Here we go again. An obscure, methodologically poor, paper published with little to no review makes a convenient point and gets elevated into supposedly ‘blockbusting’ science by the merchants of bullshit, sorry, doubt. Actual scientists drop everything to respond, but not before the (convenient) nonsense has spread widely. Rebuttals are written and submitted, but by the time they are published everyone has moved on.
If that sounds familiar, it’s because it happens a lot. In climate science, one classic example was Soon and Baliunas (2003) which instantly made it’s way to the Senate floor (via Inhofe’s then aide Marc Morano). Other examples abound. So what is this week’s example?
As Dessler et al report laid out convincingly last week, and in multiple posts by Tamino/Grant Foster, the sea level chapter in the DOE climate science ‘critique’ was notably poor. They highlighted 5 specific US tide gauge records, showed only four of them, declared that no acceleration was visible, and concluded that no acceleration was present anywhere. Curiously the 5th record (that wasn’t shown) has a very clear acceleration. They then bungled the referencing of the projections and invented a NOAA projection that did not correspond to anything real. Notably, they did no actual analysis. Actual analyses of the tide gauge record show that acceleration is sea level rise is not only widespread, but it is increasingly clear:
Conveniently, rather than defend the indefensible, one of the authors (Judith Curry) in response latched onto a new paper that apparently agreed with her prior vibes. The new paper is Voortman & de Vos (2025) (VdV25) which was published on Aug 27, and hit the contrary-sphere a few days later heavily boosted by Michael Shellenberger and a few others. This paper claims that acceleration in 243 global tide gauge records is only significant in 4% of them. This, to be clear, is rubbish. But as always in such papers, it takes a little work to figure out what has gone wrong.
Fortunately, a group of scientists led by Bob Kopp, have quickly put together a rebuttal and request for a retraction (that has been submitted to the journal): Kopp et al. (2025). In it, they point out that this analysis has in fact already been done properly (Wang et al, 2025, published before VdV25 was submitted), and then go on to explain the basic errors.
Apart from the basic lack of context that happens when you ignore the satellite record, the main issues are that the statistical model they use is overly complicated and not properly described, the statistical tests for significance are not applied properly, and the correction for multiple hypothesis testing (which assumes there is no correlation across tide gauge records) is just wrong and all but guarantees their erroneous result.
Curiously, almost all of these errors were also made in an earlier Voortman paper, and were raised by the commenters on that paper at the time (Le Bars et al., 2023)! [Update: They were also noted in a blog post by Scott Simmons].
How will this all play out in the public discourse? The process of comments, replies, and retractions is relatively slow (multiple months to a year) and even with this preprint quickly available, none of the promoters of VdV25 will deal substantively with any of this (they have not done, and will not do, any analysis themselves). It may well be that VdV25 never gets raised again, having served its purpose as a momentary distraction from the critique of CWG report. Whether or not it gets retracted is not really relevant to that.
We have seen this playbook many times before. Judith Curry and Michael Shellenberger are following in the (late) Pat Michaels’ footsteps who continually championed many new ‘blockbusting’ papers that were always on the verge of undermining the climate consensus, but that (somehow!) never quite did. Once folks lose the ability to check these things for themselves, and start basing claims on vibes, their estrangement from the scientific community hardens and the seriousness with which their opinions are taken decreases.
This little episode thus tells us very little about sea level rise acceleration, but quite a lot about the seriousness of the people involved.
References
- H.G. Voortman, and R. De Vos, "A Global Perspective on Local Sea Level Changes", Journal of Marine Science and Engineering, vol. 13, pp. 1641, 2025. http://dx.doi.org/10.3390/jmse13091641
- R.E. Kopp, J. Church, S. Dangendorf, B. Fox-Kemper, I. Haigh, D.L. Bars, G.L. Cozannet, R. Nicholls, M. Oppenheimer, C. Piecuch, R. Riva, A. Slangen, V. Srikrishnan, P. Thompson, R.S.J. Tol, and R.V.D. Wal, "Faulty science and faulty statistics can't stop sea level acceleration: An expression of concern regarding Voortman, H. G., & De Vos, R. (2025). A Global Perspective on Local Sea Level Changes. Journal of Marine Science and Engineering, 13(9), 1641.", 2025. http://dx.doi.org/10.22541/essoar.175766862.22299902/v1
- J. Wang, X. Zhang, J.A. Church, M. King, and X. Chen, "Near‐Term Future Sea‐Level Projections Supported by Extrapolation of Tide‐Gauge Observations", Geophysical Research Letters, vol. 52, 2025. http://dx.doi.org/10.1029/2024GL112940
- D. Le Bars, C. de Valk, I. Keizer, A. Jüling, R. Van de Wal, S. Drijfhout, and E. Lambert, "DISCUSSION ON: Robust validation of trends and cycles in sea level and tidal amplitude in the Dutch North Sea", Journal of Coastal and Hydraulic Structures, vol. 5, 2025. http://dx.doi.org/10.59490/jchs.2025.0042
The link for Kopp et al just returns this RealClimate post.
[Response: Sorry – fixed now.]
How can anyone so thoroughly aware of gravity gradiometry and the capabilities of GRACE as a BP Chief Scientist turned Energy Undersecretary shun the fine-tuned geodetic data streams of satellite constellations in favor of eyeballing Victorian tide gages ?
Steve has read the dailies on all this stuff over the course of decades in government, yet he and Secretary Wright seem to take their lead from the comic book quality playbooks of the CO2 Coalition, the Heartland Institute
Russel Seitz: “ How can anyone so thoroughly aware of gravity gradiometry and the capabilities of GRACE as a BP Chief Scientist turned Energy Undersecretary shun the fine-tuned geodetic data streams of satellite constellations in favor of eyeballing Victorian tide gages ? ”
His ideology and/or financial self-interest trumps his ethical/intellectual integrity?
A rhetorical question, I know. It’s a fair reminder that dishonesty comes in all shapes, sizes and levels of ability.
Same with stupidity. Anyone can say or do stupid things, though at some point, when they willfully commit to it and even celebrate it, I think it’s fair to say that it’s part of their identity, and that they are indeed just plain stupid. You’d think, therefore, that they’d be flattered when you acknowledge it, but no, they’re not. Because they’re stupid. Education won’t fix that. Therapy maybe… or peer pressure…
Not pointing any fingers at any particular troll, of course.
