US National Climate Research Articles

Quantifying the Role of Ocean Dynamics in SST Variability across GCMs and Observations

Abstract Midlatitude SSTs forced by mesoscale oceanic processes can affect the large-scale atmosphere, pointing to the ocean's crucial role outside the tropics. Previous studies have shown oceanic mesoscale processes' effect on global and regional climate variability. This study quantifies the local contribution of ocean dynamics to mixed-layer temperature across the globe by directly estimating the ocean heat flux divergence resolved by state-of-the-art ocean reanalysis, eddy-resolving, and eddy-parameterized versions of two US national climate models and indirectly from air-sea flux satellite-based estimates. Our results show that the eddy-resolving climate simulations resolve mixed-layer temperature variances that are larger and closer to those inferred from observations than both their eddy-parameterized counterparts and ECCO over much of the extratropics. The observations and the eddy-resolving models indicate a more significant role of ocean dynamics in the mixed layer temperature variability than the surface fluxes over most extratropics compared to their eddy-parameterized versions. A frequency domain analysis shows that the better-resolved ocean mesoscale and thermal gradients enhance the variance over timescale from two months to thirty years. Results show agreement in the ocean's contribution among satellite-based estimates, ocean reanalysis products, and ocean eddy-resolving simulations. At the same time, differences emerge for ECCO and the eddy-parameterized models, suggesting that surface fluxes account for a larger fraction of the mixed layer temperature variability in most of the extratropics.

New Assessment Methods of Future Conditions for Main Vulnerabilities and Risks from Climate Change

The US National Climate Assessment, published in 2018, states that “Earth’s climate is now changing faster than at any point in the history of modern civilization, primarily as a result of human activities” [...]

The Role of Cooling Centers in Protecting Vulnerable Individuals from Extreme Heat.

The Role of Cooling Centers in Protecting Vulnerable Individuals from Extreme Heat.

Status of Mean Sea Level Rise around the USA (2020)

The potential threats to the USA from current and projected sea level rise are significant, with profound environmental, social and economic consequences. This current study continues the refinement and improvement in analysis techniques for sea level research beyond the Fourth US National Climate Assessment (NCA4) report by incorporating further advancements in the time series analysis of long tide gauge records integrated with an improved vertical land motion (VLM) assessment. This analysis has also been synthesised with an updated regional assessment of satellite altimetry trends in the sea margins fringing the USA. Coastal margins more vulnerable to the threats posed by rising sea levels are those in which subsidence is prevalent, higher satellite altimetry trends are evident and higher ‘geocentric’ velocities in mean sea level are being observed. The evidence from this study highlights key spatial features emerging in 2020, which highlight the northern foreshore of the Gulf Coast and along the east coast of the USA south of the Chesapeake Bay region being more exposed to the range of factors exacerbating threats from sea level rise than other coastlines at present. The findings in this study complement and extend sea level research beyond NCA4 to 2020.

Recent Climate Changes Across the Great Plains and Implications for Natural Resource Management Practices

The Great Plains region plays an important role in providing water and land resources and habitat for wildlife and livestock, crops, energy production, and other critical ecosystem services to support rural livelihoods. The semiarid conditions of the region and tight coupling of livelihood enterprises with ecosystem services creates a situation of increased sensitivity to climate changes and enhanced vulnerability among the rural communities and Native American nations across the region. Recent climate conditions associated with warming trends, and altered atmospheric flows have resulted in rapid onset of drought conditions and other extreme weather events across the region that are changing seasonal patterns of temperature and precipitation and warming trends. Projected climate changes provided in the fourth US National Climate Assessment indicate that potential warming and variability of precipitation will further increase drought and extreme weather events.Recent research and assessment efforts of current and projected climate changes in the Great Plains indicate that rural communities and ecosystems are becoming more vulnerable to changes associated with warming trends, droughts, and increased variability in precipitation. These climate changes are having differential impacts on ecosystem services that are critical to livelihood enterprises. Strategies for how resource managers and the research community can better collaborate and more effectively codesign and coproduce efforts to understand and to respond to these challenges are needed.

Observations of greenhouse gases as climate indicators

Humans have significantly altered the energy balance of the Earth’s climate system mainly not only by extracting and burning fossil fuels but also by altering the biosphere and using halocarbons. The 3rd US National Climate Assessment pointed to a need for a system of indicators of climate and global change based on long-term data that could be used to support assessments and this led to the development of the National Climate Indicators System (NCIS). Here we identify a representative set of key atmospheric indicators of changes in atmospheric radiative forcing due to greenhouse gases (GHGs), and we evaluate atmospheric composition measurements, including non-CO2 GHGs for use as climate change indicators in support of the US National Climate Assessment. GHG abundances and their changes over time can provide valuable information on the success of climate mitigation policies, as well as insights into possible carbon-climate feedback processes that may ultimately affect the success of those policies. To ensure that reliable information for assessing GHG emission changes can be provided on policy-relevant scales, expanded observational efforts are needed. Furthermore, the ability to detect trends resulting from changing emissions requires a commitment to supporting long-term observations. Long-term measurements of greenhouse gases, aerosols, and clouds and related climate indicators used with a dimming/brightening index could provide a foundation for quantifying forcing and its attribution and reducing error in existing indicators that do not account for complicated cloud processes.

Indicators and monitoring systems for urban climate resiliency

Cities in the USA and around the world have begun to take an active role in responding to climate change. A central requirement for effective urban climate strategies is the capacity to understand and measure how the climate is changing, the physical, environmental, and social impacts of the changes, and whether adaptation and resiliency policies and programs put in place in response are working. The objective of this paper is to review and assess how urban climate change and resiliency efforts can be measured and to define what might serve as meaningful indicator and monitoring protocols. The New York City Panel on Climate Change (NPCC) is used as a case study along with a reviews of the emerging literature of urban climate change indicators to analyze the requirements and processes needed for a successful urban climate resiliency indicator and monitoring (I and M) system. In the paper, the basic requirements of a proposed Urban Climate Resilience Indicators and Monitoring System are presented. A specific illustration of an I and M system for tracking the urban heat island highlights challenges as well as potential solutions embedded within such systems. Discussions how these protocols can be translated to other locales and settings, as well as the relationship to the US National Climate Assessment indicator process, are presented.

The Relationship between Ambient Temperature and Sickle Cell Disease-Related Hospital Admissions in South Carolina

BackgroundSickle cell disease (SCD) is the most common inherited blood disorder in the United States and impacts millions of people globally. Climate change may significantly impact the health of these individuals; however to date, very limited research has examined the relationship between weather and sickle cell disease hospitalizations.MethodsWe evaluated the association between temperature and SCD-related hospital admissions among residents of South Carolina (SC) between 2003 and 2006. Daily temperature data were obtained from the US National Climatic Data Center for the most proximal weather station to each patient's residential address at the time of hospital admission. We restricted to first hospitalization for each patient. We used a semi-symmetric bidirectional case-crossover design to examine the relationship between hospital admissions and temperatures (continuous, extreme high and low temperatures) for 0 to 7 days prior (for case period) and an equivalent 7 days during the same month. Conditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs).ResultsAmong 1,937 individuals with at least one SCD hospital admission, the mean age was 24 years, and the median annual household income in the census tract of residence was about $37,000. The OR between hospital admission and temperature on the day prior to hospital admission was 1.01 (95%CI: 0.99,1.03), the OR for temperatures above 80 degrees F on the day prior was OR: 1.38 (95%CI:0.95,2.01), and for temperatures below 32 degrees F on the day was OR was 1.00 (95%CI:0.66,1.50). The associations for all other time windows that we investigated were similar.ConclusionsIn this dataset of SCD-related hospital admissions, we observed no strong relationship between temperature and hospital admission, however a weak positive relationship was observed for temperatures below freezing on days immediately prior to the hospital admission. Further investigation is warranted.

Evaluation of historical CMIP6 model simulations of extreme precipitation over contiguous US regions

Simulated historical precipitation is evaluated for Coupled Model Intercomparison Project Phase 6 (CMIP6) models using precipitation indices defined by the Expert Team on Climate Change Detection and Indices. The model indices are evaluated against corresponding indices from the CPC unified gauge-based analyses of precipitation over seven geographical regions across the contiguous US (CONUS). The regions assessed match those in recent US National Climate Assessment Reports. To estimate observational uncertainty, precipitation indices for three other observational datasets (HadEx2, Livneh and PRISM) are evaluated against the CPC analyses. Both the moderate and extreme mean precipitation intensities are overestimated over the western CONUS and underestimated in the areas of the Central Great Plains (CGP) in most CMIP6 models tested. Most CMIP6 models overestimate the mean and variability of wet spell durations and underestimate the mean and variability of dry spell durations across the CONUS. Biases in interannual variability of most of the indices have similar patterns to those in corresponding mean biases. The median and interquartile model spreads in CMIP6 model biases are clearly smaller than those in CMIP5 model biases for wet spell durations. Multimodel medians of CMIP6 (CMIP6-MMM) and CMIP5 (CMIP5-MMM) have similar biases in climatology and variability but biases tend to be smaller in CMIP6-MMM. Depending on the index, extreme precipitation is slightly better in parts of the eastern half of the CONUS in CMIP6-MMM, otherwise, the biases in climatology and variability are similar to CMIP5-MMM. CMIP6-MMM performs better than individual models and even observational datasets in some cases. Differences between observational datasets for most indices are comparable to the CMIP6 interquartile model spread. The better-performing observational and model datasets are different in different parts of the CONUS.

