No Evidence Climate Change Has Accelerated Sea Level Rise, Finds First Global Study Of Real World Data
Drawing on 100 years of data, the authors found an average rise of just 1.5mm per year
Sep 02, 2025
For over a quarter-century the world’s leading climate scientists and news media have warned that human-caused climate change has doubled the rate of sea level rise and is thus putting civilization in grave danger. “We will see at least four feet of sea level rise and possibly ten by the end of the century,” wrote The New York Times’ David Wallace-Wells in 2019. “The oceans we know won’t survive climate change,” claimed The Atlantic that same year. The author, Robinson Meyer, quoted estimates by Princeton University’s Michael Oppenheimer that sea levels would rise by more than 34 inches by 2100.
When I asked Oppenheimer about those numbers at the time, he told me, “The actual number, which is based on the sea level rise amount in [IPCC Representative Concentration Pathway] 8.5 for its [Special Report on the Ocean and Cryosphere in a Changing Climate] report, is 1.1 meters, which is 3 feet, 7 inches,” or 43 inches.
All of those claims have been proven false by the first-ever global study of sea level rise based on data gathered locally rather than on models extrapolating from assumptions. The Journal of Marine Science and Engineering published the peer-reviewed article, “A Global Perspective on Local Sea Level Changes,” by Hessel Voortman, a Dutch engineer, and Rob de Vos, a researcher, last week.
“The average rate of sea level rise in 2020 is (only) around 1.5 mm/year (15 cm per century),” said Voortman. “This is significantly lower than the 3 to 4 mm/year often reported by climate scientists in scientific literature and the media.”
Indeed, the significance of the study lies in the fact that most of what the media and climate scientists claimed about climate change and sea level rise was false. Scientists and the media tend to focus on the IPCC projections of the extreme upper end of sea level rise despite reality tracking at the very low end.
Voortman conducted the research without financial support and does not deny the reality of climate change, sea level rise, or the need for models. “It is important to stress that there are good reasons to have models. If we as engineers design something in the coastal zone, then we try to achieve a technical lifetime of 50 to 100 years, and that means we need to try to look into the future.”
An expert on the impacts of climate change, Roger Pielke, Jr., said, “Most people are not aware that the scientific community uses different concepts to discuss sea level rise. What matters for communities is what happens where they are located, not an abstract global average.”
Headlines about sea level rise have been catastrophic for decades. Because of sea level rise, the earth would become “uninhabitable,” said the Times’ Wallace-Wells in 2019. “As oceans rise,” wrote Brad Plumer in the New York Times in 2020, “crashing waves and extreme high tides will be able to reach farther inland, putting tens of millions more people and trillions of dollars in assets worldwide at periodic risk of flooding.”
Plumer’s article assumed sea levels would rise 12-36 inches. Instead, it appears they could increase just six inches, the same as during the 20th Century.
Strikingly, nobody in over 25 years of research had done what Voortman and De Vos did. “It is crazy that it had not been done,” said Voortman. “I started doing this research in 2021 by doing the literature review. ‘Who has done the comparison of the projections with the observations?’ And there were none.”
Nobody paid Voortman to do his study, nor does he belong to a university. “I’m a hydraulic engineer by profession, almost 30 years now, and involved in flood protection, coastal infrastructure adaptation projects all over the world,” he explained. “From practice, I had already encountered the situation that sea level projections were exceeding sea level observations.” First he published a paper in 2023 on the discrepancy between projections and what was happening in the Netherlands. “Then, I decided to try to analyze as many locations over the world as possible.”
In other words, despite billions of dollars poured into climate science over the last 25 years from governmental and philanthropic sources, with major climate centers in universities around the world, no scientist had done what Voortman did, without money, off the side of his desk.
Why did the media and scientists get sea level rise so terribly wrong? And why didn’t anyone bother comparing real world data to the predictions of the models? Graduate students sometimes struggle to find gaps in the scientific literature to fill. Why didn’t any of them notice this one? Why did it take an engineer volunteering his time to determine whether sea level rise was accelerating?
Laziness could be a factor. The sea level rise “projections are based on a combination of research on Antarctica, glacier behavior, on thermal expansion,” explained Voortman.” I call them assumptions, but of course they’re assumptions on how the world works, what the expansion of the ocean will be if the temperature increases by one degree, if the temperature increases over 200 meters or 400 meters — that sort of assumption. And you put in what you think you know about physics, and your result is a sea level rise.”