“Apart from the basic lack of context that happens when you ignore the satellite record…”
For some other satellite evidence from the other side of the world… and to add just a little balance to this controversial topic…
“Another study related to sea-level rise (Webb and Kench 2010) appears to contradict the general anticipation that the impacts of climate change will eventually make low-lying reef islands unable to support human occupation. It uses aerial and satellite images taken over the past 60 years, a time during which there is evidence that sea levels have risen, to compare the landform dynamics of 27 atoll islands in the central Pacific Ocean. The study found that as a whole, instead of declining, the islands grew in land area by a total of 63 ha or seven percent.
The research findings show that although sea level in the central Pacific Ocean rose by about 2.0 mm/yr over the study period and that all 27 islands changed physically during that time, there is considerable variation in the amount and style of change between and among the islands, with an overall net increase in land area; 86 percent of the islands remained relatively stable or their outline or shape increased in size. Twelve of the 27 islands increased in size by more than three percent but only four islands reduced in area by more than three percent.”
2.0 mm/yr for 60 years… 4.75 inches.
https://ui.adsabs.harvard.edu/abs/2010GPC….72..234W/abstract
Those 2 authors have published more recent papers on this area, if people are interested:
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2023EF003924
and
https://www.sciencedirect.com/science/article/pii/S0169534723002987
Ah, yes. Thanks for adding “a little balance.”
Brief correction: second set of links is from ‘mev’ not KT, apologies.
Another useful link:
https://science.nasa.gov/earth/climate-change/sea-level-101-part-two-all-sea-level-is-local/
[until Trump admin censors it]
This reference is dated 2010. 2.0 mm/year is wildly inaccurate. While sea level rise is somewhat local, we are not going to have a sink in the middle of the Pacific with a wall around it making those islands stop disappearing (already in evidence). The incredible nature of these claims does not make people rush to see more.
from one of your subpost links (2024): “Under present-day sea levels >25% of Tuvalu’s land area floods once every 5 years and >50% of land area floods once every 100 years. Our results indicate a significant increase in severity and frequency of extreme coastal flooding due to climate change with present-day 1-in-50-year floods occurring more than once every 5 years by 2060. This study highlights the pressing need for ambitious and large-scale adaptation solutions. The methodology presented here is suitable to be used in other Pacific Island locations.”
For basics: https://en.wikipedia.org/wiki/Sea_level_rise
[I arbitrarily chose a few of the many fact-based treatments on offer]
https://sealevel.nasa.gov/news/282/nasa-analysis-shows-unexpected-amount-of-sea-level-rise-in-2024/
https://www.nature.com/articles/s43017-025-00667-w
ClimateCentral does good work on tools and data:
https://www.climatecentral.org/climate-matters/sea-level-rise
KT’s other subpost link posits recreating land in the middle of a rising ocean (2 mm/yr, beyond weird), at best well meaning, unlikely to an extreme.
Susan Anderson, thanks for the link to the nature reviews earth & environment 11 Apr 2025 paper titled Sea level rise in 2024. Good to know…
https://www.nature.com/articles/s43017-025-00667-w
ICYMI/FYI, see my Submission (#26) to the NSW Parliament Joint Standing Committee on Net Zero Future re their inquiry into Emissions from the fossil fuel sector:
https://www.parliament.nsw.gov.au/lcdocs/submissions/91844/0026%20Geoff%20Miell.pdf
Attachment (landscape format) Slides #12-16 may be of interest re SLR.
Yes, Susan, thanks for the Nature Reviews link!
Me, before: “Sea level rise” refers to d(sea level)/d(t). Tracked by satellite, airborne, ship, and buoy observation, taking tides into account. Data still insufficient, but predicted to be accelerating upward from baseline.
Well, I’m behind:
Hamlington et al.: Global mean sea level (GMSL) has risen more than 10 cm since 1993, and the rate at which GMSL is increasing has doubled over the same time period
Me, now: And what does our scientific metaliteracy tell us about the hierarchy of reliability? Making no immodest claims for my command of either Calculus or comment formatting, it appears SLR acceleration (i.e. increasing 2nd time derivative of sea level: “↑ d²(sea level)/d(time)²”) over the last 30 years is sufficiently demonstrated. I appreciate the correction, because scientific progress matters critically in this context. Dang, it’s hard to keep up! Time flies when you’re getting old.
Good grief, I really don’t know what I’m doing. Not only should my self-quote have been italicized, but the Nature Reviews article verifies SLR acceleration, i.e. the 2nd derivative of SLR with time is positive, not that it’s increasing! Like I told y’all, it’s been 50 years!
“2nd derivative of sea level, not SLR, with time is positive”. F*** me, I keep shooting myself in the frackus!
Hi Ken,
Coral atolls exist because of living corals turning dissolved calcium and carbonate into hard material that builds up as reefs and as sand and fragments. For a atoll to stay above rising seas, as they would need to for quite a long time in the future, what storms wash away has to be replenished by whatever the corals themselves are able to keep creating as solid minerals. To do that, the that need to stay alive.
The shallow-water reef building corals in tropics around the world live near the upper boundary of their heat tolerance, and depend on algal symbionts for part of their food. And they depend on clear water to give the algae the sunlight, and they depend on being able to maintain and build shells that are made of material that gets more difficult to hold together as ocean pH declines.
The first known global bleaching event was in 1998 and there have since been lots. Tropical oceanic heatwaves are becoming more frequent. In the meantime, the imbalance of CO2 in air vs. ocean has been pressing more CO2 into the ocean, and that turns down the pH further.
Rather than me keep blathering, here’s an excellent discussion of the risks that corals worldwide face, from an expert whose been at her job for decades.
It’s worth a look and it’s worth putting in a plug for this series – the “Cleaning Up” podcast, that presents excellent, in-depth interviews, mostly related to energy, but also to impacts and nature, like today’s episode:
Are Coral Reefs More Resilient Than We Thought? | Ep225: Dr Katharina Fabricius
I highly recommend the podcast, and as a spoiler alert, “more resilient” means the survivors, depending on how far we perturb things, will be the types of corals like brain coral that are tough, but also don’t provide most of the habitat niches that make reefs so valuable as complex ecosystems. Dr. Fabricius mentioned a lot of damages we’re creating besides warmer, less-alkaline waters.
