39
The incidence of all heatwave indices is projected to increase in response to climate change (
Figure
4.15
). The number of days with maximum temperatures of 35°C or more is projected to increase to 17.1
per year by 2030 (high emissions, 50
th
percentile) and to as much as 35.8 days per year by 2070 (high
emissions, 50
th
percentile). The incidence of days with temperature maxima over 40°C is projected to
increase to 2.5 and 10.8 days per year under the corresponding scenarios. The maximum number of
consecutive days with temperature maxima over these levels is projected to increase to 11 and 7 days,
respectively, for the 2070 high emissions (50
th
percentile) scenario.
Events with three consecutive days with average temperatures of 32°C or more are projected to increase
from 1 in 20 years on average, to one every 0.7 years by 2070 (high emissions, 50
th
percentile;
Figure
4.15
).
It is interesting to note that the incidence of four or more consecutive days with maximum temperatures of
35°C or more has been greater during 2000-2012 than is projected for 2070 under a high emissions
scenario (50
th
percentile;
Figure 4.15
). Incidences of 40°C maxima and 32°C averages over that period
were similar to those projected for 2030 under a high emissions (50
th
percentile) scenario.
Urban heat island (UHI) effects may exacerbate the intensity of heatwave weather conditions and their
impacts on vulnerable members of the community. They may also vary at relatively small spatial scales,
depending on, for example, exposure to sea breezes, the amount of vegetation present and the extent
and type of paved land surfaces. They have not been taken account of in this study and warrant further
consideration.
4.7.5. Changes in Rainfall
4.7.5.1. Rainfall projections
Annual average rainfall is projected to decrease throughout South Australia through the 21
st
century
(
Figure 4.16
). The median projection is for rainfall to decline by 2-5% in 2030 and by between 5 and 20%
by 2070. The more extreme dry GCMs suggest that rainfall in the Adelaide region may decline by 20-
40% by 2070. The wetter models project small increases in average annual rainfall.
