For years, the Intergovernmental Panel on Climate Change, or IPCC, has claimed that human-caused climate change has accelerated sea level rise.
But that claim is false. There is no scientific evidence of accelerated sea level rise since the mid-19th Century, and thus none showing human-created emissions caused an acceleration in recent decades.
This does not mean that climate change isn’t happening. It is. It simply means that it has not caused the sea level to rise at a rate any higher than one would expect without human-caused climate change.
Not only that, but the top scientists know this fact and have deliberately misrepresented it for years, deceiving the public.
In September, I reported on one of the first global studies of sea level rise that used tide-gauge data, which is the only real-world data that goes back long enough, to the mid-19th Century, that would allow one to detect whether sea level rise had accelerated, decelerated, or remained steady.
Since then, I exchanged over 50 emails with one of the world’s leading sea level rise scientists, Robert Kopp from Rutgers University, and heard back from IPCC, NASA, and NOAA, the National Oceanic and Atmospheric Administration.
What I learned shocked me. For years, the world’s top scientists have known that they cannot prove there has been an acceleration of sea level rise, and yet they have told the public that they can.
Not only that, in the process of this exchange, I gained a glimpse into how the scientists have been able to mislead journalists, policymakers, and the wider public for so long.
You might think this is either old news or unimportant. Some climate scientists in years past have pointed out that the real-world data do not support claims of acceleration. And in recent years, a supposed increase in natural disasters from climate change has eclipsed sea level rise in terms of attention-grabbing headlines.
But sea level rise has, since the 1990s, been the main justification for apocalyptic climate claims, and past efforts to debunk sea level rise have failed to show that scientists were deliberately misleading. The media and others have published terrifying maps of the future showing cities underwater. Accelerated sea level is one of the main justifications for predicting very high costs for adapting to climate change. And while good scientists have debunked acceleration claims in the past, they did not clearly show how IPCC scientists engaged in their manipulations.
Not only can I prove that the real-world data do not support the claims that there has been an acceleration, I can show that the scientists deliberately misrepresented their research, and how they did it, thanks to my on-the-record email conversation with Kopp of Rutgers.
How They Did It
Scientists engaged in multiple forms of manipulation. First, they introduced modeling that, depending on the assumptions, could show deceleration, linearity, or acceleration. Moreover, given that we have over 150 years of real-world data, they didn’t need to use such complicated modeling.
Second, they used alternative and indirect measures to tide gauge data of sea level rise, whose presentation they manipulated to show acceleration.
Third, they used data from periods of time that are far too short to detect a long-term trend. Sometimes scientists point to satellite data that show acceleration over the last 30 years, but that’s far too short a period of time to show a long-term trend. Proof of that is that the period from the 1920s to the 1950s, before there were significant human-caused greenhouse gas emissions, had comparable levels of acceleration
What you’ll see in my exchange with Kopp is that he points to models, alternative data, and short-term data to imply that they support his claim of acceleration. His behavior makes clear that he understands perfectly well that he does not have the scientific evidence to claim an acceleration.
And so Kopp uses irrational tactics, including non sequiturs, or statements that do not follow logically, credentialism, or appeals to his authority as a scientist who knows more, and ad hominem attacks, namely criticisms and insults, to derail our conversation and distract attention away from the central fact that there is no real-world scientific evidence to support his claim of acceleration.
The result is, I believe, more than a damning indictment of Kopp and the other sea level scientists. It is also a fascinating look into how political activists posing as scientists can use rhetoric and bullying to maintain their deception over time.
If this is the strategy Kopp has used over the years, then it helps explain why the world has been deceived for so long.
I will be the first to tell you that Kopp knows far more about this topic than I ever will.
But all of his knowledge can’t get around the fact that he does not have the scientific evidence to make his claim of acceleration.
“A fox knows many things,” the old saying goes, “but a hedgehog, which is like a porcupine, knows one big thing.”
In my exchange with Kopp, I am the hedgehog and he is the fox. He knows many, many things, but I know one big thing: the only reliable long-term real-world data is tide gauge data, and they do not show acceleration.
Between September 2 and 4, Kopp and I each sent over two dozen emails to each other. The entire exchange was on the record, and I am making the entire exchange public here. I am not redacting Kopp’s email address since he lists it on his web page. The emails are in the correct order, even though the time stamps often are not.
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In his first email, Kopp says, Voortman’s recent tide gauge study showing no acceleration “does not cite and does not appear to address the concerns raised in the 10-year-old paper Visser, H., Dangendorf, S., & Petersen, A. C. (2015)…”
But the Visser et al. study shows that different statistical approaches can yield acceleration, linearity, or even deceleration depending on model choice, sampling window, and treatment of variability.
And it’s not just Visser. The peer-reviewed scientific literature as a whole openly acknowledges that the models are assumption-dependent, even as the IPCC’s Summary for Policymakers claims “very high confidence” in acceleration.