When asked to explain what he did for his research, Voortman said it was “Pretty hard, I would say, although I enjoy cracking hard puzzles.” Voortman described building large data sets and projections. “I had to do a lot of programming and automate data imports and data management. I organized it by using databases so that I really knew what I was doing. It was very structured because I was dealing with 150,000 locations and, on average, 100 years of data. That made one and a half million lines of data. I found myself for days working on things that I felt, ’This is more computer science than civil engineering.’”
Arrogance may be another factor behind why scientists got sea level rise wrong. When asked, “Do you think that the study of sea levels and climate change has been lacking in some of that humility?” Voortman said. “Maybe to an extent, yeah. Sometimes people say they know what in 2100 sea level will be. And I think, ‘No, you don’t know.’ In that sense, I sometimes think people are lacking humility.”
Another factor is that people confuse the real world and projections. “My LinkedIn timeline is currently filling with people saying, ‘Here somebody made a comparison,’ and they show that, 30 years ago, a projection was right. Well, yes one of 15 [or so] projections. They then compare it to the observations and say, ‘Look we were right.’ I’m not too impressed by those studies.”
Voortman emphasized that he didn’t think any of the scientists who came out with more catastrophic numbers had bad intentions. “I don’t believe in bad intentions.”
Voortman instead pointed to the real world focus of engineers compared to scientists. “Checking assumptions is second nature to engineers,” said Voortman, “and that maybe explains why I decided to do it. And maybe less so for scientists. If you have created a nice model on Antarctica then, yeah, you can get your PhD. You have done nice work. You have solved a set of differential equations and dealt with data. You have done your best and you have shown a nice result. I’ve been a scientist in the beginning of my career. I think in science it’s less common to say, ‘I will critically check my assumptions.’ But we engineers work outside.”
He noted that, with improper flood defense calculations, people can lose their homes. “What you don’t want is for your assumptions to be incorrect.”
Voortman said this mentality results in a different culture among engineers. “When two or three engineers are talking with each other, we think we’re working, but other people think we are arguing, because we can be very harsh. But we are always checking each other’s work, always checking each other’s assumptions.”
At the same time, it’s notable that the error when it came to sea level came from exaggerating its size, which is similar to the scientific exaggerations on other issues in recent years, including on atolls, glaciers, ice loss, and coral reefs.
When I pressed Princeton’s Oppenheimer, who overstated sea level rise seven-fold, how he could justify his catastrophic claim that sea level rise would be “unmanageable,” he ended up referring to situations that have proven quite manageable, including the Netherlands’ feat of creating a rich nation that is one-third below sea level.
As such, the same incentives behind climate alarmism were at work when it came to sea level rise. Journalists and scientists have an incentive to exaggerate the effects of climate change to attract attention, readers, and funding. It is notable that none of them contributed to improving or advancing the science of sea level change. Instead, what motivated the real-world research by Voortman and De Vos was an engineer’s mentality, rather than a modeler’s mentality, and a genuine desire to compare models to reality.
The IPCC and the news media have become increasingly politicized and alarmist, so it may not change how they represent, and misrepresent, the science. For example, the list of authors of the next assessment “is stacked with people who focus on extreme event attribution — far out of proportion to their presence in the field,” noted Pielke. “Few of the authors, if any, have expertise in the IPCC’s conventional framework for detection and attribution, and some have no publications on either detection or attribution.”
It’s clear that IPCC is doing this so that it can claim climate change is having an impact on extreme weather, rather than doing this because it is the most accurate way to characterize climate change’s impacts, or lack there of, on extreme weather events, which kill fewer and fewer people, and cause less financial damage, every year.
“Climate advocacy has emphasized connecting extreme events with climate change,” notes Pielke, “promoting the idea that ‘every tenth of degree’ of global temperature increase is associated with more extreme events and more disasters. If only we reduce emissions, the argument goes, we can also modulate extreme weather. In this logic, every extreme event becomes about energy use, and not about exposure, vulnerability, and the local decisions that have seen disaster deaths drop to their lowest in human history….When an assessment is taken over to serve politics it ceases to be an assessment and turns into something else.”
But on studying sea level rise, Voortman sees signs of progress. “I am quite happy with the newest generation of IPCC projections,” said Voortman, because “they are local, give relative sea level rise, estimate land motion, and give their estimate of all kinds of sea level processes adding to sea level rise. Those are spot on in terms of what we need in practice.”
And with his new study, Voortman is now in a position to credibly demand change. “My only criticism on those projections is that you should have compared them to [real world] observations.”
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More info the Voortman Report
Breaking: no acceleration in sea level rise detected worldwide
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