For years, climate prognosticators have warned that human-caused global warming is fueling catastrophic sea-level rise, but now climatologist Judith Curry is rocking their boat.

In her latest paper, Ms. Curry found that the current rising sea levels are not abnormal, nor can they be pinned on human-caused climate change, arguing that the oceans have been on a “slow creep” for the last 150 years — before the post-1950 climb in carbon-dioxide emissions.

“There are numerous reasons to think that projections of 21st-century sea level rise from human-caused global warming are too high, and some of the worst-case scenarios strain credulity,” the 80-page report found.

Her Nov. 25 report, “Sea Level and Climate Change,” which has been submitted for publication, also found that sea levels were actually higher in some regions during the Holocene Climate Optimum — about 5,000 to 7,000 years ago.

“After several centuries of sea level decline following the Medieval Warm Period, sea levels began to rise in the mid-19th century,” the report concluded. “Rates of global mean sea level rise between 1920 and 1950 were comparable to recent rates. It is concluded that recent change is within the range of natural sea-level variability over the past several thousand years.”

Such conclusions are unlikely to find favor with the global-warming movement, or within the academic climate “consensus,” where some experts have predicted that mean sea level could rise by five to 10 feet by the end of the 21st century.

Then again, Ms. Curry is accustomed to making waves. The former chair of the Georgia Tech School of Earth and Atmospheric Sciences, she represents one of the biggest names on the so-called “skeptic” side of the climate debate, the counterweight to Penn State climatologist Michael Mann, who leads the “warmist” camp.

She said the problem is that the disaster scenarios are driven by the most extreme forecasts of carbon-dioxide emissions, known as RCP8.5, which she and other critics have described as so extreme as to be implausible.

“[President] Trump, he said something about people talking about the extreme scenarios — well, they are,” Ms. Curry told The Washington Times. “Consideration of extreme scenarios has some value, but they’re portrayed as the expected outcome, and that’s really not useful.”

She argued that a more appropriate estimate would be about 0.2 to 1.5 meters, or six inches to five feet, and that anything over two feet is “increasingly weakly justified.” Mean sea level has risen by about seven to eight inches since 1900.

By lending her prestige to the sea-level debate, she could chill the rash of lawsuits filed by cities and counties in California, Colorado and New York—as well as the state of Rhode Island — calling for oil-and-gas companies to pay billions in damages associated with future coastal flooding.

Ms. Curry agreed that there is a human-caused component to the problem, but said it has more to do with the earth sinking than the oceans swelling.

“In most of those cases where they’re suing, half of the sea-level rise is really from the land sinking, rather than anything that the ocean is doing,” she said. “If you look at Galveston and New Orleans, much more than half is caused by sinking. And this comes from geologic processes, it comes from landfills on wetlands.”

She cited groundwater withdrawal in the Chesapeake Bay area, which has also caused sinking.

“That’s really underappreciated, this whole issue of problems with coastal engineering that we’ve caused that have made things worse,” Ms. Curry said.

Challenging her sea-level conclusions are scientists like Mr. Mann. In a June debate with Ms. Curry at the University of Charleston in West Virginia, he argued that the latest models show that “ice sheets can collapse more quickly than we thought.”

“If you had asked us five years ago what the best estimate was of the sea level rise we could see by the end of the century, we would have told you three feet,” he said, adding, “Well, now if you ask us, we have to say, it may be closer to six to eight feet.”

She and Mr. Mann have sparred before. At a March 2017 congressional committee hearing, he denied calling her a “climate science denier, to which she retorted, “It’s in your written testimony. Go read it again.”

“I think he’s learned that there’s a lot of backlash when he calls me a denier, so he calls me a contrarian,” said Ms. Curry with a laugh. “And I don’t think he’s really mentioned me much lately. I think he’s been burned.”

She said she doesn’t believe her findings on sea-level rise are particularly controversial, saying that they jibe with those of the U.N.’s Intergovernmental Panel on Climate Change.

“It’s pretty well-documented in the literature,” said Ms. Curry. “I frame the problem a little different, and my conclusions are a little different than some people, but this has been pretty well-documented and supported.”

Ms. Curry left academia in January 2017 for a host of reasons, one of which was the “craziness” associated with the politics of the climate-change debate. She moved to Reno and has since devoted her energies to her company, Climate Forecast Applications Network.

Her clients include the federal agencies and companies in the energy and insurance business seeking answers on the risks associated with climate change. After a lifetime spent in the ivory tower, she said she finds the real-world work rewarding.

“When there’s something that really depends on the outcome and the understanding of this information, rather than just using it as a political tool to drive policy, it’s really a different ballgame,” she said. “People making real decisions, people spending real money — their companies could be hurt by getting things really wrong in either direction. So that’s what I’m trying to help with.”

Given that nobody wants to be labeled a “denier,” what does she prefer to be called? That’s an easy one.

“I’m a scientist. And I regard it as my job to continually reevaluate the evidence and reconsider my conclusions. That’s my job,” Ms. Curry said. “And some people don’t really want scientists. They want political activists. But if you want a scientist, give me a call.”