In Kopp’s first response to me, he implies that Visser et al. and Dangendorf et al. disprove Voortman and De Vos’ study, but they don’t. As noted above, Visser shows that different statistical approaches can show acceleration, linearity, or even deceleration. Dangendorf et al. use a combination of observations and models that have the same problem.
“There are many studies that have done tide gauge level analyses,” Kopp wrote, “with different regression models, and Visser et al address the differences among them.”
I respond by asking “how the community justifies privileging one set of results over others, given Visser et al.’s own demonstration that the answer is highly method-dependent.”
Kopp then says that the journal in which Voortman published is not credible, admits he had not closely read Voortman, suggests that Wang et al. (2025) disprove Voortman, and that other data sources disprove Voortman.
In response, I acknowledge that we have other lines of evidence (altimetry, GRACE, Argo, paleo) but that they don’t contradict the tide gauge data, which is the longest instrumental record we have and it directly, rather than indirectly, measures sea level.
I did not respond to Kopp’s claim that the Journal of Marine Science and Engineering is low-quality first because it is credentialism, which is an unscientific and illegitimate appeal to authority and second because he presented no evidence to support his claim. The Journal is peer-reviewed. And even if it wasn’t, Kopp would still need to show why Voortman is wrong.
As for satellite altimetry data, it indeed shows an acceleration over the last 33 years, but that is too short to substitute for a century-plus of tide gauge data. Spatiotemporal reconstructions merge gauges with climate covariates, serial correlation structures, and regional fingerprints. Those methods are not the same as observing acceleration in the gauges themselves.
Kopp then proceeds to claim that “the data systematically — but not universally — favor acceleration, as would be expected in a world in which global mean sea level is accelerating.”
Once again, Kopp is cherry-picking and thus misrepresenting the modeling, and those outputs are based on assumptions, in contrast to the real-world tide-gauge data.
In response, Kopp points to “Wang et al 2021, 2025 and Sweet et al 2022” and claims that there is “unambiguous geological evidence for acceleration.”
But Wang et al. (2021, 2025) and Sweet et al. (2022) are not station-by-station tide-gauge audits. Rather, they are reconstructions and syntheses that show acceleration only after adjustments, infilling, and budget closure.
And there is no “unambiguous geological evidence for acceleration.” Paleo reconstructions are by definition indirect, dependent on proxies like coral terraces or salt-marsh sediments, and thus require interpretive modeling.
In response, Kopp says Wang et al., 2025 use “gauge-by-gauge linear regression model” and writes, “You seem to be stating that only models that have unreasonably simple-minded error structures (i.e., in the case of Voortman, no interannual correlations in sea level unless explained by harmonics) count as ‘not syntheses.’”
At this point, Kopp is simply repeating himself to evade the central point, which he effectively concedes, which is that the tide gauge data show no acceleration.
Kopp writes, “You seem to be saying that scientists should ignore the fact that global mean sea-level is observably accelerating…”
But, again, sea level rise is not “observably accelerating” over time horizons that would show a trend. The only scientific basis for claiming it is accelerating is through modeling. The observable tide-gauge data do not show this. To call model outputs “observable” is deliberately misleading.
Kopp then engages in ad hominem, credentialism, and projection. “Your sociological model would suggest my 2013 paper questioning the so-called mid-Atlantic US sea level acceleration hot spot would have fallen on deaf ears,” he writes. “Google says it has a respectable 181 citations, and in my experience, the reception has been generally positive.”
The fact that his study has 181 citations and a positive reception is no evidence for the open-mindedness of his colleagues or for its accuracy. As such, he is making an illegitimate appeal to authority.
I point out that his own 2013 paper acknowledged that the mid-Atlantic hot spot could reflect ocean-dynamic variability, it would take roughly two more decades to judge it unprecedented, and that the indices were within past variability.
In other words, his 2013 study adds nothing important to the study of sea level rise.
Kopp’s accusation that I am engaging in “sociology” is an interesting bit of psychological projection. Recall that he is the one who suggests that his study was somehow accurate because it had 181 citations, and the response to it was “generally positive.”
Kopp then offers an analogy that backfires on him.
“By your logic,” he writes, “we should never say ‘the temperature outside my house right now is 70 F’. We should say ‘the voltage in the thermocouple in the digital thermometer outside my house right now is 11 mV. The model of the physics of this thermocouple indicates a temperature of 70 F.’”
But his thermometer analogy underscores the problem. Converting a thermocouple’s voltage to a temperature reading is a simple, standardized measurement, while his efforts to show a “global mean sea level acceleration” are enormously complicated, requiring combining a sparse, uneven network of tide gauges with assumptions about spatial covariance, applying vertical land motion and GIA corrections, blending in altimetry, and then averaging across studies.
