30 years of sea-level rise

TOPEX/Poseidon, the first satellite to track global sea level was launched 30 years ago today. Sea level rise is one of the most damaging impacts of climate change and will have a global macroeconomic impact. The technique is radar altimetry, bounce radar pulses at the ocean and measure how long it takes to bounce back. Get a distance using the speed of light. Do some complex math to filter out waves and tides and orbital geometry and out pops the sea level.

30 years ago we knew climate change was a threat, and we knew the ocean was a critical component of the climate system, but we had few observations of the oceans. The 1992 NASA press release at launch quotes NASA Program Scientist Dr. William Patzert, “Without TOPEX/POSEIDON, there is no possibility of meaningful long-term climate forecasts.” https://www.jpl.nasa.gov/news/press_kits/topex_poseidon.pdf

Through the decades satellites aged and were replaced, NASA is currently on their 5th, giving us a continuous detailed global 30 year record. The graphs at the link below show the inexorable sea level rise, 10 cm in 30 years. NASA project scientist Josh Willis concludes: “The rise of sea level caused by human interference with the climate now dwarfs the natural cycles. And it is happening faster and faster every decade.”

The science is unequivocal. How we respond is politics and inappropriate for this board. Long term investors who care about macroeconomic factors should consider sea level rise.



Sea levels have been rising since the end of the last ice-age.


The science is unequivocal.

There was an article in the Guardian a few weeks ago where a climate scientist pointed that the size and scope of the current heat waves in Europe are well ahead of what the climate models were predicting. He called his colleagues who weren’t issuing hair-on-fire warnings “climate appeasers”.

Another example of “Late Empire” dysfunction – Nero fiddling while Rome burns.



Another example of “Late Empire” dysfunction – Nero fiddling while Rome burns.

Or just muddling through. 10cm in 30 years – that’s 3mm per year.

And, surprisingly, land areas are expanding.

The researchers analysed satellite images recorded by NASA’s Landsat satellites, which have observed the Earth for decades…

Coastal areas were also analysed, and to the scientists surprise, coastlines had gained more land - 33,700 sq km (13,000 sq miles) - than they had been lost to water (20,100 sq km or 7,800 sq miles). “We expected that the coast would start to retreat due to sea level rise, but the most surprising thing is that the coasts are growing all over the world,” said Dr Baart.



Just for the record (and the whole truth):

Between about 21,000 years and about 11,700 years ago, Earth warmed about 4 degrees C (7.2 degrees F), and the oceans rose (with a slight lag after the onset of warming) about 85 meters, or about 280 feet. However, sea levels continued to rise another 45 meters (about 150 feet) after the warming ended, to a total of 130 meters (from its initial level, before warming began), or about 430 feet, reaching its modern level about 3,000 years ago.

From about 3,000 years ago to about 100 years ago, sea levels naturally rose and declined slightly, with little change in the overall trend. Over the past 100 years, global temperatures have risen about 1 degree C (1.8 degrees F), with sea level response to that warming totaling about 160 to 210 mm (with about half of that amount occurring since 1993), or about 6 to 8 inches. And the current rate of sea-level rise is unprecedented over the past several millennia.




Or just muddling through. 10cm in 30 years – that’s 3mm per year.


From now on the sea-level rise is not going to be linear growth any longer. It is going to be geometric growth.

Sea level along the U.S. coastline is projected to rise, on average, 10 - 12 inches (0.25 - 0.30 meters) in the next 30 years (2020 - 2050), which will be as much as the rise measured over the last 100 years (1920 - 2020). Sea level rise will vary regionally along U.S. coasts because of changes in both land and ocean height.



P.S. - There’s nothing like sitting through a series of presentations about all the ways one of the most imperiled glaciers on Earth to get the blood flowing.

The American Geophysical Union’s annual meeting kicked off with a splash of news about Thwaites Glacier. If there’s one Antarctic glacier you need to care about, it’s this one. (Though, really why choose one?) Dubbed the “Doomsday Glacier,” Thwaites is in extremely rough shape and a key portion of it could lose its grip on the bedrock by the end of this decade. That, in case it’s not clear, is bad.

The floating part of the glacier holds back a basin of land ice that, if dumped in the ocean, would unleash roughly 10 feet (3 meters) of sea-level rise. That won’t come all at once if the ice shelf becomes unmoored. But the collapse of Thwaites would set the world on a dangerous trajectory in the decades and even centuries to come. Whether we’re on that trajectory or not is something the researchers will continue to probe. But the state of things right now is still worrisome.



Where did they find high-precision data on what the natural cycles were doing before humans started digging large quantities of carbon out of the ground and putting it back into the atmosphere?

Did they locate the ancient Egyptians’ satellite data? Or maybe the dinosaurs’?


Ever heard of Doggerland?

Doggerland was an area of land, now submerged beneath the North Sea, that connected British Isles to continental Europe. It was flooded by rising sea levels around 6500–6200 BCE.

8 MILLENNIA sea-level rise!!!

Sea levels have been rising and falling since there were seas.

Climate has been changing since there was climate.

The Captain
loves the quietude of the sea. Seas do throw tantrums.


