Claim: An acceleration of coastal overtopping around the world

[editor’s note. It’s really hard to take this press release seriously if they consider the Katrina flooding an indicator of sea level rise. Unmaintained levies break. Absolutely nothing to do with storm surges or sea level~cr}


Research News


By combining satellite data and digital models, the researchers have shown that coastal overtopping, and consequently the risk of flooding, is set to further accelerate over the 21st century, by up to 50-fold under a high emission global warming scenario, especially in the tropics. This increase is principally caused by a combination of sea level rise and ocean waves.

Low-lying coastal regions host nearly 10% of the world’s population. In addition to ongoing erosion and rising sea levels, these areas and their unique ecosystems are facing destructive hazards, including episodic flooding due to overtopping of natural/artificial protection, as in the case of Hurricane Katrina, which hit the United States in 2005, Cyclone Xynthia in Europe in 2010, and Typhoon Haiyan in Asia in 2013 (the largest tropical cyclone ever measured). These episodic events are expected to become more severe and more frequent due to global warming, while the consequences will also increase due to increased anthropogenic pressure, such as coastal and infrastructure development, rapid urbanisation. Although the magnitude and frequency of these events remain uncertain, scientists believe that countries in the tropics will be particularly affected.

Despite the significant role ocean waves play in determining coastal sea levels, their contribution to coastal flooding had previously been largely overlooked, mainly due to a lack of accurate coastal topographic information.Measuring past events to estimate future risks

In this study, French researchers -from IRD, CNES, Mercator Océan- together with Dutch, Brazilian, Portuguese, Italian and Nigerian colleagues, combined an unprecedented global digital model for surface elevation with new estimates of the extreme sea levels. These extreme water levels contain tides, analysis of wind-driven waves and existing measurements of natural and artificial coastal defences.

The study started by quantifying the increase in global submersion events that occurred between 1993 and 2015. To accomplish this, satellite data was used to define two key parameters for coastal topography: the local beach-slope and maximum subaerial elevation of the coasts. The extreme level of coastal waters was calculated in hourly timesteps in order to identify the potential annual number of hours during which coastal defences could be overtopped in each area.

“The combination of tides and episodes of large waves is the main contributor to episodes of coastal overflow,” says Rafaël Almar, a researcher in coastal dynamics at IRD, and the coordinator of the study. “We identified hot-spots, where the increase in risks of overtopping is higher, such as in the Gulf of Mexico, the Southern Mediterranean, West Africa, Madagascar and the Baltic Sea.”Acceleration during the 21st century

The scientists also performed an initial global assessment of the potential coastal overtopping over the 21st century, by taking into account different sea-level rise scenarios. Results show that the number of overtopping hours could increase with a faster pace than the average rate of sea-level rise. “The frequency of overtopping is accelerating exponentially and will be clearly perceptible as early as 2050, regardless of the climate scenario. By the end of the century, the intensity of the acceleration will depend on the future trajectories of greenhouse gas emissions and therefore the rise in sea-level. In the case of a high emissions scenario, the number of overtopping hours globally could increase fifty-fold compared with current levels,” Rafaël Almar warns. “As we go along the 21st century, more and more regions will be exposed to overtopping and consequent coastal flooding, especially in the tropics, north-western United States, Scandinavia, and the Far East of Russia.”

Further studies will be needed on the local and regional levels to flesh out these global projections, which provide a solid basis for proposing effective adaptation measures in the hotspots identified.


2.1 20 votes
Article Rating
Newest Most Voted
Inline Feedbacks
View all comments
June 18, 2021 6:27 pm

Hard to believe this is to be taken seriously. What inanity will come next. And never, ever, ever a paper showing that global warming could be benign or, heaven forbid, better for us. That is an indictment of climate research in and of itself.

Reply to  BobM
June 18, 2021 7:32 pm

Parts of New Orleans are 2 meters below sea level. That’s pretty low lying.

Reply to  Scissor
June 19, 2021 10:48 am

That is like telling somebody that the canals in the Netherlands are low-lying areas meters below sea level.

Parts of New Orleans neighborhoods are built upon landfill.
Over the last few centuries, what little dry land in was built up. New land around New Orleans required fill to bring land above the water and turn it into dry land.

