Japan’s ‘Godless’ Lake signals the growing impact of climate change

Sunday 15 February 2026 - 09:00

By: Sahili Aya

Japan’s ‘Godless’ Lake signals the growing impact of climate change

In the mountain region of Nagano, an ancient winter ritual is increasingly overshadowed by a warming climate. At Lake Suwa, priests and local residents gather each year before dawn in hopes of witnessing a rare natural phenomenon known as “miwatari” — or “God’s Crossing.” In recent winters, however, the lake has remained stubbornly unfrozen, reinforcing scientific warnings about climate change.

For centuries, the priest of Yatsurugi Shrine has led the annual observation of the lake’s surface. According to tradition, when the lake freezes completely and cracks form ridges across the ice, the raised formations mark the path of a deity crossing the water to visit a divine consort. The event has long been regarded as both sacred and symbolic.

A ritual rooted in history

The phenomenon requires sustained freezing temperatures, typically several consecutive days below minus 10 degrees Celsius, for the lake to solidify. As temperatures fluctuate between night and day, the thick ice sheet expands and contracts, creating fractures that fill with newly frozen shards. These shards collide and rise, forming visible ridges across the surface.

Historical records of the lake’s freezing patterns date back to the 15th century, making them one of the longest continuous climate archives at a single location in Japan. Shrine officials have meticulously documented full freezes and the appearance of the miwatari for generations. In modern decades, measurements have expanded to include water temperature and ice thickness, offering scientists valuable longitudinal data.

Climatologists consider the Lake Suwa chronicle a rare and significant dataset. It allows researchers to compare present conditions with centuries-old observations, providing insight into long-term climate variability in the region.

A disappearing phenomenon

Until the late 20th century, the lake typically froze almost every winter. Since the 1980s, however, full freezes have become increasingly rare. The miwatari has not appeared since 2018, marking one of the longest “godless” stretches on record.

In some winters, brief cold spells have offered hope. This season, observers recorded a full freeze in late January, only to see the ice melt days later before the sacred ridge could form. By early February, shrine officials declared an “open sea” — a term indicating that the lake would likely remain unfrozen until spring.

For religious leaders, the absence carries spiritual weight. For scientists, it signals accelerating global warming. Rising average temperatures have reduced the frequency and duration of deep winter freezes, making conditions unsuitable for the natural process that creates the ice ridges.

Science and spirituality converge

While tradition interprets the crossing as a divine journey, researchers explain it through thermodynamics and ice mechanics. Yet both perspectives converge on a shared concern: nature is changing.

The continued documentation of Lake Suwa’s winters ensures that future generations will understand the transformation now underway. Each year without a crossing becomes part of a growing record that illustrates how global warming is reshaping even the most enduring cultural traditions.

If current trends persist, experts warn that the miwatari phenomenon may eventually disappear altogether — turning a centuries-old winter spectacle into a memory preserved only in archives.