Download Potential Impacts of Climate Change on the

Potential Impacts of Climate Change on the
Kiama Local Government Area
Report prepared by CSIRO for Kiama Municipal Council
March 2005
Report prepared by CSIRO for Kiama Municipal Council
by Paul Holper, Debbie Abbs, Kathy McInnes and Simon Torok
© CSIRO Australia 2005
Important Disclaimer
This report relates to climate change scenarios based on computer modelling. Models involve simplifications
of the real physical processes that are not fully understood. Accordingly, no responsibility will be accepted by
CSIRO or the Kiama Municipal Council for the accuracy of projections in this report or actions on reliance of
this report.
For more information about climate change, see http://www.dar.csiro.au/information/climatechange.html
Address for correspondence:
Paul Holper
CSIRO Climate
PMB No 1, Aspendale, Victoria, 3195
Telephone (03) 9239 4661
Fax (03) 9239 4444
Email [email protected]
Potential Impacts of Climate Change on the Kiama Local Government Area
Contents
Executive summary.....................................................................................................................ii
1. Introduction ............................................................................................................................ 1
2. Current and past climate in the Kiama Local Government Area ........................................... 2
3. How has climate changed in New South Wales? .................................................................. 2
Temperature changes ............................................................................................................ 2
Rainfall changes..................................................................................................................... 2
Sea-level changes.................................................................................................................. 3
4. How may the climate of Kiama change? ............................................................................... 3
Temperature projections ........................................................................................................ 4
Rainfall projections ................................................................................................................. 4
Potential evaporation and moisture balance projections ....................................................... 5
Average surface winds ........................................................................................................... 6
5. Projected changes in climatic extremes ................................................................................ 7
Extreme temperatures............................................................................................................ 7
Drought................................................................................................................................... 7
Extreme rainfall ...................................................................................................................... 8
Extreme winds........................................................................................................................ 8
6. The impacts of climate change .............................................................................................. 9
Agriculture .............................................................................................................................. 9
Water resources ..................................................................................................................... 9
Biodiversity and forests .......................................................................................................... 9
Bushfires .............................................................................................................................. 10
Communities ........................................................................................................................ 10
The coastline ........................................................................................................................ 11
Conclusions ............................................................................................................................. 11
References and further reading ............................................................................................... 12
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Potential Impacts of Climate Change on the Kiama Local Government Area
Executive summary
Higher concentrations of greenhouse gases in the Earth's atmosphere are leading to increased trapping
of infrared radiation. As a result, the lower atmosphere is warming and this is changing our weather and
climate. The global average surface temperature has risen by about 0.6°C since 1900. Globally, 2004
was the fourth warmest year on record, with the 10 warmest years all having occurred since 1990.
Current and past climate
The Kiama Local Government Area has a temperate climate. However, it does experience periods of
subtropical conditions. The Great Dividing Range has a major impact on climate, creating a distinct
coastal climate zone. Kiama’s average daily maximum temperature ranges from 25°C in January and
February to 17°C in July. Average daily minimum temperature varies from 18°C in February to 8°C in
July.
Rainfall in the district is very high compared with much of New South Wales. The Illawarra Escarpment
has a strong influence on the spatial distribution of the region’s rainfall.
New South Wales has become warmer over the past 100 years, with minimum temperatures increasing
more than maxima. There has been an associated increase in the annual number of hot days and an
increase in the number of hot nights. There are fewer cold days and cold nights.
The State’s annual total rainfall has decreased 14.3 mm per decade since 1950, dominated by high yearto-year variability.
Australian average relative sea level has risen by about 1.2 mm per year from 1920 to 2000.
Projected changes
The Kiama region is likely to experience temperature increases of between about 0.5 and 1.5°C by the
year 2030. The warming expected in spring is slightly greater than the average, year-round change, and
the winter warming range is slightly lower.
Future changes in rainfall are uncertain. In general, rainfall in the Kiama region is likely to decrease. The
most pronounced decreases are likely to occur mainly in winter and spring, with reductions from about 0
to 10%. By the year 2030, rainfall is projected to change in the range of –9% to +1% in winter, relative to
1990; –11% to 0% in spring; –6% to +7% in summer and –5 to +4% in autumn.
Evaporation is likely to increase in future across the State as temperatures increase. Over the Kiama
region, the percentage changes in evaporation are largest in winter. By the year 2030, annual-average
evaporation increases of 3 to 11% along the coast are likely, relative to 1990.
While uncertain, there is a tendency for wind increases in spring and summer and decreases in autumn
and winter in the Kiama region.
The Kiama region can expect fewer cool days and cool spells and more warm days and hot spells.
Currently, Nowra experiences approximately 6 days each year with temperatures above 35°C. This is
likely to increase to 7–10 days per year above 35°C in 2030.
Australia is likely to experience a marked increase in the intensity and frequency of extreme daily rainfall
events under enhanced greenhouse conditions. The direction of change in annual rainfall extremes in
south-east NSW is uncertain, but the majority of models show a decrease in rainfall extremes in winter
and increases in summer.
The impacts of climate change
Warmer conditions, changing rainfall patterns, the fertilising effect of increased atmospheric carbon
dioxide levels, increased demand for water and fewer frosts would affect productivity and the types of
crops grown in the region.
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Potential Impacts of Climate Change on the Kiama Local Government Area
Higher evaporation rates would lead to less water for dams and catchments. Climate change reinforces
the need to use water more efficiently. Demand for water would increase as temperatures and
evaporation rates rise.