The Voortman paper says this:
This is an aspect of sea-level analysis that has been under-researched IMO. First off, it’s clear that Voortman aren’t experts at tides, otherwise they would realize the 4.42 yr perigean cycle is the important tidal factor, i.e 1/2 of 8.85. Nevertheless, a tidal-induced variability is likely a key mechanism, along with connections to ocean indices such as NAO (correlated especially with the Baltic and other Atlantic regions) and ENSO (correlated with Pacific regions). A unification is possible if a common-mode mechanism of tidal forcing impacts BOTH the sea-level sites and ocean indices.
Raising the awareness of this Voortman paper is timely, since I’ve recently been compiling a comprehensive set of cross-validated tidal model fits of well over 100 of the PSMSL mean sea level sites, predominantly those with over 100 years of data, but also those with at least 75 years. These results are collected along with 20 climate indices.
https://geoenergymath.com/2025/09/12/simpler-models-alternate-interval/
I will write more on this, but since this is my first read of the Voortman paper, I will just note that some of the PSMSL sites that Voortman single out, such as Ko Lac, Grand Isle, several Japanese stations, have also been problematic in showing a poorer cross-validation from my results. The active seismic background in Japan may be a factor, as they mention. So, if the stationarity requirement of a long-term tidal analysis, i.e no subduction shifts, is necessary then perhaps these sites can be treated specially. Otherwise, the analysis is completely automated and hands-off. The repository is here: https://climate.pukite.com
With that said, I do agree that the (lack of) independence of all these sites needs to be taken into account. So even though I have promising CV results, at least some of the agreement is less statistically significant because so many of the sites are geospatially co-located, such as along the Baltic.
BTW, just to be clear, I am not looking at the acceleration or trends at these sites for now, just the natural, seemingly erratic, cycles that have mystified researchers for years. Yet, if these are modeled adequately, they will provide a great benefit in helping to further discriminate and isolate the secular trends due to climate change, isostatic glacial rebound, etc.
Paul Pukite; ” This is an aspect of sea-level analysis that has been under-researched IMO.”
Could you be any more self-centered, Paul? You SEE a cynical manipulation of the data to support the Trump’s agenda by the DOE denier group, who to proclaim the lack of global SLR:
1. ignored the right tool for assessing it – the massive satellite dataset, IN FAVOUR of tidal gauges which signal is compromised by the local effects
2. and from the latter – with majority of the data points showing the significant INCREASE – they cherrypicked FOUR gauges that …support their agenda of no increase.
and you apparently think to yourself:
A-ha! That’s a perfect opportunity to …. complain how in the climate change studies – MY hobby horse – tidal oscillations – is severely “under-researched”
Even though short OSCILLATIONS around the mean (here: “the 4.42 yr perigean cycle “)- get AVERAGED OUT many times over – each time somebody calculates 30-YEAR average (a.k.a. a “climatological trend”).
As has been explained to you MANY DOZENS of times before. And still – nothing?
Piotr, That’s considered bullying. You can read about it in this week’s feature article in Nature
‘Lipstick on a pig’: how to fight back against a peer-review bully
Anyone reading what I have written in the above thread should understand that this is all new analysis work from yours truly. As of a month ago, there were just a couple of sites analyzed. Since that time I’ve added over 100 from the PSMSL database and have over 50 more that are shorter time range, but still significant that I haven’t posted yet, https://climate.pukite.com
Until the https://climate.us forum gets up and running, further discussions at https://github.com/orgs/azimuth-project/discussions/ are welcome.
Paul Pukite: Piotr, That’s considered bullying.
What – pointing that you AGAIN try to hijack the discussion directing it on your hobby horse, and have ignored the criticism of the same behaviour in the past??? If you can’t stand the heat, don’t start the fires.
Paul Pukite: Anyone reading what I have written in the above thread should understand that this is all new analysis work from yours truly.
What are you talking about? NOBODY was discussing whether your analysis work was “new” or not “new”. I have challenged the RELEVANCE of your post to the subject of this discussion. Here it is again, for your reference:
========================
Piotr 20 Sep: ” You SEE a cynical manipulation of the data to support the Trump’s agenda by the DOE denier group, who to proclaim the lack of global SLR:
1. ignored the right tool for assessing it – the massive satellite dataset, IN FAVOUR of tidal gauges which signal is compromised by the local effects
2. and from the latter – with majority of the data points showing the significant INCREASE – they cherrypicked FOUR gauges that …support their agenda of no increase.
and you apparently think to yourself: A-ha! That’s a perfect opportunity to …. complain – how in the climate change studies – MY hobby horse (tidal oscillations) is severely “under-researched”
Even though, your short OSCILLATIONS around the mean (here: “the 4.42 yr perigean cycle “)- get AVERAGED OUT many times over – each time we calculate 30-YEAR average (a.k.a. a “climatological trend”).
As has been explained to you MANY DOZENS of times before. And still – nothing?
======================
Which part of the above text, you had …. understood as …. me discussing whether your tidal “analysis work” is “new” or not?
Note to everyone — this is not how to do science. You don’t automatically attack the messenger. Everything that I have discussed on this forum, at my blog, at other climate science forums, in papers and books, and reported at conferences stands on it’s own. You can objectively look at the results, perhaps first take a 30,000 foot view, and consider that what I am trying to get across is a commonality to all the findings. It’s simple at it’s core — that a tidal force plays a key role in synchronizing natural climate cycles (sea level included), even though they appear to be highly erratic. But you may ask, why would I have anything new to offer since this has all been studied to death? Well, there are plenty of signal processing approaches that have never been applied to the data — it shouldn’t be all that surprising because climate science is not the only science out there, contrary to the frantic gate-keeping that Piotr supplies on a regular basis.
This RC post is specifically about the applicability of using tidal gauges to estimate sea-level trends and assigning causes to long-term variability, climate change being one. There is a valid reason to look at tidal gauges, mainly because satellite records don’t go as far back as tidal gauges do, and data covering long time-spans are particularly important in helping to resolve the influences of long-period tidal cycles. Shorter intervals such as those going back only 50 years will suffer from overfitting.
A paper that I found recently (thanks to this RC blog post) may help show how the unification of tidal forces is manifested in the observations
I have published that the Chandler wobble is directly linked to a lunar tidal cycle nonlinearly interacting with a semi-annual cycle. (NOTE: This is NOT the consensus of geophysicists despite it’s intuitive plausibility via gravitationally torques) And so the transitive unification here is that the Stockholm sea-level long-term variability is also manifested as a tidal cycle, and further that other harmonics are isolated as shown in the following figure — each spectral peak identified as D is lunisolar:
https://imagizer.imageshack.com/img924/7354/WKsiBC.png
For Stockholm, one can therefore cross-validate SLH models against the historical data
https://pukpr.github.io/results/pt6_8_quad/78site-0.6-0.8.png
https://pukpr.github.io/results/pt3_6/78site-0.3-0.6.png
I have found around 200 PSMSL sites of duration of > 75 years that collectively show statistical significance via training/test cross-validation analysis. This is not that difficult to do as each model takes only a second to train.
Again, no need to attack me, as I am only the messenger — the data is the data and these matching patterns will remain for someone else to replicate.
Paul Pukite: Note to everyone — this is not how to do science.
Note to Paul Pukite – you are NOT doing science here. What you did here is to try to HIJACK an important discussion. Gavin’s opening article is about DOE deniers trying to misrepresent the climate science to support their ideological/political goals of questioning the reality of the climate change, and therefore questioning the urgency of its mitigation. Challenging the climate change denial has big societal implications and is one of the central reasons form.
Your contribution to this discussion is to DIVERT the discussion away from its topic (DOE denial) and toward the UNRELATED to AGW tangent, which happens to be your hobby-horse:
:
Paul Pukite: ” [tidal oscillations around the mean] is an aspect of sea-level analysis that has been under-researched IMO.”
And you KNOW that it is a tangent, because it has been explained to you DOZENS of times already e.g.:
Piotr Sep 20 and Piotr Sep 21: “short OSCILLATIONSAROUND THE MEAN (here: “the 4.42 yr perigean cycle “)- get AVERAGED OUT many times over – each time we calculate 30-YEAR average (a.k.a. a “climatological trend”).
You have been incapable of refuting this falsifiable argument each of the dozens time I have
made it, and instead you …. play a wronged victim: ( “Piotr, That’s considered bullying. “) and lecture the readers that the white is black – that challenging other people’s claims with FALSIFIABLE arguments – “ is NOT how to do science“. (c) Paul Pukite.
And your trying to redirect the discussion away from AGW and toward non-AGW issues – is noting new – you have advocated redirecting research effort from studying AGW and its drivers, and toward your area of interest – short-term oscillations. And claimed doing so could save “countless lives”.
You are what you write. Paul Pukite – everyone!
Piotr said:
Sure, I’d be in favor of using satellite readings if they went back more than 100 years. As it is I use the historical PSMSL database extract the amplitude and phase of the long-period tidal cycles.
Paul: Note to everyone — this is not how to do science. You don’t automatically attack the messenger. Everything that I have discussed on this forum, at my blog, at other climate science forums, in papers and books, and reported at conferences stands on it’s own.
BPL: Agreed, one shouldn’t attack the messenger. The message, however, has to be both new and useful. That’s why God made peer review.
check
Alas, passing peer-review does not guarantee that the idea becomes consensus. There are plenty of conflicting peer-viewed models in physics.
This one is essentially pitting the obvious tidally forced mechanism (my approach) VERSUS a grab-bag consensus model that attributes interannual variation to several mechanisms, see https://tidesandcurrents.noaa.gov/sltrends/sltrends_station.shtml?plot=intannvar&id=050-141
Looking at Tamino’s graphic, and the linked blog post, it is fairly obvious (to me) that the west/east coast differences are due to tectonics. I couldn’t immediately find a map of vertical movement of the North American plate, but the east coast is extensional whilst the west is transverse with a compressional component.
There is a chance that these movements are changing and thus causing acceleration, but in my opinion it is more likely that we can measure the acceleration better in areas where the absolute sea level rise is larger than the confidence interval
KW: Looking at Tamino’s graphic, and the linked blog post, it is fairly obvious (to me) that the west/east coast differences are due to tectonics.
BPL: Was tectonics represented at all in the graphic?
In regard to determining sea-level shifts, the first analysis should be in a comprehensive understanding of the natural SLH variation. To take an example, consider locations in the Baltic Sea and then northerly into the Gulf of Bothnia separating Norway and Finland. Begin by detrending the data and fitting the erratic cycles to tidal periods, concurrently cross-validating the results in the dashed test interval — the graphs shown below demonstrate high significance across the sets and over the interval.
https://imagizer.imageshack.com/img922/1006/4lYWVe.png
Yet, look at the long-term trends — the northernmost spot Furuogrund shows a decreasing trend, while the southernmost spot Aarhus in Denmark is trending up. This is commonly understood to be due to glacial rebound, with the effect intuitively being historically stronger the more north (i.e. colder) the measurement siting.
To fully discriminate the climate change acceleration from the glacial rebound deceleration is not the easiest challenge in the world, but being able to precisely isolate the natural tidal cycles will obviously help. To make it even more challenging is that the tidal cycles can show periods in the multidecadal range.
As far as I can tell, no one is doing the long-period tidal analysis correctly, if at all, even though the results shown above demonstrate predictive capability. The challenge to anyone out there is to duplicate the results. Fortunately, it doesn’t take a lot of computing power.
BPT: Yes- the continental margins are where tectonics puts them ,and the coastlines onshore of them define the tides,
That’s entirely true for continental margins, Russell, independent of the volume of ocean water. As you surely know, coastlines, which do partially define the tides by the volume of ocean water, are also subject to local tectonic flexure, as well as orthostatic depression by glacial ice and rebound upon deglaciation, erosion and sedimentation rates subject to engineering, subsidence due to groundwater withdrawal, etc.
Tamino’s posts, however, deal with tide gauge measurements, and he professes puzzlement at the difference between the US east and west coasts (https://tamino.wordpress.com/2025/08/11/sea-level-rise-in-the-u-s-a/):
As you can see, all the [east-coast] acceleration estimates are positive and all but one “statistically significant.” They are also all above the global level with quite a few significantly so.
The story is very different for west-coast stations. Most show slower-than-global sea level rise, and one even sees sea level fall…
This drastic difference between the coasts has been known for a while, but I don’t know the reasons. I expect that ocean circulation patterns and their changes are primarily responsible.
Huh. Is Tamino not well acquainted with plate tectonics? The Oregon coast, for example, is known to be elevating or sinking in various places, evidently due to compressive forces from the subduction zone offshore (https://osupress.oregonstate.edu/book/oregon-geology).
