On the Bright Side: A Deceleration of Sea Level Rise Along the Indian Coastline

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.

One additional important finding of the study was gleaned from the longer records in the database, which revealed that the rates of sea level rise along the Indian coastline have been “decreasing since 1955,” which observation of deceleration stands in direct opposition to model-based claims that sea level rise should be accelerating in recent decades in response to CO2-induced global warming.

In comparing their findings to those reported elsewhere, Parker and Ollier note there is a striking similarity between the trends they found for the Indian coastline and for other tide gauge stations across the globe. Specifically, they cite Parker (2014), who calculated a 1.04 ± 0.45 mm/year average relative rate of sea level rise from 560 tide gauges comprising the PSMSL global database. And when that database is restricted in analysis to the 170 tide gauges with a length of more than 60 years at the present time, the average relative rate of rise declines to a paltry 0.25 ± 0.19 mm/year, without any sign of positive or negative acceleration.

The significance of Parker and Ollier’s work is noted in the “sharp contrast” they provide when comparing the rates of sea level rise computed from tide gauge data with model-based sea level reconstructions produced from satellites, such as the 3.2 mm/year value observed by the CU Sea Level Research Group (2014), which Parker and Ollier emphatically claim “cannot be trusted because it is so far from observed data.” Furthermore, it is clear from the observational tide gauge data that there is nothing unusual, unnatural, or unprecedented about current rates of sea level rise, with the exception that they appear to be decelerating, as opposed to accelerating, despite a period of modern warmth that climate alarmists contend is unequaled over the past millennium, and which should be melting away the polar ice caps and rapidly rising sea levels.



CU Sea Level Research Group. 2014. Global Mean Sea Level. sealevel.colorado.edu (retrieved May 30, 2014).

National Oceanic and Atmospheric Administration (NOAA). 2012. MSL global trend table, tidesandcurrents.noaa.gov/sltrends/MSL_global_trendtable.html (retrieved May 30, 2014).

Parker, A. 2014. Accuracy and reliability issues in computing absolute sea level rises. Submitted paper.

Parker, A. and Ollier, C.D. 2015. Sea level rise for India since the start of tide gauge records. Arabian Journal of Geosciences 8: 6483-6495.

Permanent Service on Mean sea level (PSMSL). 2013. Data, www.psmsl.org (retrieved October 1, 2013).