Editing IPCC:AR6/WGII/Chapter-6 (section)

==== 6.2.4.2 Transport ====

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Since AR5, research has highlighted the implications for disruption to global supply chains (Becker et al., 2018; [[#Shughrue--2018|Shughrue and Seto, 2018]] ; [[#Pató--2015|Pató, 2015]] ), and has made advancements in quantifying costs of climate risks to transportation infrastructure. Climate risks to transport infrastructure (from heat- and cold waves, droughts, wildfires, river and coastal floods, and windstorms) in Europe could rise from €0.5 billion to over €10 billion by the 2080s (Forzieri et al., 2018). Across the Arctic, nearly four million people and 70% of all current infrastructure, including resource extraction and transportation routes, will be at risk by 2050 (Hjort et al., 2018), although the design of specific infrastructure may also affect the degree of infrastructure damage, depending on local geological and ecological conditions. Globally, [[#Koks--2019|Koks et al. (2019)]] calculated that approximately 7.5% of road and railway assets are exposed to a 1-in-100 year flood events, and total global expected annual damages (EAD) of USD 3.1–22 billion (mean USD 14.6 billion) due to direct damage from cyclone winds, surface and river flooding, and coastal flooding. The majority of this is caused by surface water and fluvial flooding (mean USD 10.7 billion). Although twice as much infrastructure is exposed to cyclone winds compared with flooding, a mean EAD of USD 0.5 billion is significantly less than for coastal flooding (USD 2.3 billion), as cyclone damages are largely limited to bridge damage and the cost of removing trees fallen on road carriageways and railway tracks. This is small relative to global gross domestic product (GDP; ~0.02%). However, in some countries EAD equates to 0.5–1% of GDP, which is the same order of magnitude as typical national transport infrastructure budgets, but especially significant for countries such as Fiji that already spend 30% of their government budget on transport (World Bank Group, 2017). [[#Koks--2019|Koks et al. (2019)]] did not assess future climate change impacts, but comparable studies calculating changes in EAD from flooding based upon land use show increases of 170–1370%, depending on global greenhouse gas emissions levels (Alfieri et al., 2017; Winsemius et al., 2015). Moreover, Schweikert et al., (2014) report that climate risks to transport infrastructure could cost as much as 5% of annual road infrastructure budgets by 2100, with disproportionate impacts in some low and lower middle-income countries.

Changes in rainfall and temperature patterns are expected to increase geotechnical failures of embankments and earthworks (Briggs, Loveridge and Glendinning, 2017; Tang et al., 2018; [[#Powrie--2018|Powrie and Smethurst, 2018]] ) from landslides, subsidence, sinkholes, desiccation and freeze-thaw action. For instance, Pk et al. (2018) show this could lead to a 30% reduction in the engineering factor of safety of earth embankments in Southern Ontario (Canada). Increased river flows in many catchments will also increase failures from bridge scours (Forzieri et al., 2018). [[#HR%20Wallingford--2014|HR Wallingford (2014)]] calculate that the projected 8% increase in scouring from high river flows in the UK will lead to 1 in 20 bridges being at high risk of failure by the 2080s, whilst in the USA the 129,000 bridges currently deficient could increase by 100,000 (Wright et al., 2012). With respect to temperature, analysis by [[#Forzieri--2018|Forzieri et al. (2018)]] concludes that heatwaves will be the most significant risk to EU transport infrastructure in the 2080s, as a result of buckling of roads and railways due to thermal expansion, melting of road asphalt and softening of pavement material. In the USA, over 50% more roads will require rehabilitation (Mallick et al., 2018), whilst USD 596 million will be required through 2050 to maintain and repair roads in Malawi, Mozambique and Zambia (Chinowsky, Price and Neumann, 2013).

In addition to direct damages from flooding and heatwaves, disruption caused by road blockages will be increased by more frequent flood events. For example, in the city of Newcastle upon Tyne (UK), road travel disruption across the city from a 1-in-50 year surface water flood event could increase by 66% by the 2080s (Pregnolato et al., 2017), whilst heatwaves could treble railway speed restrictions in parts of the UK (Palin et al., 2013). [[#Knott--2017|Knott et al. (2017)]] highlighted risks to coastal infrastructure where ~30 cm sea level rise sea level rise would also push up groundwater and reduce design life by 5–17% in New Hampshire (USA). Heavy rain and flooding can also inundate underground transport systems (Forero-Ortiz, Martínez-Gomariz and Canas Porcuna, 2020).

Many airports, and by their nature ports, are in the low elevation coastal zone, making them especially vulnerable to flooding and sea level rise. Under a 2 o C scenario, the number of airports at risk of storm surge flooding increases from 269 to 338 or as many as 572 in an RCP8.5 scenario; these airports are disproportionately busy and account for up to 20% of the world’s passenger routes ( [[#Yesudian--2021|Yesudian and Dawson, 2021]] ). Airport and port operations could be disrupted by icing of aircraft wings, vessels, decks, riggings and docks (Doll, Klug and Enei, 2014; Chhetri et al., 2015). Warming will increase microbiological corrosion of steel marine structures (Chaves et al., 2016). Fog, high winds and waves can disrupt port and airport activity, but changes are uncertain and with regional variation (Mosvold [[#Larsen--2015|Larsen, 2015]] ; Izaguirre et al., 2021; [[#Becker--2020|Becker, 2020]] ; León-Mateos et al., 2021; Taszarek, Kendzierski and Pilguj, 2020; Danielson, Zhang and Perrie, 2020; Kawai et al., 2016).

Waterways are still important transport routes for goods in many parts of the world, although they are mostly expected to benefit from reduced closure from ice (Jonkeren et al., 2014; [[#Schweighofer--2014|Schweighofer, 2014]] ), low flows will ''likely'' lead to reduced navigability and increased closures; [[#van%20Slobbe--2016|van Slobbe et al. (2016)]] estimate the Rhine may reach a turning point for waterway transportation between 2070–2095. Obstruction due to debris and fallen vegetation of roads and rails and to inland and marine shipping from high winds are expected to increase (Koks et al., 2019; Kawai et al., 2018; Karagiannis et al., 2019)..

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