In any case, eustatic + steric sea level rise, as tracked by satellites, airborne missions, and shipboard measurements, must AFAICT be solely attributed to melting land ice and thermal expansion of seawater respectively, both due entirely to rising GMST. That is, I for one am skeptical global SLR is substantially due to recently outgassed volcanic water, infalling cometary ice, or tectonically driven changes in the capacity of the ocean basins!
Right- in the light of what Tamino wrote I should have simply pointed out that the West Coast accretional terranes are being nudged uphill a while the east coast is largely out of seismic ranges of the active midatlantic ridge.
The Pacific Northwest is for structural geologists to explain
in Re to Mal Adapted, 19 Sep 2025 at 7:49 PM,
https://www.realclimate.org/index.php/archives/2025/09/time-and-tide-gauges-wait-for-no-voortman/#comment-839519
Dear Mal,
I apologize for the following remark that is tangential to your primary topic (correct measurement of the global sea level), however, I would like to make you aware of an inaccuracy in your post that might be potentially confusing for less skilled readers.
A recent discussion between zebra and MA Rodger arrived at a conclusion that in the light of two studies cited by MA on 21 Aug 2025 at 2:29 PM,
https://www.realclimate.org/index.php/archives/2025/08/unforced-variations-aug-2025/comment-page-2/#comment-838092
global sea level rise can be interpreted rather as a consequence of Earth energy imbalance (EEI) than as a consequence of rising GMST, because it appears that EEI (and a continuing sea level rise) can persist long after the GMST rise stops.
The respective thread started on 21 Aug 2025 at 1:37 AM,
https://www.realclimate.org/index.php/archives/2025/08/unforced-variations-aug-2025/comment-page-2/#comment-838059 ,
continued this month, starting on 2 Sep 2025 at 6:43 AM,
https://www.realclimate.org/index.php/archives/2025/09/unforced-variations-sep-2025/#comment-838723
and concluded by detailed explanations provided by MA Rodger on 8 Sep 2025 at 11:43 AM,
https://www.realclimate.org/index.php/archives/2025/09/unforced-variations-sep-2025/#comment-839043
and on 11 Sep 2025 at 9:12 AM,
https://www.realclimate.org/index.php/archives/2025/09/unforced-variations-sep-2025/#comment-839174 .
Best regards
Tomáš
Trying to ingratiate himself with zebra, Tomas Kalisz lectures Mal:
Tomas Kalisz 20 Sep: “ Dear Mal, I would like to make you aware of an inaccuracy in your post: global sea level rise can be interpreted rather as a consequence of Earth energy imbalance (EEI) than as a consequence of rising GMST, because it appears that EEI (and a continuing sea level rise) can persist long after the GMST rise stops.”
1. Mal referred to current SLR – hence the future hypotheticals (no more GMST rise) – is irrelevant to his argument
2. Even if Mal talked about the future – of the two main mechanisms of climate-caused global SLR:
– thermal expansion is caused by increasing water T. What mechanism do you propose to continue heating the ocean waters without increasing air T?
– melting of glaciers DOES NOT require increasing T, it merely requires T to be
above the melting point of ice (0C). Hence contrary to your, attributed to Zebra beliefs,
ice will continue melting “long after the GMST [stopped rising]“.
So either your source of knowledge (zebra) is fundamentally wrong and you have been unable to spot it, or you are not as “skilled reader” as you fancy yourself and completely misunderstood what zebra said.
In either case: you lecturing Mal on him “being incorrect” is based on your own ignorance.
Thanks for your support, Piotr, but I’ll magnanimously concede I could have written more clearly ;^). Hell, that’s pretty much always true. For one thing, I tend to assume readers understand that global warming is a problem of rates over time. After all, this blog exists because previously slow geophysical processes are accelerating WRT their pre-industrial baselines. It’s the time dimension that gives ‘us’, or me at least, cause for alarm: an attestation of my organic nature, if not intelligence, BTW. Yep, it’s me, Mal! Nonetheless, to be more explicit, if not more concise (something generative AI is better than me at):
“Rising GMST” refers to d(GMST)/d(t). Observed by surface thermometer and satellite. Probably accelerating upward from pre-industrial baseline.
“Sea level rise” refers to d(sea level)/d(t). Tracked by satellite, airborne, ship, and buoy observation, taking tides into account. Data still insufficient, but predicted to be accelerating upward from baseline.
“Melting land ice” refers to d(land ice mass)/d(t). Tracked by various methods. Demonstrated to be accelerating downward from baseline.
“Eustatic+steric sea level rise” refers to (d(water mass))+d(water density))/d(t). The only realistic causes of global SLR on the relevant time scale.
All 1st derivatives of time, but with ominous 2nd derivatives. Accelerating GMST rise is plenty alarming to me! Relevant to sea level rise, as well:
“Melting land ice”, again as measured by various methods, is the only significant source of additional water mass, but I should have said “accelerated melting of land ice” (2nd time derivative of mass). Other potential sources are volcanic outgassing and infalling comets, but neither shows a d(m)/d(t) from pre-industrial values. And how can glaciers not be melting faster as surface temperatures rise (the few exceptions due to increased snowfall dismissed as quantitatively minor red herrings)?
“Thermal expansion of seawater” should be “Accelerated thermal expansion of seawater” (2nd time derivative of temperature-dependent density) as observed by shipborne sounding and Argo, since deep ocean waters are known by sedimentary species turnover to have been warming since the end of the Pleistocene, but more slowly. The only plausible cause of acceleration above pre-industrial is the rising trend of global heat content due to anthropogenically enhanced “greenhouse” (an awkward analogy) forcing. Other causes of thermal density change over time are solar activity and volcanic plus geothermal heat flux, of 2nd or 3rd order compared to rising GHC, and again not changing in the relevant timeframe. And where the hell else is the net downward heat flux going to go?
How’s that? Painfully verbose, I’m afraid. If it’s still not clear, I’ll let somebody else try, as I’m at the limit of my skill, and patience.
Mal Adapted: (d(water mass))+d(water density))/d(t)
Extraneous ‘)’ following ‘d(water mass)’. Dang, egregiously unclear. A thousand pardons.
in Re to Piotr, 20 Sep 2025 at 7:06 PM,
https://www.realclimate.org/index.php/archives/2025/09/time-and-tide-gauges-wait-for-no-voortman/#comment-839556
Hallo Piotr,
Have you read the conversation that I have referred to?
