The valley is bathed in the soft glow of winter light.

In the distance, thin trails of smoke rise from a village, drifting toward the snow-packed clouds above.

Ice climbing is widely regarded as one of the most dangerous mountain sports. It takes place in harsh, often subzero conditions on smooth, featureless surfaces with few natural holds. Climbers must navigate a constantly changing element, constantly assessing whether the ice is solid or fragile. Small shifts in temperature or humidity can completely alter the state of an ice-fall.

In the European Alps, glaciers are receding, snow is becoming less frequent, and winters are shortening. In just the past two summers, Switzerland’s glaciers have lost 10 percent of their volume. Scientists warn that alpine regions are warming far faster than the global average, putting sports reliant on snow and ice in peril.

However, the exact timing and nature of these changes remain uncertain. One of the least explored effects of climate change in mountain areas is the alteration of river and stream freezing patterns. Ice-climbing environments have not been the subject of much research, and the latest IPCC report on global ice and snow does little to address how changes in freezing conditions might affect this niche sport.

What they’ve noticed is a growing instability in the ice-falls. Ice on mountain streams is becoming more erratic, and the winter freezing period is getting shorter. This means not only is there less ice to climb, but the ice that does form is less reliable.

Climbers often describe ice-falls as alive. At times, the ice is incredibly solid and safe. But this can change dramatically within just a few hours if the temperature rises, making the ice more unstable. As the world warms, such rapid shifts in temperature are becoming more frequent.

What was once a solid, climbable ice-fall can quickly turn into a deadly hazard. When the ice begins to melt, a frozen waterfall can shed massive chunks—sometimes as large as a van—plummeting down the mountainside. For climbers, this can be fatal.

The waterfall is like a plastic material. The ice and hanging icicles are essentially glued to the rock, and the most dangerous situation arises when a rise in temperature causes the ice to detach from the surface. In the winter sun, a waterfall can go from below freezing in the morning to as high as 20°C within just a few hours. Today, the climate often gives climbers a winter-long spring-like environment.

The decline in ice cover on glacial streams and lakes also impacts mountain ecosystems. Michela Rogora, a researcher at Italy's national water research institute, IRSA-CNR, explains, "In lakes, early thawing disrupts water stratification and circulation, alters chemistry, increases UV exposure, and impacts biological communities—affecting everything from plankton to fish." This change has significant consequences for biodiversity.

Research already suggests that climbers are determined to keep the sport alive. They're willing to adjust their habits, whether by altering when they climb, embracing related activities better suited to the changing environment, or seeking out new locations for the sport.

Even as conditions grow more difficult, ice climbing continues to draw more participants. There are fewer icefalls and they're appearing in shorter windows, but more people are taking up the sport. The increased competition for the remaining ice could lead to a rise in accidents, as the danger grows with more climbers attempting more challenging conditions.

However, not all climbs are viable anymore. As ice continues to melt, some routes are becoming inaccessible altogether. The North Face of the Matterhorn is a good example. In the last two years, there have been no ideal days for a climb. Dry tooling isn’t an option either, as rising temperatures are melting the Matterhorn’s permafrost, which previously kept the rock stable.

In the end, with the sport becoming riskier, conditions more unpredictable, and uncertainty higher, climbers must be more attuned than ever to the signs that a climb should be called off. Unfortunately, this means calling it quits is likely to become more common. It’s going to be tough to decide whether or not it’s safe to climb!