Samples of ice from Mont Blanc are to be sent to Antarctica where they will be preserved for future research because glaciers in the French Alps are melting at an accelerating rate.
Generations of scientists will be able to study climate change and the impact of pollution by using air bubbles trapped in the ice.
The samples, which will be kept at the Concordia Research Station, a French-Italian Antarctic base, will constitute "an invaluable scientific legacy", said Jean Jouzel, a climatologist.
Researchers will drop by helicopter some 4300m up on the Col du Dome glacier next month and will spend two weeks drilling to collect three samples up to 140m-long.
One will stay in a freezer in France and the others will go to the South Pole as "property of the international community".
The core samples will provide a record of how the composition of the air and ice changed over the past 150 years, revealing levels of sulphur and nitrogen dioxide pollution as well as the effect of specific events such as the Chernobyl nuclear disaster in 1986.
The cores will be airlifted in isothermal containers and stored under 10m of Antarctic snow, at around -54C, to avoid the risk of a freezer breakdown or power cut were they to remain in France.
It is hoped this will preserve them for centuries.
Scientists believe all France's Alpine glaciers up to 3500m will have vanished by the end of this century.
"At the Col du Dome, we measured a temperature increase of 2.7F (1.5C) in the space of 10 years," said glaciologist Jerome Chappellaz.
He said degradation starts when surface water melts, then seeps into lower layers and alters the "chemical memory" of the ice.