Banks in Switzerland are already refusing to lend money to ski resorts below an altitude of 1500 metres, said Shardul Agrawala, an official conducting a two-year OECD investigation into the threat from rising temperatures.

"Some of the smaller operations are already closing up."

Alpine resorts are experiencing the warmest weather in 1,300 years, according to one climatologist. Experts say the mildness may be a freak of nature but many suspect it is linked to greenhouse gases caused by human burning of fossil fuels.

The warning coincided with the news a women's World Cup skiing slalom race scheduled for Dec. 20 in the French resort of Megeve had been called off because of a lack of snow.

The Paris-based OECD said its work was the first, systematic cross-country study of the Alpine region, covering 666 slopes.

About 90 percent of the 666 slopes had enough snow cover for a reasonable period each year, namely 100 days or more, it said.

A one-degree Celsius rise in temperature would reduce the number with decent snow cover to 500. That change was likely to occur by 2020-2025, according to best estimates, said Agrawala.

A two-degree rise would trim the number of viable slopes to 400, something that could occur by 2050, and a four-degree rise, which is on the cards for the end of the century, could cut the number to just 200.

FEELING FOR SNOW

"Tourism in the Alps is a key contributor to the economy of Alpine countries," the OECD said in a statement. "There are 60-80 million tourists and some 160 million `skier days' in France, Austria, Switzerland and Germany each year."

French holiday company Pierre & Vacances said last week that business was down a bit in its mountain locations. "The snow will come. It will no doubt lead to a wave of reservations, company chairman Gerard Bremond said.

Club Med, a larger company with big ski hotels and clubs, said this week winter bookings were up on last year despite a slowdown in recent weeks due to the lack of snow.

In the long term, the OECD said, making artificial snow was environmentally damaging, and moreover useless above a certain temperature. In France alone, the number of ski stations using fake snow had risen from 10 to 180 since the start of the 1980s.

In terms of regions, the Alpes Maritimes area closer to the Mediterranean was vulnerable, as were Steiermark-Styria in Austria and Italy's Friuli-Venezia-Giulia.

The Grisons, Valais, and Savoie areas of Switzerland, and the Swiss-French border area were less at risk.

Some Alpine ski spots are trying to diversify, said Agrawala, by offering subsidies or marketing to promote tourism on a year-round basis and, in some cases, an end to skiing.

The Alps are not the only spot suffering from weather problems.