Areas filled in the twentieth century were filled with trash, dirt and sand with lots of included decaying material.
Those are the areas slowly sinking.

To cope with these areas sinking below sea level, the Army Corps of Engineers constructed dikes.

Where I lived around Canal Boulevard it was normal to order a few truckloads of fill every few years to bring yards back up to level.
There was a fence in the back yard when I moved there. When I went to remove the rusty fence which seemed short for a fence, it was because over two feet were buried.

That fill came from the Atchafalaya Basin. Very fertile sand and silt that would have normally been deposited in the swamps surrounding New Orleans during floods.

And the land and fill subsides as the decaying material is consumed.

Our house was a mile from the nearest dike. That dike fronted along Lake Pontchartrain. It was several miles further to the dikes along the Mississippi River and the Intracoastal Canal. At no place do New Orleans dikes face the Gulf of Mexico or the ocean.
.Lake Pontchartrain does connect to the Gulf of Mexico via Lake Borgne via the Rigolets.

Areas of Gulfport were wrecked by Hurricane Katrina’s storm surge. Jim Cantore was in Gulfport, supposedly above the level of the calculated storm surge.

It turned out that even though Katrina was declining in strength, the storm surge calculations were seriously underestimated and Cantore was in danger. That storm surge coupled with a direct hit by Katrina did serious damage in Gulfport.

Nothing at all to do with sea level rise, just weather and man’s arrogant ignorance coupled with poor dike design and worse dike maintenance.

Reply to  ATheoK
June 19, 2021 1:30 pm

If the Mississippi were allowed to follow it’s natural course, a large part of New Orleans would already be gone.

Reply to  BobM
June 18, 2021 9:18 pm

Oh, really, they simply need to get out there on the beaches and scold the oceans for being so “full” and/or being so frisky. /sarc

June 18, 2021 6:48 pm

Yet another study that predicts that things are going to get worse. Sometime in the future.

Reply to  MarkW
June 18, 2021 6:55 pm

It is absolutely certain that something will get worse in the future.. 😉

Reply to  David Middleton
June 18, 2021 7:40 pm

U.S. debt.
Climate change propaganda.
Ben & Jerry’s Ice Cream.

Reply to  MarkW
June 19, 2021 5:39 am

While ignoring the past … such as, if one is going to mention overtopping of levies as an “increasing risk” then any honest assessment would have to mention the Galveston hurricane of 1900 that was the single deadliest weather event in recorded US history, resulting in the deaths of somewhere between 8 thousand and 10 thousand. That Cat 4 hurricane resulted in overtopped levies, but that was many decades before coal fired electric power plants and SUVs and pickup trucks and jetliners arrived to boost CO2 concentrations in the atmosphere.

Reply to  Duane
June 19, 2021 1:38 pm

The ignoranemouses on the left don’t know history and don’t care! Take Juneteenth for example. If one were to celebrate the abolishment of slavery in the US the proper date would be December 6th when the 13th amendment was passed not that time when the Emancipation Proclamation was declared which left DE, MO. MD, KY, and Washington DC where slave could still be owned.

But leftists, including the current occupant of the WH and his puppet masters don’t know that or don’t care.

Lincoln’s address was as pragmatic a piece of politics as one can find in US history, Very effective. But it didn’t free anyone really.

Trying to Play Nice
Reply to  rah
June 23, 2021 9:15 am

The Emancipation Proclamation was issued September 22, 1862. Juneteenth celebrates June 19th, 1865 when General Gordon Granger landed in Galveston and effectively freed the last of the slaves working in Texas.

Robert Cherba
Reply to  MarkW
June 20, 2021 5:33 am

And don’t forget that a conclusion of the study is that more studies are needed. A jobs program for “scientists.”

Not Chicken Little
June 18, 2021 6:50 pm

“…clearly perceptible by 2050” they say…about 30 years from now, but THEY can already perceive it, because they are “scientists”. And the team is very diverse so they must be right! And by 2050 they’ll all be dead or retired, can’t have any predictions that can be falsified in time to show they are charlatans…

Is it any wonder that people put “science” in quotation marks? Will “scientist” jokes replace lawyer jokes? It’s the 99% that give the 1% a bad name…

Reply to  Not Chicken Little
June 18, 2021 7:25 pm

“under a high emission global warming scenario, especially in the tropics. This increase is principally caused by a combination of sea level rise and ocean waves.”

