Parker and Ollier (2015) set the tone for their new paper on sea level change along the coastline of India in the very first sentence of their abstract: “global mean sea level (GMSL) changes derived from modelling do not match actual measurements of sea level and should not be trusted” (emphasis added). In contrast, it is their position that “much more reliable information” can be obtained from analyses of individual tide gauges of sufficient quality and length. Thus, they set out to obtain such “reliable information” for the coast of India, a neglected region in many sea level studies, due in large measure to its lack of stations with continuous data of sufficient quality.
A total of eleven stations were selected by Parker and Ollier for their analysis, eight of which are archived in the PSMSL database (PSMSL, 2014) and ten in a NOAA sea level database (NOAA, 2012). The average record length of the eight PSMSL stations was 54 years, quite similar to the average record length of 53 years for the eleven NOAA stations.
Results indicated an average relative rate of sea level rise of 1.07 mm/year for all eleven Indian stations, with an average record length of 51 years. However, the two Australian researchers report this value is likely “overrated because of the short record length and the multi-decadal and interannual oscillations” of several of the stations comprising their Indian database. Indeed, as they further report, “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,” which increase most certainly skews the rate trend of the shorter records over the most recent period of record above the actual rate of rise.