The Supermoon and SLR

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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Coeur de Lion
April 30, 2021 2:40 pm

Gawd not Miami Beach again! East coast of Florida is sinking by the way and this adds. Dear old Attenboro’ had Flooding Miami as one of the scares at the end of Blue Planet. The lying Shukman of the BBC had Flooding Miami as a direct result of Trump pulling the American taxpayer out of the Paris Agreement racket. Oh and sinking Pacific islands. And a little Maldivian who wanted climate dollars to build new airports.

Rud Istvan
April 30, 2021 2:43 pm

Kip, two separate observations.
The lunar nodal cycle is why it takes at least 60-65 years of continuous tide gauge observations to reliably estimate SLR. There are only about 70 such globally that have a related (meaning close enough) differential GPS vertical land motion correction. Those work out to about 2.2 mm/year, which closes.

The Miami Beach king tide problem isn’t just that the 1920’s plan was 4 feet which the 1926 hurricane reduced to about 2 by removing about half the original barrier island that was to be built up. Miami Beach became mostly fill dredged from Biscayne Bay. The fill is slowly subsiding as it compacts. And, Miami draws much of its drinking water from the Biscayne Aquifer, which causes further subsidence as it is depleted. Miami Beach could avoid king tide street floods as the Fort Lauderdale Isles have done (also having been built in the 1950’s completely from subsiding dredge spoils from Port Everglades on what was then mangrove swamp) by installing one way check valves on the drainage system. 80 for the Isles, done. Several hundred for bigger Miami Beach, not done. An artificially contrived sea level ‘problem’.

Rud Istvan
Reply to  Kip Hansen
April 30, 2021 8:37 pm

Sure. The former is at (among several different other sublinks), e.g. NOAA TwL report NOSO ES 0006. Or search Nils Axel Moerner last papers. He had the references also
The latter is at Or Just Search for Istvan, new productivity paradigm, 1992, strategic management journal. Google took me there.

Curious George
Reply to  Rud Istvan
April 30, 2021 3:29 pm

All Floridans should grow gills immediately. Note that once you have working gills, you don’t have to know how to swim – it becomes natural. And you don’t have to wear a face mask any more, irrespective of federal guidelines.

pHil R
Reply to  Curious George
April 30, 2021 6:43 pm

I’ll upding anyone who can work in a pithy mockery of the ridiculous mask mandate into their comment. 🙂

Reply to  Rud Istvan
April 30, 2021 7:41 pm

Miami is supposedly one of the cities most impacted by SLR.
What % of houses are actually impacted by SLR.
Here in Melbourne Australia only about 0.3% of homes are actually impacted.

Rud Istvan
Reply to  Waza
April 30, 2021 8:43 pm

Dunno. Miami Beach has a few multimillion mansions, but is mostly hotels and bars. BIG tourist draw.

Chris Hanley
April 30, 2021 3:00 pm

China, India, ASEAN and African countries are going to continue to develop using the readily available energy sources viz. fossil fuels.
Key Biscayne houses for instance sell for many millions of dollars but it’s not an ethical issue, what emissions regime the US government imposes on citizens and businesses will have no effect on the sea level trend whether or not that trend is influenced by global human emissions.

April 30, 2021 3:08 pm

Moon over Miami. Probably there’s a copyright violation in there somewhere.

April 30, 2021 3:23 pm

Excellent article.. thank you Judy.

Clyde Spencer
April 30, 2021 3:50 pm

From 2018 to 2019, global sea level rose …6.1 millimeters.

It looks to me that the satellite SLR data-rise from 2018 to 2019 is about 3mm — but then it went down about an equal amount from 2019 to 2020!

Just who do they think that they are fooling with making false claims that can be invalidated so easily?

It has been my experience that the academics writing for The Conversation frequently cherry pick their data to make their case.

Tom Abbott
Reply to  Kip Hansen
May 1, 2021 2:35 am

“I have a piece coming out on that whole outfit soon”


We need to become familiar with those who would propagadize us.

