Australia's changing climate and its implications for the built environment
Australia has a significant amount of residential dwellings, other
buildings and infrastructure. As the Australian Sustainable Built Environment
Council (ASBEC) explained, 2015 figures indicate that there are almost
8 million buildings across the country, and that these buildings have a
replacement cost of approximately $5.7 trillion. These buildings include:
- over 7.5 million residential buildings with a replacement value
of $3.5 trillion;
- around 215,000 commercial buildings worth $1.8 trillion; and
around 139,000 industrial buildings worth $0.3 trillion.
Other essential infrastructure networks are also extensive and of high
value, such as roads, railways and energy infrastructure.
These buildings and other infrastructure assets need to withstand the
Australian climate. Australians are already familiar with extreme events such
as heatwaves, cyclones, bushfires and floods that have caused extensive damage
to cities and infrastructure and resulted in deaths and injuries. Due to
climate change, however, many types of extreme events are expected to become
more frequent or more intense. Coastal areas are also experiencing rising sea
levels and more intense storm surges.
Damage from extreme events can already be significant, both in terms of
human life and economic cost. To understand the implications for Australia's
infrastructure, this chapter highlights the evidence received about recent
changes to the climate system, terrestrial environment and the marine
environment that are relevant when considering future challenges for housing,
buildings and infrastructure.
Available evidence about projected changes is also discussed, noting
that there is uncertainty about such projections and that future changes are
dependent on the emissions pathway taken. In doing so, the report refers to the
four emission pathways adopted in the Fifth Assessment Report of the Intergovernmental
Panel on Climate Change (IPCC). The following extract from CSIRO's submission
provides a useful explanation of the IPCC's emissions pathways framework:
The magnitude and nature of multi-decadal to centennial
climate change that the world is likely to experience depends strongly on
actions to reduce the emissions of greenhouse gases. The Intergovernmental
Panel on Climate Change's Fifth Assessment Report (IPCC AR5) adopted four
Representative Concentration Pathways (RCPs) to span the range of possible
future trajectories in terms of the resulting greenhouse gas concentrations in
the atmosphere. The four RCPs are RCP2.6, RCP4.5, RCP6, and RCP8.5; these are
named technically after future radiative forcing values, but basically range
from very low to high emissions pathways, and include the effects of burning
fossil fuels as well as greenhouse gas emissions from land use change and
industrial processes such as concrete manufacturing. The Paris Agreement goals
are consistent with a future concentration pathway that falls between RCP2.6
and RCP4.5; whereas current commitments by countries are more consistent with
the RCP4.5 trajectory at least until 2030 or so...RCP4.5 is often referred to as
an 'intermediate emissions scenario'. A continuation of historical emissions is
more consistent with the RCP8.5 trajectory. Given there is not yet any
certainty that the world will meet the Paris Agreement commitments, good risk
management should consider this whole range of future climates.
Sea level rises and coastal erosion
Sea levels have risen over the 20th century as a result of ocean thermal
expansion and an increase in water entering the ocean from melting glaciers and ice caps. CSIRO submitted that between 1966 and 2009, the average rate of relative sea
level rise from observations along the Australian coast was 1.4 ± 0.2
millimetres per year. Globally, sea levels increased between 1993 and 2016 at 'an average rate of 2.6
to 2.9 millimetres per year, amounting to a total increase in the order of
7 centimetres over that period'.
A joint submission from several Australian Government departments and
agencies added that the overall trend in sea level rise is affected by
variability, such as El Niño and La Niña events. The submission noted:
A strong event, such as the 2015-16 El Niño or the 2010-11 La
Niña, can result in fluctuations of 5 to 10 millimetres in global sea level
over periods of 6 to 12 months, with larger shifts on individual coastlines.
(Sea levels in the western Pacific, including eastern and northern Australia,
are generally lower during El Niño events and higher during La Niña events).
