Has it actually ever been possible to measure millimetres of fluctuation in sea level ?
Or, is it simply a case of some dabbling in science to get a mention in some journal ?
I have yet to see the sea surface so calm that a millimetre could be discerned.

My, my, my. When the cat’s away…

We have Yuyutsu citing predictions that were never made (not very enlightened), and mhaze insisting that the IPCC "didn’t predict anything for 2025," even though his own source contradicts him.

SAR’s sea-level projections were presented as time-series curves from 1995 to 2100. A projection to 2100 necessarily includes projections for every year in between, including 2025. This is why Törnqvist’s team were able to extract the ~8 cm value from the same figures mhaze linked. It’s not "three-card trickery." It’s how every multi-decadal climate projection is interpreted.

The "huge range" mhaze keeps waving around (15-95 cm) does not represent random guesses. These are conditional scenarios based on different emissions pathways. Once we know which pathway the world actually followed - namely, the high-emissions IS92 range - the correct comparison is with that curve. You don’t validate a model by comparing it to scenarios that never occurred.

Then there’s the attempt to dismiss the observed rise because NASA reports ~10-11 cm rather than the rounded "about nine centimetres." But those numbers aren’t contradictory. NASA, NOAA, Copernicus and CU all show roughly the same ~10 cm rise since the mid-1990s. Törnqvist uses rounded figures in public communication, not because the underlying data is imprecise, but because decimal pedantry isn’t required to grasp the result:

1995 projection: ~8 cm.
Observed: ~9-11 cm.
A 30-year-old model got it right.

Claiming the IPCC "didn’t predict 2025," rejecting all four major sea-level datasets, and insisting that choosing the scenario that matches real-world emissions is "cherry-picking" isn’t scientific critique. It’s motivated avoidance.

And Yuyutsu’s "300 metres" rise? Pure folklore. No such prediction has ever appeared in the scientific literature.

The core point the science keeps confirming - and the thread keeps dancing around - is simple:

The SAR model’s short-term sea-level projections were remarkably accurate. That’s why this study matters. It shows the physics was sound even three decades ago.

Everything else here is noise to avoid acknowledging that the prediction matched reality.

Tried to look up total World shipping displacement & the figures vary from 2-3 billion tonnes, to 10 billion & 12 billon in 2024. Depends on which organisation does the surveys. This of course varies from fully laden to ships in ballast.
I can't find anything on how many tonnes of other displacement there is from run-off sediment & land reclamation.
there are 361 million square kilometres of water & 1 mm of water in one square kilometre is 1000 tonnes.
I only have five fingers on each hand at this stage so anyone with a good calculator can do the sums.
Some bright spark ones queried the difference between high & low tide.

Dear John,

I never claimed that I got this 300-meter information from IPCC or SAR: if only because I didn't (and still don't) know what these acronyms stood for!

But my friends and I did hear of it, around 1990. Perhaps from the radio, perhaps from the printed newspaper, or perhaps from friends: surely you don't expect me to remember some 35 years later where I heard it from!
It was based on the assumption that all glaciers will melt.

I had no particular reason to suspect the information:
It wasn't April Fool's day.
Nobody was to gain anything from it at my expense.
The topic was not yet controversial at the time.
It was only decades later that I heard about Margaret Thatcher, etc., etc.

So I took it at face value.
OK, so the seas are going to rise by 300 meters - what should I do?

I checked the maps of my vicinity to see which areas are above 300 meters.
There weren't much, but still there were some.
If I had the money at the time then I would purchase some farm-house in the higher regions.
But since I didn't, there was no change in my course of action - just continue saving.

And by then came the news: no, it's not 300 metres, that was a calculation error - it will only be 61 meters.

It was then that my brother saw his opportunity:
he happened to own an orchard, sloping down with the top edge at 63 meters above sea level. There was also a small dilapidated cottage at the top.
So he decided to build a big house next to the cottage, renovate the cottage and join the two. Some years later he moved to that house.
He was truly hoping to have a private beach there!
Now where is it?!

Later on, "they" (whoever they were, I don't remember) revised it down that the sea will only rise by 3 meters.
I then sighed in relief: "all that for just 3 meters?" and haven't thought about it again for a long time.

Yuyutsu,

What you've described isn't a scientific prediction being revised. It's a rumour evolving as it passes from person to person, with no identifiable source, no paper, no institution, no author, and no mechanism.

That matters.

There has never been a credible scientific claim, at any time, that global sea level would rise by 300 metres, 61 metres, or even 3 metres this century. Those numbers don't appear in IPCC reports, glaciology papers, or coastal science. Not in 1990. Not later. Not ever.

The only figure that vaguely resembles your memory is this:
If every land-based ice sheet on Earth melted completely, over many thousands of years, global sea level would rise by roughly 65-70 metres. That is a theoretical maximum, not a forecast, not a scenario, and certainly not something scientists ever suggested would happen on human timescales.

That distinction is crucial. A physical upper bound is not a prediction.

What seems to have happened is that an abstract scientific fact was stripped of its context, exaggerated in transmission, and then remembered as a concrete warning. That's very human, but it doesn't tell us anything about climate science or its reliability.

By contrast, what's being discussed in this thread does have a traceable source:
the IPCC's 1995 projections, published in SAR, and a modern peer-reviewed analysis showing that their short-term sea-level projections were remarkably accurate.

So the takeaway isn't "scientists kept changing their minds". It's that unattributed stories are not science, and shouldn't be treated as evidence against it.

Your anecdote explains how confusion spreads. It doesn't undermine the data being discussed here.

That's the key difference.

On another note, there is something irreconcilable between "Yuyutsu the Enlightened" and "Yuyutsu the Denier", and I think this thread exposes it rather cleanly:

- "Yuyutsu the Enlightened" values wisdom, openness, and detachment from dogma.
- "Yuyutsu the Denier" clings to unverified memories and treats their erosion as evidence of institutional failure.

Dear John,

«What you've described isn't a scientific prediction being revised.»

You are banging on an open door - I never said it was, I never even mentioned the word "science".
If other participants here did, then it is between you and them to sort out, but please do not get me involved.

As for "Yuyutsu the Denier", I do not deny (or affirm) climate science, I just happen not to relate to it, it is not my cup of tea.

At the time, it did not even occur to me to consult science on the matter - I just took it as fact just as most young people do: "the radio said - the radio must be correct, now what do I do?". You must remember that in 1990 the information was not available at the tip of our fingers like today, so had I been really keen to know the scientific side, I would have to use my legs rather than my fingers, walk into university libraries and physically knock on various doors, which would take me way more time than I had available.

Back then also, you should remember that very few even had an idea that the information in question may be disputed or political.

I understand well about the theoretical upper limit of 65-70 meters, but for that one would have to know the world-wide volume of glaciers and unless one specialises in that area, I don't recall they ever taught that in my school.

So OK, it wasn't science on the radio but someone else, now who exactly is to compensate my brother for his missed private beach?