Increased extreme weather events

2016

Population trends, urbanisation and residential shifts to high-risk areas will intersect with climate change to increase Australia’s exposure to natural hazards (Australian Government 2015b).

In recent years, heatwaves, floods, fires and storms have occurred more frequently in many cities. Projected numbers of the average number of days per year with maximum temperature above 35 °C are given for the future Representative Concentration Pathways (RCPs) included in Table BLT5.4

In 2030 under RCP4.5, the number of days above 35 °C increases considerably, particularly in the northern centres and at some inland sites with greater warming (e.g. Canberra airport). The increases for the other scenarios are similar in this period (not shown). By 2090, the number of days above 35 °C shows a moderate increase for some cities under the RCP2.6 scenario, and numbers increase significantly for most cities under the other 2 scenarios (CSIRO & BoM 2015).

For example, in Perth, the number of days above 35 °C by 2090 is 50 per cent greater than in the period centred on 1995 under RCP4.5. The number of days above 35 °C in Adelaide also increases by about 50 per cent by 2090, whereas the number of days above 40 °C more than doubles (not shown).

Maximum temperatures of more than 40 °C also occur in most years at most sites by 2090, and could become normal for a summer day in Alice Springs and Wilcannia (not shown) (CSIRO & BoM 2015).

Table BLT5 Average number of days per year with maximum temperature above 35 °C, various locations, various emissions scenarios

City

1995

2030 RCP4.5

2090 RCP2.6

2090 RCP4.5

2090 RCP8.5

Adelaide

20.0

26.0

28.0

32.0

47.0

Alice Springs

94.0

113.0

119.0

133.0

168.0

Amberley

12.0

18.0

18.0

27.0

55.0

Broome

56.0

87.0

95.0

133.0

231.0

Cairns

3.0

5.5

5.5

11.0

48.0

Canberra

7.1

12.0

13.0

17.0

29.0

Darwin

11.0

43.0

52.0

111.0

265.0

Dubbo

22.0

31.0

34.0

44.0

65.0

Hobart

1.6

2.0

2.0

2.6

4.2

Melbourne

11.0

13.0

14.0

16.0

24.0

Mildura

33.0

42.0

44.0

52.0

73.0

Perth

28.0

36.0

37.0

43.0

63.0

St George

40.0

54.0

58.0

70.0

101.0

Sydney

3.1

4.3

4.5

6.0

11.0

Wilcannia

47.0

57.0

60.0

67.0

87.0

Note: The table shows 2030 under Representative Concentration Pathway (RCP) 4.5, and 2090 under RCP2.6, RCP4.5 and RCP8.5, based on model changes for 2020–39 and 2080–99 relative to 1986–2005.

Source: CSIRO & BoM (2015)

Increases in temperatures associated with climate change will have an impact on human wellbeing and urban livability.

Major heatwaves are Australia’s deadliest natural hazard, particularly for cities. Major heatwaves have caused more deaths since 1890 than bushfires, cyclones, earthquakes, floods and severe storms combined (DITMCU 2013; Table BLT6).

Table BLT6 Estimated numbers of deaths from natural disasters and epidemics in Australia, 1890–2013

Event

Bushfire and urban fire

Cyclone

Earthquake

Epidemic

Flood

Hail, severe storm, tornado

Heatwave

Events with fatalities

75

37

1

11

66

69

29

Deaths

843

935

13

10,375

453

124

2,887

Source: DITMCU (2013)

Based on current trends, heat-related deaths in Australian cities are predicted to increase, with Perth predicted to be most severely affected (Figure BLT16). Heat events are getting worse, but the built environment is not adapting. For example, higher overnight temperatures reduce buildings’ opportunity to cool down.

In addition, the National Climate Change Adaptation Research Facility has published research on the vulnerability of low-income households to heat in various capital cities. It found connections between parts of the outer urban areas of these cities, and lower wealth and exposure to excess heat (Barnett et al. 2013).

A dataset of observed fire weather in Australia at 38 sites from 1973 to 2010 was analysed using the Forest Fire Danger Index (FFDI). Analysis showed an increase in high FFDI values (90th percentile) from 1973 to 2010 at all 38 sites, with a statistically significant increase at 24 sites, indicating that extreme fire weather days have become more frequent over time (Clarke et al. 2013).

Projected warming and drying in southern and eastern Australia will lead to fuels that are drier and more ready to burn, with increases in the average FFDI and the number of days with severe fire danger (high confidence). There is medium confidence that there will be little change in fire frequency in tropical and monsoonal northern Australia.

Extreme rainfall events (wettest day of the year and wettest day in 20 years) are projected to increase in intensity, with high confidence. Confidence is reduced to medium for south-western Western Australia.

Tropical cyclones are projected to become less frequent, with a greater proportion of high-intensity storms (stronger winds and greater rainfall) (medium confidence). A greater proportion of storms may reach south of 25°S (low confidence). In winter, mid-latitude weather systems are projected to shift south, and the westerlies are projected to strengthen (high confidence).

Between 2000 and 2012, insured losses from natural disasters reached $16.1 billion, an average of more than $1.2 billion per year. These events caused immediate and significant damage to infrastructure assets, and lowered productivity and output. The damage to public infrastructure from the 2011 Queensland floods alone was estimated at $5–6 billion (Infrastructure Australia 2015).

Coleman S (2016). Built environment: Increased extreme weather events. In: Australia state of the environment 2016, Australian Government Department of the Environment and Energy, Canberra, https://soe.environment.gov.au/theme/built-environment/topic/2016/increased-extreme-weather-events, DOI 10.4226/94/58b65a5037ed8