The changes to climate would have significant effects on the region’s biodiversity.
Productivity of temperate region forests may increase with higher temperature and increased atmospheric
carbon dioxide. However, these benefits are likely to be offset by the effect of decreased rainfall,
increased bushfires and changes in pests. The positive benefit of higher concentrations of carbon dioxide
may be limited in the longer term by the availability of nutrients.
Projected increases in the number of hotter, drier days with the associated increase in forest biomass are
likely to lead to larger, more intense bushfires.
Heat waves are likely to increase in frequency, intensity and duration in the region. These increases may
increase the risk of heat-related health problems, especially in the very old, the very young and those with
chronic lung problems such as asthma. Warmer conditions may also assist the spread of some diseases.
As well as affecting homes, climate change may affect infrastructure, commercial buildings and other
physical assets. Climate change may affect coastal areas through sea-level rise, increased temperatures,
and changed storm events.
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Potential Impacts of Climate Change on the Kiama Local Government Area
1. Introduction
Our atmosphere consists of a mixture of gases including nitrogen, oxygen and water vapour. Also present
are small quantities of carbon dioxide, methane and a number of other ‘trace’ gases.
Sunlight passes through the atmosphere, warming the Earth’s surface. In turn, the land and oceans release
heat, or infrared radiation, thus balancing the incoming energy. Water vapour, carbon dioxide and some of
the other trace gases intercept part of this outgoing radiation, allowing it to warm the lower atmosphere, while
the remainder is emitted to space. This absorption of heat, which keeps our planet warm enough to sustain
life, is called the greenhouse effect. Without heat-trapping greenhouse gases the surface would have an
average temperature of –18°C rather than our current average of 15°C.
Atmospheric trace gases that keep the Earth warm are known as greenhouse gases. About three-quarters of
the natural greenhouse effect is due to water vapour. The next most significant greenhouse gas is carbon
dioxide.
Since the industrial revolution and expansion of agriculture around 200 years ago, we have been releasing
additional carbon dioxide gas into the atmosphere. Today, the concentration of this gas is approximately 30
per cent greater than in the 18th century. Levels of other greenhouse gases have also increased because of
human activities.
Higher concentrations of greenhouse gases in the Earth's atmosphere are leading to increased trapping of
infrared radiation. As a result, the lower atmosphere is warming and this is changing our weather and
climate, adding to the natural greenhouse effect. (The impact of the enhanced greenhouse effect is often
referred to as climate change or global warming.)
There is evidence that we are already seeing the effects of climate change. The global average surface
temperature has risen by about 0.6°C since 1900, with the 10 warmest years all having occurred since 1990
(the warmest year being 1998, followed by 2002, 2003 and 2004). There has been an increase in
heatwaves, fewer frosts, warming of the lower atmosphere and deep oceans, retreat of glaciers and sea-ice,
a rise in sea level of 10–20 cm and increased heavy rainfall in many regions.
Regardless of the actions that we take today, further changes to our climate are inevitable. This is because
about half of the carbon dioxide emitted by human activities is absorbed by the oceans and biosphere,
leaving half in the atmosphere where it has a lifetime of 50–100 years. The long atmospheric lifetime of
gases such as carbon dioxide, and the slow response of the climate system, means that climate change is
likely to accelerate in coming decades.
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Potential Impacts of Climate Change on the Kiama Local Government Area
2. Current and past climate in the Kiama Local Government Area
The Illawarra Region is classed as temperate. However, it does experience periods of subtropical conditions.
The Great Dividing Range has a major impact on climate, creating a distinct coastal climate zone.
Average temperatures vary across the region and are influenced by proximity to the coast and altitude.
Minimum temperatures along the coastal strip, including in the Kiama Local Government Area, are
moderated by the warm waters of the Tasman Sea. These waters create a tongue of milder temperatures
extending down the coast. Kiama’s average daily maximum temperature ranges from 25°C in January and
February to 17°C in July. Average daily minimum temperature varies from 18°C in February to 8°C in July.
Maximum daily temperature exceeds 30°C on an average of eight days each year. Typically, Kiama enjoys
83 clear days each year.
Rainfall in the district is very high compared with much of New South Wales. The Illawarra Escarpment has a
strong influence on the spatial distribution of the region’s rainfall. The highest annual rainfall occurs near the
highest point of the escarpment at Barren Grounds. The lowest rainfall occurs on the coastal plain near Lake
Illawarra. Approximately one-third of the average annual rainfall occurs in January, February and March with
a secondary rainfall peak in June. The Illawarra Escarpment is well known for its extreme rainfall events.
February 1984 and August 1998 saw downpours that had peak intensities greater than 120 mm/hr for one
hour duration and 24-hour totals greater than 400 mm. The February 1984 storm brought more than 800 mm
of rain in just 48 hours; 640 mm of rain fell in 9 hours. The high frequency of localised intense rain events
and the large number of small catchments along the escarpment contribute to the apparent high frequency of
large floods in the Illawarra region.
3. How has climate changed in New South Wales?
Temperature changes
NSW has become warmer over the past 100 years, with minimum temperatures increasing more than
maxima. From 1950 to 2003, the NSW annual mean temperature rose 0.17°C per decade. The State’s
annual mean maximum temperature rose 0.15°C per decade. During the same period, the annual mean
minimum temperature rose 0.19°C per decade.
There has been an associated increase in hot days (35°C or more) of 0.10 days per year, an increase in hot
nights (20°C or more) of 0.26 nights per year. There has been a decrease in cold days (15°C or less) of 0.22
days per year and a decrease in cold nights (5°C or less) of 0.29 nights per year.
