There is very high confidence that frontline communities are the first to be affected by the impacts of climate change. Due to their enhanced sensitivity to changing conditions, direct reliance on natural resources, place-based limits, and lack of financial and political capital, it is very likely that they will face the biggest climate challenges in the region. However, there is a significant amount of uncertainty in how individuals and individual communities will respond to these changing conditions, and responses will likely differ between states, communities, and even neighborhoods. Thus, it is the complex interaction between the climate exposures and the integrated social-ecological systems as well as the surrounding policy and response environment that will ultimately determine the challenges these communities face.
' evidence: "Multiple lines of research have shown that the impacts of extreme weather events and climate change depend not only on the climate exposures but also on the sensitivity and adaptive capacity of the communities being exposed to those changes.{{< tbib '187' 'b1577125-f789-49e6-9656-c40ed932184a' >}},{{
There are multiple lines of evidence that demonstrate that tribes and Indigenous peoples are particularly vulnerable to climate change. Climate stressors, such as sea level rise, ocean acidification, warmer ocean and stream temperatures, wildfires, or droughts, are projected to disproportionately affect tribal and Indigenous well-being and health,{{< tbib '106' '41bc14ce-5dbf-4eb4-90e2-0689a2bc3565' >}},{{
There is limited research on how climate change is projected to impact farmworkers, yet evidence suggests that occupational health concerns, including heat-related concerns{{< tbib '210' '63fe78ee-2eb9-445b-bbb7-e3f72f3993e0' >}},{{
Particularly relevant to economically disadvantaged urban populations, extensive work has been done evaluating and analyzing social vulnerability{{< tbib '211' '796c4617-7dcd-433e-bb0e-805cdab4c136' >}} and applying that work to the Northwest.{{< tbib '195' 'c6bc7876-ad40-4d51-83e5-49816363385c' >}} There has also been work completed considering both relative social vulnerability and environmental health data (see WSDOH 2018{{< tbib '162' 'f1ca2352-7158-4312-9c4b-3d1189c1ad10' >}}).
Strong evidence through reports and case studies demonstrates that tribes are active in increasing their resilience through climate change vulnerability assessments and adaptation plans (see https://www.indianaffairs.gov/WhoWeAre/BIA/climatechange/Resources/Tribes/index.htm and http://tribalclimateguide.uoregon.edu/adaptation-plans for a list of tribal and Indigenous climate resilience programs, reports, and actions) and through regional networks (for example, Pacific Northwest Tribal Climate Change Network, Affiliated Tribes of Northwest Indians, Northwest Indian Fisheries Commission, Columbia River Inter-Tribal Fish Commission, Point No Point Treaty Council, Upper Snake River Tribes Foundation).
There are also many community organizations across the region focusing on engaging, involving, and empowering frontline communities, including communities of color, immigrants, tribes and Indigenous peoples, and others to design plans and policies that are meaningful (for example, Front and Centered, Got Green, Puget Sound Sage, Coalition of Communities of Color).
" href: https://data.globalchange.gov/report/nca4/chapter/northwest/finding/key-message-24-5.yaml identifier: key-message-24-5 ordinal: 5 process: "This assessment focuses on different aspects of the interaction between humans, the natural environment, and climate change, including reliance on natural resources for livelihoods, the less tangible values of nature, the built environment, health, and frontline communities. Therefore, the author team required a depth and breadth of expertise that went beyond climate change science and included social science, economics, health, tribes and Indigenous people, frontline communities, and climate adaptation, as well as expertise in agriculture, forestry, hydrology, coastal and ocean dynamics, and ecology. Prospective authors were nominated by their respective agencies, universities, organizations, or peers. All prospective authors were interviewed with respect to the qualifications, and selected authors committed to remain part of the team for the duration of chapter development.
The chapter was developed through technical discussions of relevant evidence and expert deliberation by the report authors at workshops, weekly teleconferences, and email exchanges. The author team, along with the U.S. Global Change Research Program (USGCRP), also held stakeholder meetings in Portland and Boise to solicit input and receive feedback on the outline and draft content under consideration. A series of breakout groups during the stakeholder meetings provided invaluable feedback that is directly reflected in how the Key Messages were shaped with respect to Northwest values and the intersection between humans, the natural environment, and climate change. The authors also considered inputs and comments submitted by the public, interested stakeholders, the National Academies of Sciences, Engineering, and Medicine, and federal agencies. For additional information on the overall report process, see Appendix 1: Process. The author team also engaged in targeted consultations during multiple exchanges with contributing authors for other chapters, who provided additional expertise on subsets of the Traceable Accounts associated with each Key Message.
The climate change projections and scenarios used in this assessment have been widely examined and presented elsewhere{{< tbib '11' '07aed96a-e0e8-47dd-81d3-cdff5a6e261c' >}},{{
Communities on the front lines of climate change experience the first, and often the worst, effects. Frontline communities in the Northwest include tribes and Indigenous peoples, those most dependent on natural resources for their livelihoods, and the economically disadvantaged (very high confidence). These communities generally prioritize basic needs, such as shelter, food, and transportation (high confidence); frequently lack economic and political capital; and have fewer resources to prepare for and cope with climate disruptions (very likely, very high confidence). The social and cultural cohesion inherent in many of these communities provides a foundation for building community capacity and increasing resilience (likely, medium confidence).
' uncertainties: "Actual climate change related vulnerabilities will vary by community and neighborhood.{{< tbib '187' 'b1577125-f789-49e6-9656-c40ed932184a' >}},{{
The secondary and tertiary impacts of changing climate conditions are less well understood. For example, climate change may increase the amount and frequency of pesticides used, and the variety of products used to manage crop diseases, pests, and competing weeds.{{< tbib '328' 'c0419502-0517-447b-886f-ece5ec4cda6c' >}} This is likely to increase farmworker exposure to pesticides and ultimately affect their health and well-being. Further, it is unclear how the altered timing of agricultural management of key crops across the United States (for example, the timing of cherry picking) due to increased temperatures and altered growing seasons may influence the demand for farmworker labor, particularly migrant labor, and how this might impact their livelihoods and occupational health.
There is emerging evidence that there are overlaps between environmental justice concerns and climate change impacts on these communities,{{< tbib '233' 'e5aac477-6382-425b-9610-4a288438cd25' >}},{{
No systematic catalogue of the actions and efforts of frontline communities in the region to address their climate-related challenges exists. Thus, at this point, most examples of adaptation and climate preparedness are anecdotal, but these examples suggest an increasing trend to link adaptation efforts that simultaneously address both climate and equity concerns. However, this approach is still used sporadically based on the interests, needs, and resources of the communities.
" uri: /report/nca4/chapter/northwest/finding/key-message-24-5 url: ~ - chapter_identifier: southwest confidence: "The very high confidence in historical droughts derives from the detection and attribution analyses of temperature increases, snow decreases, and soil moisture decreases that have documented hydrologic droughts in California and the Colorado River Basin due to anthropogenic climate change and the conclusions of the Climate Science Special Report (CSSR), Volume I of the Fourth National Climate Assessment.{{< tbib '74' 'a29b612b-8c28-4c93-9c18-19314babce89' >}} The very high confidence in drought projections derives from the multitude of analyses projecting drought in the Southwest under a range of emissions scenarios and the conclusions of the CSSR.{{< tbib '74' 'a29b612b-8c28-4c93-9c18-19314babce89' >}} Only medium confidence is found for flood projections due to lack of consensus in the model projections of precipitation. Increasingly arid conditions and the potential for increased water use by people lead to an assessment of high confidence in the need for new ways to address increasing risks of water scarcity. The actual frequency and duration of water supply disruptions will depend on the preparation of water resource managers with drought and flood plans, the flexibility of water resource managers to implement or change those plans in response to altered circumstances,{{< tbib '481' 'da714e9f-808c-4aae-8d24-aef041988322' >}} the availability of funding to make infrastructure more resilient, and the magnitude and frequency of climate extremes.
" evidence: "Research has found that hotter temperatures can make hydrologic droughts more severe. The unprecedented droughts in the Colorado River Basin and California showed that increased temperatures from climate change intensified the severity of the drought.{{< tbib '13' 'a42c4f5e-f16b-4196-af05-61f117e0491d' >}},{{
The authors examined the scientific literature in their areas of expertise. The team placed the highest weight on scientific articles published in refereed peer-reviewed journals. Other sources included published books, government technical reports, and, for data, government websites. The U.S. Global Change Research Program issued a public call for technical input and provided the authors with the submissions. The University of Arizona Center for Climate Adaptation Science and Solutions organized the Southwest Regional Stakeholder Engagement Workshop on January 28, 2017, with over 70 participants at the main location in Tucson, AZ, and dozens of participants in Albuquerque, NM, Boulder, CO, Davis, CA, Los Angeles, CA, Reno, NV, and Salt Lake City, UT, all connected by video. Participants included scientists and managers. The author team met the following day for their only meeting in person. Subsequently, authors held discussions in regular teleconferences. Many chapter authors met at the all-author meeting March 26–28, 2018, in Bethesda, MD.
' report_identifier: nca4 statement: 'Water for people and nature in the Southwest has declined during droughts, due in part to human-caused climate change (very high confidence). Intensifying droughts (very high confidence) and occasional large floods (medium confidence), combined with critical water demands from a growing population, deteriorating infrastructure, and groundwater depletion, suggest the need for flexible water management techniques that address changing risks over time (high confidence), balancing declining supplies with greater demands.
' uncertainties: "Projecting future streamflow and hydrologic characteristics in a basin contains many uncertainties. These differences arise because of uncertainty in temperature and precipitation projections due to differences among global climate models (GCMs), uncertainty in regional downscaling, uncertainty in hydrological modeling, and differences in emissions, aerosols, and other forcing factors. Another important uncertainty is differences in the hemispheric and regional-scale atmospheric circulation patterns produced by different GCMs, which generate different levels of snow loss in different model simulations. A key uncertainty is the wide range in projections of future precipitation across the Southwest;{{< tbib '105' '9d8a98fa-0338-486a-b902-cd02d43cae87' >}} some projections of higher-than-average precipitation in the northern parts of the Southwest could roughly offset declines in warm-season runoff associated with warming.{{< tbib '105' '9d8a98fa-0338-486a-b902-cd02d43cae87' >}}
Detection is the finding of statistically significant changes different from natural cycles. Attribution is the analysis of the relative contribution of different causes and whether greenhouse gas emissions from human sources outweigh other factors. Attribution of extreme events, such as the recent California drought to climate change, is an area of emerging science. On the one hand, Seager et al. (2015){{< tbib '58' '4ca5a43c-5fbe-4cb0-8a7d-7ee3acafd7c0' >}} concluded that the California drought was primarily driven by natural precipitation variability. Sea surface temperature anomalies helped set up the high-pressure ridge over California that blocked moisture from moving inland. On the other hand, Diffenbaugh et al. (2015),{{< tbib '56' '89e08a41-6091-45fa-a92e-6168a90a8151' >}} Williams et al. (2015),{{< tbib '14' 'ba57f86f-c42f-4bba-83f6-676d6875c176' >}} and Berg and Hall (2017){{< tbib '55' '2d7d840f-37b6-4484-ba59-aa2d537a8c7c' >}} concluded that high temperatures from climate change drove record-setting surface soil moisture deficits that made the drought more severe than it would have been without climate change. Storage of increased precipitation in soils may partially offset increased evaporation, possibly making drought less likely.{{< tbib '480' '4fbaaa13-99d2-43df-93db-2be546f18892' >}}
In addition to the uncertainties in regional climate and hydrology projections and attribution studies, other uncertainties include potential changes in water management strategies and responses to accommodate the new changing baseline. Additionally, external uncertainties can impact water use in the region via legal, economic, and institutional options for augmenting existing supplies, adding underground storage and recovery infrastructure, and fostering further water conservation, changes in unresolved water rights, and changes to local, state, tribal, regional and national policies related to the balance of agricultural, ecosystem, and urban water use.
" uri: /report/nca4/chapter/southwest/finding/key-message-25-1 url: ~ - chapter_identifier: southwest confidence: 'Field evidence provides high confidence that human-caused climate change has increased wildfire, tree death, and species range shifts. Projections consistently indicate that continued climate change under higher emissions could increase the future vulnerability of ecosystems, but that reducing emissions and increasing fire management would reduce the vulnerability, providing high confidence in positive benefits of these actions.
' evidence: "Scientific research in the Southwest has provided many cases of detection and attribution of historical climate change impacts. Detection is the finding of statistically significant changes different from natural cycles. Attribution is the analysis of the relative contribution of different causes and whether greenhouse gas emissions from human sources outweigh other factors. Published field research has detected ecological changes in the Southwest and attributed much of the causes of the changes to climate change. Wildfire across the western United States doubled from 1984 to 2015, compared to what would have burned without climate change, based on analyses of eight fuel aridity metrics calculated from observed data, historical observed temperature, and historical modeled temperature from global climate models.{{< tbib '7' 'de4a77df-03ba-4319-a13f-7fdefbb353a5' >}} The increased heat has intensified droughts in the Southwest,{{< tbib '13' 'a42c4f5e-f16b-4196-af05-61f117e0491d' >}},{{
Cutting emissions through energy conservation and renewable energy can reduce ecological vulnerabilities. Under high emissions, projected climate change could triple burned area in the Sierra Nevada, but under low emissions, fire could increase just slightly.{{< tbib '173' '8dfecf8b-f8a8-4f03-8d68-551b13794a1d' >}} Projections of biome shifts{{< tbib '213' '37982de0-0e01-476f-b522-b8162d709134' >}},{{
The authors examined the scientific literature in their areas of expertise. The team placed the highest weight on scientific articles published in refereed peer-reviewed journals. Other sources included published books, government technical reports, and, for data, government websites. The U.S. Global Change Research Program issued a public call for technical input and provided the authors with the submissions. The University of Arizona Center for Climate Adaptation Science and Solutions organized the Southwest Regional Stakeholder Engagement Workshop on January 28, 2017, with over 70 participants at the main location in Tucson, AZ, and dozens of participants in Albuquerque, NM, Boulder, CO, Davis, CA, Los Angeles, CA, Reno, NV, and Salt Lake City, UT, all connected by video. Participants included scientists and managers. The author team met the following day for their only meeting in person. Subsequently, authors held discussions in regular teleconferences. Many chapter authors met at the all-author meeting March 26–28, 2018, in Bethesda, MD.
' report_identifier: nca4 statement: 'The integrity of Southwest forests and other ecosystems and their ability to provide natural habitat, clean water, and economic livelihoods have declined as a result of recent droughts and wildfire due in part to human-caused climate change (high confidence). Greenhouse gas emissions reductions, fire management, and other actions can help reduce future vulnerabilities of ecosystems and human well-being (high confidence).
' uncertainties: "Because climate model projections often diverge on whether precipitation may increase or decrease, two broad types of fire futures{{< tbib '152' '391560e0-40c1-4f9d-b063-e87d18c87e02' >}} could be 1) dry-fire future—hotter and drier climate, increased fire frequency, fire limited by vegetation, potential biome change of forest to grassland after a fire due to low natural regeneration, and high carbon emissions; or 2) intense-fire future—hotter and wetter climate, more vegetation, increased fire frequency and intensity, fire limited by climate, and higher carbon emissions. These two broad categories each encompass a range of fire conditions. On the ground, gradients of temperature, precipitation, and climate water deficit (difference between precipitation and actual evapotranspiration) generate gradients of fire regimes. Because climate change, vegetation, and ignitions vary across the landscape, potential fire frequency shows high spatial variability. Therefore, future fire types could appear in patches across the landscape, with different fire future types manifesting themselves in adjacent forest patches. Changes in aridity may shift some plant and animal species ranges downslope to favorable combinations of available moisture and suitable temperature, rather than upslope.{{< tbib '484' '9743c446-fef0-44f4-82bd-7f2ff1614205' >}} Plants and animals may respond to changing climate, and have been shown to do so, through range shifts, phenology shifts, biological evolution, or local extirpation. Thus, no single expected response pattern exists.{{< tbib '224' '820ced23-71ae-4607-8353-74e3881db2a1' >}}
" uri: /report/nca4/chapter/southwest/finding/key-message-25-2 url: ~ - chapter_identifier: southwest confidence: 'Field measurements at numerous locations have detected sea level rise, ocean warming, ocean acidification, and ocean hypoxia. Multiple model-based analyses have attributed these changes to human-caused climate change, giving high confidence to these impacts of climate change.