A framework for national climate indicators

Indicators have been proposed as critical elements for sustained climate assessment. Indicators provide a foundation for assessing change on an ongoing basis and presenting that information in a manner that is relevant to a broad range of decisions. As part of a sustained US National Climate Assessment, a pilot indicator system was implemented, informed by recommendations and (Kenney et al. 2014; Janetos and Kenney 2015; Kenney et al. Clim Chang 135(1):85–96, 2016). This paper extends this work to recommend a framework and topical categories for a system of climate indicators for the nation. We provide an overview of the indicator system as a whole: its goals, the design criteria for the indicators and the system as a whole, the selection of sectors, the use of conceptual models to transparently identify relevant indicators, examples of the actual indicators proposed, our vision for how the overall network can be used, and how it could evolve over time. Individual papers as part of this special issue provide system or sector-specific details as to how to operationalize the conceptual framework; these recommendations do not imply any decisions that are made ultimately by US federal agencies.

Climatological study of the Boundary-layer air Stagnation Index for China and its relationship with air pollution

Abstract. The Air Stagnation Index (ASI) is a vital meteorological measure of the atmosphere's ability to dilute air pollutants. The original metric adopted by the US National Climatic Data Center (NCDC) is found to be not very suitable for China, because the decoupling between the upper and lower atmospheric layers results in a weak link between the near-surface air pollution and upper-air wind speed. Therefore, a new threshold for the ASI–Boundary-layer air Stagnation Index (BSI) is proposed, consisting of daily maximal ventilation in the atmospheric boundary layer, precipitation, and real latent instability. In the present study, the climatological features of the BSI are investigated. It shows that the spatial distribution of the BSI is similar to the ASI; that is, annual mean stagnations occur most often in the northwestern and southwestern basins, i.e., the Xinjiang and Sichuan basins (more than 180 days), and least over plateaus, i.e., the Qinghai–Tibet and Yunnan plateaus (less than 40 days). However, the seasonal cycle of the BSI is changed. Stagnation days under the new metric are observed to be maximal in winter and minimal in summer, which is positively correlated with the air pollution index (API) during 2000–2012. The correlations between the BSI and the concentration of fine particulate matter (PM2.5) during January 2013 and November to December in 2015–2017 of Beijing are also investigated. It shows that the BSI matches the day-by-day variation of PM2.5 concentration very well and is able to catch the haze episodes.

Effective inundation of continental United States communities with 21st century sea level rise

Recurrent, tidally driven coastal flooding is one of the most visible signs of sea level rise. Recent studies have shown that such flooding will become more frequent and extensive as sea level continues to rise, potentially altering the landscape and livability of coastal communities decades before sea level rise causes coastal land to be permanently inundated. In this study, we identify US communities that will face effective inundation—defined as having 10% or more of livable land area flooded at least 26 times per year—with three localized sea level rise scenarios based on projections for the 3rd US National Climate Assessment. We present these results in a new, online interactive tool that allows users to explore when and how effective inundation will impact their communities. In addition, we identify communities facing effective inundation within the next 30 years that contain areas of high socioeconomic vulnerability today using a previously published vulnerability index. With the Intermediate-High and Highest sea level rise scenarios, 489 and 668 communities, respectively, would face effective inundation by the year 2100. With these two scenarios, more than half of communities facing effective inundation by 2045 contain areas of current high socioeconomic vulnerability. These results highlight the timeframes that US coastal communities have to respond to disruptive future inundation. The results also underscore the importance of limiting future warming and sea level rise: under the Intermediate-Low scenario, used as a proxy for sea level rise under the Paris Climate Agreement, 199 fewer communities would be effectively inundated by 2100.

Assessing decision support systems and levels of confidence to narrow the climate information “usability gap”

This article focuses on the implications for the US National Climate Assessment (NCA) of diversifying information needs to support climate change risk management. It describes how the Third US National Climate Assessment (NCA3) evolved to begin to narrow the gap between information from climate and impact scientists and “intermediaries” (individuals who have expertise in climate science, communication, and decision-support processes)–who are sometimes collectively described as “producers” in this article–and the decision-making needs of a wide range of “users” (individuals involved in advising or making a wide range of policy and management decisions). One step in the evolution of the NCA3 included adding a chapter to assess decision-support tools and systems being used in climate-related decisions. Another involved efforts to improve characterization of the level of confidence of NCA3 authors in their findings to help decision-makers and their advisors differentiate well-established and more preliminary conclusions. This paper lays out an argument for increasing the role of the NCA in assessing decision-support systems in the Fourth Assessment (NCA4) and the Sustained Assessment. It also briefly reviews approaches and potential next steps related to characterizing uncertainty and communicating confidence intended to improve application of assessment findings by decisionmakers.

Engagement with indigenous peoples and honoring traditional knowledge systems

The organizers of the 2014 US National Climate Assessment (NCA) made a concerted effort to reach out to and collaborate with Indigenous peoples, resulting in the most comprehensive information to date on climate change impacts to Indigenous peoples in a US national assessment. Yet, there is still much room for improvement in assessment processes to ensure adequate recognition of Indigenous perspectives and Indigenous knowledge systems. This article discusses the process used in creating the Indigenous Peoples, Land, and Resources NCA chapter by a team comprised of tribal members, agencies, academics, and nongovernmental organizations, who worked together to solicit, collect, and synthesize traditional knowledges and data from a diverse array of Indigenous communities across the US. It also discusses the synergy and discord between traditional knowledge systems and science and the emergence of cross-cutting issues and vulnerabilities for Indigenous peoples. The challenges of coalescing information about climate change and its impacts on Indigenous communities are outlined along with recommendations on the types of information to include in future assessment outputs. We recommend that future assessments – not only NCA, but other relevant local, regional, national, and international efforts aimed at the translation of climate information and assessments into meaningful actions – should support integration of Indigenous perspectives in a sustained way that builds respectful relationships and effectively engages Indigenous communities. Given the large number of tribes in the US and the current challenges and unique vulnerabilities of Indigenous communities, a special report focusing solely on climate change and Indigenous peoples is warranted.

Aspirations and common tensions: larger lessons from the third US national climate assessment

The Third US National Climate Assessment (NCA3) was produced by experts in response to the US Global Change Research Act of 1990. Based on lessons learned from previous domestic and international assessments, the NCA3 was designed to speak to a broad public and inform the concerns of policy- and decision-makers at different scales. The NCA3 was also intended to be the first step in an ongoing assessment process that would build the nation’s capacity to respond to climate change. This concluding paper draws larger lessons from the insights gained throughout the assessment process that are of significance to future US and international assessment designers. We bring attention to process and products delivered, communication and engagement efforts, and how they contributed to the sustained assessment. Based on areas where expectations were exceeded or not fully met, we address four common tensions that all assessment designers must confront and manage: between (1) core assessment ingredients (knowledge base, institutional set-up, principled process, and the people involved), (2) national scope and subnational adaptive management information needs, (3) scope, complexity, and manageability, and (4) deliberate evaluation and ongoing learning approaches. Managing these tensions, amidst the social and political contexts in which assessments are conducted, is critical to ensure that assessments are feasible and productive, while its outcomes are perceived as credible, salient, and legitimate.

Innovations in assessment and adaptation: building on the US National Climate Assessment

Well-targeted scientific assessments can support a range of decision-making processes, and contribute meaningfully to a variety of climate response strategies. This paper focuses on opportunities for climate assessments to be used more effectively to enhance adaptive capacity, particularly drawing from experiences with the third US National Climate Assessment (NCA3). We discuss the evolution of thinking about adaptation as a process and the importance of societal values, as well as the role of assessments in this evolution. We provide a rationale for prioritizing future assessment activities, with an expectation of moving beyond the concept of climate adaptation as an explicit and separable activity from Bnormal^ planning and implementation in the future. Starting with the values and resources that need to be protected or developed by communities rather than starting with an analysis of changes in climate drivers can provide opportunities for reframing climate issues in ways that are likely to result in more positive outcomes. A critical part of successful risk management is monitoring and evaluating the systems of interest to decision-makers and the effectiveness of interventions following integration of climate considerations into ongoing strategic planning activities and implementation. Increasingly this will require consideration of path dependency and coincident events.We argue that climate adaptation is a transitional process that bridges the gap between historically time-testedways of doing business and the kinds of decision processes that may be required in the future, and that scientific assessments will be increasingly central to these transitions in decision processes over time.

