Impacts and Risks of Global Change - Impact of Global Changes on Mountains: Responses and Adaptation - page 35

Extreme weather events are increasing. This means a rising intensity of
storms, extreme droughts, heat waves and forest fi res in some regions and
heavy precipitations and inudations in others. The precipitation variability
is growing.
Environment
Glacier and permafrost smelting
The general climate warming since the end of the Little Ice Age ca. 150
years ago has left distinct traces in the cryosphere. In most high mountain
areas across the world, glaciers have lost mass and surface area (Oerlemans
2005), permafrost thawing has increased thus causing mass movements
(Haeberli et al. 2006), the zone of 'good winters', i.e., those with a continuous
snow cover of 100 days, has withdrawn into higher altitudes (Breiling and
Charamza 1999).
In the Alps, early studies of glaciers were triggered by catastrophic
bursts of glacier lakes in the course of a cooling climate around the year
1600 (Nicolussi 1990). Since the Little Ice Age maximum around middle
of the 19th century, Alpine glaciers have systematically been investigated
(e.g., Schlagintweit and Schlagintweit 1850), since ca. 1890, changes in the
length of the glaciers have been recorded annually (Patzelt 1970). In the
second half of the 20th century, data on glacier mass balances have been
collected by the World Glacier Monitoring Service. A global summary of
changes in the cryosphere in general and the mountain glaciers in particular
is included in the IPCC report (Lemke et al. 2007).
Since their Little Ice Age maximum extension around the middle of
the 19th century, the glaciers of the Austrian Alps have lost at least 50%
of their area (Gross 1987, Bender et al. 2011). The changes in glacier area
are documented by country in glacier inventories (Abermann et al. 2009,
Lambrecht and Kuhn 2007) largely based on remote sensing methods
(Haeberli et al. 2007). Since the end of the last glacier-favouring period from
the mid-1960s until the beginning of the 1980s, with some glacier advances,
an intensive, more and more accelerating retreat of Alpine glaciers has been
observed. Related phenomena, such as the formation of supra- and peri-
glacial lakes require new strategies in glacier monitoring (Paul et al. 2007)
and trigger research on basic mechanisms (Huss et al. 2007).
As consequence of the recent warming, the last two decades being the
warmest since the beginning of instrumental measurements (Lemke et al.
2007), the glaciers of the Alps have undergone a tremendous development
(UNEP and WGMS 2008). Due to negative mass balances, glaciers show
losses both in volume and surface area from year to year. Hintereisferner, one
of the best investigated glaciers in the Austrian Alps (e.g., Span et al. 1997),