Geoscience Reference
In-Depth Information
Snow
Nicholls (2005) has observed declines in maximum snow depth in the Snowy
Mountains, with spring snow depth declining by 40 per cent between 1962 and
2003. Hennessy et al. (2008b) modelled projected impacts of climate change
on snow cover in the Australian Alps using a range of scenarios for 2020 and
2050. Their worst-case climate change scenario for 2050 (
1
2.9°C,
2
24 per cent
in winter precipitation) is at the extreme low end of the warming likely to
apply at
1
4°C global warming and a mid case for precipitation change, so this
scenario would represent a conservative estimate of Australian snow cover at
4°C global warming.
Figure 2.8
shows their calculated length of snow season for
this scenario across the Alps, compared to current season length. In most regions
currently with a significant snow season on average, annual snow cover goes to
zero. Only in the very highest locations does a snow-season persist, but this is
greatly shortened (for instance, at 2,000 metres in the Snowy Mountains, the
season length is cut to one third its present length).
Sea level rise and coastal impacts
Over the period 1920 to 2000 sea level rise around Australia was 1.2mm a year
(Church et al., 2006). This has accelerated to a rate of 5.9mm a year between
1993 and 2009 (Church and White, 2011). Australia will be affected by the
Hoegh-Guldberg et al., 2013). For a number of reasons, regional sea level rise
can proceed at a different rate from the global rate. In particular, where ice-sheet
loss is a significant contributor to sea level rise - and this is likely as we approach
a Four Degree World - sea level rises least in the area closer to the areas of ice
loss and most further afield, in areas such as the Australian region (Church et al.,
2011). DCC (2009) estimated a sea level rise of 1.1 metres by 2100. Irreversible
melting of the Greenland ice sheet is likely to be initiated at
1
4°C global
warming and would lead to a sea level rise of seven metres, although this will
take many centuries to be realized (Ridley et al., 2010).
The coastal impacts of sea level rise potentially include increased inundation of
low-lying terrain and recession of soft shorelines (DCC, 2009). Severe episodes of
coastal inundation and erosion occur during severe storm events, during which high
waves and storm surges may beset the coast. Patterns of change in high waves and
storm surge may be inferred from changes in circulation patterns that affect mean
and extreme wind patterns. Over Australia, a distinct pattern of wind change has
been projected for 2081-100, relative to 1981-2000, in the climate model ensemble
for the more moderate temperature increases associated with a medium emission
scenario. This shows an increase in mean winds in coastal regions between 25-35°S
in summer and north of 25°S and over the Victorian coast and Tasmania. In winter,
wind speed declines occur between 38-44°S in summer and between 25-35°S south
in winter. A decline in strong winds is seen around much of coastal Australia in
summer and all but Bass Strait and Tasmania in winter (McInnes et al., 2011). This