In February 2004, NSW and other eastern States experienced a record-breaking hot spell over 40°C at a
number of locations (BoM, 2004a). At Wilcannia, for example, 16 days in a row over 40°C occurred from 6–
21 February 2004. On 13 October 2004, Sydney's maximum temperature of 38.2°C was the hottest October
day in the city since records began in 1858 (BoM, 2004b). Although in isolation such events cannot be
attributed to changing climate, it is reasonable to expect that such events will occur more frequently or earlier
or later in the season than has tended to occur historically.
Rainfall changes
NSW annual total rainfall has decreased 14.3 mm per decade since 1950, dominated by high year-to-year
variability. Rainfall was particularly low during many years in which El Niño was present, including 1965,
1982, 1994 and 2002. (El Niño events happen when ocean surface waters in the eastern Pacific Ocean
warm. Waters off the east coast of Australia are cooler. El Niño events occur every three to eight years, often
lowering rainfall in south-eastern Australia and in some cases, causing widespread drought.)
During the 2002 drought, the low rainfall was accompanied by the highest mean maximum temperatures on
record. Dry periods now are likely to be warmer than in the past, exacerbating the impact of low rainfall.
Temperature increases in NSW mean that there is a tendency for more recent dry periods to be
accompanied by warmer temperatures than in the past. The impact of the 2002 drought would have been
worsened by temperature rises, resulting in increased evaporation and water demand. Decreases in the
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Potential Impacts of Climate Change on the Kiama Local Government Area
annual intensity and frequency of extreme daily rainfall events in NSW are consistent with the decline in
annual mean rainfall since 1950, with strongest decreases at coastal locations.
Sea-level changes
From 1920 to 2000, average relative sea level (including land movement) around Australia rose by about 1.2
mm per year. The total rise over the period was approximately 96 mm. This is less than the global average
due to a trend toward more frequent and intense El Niño events since the mid-1970s. During these events,
sea levels are lower around Australia.
Records from Fort Denison, Sydney, reveal that the frequency of extreme sea-level events in Sydney
has increased. For example, the extreme sea levels that occurred on average once every 10 years before
1950 were found to occur once every 2 to 3 years since 1950. The change is due mainly to increased
frequency of both La Niña and El Niño events during this period. During the La Niña phase, sea levels are
generally higher along Australia’s eastern coastline due to the warmer waters in the eastern Pacific. Severe
storm events that occur during a La Niña event often do more damage than normal, as storm surges and
waves can penetrate further inland, worsening flooding and coastal erosion.
4. How may the climate of Kiama change?
Projections of climate change depend on the extent to which carbon dioxide and other greenhouse gases
increase in the atmosphere. The values presented here are based on emission scenarios that encompass a
broad range of demographic, economic and technical driving forces of greenhouse gas emissions for the
21st century (SRES, 2000). The Intergovernmental Panel on Climate Change Special Report on Emissions
Scenarios (SRES) presents multiple scenarios of greenhouse gas and aerosol precursor emissions for the
21st century. The SRES scenarios, some of which are used to drive climate model projections, cover a wide
range of the main driving forces of future emissions, from demographic to technological and economic
developments. These SRES emission scenarios are assumed to be equally plausible and represent a large
range of emissions uncertainty. A second source of uncertainty lies in our understanding of the climate
system and how much warming is produced by the emitted greenhouse gases. This uncertainty is addressed
by surveying the climate change results from many global climate models. A third source of uncertainty is the
way that climate change is represented spatially across different climate models. To determine the full range
of uncertainty in projections of climate change, CSIRO chose 12 national and international climate models
that generate the best simulations of Australia’s climate.
In this report, there are references to stabilisation of atmospheric carbon dioxide concentrations at particular
concentrations. The greater the ultimate concentration at which greenhouse gases are stabilised, the greater
the likely changes to climate. Stabilisation at 450 ppm and at 550 ppm are lower-range scenarios. Currently,
carbon dioxide concentrations are approximately 380 parts per million.
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Potential Impacts of Climate Change on the Kiama Local Government Area
The subsequent projections of average temperature, rainfall, potential evaporation, moisture balance and
average and extreme wind are presented as an average over the area enclosed in red in Figure 1. They
include the uncertainties associated with the factors described above.
-30°S
Sydney
Kiama
Nowra
-35°S
Moruya
-40°S
150°E
Figure 1: South-east NSW region over which projections of temperature, average rainfall, evaporation, water
balance and average and extreme winds have been prepared.
Temperature projections
Table 1 shows the projections of temperature change for the Kiama region. Temperatures may increase by
between about 0.5 and 1.5°C by 2030 under the full range of SRES scenarios with a slightly greater range of
warming in spring (0.5 to 1.6°C) and a slightly reduced warming range in winter (0.5 to 1.3°C). Under a
scenario of stabilisation at either 450 or 550 ppm, the upper range of warming is reduced to about 1.0°C
whereas the lower range is approximately unchanged. By 2070, the SRES scenarios indicate a greater
range of warming in spring (1.0 to 4.9°C) and a narrower range of warming in winter (1.0 to 4.0°C). Once
again, under the stabilisation scenarios, the upper range of the change is reduced by about half, illustrating
the impact that mitigation policies could have on reducing the likelihood of severe temperature increase.
Table 1: Projected changes in average temperature (°C) for the years 2030 and 2070 relative to 1990
averaged over the region shown in Figure 1.