' evidence: "At the Golden Gate Bridge, San Francisco, sea level rose 9 ± 0.4 inches (22 ± 1 cm) from 1854 to 2016,{{< tbib '236' '8e1ab38d-5d31-4a6a-8ad6-e06fe74a4aa1' >}} and at San Diego, 9 ± 0.8 inches (24 ± 2 cm) from 1906 to 2016.{{< tbib '237' '1f19738a-f4ec-4a51-8478-b88163d6dea6' >}} Analyses of these gauges and hundreds around the world show a statistically significant increase in global mean sea level{{< tbib '238' '94a8514e-063e-45ef-b893-11c82b49a597' >}},{{
The authors examined the scientific literature in their areas of expertise. The team placed the highest weight on scientific articles published in refereed peer-reviewed journals. Other sources included published books, government technical reports, and, for data, government websites. The U.S. Global Change Research Program issued a public call for technical input and provided the authors with the submissions. The University of Arizona Center for Climate Adaptation Science and Solutions organized the Southwest Regional Stakeholder Engagement Workshop on January 28, 2017, with over 70 participants at the main location in Tucson, AZ, and dozens of participants in Albuquerque, NM, Boulder, CO, Davis, CA, Los Angeles, CA, Reno, NV, and Salt Lake City, UT, all connected by video. Participants included scientists and managers. The author team met the following day for their only meeting in person. Subsequently, authors held discussions in regular teleconferences. Many chapter authors met at the all-author meeting March 26–28, 2018, in Bethesda, MD.
' report_identifier: nca4 statement: 'Many coastal resources in the Southwest have been affected by sea level rise, ocean warming, and reduced ocean oxygen—all impacts of human-caused climate change (high confidence)—and ocean acidification resulting from human emissions of carbon dioxide (high confidence). Homes and other coastal infrastructure, marine flora and fauna, and people who depend on coastal resources face increased risks under continued climate change (high confidence).
' uncertainties: "Catastrophic rapid loss of Antarctic and Greenland ice sheets could increase sea level more rapidly. Sea level rise at individual locations depends on the form of the seafloor (bathymetry) and other local conditions. Climate change impacts compound overfishing and make fish populations more vulnerable. Potential economic changes in California’s coastal and marine-based economies are subject to many different environmental and socioeconomic factors.
The full complexity of ecological responses to ocean acidification in combination with other stresses in California marine waters is currently unknown. Food supply for marine species,{{< tbib '487' 'cf677518-2ff0-4462-8d41-e48e8655ba18' >}} natural variation in resilience,{{< tbib '488' '04a02114-e2b5-4c87-8c34-5658bc4f3c05' >}},{{
The documented human-caused increase in temperature is a key driver of regional impacts to snow, soil moisture, forests, and wildfire, which affect Indigenous peoples, other frontline communities, and all of civil society. Case study evidence, using Indigenous and Western scientific observations, oral histories, traditional knowledge and wisdom (e.g., Ferguson et al. 2016{{< tbib '493' 'd630a483-2475-4fbb-b942-e5068ac04971' >}}), suggests that climate change is affecting the health, livelihoods, natural and cultural resources, practices, and spiritual well-being of Indigenous communities and peoples in the Southwest (e.g., Redsteer et al. 2011, 2013; Wotkyns 2011; Cozzetto et al. 2013; Gautam et al. 2013; Navajo Nation Department of Fish and Wildlife 2013; Nania and Cozzetto et al. 2014; Sloan and Hostler 2014; Redsteer and Fordham 2017{{< tbib '44' '85923ac2-22e6-4265-9d70-1887132abfce' >}},{{
Abundant evidence and strong agreement among sources exist regarding current impacts of climate change in the region. Impacts of climate change on the food sources, natural resources-based livelihoods, cultural resources and practices, and spiritual health and well-being of Southwest Indigenous peoples are supported, in part, by evidence of regional temperature increases,{{< tbib '23' '29960c69-6168-4fb0-9af0-d50bdd91acd3' >}},{{
Impacts specific to Indigenous peoples include: 1) declining surface soil moisture, higher temperatures, and evaporation converge with oak trees’ decreased resilience,{{< tbib '285' 'd04b2c86-5ca0-42e0-9792-2f319c15cd7e' >}} diminished acorn production, and fire and pest threat to reduce the availability and quality of acorns for tribal food consumption and cultural purposes;{{< tbib '306' 'debdf209-4050-4706-965c-09cff7ec353b' >}} and 2) declining vegetation, higher temperatures, diminished snow, and soil desiccation have caused dust storms and more mobile dunes on some Navajo and Hopi lands, resulting in damaged infrastructure and grazing lands and loss of valued native plant habitat.{{< tbib '44' '85923ac2-22e6-4265-9d70-1887132abfce' >}},{{
Multiple projections of climate and hydrological changes show potential future change and disruption to the ecosystems on which Indigenous peoples depend for their natural resources-based livelihoods, health, cultural practices, and traditions. These include projections of increased temperatures and heat extremes;{{< tbib '24' 'acbb7b12-c119-4c42-8a80-c2555964db4c' >}} longer, more severe, and more frequent drought;{{< tbib '13' 'a42c4f5e-f16b-4196-af05-61f117e0491d' >}},{{
Evidence of specific future disruptions to traditional food sources from forests and oceans mostly relies upon inferences, based on projections of changing seasonality and associated phenological or ecosystem responses{{< tbib '298' '6848eec2-534b-4629-967c-53d8530089a3' >}},{{
Abundant evidence exists of autonomous adaptation strategies, projects, and actions, rooted in traditional environmental knowledge and practices or integration of diverse knowledge systems to inform ecological management to support adaptation and ecosystem resilience.{{< tbib '490' '953476ae-1357-48a5-99d8-1daf963f0a3c' >}},{{
In response to the current and future projected climate changes and ecosystem disruptions, a number of tribes in the Southwest are planning and implementing energy efficient and renewable energy projects.{{< tbib '327' 'fda7d18b-acc5-46fc-9863-3b4ac6a609be' >}},{{
Several tribes in the Southwest are developing climate change adaptation plans to address the current climate-related impacts and prepare for future projected climate changes. The Santa Ynez Band of Chumash Indians, which is working towards an integrated energy and climate action plan, the Yurok Tribe, the Gila River Indian Community, and the Tohono O’odham Nation are among the first tribes in the region to develop climate adaptation and resilience plans, which reflects a nationwide gap or need for further tribal adaptation plan development. Lack of capacity and funds has hindered progress in moving from planning to implementation, which is similar to the situation for U.S. cities.{{< tbib '497' '8a61b1a7-bb52-496d-86f7-21911efcf5f8' >}}
" href: https://data.globalchange.gov/report/nca4/chapter/southwest/finding/key-message-25-4.yaml identifier: key-message-25-4 ordinal: 4 process: 'The authors examined the scientific literature in their areas of expertise. The team placed the highest weight on scientific articles published in refereed peer-reviewed journals. Other sources included published books, government technical reports, and, for data, government websites. The U.S. Global Change Research Program issued a public call for technical input and provided the authors with the submissions. The University of Arizona Center for Climate Adaptation Science and Solutions organized the Southwest Regional Stakeholder Engagement Workshop on January 28, 2017, with over 70 participants at the main location in Tucson, AZ, and dozens of participants in Albuquerque, NM, Boulder, CO, Davis, CA, Los Angeles, CA, Reno, NV, and Salt Lake City, UT, all connected by video. Participants included scientists and managers. The author team met the following day for their only meeting in person. Subsequently, authors held discussions in regular teleconferences. Many chapter authors met at the all-author meeting March 26–28, 2018, in Bethesda, MD.
' report_identifier: nca4 statement: 'Traditional foods, natural resource-based livelihoods, cultural resources, and spiritual well-being of Indigenous peoples in the Southwest are increasingly affected by drought, wildfire, and changing ocean conditions (very likely, high confidence). Because future changes would further disrupt the ecosystems on which Indigenous peoples depend (likely, high confidence), tribes are implementing adaptation measures and emissions reduction actions (very likely, very high confidence).
' uncertainties: "Uncertainties in the climate and hydrologic drivers of regional changes affecting Indigenous peoples in the Southwest include 1) differences in projections from multiple GCMs and associated uncertainties related to regional downscaling methods, 2) the way snow is treated in regional modeling,{{< tbib '498' '64014404-d26e-45c7-9b33-8e2253a9ca04' >}} 3) variability in projections of extreme precipitation, and, in particular, 4) uncertainties in summer and fall precipitation projections for the region.{{< tbib '88' 'e8089a19-413e-4bc5-8c4a-7610399e268c' >}} Additional uncertainties exist in sea level rise projections{{< tbib '242' 'a1aee4ba-d4fc-4f92-a74a-e37189c138b5' >}} and, for the California coast, ocean process model projections of acidification, deoxygenation, and warming coastal zone temperatures.{{< tbib '499' '99e25417-f6c0-49f1-87cd-e9af689f3cff' >}} For the most part, Native lands lack instrumental monitoring for weather and climate, which is a barrier for long-term climate-related planning.{{< tbib '493' 'd630a483-2475-4fbb-b942-e5068ac04971' >}}
Complexities arising from the multiple factors affecting ecosystem processes, including tree mortality and fire, often preclude formal detection and attribution studies. Much evidence and agreement among evidence exist regarding the role of hotter temperatures in fire and tree mortality.{{< tbib '7' 'de4a77df-03ba-4319-a13f-7fdefbb353a5' >}},{{
Other uncertainties relate to estimating future vulnerabilities and impacts, which depend, in part, on adjudication of unresolved water rights and the potential development of local, state, regional, tribal, and national policies that may promote or inhibit the development and deployment of adaptation and mitigation strategies.
" uri: /report/nca4/chapter/southwest/finding/key-message-25-4 url: ~ - chapter_identifier: southwest confidence: "Hydrological drought in California reduced hydroelectric generation{{< tbib '335' '8347d2b2-855d-4765-b7a2-6d2a9e0c99f4' >}} and fossil fuel electricity generation efficiencies. Drought and rising temperatures under climate change can reduce the ability of hydropower and fossil fuel electricity generation to meet growing energy use in the Southwest (very likely, very high confidence). Renewable solar and wind energy offers increased electricity reliability, lower water intensity for energy generation, reduced greenhouse gas emissions, and new economic opportunities (likely, high confidence).
" evidence: "Numerous studies link Southwest hydrologic drought with a decline in renewable hydroelectricity generation in the region. Hydroelectric generation depends on runoff to fill reservoirs to maximize generation capacity.{{< tbib '336' '7db8f4ff-81fb-4d22-949a-076aab55aa86' >}},{{
Similarly, low reservoir levels in Lake Mead—which is formed by damming the Colorado River—driven by reduced Colorado River runoff{{< tbib '13' 'a42c4f5e-f16b-4196-af05-61f117e0491d' >}},{{
Fossil fuel generation efficiency depends on the temperature and availability of the external cooling water. Warming could reduce energy efficiency up to 15% across the Southwest by 2100.{{< tbib '91' '8c12cc4c-3448-4055-b7a2-e03ead1c2572' >}} Higher temperatures also increase electric resistance in transmission lines, causing transmission losses of 7% under higher emissions.{{< tbib '344' '673a11a4-4d3c-4303-af82-29de1ca24bd6' >}} Replacing fossil fuel generation with solar power renewables reduces greenhouse gas emissions and water use per unit of electricity generated.{{< tbib '90' '437ba8f2-66cf-44f5-8bea-173c02458858' >}} This supports the assertion that increasing solar energy generation in the Southwest could meet the energy demand no longer being met by hydropower and fossil fuel as well as the expected increase in energy use in the future.
Solar energy production is also an economic opportunity for the region. The energy potential for renewable energy is estimated to range from one-third to over ten times 2013 generation levels from all sources.{{< tbib '502' '2c0c6750-e017-4590-b7aa-e1756bc7854b' >}} The lower range assumes capacity requirements remain at 2013 levels,{{< tbib '502' '2c0c6750-e017-4590-b7aa-e1756bc7854b' >}} but recent data show an upward trend in Southwest energy use.{{< tbib '89' 'ab3cc54d-c74f-4a6d-8746-efa051c2e97e' >}}
The high potential for solar energy projects in the Southwest and the extent of federally owned land in the Southwest (well over half the total surface area for the six-state region) prompted the Bureau of Land Management (BLM) and the U.S. Department of Energy to conduct a programmatic environmental impact analysis of a new Solar Energy Program to further support utility-scale solar energy development on BLM-administered lands.{{< tbib '502' '2c0c6750-e017-4590-b7aa-e1756bc7854b' >}},{{
Solar and renewable energy jobs are increasing. The solar workforce increased 25% in 2016, while wind employment increased 32%.{{< tbib '505' '92b75533-4ebe-4cad-af48-6789b4627f47' >}} Jobs in low-carbon-emission generation systems, including renewables, nuclear, and advanced low-emission natural gas, comprise 45% of all the jobs in the electric power generation and fuels technologies.{{< tbib '505' '92b75533-4ebe-4cad-af48-6789b4627f47' >}} Growing Southwest energy use, competitive prices for renewables, and the renewable energy potential of the Southwest favor the replacement of fossil-fuel-generated energy by renewable solar and wind energy.
" href: https://data.globalchange.gov/report/nca4/chapter/southwest/finding/key-message-25-5.yaml identifier: key-message-25-5 ordinal: 5 process: 'The authors examined the scientific literature in their areas of expertise. The team placed the highest weight on scientific articles published in refereed peer-reviewed journals. Other sources included published books, government technical reports, and, for data, government websites. The U.S. Global Change Research Program issued a public call for technical input and provided the authors with the submissions. The University of Arizona Center for Climate Adaptation Science and Solutions organized the Southwest Regional Stakeholder Engagement Workshop on January 28, 2017, with over 70 participants at the main location in Tucson, AZ, and dozens of participants in Albuquerque, NM, Boulder, CO, Davis, CA, Los Angeles, CA, Reno, NV, and Salt Lake City, UT, all connected by video. Participants included scientists and managers. The author team met the following day for their only meeting in person. Subsequently, authors held discussions in regular teleconferences. Many chapter authors met at the all-author meeting March 26–28, 2018, in Bethesda, MD.
' report_identifier: nca4 statement: 'The ability of hydropower and fossil fuel electricity generation to meet growing energy use in the Southwest is decreasing as a result of drought and rising temperatures (very likely, very high confidence). Many renewable energy sources offer increased electricity reliability, lower water intensity of energy generation, reduced greenhouse gas emissions, and new economic opportunities (likely, high confidence).
