The mountains of Papua sit just 450km (280 miles) south of the equator, yet they've worn a crown of "eternal snow" for centuries. That crown, it turns out, was on a lease.

A century ago, the 300km (190-mile) Sudirman Range boasted snow and permanent ice on all four of its major peaks. Today, only small patches cling to Puncak Jaya, also known as Carstensz Pyramid - and those are expected to vanish entirely within a year or two. Glacier cover has shrunk from nearly 1,900 hectares (4,700 acres) in the 19th Century to about 16 hectares (40 acres) today. That's not a decline; that's an eviction notice.

"There is a profound unfairness in this," says Marie Šabacká, a Czech glacier ecologist who traveled to Puncak Jaya last March to be among the last scientists to study Papua's "eternal snow." She notes these tropical glaciers are unique, separated from other glacier systems by thousands of kilometres. Papua hosts the "last remaining tropical ice" between the Andes and Himalayas.

Ice cores from Puncak Jaya preserve a climate history archive, offering data on atmospheric conditions and changes in the tropical Pacific and Western Pacific Warm pool. But this archive is disappearing before scientists have fully studied it.

The retreat is driven by the same forces melting ice worldwide: a warming atmosphere caused by human activity, including burning fossil fuels like coal, oil, and gas. As temperatures rise, the freezing point moves higher, so more precipitation falls as rain instead of snow. El Niño events can accelerate this, while local factors like cloud cover, snowfall, and topography influence the pace. At this altitude, a small temperature increase or shift from snowfall to rainfall can determine whether a glacier survives at all.

The glaciers' retreat is evidence of long-term warming, and their disappearance "removes both a biological habitat and part of a culturally significant landscape."

At least five groups of Indigenous people have deep spiritual ties to Puncak Jaya. The Moni call it Mbainggela, believing ancestors watch over the mountain. The Amungme know the range as Nemangkawi, or the "White Arrow." "Parents and grandparents prayed their children would have hearts like the White Arrow, never straying from the proper path," says Elfrida Natkime, a young Amungme woman. "It symbolises honesty, purity and moral integrity."

Amungme activist Adolfina Kum puts it bluntly: "How would Muslims feel if Mecca were destroyed? How would Catholics feel if Rome or the Vatican were destroyed? For the Amungme people, that is what it feels like when Nemangkawi is destroyed."

The glacier's disappearance isn't isolated. The discovery of vast copper and gold deposits transformed the region in the 20th Century. Entire mountain faces have been excavated, and roads, industrial infrastructure, and settlements have reshaped valleys. Papuans say development brought jobs, roads, education, and economic opportunities - but also environmental degradation and decades of social conflict. Some lost access to ancestral lands as mining expanded. The BBC approached Freeport, which operates Papua's Grasberg mine, one of the world's largest gold and copper operations, for comment.

"Every time I see the mountains, I feel amazed, but I also feel sadness," Natkime says. "Since the company came, I have seen the exploitation. But the development has also provided a livelihood for many people."

Scientists and explorers are racing to document what's left. Using drones and 3D mapping, Danish researcher Klaus Thymann and his team created a detailed model. From the early 2000s to 2025, the glaciated area has receded by 95%, he says. "There's almost no ice left. Those are the facts."

Thymann calls glaciers "incredibly powerful" indicators of climate change. "When people hear that something described as 'eternal' is disappearing, it triggers a reaction," he explains.

Kum believes communities "lose an important source of strength" when sacred places are disturbed. "I often describe it as pulling out the roots of a tree. Once the roots are removed, the tree loses its foundation."

Meanwhile, in other climate news: Nepal plans to use a new flood study to claim millions from a UN climate disaster fund, and when an avalanche killed climber Nirmal Purja, his friends faced the hardest mission of all.