I am asking because MA Rodger explained quite clearly that it is not the surface temperature rise what primarily heats the ocean (and thus increases its volume).
Quite oppositely, the studies cited by him seem to show that sea level rise will continue centuries after global warming (in terms of global mean surface temperature rise) reaches its maximum, namely until the positive Earth energy imbalance (EEI) will decrease to zero.
The reason for this (for me surprising) conclusion is the mechanism of the ocean heating which seems to be different from your assumption. It appears that the ocean warms primarily by direct absorption of shortwave solar radiation, and the studies suggest that as soon as the EEI rise stops, the absorbed heat will be rather transported to deeper ocean layers than to the land and the atmosphere.
I have no idea if these conclusions already form part of the scientific consensus about climate change. Perhaps not yet. Anyway, if you would like to dispute them, you should have to approach rather MA Rodger who actually presented them in the respective thread.
Greetings
Tomáš
BPL,
Not 100% sure what you are saying. Are you saying Tamino hasn’t included an isostatic rebound model? When I mentioned tectonics I was talking about the ongoing massive forces of continental drift, not the melting of a thin layer of ice thousands of years ago
KW,
S0rry if I misinterpreted you. A common denier meme is that any increase in sea level is due to islands/continental margins/etc. sinking, producing a spurious sea level rise. I just wondered if anyone had collected the data globally, and if there was some time series for continental-margin rise or fall.
The link for Le Bars et al (2023) also just returns this RealClimate post.
[Response: It’s supposed to link to the full reference at the bottom, and then you can click on the doi to get to the paper. I think it’s correct? – gavin]
Again. Judith Curry was withdrawn as a witness by the defense in Held v. Montana because she would have been under oath and demolished on cross examination and rebuttal. The state court judge went on to uphold Montana’s Constitutional Right to a Clean and Healthful Environment. Affirmed by Montana’s Supreme Court. Defense motions-to-dismiss a federal court case by young plaintiffs objecting to 3 Trump executive orders favoring fossil fuel was just heard–decision pending. Defense doing all it can to prevent Curry and others from testimony under oath.
Keith Woollard: “ Looking at Tamino’s graphic, and the linked blog post, it is fairly obvious (to me) that the west/east coast differences are due to tectonics.”
THAT’S what you want us to discuss upon seeing the staggering intellectual dishonesty of your ideological allies – deniers from DOE?
The figure posted by Gavin WASN”T an invitation to discuss … the technical reasons for the difference between the west and east coast tidal gauges – it was to illustrate scientific standards and ethical Integrity of the deniers – who, to proclaim on the lack of global SLR:
1. ignored the right tool for assessing it – the massive satellite dataset, and IN FAVOUR of tidal gauges which signal is compromised by the local effects
2. and from the latter – they cherrypicked FOUR gauges, every one of them supporting their pro-Trump agenda – while ignoring ALL the other datapoints that contradicted their agenda – the read point in the graphs.
And YOU, upon seeing that brazen MANIPULATION, want people to discuss …. your opinion on the reason for regional differences in tidal gauges readings in between the west and east coast of the US????
You, and your fellow denier distractor, Ken Towe, are like people who seeing an arsonist setting a house on fire – are trying distract the neighbours from stopping the arsonists by re-directing their attention onto the
reason WHY the wet left wall of the house is not on fire yet,
Sorry Piotr, my intent was not to derail the conversation. Gavin presented a graphic and a link to the related discussions. Tamino struggled to explain what seemed obvious to me. I was showing why acceleration isn’t statistically significant on the west coast. Not everything is “us and them”
Keith Woollard: Gavin presented a graphic and a link to the related discussions. Tamino struggled to explain what seemed obvious to me .
Which does not change the fact that it is a minor point, present not in Gavin’s text, but only in one of its references – and as such – is a trivial TANGENT to the essential SUBJECT of Gavin’s article, which was the brazen manipulation by the deniers who, to proclaim on the lack of global SLR:
1. ignored the right tool for assessing it – the massive satellite dataset, and IN FAVOUR of tidal gauges which signal is compromised by the local effects
2. and from the latter – they cherrypicked FOUR gauges, every one of them supporting their pro-Trump agenda – while ignoring ALL the other datapoints that contradicted their agenda”
Whether the result – detracting from Gavin’s subject onto a trivial, minor digression in one of his references – stems from a deliberate action, or is a result of poor intellectual discipline ^* – does not make a big difference.
Just like in the case of Trump – whether he goes on a tangent to avoid issues he does not want discussed, or because he just can’t help himself – doesn’t really matter – by their fruits, not their declared intentions, you shall know them.
==
^* “Tangentiality – a thought disorder where a person’s train of thought wanders and deviates from the original topic, providing irrelevant or excessive detail without ever returning to the essential point of the conversation.
Wow, just wow!
I wonder if you could be any more condescending?
Perhaps if you could explain to Gavin which of his graphics are important and which are trivial, it might make it easier for people to work out which of the one presented is worth discussing.
And the need to explain the concept of a tangent when I suspect the majority of contributors here have at least some university mathematics!
Keith Woollard: Wow, just wow! I wonder if you could be any more condescending? Perhaps if you could explain to Gavin which of his graphics are important and which are trivial,
The difference between us is that I have based my calling you out on falsifiable arguments above – your response is based either on your inability to read or on your deliberate distortion of what I have said, namely
– I identified “ the essential SUBJECT of Gavin’s article – the brazen manipulation by the deniers to proclaim on the lack of global SLR”
and in this context called your contribution (finding in one of the Gavin’s links one sentence by Tamino – a sentence that is irrelevant to Gavin’s subject. Irrelevant, because Gavin’s graph proves cherry-picking of data by the deniers regardless whether Tamino knows why the tidal gauges signal is different between the West and East coast, or not.
As such – YOUR entire “contribution” to Gavin’s subject is at best trivial, at worst, an attempt to distract from the Gavin’s message – from his proof of scientific dishonesty of the deniers from DOE/their sources.
When I called out on that, you portray my criticism of YOU as my …. staggering arrogance (“ Wow, just wow! I wonder if you could be any more condescending?” – the arrogance so great that I am not above condescension toward one of the best climate scientists in the world:
Keith Woollard “ Perhaps […] explain to Gavin which of his graphics are important and which are trivial=
Anybody who has been convinced by Keith W. that the target of my condescension WAS Gavin Schmidt – should consider Keith Woollard an honorable, principled and truthful man. By their fruits you shall know them.
