Now they have published a new analysis of global glacier changes and say observations of the first decade of the 21st century (2001-2010) compared to all available earlier data from in-situ, air-borne, and satellite-borne observations as well as to reconstructions from pictorial and written sources leads them to believe that observed glaciers currently lose between half a meter and one meter of ice thickness every year – this is two to three times more than the corresponding average of the 20th century.
Rhone Glacier, June 2007. Image: Simon Oberli
"Exact measurements of this ice loss are reported from a few hundred glaciers only. However, these results are qualitatively confirmed from field and satellite-based observations for tens of thousands of glaciers around the world," says explains Michael Zemp, Director of the World Glacier Monitoring Service and lead author of the study .
According to the results, the current rate of glacier melt is without precedent for the time period observed. They also say that the long-term retreat of glacier tongues is a global phenomenon. Intermittent re‐advance periods at regional and decadal scales are normally restricted to a subsample of glaciers and have not come close to achieving the Little Ice Age maximum positions reached between the 16th and 19th century.
As such, glacier tongues in Norway have retreated by some kilometers from its maximum extents in the 19th century. The intermittent re-advances of the 1990s were restricted to glaciers in the coastal area and to a few hundred meters.
In addition, the study indicates that the intense ice loss of the past two decades has resulted in a strong imbalance of glaciers in many regions of the world. "These glaciers will suffer further ice loss, even if climate remains stable," says Zemp.
Citation: Michael Zemp et.al. Historically unprecedented global glacier decline in the early 21st century. Journal of Glaciology. August 3, 2015. doi: 10.3189/2015JoG15J017