Climate Change Is Melting Mount Rainier’s Glaciers.

Once, there were 29. Now at least one is gone, maybe three. Those that remain are almost half the size they used to be.

Mount Rainier is losing its glaciers. That is all the more striking as it is the most glacier-covered mountain in the contiguous United States.

The changes reflect a stark global reality: Mountain glaciers are vanishing as the burning of fossil fuels heats up Earth’s atmosphere. According to the World Glacier Monitoring Service, total glacier area has shrunk steadily in the last half-century; some of the steepest declines have been in the Western United States and Canada.

Mount Rainier National Park, a popular tourist destination that gets roughly 2 million visitors every year, is feeling the effects acutely.

Wildflowers, among its main summer attractions, are blossoming at odd times. The season for climbing the 14,000-foot summit is shorter. Douglas firs are climbing down the mountain slopes to areas where there is less snow than before. Rocks are tumbling down from the retreating glaciers, wiping out old-growth forests, changing the course of rivers, and most importantly for the National Park Service, flooding roads that it is supposed to maintain so tourists can drive in and enjoy its wilderness.

One small south-facing glacier, the Stevens, no longer exists and has been removed from the park’s inventory of glaciers. Two others, known as Pyramid and Van Trump, “are in serious peril,” according to an exhaustive survey published this summer by the Park Service, and may well be gone by the time the agency carries out the next survey in the coming year or two, said Scott R. Beason, the park geologist who led the study.

“Killing off a glacier is not something I take lightly,” he said. “Losing them is big.”

His study used historical glacier measurements, satellite images and aerial photography to assemble a three-dimensional map of the park’s snow and ice. It found that the total area covered by glacier ice had shrunk by 42 percent between 1896 and 2021. (Another survey carried out in the fall of 2022 by a glaciologist, Mauri Pelto, concluded that the Pyramid and Van Trump had vanished.)

Glaciers give Mount Rainier its spectacular icy-blue shine. On a clear day, they make the mountain visible from hundreds of miles away.

In a stable climate, glaciers dance to the rhythm of the seasons. They grow every winter with snow and ice. They melt every summer, supplying chilled water to the creeks and rivers downstream, and the plants and animals that rely on them, in the dry season.

Climate change has upset that balance. Spring snowpack has declined since the mid 20th century. Temperatures have gone up. Even when the winter snow is good, an unusually warm spring melts the snow quickly, as it did this year.

The face of Mount Rainier is changing, likely forever.

Mr. Beason noticed it when he drove into the park last week and looked up. The mountain looked “subdued,” he said.

Even for September, there was little winter snow left on the Nisqually Glacier, one of the mountain’s most prominent and largest glaciers. Black boulders clung to the surface of the glacier. Over the years, the mouth of the Nisqually had moved farther and farther up the mountain. “The glaciers at Mount Rainier are in a long-term demise,” the Park Service report warned. “The long-term impacts of this loss will be widespread and impact many facets of the park ecosystem.”

Mountain climbers are facing new challenges, too. Glaciers are the highways they walk on to reach the summit. Those passages are melting earlier and earlier in the summer. The paths to the summit are becoming longer, as climbers have to go around risky cracks and fissures. The climbing season is getting shorter.

On a fog-soupy Thursday morning in August, Paul Kennard, a geomorphologist who retired recently after 20 years with the Park Service, parked his car at the Paradise parking lot, passed the summer visitors who had come to admire the wildflowers and soon went off-trail to climb to the Nisqually.

It is among the glaciers in greatest trouble. Much of it is below 10,000 feet, and it’s on the mountain’s south-facing side, where the heat hits hardest. The very top of the mountain is unlikely to lose its snow and ice. If it did, Mount Rainier, an active volcano, would look very different. “Like Darth Vader’s head,” Mr. Kennard said.

Mr. Kennard stepped nimbly over a fast-moving stream of polished wet stone and then up and down the lateral moraine on the east side of the glacier. Up here, at over 6,000 feet, the surface of the Nisqually was only black boulder and rock, clinging to hundreds of feet of ice underneath. Loose pebbles were perched here and there, making the path up and down the slopes all the more precarious. Large, white bones and teeth littered the ground. Probably a mountain goat, Mr. Kennard surmised, maybe an elk.

To the uninitiated visitor, it didn’t look like a glacier. Mr. Kennard assured that it was. He had climbed the Nisqually at least 75 times, he said. Today, it looked worse than he had imagined.

“A glacier that’s healthy, or at least holding its own, or advancing has a different look,” he said. “It doesn’t look as deflated.”

Underneath some rocks, glistening veins of black ice revealed themselves. Sometimes, you could hear a quiet gurgle of water — a reminder of the frozen river that you were standing on. A roar in the distance meant rocks were falling. The big ones, Mr. Kennard said, pointing to those that were the size of camper vans, could become dislodged and start tumbling down at any time. Depending on their number and speed, they can cause sheer havoc.

The worst he remembers was in 2006, when a glacier burst and sent a mighty slurry of wet sediment and stone down a tributary of the Nisqually River. It sounded to him like a freight train. Huge boulders rolled down. The debris flow, as it’s called, smothered a grove of Douglas firs that were at least 100 years old. The river leaped its banks, changed course and chewed up bits of the 13-mile-long Westside road.

That road remains closed to car traffic. The skeletons of those Douglas firs line the far banks. “I see a river gone wild,” Mr. Kennard said.

A few years ago, just before he retired, Mr. Kennard developed a low-cost solution, using what the mountain was ejecting: tall trees and big rocks. He created a series of log buttresses, sandwiched between boulders and sticking out into the river, in an effort to protect the riverbank from washing away.

It was a pilot project, designed to protect one of the most important structures in the park: the main road that motorists take from the southern entrance. That road sits perilously close to the Nisqually River, running wild as the once-forever ice rivers of Mount Rainier disappear. “Less forever now,” Mr. Kennard said. “The glaciers are falling apart.”