Sunshine quickened Swiss glacier melt

15th December 2009, Comments 0 comments

Scientists say increased sunshine in the 1940s helped Alpine glaciers melt faster.

Geneva -- A surge in sunshine more than 60 years ago helped Swiss Alpine glaciers melt faster than today, even though higher average temperatures are being recorded now with global warming, Swiss researchers said Monday.

Their study into the impact of solar radiation on Alpine glaciers made the "surprising discovery" that in the colder 1940s, and especially summer 1947, the glaciers lost the most ice since measurements began 95 years ago, according to Zurich's Federal Institute of Technology (ETHZ).

Average temperatures have been rising in the past two decades around the Alps and scientists have said glacier melt is accelerating at unprecedented levels under the impact of warmer climate change.

"The surprising thing is that this paradox can be explained relatively easily with radiation," said one the ETHZ researchers, Matthias Huss, in the university's online review.

"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," he added.

The researchers found from historic data on three Swiss glaciers, as well as radiation recordings from the eastern Alpine town of Davos, that the level of sunshine in the 1940s was eight percent higher than the long term average and significantly higher than now.

As a result, snow and ice melted by about four percent.

A phase of less sunshine -- global dimming -- from the 1950s to 1980s also corresponded to an advance in the lower end of glaciers.

However, the ETHZ scientists said they also found that "temperature-based opposing mechanisms" then came into play about 30 years ago and that warming had been sustained for an unprecedented 20 to 25 years.

The shrinkage in mountain glaciers, which is often easily observable by the naked eye, has been taken as a barometer for climate change.

Martin Funk, head of the glaciology section at ETHZ, insisted that the finding on the impact of solar radiation made little "fundamental" difference to predictions of the impact of global warming on the Alpine landscape.

"Global warming will certainly cause melting over the coming years that will exceed what was found in the 1940s," he told AFP.

The study published in the peer reviewed journal Geophysical Research Letters is part of broader research into the impact of climate change on the Alps and the role of solar radiation in climate models.

"The novelty is that generally the melting of glaciers is associated with temperature," said Funk.

Funk said it would help refine climate models for the Alps over the coming decades by assessing the weight of other criteria such as the sun or ground alongside rising air temperature.

"It's a way of better plotting the evolution of Alpine glaciers. Essentially hydroelectric power companies want to know what quantity of water they can count on in the future," he explained.

Studies have shown that solar radiation can vary substantially due to cloud cover, as well as aerosols -- particles and gases -- in the atmosphere produced by human pollution or natural causes such as volcanoes or tropical sandstorms.

AFP / Expatica

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