Matthias Huss, a researcher with Zurich's Federal Institute of Technology, examined solar radiation data from the Alpine town of Davos.

He found that a clearer and cleaner atmosphere during the 1940s, especially over the summer of 1947, allowed more solar radiation to reach the ground, melting the glaciers.

The Alpine ice floes retreated more during that period than at any other time since records began 95 years ago.

More particles in the air during the decades that followed dimmed the sun and allowed the glaciers to expand.

Huss told World Radio Switzerland: “This should not lead people to conclude that the current period of global warming is not really as big of a problem for the glaciers as previously assumed.”

Previous studies have shown that solar radiation can fluctuate widely as a result of cloud cover and atmospheric particles and gases.

The Swiss findings were published in the journal Geophysical Research Letters.

Photo: Matthias Huss / ETH Zurich