**Acknowledgements**

We acknowledge the DAR—Department of Regional Autonomies—of the Italian presidency of the Council of Ministers for funding this research.

The photographic comparison of Lys Glacier was performed by Fabiano Ventura in the context of the project 'On the Trail of the Glaciers'— sulletraccedeighiacciai. com.

Pleiades images were obtained from the European Space Agency (project ID 32535). We wish to thank Val d'Aosta region for providing access to the GPS reports and regional technical maps; the meteorological series from Gressoney d'Ejola is available thanks to the efforts and dedication of Umberto and Willy Monterin.
