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A controversial new study has challenged long-standing claims about global sea level rise, arguing that oceans are rising far more slowly than widely reported and showing no clear link to climate change-driven acceleration.

Findings at Odds with Mainstream Science

The research, conducted by Dutch engineering consultant Hessel Voortman and independent researcher Rob de Vos, suggests the average global sea level rise in 2020 was just 1.5 millimeters per year — equivalent to about six inches per century. That figure is less than half the 3–4 mm/year rate often cited in scientific journals and climate reports.

“This is significantly lower than what is generally reported in the media and scientific literature,” Voortman told journalist Michael Shellenberger.

The findings were based on tide-gauge data from 200 stations worldwide, each with at least 60 years of records. Voortman said that in most locations, differences between observed sea levels and model projections were “not significant,” undermining claims of a measurable acceleration.

A First-of-Its-Kind Approach

Voortman said he was surprised that no previous studies had systematically compared projections with long-term tide-gauge observations.

“It is crazy that it had not been done. I began this research in 2021 by reviewing the literature, and there were none,” he explained.

Unlike many climate studies, Voortman and de Vos carried out their analysis without outside funding. Voortman, a hydraulic engineer with 30 years of experience in flood protection and coastal adaptation projects, said his practical work had already raised doubts: “From practice, I had already encountered the situation that sea level projections were exceeding sea level observations.”

Local Factors Over Global Warming?

The study also challenges the reliability of satellite imagery, which many mainstream researchers use to show accelerating sea level rise since the early 1990s. According to Voortman, sea levels were in a natural “trough” in 1993 and a “peak” in 2020, making the appearance of acceleration misleading.

Where noticeable increases were detected, Voortman argued that they were more likely due to local influences — such as earthquakes, construction, or natural post-glacial shifts — rather than a uniform, CO₂-driven global phenomenon.

The researchers claim that the IPCC’s models “significantly overestimate local sea level rise in 2020,” according to their press release.

Calls for Perspective, Not Panic

While urging less “fearmongering” about sea levels, Voortman stressed that his findings should not be seen as outright climate denial.

“It is important to stress that there are good reasons to have models,” he said. “If we as engineers design something in the coastal zone, we need to plan for a technical lifetime of 50 to 100 years. That requires looking into the future.”

Still, he cautioned that both projections and real-world measurements must be considered to ensure infrastructure is designed realistically.

A Debate Far From Settled

The study directly contradicts the bulk of climate science, which has consistently pointed to an acceleration in sea level rise over the past three decades. Critics are likely to argue that Voortman’s focus on tide gauges misses broader global patterns detected by satellites.

For now, the research has injected fresh controversy into one of the most urgent debates of the modern era, raising new questions about how much — and how fast — the oceans are truly rising.