' uncertainties: "Climate model projections of the future diverge on whether precipitation may increase or decrease for much of the region, so hydroelectric power changes may exhibit spatial variation. The amount of runoff is a key factor driving the generation potential for hydroelectric power. A key uncertainty is how much hydroelectricity generation will decline. Some projections of higher-than-average precipitation in the northern parts of the Southwest could roughly offset declines in warm-season runoff associated with warming.{{< tbib '105' '9d8a98fa-0338-486a-b902-cd02d43cae87' >}}
Energy demand in the Southwest is increasing, but the rate of growth is uncertain.{{< tbib '506' '561029d5-4494-43bf-98d2-96ad38606588' >}} Changes in energy market prices cause future uncertainty in the future mix of energy sources for the Southwest.{{< tbib '502' '2c0c6750-e017-4590-b7aa-e1756bc7854b' >}} The low cost of natural gas and the competitive cost of solar and wind renewables make it somewhat certain the proportion of the energy generated from these sources will continue to increase and offset reductions in traditional fossil-fuel-generated energy, reducing overall greenhouse gas emissions.{{< tbib '504' '1f8c0eab-9564-4064-bd8e-b98c135744e9' >}} Renewable energy job growth potential is also uncertain and depends on the factors mentioned above.{{< tbib '505' '92b75533-4ebe-4cad-af48-6789b4627f47' >}}
Additionally, daily to multiyear variation in coastal cloud cover affects solar electricity generation potential along the California coast.{{< tbib '507' 'beba4436-bbd0-43c2-bd04-e6000c5e4a27' >}},{{
Since the availability of affordable food around the world depends upon complex trade and transportation networks, the effects of climate change on Southwest food availability, production, and affordability remain highly complex and thereby uncertain and classified with medium confidence. While the viability of rural livelihoods is vulnerable to water shortages and other climate-related risks, rural livelihoods may be supplemented by other nonagricultural income, such as recreation and hunting. The viability of rural livelihoods is highly complex, and risk is, therefore, classified with medium confidence. Crop impacts related to hotter and drier conditions and reduced winter chill periods, caused by climate change, are classified with medium confidence. Not all crops are directly harmed by warming temperatures, and the simulation impacts of reduced chilling hours can produce a fairly wide range of results depending upon model assumptions. Hotter and drier conditions can directly harm livestock via reduced forage quantity and quality and exposure to higher temperatures, conferring a high confidence classification. Projections of future drought and water scarcity portend increased competition for water from other beneficial uses with medium confidence.
' evidence: "Climate change has altered climate factors fundamental to food production and rural livelihoods in the Southwest. Abundant evidence and good agreement in evidence exist regarding regionally increasing temperatures, reduced soil moisture, and effects on regional snowpack and surface water sources.{{< tbib '13' 'a42c4f5e-f16b-4196-af05-61f117e0491d' >}},{{
Elevated temperatures can be associated with failure of some crops, such as warm-season vegetable crops, and reduced yields and/or quality in others.{{< tbib '374' 'c29be9d3-c558-41ec-979c-f8d0c0b6f0e6' >}} Temperatures in California, Nevada, and Arizona are already at the upper threshold for corn{{< tbib '372' '53efddbf-8a1f-44fb-83e2-167fde08c9aa' >}} and rice.{{< tbib '373' 'a7cfed2a-25b6-4d4f-a9dc-49e1568e2aea' >}} While crops grown in some areas might not be viable under hotter conditions, other crops such as olives, cotton, kiwi, and oranges may replace them.{{< tbib '375' '0a8508df-df59-4080-89a2-52bfeaca47e0' >}} In the Southwest, climate change may cause a northward shift in crop production, potentially displacing existing growers and affecting rural communities.{{< tbib '376' '4442506b-fbba-41ea-9cef-1eac88ce2049' >}} Quality of specialty crops, both nutritive and sensory, declines because of increased temperatures and other changes associated with a changing climate,{{< tbib '393' '3baf471f-751f-4d68-9227-4197fdbb6e5d' >}},{{
High ambient temperatures associated with climate change could decrease production of rangeland vegetation across the Southwest,{{< tbib '384' 'aa6f4075-c70e-43f8-969e-b5625ad25449' >}} reducing available forage for livestock. Ranching enterprises across the region have vastly different characteristics that will influence their adaptive capacities.{{< tbib '390' 'c779538d-b066-4e38-8527-ff3f7552f26e' >}}
Local-scale impacts can vary considerably across the region depending upon surface and groundwater availability. Drought causes altered water management, with heavy reliance on a limited groundwater to sustain regional food production.{{< tbib '130' '7aecf6b3-0b12-40d7-8c61-c1b72cc14289' >}} Despite severe localized impacts, losses in total agricultural revenue are buffered by groundwater reliance to offset surface water shortage.{{< tbib '369' '53ceb8c3-f1b8-4cc1-bb65-3268f4f8bb74' >}} Parts of the Southwest have exhausted sustainable use of groundwater resources. When surface water supplies are reduced, farmers shift to increased groundwater pumping, even when pumping raises production costs{{< tbib '371' 'cf96b502-57a2-4b76-bffc-750e1bf668d6' >}}—declining groundwater tables significantly increase pumping costs and require drilling of deeper wells.{{< tbib '130' '7aecf6b3-0b12-40d7-8c61-c1b72cc14289' >}} Continued climate change may reduce aquifer recharge in the southern part of the region 10%–20%.{{< tbib '370' '2042ab8a-6a82-40a2-99ba-7e67babf8ffc' >}} Climate change is projected to cause longer and more severe drought periods that will intensify the uncertainty associated with Southwest water supply and demand. Water-intensive forage crops and the livestock industry are especially vulnerable to climate-related water shortages.{{< tbib '15' 'bf7e284b-6333-477d-883f-23e002742a6c' >}}
" href: https://data.globalchange.gov/report/nca4/chapter/southwest/finding/key-message-25-6.yaml identifier: key-message-25-6 ordinal: 6 process: 'The authors examined the scientific literature in their areas of expertise. The team placed the highest weight on scientific articles published in refereed peer-reviewed journals. Other sources included published books, government technical reports, and, for data, government websites. The U.S. Global Change Research Program issued a public call for technical input and provided the authors with the submissions. The University of Arizona Center for Climate Adaptation Science and Solutions organized the Southwest Regional Stakeholder Engagement Workshop on January 28, 2017, with over 70 participants at the main location in Tucson, AZ, and dozens of participants in Albuquerque, NM, Boulder, CO, Davis, CA, Los Angeles, CA, Reno, NV, and Salt Lake City, UT, all connected by video. Participants included scientists and managers. The author team met the following day for their only meeting in person. Subsequently, authors held discussions in regular teleconferences. Many chapter authors met at the all-author meeting March 26–28, 2018, in Bethesda, MD.
' report_identifier: nca4 statement: 'Food production in the Southwest is vulnerable to water shortages (medium confidence). Increased drought, heat waves, and reduction of winter chill hours can harm crops (medium confidence) and livestock (high confidence); exacerbate competition for water among agriculture, energy generation, and municipal uses (medium confidence); and increase future food insecurity (medium confidence).
' uncertainties: "The impacts of climate change on food production depend upon microclimatology and local-scale environmental, social, and economic resources. While the scientific community relies upon computer models and generalized information to project likely future conditions, unforeseen consequences of warming temperatures, such as those related to pests, pollinators, and pathogens, may be more detrimental than some of the well-documented projections, such as temperature impacts on reduced yields. The effects of increased precipitation supplying the deep root zone may somewhat offset the increase in temperature, so agricultural drought may be less frequent for trees and other crops dependent on deeper soil moisture.{{< tbib '480' '4fbaaa13-99d2-43df-93db-2be546f18892' >}} Scientists are producing more drought- and heat-tolerant cultivars, which may be suitable to production in the projected warmer and more arid climate of the Southwest.
Since food security relies on complex national and international trade networks, how regional climate change may affect local food security is uncertain. Many adaptation options, such as using alternate breeds, crops, planting and harvest dates, and new (sometimes untested) chemicals, may work in certain situations but not others. Thus, predicting impacts to food production in a hotter/drier land is likely to vary by crop and location, necessitating flexibility and adaptive management. Of paramount uncertainty is the impact of water shortage on regional food production as other uses may outcompete producers for limited supplies.
" uri: /report/nca4/chapter/southwest/finding/key-message-25-6 url: ~ - chapter_identifier: southwest confidence: "Evaluation of confidence levels for the assessment of the type and magnitude of observed or projected public health and clinical impacts was based on the strength of evidence underlying the answers to three primary questions:
What characteristics of the region’s historical climate and weather patterns translate directly (for example, extreme heat) or indirectly (for example, higher temperatures fostering ozone formation or the growth and spread of pathogens and vectors) to exposures associated with observed human health risks that are unique to or overrepresented in the Southwest?
Does recent historical evidence indicate that climate and weather patterns have changed, or do climate models project changes over the 21st century, thereby increasing the risk of human exposures and health impacts evaluated under question 1?
What are the determinants of individual and population vulnerability that increase or decrease the risk of an adverse health outcome or affect adaptive capacity? These include factors that affect a) biological susceptibility, b) physical environment and exposure characteristics, and c) social, behavioral, or economic factors.
To the extent possible, the evaluation recognized and accounted for the complex interconnections among these factors, the fact that their relative importance may differ across geographic and temporal scales, and the combined uncertainties of evidence from multiple disciplines (for example, health sciences, climatology, and social or behavioral sciences) that can vary substantially.
The information revealed by answering those questions, gives high confidence that extreme heat will be the dominant driver of exposures that pose the greatest health risks in the Southwest—including direct effects of heat on individuals and indirect effects of heat on air pollution levels. Due to the uncertainties related to the frequency and intensity of human exposures and related to impacts on essential ecosystem services under projected climate change, the statement “Improving public health systems, community infrastructure, and personal health can reduce serious health risks under future climate change” is made with medium confidence. Nevertheless, clinical and public health policy effectiveness assessments show that such improvements can reduce the burden of disease and health risks associated with environmental exposures.
" evidence: "Strong evidence and good agreement among multiple sources and lines of evidence exist, indicating that the Southwest regional temperature may increase, snowpack may decline, soil moisture may decrease, and drought may be prolonged.{{< tbib '14' 'ba57f86f-c42f-4bba-83f6-676d6875c176' >}},{{
Exposure to hotter temperatures and extreme heat events, partly a manifestation of human-caused climate change, already led to heat-associated deaths and illnesses in heat waves in Arizona and California in the early and mid-2000s.{{< tbib '398' 'b3e00a14-a876-44fa-9c1f-836bd53a7f69' >}},{{
Good agreement exists among models that most of the Southwest may become more arid, due to the effect of increasing temperatures on snow, evaporation, and soil moisture.{{< tbib '58' '4ca5a43c-5fbe-4cb0-8a7d-7ee3acafd7c0' >}},{{
Strong evidence exists of the effects of extreme heat on public health in the region (e.g., Knowlton et al. 2009, Oleson et al. 2015, Wilhelmi et al. 2004{{< tbib '400' '7ca0e947-163a-46f3-9274-cea209b94510' >}},{{
Given the proportion of the U.S. population in the Southwest, a disproportionate number of West Nile virus, plague, hantavirus pulmonary syndrome, and Valley fever cases occur in the region.{{< tbib '158' 'd8bd2def-be9b-47e3-84de-199bcd26c31d' >}},{{
Overall, the Southwest is ill-prepared to absorb the additional patient load that would accompany climate change associated disasters.{{< tbib '448' 'e523f9c0-56f9-44ff-b2d9-7debec2a19d0' >}} The American College of Emergency Physicians assigned an overall emergency care grade of C or C+ to three of the six Southwest states, with the others receiving poorer grades, and four of the six states received an F grade for access to emergency care.{{< tbib '448' 'e523f9c0-56f9-44ff-b2d9-7debec2a19d0' >}}
" href: https://data.globalchange.gov/report/nca4/chapter/southwest/finding/key-message-25-7.yaml identifier: key-message-25-7 ordinal: 7 process: 'The authors examined the scientific literature in their areas of expertise. The team placed the highest weight on scientific articles published in refereed peer-reviewed journals. Other sources included published books, government technical reports, and, for data, government websites. The U.S. Global Change Research Program issued a public call for technical input and provided the authors with the submissions. The University of Arizona Center for Climate Adaptation Science and Solutions organized the Southwest Regional Stakeholder Engagement Workshop on January 28, 2017, with over 70 participants at the main location in Tucson, AZ, and dozens of participants in Albuquerque, NM, Boulder, CO, Davis, CA, Los Angeles, CA, Reno, NV, and Salt Lake City, UT, all connected by video. Participants included scientists and managers. The author team met the following day for their only meeting in person. Subsequently, authors held discussions in regular teleconferences. Many chapter authors met at the all-author meeting March 26–28, 2018, in Bethesda, MD.
' report_identifier: nca4 statement: 'Heat-associated deaths and illnesses, vulnerabilities to chronic disease, and other health risks to people in the Southwest result from increases in extreme heat, poor air quality, and conditions that foster pathogen growth and spread (high confidence). Improving public health systems, community infrastructure, and personal health can reduce serious health risks under future climate change (medium confidence).
' uncertainties: "Uncertainties in the climate and hydrologic drivers of regional changes affecting public health include 1) differences in projections from multiple GCMs and associated uncertainties related to regional downscaling methods, 2) variability in projections of extreme precipitation, 3) uncertainties in summer and fall precipitation projections for the region,{{< tbib '88' 'e8089a19-413e-4bc5-8c4a-7610399e268c' >}} and 4) uncertainties in models that project occurrence and levels of climate-sensitive exposures that are known to impact public health, such as local and regional ozone air pollution, particulate air pollution (for example, increases from wildfire emissions or reductions from advancements in vehicle emissions control technology), or occurrence and exposure to toxins or pathogens.
Studies of non-fatal illnesses using healthcare services data can yield critical insights different from those one can derive from death data. Most studies of heat impacts on health have focused on deaths rather than nonfatal illnesses. This is primarily because hospitalization and emergency department data, compared with death certificate data, are not as available or uniform across locations, and when they are available it can be difficult to access them due to concerns for patient confidentiality. Ongoing enhancements to electronic medical records technology and adoption across the healthcare services sector will potentially address those limitations in the near future and will provide invaluable data resources to identify and adopt prevention strategies that reduce the vulnerability of patients and populations to the adverse effects of climate-sensitive exposures.
More recent work focusing on the more deadly neuroinvasive West Nile virus indicates that regionally, the central and southern parts of the country may experience increasing cost from this vector-borne disease in the future.{{< tbib '178' '0b30f1ab-e4c4-4837-aa8b-0e19faccdb94' >}},{{
While improvements to individual health and to clinical and community infrastructure are highly likely to 1) improve physical capacity to adapt to climate effects, 2) diminish the overall impacts on population health, and 3) increase societal capacity to respond quickly to dampen the effects of long-term and emergency responses,{{< tbib '446' '46b92d0e-f9f2-4b12-8b9e-8c27d6a4b9da' >}},{{
There is very high confidence that the arctic sea ice will continue to reduce in size over the next 20–40 years, and it is likely that the Arctic Ocean will be nearly ice-free in late summer by mid-century based on current climate models. There is also high confidence that this melting will have an effect on the northward expansion of North Pacific fish species and associated effects on associated food webs. There is very high confidence that continued melting of the Arctic Ocean ice will have an effect on the habitat and behavior of polar bear and walrus. There is high confidence that Alaska’s ocean waters are becoming increasingly acidic. Given this increase, it is very likely that there will be biological impacts, but it is uncertain which species will be affected and to what extent.
' evidence: "Changes in arctic sea ice and its impacts on marine ecosystems and various biological resources are well documented by 38 years of satellite records{{< tbib '280' '2aa47611-1a24-4796-b0a8-a0ba3092e470' >}} and the scientific literature.{{< tbib '48' '13e01b3b-caf8-4d85-ac0f-5689df47762a' >}},{{
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.
' report_identifier: nca4 statement: 'Alaska’s marine fish and wildlife habitats, species distributions, and food webs, all of which are important to Alaska’s residents, are increasingly affected by retreating and thinning arctic summer sea ice, increasing temperatures, and ocean acidification. Continued warming will accelerate related ecosystem alterations in ways that are difficult to predict, making adaptation more challenging (very likely, very high confidence).
' uncertainties: 'To date, relatively few of Alaska’s marine species have been studied for their response to ocean acidification, and the assessment of potential impacts is challenging due to each species’ differing habitats, life cycle stages, and response and adaptation mechanisms. It is known that some organisms respond more dramatically to environmental change than others, and warming ocean temperatures may be more significant in the short term than ocean acidification. There is significant uncertainty in the projected increase of shipping through the Arctic and the Bering Strait, since much of this increase will be driven by economic factors and not climate or other environmental change.