I was just looking at the NOAA Tides and Currents “Sea Level Trends” pages, and they have the following slender banner up – another rapid shift in a system.
Anyone who makes use of the NOAA sea-level and tide information might want to read this.
New site goes live in less than two weeks, current site planned removal by next April.
The main Tides and Currents page also has a banner, saying
They include a non-working link at what I bolded above:
https://dev.tidesandcurrents.noaa.gov/high-tide-flooding/annual-outlook.html
The “dev.” at the start of the URL indicates to my software industry thinking “development” rather than “production”, but regardless, it doesn’t work (as I type this).
Here’s the live version of the Annual High Tide Flooding Outlook page:
https://tidesandcurrents.noaa.gov/high-tide-flooding/annual-outlook.html
I’m trying not to read anything into the system change or the broken link – IT maintenance needs downtime and it’s Sunday night in the US while I’m typing.
Just flagging a change in our federal scientific data systems.
Keith Woollard said:
A behavior can be accelerating in the opposite direction to which it is trending. That’s just math, as acceleration is first derivative of a rate. So if a rate such as sea-level change is negative and a subsequent rate is less negative, then the sea-level is accelerating in the positive direction.
So, I don’t think you actually showed why acceleration is not statistically significant, since I don’t see you doing any math.
Yes Paul, totally agree. In this case I am not talking about any true mathematical definitions, rather how Tamino appears to have defined statistical significance. They seem to have defined it as “if the expected values encompassed by the CI are all on the same side of the axis, then it is statistically significant. Thus for low values for both the rate and the derivative, it is much harder to reach statistical significance.
https://www.americanthinker.com/blog/2025/09/latest_science_further_exposes_lies_about_rising_seas.html
https://www.americanthinker.com/blog/2025/09/media_s_psyop_against_climate_scientists.html
https://andymaypetrophysicist.com/2024/08/04/is-sea-level-rise-accelerating/
“American Thinker”? “Petrophysicist”? Science Denier, Obviously posts obvious science denial.
Consider the source, and follow the money.
Obvious indeed. Proud of denying science; never mind that it brings them the quality of life they enjoy and the computer on which they posted. Also eager to discredit those who make it possible for them to post here. Some correctives to the insult laden claim that using one’s intelligence, sense, and senses is a “religion” while lies and insults are true. Reality has one undeniable quality: it is real.
https://www.climate.gov/news-features/understanding-climate/climate-change-global-temperature
https://www.youtube.com/watch?v=LwRTw_7NNJs
https://yaleclimateconnections.org/2024/06/the-u-s-is-nowhere-near-ready-for-climate-change/
https://yaleclimateconnections.org/2024/08/when-will-climate-change-turn-life-in-the-u-s-upside-down/ [and the other items in that series; plenty of data about loss of life, liberty, and money there too]
– A new entity arrived, using handle: “Science Denier, Obviously”
– Susan: “ Proud of denying science
Susan, if the handle “Science Denier” – then yes – it signals the pride from being one (If as a person without scientific background I can hold my own again scientists then I must be very stable genius, just as our Glorious Leader, President Donald J. Trump!“)
But adding “Obviously” changes the things – now the main goal of this handle is to PREEMPT the criticism along the lines: See? I already KNEW in advance your response, and therefore your criticism of me and links I promote is invalid, thus calling me and my links “denialist” is “unfair and immoral” [(c) Mo Yunus]
Imagine also giving links to the KKK and Aryan Nation materials, under the name: “Racist, Obviously”.
Piotr says
24 Sep 2025 at 5:05 PM
See? I already KNEW in advance your response, and therefore your criticism of me and links I promote is invalid, thus calling me and my links “denialist” is “unfair and immoral” [(c) Mo Yunus]
Incorrect. Misrepresented. My real actual comments are being misused here. Another an unfair and immoral tactic.
see Mo Yunus says
19 Sep 2025 at 9:22 PM
Constantly lumping all criticism into the category of “denialism” is an unfair and immoral tactic. It closes off important conversations and pushes away people who might otherwise be allies.
It replaces reasoned debate with a punitive, “us vs. them” mentality, and in doing so, becomes as toxic and unhelpful as the rhetoric it claims to oppose.
To me, this is a moral dilemma. A group defending a scientifically sound position can start to adopt the same rigid, unforgiving tactics as the very people they’re fighting against.
A comparison to the Stanford prison experiment makes perfect sense here; an adversarial dynamic can corrupt even people with good intentions, leading to behavior that is dehumanizing and cruel.
This “us vs. them” mentality has a number of negative effects on any online forum: It silences good-faith discussion. It erodes trust in the moderators and the site’s purpose.
It leads to a decline in quality of content. The focus shifts from explaining complex topics to winning arguments.
in full
https://www.realclimate.org/index.php/archives/2025/09/unforced-variations-sep-2025/#comment-839523
and addendum
https://www.realclimate.org/index.php/archives/2025/09/unforced-variations-sep-2025/#comment-839751
Mo Hummus: Constantly lumping all criticism into the category of “denialism” is an unfair and immoral tactic
So is piously dismissing denialists’ ulterior, if not subjectively immoral, motives, sometimes disguised. It ignores the principal reason the US still doesn’t have a decarbonization policy, 37 years after James Hansen’s announcement. AFAICT from having lived that interval as a nominal adult, the dogged official denial of anthropogenic climate change by our government, including it’s present retreat from previous congressional and judicial recognition however ineffectual, is undeniably, ultimately due to the long, documented disinformation campaign by fossil fuel producers and investors, to forestall collective intervention in their profit streams. FWIW, I’m hardly alone in that conclusion (https://www.newyorker.com/news/daily-comment/kochland-examines-how-the-koch-brothers-made-their-fortune-and-the-influence-it-bought).
In any case, not all criticism on RC is lumped in the denialism category. It’s just that there haven’t been any new substantive challenges to the climate-science consensus for years! By now, RC regulars have seen all the faces political and/or professional disinformers wear. For newcomers to our depressing climate reality, here’s a recent peer-reviewed article in a European Commission journal: “Disinformation as an obstructionist strategy in climate change mitigation: a review of the scientific literature for a systemic understanding of the phenomenon” (https://open-research-europe.ec.europa.eu/articles/4-169/v2). Scientifically meta-literate readers will note the article’s place in J. Nielsen-Gammon’s hierarchy of credibility (https://web.archive.org/web/20130213192911/http://blog.chron.com/climateabyss/2013/02/scientific-meta-literacy; does anybody have a current link to his original post?).