Nevertheless, it is expected that by 2020 the Australian sea level will,
on average, be 0.06 to 0.19 metres above the 1986–2005 level. The rate of
increase is expected to be faster than that experienced over the 20th century,
due to continued ocean thermal expansion and melting glaciers and ice caps, as
well as the loss of mass from ice sheets, and changes in the mass of water
stored on land.
CSIRO added that whether a low or high emissions pathway is taken is
expected to have only a limited impact on the committed amounts of sea level
rise 'over the next decade or so'. However, CSIRO emphasised that future sea
level rises later in this century will be sensitive to the amount of global
greenhouse emissions. CSIRO submitted:
By 2090, intermediate global emissions (RCP4.5) are likely to
lead to a global sea-level rise of 0.27 to 0.66 m. High global emissions
(RCP8.5) are likely to lead to a rise of 0.38 to 0.89 m. However, a collapse of
the marine‑based sectors of the Antarctic ice sheet could add several
tenths of a metre to sea-level rise late in the century...
It is widely accepted that climate change could result in increased
numbers of coastal properties being damaged or lost due to storm surges,
increased coastal erosion and higher sea levels. The ASBEC submitted that the
impacts of these climate change-related developments 'are being seen already in
many Australian coastal settlements'. Local governments advised that coastal assets are already being affected, and
that the cost to protect, upgrade and repair such assets is expected to
increase with climate change and sea level rise.
The Climate Council of Australia advised that the exposure of coastal
assets to sea level rise 'is very large and the risks are set to increase'. The
Climate Council submitted that, across Australia, more than $226 billion
(2008$) in commercial, industrial, road and rail, and residential assets are
potentially exposed to flooding and erosion hazards at the high-end scenario of
1.1 metres of sea level rise by 2100.
This figure includes 5800 to 8600 commercial buildings, with an estimated
replacement value of $58 billion–$81 billion; 3700 to 6200 light industrial
buildings, with an estimated replacement value $4.2 billion–$6.7 billion; and
27,000 to 35,000 kilometres of roads and rail, with a replacement value of $51
In 2006, it was estimated that approximately 3 per cent of addresses in
Australia are within three kilometres of the shoreline in areas less than five
metres above mean sea level.
The committee received evidence of how sea level rises are expected to
affect individual cities and communities. Examples include:
- Darwin—the Northern Territory Government advised that around 180 residential
buildings in Greater Darwin are estimated to be at risk from a 1.1-metre sea
level rise. In addition, '190 buildings within 110 metres of the high tide
mark...are at risk from erosion'. The Government added that the threat is particularly evident around Darwin
'because Darwin's coastal cliffs are comprised of erodible, soft rock
necessitating continual remediation and reinforcement by local government'.
- Collaroy-Narrabeen Beach—the committee was advised that this
beach is the most vulnerable to erosion from coastal storms in northern Sydney
(and is considered be the third most at risk area from coastal processes in
Australia). The Environment Institute of Australia and New Zealand noted that
in 2016 an estimated $30 million in damage was caused by severe storms that
eroded away about 50 metres of beach and caused extensive property damage.
- City of Lake Macquarie—the local council informed the committee
that a 0.9‑metre increase in relative sea level is expected to result in
the permanent inundation of over 93 hectares of residential zoned land, along
with the loss of public land and facilities.
The National Climate Change Adaptation Research Facility (NCCARF) at
Griffith University has published maps indicating how sea level rise place areas
of Australia potentially at risk of inundation. The maps are indicative only,
and do not take into account storm surge or wave height, nor do they take into
account sea walls, barriers or erosion. Noting the limitations, the maps
provide an accessible means for understanding the potential risks of sea level
rise for particular communities.
The maps for Brisbane and the Gold Coast for 2100 under a low
emissions scenario follow at Figure 2.1 (on page 10) and Figure 2.2 (on page 11).