Scenario
Annual
SRES (full uncertainty)
Stabilisation at 450 ppm
Stabilisation at 550 ppm
0.5 to 1.4
0.4 to 1.0
0.5 to 1.1
SRES (full uncertainty)
Stabilisation at 450 ppm
Stabilisation at 550 ppm
1.0 to 4.3
0.9 to 2.2
1.1 to 2.7
Temperature rise (°C relative to 1990)
Summer
Autumn
Winter
2030
0.5 to 1.5
0.4 to 1.4
0.5 to 1.3
0.4 to 1.0
0.4 to 1.0
0.4 to 0.9
0.5 to 1.1
0.5 to 1.1
0.5 to 1.0
2070
1.0 to 4.4
1.0 to 4.1
1.0 to 4.0
1.0 to 2.3
0.9 to 2.1
0.9 to 2.1
1.1 to 2.8
1.1 to 2.5
1.2 to 2.6
Spring
0.5 to 1.6
0.4 to 1.2
0.5 to 1.2
1.0 to 4.9
0.9 to 2.5
1.1 to 3.1
Rainfall projections
Future changes in rainfall contain large uncertainty. This uncertainty arises because some models simulate
increasing rainfall while others simulate decreasing rainfall. In general, rainfall in the Kiama region is likely to
decrease. The most pronounced decreases are likely to occur mainly in winter and spring with the rainfall
4
Potential Impacts of Climate Change on the Kiama Local Government Area
reduction from about 0 to 10%. In summer and autumn, the direction of rainfall change is uncertain with
decreases or increases possible.
By the year 2030, rainfall is projected to change in the range of –9% to +1% in winter, relative to 1990; –11%
to 0% in spring; –6% to +7% in summer and –5 to +4% in autumn (Table 2). By 2070, these ranges of
change approximately triple. Limiting atmospheric greenhouse gas concentrations would reduce the limits of
the projected rainfall changes.
Table 2: Projected changes in average rainfall for the years 2030 and 2070 relative to 1990.
Scenario
Annual
SRES (full uncertainty)
Stabilisation at 450 ppm
Stabilisation at 550 ppm
–6 to +2
–4 to +1
–5 to +1
SRES (full uncertainty)
Stabilisation at 450 ppm
Stabilisation at 550 ppm
–18 to +6
–10 to +3
–12 to +4
Rainfall Change (% relative to 1990)
Summer
Autumn
Winter
2030
–6 to +7
–5 to +4
–9 to +1
–5 to +5
–3 to +3
–6 to +1
–5 to +5
–4 to +3
–7 to +1
2070
–19 to +21
–14 to +12
–26 to +4
–10 to +11
–7 to +6
–13 to +2
–12 to +13
–9 to +8
–16 to +3
Spring
–11 to 0
–8 to 0
–9 to 0
–35 to 0
–18 to 0
–22 to 0
Potential evaporation and moisture balance projections
Potential evaporation is the potential of the local air to evaporate available water from open water or soil, and
transpire water from plants. Atmospheric moisture balance is a measure that takes into account changes in
both potential evaporation and rainfall, that is, it is the moisture that remains after evaporation has occurred.
Atmospheric moisture balance cannot be used to infer likely changes in runoff or in other hydrological
measures.
Evaporation is likely to increase in future across the State as temperatures increase. The increases are
greatest in the north-west of the State. Over the Kiama region, the percentage changes are largest in winter.
By the year 2030, the SRES scenarios give annual-average increases of 2 to 5% along the coast, relative to
1990. By 2070, the annual average increase is 4 to 16% along the coast. If carbon dioxide concentrations are
stabilised at 550 ppm by the year 2150, the upper limits of the SRES potential evaporation changes are
reduced by 1% by 2030 and 10% by 2070. If carbon dioxide concentrations are stabilised at 450 ppm by the
year 2090, the annual average upper limits of the SRES potential evaporation changes are reduced by 1%
by 2030 and by 8% by 2070 (Table 3).
Table 3: Projected changes in potential evaporation for the years 2030 and 2070 relative to 1990.
Scenario
Annual
SRES (full uncertainty)
Stabilisation at 450 ppm
Stabilisation at 550 ppm
2 to 5
2 to 4
2 to 4
SRES (full uncertainty)
Stabilisation at 450 ppm
Stabilisation at 550 ppm
4 to 16
4 to 8
5 to 10
Potential Evaporation Change (% relative to 1990)
Summer
Autumn
Winter
Spring
2030
1 to 4
1 to 6
3 to 11
2 to 8
1 to 3
1 to 5
3 to 8
2 to 6
1 to 3
1 to 5
3 to 8
2 to 7
2070
3 to 12
3 to 19
6 to 33
4 to 26
2 to 6
3 to 10
6 to 17
4 to 13
3 to 8
3 to 12
7 to 21
5 to 16
Decreases in annual moisture balance occur across the State with the largest in the north and smallest along
the coast. Table 4 summarises the average annual changes in moisture balance over the Kiama region.
There is a reduction in available moisture of between 20 and 105 mm by 2030 and between 45 and 325 mm
by 2070. Stabilising greenhouse gases at 450 ppm reduces the upper range of the moisture deficit by 30 mm
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Potential Impacts of Climate Change on the Kiama Local Government Area
by 2030 and by 160 mm by 2070 while the lower limit is relatively unchanged. Under a 550 ppm stabilisation
scenario, the reduction in moisture deficit is 25 and 125 mm for 2030 and 2070 respectively.