Sea level along the U.S. coastline is projected to rise…

Sure, but the projections may be overstated. To avoid going into the weeds too much, let’s use the NASA interactive map, “IPCC 6th Assessment Report Sea Level Projections” from last year, found here:

Move the map and click on Boston, then click on ‘full projection’. There are six different scenarios, but they all show the same sea level estimate of 17cm for 2030. For 2020 the number is 10cm, so they are expecting 70mm of sea level rise between 2020 and 2030, an average of 7mm/year.

Here is the measured Boston sea level data from NOAA since 1920:
The trend is 2.9mm/yr with no acceleration observable. To reach an average SLR of 7mm/yr the rate would have to accelerate to more than 15mm/yr by the end of the decade.

That seems highly unrealistic. Does anybody want to make a $100 wager (not adjusted for inflation) with the proceeds going to a charity chosen by the winner?


Did they locate the ancient Egyptians’ satellite data? Or maybe the dinosaurs’?

Read an article in Smithsonian Magazine 10-15 years ago talking about old master painters and their artwork involving Venice and their canals. They used the centuries old paintings and compared them to current photographs to determine if sea levels were rising. The results were iffy because there was the big question of are the structures sinking?

Tried to search the magazine website for the article but no luck.



The graphs at the link below show the inexorable sea level rise, 10 cm in 30 years.

10cm in 30 years.

WoW*!* I’d better out my old water wings!

The thing about these things is that they are always at least 10+ years in the future so by the time they don’t happen** nobody remembers or cares.

**Or happen and nobody notices.


Over the three decades several different satellites have been used to measure sea level change. Kleinherenbrink et al. looked at the drift between systems and conclude there has been no statistically significant increase.

“Based on four different weighting methods used in a tide-gauge comparison it is determined that TOPEX is drifting and not ERS. Therefore, we suggest to calibrate the TOPEX GMSL record with the crossover of ERS1&2 after the removal of cal-1. The calibration reduces the observed acceleration in GMSL, so that it becomes statistically equivalent to zero at the 95%-confidence level.


Some good news for Venice, Italy. For a century (1870-1970) the sea level there rose at a rate of 2.6mm/yr. Munaretto et al. write that half was from subsidence and half from the sea. Then, from 1970 to 2000 the trend slowed dramatically to 0.7mm/yr.

This month Fogarin et al. published their study of the Venice shoreline/littoral for the 2015-19 period. They write: “Overall, the case study littoral reveals to be stable or mainly subjected to accretion.” (5% of the coast is eroding, 36% is stable, 52% is accreting and 7% was not evaluable).

Flood Protection in Venice under Conditions of Sea-Level Rise: An Analysis of Institutional and Technical Measures


Part of that additional 5,000 square miles is urban landfill.


Not at 10 cm per 30 years.

Our grandkids, my great nephews and nieces will face all of Florida under water.


The average elevation of Florida is some 20 feet according to this map:

or 100 feet:

or 58 feet:

Taking the average yields 60 feet.

Who knows how long our grandkids will live, maybe another 80 years? That would imply an average sea level rise of 9 inches per year – 230 mm/yr.

As you probably know, the current rate is 3 mm/yr so, no, our grandkids will not face all of Florida under water.

Cool it with the apocalypse

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That is NOT the conclusion of Kleinherenbrink et al. Their conclusion is that uncertainties in the satellite data prevent the acceleration they do see from being statistically significant.

As a consequence, it is likely that a climate-driven acceleration is present in the altimetry-derived GMSL time series, but it is not certain.Note that the inability to state that an acceleration is present with certainty using satellite radar altimetry does not imply there is no acceleration at all. Its estimated value in this study is actually in line with the results of the 20th-century tide-gauge-based GMSL reconstruction by Dangendorf et al.17, notably 0.018 ± 0.016 mm yr−2. The uncertainties in the altimetry-derived estimate, however, cause the same acceleration to become statistically equivalent to zero at a 95%-confidence level.

Yes, humans are increasing coastal landmass faster than the rising sea is taking land away. However, all this new land is low-lying and subject to increasing flooding as sea levels rise. You failed to include the following observation from your linked article:

“About 70% of coastal land expansion has been carried out in low-lying regions that are likely to be exposed to extreme sea level rise by the end of the century. Both environmental impacts and projected coastal inundation suggest these developed coastlines are not sustainable, but cities will likely continue to build them, the authors said.”

They will certainly face a future where most of coastal FL will be subject to frequent flooding. Insurance for buildings will be very expensive or unavailable. The unavailability of insurance will mean that sustainable habitation along the FL coast will be increasingly not economically viable.


Yes, we agree. There is no statistically significant acceleration.


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C’mon, do you not see the difference between yours and my portrayal of the authors’ conclusion?

DrBob2: “Kleinherenbrink et al. looked at the drift between systems and conclude there has been no statistically significant increase.”

me: “Their conclusion is that uncertainties in the satellite data prevent the acceleration they do see from being statistically significant.”

You imply the authors believe there is no increase in sea levels. The authors’ explicitly state that climate-driven sea level rise is likely. It is a not-so-subtle form of misrepresentation by providing insufficient context, particularly given the subject of this thread.

It is like saying Lincoln concluded that the Gettysburg battlefield was not honorable based on the phrase: “…we cannot dedicate, we cannot consecrate, we cannot hallow this ground…”. Context is really important.


Lets keep sucking tailpipes then. Thanks. Lets do nothing and save money…what was it? Because it would cost vast amounts of money compared to doing nothing…

Back to square one…no point in believing the information on the do nothing side of things.

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