' uri: /report/nca4/chapter/alaska/finding/key-message-26-1 url: ~ - chapter_identifier: alaska confidence: 'There is high confidence that wildfire in Alaska will continue but medium confidence as to its ultimate effect on vegetation and permafrost, which is often dependent on fire fields available (e.g., older forests or new growth shrublands), the fire intensity, and the return rate. There is high confidence that the north coast of Alaska is eroding at high rates. It is likely that coastal erosion is accelerating in response to climate change but medium to low confidence as to the location and rate because of limited studies and datasets documenting this. There is high confidence that river erosion will continue but medium confidence as to when, where, and to what extent this will occur across Alaska because of differences in local climatic and geographic qualities of the area in question. There is high confidence and it is likely that the glaciers in Alaska will continue to diminish, especially those that are tidewater glaciers.
' evidence: "Permafrost
Multiple studies of permafrost in Alaska have shown that the gradual warming of the ground{{< tbib '105' '5a612de8-a07d-48c0-a7ca-c4b705157070' >}} has resulted in the warming and thawing of permafrost over the past 30 years,{{< tbib '79' '7fbfdebd-eb73-40be-88ec-109ad7a226fd' >}},{{
Wildfire
It has been well documented that wildfires are a common occurrence in Alaska, especially the interior boreal areas, although they have also occurred in areas of arctic tundra,{{< tbib '114' '9e7065c6-93b9-4bf7-8883-3547a9199ea6' >}},{{
Coastal and River Erosion
The shoreline along Alaska's northern coast has eroded at some of the fastest rates in the Nation, putting local communities, oil fields, and coastal habitat at risk.{{< tbib '19' 'cf15559b-f1e8-4022-945b-45ab149dc1a8' >}} Unlike the contiguous United States, Alaska is subject to glacial and periglacial processes that make permafrost and sea ice key controlling factors of coastal erosion and flooding. Thermal degradation of permafrost leads to enhanced rates of erosion along permafrost-rich coastal shorelines{{< tbib '19' 'cf15559b-f1e8-4022-945b-45ab149dc1a8' >}} and subsidence of already low-lying regions. Longer sea ice-free seasons, higher ground temperatures, and relative sea level rise are expected to exacerbate flooding and accelerate erosion in many regions, leading to the loss of more shoreline in the future.{{< tbib '19' 'cf15559b-f1e8-4022-945b-45ab149dc1a8' >}}
While erosion and changed river courses are a normal part of landscape evolution, lateral river erosion rates are likely to change over time, but the direction and magnitude of these changes are poorly understood. Major river erosion events are typically tied to high hydrological flows or the melting of permafrost along river and stream banks. Statewide, evidence for changes in maximum gauged streamflows is mixed, with a majority of locations having no significant trend.{{< tbib '289' '41ed988f-4fa6-476d-90c9-ef9e3e8d1806' >}} There is significance for seasonal changes in the timing of peak flows in interior Alaska, though increases in the absolute magnitude are not well evident in existing data.{{< tbib '290' '5e61fa98-c1ff-42e6-aa82-10dad90342d9' >}} Riverine erosion is a serious problem for a significant number of communities.{{< tbib '123' '49a37e8f-eef6-4ee6-9705-fac54c48df30' >}} Significant resources have been expended to slow erosion at some communities, often through the construction of berms and bank stabilization projects. These projects have a mixed record of success and nearly always require ongoing maintenance.
Glacier Change
Airborne altimetry surveys of Alaska glaciers spanning the 1994–2013 interval and covering about 40% of the region’s glacierized area{{< tbib '137' 'df531aa2-4a99-4ce7-9dd9-744729e2161d' >}} yield decadal timescale mass balance estimates for individual glaciers and a regional estimate.{{< tbib '291' '08047702-47b0-4401-ab44-a0f46a16efe5' >}} Several new modeling studies suggest that the measured rates of Alaska ice loss are likely to increase in coming decades,{{< tbib '139' 'c426adb7-b055-4726-80f1-82d7846f46c0' >}},{{
Interdisciplinary research along the Gulf of Alaska is providing new insights into the role of glacier runoff in structuring downstream freshwater and nearshore marine ecosystems.{{< tbib '101' '141ed68e-5810-4735-afee-878ceb6041cc' >}} End-of-century projections from physically based models suggest that anticipated atmospheric warming (2°–4.5°C) will drive volume losses of 32%–58% for Alaska glaciers.{{< tbib '142' '226e7316-1460-4cfe-94a1-4bca27549241' >}} Increases in river chemical ions due to glacial runoff and permafrost melt have also been associated with diminishing glaciers in Alaska.{{< tbib '94' '7c14626a-343f-48a3-9076-1bd656f663c3' >}},{{
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.
' report_identifier: nca4 statement: 'Alaska residents, communities, and their infrastructure continue to be affected by permafrost thaw, coastal and river erosion, increasing wildfire, and glacier melt. These changes are expected to continue into the future with increasing temperatures, which would directly impact how and where many Alaskans will live (very likely, high confidence).
' uncertainties: 'Some events such as wildfires and coastal storms are dependent on regional and local current weather conditions, and the exact landscape or ecosystem response can be highly variable. Future effects are also dependent on quick response actions and adaptation measures.
' uri: /report/nca4/chapter/alaska/finding/key-message-26-2 url: ~ - chapter_identifier: alaska confidence: 'There is high confidence that there will be a continuation of trends causing higher winter temperatures, increased storm events, increased frequency and extent of wildfires, and increased permafrost thawing with associated erosion. Given these trends, there is very likely to be subsequent human health effects, but the distribution and magnitude of these effects remain uncertain.
' evidence: "The evidence base for climate-related health threats can be divided into three main categories. First are those threats that have strong documentation of both the climate or environmental driver and the health effect. An example is the emergence of gastrointestinal illness due to the northward expansion of the bacteria Vibrio parahaemolyticus among Alaska shellfish. Other threats with a similar level of evidence include increased venomous insect stings.
Second, some health threats are based on a combination of well-documented climate-driven environmental changes and records of anecdotal community observations of health impacts. Examples include the increased risk of injury or death from exposure among winter subsistence-related travelers or respiratory problems from smoke inhalation during wildfires. The community observations of these threats point to a real trend.{{< tbib '10' 'cc3776b7-7ea8-42e9-802d-2ef5e6ac2f40' >}},{{
The third category is those threats that are logical inferences of potential health risks based on documented environmental changes and community-vulnerability assessments. Examples include the well-documented threats from coastal storms to community infrastructure and shorelines and the damage to community water and sanitation systems from permafrost thawing or erosion. The risk of physical harm from major storm or flooding events is obvious, and the loss of a water/sewer system would likewise pose a clear threat to health through waterborne or water-washed infections. However, these threats are based on likely outcomes from existing trends in environmental change. The human health effects are either undocumented or are anticipated in the future. Many of the infectious disease risks and harmful algal blooms (HABs) fall into this category; where range expansion of pathogens or vectors is occurring, health effects are likely to follow.
" href: https://data.globalchange.gov/report/nca4/chapter/alaska/finding/key-message-26-3.yaml identifier: key-message-26-3 ordinal: 3 process: '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.
' report_identifier: nca4 statement: 'A warming climate brings a wide range of human health threats to Alaskans, including increased injuries, smoke inhalation, damage to vital water and sanitation systems, decreased food and water security, and new infectious diseases (very likely, high confidence). The threats are greatest for rural residents, especially those who face increased risk of storm damage and flooding, loss of vital food sources, disrupted traditional practices, or relocation. Implementing adaptation strategies would reduce the physical, social, and psychological harm likely to occur under a warming climate (very likely, high confidence).
' uncertainties: 'The greatest uncertainties in the health threats of climate change lie in the geographic distribution, magnitude, duration, and capacity to detect the effects. Many of the impacts of climate changes are most evident in rural Alaska, which is an enormous area and sparsely populated. Thus, sporadic events with geographic variability such as storms or HABs may have a range of human health effects from none to severe, depending on the timing and location of exposure. Likewise, the magnitude and duration of the effects on health are difficult to predict based on variability in the source of risk and human adaptation. The lack of repeated outbreaks of V. parahaemolyticus illnesses from raw shellfish consumption is a good example of how adaptations in aquaculture practices and commercial regulations, along with likely changes in consumer practices, appear to have reduced the magnitude of the health threats, compared with initial outbreak. Finally, we have limited capacity to detect many of the health outcomes associated with climate change. The organized reporting and monitoring of climate-linked health effects by public health are limited to the toxin-mediated illnesses, some of the infectious diseases, mortality events, and unusual clusters of illnesses or injuries. Even among those conditions, underreporting of illnesses is common due to healthcare-seeking behavior, lack of recognition by medical providers due to unfamiliarity or limited diagnostic capacities, or incomplete compliance. For many of the anticipated health effects, such as nonoccupational injuries, mental health issues, and respiratory conditions, there may be documentation in a person’s individual health records, but no systems are in place to collect such information and link these illnesses to climate or environmental events or conditions. Large administrative healthcare databases, such as the Alaska Hospital Discharge Data System or the Alaska Health Information Exchange, could be used for focused investigations or ongoing monitoring. However, these would only be useful for severe illnesses with large geographic or multiyear distributions. These datasets would likely miss health events that do not result in emergency room visits or hospitalizations, that are rare, or that occur in irregular episodes. Data from ambulatory clinic visits, community surveys, or syndrome-based surveillance efforts would be needed to detect and characterize uncommon or less severe health occurrences.
' uri: /report/nca4/chapter/alaska/finding/key-message-26-3 url: ~ - chapter_identifier: alaska confidence: 'There is high confidence that climate change is having far-reaching effects on Alaska’s Indigenous peoples. It is likely that most of these impacts will have negative effects, as they undermine existing behaviors, patterns, infrastructure, and expectations. It is also likely that there will continue to be some benefits and opportunities stemming from climate-related changes. There is medium confidence that the negative impacts can be reduced and the new opportunities maximized with appropriate policy and regulatory action, as not all aspects of change can be addressed in this way, and it is unclear whether such a systematic approach is plausible in light of the way programs and policies are administered in Alaska’s Indigenous communities.
' evidence: "Many studies have examined different aspects of Alaska’s Indigenous communities, including the ways climate change is affecting or can affect subsistence,{{< tbib '15' 'e0b0f2a6-5ac8-4196-8634-6123511e0051' >}},{{
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.
' report_identifier: nca4 statement: 'The subsistence activities, culture, health, and infrastructure of Alaska’s Indigenous peoples and communities are subject to a variety of impacts, many of which are expected to increase in the future (likely, high confidence). Flexible, community-driven adaptation strategies would lessen these impacts by ensuring that climate risks are considered in the full context of the existing sociocultural systems (likely, medium confidence).
' uncertainties: 'There is little question that climate change is having widespread and far-reaching impacts on Alaska’s Indigenous peoples. It is less clear, however, exactly which peoples and communities are responding to the changes they face. One community may be able to seize a new opportunity or may be able to adjust effectively to at least some forms of change, whereas another community will not be able to do either. More needs to be understood about these differences, the reasons for them, and how adaptability and resilience can be fostered.
It is also unclear how, exactly, the changes will influence one another as they occur in the context of all that is happening in Alaska Native life. For example, climate change may mean hunters have to travel farther to hunt. GPS allows for more reliable navigation, and four-stroke engines provide more confidence when traveling farther offshore. At the same time, rising fuel prices mean it is more expensive to travel far, perhaps limiting the ability of a hunter to take advantage of better navigation and motors. How these competing influences will balance out is difficult to say and requires more attention.
' uri: /report/nca4/chapter/alaska/finding/key-message-26-4 url: ~ - chapter_identifier: alaska confidence: '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.
' evidence: "Coastal erosion affects a number of coastal communities, with the highest rates on the Arctic coastline.{{< tbib '19' '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.{{< tbib '123' '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.{{< tbib '122' '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.{{< tbib '145' '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.
" href: https://data.globalchange.gov/report/nca4/chapter/alaska/finding/key-message-26-5.yaml identifier: key-message-26-5 ordinal: 5 process: '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.
' report_identifier: nca4 statement: '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).
' 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.
' uri: /report/nca4/chapter/alaska/finding/key-message-26-5 url: ~ - chapter_identifier: alaska confidence: 'There is high confidence that proactive adaptation can reduce costs, generate social and economic opportunity, and improve livelihood security. It is likely and there is high confidence that proactive adaptation will be affected by external factors, such as global markets that are beyond the control of the organization or institution implementing the adaptations.
It is likely and there is very high confidence that direct engagement and partnership with communities will be a critical element of adaptation success, as this has strong evidence and high consensus in the literature; however, there are a limited number of publications that document this partnership model in Alaska.
' evidence: "Research investigating costs of adapting to projected climate changes in Alaska in the realms of public infrastructure and wildfire suppression indicates cost savings from adaptation.{{< tbib '21' 'b7e764c8-8912-4d18-8dd3-1555ab8da1c2' >}},{{
Adaptation actions to the impacts of climate change in Alaska have been transitioning from awareness and concern to education and actions.{{< tbib '135' 'b8ad073b-11cd-4b02-809d-f992e02566b4' >}},{{
Most research reports on case studies and actions that describe transparent, collaborative, and accessible information though data sharing, building of networks, and long-term partnerships with communities.{{< tbib '252' '46337d79-86c4-4e77-bab9-724c5f44c63f' >}},{{
A number of climate adaptation guidebooks focus on Alaska and Canada, which have related adaptation challenges.{{< tbib '134' 'f3fa0761-8412-46f5-9da4-b9b467bd8521' >}} Universities, governments, and nongovernmental organizations produced these guidebooks for a range of audiences, including rural Alaska Native communities, local governments, and state governments. Key phases in the adaptation planning process that are consistent across the majority of the guidebooks include building partnerships and networks of stakeholders; conducting vulnerability and risk assessments; establishing priorities, options, and an implementation plan and evaluation metrics; implementing the preferred option; and conducting ongoing monitoring and adjustment of activities.{{< tbib '134' 'f3fa0761-8412-46f5-9da4-b9b467bd8521' >}} Guidebooks specific to Alaska Natives and Canadian Inuit and First Nations peoples emphasize the importance of community support and participation in the adaptation planning process.{{< tbib '134' 'f3fa0761-8412-46f5-9da4-b9b467bd8521' >}}
" href: https://data.globalchange.gov/report/nca4/chapter/alaska/finding/key-message-26-6.yaml identifier: key-message-26-6 ordinal: 6 process: '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.
' report_identifier: nca4 statement: 'Proactive adaptation in Alaska would reduce both short- and long-term costs associated with climate change, generate social and economic opportunity, and improve livelihood security (likely, high confidence). Direct engagement and partnership with communities is a vital element of adaptation in Alaska (likely, very high confidence).
' uncertainties: "Little research has been conducted to track and evaluate the efficacy of implementation of existing adaptation planning in Alaska or to assess the possibilities for maladaptation. Similarly, the feedbacks and synergies are not well documented between adaptation and changes in physical, natural, and social systems. More research is needed to understand cross-sector and cumulative impacts and how they can best be addressed in an all-inclusive manner.{{< tbib '135' 'b8ad073b-11cd-4b02-809d-f992e02566b4' >}}
" uri: /report/nca4/chapter/alaska/finding/key-message-26-6 url: ~ - chapter_identifier: hawaii-and-pacific-islands confidence: 'There is very high confidence in further increases in temperature in the region, based on the consistent results of global climate models showing continued significant increases in temperature in the Hawai‘i–USAPI region for all plausible emissions scenarios.
There is low confidence regarding projected changes in precipitation patterns, stemming from the divergent results of global models and downscaling approaches and from uncertainties around future emissions. However, for leeward areas of Hawai‘i and the eastern part of the Federated States of Micronesia (FSM), future decreases in precipitation are somewhat more likely, based on greater agreement between downscaling approaches for Hawai‘i and greater agreement among global models for eastern FSM.
There is very high confidence in future increases in sea level, based on widely accepted evidence that warming will increase global sea level, with amplified effects in the low latitudes.