Changes in temperature and extreme heat events
Along with sea level rises, change in temperature is perhaps the
consequence most readily associated with climate change. The Climate Council
provided the following explanation of how greenhouse gas emissions from human
activities affects temperature and precipitation:
As greenhouse gases increase in the atmosphere, primarily
carbon dioxide from the combustion of fossil fuels (coal, oil and gas), the
climate system is warming because these gases are trapping more heat. The
oceans are also warming, especially at the surface, and this is driving higher
evaporation rates that, in turn, increases the amount of water vapour. In
addition, a warmer atmosphere can hold more water vapour, leading in turn to
more intense rainfall. The 1°C temperature rise that has already occurred,
together with increasing evaporation, has led to an increase of about 7% in the
amount of water vapour in the atmosphere.
CSIRO submitted that Australia's mean land surface air temperature and
surrounding sea surface temperature have both increased by around 1°C since
1910. CSIRO added that:
In recent decades, months warmer than average occur more
often than months colder than average. And since 2001, the number of heat
records in Australia has outnumbered extreme cool records by about 3 to 1 for
daytime maximum temperatures, and about 5 to 1 for night time minimum
Recorded temperature changes by region are depicted at Figure 2.3
(on page 12).
Gold Coast, inundation in year 2100 under low greenhouse gas scenario (RCP4.5)
Note: These maps illustrate a sea-level
rise scenario of 0.54 metres relevant to 2100, derived from CoastAdapt
sea-level rise charts, combined with the nominal highest astronomical tide that
gives an inundation level of 1.96m above mean sea level. Inundation has been
modelled using high-resolution digital elevation data and a simple 'bucket
fill' approach. As noted above, the model does not take account features such
as sea walls. Further information on how the maps have been developed is
available at https://coastadapt.com.au/slr.
NCCARF, 'Sea-level rise and future climate information for coastal councils',
CoastAdapt, https://coastadapt.com.au/slr (accessed 9 January 2018).
Figure 2.3: Annual
mean temperature changes across Australia since 1910
Source: Bureau of
Meteorology; published in CSIRO and Bureau of Meteorology, 'Report at a glance'
in State of the Climate 2016, www.bom.gov.au/state-of-the-climate/index.shtml
(accessed 9 January 2018).
When considering future changes, CSIRO warned that there are two key
uncertainties: future anthropogenic emission trajectories of greenhouse gases
and the response of the Earth's climate system to those emissions.
Notwithstanding this, CSIRO submitted that regional climate projections
indicate that 'mean, daily minimum and daily maximum temperatures will continue
to increase throughout this century for all parts of Australia'. CSIRO
The magnitude of the warming later in the century will depend
on global emissions. By around 2030, Australian annual average temperature is
projected to increase by 0.6-1.3 °C above the climate of 1986-2005 under
intermediate global emissions (RCP4.5), with little difference in warming
between different emission (i.e. RCP) scenarios. The projected temperature
range by 2090 is 0.6 to 1.7 °C for low emissions, 1.4 to 2.7 °C for
intermediate emissions and 2.8 to 5.1 °C for high emissions. Inland areas are
likely to warm more than coastal areas.
A heatwave event is a period of abnormally hot weather that lasts
Overall, the evidence received by the committee during this inquiry
noted that the duration, frequency and intensity of heat events have increased
significantly. For example, CSIRO submitted that attribution studies have
identified that the 2013 and 2014 heatwave events in Australia were influenced
by climate change. Similar evidence was provided in the Climate Council's submission, which
provided the following comments on the trend in extreme heat events:
The incidence of extreme temperatures has increased markedly
over the last 50 years, and heatwaves have become hotter, are lasting longer
and occur more often...Ground-breaking scientific research that tells us how much
influence climate change has on a single heatwave or heat record has shown that
many of the most extreme weather events, such as Australia's record hot year in
2013, were virtually impossible without climate change...The 2016/2017
summer has been described as the "Angry Summer", highlighting the
extraordinary number of weather records broken...This follows the long-term trend
of rising global average temperature since the 1970s, increasing at a rate 170
times faster than the background rate over the past 7,000 years...