Table 4: Projected changes in annual moisture balance for the years 2030 and 2070 relative to 1990.
Scenario
SRES (full uncertainty)
Stabilisation at 450 ppm
Stabilisation at 550 ppm
Change in Annual Moisture Balance (mm relative to 1990)
2030
2070
–20 to –105
–45 to –325
–20 to –75
–40 to –165
–20 to –80
–50 to –200
Average surface winds
Future changes in wind speed contain large uncertainty in most seasons because the range of possible
change spans zero owing to the fact that some climate models simulate increase and some decrease in this
variable. Table 5 shows that annual-average wind-speed over the Kiama region may change in the range of
–1.3% to +1.6% by 2030 and –3.9 to +4.9% by 2070. There is a tendency for wind increases in spring and
summer and decreases in autumn and winter. However, over the southern Tasman Sea, there is a tendency
for wind increases during winter, spring and summer in the range of –2.5 to +5%. The ranges of change for
the two stabilisation scenarios are narrower than those for the SRES scenarios, illustrating the marked effect
that deliberate attempts to limit greenhouse gas emissions could have on future climate change, particularly
by 2070.
This tendency towards positive increases in wind speed may have an impact on wave climate over the
Kiama region. The total annual wave climate for the central coastal region of NSW is made up of waves
originating from the north-east (17%), east (42%) and south-east (41%). North-east waves occur
predominantly in summer, and are of relatively low amplitude (1.25m). Easterly waves occur year round and
south-easterly waves have a broader spectrum of wave heights, reaching summer and winter maxima of 4 m
(Short and Trenaman; 1990). Five dominant meteorological systems contribute significantly to the overall
wave climate in this region. These are tropical cyclones, east coast lows, low pressure systems in the
southern Tasman Sea, anticyclones and sea breezes. Hennessy et al., (2004) looked at how the various
storm systems may change as a result of climate change. They found that cut-off lows contributing to the top
one percent of wind speeds showed small increases in frequency in both summer and winter halves of the
year as did southern Tasman lows in winter. While the cause of the increase cannot be determined
precisely, severe wind speeds were also found to increase in the southern Tasman Sea in the majority of
climate models examined. This suggests an increase in wave energy from the south-east as well as a
possible increase in extreme sea levels events along the southern half of the NSW coast.
Table 5: Projected changes in average wind speed for the years 2030 and 2070 relative to 1990.
Scenario
Annual
SRES (full uncertainty)
–1.3 to 1.6
Stabilisation at 450 ppm
–0.9 to 1.2
Stabilisation at 550 ppm
–1.0 to 1.2
SRES (full uncertainty)
–3.9 to 4.8
Stabilisation at 450 ppm
–2.0 to 2.5
Stabilisation at 550 ppm
–2.4 to 3.0
10 m Wind Change (% relative to 1990)
Summer
Autumn
Winter
2030
–0.7 to 1.8
–2.6 to 2.0
–2.4 to
1.1
–0.5 to 1.4
–1.9 to 1.5
–1.8 to
0.8
–0.5 to 1.4
–2.0 to 1.5
–1.9 to
0.8
2070
–2.2 to 5.6
–7.9 to 6.2
–7.5 to
3.3
–1.1 to 2.9
–4.1 to 3.2
–3.9 to
1.7
–1.3 to 3.5
–4.9 to 3.8
–4.6 to
2.0
6
Spring
–1.4 to 3.7
–1.0 to 2.8
–1.1 to 2.9
–4.3 to 11.5
–2.2 to 6.0
–2.7 to 7.1
Potential Impacts of Climate Change on the Kiama Local Government Area
5. Projected changes in climatic extremes
Extreme temperatures
Small changes in average temperature can be associated with large changes in extreme daily temperatures.
Changes in extreme temperatures are determined by applying the range of projected change in average
temperature to observed daily temperature records, and analysing the modified record for changes in
extreme events above or below specific thresholds (Hennessy et al., 2004a).
Projections for extreme daily temperatures are discussed for three sites in the Kiama region: Sydney, Nowra,
and Moruya, for which high quality observed daily data were available from the Bureau of Meteorology over
the last 40 years (1964–2003).
The annual frequencies of four types of extreme temperature events were considered: days below 5°C, three
consecutive days below 5°C (cool spell), days above 35°C and three consecutive days above 35°C (warm
spell). Results are summarised in Tables 6 and 7. In general, cool days and cool spells show a declining
trend while warm days and warm spells show an increasing trend. Table 7 shows the average number of
days above 35°C for 2030 and 2070 for a low and high scenario.
Table 6: The average number of days per year below 5°C at three NSW sites for present conditions (1964–
2003), 40 years centred on 2030 and 40 years centred on 2070. A cold spell was defined as three
consecutive days below 5°C.
Site
Nowra
Sydney
Moruya
Days Below 5°C
Present
29
1
31
2030
9–25
0–1
8–25
Spells Below 5°C
2070
0–18
0
0–17
Present
4
0
5
2030
0–3
0–0
1–4
2070
0–2
0–0
0–2
Table 7: The average number of days per year above 35°C at three NSW sites for present conditions (1964–
2003), 40 years centred on 2030 and 40 years centred on 2070. A hot spell was defined as three
consecutive days above 35°C.