April 30, 2021 3:58 pm

As an infrastructure engineer, I am trying to get my head around SLR.
WHat do I actually have to plan for and build?
It has become very apparent that actual local SL used for engineering is NOT the MSL +SLR or Highest Astronomical Tide HAT +SLR, but the change in Mean High High Water MHHW.

Here in Melbourne Australia.

HAT is about 0.55m
MHHW is about 1.1m
Highest recorded SL is 1.4m in 1934. ( biggest east recorded flood)
The 0.55m difference is call “storm surge” but in the case of Melbourne is made up of at least 5 phenomena.
1. Local low pressure systems.
2. Wind
3. Distant low pressure systems.
4. Seiche waves ( the sloshing of the above 3)
5. River flows.

After the 1934 flood the Upper Yarra dam was built, so no more big river flows.
Thus with 86 years of SLR the highest SL for engineering purposes has not increased.
WRT to the other phenomena. Alarmists claim southern Australia will have more high pressure systems to drive drought and bushfires.

Re Planning, authorities previously used the 1934 flood as the design reference. The design high water was 1.4m + 0.2m allowance for waves = 1.6m
Due to climate change the authorities have added 200mm by 2040.
All new house must be 1.8m + 0.6m freeboard = 2.4m.
From an engineering perspective This is ridiculous.

Clyde Spencer
April 30, 2021 3:59 pm

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.

The other side of that coin is that in the next 18.6-yr lunar cycle, it will appear that the sea level rise is accelerating! I have little doubt that the MSM will jump on that like a hungry cat on a wobbly mouse.

April 30, 2021 4:21 pm

Australia set up a coastal sea level monitoring project in the early 1990s so now almost 30 years of data:
Page 8 has has the data table for sea level. Most of the sites are reportedly surveyed to compensate for ground movement.

There appears to be more increase in lower latitudes than those at higher latitudes but a big range from 2.4mm/yr up to 12.3mm/yr but that latter figure is only since 2015. The highest long term is 7mm/yr. Cocos Island almost 200mm over the period and Lorne just 70mm.

Figure 17 shows the anomaly and there is a lot of variance. Some relatable to El Nino.

Reply to  Kip Hansen
April 30, 2021 9:10 pm

I have never picked that up before I assumed they were actually correcting for changes in elevation – I appreciate having that fact pointed out.

We should be more concerned about being tipped off Australia than cooking.

This link gives some surprising detail on Australia’s northern progression – no wonder it is getting warmer:
About 70mm a year – adds up over a few years.

If Australia has tilted that much in 30 years then it literally swamps sea level rise!

Alan M
Reply to  RickWill
April 30, 2021 5:14 pm

Rick you state

Most of the sites are reportedly surveyed to compensate for ground movement.

However the text above the table states
“– the records are too short to be inferring long-term trends and have not been corrected for land movement or other parameters that may influence the reported rates.”

Northern Australia is known to be sliding beneath the Indo plate and this may account for the difference

Alan M
Reply to  Alan M
April 30, 2021 5:16 pm

Kip beat me to it

Reply to  Alan M
April 30, 2021 9:13 pm

I appreciate the observation – I had never picked up on that before. Tilting appears to be swamping sea level change – where is the pivot point?

I have always wondered if the ice loading Antarctica is driving the northern drift of the land masses! If there is some low energy state that the globe is moving toward?

Reply to  RickWill
April 30, 2021 5:22 pm

Fort Denison, Sydney.

comment image

and the nearby Bondi (open to ocean) surge pool levels.

comment image

spangled drongo
Reply to  RickWill
April 30, 2021 6:38 pm

Rick, there is also this historical BoM link showing Mean sea levels at Fort Denison from the first one in May 1914 to the last in March 2021.

The latest MSL is over 2 inches LOWER than the first:

Vertical land movement here is downward which makes that fall larger.