There is medium confidence in the increasing risk of both drought and flood extremes patterns, based on both observed changes (for example, increasing lengths of wet and dry periods) and projected effects of warming on extreme weather globally.
There is medium confidence in possible future catastrophic impacts on food and water security resulting from saltwater contamination in low atolls due to sea level rise; this is based on very high confidence in continuing sea level rise, the known effects of saltwater contamination on water supply and agriculture, and uncertainty regarding the effectiveness of adaptation measures.
' evidence: "Vulnerability of water supplies to climate change: With their isolation and limited land areas, Hawai‘i and the USAPI are vulnerable to the effects of climate change on water supplies.{{< tbib '72' '97ae6e5b-3482-4760-a4f4-9e00ee6337b6' >}},{{
Temperature change: In Hawai‘i, air temperature increased by 0.76°F (0.42°C) over the past 100 years. The year 2015 was the warmest on record at 1.43°F (0.79°C) above the 100-year average. Mean and minimum (nighttime) temperatures both show long-term, statistically significant increasing trends, while the diurnal temperature range (the average difference between daily minimum and maximum temperature) shows a long-term, statistically significant decreasing trend.{{< tbib '59' '7621e6f5-4234-4a44-bb1d-8278429deb2b' >}} Estimates of historical temperature changes in Hawai‘i are based on the relatively few observing stations with long records and represent the best available data. Further temperature increases in the Hawai‘i–USAPI region are highly likely. Northern tropical Pacific (including Micronesia) sea level air temperatures are expected to increase by 2.2°–2.7°F (1.2°–1.5°C) by mid-century and by 2.7°–5.9°F (1.5°–3.3°C) by 2100.{{< tbib '63' '1fca63fb-3033-445e-99ba-1136da451058' >}} Southern tropical Pacific (including American Sāmoa) sea level air temperatures are expected to increase by 1.8°–3.1°F (1.0°–1.7°C) by mid-century and by 2.5°–5.8°F (1.4°–3.2°C) by 2100.{{< tbib '63' '1fca63fb-3033-445e-99ba-1136da451058' >}} Increasing temperatures throughout the Hawai‘i–USAPI region might cause increases in potential evapotranspiration,{{< tbib '226' 'bdbb00c1-6c40-4e03-9120-2df759b580a7' >}} with consequent negative impacts on water supplies.
Precipitation change: While Hawai‘i precipitation has experienced upward and downward changes across a range of timescales, more than 90% of the state had a net downward rainfall trend during 1920–2012.{{< tbib '60' 'e6d1098e-93cc-4285-9d16-6e52c5e302f7' >}} Projections of future precipitation changes in Hawai‘i are still uncertain. Using a dynamical downscaling approach to project climate changes in Hawai‘i for the 20-year period at the end of the this century under a middle-of-the-road scenario (SRES A1B) resulted in increases in mean annual rainfall of up to 30% in the wet windward areas of Hawaiʻi and Maui Islands and decreases of 40% in some of the dry leeward and high-elevation interior areas.{{< tbib '34' 'f60beed2-efd0-40c8-8f94-b81d3e9f1509' >}} Somewhat different results were obtained using an independent statistical downscaling method.{{< tbib '34' 'f60beed2-efd0-40c8-8f94-b81d3e9f1509' >}} For the lower scenario (RCP4.5), mean annual rainfall in Hawai‘i is projected by statistical downscaling to have only small changes in windward areas of Hawai‘i and Maui Islands, to decrease by 10%–20% in windward areas of the other islands, and to decrease by up to 60% in leeward areas for the period 2041–2070. For the same scenario, the late-century (2071–2100) projection is similar to the 2041–2070 projection, except that a larger portion of the leeward areas will experience reductions of 20%–60%. For the higher scenario (RCP8.5), windward areas of Hawai‘i and Maui Islands will see changes between +10% and −10%, and rainfall in leeward areas will decrease by 10% to more than 60% by the 2041–2070 period. By the late-century period (2071–2100), windward areas of Hawai‘i and Maui Islands will see increases of up to 20%, windward areas on other islands will have decreases of 10% to 30%, and leeward areas will have decreases of 10% to more than 60%. The number of climate and water resources monitoring stations has declined across the region,{{< tbib '23' '7350d7b3-6e95-4375-ba23-26756b441fc2' >}},{{
Trends in hydrological extremes in Hawai‘i: Increasing trends in extreme 30-day rainfall and the lengths of consecutive dry-day and consecutive wet-day periods{{< tbib '66' 'f8ccfb79-1bed-462d-9172-c56a71b542b9' >}} indicate that Hawai‘i’s rainfall is becoming more extreme and suggest that both droughts and floods are becoming more frequent in Hawai‘i. With the addition of more years of observed data, and a more detailed spatiotemporal analysis from a grid-box level down to the island level, this contrasts with the earlier findings of a decreasing trend in the number of extreme rainfall events in Hawai‘i.{{< tbib '227' '39d80273-7b1f-4342-8c9d-439e262dea4f' >}}
Saltwater contamination due to sea level rise: Sea level rise exacerbates the existing vulnerability of groundwater lenses on small coral islands to contamination by saltwater intrusion by amplifying the impacts of freshwater lens-shrinking droughts and storm-related overwash events.{{< tbib '69' 'dc90f15e-2420-461e-ba38-f65717485591' >}}
" href: https://data.globalchange.gov/report/nca4/chapter/hawaii-and-pacific-islands/finding/key-message-27-1.yaml identifier: key-message-27-1 ordinal: 1 process: "To frame this chapter, the regional leads wanted to maximize inclusiveness and represent the key sectoral interests of communities and researchers. To select sectors and a full author team, the coordinating lead author and regional chapter lead author distributed an online Google survey from September to October 2016. The survey received 136 responses representing Hawaiʻi and all the U.S.-Affiliated Pacific Islands (USAPI) jurisdictions; respondents identified which of the National Climate Assessment (NCA) sectors they were most interested in learning about with respect to climate change in the Pacific Islands and suggested representative case studies.{{< tbib '223' '884675c9-3e31-483d-b6b9-fd53b99875ae' >}} The five top sectors were picked as the focus of the chapter, and a total of eight lead authors with expertise in those sectors were invited to join the regional team. To solicit additional participation from potential technical contributors across the region, two informational webinars spanning convenient time zones across the Pacific were held; 35 people joined in. The webinars outlined the NCA history and process, as well as past regional reports and ways to participate in this Fourth National Climate Assessment (NCA4).
A critical part of outlining the chapter and gathering literature published since the Third National Climate Assessment (NCA3){{< tbib '224' 'dd5b893d-4462-4bb3-9205-67b532919566' >}} was done by inviting technical experts in the key sectors to participate in a half-day workshop led by each of the lead authors. A larger workshop centered on adaptation best practices was convened with participants from all sectors, as well as regional decision-makers. In all, 75 participants, including some virtual attendees, took part in the sectoral workshops on March 6 and 13, 2017. Finally, to include public concerns and interests, two town hall discussion events on March 6 and April 19, 2017, were held in Honolulu, Hawaiʻi, and Tumon, Guam, respectively. Approximately 100 participants attended the town halls. Throughout the refining of the Key Messages and narrative sections, authors met weekly both via conference calls and in person to discuss the chapter and carefully review evidence and findings. Technical contributors were given multiple opportunities to respond to and edit sections. The process was coordinated by the regional chapter lead and coordinating lead authors, as well as the Pacific Islands sustained assessment specialist.
" report_identifier: nca4 statement: 'Dependable and safe water supplies for Pacific island communities and ecosystems are threatened by rising temperatures (very high confidence), changing rainfall patterns (low confidence), sea level rise (very high confidence), and increased risk of extreme drought and flooding (medium confidence). Islands are already experiencing saltwater contamination due to sea level rise, which is expected to catastrophically impact food and water security, especially on low-lying atolls (medium confidence). Resilience to future threats relies on active monitoring and management of watersheds and freshwater systems.
' uncertainties: "Effects of warming on evapotranspiration: There are uncertainties in how warming will affect cloud cover, solar radiation, humidity, and wind speed. All of these affect potential evapotranspiration and changes in soil moisture, and the effects will differ by region.{{< tbib '228' '44466960-d3a9-4374-b1cf-893bb8a476f0' >}}
Future precipitation changes: Global models differ in their projections of precipitation changes for the Hawai‘i–USAPI region.{{< tbib '63' '1fca63fb-3033-445e-99ba-1136da451058' >}} For Hawai‘i, downscaled projections differ according to the choice of global model time horizon, emissions scenario, and downscaling method.{{< tbib '229' '9171ec97-c44b-48eb-80b3-2756ba8a14a3' >}}
" uri: /report/nca4/chapter/hawaii-and-pacific-islands/finding/key-message-27-1 url: ~ - chapter_identifier: hawaii-and-pacific-islands confidence: 'It is very likely that air and water temperatures will increase and that sea level will rise (very high confidence). Research indicates that global mean sea level rise will exceed previous estimates and that, in the USAPI, sea level rise is likely to be higher than the global mean (likely, high confidence). As a result, it is likely that climate change will affect low-lying and coastal ecosystems in Hawaiʻi and other Pacific islands, with medium confidence in forecasts of the effects on these ecosystems.
There is low confidence as to how rainfall patterns will shift across the main Hawaiian Islands. It is considered likely that changes in rainfall will result in ecologic shifts expected to threaten some species. However, there is low confidence in specific ecologic forecasts because the direction and magnitude of rainfall changes are uncertain, and there is a lack of robust understanding of how species will respond to those changes. It seems as likely as not that the responses of terrestrial biomes and species to climate change will result in additional complexity in the management of rare and threatened species.
' evidence: "Projections of sea level rise have been made at both regional and local scales (see Traceable Account for Key Message 3). Based on these projections, the effects of sea level rise on coastal ecosystems have been evaluated for the Northwest Hawaiian Islands.{{< tbib '18' '8fd88741-58fd-4753-ae35-af3a2ed38915' >}},{{
Forecasts of how climate change will affect rainfall and temperature in the main Hawaiian Islands have been based on both statistical and dynamical downscaling of global climate models (GCMs; see Traceable Account for Key Message 1). Statewide vulnerability models have been developed for nearly all species of native plants{{< tbib '233' 'c0eb08ae-6725-4e68-b99e-1f2cef382c25' >}} and forest birds,{{< tbib '43' 'f483b8cf-8401-40ec-9001-23466261d5fa' >}} showing substantial changes in the available habitat for many species. More detailed modeling within Hawaiʻi Volcanoes National Park has suggested that rare and listed plants being managed in Special Ecological Areas will experience climate changes that make the habitat in these areas unsuitable.{{< tbib '91' '5eac12ba-e664-4eb2-aa66-18d9067566d8' >}}
Effects of climate change on streamflow in Hawaiʻi will largely be driven by changes in rainfall, although geologic conditions affect the discharge of groundwater that provides base flow during dry weather.{{< tbib '234' '381cc925-f22b-46a5-8a36-3e99bbd52635' >}} A regional watershed model from the windward side of Hawaiʻi Island suggested that control of an invasive tree with high water demand would somewhat mitigate decreases in streamflow that might be caused by a drier climate.{{< tbib '44' 'e69ceccd-2c27-48f0-b3fe-46ce1b67f636' >}} Finally, it has been suggested that ocean acidification will decrease the viability of the planktonic larvae of native Hawaiian stream fishes.{{< tbib '99' '0c523a5a-213e-491a-9dcf-0a2c7eb05d77' >}}
" href: https://data.globalchange.gov/report/nca4/chapter/hawaii-and-pacific-islands/finding/key-message-27-2.yaml identifier: key-message-27-2 ordinal: 2 process: "To frame this chapter, the regional leads wanted to maximize inclusiveness and represent the key sectoral interests of communities and researchers. To select sectors and a full author team, the coordinating lead author and regional chapter lead author distributed an online Google survey from September to October 2016. The survey received 136 responses representing Hawaiʻi and all the U.S.-Affiliated Pacific Islands (USAPI) jurisdictions; respondents identified which of the National Climate Assessment (NCA) sectors they were most interested in learning about with respect to climate change in the Pacific Islands and suggested representative case studies.{{< tbib '223' '884675c9-3e31-483d-b6b9-fd53b99875ae' >}} The five top sectors were picked as the focus of the chapter, and a total of eight lead authors with expertise in those sectors were invited to join the regional team. To solicit additional participation from potential technical contributors across the region, two informational webinars spanning convenient time zones across the Pacific were held; 35 people joined in. The webinars outlined the NCA history and process, as well as past regional reports and ways to participate in this Fourth National Climate Assessment (NCA4).
A critical part of outlining the chapter and gathering literature published since the Third National Climate Assessment (NCA3){{< tbib '224' 'dd5b893d-4462-4bb3-9205-67b532919566' >}} was done by inviting technical experts in the key sectors to participate in a half-day workshop led by each of the lead authors. A larger workshop centered on adaptation best practices was convened with participants from all sectors, as well as regional decision-makers. In all, 75 participants, including some virtual attendees, took part in the sectoral workshops on March 6 and 13, 2017. Finally, to include public concerns and interests, two town hall discussion events on March 6 and April 19, 2017, were held in Honolulu, Hawaiʻi, and Tumon, Guam, respectively. Approximately 100 participants attended the town halls. Throughout the refining of the Key Messages and narrative sections, authors met weekly both via conference calls and in person to discuss the chapter and carefully review evidence and findings. Technical contributors were given multiple opportunities to respond to and edit sections. The process was coordinated by the regional chapter lead and coordinating lead authors, as well as the Pacific Islands sustained assessment specialist.
" report_identifier: nca4 statement: 'Pacific island ecosystems are notable for the high percentage of species found only in the region, and their biodiversity is both an important cultural resource for island people and a source of economic revenue through tourism (very high confidence). Terrestrial habitats and the goods and services they provide are threatened by rising temperatures (very likely, very high confidence), changes in rainfall (likely, medium confidence), increased storminess (likely, medium confidence), and land-use change (very likely, very high confidence). These changes promote the spread of invasive species (likely, low confidence) and reduce the ability of habitats to support protected species and sustain human communities (likely, medium confidence). Some species are expected to become extinct (likely, medium confidence) and others to decline to the point of requiring protection and costly management (likely, high confidence).
' uncertainties: 'The timing and magnitude of sea level rise are somewhat uncertain. There is greater uncertainty on how climate change will affect the complex patterns of precipitation over the high islands of Hawaiʻi. There is also high uncertainty about how plants will respond to changes in their habitats and the extent to which climate change will foster the spread of invasive species.
' uri: /report/nca4/chapter/hawaii-and-pacific-islands/finding/key-message-27-2 url: ~ - chapter_identifier: hawaii-and-pacific-islands confidence: 'There is very high confidence that a continued rise in global temperature will lead to increases in the rate of sea level rise. There is less confidence in the projected amounts of sea level rise during this century, and there is low confidence in the upper bounds of sea level rise by the end of the century. Sea level rise will very likely lead to saltwater intrusion, coastal erosion, and wave flooding. It is very likely this will strain the sustainability of human infrastructure systems, limit freshwater resources, and challenge food availability. If the high-end projections of future sea level rise materialize, it is very likely this will threaten the very existence of Pacific island coastal communities.
