Daytime temperatures well above 30 degrees Celsius (86 Fahrenheit) for most of the past two months have brought discomfort and drought in cities and farms in Switzerland's valleys, matching most of the rest of the continent groaning from the oppressive heat.

But the heatwave has more lethal consequences in the mountains, shifting the freezing point to a much higher altitude and melting the ice that normally binds rockfaces together at the height of the climbing season.

On Thursday, the zero degree mark in the Alps stood at an altitude of 4,200 metres (13,860 feet), well above the more usual 3,000 or so metresfeet) in summer and above the tops of most European mountain peaks.

The sweltering temperatures have also highlighted the role of the Alps, like many mountain ranges with glaciers, as a barometer to assess the extent of climate change and the impact of global warming, according to experts.

"It's a really exceptional situation," Martin Funk, a glaciologist at Zurich's Federal Institute of Technology said.

Three weeks ago, 90 climbers were evacuated by helicopter from one of Switzerland's prized landmarks, the 4,478 metre high (14,777 feet) Matterhorn, following a landslide at 3,400 metres.

Wisps of steam could be seen emerging from the mountain under the beating sun and the mountain was declared off-limits for several days while work was carried out to secure rockfaces.

A Dutch mountaineer was killed on Wednesday, hit by falling rocks while he was tackling the Dufourspitze, Switzerland's highest peak at 4,638 metres (15,217 feet), police said.

Fifty-five people have been killed in mountain accidents in Switzerland so far this year, against 27 or 28 recorded by the Swiss news agency ATS at the end of July same time in previous years.

But mountain rescue services believe that the higher number might be down to the fact that the hot weather has brought more people into the Alps and lulled them into a false sense of security.

While some degree of melting icecaps and glaciers during the summer months is usual, the swathes of white ice which cover some high valleys are receding at a faster rate than usual, experts said.

Funk told the Swiss news agency ATS that the situation could bring about more unpredictable results, such as hidden pockets of water inside glaciers which could suddenly burst, causing water to crash down into valleys or triggering landslides.

Earlier this week, newly formed lakes at the foot of a glacier in the south of the country, the Grubengletscher, were emptied as a precaution, while authorities were keeping a close watch on a growing lake on the Triftsgletscher in central Switzerland.

Climate experts monitoring the Alps warned that this summer's extremes may be the norm for the later half of this century.

Climatologist Martin Beniston, who works for the UN's Intergovernmental Panel on Climate Change (IPCC), and other scientists forecast a 400 to 500 kilometre northwards shift in Europe's climate patterns, giving Switzerland a Mediterranean climate on a par with Tuscany.

Geraniums gracing Swiss chalets can always be swapped for exotic flowers, but for farmers used to milking cows and growing greens the consequences could be far reaching, according to models used by the Swiss environment ministry.

Cows are already suffering because of dried meadows, causing a milk shortage this summer, according to the Swiss milk producers' association.

Up in the mountains, climate change will also hit the livelihoods of low to medium altitude Alpine resorts in 50 to 90 years time. If global warming accelerates there will simply not be enough snow to ski on, Swiss climatologists predict.

SPACE.WIRE