Sea Level Expert: Recent Sea Level Change Exaggerated

The study "Comparison of Sea Levels measured by Satellite Altimetry and by Tide Gages" by Cyril Galvin PhD is the subject of the May 20th meeting of the Potomac Geophysical Society. 

Abstract:

“Present-day sea level change: Observations and causes” appeared in Reviews of Geophysics (2004). Its authors claim “global mean sea level rise is now known to be very accurate, 2.8+/-0.4mm/yr”, a rate “significantly larger than the historical rate of sea level change measured by tide gages during the past decades (in the range of 1-2mm/yr)”. The 2004 paper has been cited in the literature at least 115 times (in Web of Science database, as of 14 April 2010), usually to support a very recent acceleration of sea level rise. Tide gages have operated for centuries; satellite altimetry has been around for two decades. Both gages attempt to measure the elevation of the sea surface. The tide gage is immersed in the sea surface, the satellite altimeter orbits 100 miles away. In April 2003, I selected 14 tide gages from US coasts whose data are collected by NOAA and archived by PSMSL. The 14 are located at or near ocean coasts and have data for quarter points of the 20^th century (1925, 1950, 1975, 2000). The identity of these gages was published in The New York Review of Books, 14 August 2003, a year before publication of the 2004 article quoted above. Using their study decade, 1993-2003, seven of the 14 tide gages showed lower, and seven showed higher sea levels in 2003 than in 1993. Average changes in sea level at the 14 pre-selected gages were 0.36mm/yr. This is an order of magnitude less than 2.8mm/yr quoted above for the 2004 satellite data. Further, the 14-gage average sea level is actually less than the standard deviation of the satellite altimetry data. The rate of sea level change quoted for satellite altimetry in the opening sentences above is unlikely to be correct."

Biographical Information:

Cy Galvin PhD is believed to be the first practicing coastal engineer, and he remains the longest continuously operating consulting coastal engineer. He received a BS in Geological Engineering from St Louis University (thesis: Grover Gravel, 1957); a SM from MIT (thesis: Deformed Devonian Brachiopods from Maine, 1959); a PhD from MIT (Experiments on Longshore Currents, 1963). ASCE awarded him their Norman Medal and Huber Research Prize for his experiments on water waves. He has studied sea level problems for about 30 years and has interests in science and public policy, as represented by the controversy on global warming. 

Added note: Satellite altimetry is calibrated to tide gauge data and has been repeatedly "adjusted" over the years, including recently adjusted data collected up to 18 years ago.