' evidence: "Multiple lines of research have shown that changes in melting in Greenland,{{< tbib '110' 'ef6eb8d0-6301-4987-a2ff-9606e1f4177a' >}} the Antarctic,{{< tbib '107' 'ae82c8a3-3033-4103-91e9-926a27d1fa18' >}} and among alpine glaciers,{{< tbib '111' '5d34229c-b521-42f4-aad1-f2ffc600879d' >}} as well as the warming of the ocean,{{< tbib '113' '6bbe13d9-4992-456c-b97d-42947994b6be' >}} have occurred faster than expected. The rate of sea level rise is accelerating,{{< tbib '103' 'd7ed19d6-e5ac-4b44-b686-0a8a16fc431b' >}} and the early signs of impact are widely documented.{{< tbib '9' '7717dd13-7f6b-4b7c-ab84-571d50f7b8da' >}} Relative to the year 2000, global mean sea level (GMSL) is very likely to rise 0.3–0.6 feet (9–18 cm) by 2030, 0.5–1.2 feet (15–38 cm) by 2050, and 1.0–4.3 feet (30–130 cm) by 2100 (very high confidence in lower bounds; medium confidence in upper bounds for 2030 and 2050; low confidence in upper bounds for 2100).{{< tbib '17' 'c66bf5a9-a6d7-4043-ad99-db0ae6ae562c' >}},{{
Changes in precipitation,{{< tbib '235' 'c57f7893-035e-49d9-b31d-83856dab8624' >}} Pacific sea level,{{< tbib '4' '6e320831-727b-482d-982a-45732be3790f' >}} climate variability,{{< tbib '3' 'e5f02380-28e9-4238-994f-09a2efba32ae' >}} and the unsustainable practices of many human communities among Pacific islands{{< tbib '127' 'f22f00d3-1456-4fef-b286-a4af1494bb93' >}} all converge to increase the vulnerability of coastal populations{{< tbib '135' 'e16534d0-638a-4fdc-88fb-426611965c54' >}} as climate change continues in the future.{{< tbib '55' 'a9307aae-3eb6-41f2-9921-ba96fa8ac075' >}} As sea level rises and average atmospheric temperature continues to increase, wave events{{< tbib '37' '1b9a155a-3d54-41ff-a844-1400bb326927' >}} associated with changing weather patterns{{< tbib '140' 'fc838fdf-81d0-488b-a2b5-0781d7bbc9ef' >}} constitute a growing mechanism for delivering{{< tbib '12' 'f4859f1b-a4d7-4e21-a05b-70204fd6df59' >}} damaging saltwater into island aquifer systems,{{< tbib '13' '88dcd306-5ae7-48df-8411-658f9c5d97bc' >}} ecosystems,{{< tbib '129' 'd055c0df-2c85-4ee1-a3c6-8e6c79e425bd' >}} and human infrastructure systems.{{< tbib '17' 'c66bf5a9-a6d7-4043-ad99-db0ae6ae562c' >}}
In Hawaiʻi, studies by the Hawaiʻi Climate Change Mitigation and Adaptation Commission{{< tbib '42' '0244c888-89df-4a3c-a7f1-79af0a0a6f00' >}} reveal that with 3.2 feet of sea level rise, over 25,800 acres of land in the state would be rendered unusable. Some of that land would erode into the ocean, some would become submerged by inches or feet of standing water, and some areas would be dry most of the year but repeatedly washed over by seasonal high waves. Statewide, about 34% of that potentially lost land is designated for urban use, 25% is designated for agricultural use, and 40% is designated for conservation. The loss of urban land is expected to increase pressure on the development of inland areas, including those designated as agricultural and conservation lands. Across the state, over 6,500 structures located near the shoreline would be compromised or lost with 3.2 feet of sea level rise. Some of these vulnerable structures include houses and apartment buildings, and their loss would result in over 20,000 displaced residents in need of new homes. The value of projected flooded structures, combined with the land value of the 25,800 acres projected to be flooded, amounts to over $19 billion across the state (in 2013 dollars; $19.6 billion in 2015 dollars). However, this figure does not encompass the full loss potential in the state, as monetary losses that would occur from the chronic flooding of roads, utilities, and other public infrastructure were not analyzed in this report and are expected to amount to as much as an order of magnitude greater than the potential economic losses from land and structures. For example, over 38 miles of major roads would be chronically flooded across the state with 3.2 feet of sea level rise. Utilities, such as water, wastewater, and electrical systems, often run parallel and underneath roadways, making lost road mileage a good indication of the extent of lost utilities. This chronic flooding of infrastructure would have significant impacts on local communities as well as reverberating effects around each island.
The loss of valuable natural and cultural resources across all islands would cost the state dearly, due to their intrinsic value. Beaches that provide for recreation, wildlife habitat, and cultural tradition would erode, from iconic sites such as Sunset Beach on O‘ahu to neighborhood beach access points rarely visited by anyone except local residents. Some beaches would be lost entirely if their landward migration is blocked by roads, structures, shoreline armoring, or geology. The flooding of the more than 2,000 on-site sewage disposal systems with 3.2 feet of sea level rise would result in diminished water quality in streams and at beaches and shoreline recreation areas. The loss of and harm to native species and entire ecosystems would have implications for Hawaiian cultural traditions and practices, which are closely tied to the natural environment. Further, nearly 550 cultural sites in the state would be flooded, and many Hawaiian Home Lands communities would be impacted by flooding. In some cases, inland migration or careful relocation of these natural and cultural resources is expected to be possible. In other cases, the resources are inextricably bound to place and would be permanently altered by flooding.{{< tbib '42' '0244c888-89df-4a3c-a7f1-79af0a0a6f00' >}}
Marra and Kruk (2017){{< tbib '142' 'a4512dba-212b-4139-b4bd-7dcdc5632f03' >}} describe climate trends for the USAPI. Globally and locally, observations of GHG concentrations, surface air temperatures, sea level, sea surface temperature, and ocean acidification show rising trends at an increasing rate. Trends in measures of rainfall, surface winds, and tropical cyclones are not as readily apparent. Patterns of climate variability characterize these measures and tend to mask long-term trends. A lack of high-quality, long-term observational records, particularly with respect to in situ stations, contributes to difficulties in discerning trends. To maintain and enhance our ability to assess environmental change, attention needs to be given to robust and sustained monitoring.
There are consistent subregional changes in the number of days with high winds. The global frequency of tropical cyclones (TCs) appears to be showing a slow downward trend since the early 1970s. In the Pacific region, long-term TC trends in frequency and intensity are relatively flat, with the record punctuated by as many active as inactive years.{{< tbib '142' 'a4512dba-212b-4139-b4bd-7dcdc5632f03' >}}
" href: https://data.globalchange.gov/report/nca4/chapter/hawaii-and-pacific-islands/finding/key-message-27-3.yaml identifier: key-message-27-3 ordinal: 3 process: "To frame this chapter, the regional leads wanted to maximize inclusiveness and represent the key sectoral interests of communities and researchers. To select sectors and a full author team, the coordinating lead author and regional chapter lead author distributed an online Google survey from September to October 2016. The survey received 136 responses representing Hawaiʻi and all the U.S.-Affiliated Pacific Islands (USAPI) jurisdictions; respondents identified which of the National Climate Assessment (NCA) sectors they were most interested in learning about with respect to climate change in the Pacific Islands and suggested representative case studies.{{< tbib '223' '884675c9-3e31-483d-b6b9-fd53b99875ae' >}} The five top sectors were picked as the focus of the chapter, and a total of eight lead authors with expertise in those sectors were invited to join the regional team. To solicit additional participation from potential technical contributors across the region, two informational webinars spanning convenient time zones across the Pacific were held; 35 people joined in. The webinars outlined the NCA history and process, as well as past regional reports and ways to participate in this Fourth National Climate Assessment (NCA4).
A critical part of outlining the chapter and gathering literature published since the Third National Climate Assessment (NCA3){{< tbib '224' 'dd5b893d-4462-4bb3-9205-67b532919566' >}} was done by inviting technical experts in the key sectors to participate in a half-day workshop led by each of the lead authors. A larger workshop centered on adaptation best practices was convened with participants from all sectors, as well as regional decision-makers. In all, 75 participants, including some virtual attendees, took part in the sectoral workshops on March 6 and 13, 2017. Finally, to include public concerns and interests, two town hall discussion events on March 6 and April 19, 2017, were held in Honolulu, Hawaiʻi, and Tumon, Guam, respectively. Approximately 100 participants attended the town halls. Throughout the refining of the Key Messages and narrative sections, authors met weekly both via conference calls and in person to discuss the chapter and carefully review evidence and findings. Technical contributors were given multiple opportunities to respond to and edit sections. The process was coordinated by the regional chapter lead and coordinating lead authors, as well as the Pacific Islands sustained assessment specialist.
" report_identifier: nca4 statement: 'The majority of Pacific island communities are confined to a narrow band of land within a few feet of sea level. Sea level rise is now beginning to threaten critical assets such as ecosystems, cultural sites and practices, economics, housing and energy, transportation, and other forms of infrastructure (very likely, very high confidence). By 2100, increases of 1–4 feet in global sea level are very likely, with even higher levels than the global average in the U.S.-Affiliated Pacific Islands (very likely, high confidence). This would threaten the food and freshwater supply of Pacific island populations and jeopardize their continued sustainability and resilience (likely, high confidence). As sea level rise is projected to accelerate strongly after mid-century, adaptation strategies that are implemented sooner can better prepare communities and infrastructure for the most severe impacts.
' uncertainties: 'Major uncertainties lie in understanding and projecting the future melting behavior of the Antarctic and Greenland ice sheets. To date, new observations attest to melting occurring at higher than expected rates. If this continues to be the case, it is plausible for future sea level rise to exceed even worst-case scenarios. Secondary feedbacks to warming, such as changes in the global thermohaline circulation; shifts in major weather elements, such as the intertropical convergence zone and the polar jet stream; and unexpected modes of heat distribution across the hemispheres risk complex responses in the climate system that are not well understood. Pacific climate variability is a governing element that amplifies many aspects of climate change, such as drought, sea level, storminess, and ocean warming. A number of mechanisms through which climate change might alter Pacific variability have been proposed on the basis of physical modeling, but our understanding of the variability remains low, and confidence in projected changes is also low. For instance, in any given Pacific region, our understanding of future TC occurrence, intensity, and frequency is low. Future physical responses to climate change that have not yet been described are possible. These uncertainties greatly limit our ability to identify the chronology of changes to expect in the future.
' uri: /report/nca4/chapter/hawaii-and-pacific-islands/finding/key-message-27-3 url: ~ - chapter_identifier: hawaii-and-pacific-islands confidence: 'There is high confidence that fisheries and the livelihoods they support are threatened by warmer ocean temperatures and ocean acidification. Widespread and multiyear coral reef bleaching and mortality are already occurring. It is likely, based on modeled SST projections, that by mid-century, bleaching will occur annually with associated mortality.
There is medium confidence in the projection of annual bleaching by mid-century, as it does not take into account any adaptation in corals.
There is high confidence that bleaching and rising seawater acidity will result in loss of reef structure, leading to lower fisheries yields and loss of coastal protection. This is deemed very likely because significant coral mortality has recently been observed in western Hawaiian coral reefs that suffered from the 2015 bleaching event. Further, the positive relationship between fish density and coral reef cover is well established. The magnitude of this impact depends on the extent that coral species exhibit adaptive or resilience capacity.
There is medium confidence that declines in oceanic fishery productivity of up to 15% and 50% are likely by mid-century and 2100, respectively. These declines are considered likely because we have seen related linkages between climate variability such as ENSO and the Pacific Decadal Oscillation and fisheries yields that provide an analog in some ways to global warming impacts. The uncertainty lies in our limited understanding of the linkages and feedbacks in the very complex oceanic food web. As temperate habitats warm, they will likely gain some tropical species, while the tropical habitats will likely only lose species.
' evidence: "The Key Message was developed based on input from an expert working group convened at the outset of this section development and supported by extensive literature.
Ocean warming: NCA3 documented historical increases in sea surface temperature (SST), and current levels in much of the region have now exceeded the upper range of background natural variation.{{< tbib '32' '081bdbe7-f95f-4708-b18c-e7bc797effa7' >}},{{
Ocean acidification: Atmospheric carbon dioxide levels recorded at Mauna Loa, Hawaiʻi, have recently exceeded 400 parts per million, and oceanic pH levels measured off Oʻahu have steadily declined from an annual average of about 8.11 to 8.07 over the past 25 years (data from Hawaiʻi Ocean Time Series, SOEST, University of Hawaiʻi) and are projected to decrease to 7.8 by 2100.{{< tbib '123' 'fa5d3ea3-a0ad-4418-b516-20c748528b2f' >}} As pH declines, it lowers the saturation level of aragonite (the form of calcium carbonate used by corals and many other marine organisms), reducing coral and shell growth.{{< tbib '125' '7ab1d9e1-75a1-48c5-8d85-02258496f919' >}} By the end of the century, aragonite saturation is projected to decline from a current level of 3.9 to 2.4, representing extremely marginal conditions for coral reef growth.{{< tbib '32' '081bdbe7-f95f-4708-b18c-e7bc797effa7' >}},{{
Bleaching events: These continue to occur—most recently over successive years—with widespread impacts.{{< tbib '45' 'be538e70-7c97-4680-a580-7ee398361090' >}},{{
Mortality: During the 2014–2015 bleaching events, coral mortality in western Hawaiʻi was estimated at 50%{{< tbib '45' 'be538e70-7c97-4680-a580-7ee398361090' >}} and over 90% at the pristine equatorial Jarvis Atoll.{{< tbib '156' '71443a23-b42f-4435-93ac-78d32df5bd30' >}}
Coral reef ecosystem impacts: Coral reef cover around the Pacific Islands region is projected to decline from the current average level of about 40% to 15%–30% by 2035 and 10%–20% by 2050.{{< tbib '123' 'fa5d3ea3-a0ad-4418-b516-20c748528b2f' >}} The loss of coral reef habitat is projected to reduce fish abundance and fisheries yields by 20%.{{< tbib '123' 'fa5d3ea3-a0ad-4418-b516-20c748528b2f' >}} Loss of coral reefs will result in increased coastal erosion.{{< tbib '23' '7350d7b3-6e95-4375-ba23-26756b441fc2' >}},{{
Insular fisheries: Insular fishes, including both coral reef fishes and more mobile, coastal pelagics (species such as mahi mahi and wahoo), are impacted both from declines in carrying capacity and loss from migration in response to temperature change. Taken together, declines in maximum catch potential exceeding 50% from late 20th century levels under the higher scenario are projected by 2100 for the exclusive economic zones of most islands in the central and western Pacific.{{< tbib '163' 'faaa3555-cab7-44a6-a71e-dc269d1b67ce' >}}
Oceanic fisheries: A number of studies have projected that ocean warming will result in lower primary productivity due to increased vertical stratification and loss of biodiversity as organisms move poleward.{{< tbib '129' 'd055c0df-2c85-4ee1-a3c6-8e6c79e425bd' >}},{{
To frame this chapter, the regional leads wanted to maximize inclusiveness and represent the key sectoral interests of communities and researchers. To select sectors and a full author team, the coordinating lead author and regional chapter lead author distributed an online Google survey from September to October 2016. The survey received 136 responses representing Hawaiʻi and all the U.S.-Affiliated Pacific Islands (USAPI) jurisdictions; respondents identified which of the National Climate Assessment (NCA) sectors they were most interested in learning about with respect to climate change in the Pacific Islands and suggested representative case studies.{{< tbib '223' '884675c9-3e31-483d-b6b9-fd53b99875ae' >}} The five top sectors were picked as the focus of the chapter, and a total of eight lead authors with expertise in those sectors were invited to join the regional team. To solicit additional participation from potential technical contributors across the region, two informational webinars spanning convenient time zones across the Pacific were held; 35 people joined in. The webinars outlined the NCA history and process, as well as past regional reports and ways to participate in this Fourth National Climate Assessment (NCA4).
A critical part of outlining the chapter and gathering literature published since the Third National Climate Assessment (NCA3){{< tbib '224' 'dd5b893d-4462-4bb3-9205-67b532919566' >}} was done by inviting technical experts in the key sectors to participate in a half-day workshop led by each of the lead authors. A larger workshop centered on adaptation best practices was convened with participants from all sectors, as well as regional decision-makers. In all, 75 participants, including some virtual attendees, took part in the sectoral workshops on March 6 and 13, 2017. Finally, to include public concerns and interests, two town hall discussion events on March 6 and April 19, 2017, were held in Honolulu, Hawaiʻi, and Tumon, Guam, respectively. Approximately 100 participants attended the town halls. Throughout the refining of the Key Messages and narrative sections, authors met weekly both via conference calls and in person to discuss the chapter and carefully review evidence and findings. Technical contributors were given multiple opportunities to respond to and edit sections. The process was coordinated by the regional chapter lead and coordinating lead authors, as well as the Pacific Islands sustained assessment specialist.