Submissions commented on a wide range of projected changes in
Australia's climate and extreme events. On temperature-related changes, CSIRO
explained that projections indicate that heatwaves will 'become more frequent,
hotter, and longer across Australia by the end of the 21st century'. More
frequent and hotter hot days are expected, with the degree of change dependant
on the emissions pathway taken.
Projections for individual cities were provided, such as the following
evidence from CSIRO regarding expected changes in Sydney's climate:
Sydney currently has around 27 days each year where the
maximum temperature exceeds 30°C. By 2090, under intermediate global emissions
of greenhouse gases (RCP4.5), there are likely to be approximately 51 days each
year exceeding 30°C; under high emissions (RCP8.5), this is projected to rise
to 84 days. The average longest run of Sydney days with maximum temperature
exceeding 30°C is currently around four per year. By 2090, under moderate
(RCP4.5) emissions this will rise to around six days and under high
(RCP8.5) emissions, nine days.
CSIRO and the Bureau of Meteorology have undertaken analysis to project
how the number of hot days in Australian capital cities will increase over time
under different emissions pathways. Results of this analysis are at Table 2.1.
Table 2.1: Actual and projected
average number of days per year with the maximum temperature above 35°C for
Australian capital cities
Note: The 1995 figures are averages of observations
for 1981–2010. The 2030 and 2090 figures are from climate model projections
under different RCP scenarios.
CSIRO and Bureau of Meteorology, Climate Change in Australia – Technical
Report, 2015; cited in Climate Council of Australia, Submission 40,
In urban areas, rising temperatures and a greater number of hot days per
year due to climate change could exacerbate the 'urban heat island' effect that city residents already experience. The following evidence received
during a previous inquiry into stormwater management illustrates how heat can
be significantly higher in built areas compared to nearby green areas:
...on an early March morning at break of dawn, the temperature
over Adelaide's city centre was 10 degrees warmer than it was over the
Parklands. That is because of the hard surface, the heat sink and everything
else like that. That relates back to a suburban environment. If you have all
house and hard space—all impervious area—in an urban environment, that one park
at the end of every three or four streets, no matter how well it is manicured
or preserved, is not going to provide that cooling effect. It needs to be done
street by street.
Several submitters commented on the urban heat island effect during this
inquiry. For example, the Northern Territory Government advised that it is
aware that the Darwin central business district 'is consistently hotter than
surrounding areas, largely due to planning outcomes and building designs that
collectively contribute to the creation of a significant heat sink and source
in today's climate'.
The urban heat island effect is discussed further in Chapter 4.
Heatwaves also have implications for the health of building occupants, which is
discussed in Chapter 6.
Submissions commented on fire weather. Since the 1970s, longer fire
seasons across large parts of Australia have been encountered. CSIRO added:
Projected warming and drying in southern and eastern
Australia will lead to fuels that are drier and readier to burn, with increases
in the average forest fire danger index and a greater number of days with
severe fire danger...
It was emphasised, however, that the influence of climate change on the
amount and condition of the fuel needed for bushfires is 'complex'. To
illustrate, the Climate Council noted that 'increases in rainfall may dampen
the bushfire risk in one year by keeping the fuel load wetter, but increase the
risk in subsequent years by enhancing vegetation growth and thus increasing the
fuel load in the longer term'. Notwithstanding the complexity in assessing the
implications of a changing climate for bushfire risk, the Climate Council
observed that 'it is clear...that climate change is driving up the likelihood of
dangerous fire weather'. The Climate Council explained:
At higher temperatures, fuel is 'desiccated' and is more
likely to ignite and to continue to burn...In addition, fires are more likely to
break out on days that are very hot, with low humidity and high winds—that, is
high fire danger weather...Heatwaves are becoming hotter, longer and more
frequent, which is contributing to an increase in dangerous bushfire weather.