This is supported by the fact that Pacific atolls are increasing in size.

Reply to  spangled drongo
April 30, 2021 9:16 pm

Kip and Alan have given me the ammunition to seriously question the validity of the sea level monitoring project – I went straight to the tables without reading their disclaimer.

H. D. Hoese
April 30, 2021 4:22 pm

This study done on California Pacific Grove tides emphasizes the need for longer cycle measurements and how dangerous extrapolation is to be avoided. The lunar cycle does effect T and organisms at the extreme and has been suggested for a number of effects, difficult to provide with evidence. I could probably make a Texas freeze model with the cycle but it may take a few lifetimes.

Denny, M. W. and R. T. Paine. 1998. Celestial mechanics, sea – level changes, and intertidal ecology. Biological Bulletin. 108-115

April 30, 2021 5:23 pm

Be very wary of the power of the sea level change, we had a set of steel oil storage tanks we were erecting on the west coast of Saudi back in the 80`s that suffered with sea level changes. and they were 1/2 mile inland !
It took a couple of weeks to find out . . . the young rookie American engineer had set up the theodolite on an elevated steel paltform bolted half way up a tank and sunshine did the rest, every day, regular as clockwork, sun came up, tide came in, tanks lifted. He was soooo convinced as all his carefull measurments and plots showed exactly that, and we were in BIG trouble with a whole tank farm.
(until proven otherwise and taught about coefficient of linear expansion of steel !)

April 30, 2021 5:41 pm

Do you suppose, with all the periodic oscillations, solar cycles, etc. maybe the idea was to blame any uptick in tidal gauges adn temps on AGW, but the window has passed, and now everything will be cycling downward? Just curious.

April 30, 2021 5:47 pm

Thanks, Kip. I’ve read many of your posts (and comments) over the years and always come away equipped with more ammo for the good fight! Please keep it coming.

Clyde Spencer
Reply to  Kip Hansen
May 2, 2021 4:37 pm

You don’t get a monthly check from the oil cartel like me? [For the benefit of the resident trolls, that was sarcasm.]

Ron Long
April 30, 2021 5:49 pm

Since I’m alone in my home office I gave this story a Super Moon.

Carlo, Monte
April 30, 2021 5:56 pm

Well done, Kip. The standard circular reasoning strikes again, with the People’s Republic of Boulder, Colorado heavily implicated.

Rory Forbes
Reply to  Kip Hansen
April 30, 2021 8:40 pm

The world is at the mercy of an organized campaign to spread false information about the Climate Crisis.

And much else besides. One of CNN’s upper managers was bragging, last week, on the effectiveness of their 4 year campaign to oust Trump, using invented “news” (fake news). The BBC decided over a decade ago, as a matter of policy, to go all in on the AGW fraud …
The rest is history.

Clyde Spencer
Reply to  Kip Hansen
May 2, 2021 4:38 pm

It would be bad enough if it were limited to the “Climate Crisis.” Unfortunately, it extends well beyond that.

April 30, 2021 6:04 pm

Miami is about poor planning and subsidence.

Tombstone Gabby
April 30, 2021 8:12 pm


I seem to recall an article about there having been three different satellites involved in the measurement of sea level over the years. When the figures were plotted an upward curve was generated. However, when the figures from each satellite were plotted separately – three straight lines. Calibration of the sensors?

Sort of like tacking thermometer readings onto a tree-ring graph line I guess.

Tombstone Gabby
Reply to  Kip Hansen
May 1, 2021 10:16 am

I should have done a ‘search’ – right.

I recall reading the Jakarta article. In the late 60’s the road from the airport into the city ran alongside a drainage ‘canal’ – malodorous is a polite word.

Clyde Spencer
Reply to  Kip Hansen
May 2, 2021 4:41 pm

Read up on Sentinel 6. They have made refinements of using GPS instead of a geodetic model.