" report_identifier: nca4 statement: 'Fisheries, coral reefs, and the livelihoods they support are threatened by higher ocean temperatures and ocean acidification (very likely, high confidence).Widespread coral reef bleaching and mortality have been occurring more frequently, and by mid-century these events are projected to occur annually, especially if current trends in emissions continue (likely, medium confidence). Bleaching and acidification will result in loss of reef structure, leading to lower fisheries yields, and loss of coastal protection and habitat (very likely, very high confidence). Declines in oceanic fishery productivity of up to 15% and 50% of current levels are projected by mid-century and 2100, respectively, under the higher scenario (RCP8.5; likely, medium confidence).
' uncertainties: "A major uncertainty for coral reefs is whether they can evolve rapidly enough to keep up with the changing temperature and pH.{{< tbib '164' '06b7a4b5-9c7e-42de-8dee-c54d443a2af3' >}},{{
There is high confidence that climate change is having far-reaching effects on the land security, livelihood security, habitat security, and cultural food security of Indigenous peoples of the Pacific.
It is likely that most of these impacts will have negative effects on the cultural heritage of the Pacific island communities.
There is high confidence that traditional knowledge together with science will support the adaptive capacity of Pacific island communities to survive on their islands.
' evidence: "The research supporting this Key Message examines the impacts of climate change on the lands, territories, and resources of the Pacific region and its Indigenous communities.
It is foundational to highlight the interconnectedness and important familial relationship Indigenous peoples have with their lands, territories, and resources. Native Hawaiian attorneys and professors Sproat and Akutagawa discuss the health impacts and threats that climate change poses for Indigenous communities and their relationship with ancestral resources. Sproat states that “any such loss will result in the loss of culture.”{{< tbib '177' '9c017401-c8d2-4d9f-9d69-4a7bb247594b' >}} Further support is found in a community health assessment done by Akutagawa and others that states, “In traditional Hawaiian conceptions of health, personal harmony and well-being are deemed to stem from one’s relationship with the land, sea, and spiritual world”.{{< tbib '176' '85e07f9f-b899-4b21-8028-3a9c2d85d792' >}}
Governments and their support institutions are also sharing outcomes of projects they’ve initiated over the years that document not only the successes but also the challenges, observations, and lessons learned.{{< tbib '149' '567b51b3-07f8-4e75-81d5-76b394218947' >}},{{
In writing this Key Message, the authors considered the body of research focusing on the impacts of climate change on Pacific communities such as sea level rise,{{< tbib '104' 'b36fdfcb-d735-4cad-a0df-806725e7d8f4' >}},{{
There is very strong evidence that traditional knowledge is key to the resilience and adaptive capacity of Indigenous peoples of the Pacific.{{< tbib '21' '5db43854-3226-408c-a5ef-aa7898146f1f' >}},{{
To frame this chapter, the regional leads wanted to maximize inclusiveness and represent the key sectoral interests of communities and researchers. To select sectors and a full author team, the coordinating lead author and regional chapter lead author distributed an online Google survey from September to October 2016. The survey received 136 responses representing Hawaiʻi and all the U.S.-Affiliated Pacific Islands (USAPI) jurisdictions; respondents identified which of the National Climate Assessment (NCA) sectors they were most interested in learning about with respect to climate change in the Pacific Islands and suggested representative case studies.{{< tbib '223' '884675c9-3e31-483d-b6b9-fd53b99875ae' >}} The five top sectors were picked as the focus of the chapter, and a total of eight lead authors with expertise in those sectors were invited to join the regional team. To solicit additional participation from potential technical contributors across the region, two informational webinars spanning convenient time zones across the Pacific were held; 35 people joined in. The webinars outlined the NCA history and process, as well as past regional reports and ways to participate in this Fourth National Climate Assessment (NCA4).
A critical part of outlining the chapter and gathering literature published since the Third National Climate Assessment (NCA3){{< tbib '224' 'dd5b893d-4462-4bb3-9205-67b532919566' >}} was done by inviting technical experts in the key sectors to participate in a half-day workshop led by each of the lead authors. A larger workshop centered on adaptation best practices was convened with participants from all sectors, as well as regional decision-makers. In all, 75 participants, including some virtual attendees, took part in the sectoral workshops on March 6 and 13, 2017. Finally, to include public concerns and interests, two town hall discussion events on March 6 and April 19, 2017, were held in Honolulu, Hawaiʻi, and Tumon, Guam, respectively. Approximately 100 participants attended the town halls. Throughout the refining of the Key Messages and narrative sections, authors met weekly both via conference call and in person to discuss the chapter and carefully review evidence and findings. Technical contributors were given multiple opportunities to respond to and edit sections. The process was coordinated by the regional chapter lead and coordinating lead authors, as well as the Pacific Islands sustained assessment specialist.
" report_identifier: nca4 statement: 'Indigenous peoples of the Pacific are threatened by rising sea levels, diminishing future freshwater availability, and shifting ecosystem services. These changes imperil communities’ health, well-being, and modern livelihoods, as well as their familial relationships with lands, territories, and resources (likely, high confidence). Built on observations of climatic changes over time, the transmission and protection of traditional knowledge and practices, especially via the central role played by Indigenous women, are intergenerational, place-based, localized, and vital for ongoing adaptation and survival.
' uncertainties: 'There is no doubt that Indigenous communities of the Pacific are being impacted by climate change. However, the rate and degree of the impacts on the spiritual, relational, and ancestral connectedness varies from community to community and on the type of practice being impacted. This variable is difficult to document and express in certain circumstances. Additionally, the degree of the impact varies according to the livelihoods of the community and the specific climatic and socioeconomic and political circumstances of the island in question.
' uri: /report/nca4/chapter/hawaii-and-pacific-islands/finding/key-message-27-5 url: ~ - chapter_identifier: hawaii-and-pacific-islands confidence: 'There is medium confidence that climate change will yield compounding economic, environmental, social, and cultural costs. There is greater evidence of these compounding costs resulting from extreme events that are exacerbated by climate change.
There is high confidence that food and water insecurity will result in severe disruptions to livelihoods, including the displacement and relocation of island communities.
It is likely that the absence of interventions will result in the costly and lengthy rebuilding of communities and livelihoods and more displacement and relocation. Events have played out repeatedly across the region and have resulted in damage, disruptions, and displacements.
' evidence: "For Atlantic and eastern North Pacific hurricanes and western North Pacific typhoons, increases are projected in precipitation rates and intensity. The frequency of the most intense of these storms is projected to increase in the western North Pacific and in the eastern North Pacific (see also Key Message 3).{{< tbib '246' '52ce1b63-1b04-4728-9f1b-daee39af665e' >}} Studies indicate that Hawaiʻi will see an increased frequency of tropical cyclones (TCs) due to storm tracks shifting northward in the central North Pacific.{{< tbib '40' '9082a92d-e1be-4346-8657-7b172a8f91bc' >}},{{
The Climate Science Special Report (CSSR) summarizes extensive evidence that is documented in the climate science literature and is similar to statements made in NCA3 and international{{< tbib '106' 'f03117be-ccfe-4f88-b70a-ffd4351b8190' >}} assessments.{{< tbib '33' '75cf1c0b-cc62-4ca4-96a7-082afdfe2ab1' >}} More recent downscaling studies have further supported these assessments,{{< tbib '248' '4f1e7aa1-0c36-4220-ac77-7d55bcb33061' >}} though pointing out that the changes (future increased intensity and TC precipitation rates) will not necessarily occur in all basins.{{< tbib '246' '52ce1b63-1b04-4728-9f1b-daee39af665e' >}}
Damage from TCs is significant. Tropical Cyclone Evan struck Sāmoa in December 2012 and caused damage and losses of approximately $210 million dollars (dollar year not reported), representing 30% of its annual gross domestic product (GDP). Tropical Cyclone Pam struck Vanuatu, Tuvalu, and Kiribati in 2015; in Vanuatu, it killed 11 people and caused approximately $450 million (dollar year not reported) in damages and losses, equal to 64% of GDP.{{< tbib '196' '08f6548b-e879-45a6-97df-3790e804e73e' >}}
In the CSSR, future relative sea level rise as shown for the 3.3-feet (1 m) Interagency scenario in 2100 indicates that, because they are far from all glaciers and ice sheets, relative sea level rise in Hawai‘i and other Pacific islands due to any source of melting land ice is amplified by the static-equilibrium effects. Static-equilibrium effects on sea level are produced by the gravitational, elastic, and rotational effects of mass redistribution resulting from ice loss.{{< tbib '105' '3bae2310-7572-47e2-99a4-9e4276764934' >}}
Sea level rise across Hawaiʻi is projected to rise another 1–3 feet by the end of this century. Sea level rise has caused an increase in high tide floods associated with nuisance-level impacts. High tide floods are events in which water levels exceed the local threshold (set by the National Oceanic and Atmospheric Administration’s National Weather Service) for minor impacts. These events can damage infrastructure, cause road closures, and overwhelm storm drains. Along the Hawaiian coastline, the number of tidal flood days (all days exceeding the nuisance-level threshold) has also increased, with the greatest number occurring in 2002–2003. Continued sea level rise will present major challenges to Hawaiʻi’s coastline through coastal inundation and erosion. Seventy percent of Hawaiʻi’s beaches have already been eroded over the past century, with more than 13 miles of beach completely lost. Sea level rise will also affect Hawai‘i’s coastal storm water and wastewater management systems and is expected to cause extensive economic impacts through ecosystem damage and losses in property, tourism, and agriculture.{{< tbib '247' '2eff8dd3-b0da-474d-b7be-ba223baa8396' >}}
In the Pacific Islands region, population, urban centers, and critical infrastructure are concentrated along the coasts. This results in significant damages during inundation events. In December 2008, wind waves generated by extratropical cyclones, exacerbated by sea level rise, caused a series of inundation events in five Pacific island nations.{{< tbib '9' '7717dd13-7f6b-4b7c-ab84-571d50f7b8da' >}} An area of approximately 3,000 km in diameter was affected, impacting approximately 100,000 people. Across the islands, major infrastructure damage and crop destruction resulted, costing millions of dollars and impacting livelihoods, food security, and freshwater resources.
The increases in the frequency and intensity of climate change hazards, including cyclones, wind, rainfall, and flooding, pose an immediate danger to the Pacific Islands region. A decrease in the return times of extreme events, which will reduce the ability of systems to recover, will likely cause long-term declines in welfare.{{< tbib '181' 'dd36c0e3-b849-46c9-8685-dd76a465223a' >}} For small islands states, the damage costs of sea level rise are large in relation to the size of their economies.{{< tbib '194' '2e8e659c-1150-4516-b2c2-fd3176f9c641' >}},{{
The social science research on climate and conflict suggests a possible association between climate variability and change and conflict. Consensus or conclusive evidence of a causal link remains elusive. Hsiang et al. (2013){{< tbib '249' '6013994a-8717-4a99-935a-8a13800fcdc5' >}} find strong causal evidence linking climatic events to human conflict across a range of spatial scales and time periods and across all major regions of the world. They further demonstrate that the magnitude of climate influence is substantial.{{< tbib '249' '6013994a-8717-4a99-935a-8a13800fcdc5' >}} Specifically, large deviations from average precipitation and mild temperatures systematically increase the risk of many types of conflict (intergroup to interpersonal), often substantially. Hsiang and Burke (2014){{< tbib '250' 'e3a15302-b1ec-4bfe-9ac3-3a2cf23d3303' >}} describe their detailed meta-analysis, examining 50 rigorous quantitative studies, and find consistent support for a causal association between climatological changes and various conflict outcomes.{{< tbib '250' 'e3a15302-b1ec-4bfe-9ac3-3a2cf23d3303' >}} They note, however, that multiple mechanisms can explain this association and that the literature is currently unable to decisively exclude any proposed pathway between climatic change and human conflict.{{< tbib '249' '6013994a-8717-4a99-935a-8a13800fcdc5' >}}
Evidence of the impact of climate on livelihoods is also well established. Barnett and Adger (2003, 2007){{< tbib '191' '0dc9b00c-1fc7-43ee-bcb6-4c8e783e88f1' >}},{{
To frame this chapter, the regional leads wanted to maximize inclusiveness and represent the key sectoral interests of communities and researchers. To select sectors and a full author team, the coordinating lead author and regional chapter lead author distributed an online Google survey from September to October 2016. The survey received 136 responses representing Hawaiʻi and all the U.S.-Affiliated Pacific Islands (USAPI) jurisdictions; respondents identified which of the National Climate Assessment (NCA) sectors they were most interested in learning about with respect to climate change in the Pacific Islands and suggested representative case studies.{{< tbib '223' '884675c9-3e31-483d-b6b9-fd53b99875ae' >}} The five top sectors were picked as the focus of the chapter, and a total of eight lead authors with expertise in those sectors were invited to join the regional team. To solicit additional participation from potential technical contributors across the region, two informational webinars spanning convenient time zones across the Pacific were held; 35 people joined in. The webinars outlined the NCA history and process, as well as past regional reports and ways to participate in this Fourth National Climate Assessment (NCA4).
A critical part of outlining the chapter and gathering literature published since the Third National Climate Assessment (NCA3){{< tbib '224' 'dd5b893d-4462-4bb3-9205-67b532919566' >}} was done by inviting technical experts in the key sectors to participate in a half-day workshop led by each of the lead authors. A larger workshop centered on adaptation best practices was convened with participants from all sectors, as well as regional decision-makers. In all, 75 participants, including some virtual attendees, took part in the sectoral workshops on March 6 and 13, 2017. Finally, to include public concerns and interests, two town hall discussion events on March 6 and April 19, 2017, were held in Honolulu, Hawaiʻi, and Tumon, Guam, respectively. Approximately 100 participants attended the town halls. Throughout the refining of the Key Messages and narrative sections, authors met weekly both via conference call and in person to discuss the chapter and carefully review evidence and findings. Technical contributors were given multiple opportunities to respond to and edit sections. The process was coordinated by the regional chapter lead and coordinating lead authors, as well as the Pacific Islands sustained assessment specialist.
" report_identifier: nca4 statement: 'Climate change impacts in the Pacific Islands are expected to amplify existing risks and lead to compounding economic, environmental, social, and cultural costs (likely, medium confidence). In some locations, climate change impacts on ecological and social systems are projected to result in severe disruptions to livelihoods (likely, high confidence) that increase the risk of human conflict or compel the need for migration. Early interventions, already occurring in some places across the region, can prevent costly and lengthy rebuilding of communities and livelihoods and minimize displacement and relocation (likely, high confidence).
' uncertainties: "A key uncertainty remains the lack of a supporting, detectable anthropogenic signal in the historical data to add further confidence to some regional projections. As such, confidence in the projections is based on agreement among different modeling studies. Additional uncertainty stems from uncertainty in both the projected pattern and magnitude of future sea surface temperatures.{{< tbib '33' '75cf1c0b-cc62-4ca4-96a7-082afdfe2ab1' >}},{{
One study projects an increase in tropical cyclone frequency (TCF) of occurrence around the Hawaiian Islands but stipulates that TCF around the Hawaiian Islands is still very low in a warmed climate, so that a quantitative evaluation of the future change involves significant uncertainties.{{< tbib '40' '9082a92d-e1be-4346-8657-7b172a8f91bc' >}}
Uncertainties in reconstructed global mean sea level (GMSL) change relate to the sparsity of tide gauge records, particularly before the middle of the twentieth century, and to the use of a variety of statistical approaches to estimate GMSL change from these sparse records. Uncertainties in reconstructed GMSL change before the 20th century also relate to the lack of geological proxies (preserved physical characteristics of the past environment that can stand in for direct measurement) for sea level change, the interpretation of these proxies, and the dating of these proxies. Uncertainty in attribution relates to the reconstruction of past changes and the magnitude of natural variability in the climate.
