“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 a 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 20th 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.
Cy Galvin operates Cyril Galvin, Coastal
Engineer, est 1978. As far as he knows, he was the first to begin
practice solely as a 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. Born: Jersey City, 1935;
resident: Springfield, Virginia, since 1974.