December 14, 2009

Surge In Sunshine Melted Swiss Glaciers

Swiss researchers reported on Monday that a spike in sunshine sixty years ago was responsible for melting Switzerland's Alpine glaciers at a faster rate than they are today.

The researchers examined the impact of solar radiation on the glaciers, and found that during the 1940s, particularly in the summer of 1947, the ice floes lost the most since measurements began being recorded 95 years ago.

Nevertheless, average temperatures have been increasing over the past twenty years, and scientists have said glacier melt is accelerating at unprecedented levels due to climate change.

"The surprising thing is that this paradox can be explained relatively easily with radiation," said Matthias Huss, a researcher with Zurich's Federal Institute of Technology (ETHZ).

"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," the AFP news agency quoted him as saying.

The researchers used historic data on three Swiss glaciers and radiation recordings from the eastern Alpine town of Davos, and found that the level of sunshine in the 1940s was eight percent higher than average and substantially above what it is today.

As a result, roughly 4 percent of the snow and ice melted.

A phase of less sunshine, or "global dimming", took place from  the 1950s to 1980s, resulting in the glaciers' advance.

The ETHZ scientists said that "temperature-based opposing mechanisms" came into play some three decades ago, and have been sustained ever since.

The study was part of a comprehensive research initiative into the impact of climate change on the Alps, and the role that solar radiation plays in climate models.

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

The study was published in the journal Geophysical Research Letters.

Reference: Huss M, Funk M & Ohmura A: Strong Alpine glacier melt in the 1940s due to enhanced solar radiation. Geophysical Research Letters (2009), 36, L23501, doi:10.1029/2009GL040789


Image Caption: In the 1940s, the glaciers were melting at a faster pace than today. An image of the Gorner glacier. (Image: Matthias Huss / ETH Zurich)


On the Net: