Editing IPCC:AR6/WGII/Chapter-11 (section)

==== 11.3.5.2 Projected Impacts ====

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Changes in heat waves, droughts, fire weather, heavy rainfall, storms and sea level rise (SLR) are projected to increase negative impacts for cities, settlements and infrastructure ( ''high confidence'' ) (Table 11.3a, Table 11.3b; Box 11.1, Box 11.3, Box 11.4).

Increased floods, coastal inundation (assuming a sea level rise (SLR) of 1.6 m by 2100), wildfires, windstorms and heatwaves may cause property damage in Australia estimated at AUD$91 billion per year by 2050 and AUD$117 billion per year by 2100 for RCP8.5, while damage-related loss of property value is estimated at AUD$611 billion by 2050 and AUD$770 billion by 2100 for RCP8.5 ( [[#Steffen--2019|Steffen et al., 2019]] ). For a 1.0-m sea level rise (SLR), the value of exposed assets in New Zealand would be NZD$25.5 billion (Box 11.6). For a 1.1-m sea level rise (SLR), the value of exposed assets in Australia would be AUD$164–226 billion (Box 11.6). These exposure estimates exclude impacts on personal livelihood, well-being and lifestyle.

Extreme heat risks are projected to exacerbate existing heat-related impacts on human health, vegetation and infrastructure ( [[#Tapper--2014|Tapper et al., 2014]] ; [[#Tapper--2021|Tapper, 2021]] ) (11.3.6). In Australia, the annual frequency of days over 35°C is projected to increase 20–70% by 2030 (RCP4.5), and 25–85% (RCP2.6) to 80–350% (RCP8.5) by 2090 (Table 11.3a). For example, Perth may average 36 d over 35°C by 2030 (RCP4.5). In New Zealand, the annual frequency of days over 25°C may increase 20–60% (RCP2.6) to 50–100% (RCP8.5) by 2040 and 20–60% (RCP2.6) to 130–350% (RCP8.5) by 2090 (Table 11.3b). For example, Auckland may average 39 d over 25°C by 2040 (RCP8.5). Unprecedented extreme temperatures, as high as 50°C in Sydney or Melbourne, could occur with global warming of 2.0°C ( [[#Lewis--2017|Lewis et al., 2017]] ). Heat-related costs for Melbourne during 2012–2051 are estimated at AUD$1.9 billion, of which AUD$1.6 billion is human health/mortality costs ( [[#AECOM--2012|AECOM, 2012]] ). Extreme heat is threatening liveability in some rural areas in Australia ( [[#Turton--2017|Turton, 2017]] ), particularly given their reliance on outside physical work and older populations.

Key infrastructure and services face major challenges. Structural metal corrosion rates are projected to increase significantly at coastal locations but decrease inland ( [[#Trivedi--2014|Trivedi et al., 2014]] ). A drier climate may decrease the rate of deterioration of road pavements, but extreme rainfall events and heat pose a significant risk ( [[#Taylor--2015|Taylor and Philp, 2015]] ), especially to unsealed roads in northern Australia ( [[#CoA--2015|CoA, 2015]] ). Critical infrastructure on coasts is at risk from sea level rise (SLR) and storm surges (Box 11.6). Facilities such as hospitals face weather-related hazards exacerbated by climate change and not originally anticipated in building and infrastructure design ( [[#Loosemore--2011|Loosemore et al., 2011]] ; [[#Loosemore--2014|Loosemore et al., 2014]] ). By 2050, increased risks are projected for the availability and quality of potable water supplies, delivery of wastewater and stormwater services to communities, transport systems, electricity infrastructure, operating municipal landfills and contaminated sites located near rivers and the coast ( [[#Gilpin--2020|Gilpin et al., 2020]] ; [[#MfE--2020a|MfE, 2020a]] ; [[#Hughes--2021|Hughes et al., 2021]] ). These then create risks to social cohesion and community well-being from displacement of individuals, families and communities, with inequitable outcomes for vulnerable groups ( [[#Boston--2018|Boston and Lawrence, 2018]] ).

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