Editing IPCC:AR6/SROCC/Chapter-3 (section)

===== 3.4.3.3.4 Infrastructure =====

Permafrost is undergoing rapid change (Section 3.4.1.2), creating challenges for planners, decision makers and engineers (AMAP, 2017d <sup>[[#fn:r1941|1941]]</sup> ). The observed changes in the ground thermal regime (Romanovsky et al., 2010 <sup>[[#fn:r1942|1942]]</sup> ; Romanovsky et al., 2017 <sup>[[#fn:r1943|1943]]</sup> ; Biskaborn et al., 2019 <sup>[[#fn:r1944|1944]]</sup> ) threaten the structural stability and functional capacities of infrastructure, in particular that which is located on ice rich frozen ground. Extensive summaries of construction damages along with adaptation and mitigation strategies are available (Larsen et al., 2014 <sup>[[#fn:r1945|1945]]</sup> ; Dore et al., 2016 <sup>[[#fn:r1946|1946]]</sup> ; AMAP, 2017d <sup>[[#fn:r1947|1947]]</sup> ; Pendakur, 2017 <sup>[[#fn:r1948|1948]]</sup> ; Shiklomanov et al., 2017a <sup>[[#fn:r1949|1949]]</sup> ; Shiklomanov et al., 2017b <sup>[[#fn:r1950|1950]]</sup> ; Vincent et al., 2017 <sup>[[#fn:r1951|1951]]</sup> ).

Projections of climate and permafrost suggest that a wide range current infrastructure will be impacted by changing conditions ( ''medium confidence'' ). A circumpolar study found that approximately 70% of infrastructure (residential, transportation and industrial facilities), including over 1200 settlements (~40 with population more than 5000) are located in areas where permafrost is projected to thaw by 2050 under RCP4.5 (Hjort et al., 2018 <sup>[[#fn:r1952|1952]]</sup> ). Regions associated with the highest hazard are in the thaw-unstable zone characterised by relatively high ground-ice content and thick deposits of frost susceptible sediments (Shiklomanov et al., 2017b <sup>[[#fn:r1953|1953]]</sup> ). By 2050, these high hazard environments contain one-third of existing pan-Arctic infrastructure. Onshore hydrocarbon extraction and transportation in the Russian Arctic are at risk: 45% of the oil and natural gas production fields in the Russian Arctic are located in the highest hazard zone.

In a regional study of the state of Alaska, cumulative expenses projected for climate-related damage to public infrastructure totalled USD 5.5 billion between 2015 and 2099 under RCP8.5 (Melvin et al., 2017 <sup>[[#fn:r1954|1954]]</sup> ). The top two causes of damage related costs were projected to be road flooding from increased precipitation, and building damage associated with near-surface permafrost thaw. These costs decreased by 24% to USD 4.2 billion for the same time frame under RCP4.5, indicating that reducing greenhouse gas emissions globally could lessen damages (Figure 3.13). In a related study that included these costs and others, as well as positive gains from climate change in terms of a reduction in heating costs attributable to warmer winter, annual net costs were still USD 340–700 million, or 0.6–1.3% of Alaska’s GDP, suggesting that climate change costs will outweigh positive benefits, at least for this region (Berman and Schmidt, 2019 <sup>[[#fn:r1955|1955]]</sup> ).

Winter roads (snow covered ground and frozen lakes) are distinct from the infrastructure considered earlier, but have a strong influence on the reliability and costs of transportation in some remote northern communities and industrial development sites (Parlee and Furgal, 2012 <sup>[[#fn:r1956|1956]]</sup> ; Huskey et al., 2014 <sup>[[#fn:r1957|1957]]</sup> ; Overland et al., 2017 <sup>[[#fn:r1958|1958]]</sup> ). For these communities, changing lake and river levels and the period of safe ice cover all affect the duration of use of overland travel routes and inland waterways, with associated implications for increased travel risks, time, and costs (Laidler, 2012 <sup>[[#fn:r1959|1959]]</sup> ; Ford et al., 2013 <sup>[[#fn:r1960|1960]]</sup> ; Goldhar et al., 2014 <sup>[[#fn:r1961|1961]]</sup> ). There have been recent instances of severely curtailed ice road shipping seasons due to unusually warm conditions in the early winter (Sturm et al., 2017 <sup>[[#fn:r1962|1962]]</sup> ). While the impact of human effort on the maintenance of winter roads is difficult to quantify, a reduction in the operational time window due to winter warming is projected (Mullan et al., 2017 <sup>[[#fn:r1963|1963]]</sup> ).

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