Sunday, January 3, 2010

Fast Pace of Glacier Melt in the 1940s: Lower Aerosol Pollution

Saturday, Jan 2nd, 2010

The most recent studies by researchers at ETH Zurich show that in the 1940s Swiss glaciers were melting at an even-faster pace than at present. This is despite the fact that the temperatures in the 20th century were lower than in this century. Researchers see the main reason for this as the lower level of aerosol pollution in the atmosphere.

In Switzerland, the increase in snow in wintertime and the glacier melt in summertime have been measured at measurement points at around 3,000 metres above sea level — on the Clariden Firn, the Great Aletsch glacier and the Silvretta glacier — without interruption for almost 100 years. As part of his doctoral work, Matthias Huss used this unique range of measurements to examine how climate change in the last century affected the glaciers. The work was carried out under the supervision of Martin Funk, professor and head of the Department for Glaciology at the Laboratory for Hydraulics, Hydrology and Glaciology (’VAW’) at ETH Zurich, who is also co-author of the study.

Solar radiation as the decisive factor

In its work, the research team took into account the solar radiation measured on the Earth’s surface in Davos since 1934. Studies over the past two decades have shown that solar radiation varies substantially due to aerosols and clouds, and this is assumed to influence climate fluctuations. Recent years have seen the emergence of the terms ‘global dimming’ and ‘global brightening’ to describe these phenomena of reduced and increased solar radiation respectively. These two effects are currently the subject of more and more scientific research, in particular by ETH Zurich, as experts feel that they should be taken into account in the climate models.

The new study, published in the journal ‘Geophysical Research Letters’, confirms this requirement. This is because, taking into account the data recorded for the level of solar radiation, the scientists made a surprising discovery: in the 1940s and in the summer of 1947 especially, the glaciers lost the most ice since measurements commenced in 1914. This is in spite of the fact that temperatures were lower than in the past two decades. “The surprising thing is that this paradox can be explained relatively easily with radiation,” says Huss, who was recently appointed to the post of senior lecturer at the Department of Geosciences at the University of Fribourg in Switzerland.

Full article here