A new special report by the Intergovernmental Panel on Climate Change said Wednesday that glaciers around the world, outside of Greenland and Antarctica but including Europe, are losing 220 billion metric tons of ice a year.
Planpincieux's glacier has been monitored by experts for the past six years.
Mayor Stefano Miserocchi has forbidden access to a section of the Val Ferret, outside of Courmayeur, a popular hiking spot.
Moreno Vignolini, a press officer for civic authorities in Courmayeur, said: "With the strong heat of this summer, there was, between August and the first half of September, an acceleration of the melting of the glacier, at an average rhythm of 35 centimetres by day, up to peaks of 50 or 60 cm on certain days".
A staggering 250,000 cubic meters (8.8 million cubic feet) of ice could break away from the Planpincieux glacier on the Grandes Jorasses mountain in the Mont Blanc massif, experts at the Valle d'Aosta regional government and the Fondazione Montagna Sicura (Safe Mountain Foundation) reported in an analysis.
"It is now news that a glacier on Mont Blanc risks collapsing", he said. But officials say the glacier's precarious status was the result of a climate emergency that had already begun, and over which an global group of scientists sounded yet another alarm this week.
The council of the town of Courmayeur has closed a highway due to the danger.
Italian President Giuseppe Conte recently told the UN General Assembly that the glacier's demise should "shake all of us and mobilise us". "It's an alarm that can not leave us indifferent".
The warning comes as world leaders meet in NY for the United Nations climate action summit.
Specialists on the Secure Mountain Basis, who've been monitoring the glacier since 2013, stated: 'This glacier is atypical because it's temperate, and so is influenced by the temperature of the water flowing under, which significantly exposes it to the worldwide warming in progress'.
"Many glaciers are projected to disappear regardless of future emissions", the new science report said.
Tourism in the Alps makes around £48billion a year for region and supports 12 per cent of employment. If this trend continues, Switzerland could lose all glaciers by the year 2100 if warming continues.