The third national climate assessment’s coastal chapter: the making of an integrated assessment

Coastal areas are on the front lines of the impacts of climate change. The immediate impacts of temperature, precipitation and sea-level change affect rich but already threatened ecological systems and the most populated, highly developed, and economically vibrant regions of human activity on the planet. The specific vulnerabilities, impacts and adaptation options and activities vary greatly across the coastal areas of the US. The charge given to the coastal chapter team of the third US National Climate Assessment (NCA3, released in May 2014) was to discern the key vulnerabilities and most important cross-cutting concerns across the extensive coastline of the US. This paper is a reflection on what the coastal chapter team accomplished and how it was done (including author selection, staff support, technical inputs, the chapter development process, within- and cross-chapter integration, the review process, the delivery and high-impact release, the timeline of key assessment steps, and evaluation of the chapter development process). It concludes with eight lessons that might inform the activities of future collaborative author teams writing transdisciplinary, integrated assessment reports.

Building a sustained climate assessment process

The leaders and authors of the Third US National Climate Assessment (NCA3) developed new modes of engaging academia, the private sector, government agencies and civil society to support their needs for usable, rigorous, and timely information and better connect science and decision-making. A strategic vision for assessment activities into the future was built during the NCA3 process, including recommendations on how to establish a sustained assessment process that would integrate evolving scientific understanding into decision making to manage the risks of climate change over time. This vision includes a collaborative assessment process that involves partnerships across a diverse and widely distributed set of non-governmental and governmental entities. The new approach to assessments would produce timely, scientifically sound climate information products and processes, rather than focusing on the production of single quadrennial synthesis reports. If properly implemented, a sustained assessment would be more efficient and cost-effective, avoiding the painful and time-consuming process of beginning the assessment process anew every 4 years. This ongoing assessment would also encourage scientific and social innovations and explore new insights and opportunities, building the capacity to advance the development and delivery of climate information to meet societal requirements and benefit from scientific opportunities.

U.S. National climate assessment gaps and research needs: overview, the economy and the international context

A number of knowledge gaps and research priorities emerged during the third US National Climate Assessment (NCA3). Several are also gaps in the latest IPCC WG2 report. These omissions reflect major gaps in the underlying research base from which these assessments draw. These include the challenge of estimating the costs and benefits of climate change impacts and responses to climate change and the need for research on climate impacts on important sectors such as manufacturing and services. Climate impacts also need to be assessed within an international context in an increasingly connected and globalized world. Climate change is being experienced not only through changes within a locality but also through the impacts of climate change in other regions connected through trade, prices, and commodity chains, migratory species, human mobility and networked communications. Also under-researched are the connections and tradeoffs between responses to climate change at or across different scales, especially between adaptation and mitigation or between climate responses and other environmental and social policies. This paper discusses some of these research priorities, illustrating their significance through analysis of economic and international connections and case studies of responses to climate change. It also critically reflects on the process of developing research needs as part of the assessment process.

Building community, credibility and knowledge: the third US National Climate Assessment

Assessments that are designed to be credible and useful in the eyes of potential users must rigorously evaluate the state of knowledge but also address the practical considerations— politics, economics, institutions, and procedures—that affect real-world decision processes. The Third US National Climate Assessment (NCA3) authors integrated a vast array of sources of scientific information to understand what natural, physical and social systems are most at risk from climate change. They were challenged to explore some of the potentially substantial sources of risk that occur at the intersections of social, economic, biological, and physical systems. In addition, they worked to build bridges to other ways of knowing and other sources of knowledge, including intuitive, traditional, cultural, and spiritual knowledge. For the NCA3, inclusion of a broad array of people with on-the-ground experience in various communities, sectors and regions helped in identifying issues of practical importance. The NCA3 was more than a climate assessment; it was also an experiment in testing theories of coproduction of knowledge. A deliberate focus on the assessment process as well as the products yielded important outcomes. For example, encouraging partnerships and engagement with existing networks increased learning and made the idea of a sustained assessment more realistic. The commitment to building an assessment focused on mutual learning, transparency, and engagement contributed to the credibility and legitimacy of the product, and the saliency of its contents.