Mount Rainier is shrinking (just a bit), new study finds

The Pacific Northwest’s highest peak is a little less lofty than it used to be, according to a new study.

Mount Rainier is now 10 feet shorter than it was in the 1990s, according to a study in the journal Arctic, Antarctic, and Alpine Research, and its summit has moved about the length of a football field to the southwest.

It’s not plate tectonics, volcanic activity, or erosion that has whittled the iconic peak of Washington state.

It’s climate change, researchers say.

Lead author Eric Gilbertson, a mechanical engineering professor at Seattle University, says 20 feet of ice has melted off Rainier’s summit, a perennially icy spot known as Columbia Crest, since 1998.

Rainier’s icecap has thinned enough that a lower, rocky spot on the volcano’s crater rim, a little more than a football field’s length away from the longtime summit, has surpassed the ice dome of Columbia Crest to become the highest point in Washington.

“It's pretty clearly human-induced global warming.” Gilbertson said. “The mountain’s getting warmer, just like everything else in the world. It's just now it's reaching the highest elevations.”

Mountains’ high points are often bare rock, but some, like Mount Rainier, are capped in ice, and their official elevations reflect their icy surface, not their buried bedrock.

While falling and melting snow can make a mountain’s surface rise and fall with the seasons, Gilbertson said the wind-whipped summit of Rainier doesn’t accumulate much new snow.

“Columbia Crest only fluctuates a couple inches from max snow depth in early May to [minimum] snow depth in late August.”

Gilbertson surveyed the summit in August and September 2024 and May and August 2025.

“I actually tried to survey it in 2023 in September, but the mountain was too melted out,” he said. “I couldn't even get to the top. Too many crevasses opened up.”

There are still more than 20 named glaciers on the flanks of Mount Rainier, and the mountain is still home to more ice than any American peak south of Alaska. One glacier, called the Columbia Crest Glacier, sits inside the volcanic crater at the summit.

But Rainier’s newly identified high point is bare rock each summer.

“All told, Mount Rainier is no longer an ice-capped summit,” the researchers from Seattle University, University of California Merced, and Utah State University write.

The video above, from a U.S. Geological Survey helicopter overflight, shows Mount Rainier's summit and its crater rim on Aug. 4, 2025.

The researchers examined the contiguous United States’ five known ice-capped summits, all in Washington state. They found four of the five shrank in height by at least 20 feet, while only two of the five (Colfax Peak, next to Mount Baker, and Liberty Cap, on a flank of Mount Rainier) still have year-round ice atop their high points.

“This fits the pattern we have seen on every glacier we observe in the North Cascades, including on Mount Baker, with significant thinning even near the top of the glaciers,” Nichols College glacier researcher Mauri Pelto, said in an email. Pelto was not involved in the study.

RELATED: Glacierless Peak? The icy realms of Washington’s North Cascades lose their cool

Geologists with Mount Rainier National Park have been documenting the volcano’s glaciers for decades. They have long found that the volcano’s mantle of ice is thinning and retreating uphill as the climate warms.

In 2023, National Park Service researchers said the Northwest’s tallest peak had lost half its ice since 1896, with the losses accelerating in recent years.

Yet the park’s geologists are not convinced of the new study’s findings.

“The results of this study are not confirmed,” Terry Wildy, Mount Rainier National Park’s chief of interpretation, said in an email. “We have concerns about some aspects of the methods used in this particular study, and we are evaluating the results carefully. The National Park Service has requested the raw field data and processing steps from the researchers to independently verify the elevation measurements.”

According to the new paper, Mount Rainier’s highest point is a fraction of an inch below 14,400 feet, or 10 feet below the U.S. Geological Survey’s longstanding official measurement of 14,410 feet.

RELATED: Another three bite the dust: Heat melts Mount Rainier glaciers

Even with modern technology like satellite-linked positioning systems and ground-penetrating radar, pinpointing the location of a mountain peak — or any other spot on a bulging, irregular planet — is not straightforward. There’s a whole science, called geodesy or geodetics, dedicated to accurately capturing the size and shape of the Earth.

“Doing Earth measurement geodesy is like fitting a tuxedo on a squid,” said Gavin Schrock with the Land Surveyors’ Association of Washington.

On top of Rainier, it doesn’t help that brass-capped survey “monuments” — small rods driven into rock to establish geodetic baselines — are repeatedly vandalized or stolen.

Schrock said Gilbertson’s new study was “well put together.” But he said he considers the elevation of Rainier an open question until the surveyors’ association can mount another expedition to the summit in 2026.

Schrock said the group’s latest Rainier expedition, in 2010, found little change in elevation — of either the Columbia Crest icecap or the bedrock deep beneath it — from previous expeditions.

"We had not shown any shrinking or swelling," he said. "It all came in within a few inches of each other."

Elevation measurement generally relies on an abstract coordinate system called a vertical datum — a network of reference locations of known elevation. The datum is revised from time to time, potentially altering measurements that rely on it.

If Gilbertson and coauthors had used the most recent vertical datum, the rocky high point would measure 14,406 feet high — about 4 feet below the current official height.

“No matter which datum is used, the conclusion is exactly the same,” Gilbertson said in an email. “Columbia Crest melted down over 20 feet and is no longer the summit. The new summit is on the southwest rim and is rock.”

Gilbertson said he got into measuring mountains after years of climbing them.

“My primary hobby is peak bagging,” he said.

He has a project to “bag,” or summit, the highest peak in every country on earth.

“I'm at 147 out of 196, so I'm about three-quarters of the way done so far,” he said.

In another paper published in November, Gilbertson and his twin brother Matthew report identifying new national high points in Gambia, Guinea-Bissau, Saudi Arabia, Togo, and Uzbekistan.

About 10,000 people attempt to summit Mount Rainier every year.

Climber H.E. Holmes named Rainier’s summit Columbia Crest after spending two nights there during an expedition in 1891. He mistakenly thought it was the highest point in the United States.