclic variation. Using tide gauge records going back as far as 1700, Nicola compares the trends in sea level rise acceleration at widely spread geographical locations once the quasi-cyclic components are removed and finds the long term global average to be very small – around 0.01mm/yr. Very little difference is found between acceleration rates between the pre and post industrial eras. It is suggested the acceleration is a natural variation due to the recovery from the little ice age as part of a quasi millennial cycle which may continue until the mid C21st. In conclusion the study suggests that sea level rise during the C21st will be around 277+/-7mm, or about 9 inches.

Fig. 10 a Global sea level record (Jevrejeva et al. 2008) (left) and its
MSAA colored diagram (right).

Multi-scale dynamical analysis (MSDA) of sea level recordsversus PDO, AMO, and NAO indexes
N. Scafetta

Received: 24 February 2013 / Accepted: 10 April 2013  Springer-Verlag Berlin Heidelberg 2013

Abstract: 
Herein I propose a multi-scale dynamical analysis to facilitate the physical interpretation of tide gauge records. The technique uses graphical diagrams. It is applied to six secular-long tide gauge records representative of the world oceans: 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. For comparison, an equivalent analysis is applied to the Pacific Decadal Oscillation (PDO) index and to the Atlantic Multidecadal Oscillation (AMO) index. Finally, a global reconstruction of sea level (Jevrejeva et al. in Geophys Res Lett 35:L08715, 2008) and a reconstruction of the North Atlantic Oscillation (NAO) index (Luterbacher et al. in Geophys Res Lett 26:2745–2748, 1999) are analyzed and compared: both sequences cover about three centuries from 1700 to 2000.

The proposed methodology quickly highlights oscillations and teleconnections among the records at the decadal and multidecadal scales. At the secular time scales tide gauge records present relatively small (positive or negative) accelerations, as found in other studies (Houston and Dean in J Coast Res 27:409–417, 2011). On the contrary, 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. In particular, the influence of a large quasi 60–70 year natural oscillation is clearly demonstrated in these records. The multiscale dynamical evolutions of the rate and of the amplitude of the annual seasonal cycle of the chosen six tide gauge records are also studied.

Keywords Tide gauge and sea level records  PDO, AMO and NAO indexes  Climate oscillations  Dynamical analysis of time series  Multi-scale analysis of time series  Physical couplings and teleconnections

From the conclusion:

In conclusion, at scales shorter than 100-years, the measured tide gauge accelerations are strongly driven by the natural oscillations of the climate system (e.g. PDO, AMO and NAO). At the smaller scales (e.g. at the decadal and bi-decadal scale) they are characterized by a large volatility due to significant decadal and bi-decadal climatic oscillations (Scafetta 2009, 2010, 2012a; Manzi et al. 2012). Therefore, accelerations, as well as linear rates evaluated using a few decades of data (e.g. during the last 20-60 years) cannot be used for constructing reliable longrange projections of sea-level for the twenty first century. The oscillating natural patterns need to be included in the models for producing reliable forecasts at multiple time scales. The proposed MSDA methodologies (e.g. MSAA, MSRA and MSACAA) provide a comprehensive picture to comparatively study dynamical patterns in tide gauge records. The techniques can be efficiently used for a quick and robust study of alternative climatic sequences as well.