Sea Levels Are Stable And Falling At About Half Of The World’s Tide Gauges

Image from  Mörner, 2017

Is Sea Level Rise ‘Global’ If Roughly 50% Of Gauges Show Stable To Falling Sea Levels?

A few years ago, a comprehensive analysis of selection bias in tide gauge measurements between 1807-2010 indicated that (a) sea levels are only rising at a rate of about 1 mm/yr (as of 2010), and (b) a total of 65% of the world’s tide gauges have recorded stable to falling sea levels.

Beenstock et al., 2014

“Tide gauges dating back to the 19th century were located where sea levels happened to be rising. Data reconstructions based on these tide gauges are therefore likely to overestimate sea level rise.”

“We therefore study individual tide gauge data on sea levels from the Permanent Service for Mean Sea Level (PSMSL) during 1807 – 2010 without recourse to data reconstruction. Although mean sea levels are rising by 1mm/year, sea level rise is local rather than global, and is concentrated in the Baltic and Adriatic seas, South East Asia and the Atlantic coast of the United States. In these locations, covering 35 percent of tide gauges, sea levels rose on average by 3.8mm/year. Sea levels were stable in locations covered by 61 percent of tide gauges, and sea levels fell in locations covered by 4 percent of tide gauges. In these locations sea levels fell on average by almost 6mm/year.”

Out of a database of over 2,100 tide gauge measurements available from the Permanent Service for Mean Sea Level, NOAA has selected 240 tide gauges for their analysis of global-scale sea level rise. Of these, there are about 15 gauges that did not extend far enough into the last few decades (for example, Latvia, Antarctica, Ghana, Colombia), precluding a recent trend analysis.

Of the remaining 225 tide gauges in the NOAA database, there are at least 100 located in regions where sea levels are stable (no significant change in either direction) or falling.  A graphical illustration of these non-trend tide gauge measurements is provided below.

With 45% to 65% of tide gauge measurements from across the globe indicating that there has been no significant sea level trend in the last 30 to 50 years (at least), why is it considered accurate to claim that sea level rise is occurring globally, rather than in some localities?

The tide gauge sites where sea levels have been stable to falling include such locations as: Canada, Alaska, Argentina, Australia, Russia, Greece, Sweden, Pacific Ocean, Denmark, California/Oregon/Washington (US), Croatia, Costa Rica, Norway, Chile, India, UK, Ireland, Spain, Philippines, South Korea, Singapore, Vietnam, and Thailand. 

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