At this point, Kopp finds another way to talk around the problem by suggesting that he and his colleagues had not misled the public because “high confidence” refers to an assessment based on multiple sources.
It’s an outlandish claim because it’s Kopp’s introduction of multiple sources, his fiddling with assumptions, and his cherry-picking, which make his claim of acceleration not simply unscientific but dishonest.
In sum, our email conversation reveals how Kopp repeatedly introduces irrelevant information clearly aimed at derailing and distracting attention from three essential facts. First, the long-term tide-gauge record does not show acceleration. Second, the models they introduce can show acceleration, deceleration, or linearity. And, third, by cherry-picking the model outputs showing acceleration, and even using models at all, rather than direct, real-world tide gauge data alone, proves that Kopp, his colleagues, and the IPCC are covert political activists who have deceived the world into believing that sea level rise is accelerating.
Abuses of Power
Five days after our exchange, Kopp and 15 of his colleagues demanded that the Journal of Marine Science and Engineering retract Voortman’s study. They wrote that the Journal’s reviewers “failed to recognize the context of this manuscript and the breadth of the existing literature, resulting in at best a superficial review. Upon close examination, we believe the paper contains fatal methodological flaws that compromise the validity of its conclusions and merit retraction.”
But anyone who understands what I explained above will understand what they are doing.
They say that Voortman “stands in contrast both to other studies conducting similar tide-gauge analyses.” Note the language. They don’t say that other studies disprove Voortman; they say it “stands in contrast.” Nor do they say the studies did the same tide-gauge analysis; they say “similar tide-gauge analyses.”
That’s the same strategy Kopp and other scientists use to give people the impression of certain conclusions without directly lying. They complain that Voortman “failed to recognize the context… and the breadth of the existing literature…” But failing to recognize context does not mean the results are wrong.
They say, “Upon close examination, we believe the paper contains fatal methodological flaws…”
And perhaps it does. I do not know. What I do know is that it doesn’t matter if it does. The tide gauge data is the tide gauge data. They do not show an acceleration. And every other way the scientists claim to find acceleration is not scientifically valid, meaning they do not accurately measure what they appear to be measuring.
As troubling is the fact that one of the authors of that retraction demand, Richard Tol, openly admitted that he has no evidence that Voortman and his coauthor De Vos did anything that merited retraction. And yet Tol demanded a retraction anyway. Wrote Tol, “retractions should generally be reserved for fraud or irreproducibility,” and then admitted he had no evidence that Voortman and De Vos had committed fraud, nor that their results couldn’t be reproduced.
Then, Tol admitted in an email to me that he had not even read the papers cited in the retraction demand he signed. As such, Tol has engaged in precisely the kind of irresponsible, unscientific, and unprofessional behavior he is accusing Voortman and De Vos of.
Here’s the bottom line. There is no scientific evidence that sea level rise has accelerated, and, rather, abundant evidence that a group of political activists posing as scientists unnecessarily introduced models, and then cherry-picked their most alarmist outputs, used indirect data, and data from too short of time periods, to deceive the public.
And this is hardly the first time that someone has cherry-picked periods of time too short to show a trend. The New York Times did this on landfalling hurricanes, as you can see below with their graph starting from 1980, even though the data goes back to 1900 and shows no increase.
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Others, including the Financial Times, manipulated the data by failing to correct the data for better detection of hurricanes in recent decades, thanks to satellites.
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And the Environmental Protection Agency (EPA) still does this on heat waves. Google “EPA heat waves” and the first web page you’ll see reveals graphs since the 1960s. Then,the EPA made its graph from 1890 difficult to find on its website. It shows a massive spike in the 1930s before significant human emissions.
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In the end, the fact that there’s no acceleration in sea level should not surprise us, given that we’ve known since 2018 that 89% of the atoll islands that scientists and the media claimed would be destroyed by sea level rise had instead grown or stayed the same size.
If I had to predict how Kopp and his allies respond to this, I suspect they will use distracting non sequiturs, authoritarian credentialism, personal demonization or ad hominem attacks, and obfuscation. “You can’t teach an old dog new tricks.”
The scientists cannot change because they have sunk their entire lives and reputations into a massive deception. It will be interesting, from a strictly psychological point of view, to watch how they behave as more people realize that they deliberately deceived the world.
This scandal is also a damning indictment of mainstream media journalists. They not only failed to see through the charade, some of them may have participated in it — all while, no doubt, telling themselves and other that they were neutral and objective “science journalists” committed to reporting the truth.
The Intergovernmental Panel on Climate Change (IPCC) must not only immediately correct its false claim, it should invite an independent group of experts, including scientists, journalists, and policy experts, to investigate the scandal. If it fails to do so, then it will become increasingly clear to the world that it, and the scientists who create its reports, simply cannot be trusted.
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