Also, over the past several decades in the southeast and southwest of
Australia, there has been a drying trend characterised by declining rainfall
and soil moisture. Contributing to this drying trend is a southward shift of
fronts that bring rain to southern Australia in the cooler months of the
year...In very dry conditions, with relative humidity less than around 20%, fuel
dries out and becomes more flammable...Jolly et al. 2015 and Williamson et al.
2016 highlighted that the combination of droughts and heatwaves contribute
significantly to particularly bad fire seasons in Australia's southeast. A
study into forested regions of Australia found that, in the majority of cases,
years with drought conditions resulted in a greater area of burned land...
The implications of bushfires for infrastructure are already significant
under current conditions. The Climate Council submitted that Deloitte Access
Economics has estimated that bushfires result in annual costs of approximately
$380 million on average. Australia's worst bushfire disaster—the 2009 Black Saturday bushfires in
Victoria—caused the loss of 173 lives and resulted in estimated damage
totalling $4.4 billion.
Victoria has been particularly susceptible to damage from bushfire,
sustaining around 50 per cent of economic damage despite only comprising 3 per
cent of Australia's total landmass.
Like other natural disasters, bushfires can damage a wide range of
infrastructure, including water supplies, roads and bridges, and electricity
infrastructure. The Climate Council provided the following overview of how
bushfires can affect essential infrastructure:
Large-scale, high intensity fires that remove vegetation
expose top soils to erosion and increased runoff after subsequent rainfall...This
can increase sediment and nutrient concentrations in nearby waterways,
potentially making water supplies unfit for human consumption...During the Black
Saturday fires in 2009, 10 billion litres of Melbourne's drinking water were
pumped to safer storage locations because of fears it would be
contaminated...These bushfires affected about 30% of the catchments that supply
Melbourne's drinking water. Melbourne Water estimated the post‑fire
recovery costs, including water monitoring programs, to be more than $2
billion...The 2016 Tasmanian wilderness fire caused more than $130 million in
damages to roads, hydro-electric infrastructure and bridges...
Precipitation, storms, cyclones and flooding
This section examines the implications of climate change for
precipitation and a variety of storm and water-related risks to coastal and
CSIRO advised that rainfall patterns have changed. Examples put forward
by CSIRO include:
- the 19 per cent reduction of May–July rainfall in the
south-western region of Western Australia since 1970;
- reductions in rainfall during April–October (the growing season)
in the continental south-east of Australia;
- increases in rainfall since the 1970s in parts of northern
decreases in average snow depths 'at a number of Australian sites
since the 1950s'.
In their contribution to the joint departmental and agency submission,
the Bureau of Meteorology and the Great Barrier Reef Marine Park Authority (GBRMPA)
explained that 'evidence for significant observed changes in extreme high
rainfall is mostly inconclusive'. Notwithstanding this, it was noted that in
the decades since the 1950s some parts of Australia 'do show a tendency...towards
a higher proportion of rainfall falling from extreme events'.
On future projections for precipitation, the joint submission explained
that climate models 'generally indicate a higher proportion of total rainfall
coming from extreme events, with more extreme rainfall events projected even in
those regions where total rainfall is expected to decrease'. CSIRO provided the following summary of expected precipitation changes based on
information currently available:
In southern Australia, winter and spring rainfall is
projected to decrease, though increases are projected for Tasmania in
winter...The winter decline may be as great as 50 per cent in south-western
Australia under high emissions by 2090. The direction of change in summer and
autumn rainfall in southern Australia is uncertain, but there is medium
confidence in a decrease in south-western Victoria in autumn and in western
Tasmania in summer. There is medium confidence in a winter rainfall decrease
across eastern Australia by 2090. In northern Australia and northern inland
areas, there is low confidence in the direction of future rainfall change by
2090, but substantial changes to wet-season and annual rainfall cannot be
As a result of the projected precipitation changes, southern Australia
is expected to encounter increased time in drought 'with a greater frequency of
severe droughts'. This is related to 'the southward shift of the
fronts from the Southern Ocean that bring rain across southern Australia during
the cool months of the year (winter and spring)'.
Storm surges and tropical cyclones
Storm surges and tropical cyclones attracted significant comment. These can be interlinked,
as storm surges 'accompany tropical cyclones as they make landfall' and 'the most extreme storm surges are normally associated with cyclones'. However, storm surges 'can also be formed by intense low pressure systems in
non‑tropical areas, such as east coast lows in the Tasman Sea'.
In modern Australian history, Tropical Cyclone Tracy, which devastated
Darwin in 1974, is the standout example of the destruction cyclones can cause
in Australia. Sixty-six people died from Cyclone Tracy (53 on land and 13 at
sea) and approximately 35,000 residents (out of a population of 48,000) were
evacuated in its aftermath.
Cyclones that have occurred more recently have also caused significant
damage. The ASBEC noted that Cyclone Yasi (2011) 'was estimated to have caused
over $3.5 billion in damage and lost business in Queensland'. Cyclone Debbie (2017) resulted in estimated insurance losses of over $1.6
Modelling work commissioned by the Northern Australia Insurance Premiums
Taskforce estimated that the long-term future losses from cyclones in northern
Australia are expected to be, on average, around $285 million per year.
It was acknowledged that trends in tropical cyclone frequency and
intensity 'are difficult to discern for the Australian region due to the short
observational records, as well as high year-to-year variability'. Nevertheless, it is projected that tropical cyclones will 'become less frequent
with a greater proportion of high intensity storms (those with stronger winds
and greater rainfall)'. The Climate Council provided the following overview of the implications of
climate change for tropical cyclones:
Climate change is likely to affect tropical cyclone behaviour
in two ways. First, the formation of tropical cyclones most readily occurs when
there are very warm conditions at the ocean surface and when the vertical
gradient is strong. As the climate continues to warm, the difference between
the temperature near the surface of the Earth and the temperature higher up in
the atmosphere, is likely to decrease as the atmosphere continues to warm. As
this vertical gradient weakens, it is likely that fewer tropical cyclones will
form...Second, the increasing temperature of the surface ocean affects the
intensity of cyclones (along with changes in upper atmosphere conditions), both
in terms of maximum wind speeds and in the intensity of rainfall that occurs in
association with the cyclone. This is because the storms draw energy from the
surface waters of the ocean, and as more heat (energy) is stored in these upper
waters, the cyclones have a larger source of energy on which to draw...
As noted in another of the committee's reports on climate change, in the
southern Great Barrier Reef region the incidence of strong tropical cyclones is
projected to increase from one every 25 or more years at present to one every
6–12 years. Between the Pilbara and southern Kimberley regions, the incidence
of strong cyclones is projected to increase from one every 10 years to one
every 7.5 years.
Storm surges were also discussed extensively during this inquiry, with
stakeholders focused on the relationship between storm surges and the sea level
in particular. CSIRO submitted that the rising sea level 'amplifies the effects
of high tides and storm surges'. To illustrate, CSIRO discussed a preliminary assessment of the implications of
sea level rise in southeast Queensland. Two key findings of the assessment are
- Without taking into account an expected population increase, the
number of buildings in the area at risk of inundation from a 1-in-100-year
storm tide could increase from 227,000 at present to 245,100 by 2030 and to
273,000 by 2070. CSIRO noted that the population in the region is expected to
increase to 4 million by 2030, which would compound climate change effects 'if
the population remains at its current pattern of settlement'.
- With an additional 0.2 metre rise in sea level and unchanged
planning and building regulations, by 2030 it is projected that the number of
residential buildings at risk from a storm tide of 2.5 metres will increase
from 35,200 to about 61,500 (and approximately 121,000 residential buildings by
The Climate Council commented:
As the sea level continues to rise, these storm surges are
riding on a higher base sea level and thus becoming more damaging as they are
able to penetrate further inland. Some of the most devastating coastal flooding
events are caused by a "double whammy" of concurrent high sea-level
events and heavy rainfall events in the catchments inland of coastal
settlements. That is, coastal settlements can be inundated by water from both
i) a storm surge, a high tide and a higher sea level, and ii) flooding rivers
from the catchments behind the settlements.