Site
Nowra
Sydney
Moruya
Days Exceeding 35°C
Present
6
3
2
2030
7–10
3–6
2–3
2070
8–24
4–18
2–7
Spells Above 35°C
Present
0
0
0
2030
0–0
0–0
0–0
2070
0–1
0–1
0–0
Drought
CSIRO investigated changes in future drought frequency using the Bureau of Meteorology's criteria for
serious rainfall deficiency. CSIRO did this by using observed monthly rainfall data from 1961 to 2000 and
modifying seasonal rainfall projections for the south-east region of New South Wales for 40 years centred on
the years 2030 and 2070. As rainfall projections indicate increases or decreases, depending on the climate
model chosen, it follows that drought frequency may also undergo increases or decreases.
The average drought frequency during 1961–2000 is about three months per decade. In the 40-year period
centred on 2030, the projections indicate that increases and decreases in drought frequency are possible.
The drought frequency is increased by about 70% for the worst case (decreased rainfall) scenario and
decreased by 35% for the best case (increased rainfall) scenario by 2030. The range of uncertainty is much
larger by 2070, when drought frequency could increase by more than 200% or decrease by up to 70%.
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Potential Impacts of Climate Change on the Kiama Local Government Area
Extreme rainfall
Australia is likely to experience a marked increase in the intensity and frequency of extreme daily rainfall
events under enhanced greenhouse conditions. The direction of change in annual rainfall extremes in southeast NSW is uncertain, but the majority of models show a decrease in rainfall extremes in the south-east in
winter and increases in summer.
The patterns of change for the 3-day extreme rainfall events are mostly similar to those of the 1-day events.
The greatest agreement between models is along the coastal regions, where 3-day events are projected to
decrease in intensity in autumn, winter and spring but increase in summer.
The average projected changes in the 1-in-40 year intensity for each region is presented in Table 8 for the 1day and the 3-day events. In the south-east, rainfall extremes are projected to decrease in all seasons
except summer.
The changes presented in Table 8 should be used with caution. The complex terrain of the south-east has a
major effect on extreme rainfall events and these effects are not captured by the coarse resolution of the
climate models considered in this study. A modelling study by Abbs (2004) has found that on the local scale,
changes in rainfall extremes may show localised increases of up to 30% in mountainous regions, in locations
where the climate models project changes between –10 and +10%. This effect is likely to be evident along
the Illawarra Escarpment.
Table 8: Projected regional changes in intensity of the 1-in-40 year 1-day and 3-day rainfall events for each
season and annually for 2030 and 2070 for the south-east region. All changes are relative to the climate of
1961–2000.
Event
1-day
3-day
ANN
2030
2070
+7%
+5%
+10%
+3%
DJF
2030
2070
+12%
+10%
+22%
+15%
MAM
2030
2070
–3%
–3%
–5%
–5%
JJA
2030
=
–5%
2070
–7%
–8%
SON
2030
2070
=
=
–5%
–8%
Extreme winds
Extreme wind is defined as the 95th percentile – that is, the monthly wind–speed exceeded only 5% of the
time. Table 9 presents extreme wind projections for the Kiama region. During summer, there is a bias toward
increasing wind-speeds in the range of –1.5 to 2.2% by 2030 and by 4.6 to 6.6% by 2070. In autumn,
extreme wind-speeds tend toward decreases in the range of –5.3 to +1.7% by 2030 and –16 to +5% by
2070. In winter, there is a tendency toward extreme wind-speed increases with changes in the range of –3 to
+6.1% by 2030 and –9.2 to +18.4% by 2070. In spring wind changes are less certain with changes in the
range –4.8 to +4.4% by 2030 and –14.5 to +13.4% by 2070.
Table 9: Projected changes in extreme winds for the years 2030 and 2070 relative to 1990.
Scenario
Summer
SRES (full uncertainty)
Stabilisation at 450 ppm
Stabilisation at 550 ppm
–1.5 to 2.2
–1.1 to 1.5
–1.2 to 1.7
SRES (full uncertainty)
Stabilisation at 450 ppm
Stabilisation at 550 ppm
–4.6 to 6.6
–2.4 to 3.4
–2.9 to 4.1
10 m Wind Change (% relative to 1990)
Autumn
Winter
Spring
2030
–5.3 to 1.7
–3.0 to 6.1
–4.8 to 4.4
–3.8 to 1.2
–2.2 to 4.4
–3.4 to 3.2
–4.1 to 1.3
–2.3 to 4.7
–3.7 to 3.4
2070
–16.0 to 5.0
–9.2 to 18.4
–14.5 to 13.4
–8.3 to 2.6
–4.8 to 9.5
–7.5 to 6.9
–10.0 to 3.2
–5.8 to 11.5
–9.1 to 8.4
8
Potential Impacts of Climate Change on the Kiama Local Government Area
6. The impacts of climate change
Agriculture
Warmer conditions, changing rainfall patterns, the fertilising effect of increased atmospheric carbon dioxide
levels, increased demand for water and fewer frosts would affect productivity and the types of crops grown in
the region. In addition, farmers may be faced with more weeds and other invasive species as well as
changing domestic and international markets. The region’s farmers already face an extremely variable
climate so their ability to manage climate change is high, but climate change can still create severe stress on
communities, families, finances and the business of farming.
The higher rainfall coastal regions could in future become more important for agriculture compared with
areas in the west of New South Wales, where projections are for more drying in summer and spring
(Hennessy, 2004a).