Using RCP8.5 again? “a high emission global warming scenario”? The increase is due to “a combination of sea level rise and ocean waves.”???? Ocean waves? Really? Ocean Waves are now a scary climate thing?

Oh, yeah, and it is all complicated by “increased anthropogenic pressure, such as coastal and infrastructure development, rapid urbanisation.” So, the sea level rise won’t be apparent enough to stop the coastal infrastructure development, and urbanisation, but apparently sneaks up on them all of a sudden 50 years from now.

Or, perhaps, the sea level rise is taken in stride, like always, and life goes on, and we deal with the occasional outlier storm. That is what insurance is for. Ask Warren Buffett what he thinks.

Rich Davis
June 18, 2021 6:57 pm

A competitor to EurekAlert! in the realm of climate nonsense?

Big Jumble
June 18, 2021 7:00 pm

My bathtub overnflowed when I got in during the full moon king tide after the COVID-19 19 pound weight gain circumstantial sloth self-inflicted on me caused by stress eating ice cream while watching Animal Planet nonstop. Who knew there was so much hunger out there in nature? Might as well be a sturgeon.$$

Reply to  Big Jumble
June 18, 2021 8:16 pm

Watch out for the ocean waves.

Joel O'Bryan
Reply to  Big Jumble
June 18, 2021 9:46 pm

and a bubble bath with a potent GHG.

Paul Jenkinson
Reply to  Big Jumble
June 19, 2021 5:25 am

You just watched a Sir David Attenborough special.

June 18, 2021 7:28 pm

Didn’t see the link to Eurekalert in your story, above.

From Wikipedia: link

The Research Institute for Development (French: Institut de Recherche pour le Développement, IRD) is a French science and technology establishment under the joint supervision of the French Ministries of Higher Education and Research and Foreign Affairs.

These international modeler “scientists” are political-social-planners-in-the-making. They described their methods, which aren’t terribly scientific.. This should be seen as a political/public information worst case with the purpose stated in the last paragraph:

Further studies will be needed on the local and regional levels to flesh out these global projections, which provide a solid basis for proposing effective adaptation measures in the hotspots identified.

“please, send money.”

Can’t take it as a serious geological or oceanographic study, as they assumed whatever happened in the past will get worse based on the worst-case estimations of sea-level rise and climate change driven worsening weather events.

June 18, 2021 7:30 pm

If you dig into the research paper, nowhere do they use reported ocean overtopping events in their data. They use satellite date to model coastal topology and tidal data to estimate how often overtopping is presumed to occur in their computer model. In other words, there is no evidence at all that overtopping is happening as frequently as they say, nor is there any evidence that those events are accelerating. All they have is a computer model that they created and—wonder of wonders—produced an outcome that they programmed into it. Just like the CMIP climate models.

Funny how climate alarmists always—always!—use computer models to support their claims and ignore observations of the actual oceans and atmosphere. It’s easy to program a computer to produce what you want. It’s harder to make measurements say what you want.

Joao Martins
Reply to  stinkerp
June 19, 2021 2:27 am

Very good analysis! Thank you!

H. D. Hoese
Reply to  stinkerp
June 19, 2021 7:51 am

Usual paper with only a couple of pre–2000 citations. Apparently their only real data for extrapolation is from transects in Fig. 5. France and the Netherlands are not typical of world-wide beaches, but doesn’t seem to bother them. “One of the main limitations would be due to the different impacts waves will have on different types of coasts.” Their 85 references don’t seem to cover all these, except perhaps in a few general reviews.

“Fig. 1: Schematic of the processes governing coastal overtopping and the different levels of potential flooding depending on coastal topography.”
Although their description is better, this figure would be more appropriate in a 5th grade or earlier class.

I get asked about sea level as locals sometimes even wonder about local data and conclusions. Gets tiring giving modelers a bad name.

Chris Nisbet
June 18, 2021 8:16 pm

These articles always seem to brush over the most important bits.
1) “will be clearly perceptible as early as 2050”. IOW – are not clearly perceptible.
2) “the magnitude and frequency of these events remain uncertain”. Should be the first sentence, so we don’t have to bother reading the rest and go back to doing what we were doing.
It’s almost as though they’re doing it on purpose. /sarc.