Likewise, the Bureau of Meteorology and the GBRMPA noted that, even if
the severity of storm surges does not change, rising sea levels would result in
increased frequency of flooding from storm surges. This is because 'an increase
in the baseline sea level component will lead to an increase in sea levels at
any specific time even if all other components are constant'.
Given the relationship between cyclones and storm surges, and the
projection regarding the increased intensity of cyclones due to climate change,
it is considered there will be a greater risk of extreme storm surges. In considering the implications of these events, the Australian Local
Government Association (ALGA) emphasised that inland communities can also be
affected by these coastal events. ALGA noted that 'much of the flooding from
Cyclone Debbie was experienced beyond the coastal zone'.
Extreme rainfall events and
The Climate Council of Australia submitted that a 2°C increase in
average temperatures globally 'could result in a 10–30% increase in extreme
It is expected that extreme rainfall events (the wettest day of the year and
the wettest day in 20 years) will increase in intensity in Australia. As noted at paragraph 2.36, it is expected that a higher proportion of
total rainfall will come from extreme events, even in regions where total rainfall
is expected to decrease.
Flooding from heavy rainfall is another area of concern. Flood events
have caused significant damage previously: notable examples include the floods
in 2010–11 in southeast Queensland, Victoria, and Tasmania, which were
calculated to have caused $5.6 billion damage. The Climate Council provided the following summary of the damage caused by the
2010–11 floods in Brisbane and elsewhere in southeast Queensland:
The economic impacts of heavy rainfall can be devastating.
One of the worst flooding events in recent times in Australia as a result of
heavy rainfall was the Queensland 2010/2011 floods. Extreme and extended
rainfall over large areas of Queensland from a strong La Niña event in the
latter part of 2010 led to record breaking and very damaging flooding in
Queensland in December 2010 and January 2011. December 2010 was Queensland's
wettest December on record...Approximately 2.5 million people were affected and
29,000 homes and businesses experienced some form of flooding. The economic
cost of the flooding was estimated to be in excess of $5 billion...with 18,000
homes inundated, damage to 28% of the Queensland rail network and damage to
19,000 km of roads and 3 ports...Around 300,000 homes and businesses lost
power in Brisbane and Ipswich at some stage during the floods...
As noted above, although precipitation levels may decrease in many parts
of the country, the intensity of extreme rain events is projected to increase.
This has particular implications for urban areas, where impervious surfaces and
significant amounts of runoff are typical features of the built environment. As
noted in the committee's 2015 report on stormwater management, future growth in
Australia's urban centres and more frequent extreme weather events due to
climate change may increase volumes of runoff in urban areas that will need to
be absorbed in the environment or managed by stormwater infrastructure, or will
otherwise result in flooding.
The committee received evidence discussing analysis of flood risk in
particular areas. For example, Lake Macquarie City Council submitted there are
around 18,500 properties in its jurisdiction that are subject to lake and
catchment flooding in a 1 per cent flood event. The Council provided the
following evidence of the consequences of this in the face of climate change:
Recent climate change projections for the region indicate
that there will be an increase in the frequency of extreme rainfall events (95th percentile) in summer and autumn. Other projections for the region indicate
that the maximum intensity of extreme rainfall events will increase by up to
20% by 2050 for a 24 hour event and by greater amounts for shorter duration
events in the longer term (2080).
As a consequence, greater numbers of people and
infrastructure will be exposed to the direct impacts of flooding in the future
and communities and systems that are already exposed to flooding will be
exposed more frequently. Within the broader Hunter region, vulnerable groups
including elderly and low socio-economic groups are disproportionately represented
in areas subject to flooding.