Grazing (dairy and beef), fodder production and horticulture (vegetables, viticulture, berries and cut-flowers)
are the main agricultural activities in the region. For high rainfall pastures, the negative effect of higher
temperatures is likely to cancel out the positive effect of higher concentrations of carbon dioxide. Evaporation
exceeds rainfall for most months and is a particular problem in spring and early summer, reducing the
availability of dairy pastures at that time of the year. It may become necessary to sow alternative species of
pasture that are more resilient to anticipated future climate. A projected decrease in average rainfall,
especially in spring, would affect pasture production and thus animal production. Warmer conditions would
also increase heat stress in dairy cattle, which could reduce milk production, unless management measures
such as shade sheds, and sprinklers are adopted.
Higher temperatures would reduce the amount of winter chilling, which is important for setting of some fruits,
and it may become necessary to consider low chill varieties and alternative management options. In
viticulture, higher temperatures may reduce grape quality.
Water resources
Higher evaporation rates would lead to less water for dams and catchments. Climate change reinforces the
need to use water more efficiently. Demand for water would increase as temperatures and evaporation rates
rise. Based on the projected range of regional rainfall and potential evaporation change, runoff in the rivers is
likely to decrease. In the region, these changes are likely to increase stress on rivers. Lower flows and higher
temperatures would also reduce water quality by creating a more favourable environment for microbes and
algal blooms. Wetlands provide habitat for birds and other wildlife and have been shrinking due to a variety
of causes. Decreases in runoff due to climate change have the potential to contribute further to this decline.
The Illawarra Escarpment is well known for its high intensity rainfall events. It is likely that these events will
become more frequent and more intense in future. A new study is underway examining the effects of climate
change on the intensity and frequency of extreme rainfall events along the Central Coast of New South
Wales, including the Illawarra region.
Biodiversity and forests
The region contains a variety of biodiversity and habitat types that support a range of threatened, rare and
endangered flora and fauna. However, the distribution of vegetation in the region is patchy and fragmented
9
Potential Impacts of Climate Change on the Kiama Local Government Area
as a result of past clearing. The Kiama LGA and Minnamurra Catchment, for example, are well known and
valued for their outstanding scenic qualities, stemming from the magnificent forested escarpment, the scenic
rural landscapes of the central catchment and a healthy estuary with expansive wetlands on the lowland
plain.
The changes to the region’s climate would have significant effects on biodiversity:
• Habitat fragmentation means that climate change poses similar risks to remnants as to island
ecosystems, where small patches are separated by large distances. Species that can thrive in a range of
environments or have a strong capacity for dispersal and establishment are likely to cope better than
those with narrow requirements or that are unable to migrate.
• Fire regimes and regional hydrology may both alter in response to climate change, thus placing continued
stress on fauna.
• Coastal areas are extremely important as a source of marine biodiversity and as a nursery area for
fisheries, although cool water species may decline.
• Estuarine ecosystems and wetlands are threatened by changes to salinity and by sea-level rise. Estuarine
mangrove forests and salt marshes are extremely vulnerable to changes in sea level, especially in
locations where shoreward migration is restricted by human infrastructure.
Research has suggested that temperate region forests in Australia may increase in productivity with higher
temperature and increased atmospheric carbon dioxide concentrations. However, decreased rainfall,
increased bushfires and changes in pests are likely to lead to an overall decline in forest productivity. Also
the positive benefit of higher concentrations of carbon dioxide may be limited in the longer term by the
availability of nutrients. Changing climate is likely to lead to changes in tree, and other, species composition,
possible increased invasion by weeds, and changes to the habitat forests provide for animals. This would
raise new challenges in managing forest areas for biodiversity conservation.
Bushfires
Fire is an essential part of Australia’s ecology. The current bushfire regime for south-east Australia is for a
small number of large fires that do significant damage and many smaller fires that do minimal damage.
Climate change is likely to alter existing fire regimes, through changes in the amount and extent of rainfall
patterns, changes in fuel load (growth, curing rates and composition of grasses), changes in wind regimes,
and possible changes in ignition patterns associated with lightning. Increased carbon dioxide levels, warmer
temperatures and greater summer and autumn rainfall suggest that forest biomass may increase by 25 to 50
percent in eastern and southern Australia by the year 2070. The projected increase in the number of hotter,
drier days with the associated increase in forest biomass is likely to lead to larger, more intense bushfires.
An altered fire regime would reduce the ability of eucalypt forests to regenerate and result in species loss,
alteration of habitat structure and increased invasion of exotic species such as Lantana.
Communities
Heat waves are likely to increase in frequency, intensity and duration in the region. These increases may
increase the risk of heat-related health problems, especially in the very old, the very young and those with
chronic lung problems such as asthma. Warmer conditions may also assist the spread of diseases, including
vector- or food-borne infections such as Ross River virus and Salmonella.
The built environment is vulnerable to climate change. As well as affecting homes, climate change may affect
infrastructure, commercial buildings and other physical assets. Changes in average climate may affect
design and performance, including structural standards, cooling and heating demand and drainage. Likely
increases in the intensity of the heaviest rainfall events would lead to increased flash flooding. In low-lying
coastal areas there will be increased risk of storm surge inundation. Increased coastal erosion rates may
also threaten coastal infrastructure. Higher temperatures and lower average rainfall would lead to increased
pressure on urban water supplies, unless moderated by demand management measures. The need for
increased cooling in summer is also likely to increase peak energy demand. The risk of infrastructure loss
through bushfires is likely to increase.
10
Potential Impacts of Climate Change on the Kiama Local Government Area
The coastline
Climate change may affect coastal areas through sea-level rise, increased temperatures, and changed storm
events. Many natural systems, including estuaries, coastal vegetation, wetlands and reefs, will have difficulty
in adapting to climate change, and climate change may increase their vulnerability. Development trends in
coastal areas due to population and economic growth are likely to lead to greater community risk and
insurance exposure to current and future hazards.
