finding 26.5 : key-message-26-5

Climate warming is causing damage to infrastructure that will be costly to repair or replace, especially in remote Alaska (very likely, high confidence). It is also reducing heating costs throughout the state (likely, medium confidence). These effects are very likely to grow with continued warming (very likely, high confidence). Timely repair and maintenance of infrastructure can reduce the damages and avoid some of these added costs (likely, high confidence).

This finding is from chapter 26 of Impacts, Risks, and Adaptation in the United States: The Fourth National Climate Assessment, Volume II.

Process for developing key messages:

The Alaska regional chapter was developed through public input via workshops and teleconferences and review of relevant literature, primarily post 2012. Formal and informal technical discussions and narrative development were conducted by the chapter lead and contributing authors via email exchanges, teleconferences, webinars, in-person meetings, and public meetings. The authors considered inputs and comments submitted by the public, the National Academies of Sciences, Engineering, and Medicine, and federal agencies. The author team also engaged in targeted consultations during multiple exchanges with contributing authors, who provided additional expertise on subsets of the Traceable Account associated with each Key Message.

Description of evidence base:

Coastal erosion affects a number of coastal communities, with the highest rates on the Arctic coastline.cf15559b-f1e8-4022-945b-45ab149dc1a8 Coastal erosion and flooding in some cases will require that entire communities, or portions of communities, relocate to safer terrain. The U.S. Army Corps of Engineers identified erosion threats to 31 communities requiring partial or complete relocation.49a37e8f-eef6-4ee6-9705-fac54c48df30 Relocation costs for seven vulnerable communities identified in a 2009 U.S. Government Accountability Office (GAO) study ranged from $80 to $200 million per community.1807de04-16a3-422a-a5bc-d241def97f88

Melting glaciers will increase the role of seasonal precipitation patterns for hydroelectric power generation. River discharge has been increasing during the winter since the 1960s, but because reservoirs are generally full in fall, investments to increase reservoir heights would be required to take advantage of increased fall precipitation.09961450-e217-4cf4-b11f-fab19c8ea9ed

National Weather Service (NWS) daily weather summaries show that heating degree days have already declined by 5% in Sitka, 6% in Fairbanks and Nome, and 8% in Anchorage and Utqiaġvik (formally known as Barrow) as compared to mid-20th century levels. The same NWS data show that increased cooling degree days from warmer summer temperatures provide only a small offset to the beneficial effect of lower heating costs.

New information and remaining uncertainties:

The extent, rate, and patterns of coastal erosion at locations other than along the north coast, and including deltas and rivers, are poorly known. Change in the patterns and trends of erosion (for example, an increase in the rate associated with warming and climate change), is expected but poorly documented for most locations due to the scarcity of historical data.

Future energy prices are highly uncertain, generating a high level of uncertainty around the dollar value of the savings in space heating costs associated with the projected decline in heating degree days.

Wildfire suppression costs depend on future policy decisions for wildfire management. Property damage from wildfire depends on uncertain future settlement and development patterns.

Assessment of confidence based on evidence:

There is high confidence and it is very likely that future damage to infrastructure from thawing permafrost and coastal erosion will cost hundreds of millions of dollars annually to repair or replace. There is high confidence and it is likely that timely repair and maintenance of infrastructure can reduce damages and avoid some of the added costs. There is medium confidence and it is very likely that these costs will be offset in part by savings from reduced space heating needs.

This finding was derived from scenario rcp_4_5
This finding was derived from scenario rcp_8_5

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