The Supermoon and SLR – Watts Up With That?

The Supermoon and SLR – Watts Up With That?


News Brief by Kip Hansen – 30 April 2021

Dr. Judith Curry sent out a tweet about this article at The Conversation:  “This supermoon has a twist – expect flooding, but a lunar cycle is masking effects of sea level rise“.  The piece is written by Brian McNoldy, a Senior Research Associate, University of Miami and written in conjunction with Covering Climate Now — the climate news propaganda effort headed up by the Columbia Journalism Review and The Guardian.  The Conversation is a member of Covering Climate Now  and a search of their website shows they have published, so far, a total of 86 articles in cooperation with that organization.

McNoldy does a good job explaining what Lunar Nodal Cycle is and how it affects apparent local Relative Sea Level Rise.  McNoldy claims:

“Right now, we’re in the phase of an 18.6-year lunar cycle that lessens the moon’s influence on the oceans. The result can make it seem like the coastal flooding risk has leveled off, and that can make sea level rise less obvious.”

“Global sea level is still rising with the warming planet, and that 18.6-year cycle will soon be working against us.” 

“Once we reach the bottom of the cycle around 2025 and start the upward phase, the lunar nodal cycle begins to contribute more and more to the perceived rate of sea level rise. During those years, the rate of sea level rise is effectively doubled in places like Miami.”  [source ]

All that is absolutely true and McNoldy gives us some neat graphics (also available at the wiki) and the de riguer  photo of Miami’s below normal high tide intersection flooding at Spring or King Tide.

The problem with the article is that it fails to point out that contribution of the Lunar Modal Cycle is  Plus or Minus One Inch.  The data is “hidden” in  his otherwise fallacious graph here:

Why do I call this graphic “fallacious”?  I do so because it shows, for Miami Florida, Sea level Rise of 5 inches from 1996 to today, which is a bit high – actual data shows maybe 4 inches.  But McNoldy gives the trend as 0.23 in/yr (5.84 mm/yr).

Let’s see what NOAA says for tide station 8723214 Virginia Key, Florida (the official station for Miami, FL):

McNoldy’s annual trend is given at twice the NOAA rate of 2.97 mm/yr for Miami.  McNoldy references a 2018 study by Steven Nerem and his “sea level is always accelerating” team at University of Colorado Boulder

And yet:

NASA says current satellite-measured Sea Level Rise is about 3.3 mm/yr, with a century-long trend of “nearly” 1.78 mm/yr.   There have been multiple attempts to make the latest 25 years of data show dangerous acceleration – but anyone with eyes can see that it just ain’t so.  Note that the starting date of 1993 for the above graph is dictated by the beginning of the satellite Sea Level record – to go back a century, one must use Tide Gauge data and patching the satellite record onto the tide gauge record produces an invalid time series (apples and oranges). 

[Late addition: Note that NASA’s long-term estimate of Global Sea Level Rise over the last 100 years is “nearly” 7 inches. This is less than the usually stated “8 inches” per century in the general sea level literature. The current statement from NOAA is “8–9 inches (21–24 centimeters) since 1880,” NOAA throws in, in their usual short-sighted advocacy-mode, “From 2018 to 2019, global sea level rose 0.24 inches (6.1 millimeters).” Try to find that 6 mm jump in the official NASA graph above.]

McNoldy mixes up speculative measures of future SLR with actual Relative Sea Levels experienced on the ground at specific location and attempts to throw a scare with the Supermoon and the Lunar Modal Cycle (a whole inch, currently down trending and in another five years, it will be up trending). 

And that, making harmless information scary, is the whole purpose of the Covering Climate Now propaganda machine.

Bottom Line:

Miami, Florida has high tide flooding because much of Miami Beach (particularly) is built within a foot or two of normal high tides, and some portions are below normal high tides.  So, of course, Miami will experience tidal flooding again at these predicted higher tides.  For Miami’s real Sea Level story, see my earlier essay:  Miami’s Vice.

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Author’s Comment:

I have written a lot about Sea Level and Sea Level Rise here at WUWT.  This link will take you to a search results list of my Sea Level essays.     Whereas, this link covers all Sea Level Rise essays at WUWT.

There has been a lot of nonsense published in the mass media about dangerous sea level rise – and it is, mostly – non-science.

Glad to answer your questions, address them to “Kip…” so I see them.

Thanks for reading.

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