June 18, 2021 8:46 pm

At least it is something new ~ we have gone from tipping point to topping point.

Louis Hooffstetter
June 18, 2021 9:08 pm

After Katrina, I worked on a project to close the Mississippi River Gulf Outlet (MRGO), a channel dredged parallel to the Mississippi River from New Orleans to the Gulf of Mexico. During Hurricane Katrina waves came up the MRGO and smashed into the levees south of New Orleans, causing them to fail. I discovered that levees that failed were built from the material excavated from the MRGO. The material was pure peat, derived from Mississippi delta marsh grass, with zero clay or soil in it. It literally had the particle size and consistency of used coffee grounds. The dredging companies on the project tried using the material to build levees for a dredge disposal area, but it would not stack up. It literally ‘melted’ every time it rained or was exposed to water. Because the Army Corps of Engineers knew the peat/coffee grounds material could not stand up to waves or water of any kind, they put a 6″ thick clay ‘cap’ on the coffee ground levees to protect them from storms. It didn’t work. This was literally the worst possible material to use to build a levee. Levees made of sugar would have held up better. The failure of the levees during Hurricane Katrina was a man made disaster.

Reply to  Louis Hooffstetter
June 18, 2021 10:35 pm

The southern area of what is now Louisiana up to around 10,000 or 15,000 years ago was quite a bit higher than sea level (in some places I think close to 100 meters above sea level).The sea level rising that began changed things.Yet it wasn’t until around 5,000 or 6,000 years ago that any Mississippi River deltas began forming with relation to water of the Gulf. And I think it was around that same time span what is now New Orleans became an area of Cypress bogs and grass marshes. The settlement of NewOrleans was until the early 1900s only built on naturally occurring levees that were not pure peat. And only when a modern high volume water pump was designed did the city spread – but then subsidence became part of the greater urban picture.

Alan the Brit
Reply to  Louis Hooffstetter
June 18, 2021 11:18 pm

Correct me if I am wrong, but I agree the disaster was manmade, but I thought that local engineers were advising local authorities that the sea/flood defences were in a poor state of repair/maintenance, & money needed to be spent to rectify the situation, but the money was not forthcoming!!!

4 Eyes
Reply to  Alan the Brit
June 19, 2021 2:35 am

When I visited the lake levee protecting New Orleans in 1986 a fellow engineer told me the Army Corps of Engineers knew the levee needed work but money had never been forthcoming, for 40 years! Totally man-made disaster

Joseph Zorzin
Reply to  4 Eyes
June 19, 2021 3:27 am

Meanwhile, Americans spend 100 billion dollars per year on cosmetics.

Reply to  Alan the Brit
June 19, 2021 3:38 am

Was the money not forthcoming, or did it come and, like so much other government money in New Orleans and La., did it just disappear? After Katrina,if memory serves, it came to light that 100 million had disappeared from the NO school system. I suspect the money came and went poof!

H. D. Hoese
Reply to  Louis Hooffstetter
June 19, 2021 6:54 am

This was a prescient study showing how MRGO would be a bad project, hardly ever saw a ship in it, now trying to be rectified. Learning is still very slow about preventing storm damage despite all the current efforts. Rounsefell, G. A. 1964. Preconstruction study of the fisheries of the estuarine area traversed by the Mississippi River-Gulf Outlet Project. Fishery Bulletin U. S. 63(2):373-393.

This was one of several studies on the problem proving Rounsefell correct.
Shaffer, G. P., and 11 other authors. 2009. the MRGO Navigation Project: Human-induced environmental, economic and storm disaster. Journal of Coastal Research. S1(54):206-224.

This has got to be high on the list of incredibly inaccurate statements as these have been studied by geologists for lots of decades, wave cut features very interesting after storms, neither overlooked nor lack of mapping; it was a transect mapping across beaches in courses and studies.  “Despite the significant role ocean waves play in determining coastal sea levels, their contribution to coastal flooding had previously been largely overlooked, mainly due to a lack of accurate coastal topographic information.”

June 18, 2021 9:11 pm

I must have missed the links.

To this story:

To the paper:

The money paragraph in the paper:

Under RCP 8.5, the globally aggregated annual overtopping hours by the end of the 21st-century is projected to be up to 50 times larger compared to present-day.”