Ed Zuiderwijk
May 1, 2021 12:58 am

The NASA measures of 7″ per century and 24 cm since 1880 are spot on the Dutch tidal gauge measurements on the North Sea, 1.9 mm/yr, 19 cm per century. There is no accelleration seen in those data.

May 1, 2021 1:49 am

The moon is drifting away from the earth at a rate of 38 mm (1.5″) per year. Since 1996, the moon has drifted away 950 mm (37.5″).

Maybe the moon is dragging the ocean with it 😉

Tom Abbott
May 1, 2021 2:29 am

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

That sums it up nicely.

Sea level rise and coral reef destruction are two of the most distorted subjects connected to climate change/global warming. The alarmists are always trying to make something out of these subjects and fall flat on their faces every time (like here with this claim), but that doesn’t keep them from repeating these failures over and over.

Tom Abbott
Reply to  Kip Hansen
May 1, 2021 11:20 am

I forgot that one!

Three non-problems that alarmists can’t stop talking about.

Andy H
May 1, 2021 12:15 pm

I live near a bit of coast with 500 times that as a tidal range (12-14m).

May 2, 2021 5:22 pm

Kip Hansen

” … 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). ”

This is clearly wrong. No one needs to patch anything onto anything else.

Anyone who is able to process tide gauge data out of the PSMSL data set can see that the trend for tide gauge data for the satellite period is nearly the same as that of the satellite altimetry data:

comment image

In comparison to the layman’s humble evaluation (green) you see professional work made by Sönke Dangendorf & alii (red)

Trends for 1993-2019

Sat altimetry: 2.94 mm/year
PSMSL Bin: 3.21 mm/year (3.0 till end of 2015)
PSMSL Dangendorf: 2.8 mm/year (series ends in 2015)

The title sounds much too alarmistic to me, but the work done is, from my point of view as a former engineer, very good.

Persistent acceleration in global sea-level rise since the 1960s
Sönke Dangendorf, Carling Hay, Francisco M. Calafat, Marta Marcos, Christopher G. Piecuch,Kevin Berk & Jürgen Jensen

If you can do it better, feel free to do it.

Most people say ‘I guess Dangendorf & al. are wrong; prove me wrong’, instead of proving them wrong.

J.-P. D.

Reply to  Bindidon
May 2, 2021 5:36 pm

A hint to some self-calling ‘specialists’, before they unnecessarily reply with one or two gauge graphs showing zero trend: The PSMSL data base consists of over 1500 gauges, whose data processing isn’t quite trivial, as you have to perform (best possible) corrrection for vertical land movement (but the effect of that correction is not perceptible for the period shown in the graph above).

J.-P. D.

Reply to  Bindidon
May 2, 2021 5:43 pm

A wonderful picture made out of PSMSL data processing:

comment image

It shows the data processing moving step by step from the Swedish gauge Furuögrund, located at the end of the Bothnian Gulf, to the average of all gauges in the Northern Atlantic.

Raw data, without VLM correction for the heavy glacial isostatic rebound!

J.-P. D.

Reply to  Kip Hansen
May 4, 2021 5:52 am

Kip Hansen

I don’t know if I understand you well. What do you mean with ‘law rising’ ?

What you see represents the data transition from

  • a single tide gauge located at a place with glacial isostatic rebound, to
  • the average of more and more gauges.

If VLM was applied, the graph would considerably shrink due to the corrections (violet, blue, green and yellow data moving down, and red data moving a little bit up, because it contains subsident areas).

The graph then shows correct data, but you no longer can see the strange similarity shown by the running means (look at all the little bumps becoming flatter each time you zoom more out of the Bothnian Gulf).

If I well remember, the lifetime trend for Furuögrund moves from -8 mm/yr (raw) up to -3 mm/yr (with VLM correction). The Bothnian Gulf is a parade example for local sea level dropping even after VLM correction.

I hope the answer is what you expect.

J.-P. D.

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