BBC correspondent in Milan
Many ski resorts face economic hardship as a result of climate change, the UN environment programme Unep has warned.
Many Alpine ski resorts could lose their customers, the report says
The winter climate warming means that snowfall is becoming less reliable, especially in lower altitude resorts.
The Unep report is being presented at a conference about sport and the environment in Italy's city of Turin, the venue for the next Winter Olympics.
It coincides with the annual international meeting on climate change which is taking place in Milan.
The effects of climate change are already being felt in the world of winter sports.
One ski resort in Scotland, Glencoe, where snow has never been very reliable, has just announced that it is suffering financial difficulties.
But for skiers who can afford to go to the classic winter sports resorts in the Alps, good snow has been virtually guaranteed.
Now the Unep report warns that if the snowline rises by 300 metres - a quite likely scenario - only 63% of Swiss resorts will reliably provide good skiing.
Unep spokesman Nick Nuttall says that Italian and Austrian resorts will also be badly affected.
"One of the classic ones is Kitzbuehl in Austria, a very well-known ski resort, and that is at a low altitude. And the findings seem to indicate that Kitzbuehl faces extinction as a winter sports centre," Mr Nuttall says.
"It's all about reliability and if people can't predict that they're going to find snow when they go skiing, they're going to go somewhere else."
Skiing has the reputation of being a luxury sport, and rich winter sports enthusiasts will be able to afford to move their holidays to the American Rockies or other high altitude areas.
But the people who live in the resort areas in Europe are not rich.
Farmers in these mountain villages depend on winter tourism to supplement their incomes.
Unep also points out that the lower slopes in Europe are used by families from nearby towns, where there is a winter sports tradition, and they are the places where children have traditionally learnt to ski.