IMO nothing shows the bankruptcy of climate science, its transformation into an engine of Leftist agitprop, as the relentless focus on RCP8.5 – years after it has been shown to be either wildly improbable or impossible. I wrote about this in 2015, and probably wasn’t the first to do so.

Peta of Newark
June 18, 2021 9:39 pm

This is not science
Its a bunch of mentally disordered people hanging out together and catastrophizing.
Because it makes them feel good, it makes them feel superior = that they’re possessed of ‘more care’ and ‘better intentions’ than everyone else.

Made even more gratifying for them that they’re given a public stage upon which to perform this dysfunctional ritual.
Check any UK early evening soap opera, hysterical game-show or celebrity put-down show. These folks are behaving exactly like that and if me, you anyone watches that shyte, day in, day out for years & years & years, we lose track of what is ‘normal’ thinking and behaviour. Especially if we watch it with bellies full of sugar, veins coursing alcohol or lungs full of weed.

Its a social ritual they’re engaging, like the TV soaps and the office chatter they provoke next day.
e.g. ‘social drinking’ – got to be the biggest mistake anyone could make or believe in.
There is nothing social, caring, clever, sensitive or superior about being deeply chemically depressed in the company of others, it is the biggest insult you could give anyone.

The burgeoning crowds of these (haha scientist) people is a measure of how much trouble we really are in.

Having said that:
I do often wonder how all the silt and mud we now wash down our rivers affects what is seen as ‘sea-level rise.
As they say about beach profiles and depths, the mud and silt will be altering those and presumably, how far the tide rolls up any given beach whenever it comes in.
C’mon Shirls, you tell ’em: That would perfectly explain why some places are recording more ‘global’ sea level rise than others, and some even have negative Global Sea Level Rise.
Only sugar-eaters could accommodate such nonsense inside their heads, esp when they watch it every day on TV.

The sea ain’t going anywhere. We’re simply ‘filling it in’ with mud and silt and at various different depths at various different places.
Wind-blown dust falling into the sea also.

And where that dust (re) lands on the land, it causes Global Greening. The NPK, soot and organic material it carries are the REAL global greening fertilisers.
Hence all that sulphurous smut we’ve just been reading about at the bottom of the Black Sea

Joel O'Bryan
June 18, 2021 9:48 pm

Rent seekers using RCP 8.5??? Call me shocked.

Further studies will be needed on the local and regional levels to flesh out these global projections, which provide a solid basis for proposing effective adaptation measures in the hotspots identified.”

June 18, 2021 10:06 pm

I once queried in the UK’s Guardian why none of the oldest tide gauges located in geologically stable areas showed no accelerated sea level rise – just the bog standard rise of about 2.4mm a year. I was told to the extent of being shouted down, that sea level rise was not uniform.

So I then asked when the tide gauges at those locations would start to show an accelerated rise as they can’t be exempt forever. There was no reponse.

It’s pretty remarkable that those who set up those tide gauges so many years ago just happened to set them up in those locations where there would just happen to be no accelerated rise.

What are the odds of that fluke happening?

Mr. Lee
Reply to  Tedz
June 18, 2021 11:02 pm

Beautifully argued. IMHO, the single best argument againstt the climate narrative.
Cuxhaven just happens to be the longest and strongest tide gauge in the world ….and just happens to show no acceleration over 175 years? What a coincidence!

Reply to  Mr. Lee
June 20, 2021 10:37 am

The first records of the tidal gauge of Brest, France, began around year 1815, 2 centuries ago. The measured ocean level rise in this place is about 250mm from 1845 to 2021, 176 years continuously, 1.5 mm/year. No acceleration could be evidenced, too

Reply to  Tedz
June 18, 2021 11:23 pm

The Guardian makes Soviet-era Pravda and Izvestia look like paragons of honesty.

LAyot Nala
June 18, 2021 11:09 pm

97% of image scientists are. mendacious!

June 19, 2021 12:11 am

Oh, boohoo, the rich will have to give up their seaside pleasure palaces because of climate change. Now, I’m even less likely to do anything to stop climate change.

Peter Barrett
June 19, 2021 1:20 am

Sorry, lost me at “digital models”.

