Snow and a warming climate: what eleven winters can and cannot tell you

Why this matters

Cirque exists to make changes in mountain snow something skiers can see for themselves, at the resorts and dates they actually care about. That only works if the evidence is trustworthy, so the site is careful about what its numbers can show.

Eleven winters show variability

The snow figures on Cirque cover 11 winters, 2014/15 to 2024/25. That is enough to show how much one winter differs from the next, and the swings are large: among resorts with a typical season of 100 days or more of natural snow at mid-mountain, the gap between the best and worst winter has a median of 84 days, and at Valle Nevado it reaches 235 days.

Swings that size swamp any gradual change over a decade. A run of good or bad winters can look like a trend and be nothing of the kind, so Cirque does not draw trend conclusions from this record, in either direction.

What a trend claim needs

A trustworthy statement about how natural snow has changed at a resort needs a much longer record, several decades at least, a model that has been checked against measured snow depth, and a stated range of uncertainty. Without all three, a trend line is a guess.

Cirque has started testing its snow model against weather stations that measure snow depth, and plans a longer record from reanalysis weather data going back to the 1950s. Until that work is done and validated, the site sticks to what eleven winters can support.

Keeping the measures apart

Snowfall, the snowpack on the ground, how reliable that snowpack is, and whether the pistes are actually open are four different things. A resort can have heavy snowfall and a thin base after a warm spell, or open pistes on snowmaking with little natural snow. Cirque reports modelled natural snowpack and its reliability, and says so every time.

Questions

Is snow getting less reliable at ski resorts?

Cirque’s current record is 11 winters, which shows how much winters vary but cannot show a trend. Cirque will make no trend claims until it has a longer, validated record.

Why not show a trend from the data you have?

Because winter-to-winter swings are large (a median of 84 days of natural snow between the best and worst winter at well-established resorts) and would swamp any gradual change over a decade.

What is the difference between snowfall and snowpack?

Snowfall is what lands; snowpack is what is left on the ground after melting, settling and wind. Skiing depends on the snowpack.