Infrastructure within the City that is exposed to flood
hazards includes residential dwellings, public infrastructure including road
and nationally significant transport links, utilities, community facilities,
commercial and industrial areas. Intangible damages associated with flood
hazards include impacts on mental and physical health, disruption of services,
and disruption of economic activity.
Certain types of ecosystems and natural features such as coral reefs, sand dunes,
mangroves and wetlands can help protect Australia's coast from the worst
impacts of extreme weather events. How climate change is affecting coral reefs,
kelp and mangrove forests, and the marine environment generally, were discussed
extensively in the committee's 2017 report on the impacts of climate change on
marine fisheries and biodiversity.
In summary, there is substantial evidence that warming ocean
temperatures and ocean acidification have had significant ecological impacts in
the Great Barrier Reef and in Western Australian reefs, such as coral bleaching
and reductions in coral calcification and reproduction rates. Mangrove and kelp
forest dieback has also occurred, such as the severe dieback of mangroves in
the Gulf of Carpentaria.
From an infrastructure perspective, the health of these natural coastal
defence systems can be significant, particularly during extreme weather events.
As Professor Damien Burrows noted during the committee's marine fisheries and
Mangroves protect the coast by absorbing the energy of
storm-driven waves and wind. The only two yachts undamaged by Cyclone Tracy in
Darwin in 1974 were sheltered in a mangrove creek. In 2006, mangroves protected
vessels and the coastline during Cyclone Larry in far north Queensland.
The damage bill would have been much higher if it wasn't for the existence
of intact mangrove forests.
Need for a strong mitigation response
This report generally focuses on adaptation measures required in
response to climate change. It is important, however, to address the need to
reduce and curb greenhouse gas emissions, including the actions needed to meet
Australia's obligations under the Paris Agreement.
Several submitters emphasised the need for more action to be taken to
address the consequences of human activities for the climate system. The
Investor Group on Climate Change (IGCC) commented:
Ultimately, the best defense against rising costs and the
physical impacts of climate change is to meet the goals of the Paris Agreement
and limit global warming to less than 2°C.
To achieve this, the IGCC argued that Australia needs to be 'working to
facilitate an economically efficient transition to a net zero emissions economy in line with global commitments under the Paris Agreement', including
by managing carbon risk as an economic and financial risk (this is discussed in
Governments and other stakeholders called on the Australian Government
to strengthen its mitigation and adaptation efforts. For example, the
Queensland Government submitted that it:
...strongly advocates for the
Australian Government to strengthen its climate change policy response in terms
of its emissions reduction targets and a credible suite of mechanisms to
achieve these targets, and its efforts in relation to climate adaptation.
The need for a carbon pricing mechanism to change existing economic
models and otherwise support the transition to a low-carbon economy was noted.
Effective mitigation is critical due to the limits on the ability to
adapt. Professor Lesley Hughes from the Climate Council of Australia warned
that although Australia, as a developed country, is adapting to climate change
'reasonably well' at present, the ability to adapt 'even in a country like
Australia, will become a larger and larger challenge'. Professor Hughes
Really, we need to fix the root cause of the problem so that
we don't get a situation to which we simply cannot adapt. It's very clear from
the climate science that we're heading for at least two degrees, probably more.
We are not reducing emissions strongly enough to only get two degrees, so we're
looking at more than two degrees in the second half of this century. The
influence of that on extreme climate events will be massive. There will be many
to which adaptation becomes increasingly unlikely.
Professor Hughes added that the climate system has 'a very big lag
time'. Professor Hughes explained that once 2°C of warming is reached, sea
level rise will continue 'for centuries if not millennia'. The professor
When we get to two degrees, we are probably still in the
range of adapting, but, beyond that, sea level rise is going to keep going up
at least for centuries after that. So it really depends on the timescale at
which you are thinking your infrastructure needs to adapt by. It's like turning
off a tap, but the water keeps running for a few hundred years and you still
have an overflowing bath tub.
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