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.

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