Joao Martins
June 19, 2021 2:23 am

In any place, coastal overtopping is occurring twice as fast as in the rest of the world!
Send the money, please!

June 19, 2021 3:21 am

What are they talking about with Katrina? Besides the levees breaking, New Orleans is sinking. Even when we bought it from France, the French told the Americans it was a lousy place to build a city.

Gregory Woods
June 19, 2021 3:32 am

Further studies will be needed

Of course!

Rod Evans
June 19, 2021 3:37 am

I have a far more basic observation that explains flooding events in our part of the world. Under woke EU rules, river dredging was made economically prohibitive because dredge waste was classified as contaminated spoil. Consequently the spoil had to be paid for and sent to land fill. Prior to this Pan EU nation’s rule, re dredge waste being toxic, it was automatically spread onto adjoining fields which helped plants to grow from the additional nutrients. That has been done for centuries past, but no more. Now rivers are not dredged and guess what flooding from even modest rain fall now happens.
It has nothing to do with global warming and everything to do with pseudo global environmentalism and the growing global woke movement. I think they park that nonsense under the banner of “rewilding”. Well it makes me pretty wild, that’s for sure.

Patrick MJD
June 19, 2021 3:42 am

Of course they forget Louisiana is a low-lying swamp.

Reply to  Patrick MJD
June 19, 2021 9:20 am

It’s also very wet and hot.

June 19, 2021 4:43 am

one certainty is that with growing population coastlines will continue to be developed , and disproportionately so . at the same time water tables underneath development will continue to be drained , waterfronts built on landfill will continue to sink , shorelines will erode . time was , poor people often lived along the water’s edge where they were sometimes at risk while the well to do lived on higher ground where it was safer to build . as humans got less connected to their environment and more wealthy it is now the rich who are increasingly desirous of their waterfront property while ignoring the risks . with each passing year more and more expensive infrastructure is built in harm’s way . and CC is blamed for the growing risk and expense .

June 19, 2021 4:59 am

“combined an unprecedented global digital model” So, just the same lies reworded for re-release by the same lie spewing liars.

Nicholas Harding
June 19, 2021 5:36 am

I have been sailing since the late 1970s from the same mooring; I have not noticed any sea level rise in Long Island Sound or Block Island Sound. Mind you, I am just one observer who does not have a computer model, but this problem is not visible to the naked eye, if it exists at all. Should there be meaningful sea level rise (2-3 feet) in the next 2500 years, simple barriers can be erected. For those who choose to live below sea level, either now or then, caring for dikes and levies should always be a priority for local governments.

June 19, 2021 6:35 am

“Further studies will be needed”

June 19, 2021 7:34 am

Not definite but words like could to indicate what might happen or not.

June 19, 2021 9:17 am

When you spill a bucket of water it disperses. The level of water in a container is a function of size and volume. 300 years ago N.O. was a flood plain of a river delta. The delta’s flood plain continues to rise while N. O. has been boxed off for more than 200 years.The older the box the more unreliable.

June 19, 2021 1:28 pm

I’ve only noticed a sever and sustained over topping of climate change propaganda lately.

Mike Lowe
June 19, 2021 2:22 pm

“….digital models”! Don’t need to read any more!

June 19, 2021 6:24 pm

A high-emission scenario? Also known as RCP 8.5? The one that scientists say is increasingly unlikely?

June 20, 2021 5:44 am

Hard to take these predictive articles seriously when the price of waterfront property is still astronomical.

Theresa W Chavez
June 21, 2021 12:50 am

Regardless of the climate, the frequency of overturning is increasing exponentially and will be clearly felt in 2050. By the end of this century, the intensity of acceleration will depend on the future trajectory of greenhouse gas emissions, and thus on sea-level rise. In the case of high emissions, the global number of overturning hours may be 50 times higher than the current level. Some car manufacturers, such as Lexus, focus on the efficient use of green energy to reduce the use of oil. In addition, automobile exhaust emissions are also gradually reduced. In this way, greenhouse gas emissions will slow down.

Trying to Play Nice
Reply to  Theresa W Chavez
June 23, 2021 9:30 am

Over the last 6 years Lexus seems to be focusing on lowering sales numbers to reduce greenhouse gas emissions.

Verified by MonsterInsights