PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES
Significance
Climate change in Alaska is causing widespread environmental change that is damaging critical infrastructure. As climate change continues, infrastructure may become more vulnerable to damage, increasing risks to residents and resulting in large economic impacts. We quantified the potential economic damages to Alaska public infrastructure resulting from climate-driven changes in flooding, precipitation, near-surface permafrost thaw, and freeze–thaw cycles using high and low future climate scenarios. Additionally, we estimated coastal erosion losses for villages known to be at risk. Our findings suggest that the largest climate damages will result from flooding of roads followed by substantial near-surface permafrost thaw-related damage to buildings. Proactive adaptation efforts as well as global action to reduce greenhouse gas emissions could considerably reduce these damages.
Abstract
Climate change in the circumpolar region is causing dramatic environmental change that is increasing the vulnerability of infrastructure. We quantified the economic impacts of climate change on Alaska public infrastructure under relatively high and low climate forcing scenarios [representative concentration pathway 8.5 (RCP8.5) and RCP4.5] using an infrastructure model modified to account for unique climate impacts at northern latitudes, including near-surface permafrost thaw. Additionally, we evaluated how proactive adaptation influenced economic impacts on select infrastructure types and developed first-order estimates of potential land losses associated with coastal erosion and lengthening of the coastal ice-free season for 12 communities. Cumulative estimated expenses from climate-related damage to infrastructure without adaptation measures (hereafter damages) from 2015 to 2099 totaled $5.5 billion (2015 dollars, 3% discount) for RCP8.5 and $4.2 billion for RCP4.5, suggesting that reducing greenhouse gas emissions could lessen damages by $1.3 billion this century. The distribution of damages varied across the state, with the largest damages projected for the interior and south-central Alaska. The largest source of damages was road flooding caused by increased precipitation followed by damages to buildings associated with near-surface permafrost thaw. Smaller damages were observed for airports, railroads, and pipelines. Proactive adaptation reduced total projected cumulative expenditures to $2.9 billion for RCP8.5 and $2.3 billion for RCP4.5. For road flooding, adaptation provided an annual savings of 80–100% across four study eras. For nearly all infrastructure types and time periods evaluated, damages and adaptation costs were larger for RCP8.5 than RCP4.5. Estimated coastal erosion losses were also larger for RCP8.5.
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Climate change at high latitudes is causing rapid and unprecedented environmental change. The rate of temperature rise across the Arctic has been twice the global average in recent decades (1–3). Sea and land ice has diminished (4, 5), and increased coastal erosion (6, 7), permafrost thaw (8–10), and wildfire activity (11–14) have been observed. Models project that these changes will continue (15–17) and that the corresponding societal impacts will be greater (18) without substantial near-term global reductions in greenhouse gas (GHG) emissions. In the state of Alaska and across the broader circumpolar north, these changes are exacerbating existing challenges and introducing new risks for communities, including increased damage to critical infrastructure (19–21).
Climate change increases the vulnerability of infrastructure by enhancing environmental stressors, thereby creating additional strains on structures beyond what is expected from normal conditions and use. Risks to infrastructure associated with climate change in the Arctic have been studied previously for some environmental stressors. Increased near-surface permafrost thaw associated with climate warming has been widely recognized as a cause of increased infrastructure damage (22–25). This climate-driven thaw can occur concurrent with thaw induced by natural disturbances, such as wildfire (26, 27), and human activities (20, 23, 27, 28), including the construction of infrastructure. Permafrost thaw and subsequent ground subsidence, particularly where permafrost is ice-rich, negatively impact buildings, roads, railroads, pipelines, and oil and gas infrastructure (19, 20, 24, 29). In Alaska, Hong et al. (25) found the greatest near-term risks of thaw settlement in relatively warm permafrost found in the discontinuous permafrost zone in the interior and longer-term risks in the continuous permafrost zone in the northern part of the state (Fig. 1 shows a map of permafrost distribution). Warmer temperatures can also alter the frequency of freeze–thaw cycles (FTCs), impacting foundation and underground infrastructure stability and vulnerability (30, 31). Extensive erosion influenced by sea ice loss, permafrost thaw, and inland flooding (7, 32) threatens numerous coastal and riverine communities in Alaska and affects most infrastructure types (33). As climate change continues, the extent of infrastructure damage as well as the costs to maintain, replace, and adapt the built environment are expected to increase.
Few studies have moved beyond observation and risk evaluation to quantify the potential economic impacts of climate change on Alaska public infrastructure. Climate change-related increases in costs have been estimated at about $50 million (original values converted to 2015 dollars using the Consumer Price Index) annually (34) for a subset of stressors affecting roads and the electricity sector, whereas Larsen et al. (35) estimated approximately $7.3–14.5 billion (from 2006 to 2080; values converted to 2015 dollars using the Consumer Price Index) above “normal” operations and maintenance resulting from permafrost thaw, flooding, and coastal erosion impacts on a wide range of infrastructure types. In recent years, the analysis by Larsen et al. (35) has served as a guide for considering damage to infrastructure in Alaska and the broader Arctic under different climate futures. Although this study has provided valuable insights, the authors noted that estimates could be improved considerably with a more comprehensive inventory of public infrastructure and the use of nonlinear damage functions that better capture relationships among environmental stressors, infrastructure lifespan, and the associated incremental change in capital and operation and maintenance costs (35, 36).
We addressed the recommendations made by Larsen et al. (35) and developed new estimates of potential economic impacts of climate change to Alaska’s public road, building, airport, rail, and pipeline infrastructure. Using high and low climate forcing scenarios [representative concentration pathway 8.5 (RCP8.5) and RCP4.5, respectively, from the Coupled Model Inter-comparison Project Phase 5 (CMIP5)] (37) for five general circulation models (GCMs), we evaluated the climate-related change in incurred costs (hereafter damages) required to maintain infrastructure. We estimated the benefits (or avoided damages) to infrastructure of global reductions in GHG emissions and identified where proactive adaptation measures may reduce climate change-related expenses. Climate model projections were incorporated into a reconfigured version of the Infrastructure Planning Support System (IPSS) software tool (38–40) that accounts for climate change impacts unique to northern latitudes, including near-surface permafrost thaw and extreme freeze–thaw dynamics. This model also considers damages from precipitation and precipitation-caused flooding. Independently, we developed an approach to generate first-order estimates of projected coastal erosion rates and evaluated how GHG mitigation may influence erosion in 12 coastal communities where immediate actions to manage erosion or relocate have been recommended (33). This study is one component of a broader multi-sector modeling framework developed for the Environmental Protection Agency Climate Change Impacts and Risk Analysis Project (41, 42), which seeks to quantify the avoided or reduced impacts of climate change resulting from GHG mitigation and adaptation.
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Tags: AK, Alaska, Climate, Erosion, Global Warming, National Academy of Sciences, Permafrost, PNAS, Proceedings of the National Academy of Sciences
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