The upshot: determined denialists will adopt whatever rhetorical style they think will fend off decarbonization the longest, with unapologetic hypocrisy! As for you, Mo X, you may or may not be one of them. but you are a gratuitous tone troll (https://rationalwiki.org/wiki/Tone_argument). If our blunt “peer review” (heh) truly offends you, have you considered filing a butt-hurt complaint (https://www.dochub.com/fillable-form/4630-butt-hurt-report)?
Correction: it[]s present retreat. “The crux of the biscuit, is the apostrophe” (F. Zappa).
The internet entity formerly known as “Mo Yunus” :
“ Incorrect. Misrepresented. My real actual comments are being misused here. Another an unfair and immoral tactic: see Mo Yunus 19 Sep: Constantly lumping all criticism into the category of “denialism” is an unfair and immoral tactic.”
Let’s see: your original post (19 Sep )
– did not reply to any specific post,
– did not quote or even refer to any specific discussion in which somebody was called “denialist”
– did make a sweeping generalized claim (“Constantly”)
As such – it is a GENERALIZATION Strawman. Why it is a strawman see Atomsk 26 Sep 2025 at 6:54 AM :
https://www.realclimate.org/index.php/archives/2025/09/but-you-said-the-ice-was-going-to-disappear-in-10-years/#comment-839875
As a strawman – it is dishonest – it tries to discredit the opponent by ascribing to them the “unfairness and immorality” of your strawman.
As an unsupported GENERALIZATION – can be used to turn the table on the critics – ANYONE whose arguments were called out as “denialist” – can now accusing their critics of “unfair and immoral tactic“.
Heck, our Yunus Hummus have just used (23 Sep 25 at 8:51 PM) his unfair and immoral” quote in response to Mal arguing that Thomas Fuller is …. NOT a denialist !
Mal Adapted: 23 Sep 25 2:47 PM “that make me think Tom [Fuller] is simply a gleeful reflexive contrarian: he’s here to ‘pick’ holes, and BTW to ‘pick’ fights”
“Unfair and immoral” if you do, “unfair and immoral” if you don’t, eh?
Climate Science from Climate Scientists: [and from Unforced Vs} “As usual try to remain substantive and avoid insults and personal attacks on other commenters. Any sock-puppetry or abusive comments will just be deleted on sight. Also, please don’t outsource your comments to ChatGPT – cut-and-pastes of long-winded LLM output are tedious and add precisely nothing to the conversation. There are real things happening in climate – please focus on them.”
Piotr: A good rule of thumb: write for the possible lurker who came here for real information, having heeded the banner which describes RealClimate. I am not remotely interested in the people whose personal attacks and/or outlandish assertions all too often kidnap this comment section.
Excessive hostilities are a distraction.
I published a paper on Brest and Marseille tide gauges trends and accelerations estimates from the exploration of all possible time spans : https://comptes-rendus.academie-sciences.fr/geoscience/articles/10.5802/crgeos.302/
which supports the acceleration result on these two french tide gauges.
Good research on tidal gauge data. I appreciate the work done on filling the gaps in the time-series data, especially for the Brest station, which has a ~12 year gap between the 1940’s and 1950’s. Using my technique for modeling long-period tides, I can show excellent cross-validation using training up to 1930 and after 1970, and thus filling in everything in between with interpolated values.
https://imagizer.imageshack.com/img923/1508/U7AZ6z.png
In the chart above, the gap in missing values is shown as a straight line. I don’t show the interpolated missing values, simply because of the plotting algorithm being used, but these can be checked by using data from nearby sites, as your paper describes. Yet, if the already good cross-validation of the other test values – in the 1930’s and 1960’s validation interval (dashed interval) shown in the chart – – is any indication, the missing values will likely also show a good correlation when filled in. That would provide a completely unbiased validation of the model as the unseen data is completely out-of-band.
Regarding the paper by Jonathan Chenal, the other station (in addition to Brest in France) evaluated for missing data is at Marseille. I have evaluated most of the stations available at the PSMSL site as a tidal forcing model so thought to add that as well. This data is on the shorter side and is very choppy, but also can be cross-validated in a test interval
https://imagizer.imageshack.com/img924/2304/nscpSQ.png
All the missing data can be filed in, i.e. interpolated, via this model, even though it is not shown above. The model is generic, only dependent on known tidal periods, and seems to work in most coastal regions around the world, perhaps save for a few of the seismically active locations such as in Japan. Some of these are obvious as they show more abrupt shifts in sea level, which makes it more difficult to train on.
Since tectonics and even the Gulf of Bothnia have come up in this sea level discussion, I’ll pass along these two useful (to me, at least) videos from geologist Rob Butler’s “The Shear Zone” YouTube page. First one deals with the tropics, so no bouncing from ice appearing and disappearing locally, the second deals with what’s happening in a place where the ice had been recently. You can finish both in less than 25 minutes. And to those who’ve been trying to say sea level has been rising for thousands of years, in the first video he places the high-point of sea level in the pre-industrial Holocene at 5,000 years before present, with slow decline since. Well, until fossil carbon became popular as fuel.
Holocene sea levels: Ring of Fire – tectonic journeys in E Asia
– https://www.youtube.com/watch?v=G87CRgpHnP4
“Thailand’s dramatic coast line contains high-resolution records of past sea-level change – information that has been used to understand global signals. Explore the extent to which these records can be read – in terms of climate change, local and regional tectonics”
Nordic rebound – GIA and mantle viscosity
– https://www.youtube.com/watch?v=-Fkq_4RWSWI
“Follow Rob to northern Finland to find out how the active uplift of the region gives fundamental information on the Earth’s mantle.”
US Government is shut down so this will have to do from state-side.
Image Gallery => https://pukpr.github.io/results/lte_1950_1970/image_results.html
Even trying to model sea-level changes way up the St. Lawrence Seaway
https://Climate.US is promising to do:
but wait “A generous supporter has stepped forward with a $10,000 match challenge. Donate right now and every gift to Climate.us will be doubled, dollar for dollar, up to a maximum of $10,000!”
The infamous match challenge.
So why can’t someone just do the research? It doesn’t require that much besides curiosity.