Since NCA3, multiple approaches have been used to generate probabilistic projections of GMSL rise. These approaches are in general agreement. However, emerging results indicate that marine portions of the Antarctic ice sheet are more unstable than previously thought. The rate of ice sheet mass changes remains challenging to project.
In sea level rise projections, Antarctic contributions are amplified along U.S. coastlines, while Greenland contributions are dampened; regional sea level is projected to be higher than if driven by a more extreme Greenland contribution and a somewhat less extreme Antarctic contribution.{{< tbib '17' 'c66bf5a9-a6d7-4043-ad99-db0ae6ae562c' >}}
The degree to which climate variability and change impact conflict, and related causal pathways, remains uncertain. This is compounded by the fact that different types of conflict—social, political, civil, or violent—are conflated.{{< tbib '209' '657d9028-d5b7-4e0c-980e-dd71138c8bd7' >}},{{
Gemenne et al. (2014){{< tbib '208' '32ad430a-4769-4e16-8ece-c28d123504b0' >}} also note that the relationship between climate change and security comes from observation of past patterns and that present and projected climate change have no historical precedent. In effect, understanding past crises and adaptation strategies will no longer be able to help us understand future crises in a time of significant climate change.
The degree to which climate variability and change affect migration decisions made today also remains uncertain. This is in part due to the diverse scenarios that comprise climate migration, which themselves result from multiple drivers of migration.{{< tbib '251' 'b3626f1d-9cfa-469a-b52d-dce3c6a0dff0' >}} Burrows and Kinney (2016){{< tbib '251' 'b3626f1d-9cfa-469a-b52d-dce3c6a0dff0' >}} detail examples of climate extremes leading to migration conflicts since 2000, yet they note that there are surprisingly few case studies on recent climate extremes that lead to migration and conflict specifically, despite an increasing body of literature on the theory.
While researchers disagree as to the degree to which climate change drives conflict and migration and the causal pathways that connect them, there is agreement that further research is needed. Buhaug (2015){{< tbib '252' '9d9049c5-28b9-4029-a6b7-a18838dcdc69' >}} and Gemenne et al. (2014){{< tbib '208' '32ad430a-4769-4e16-8ece-c28d123504b0' >}} argue for research to develop a more refined theoretical understanding of possible indirect and conditional causal connections between climate change and, specifically, violent conflict.{{< tbib '252' '9d9049c5-28b9-4029-a6b7-a18838dcdc69' >}} Hsiang and Burke (2014){{< tbib '250' 'e3a15302-b1ec-4bfe-9ac3-3a2cf23d3303' >}} would like additional research that reduces the number of competing hypotheses that attempt to explain the overwhelming evidence that climatic variables are one of many important causal factors in human conflict.{{< tbib '250' 'e3a15302-b1ec-4bfe-9ac3-3a2cf23d3303' >}} Burrows and Kinney (2016){{< tbib '251' 'b3626f1d-9cfa-469a-b52d-dce3c6a0dff0' >}} explore the potential pathways linking climate change, migration, and increased risk of conflict and argue that future research should focus on other pathways by which climate variability and change are related to conflict, in addition to the climate–migration–conflict pathway. Kallis and Zografos (2014){{< tbib '209' '657d9028-d5b7-4e0c-980e-dd71138c8bd7' >}} seek greater understanding of the potential harm of certain climate change adaptation measures that have the potential to result in maladaptation by spurring conflict.
" uri: /report/nca4/chapter/hawaii-and-pacific-islands/finding/key-message-27-6 url: ~ - chapter_identifier: near-term-adaptation-needs-and-increased-resiliency confidence: 'There is high confidence that the amount of adaptation activity, in particular implementation activity, is increasing. There is less agreement and evidence regarding the consequences of this activity.
' evidence: "There exists extensive documentation in the gray literature of specific adaptation planning and implementation activities underway by local, state, regional, and federal agencies and jurisdictions. The literature also contains reports that attempt to provide an overview of these activities, such as the recent set of case studies in Vogel et. al. (2017).{{< tbib '14' '3c3cc09b-c2d7-4c52-bf8f-c064efa78e93' >}} Websites, such as those of the Georgetown Climate Center (http://www.georgetownclimate.org), provide summaries and examples of adaptation activities in the United States. The sectoral and regional chapters in this National Climate Assessment also provide numerous examples of adaptation planning and implementation activities. The literature also offers work that aims to provide surveys of large numbers of adaptation activity, such as Moser et. al. (2018){{< tbib '121' 'b47b4130-ce3f-4e3e-914d-443a5652abbb' >}} and Stults and Woodruff (2016).{{< tbib '164' '44dd3160-74d0-4173-8ca4-b503fcd93615' >}}
" href: https://data.globalchange.gov/report/nca4/chapter/near-term-adaptation-needs-and-increased-resiliency/finding/key-message-28-1.yaml identifier: key-message-28-1 ordinal: 1 process: 'The scope for this chapter was determined by the Fourth National Climate Assessment (NCA4) Federal Steering Committee, which is made up of representatives from the U.S. Global Change Research Program member agencies. The scope was also informed by research needs identified in the Third National Climate Assessment (NCA3). Authors for this NCA4 chapter were selected to represent a range of public- and private-sector perspectives and experiences relevant to adaptation planning and implementation.
This chapter was developed through technical discussions of relevant evidence and expert deliberation by chapter authors during teleconferences, e-mail exchanges, and a day-long in-person meeting. These discussions were informed by a comprehensive literature review of the evidence base for the current state of adaptation in the United States. The author team obtained input from outside experts in several important areas to supplement its expertise.
' report_identifier: nca4 statement: 'Adaptation planning and implementation activities are occurring across the United States in the public, private, and nonprofit sectors. Since the Third National Climate Assessment, implementation has increased but is not yet commonplace. (High Confidence)
' uncertainties: "While the amount of adaptation-related activity is clearly increasing, the lack of clear standards and the diverse lexicon used in different sectors make it difficult to systematically compare different adaptation activities at the level of outcomes across sectors and regions of the country. In addition, publicly available adaptation plans may never actually result in implementation. It is thus difficult to provide a quantitative assessment of the increase in adaptation activity other than just counting plans and initiatives. Given the reliance on small-sample surveys, judgments about the distribution of adaptation actions across categories have potentially large errors that are difficult to estimate. In addition, it is difficult to assess the contribution of these activities to concrete outcomes such as risk reduction or current and future improvements to well-being, security, and environmental protection.{{< tbib '130' 'dbb9cf98-a2e1-4392-b1f9-38d00259ecdf' >}} There also exists little gap analysis that compares any given set of adaptation activities with what might be appropriate according to some normative standard or what might be reasonably achieved. Thus, while adaptation activities are clearly increasing in the United States, scant evidence exists for judging their consequences.
" uri: /report/nca4/chapter/near-term-adaptation-needs-and-increased-resiliency/finding/key-message-28-1 url: ~ - chapter_identifier: near-term-adaptation-needs-and-increased-resiliency confidence: "There is high confidence that most organizations’ planning is currently based on extensions from the record of local climate conditions.{{< tbib '169' '60233f20-d45f-4086-ada7-00dbd47712c3' >}}
" evidence: "The assumption that the historical record of events and variability will be the same in the future is called the stationarity assumption{{< tbib '27' 'c52f2539-9c5e-4ead-b8b7-f1884c5d662e' >}} and has guided planning for climate and weather events in most places for most of recorded history. The evidence is strong that the stationarity assumption is no longer valid for all impacts and variability in all locations, because climate change is altering both the events and their variability.{{< tbib '3' '666daffe-2c3b-4e2d-9157-16b989860618' >}},{{
The scope for this chapter was determined by the Fourth National Climate Assessment (NCA4) Federal Steering Committee, which is made up of representatives from the U.S. Global Change Research Program member agencies. The scope was also informed by research needs identified in the Third National Climate Assessment (NCA3). Authors for this NCA4 chapter were selected to represent a range of public- and private-sector perspectives and experiences relevant to adaptation planning and implementation.
This chapter was developed through technical discussions of relevant evidence and expert deliberation by chapter authors during teleconferences, e-mail exchanges, and a day-long in-person meeting. These discussions were informed by a comprehensive literature review of the evidence base for the current state of adaptation in the United States. The author team obtained input from outside experts in several important areas to supplement its expertise.
' report_identifier: nca4 statement: 'Successful adaptation has been hindered by the assumption that climate conditions are and will be similar to those in the past. Incorporating information on current and future climate conditions into design guidelines, standards, policies, and practices would reduce risk and adverse impacts. (High Confidence)
' uncertainties: "While significant uncertainties can exist in estimating the extent to which current variability differs from historic observations in any particular location, there is robust evidence that such differences do occur in many locations (see Ch. 18: Northeast; Ch. 19: Southeast; Ch. 20: U.S. Caribbean; Ch. 21: Midwest; Ch. 22: N. Great Plains; Ch. 23: S. Great Plains; Ch. 24: Northwest; Ch. 25: Southwest; Ch. 26: Alaska; and Ch. 27: Hawaiʻi & Pacific Islands).{{< tbib '5' '29960c69-6168-4fb0-9af0-d50bdd91acd3' >}},{{
Significant agreement and strong evidence provide high confidence that adaptation is a form of iterative risk management and that this is an appropriate framework for understanding, addressing, and communicating climate-related risks.{{< tbib '33' '7f8b90be-c5d1-43b5-8b7f-a485ef08c7ec' >}}
" evidence: "Evidence from a large body of literature and observations of experience support the judgment that iterative risk management is a useful framework (e.g., National Research Council 2009, America's Climate Choices 2010, Kunreuther et al. 2012{{< tbib '142' '7ab8b14a-38c7-4128-b0e3-fe1ab65edac0' >}},{{
The scope for this chapter was determined by the Fourth National Climate Assessment (NCA4) Federal Steering Committee, which is made up of representatives from the U.S. Global Change Research Program member agencies. The scope was also informed by research needs identified in the Third National Climate Assessment (NCA3). Authors for this NCA4 chapter were selected to represent a range of public- and private-sector perspectives and experiences relevant to adaptation planning and implementation.
This chapter was developed through technical discussions of relevant evidence and expert deliberation by chapter authors during teleconferences, e-mail exchanges, and a day-long in-person meeting. These discussions were informed by a comprehensive literature review of the evidence base for the current state of adaptation in the United States. The author team obtained input from outside experts in several important areas to supplement its expertise.
' report_identifier: nca4 statement: 'Adaptation entails a continuing risk management process; it does not have an end point. With this approach, individuals and organizations of all types assess risks and vulnerabilities from climate and other drivers of change (such as economic, environmental, and societal), take actions to reduce those risks, and learn over time. (High Confidence)
' uncertainties: 'The literature and practice of climate change are undergoing a process of maturation and convergence. The process began with many organizations and sectors developing their own approaches and terminology in response to climate risks, meaning that a wide variety of approaches still exist in the field. We believe that the field will progress and converge on the most effective approaches, including iterative risk management. But this convergence is still in process, and the outcome remains uncertain.
' uri: /report/nca4/chapter/near-term-adaptation-needs-and-increased-resiliency/finding/key-message-28-3 url: ~ - chapter_identifier: near-term-adaptation-needs-and-increased-resiliency confidence: 'There is suggestive evidence that provides medium confidence that many proactive adaptation actions offer significant benefits that exceed their costs. However, because of a small sample size and insufficient evaluation, it is in general hard to know the extent to which this is true in any particular case. There is strong agreement that evaluating adaptation involves consideration of a wide range of measures of social well-being.
' evidence: "Both limited field applications and literature reviews highlight adaptation co-benefits, including those associated with equity considerations.{{< tbib '83' '971185c1-a31f-4c15-8454-57f273b4ed33' >}} Near-term benefits are assessed from observations of adaptation results, as well as from comparisons to similar situations without such responses; longer-term benefits are generally assessed from projections.
" href: https://data.globalchange.gov/report/nca4/chapter/near-term-adaptation-needs-and-increased-resiliency/finding/key-message-28-4.yaml identifier: key-message-28-4 ordinal: 4 process: 'The scope for this chapter was determined by the Fourth National Climate Assessment (NCA4) Federal Steering Committee, which is made up of representatives from the U.S. Global Change Research Program member agencies. The scope was also informed by research needs identified in the Third National Climate Assessment (NCA3). Authors for this NCA4 chapter were selected to represent a range of public- and private-sector perspectives and experiences relevant to adaptation planning and implementation.
This chapter was developed through technical discussions of relevant evidence and expert deliberation by chapter authors during teleconferences, e-mail exchanges, and a day-long in-person meeting. These discussions were informed by a comprehensive literature review of the evidence base for the current state of adaptation in the United States. The author team obtained input from outside experts in several important areas to supplement its expertise.
' report_identifier: nca4 statement: 'Proactive adaptation initiatives—including changes to policies, business operations, capital investments, and other steps—yield benefits in excess of their costs in the near term, as well as over the long term (medium confidence). Evaluating adaptation strategies involves consideration of equity, justice, cultural heritage, the environment, health, and national security (high confidence).
' uncertainties: 'Benefits are based on understanding the relevant systems so that one can compare similar cases and construct counterfactuals. Such understanding is excellent for many engineered systems (for example, how a storm drain performs under various rainfall scenarios) but is less robust for many biological systems. Benefit–cost ratios can have large uncertainties associated with estimates of costs, the projection of benefits, and the economic valuation of benefits. In addition, because expected differences in benefit–cost ratios are sufficiently large and the number of current examples is sufficiently low, there are large uncertainties in applying results from one case to another.
' uri: /report/nca4/chapter/near-term-adaptation-needs-and-increased-resiliency/finding/key-message-28-4 url: ~ - chapter_identifier: near-term-adaptation-needs-and-increased-resiliency confidence: 'There is significant agreement that provides high confidence, in at least some cases, that both 1) mainstreaming climate information into existing risk management and 2) creating enabling environments and institutions to improve adaptation capacity, implementation, and evaluation reduce risk, produce co-benefits across communities and sectors, and help secure economic investments into the future.
' evidence: "There is significant agreement, but only case study evidence, that effective adaptation can be realized by mainstreaming.{{< tbib '100' '40cd1072-ac17-4dfa-ba98-a554bf1a0458' >}},{{
The scope for this chapter was determined by the Fourth National Climate Assessment (NCA4) Federal Steering Committee, which is made up of representatives from the U.S. Global Change Research Program member agencies. The scope was also informed by research needs identified in the Third National Climate Assessment (NCA3). Authors for this NCA4 chapter were selected to represent a range of public- and private-sector perspectives and experiences relevant to adaptation planning and implementation.
This chapter was developed through technical discussions of relevant evidence and expert deliberation by chapter authors during teleconferences, e-mail exchanges, and a day-long in-person meeting. These discussions were informed by a comprehensive literature review of the evidence base for the current state of adaptation in the United States. The author team obtained input from outside experts in several important areas to supplement its expertise.
' report_identifier: nca4 statement: 'Integrating climate considerations into existing organizational and sectoral policies and practices provides adaptation benefits. Further reduction of the risks from climate change can be achieved by new approaches that create conditions for altering regulatory and policy environments, cultural and community resources, economic and financial systems, technology applications, and ecosystems. (High Confidence)
' uncertainties: 'It is not well understood how community acceptance of needed adaptations develops. This presents both a barrier to the implementation of adaptation measures and an opportunity for additional research into ways to close this gap in understanding. Additionally, a need exists to clarify the co-benefits of addressing multiple threats and opportunities. Effective adaptation also depends on networks of collaboration among researchers and practitioners and the long-term support of monitoring networks. The sustainability of both types of networks is a major uncertainty. Their effectiveness is both an uncertainty and major research need.
' uri: /report/nca4/chapter/near-term-adaptation-needs-and-increased-resiliency/finding/key-message-28-5 url: ~