Low-lying wetlands may become vulnerable to more frequent inundation due to sea-level rise, storm surges,
wave events and possibly more extreme runoff events. The region’s coastline is exposed to high wave
activity from the south-east.
The storm systems most conducive to elevated sea levels, through both storm surge and high waves, are
slow-moving low-pressure systems such as cut-off lows or tropical lows that move southward along the
coast. The cut-off lows associated with extreme wind speeds show small increases in frequency and the
spatial distribution of the wind speed change indicates that these systems may exacerbate extreme winds
and sea levels along the southern NSW coast. The changes in the frequencies of other weather patterns
suggests a shift in wave climate, with waves from the south-east becoming more prevalent and likely to
affect the morphology of the southern NSW coast.
Conclusions
Like all areas of Australia, the Kiama Local Government Area is likely to experience changes associated with
rising atmospheric concentrations of greenhouse gases. Temperature is likely to rise by between 0.5 and
1.5°C by the year 2030. The Kiama region can expect fewer cool days and cool spells and more warm days
and hot spells. In general, rainfall in the Kiama region is likely to decrease, with the most pronounced
decreases occurring mainly in winter and spring.
Warmer conditions, changing rainfall patterns, the fertilising effect of increased atmospheric carbon dioxide
levels, increased demand for water and fewer frosts would affect productivity and the types of crops grown in
the region. Higher evaporation rates would lead to less water for dams and catchments.
Although CSIRO has not undertaken a detailed assessment of the likely impacts of climate change on the
Kiama region, this report describes in general terms some of the projected impacts. Affected sectors
examined include agriculture, water resources, biodiversity and forests, bushfires, communities, and the
coastline.
Knowledge of the likely changes to regional climate will assist the Kiama Local Government Area to
undertake adaptation measures that will minimise adverse effects of climate change and maximise
advantages. For example, the Council may consider revising planning guidelines in view of anticipated
changes.
For more detailed information on climate change and its likely impacts on New South Wales, refer to the list
of references and further reading at the end of this report. Extensive relevant material can be found
particularly in Hennessy (2004a and 2004b) and in Pittock (2003).
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Potential Impacts of Climate Change on the Kiama Local Government Area
References and further reading
Abbs, D.J. (2004) A high resolution modelling study of the effect of climate change on the intensity of
extreme rainfall events. In: Staying afloat: Floodplain Management Authorities of NSW 44th Annual
Conference: conference proceedings, Coffs Harbour, NSW. [Tamworth]: Floodplain Management Authorities
of NSW. p. 17–24.
BoM (2004a) NSW February (2004) Heatwave conditions. Bureau of Meteorology media archive.
http://www.bom.gov.au/announcements/media_releases/nsw/2004febnsw.shtml
BoM (2004b).Sydney experiences hottest October day on record. Bureau of Meteorology media archive.
http://www.bom.gov.au/announcements/media_releases/nsw/20041013.shtml.
BoM (2005) Climate information
http://www.bom.gov.au/climate/
CSIRO Atmospheric Research (2001a) Greenhouse effect information sheet.
http://www.dar.csiro.au/publications/holper_2001b.html
CSIRO Atmospheric Research (2001b) Climate change projections for Australia, 8pp.
http://www.dar.csiro.au/publications/projections2001.pdf
Hennessy, K.J., McInnes, K.L., Abbs, D.J., Jones, R.N., Bathols, J.M., Suppiah, R., Ricketts, J.R., Rafter,
A.S., Collins, D., and Jones, D. (2004a) Climate change in New South Wales. Part 2, Projected changes in
climate extremes / consultancy report for the New South Wales Greenhouse Office. Aspendale: CSIRO
Atmospheric Research. 79 p.
http://www.dar.csiro.au/publications/hennessy_2004c.pdf
Hennessy, K.J., Page, C.M., McInnes, K.L., Jones, R.N., Bathols, J.M., Collins, D., and Jones, D. (2004b)
Climate change in New South Wales. Part 1, Past climate variability and projected changes in average
climate / Consultancy report for the New South Wales Greenhouse Office. Aspendale: CSIRO Atmospheric
Research. 46 p.
http://www.dar.csiro.au/publications/hennessy_2004b.pdf
Nature Conservation Council of New South Wales (1999) Towards an Illawarra region vegetation
management plan. http://www.nccnsw.org.au/bushland/reference/vegman/index.html
Pittock, A.B. (2003) Climate change – An Australian guide to the science and potential impacts, Australian
Greenhouse Office, Canberra, http://www.greenhouse.gov.au/science/guide/index.html
Reinfelds, I. (1999) Minnamurra River catchment management strategy.
http://www.kiama.nsw.gov.au/envserv/pdf/Minn_River_Catchment_Man_Plan.PDF
Short, A.D. and Trenaman, N.L. (1992). Wave climate of the Sydney region, an energetic and highly variable
ocean wave regime. Australian Journal of Marine Freshwater Research, 43, 765–791.
SRES (2000) Special report on emission scenarios: Summary for policymakers. A Special Report of Working
Group III of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, UK,
http://www.ipcc.ch/pub/sres-e.pdf, 27 pp.
Victoria Government (2004) Victoria’s climate change regional profile – how will climate change affect us?
http://www.greenhouse.vic.gov.au/impacts/climatechangeaffect.htm
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