Title: Fourth National Climate Assessment, Chapter 8: Climate Effects

Agency: U.S. Global Change Research Program

Comments Close: January 31st, 2018

Summary Index: 

  1. Purpose
  2. Context: The National Climate Assessment & US Global Change Research Program; Chapter 8 Writing Process; Tips for Chapter Review
  3. Details: Key Messages; Summary of Three Key Messages


Source: Pixabay


Volume II of the Fourth National Climate Assessment “summarizes the impacts of climate change on the United States, now and in the future” (GlobalChange.gov).

Chapter 8, “Coastal Effects,” summarizes the observed and expected impacts of climate change on coastal communities in the United States. The main concern is sea-level rise and increasing incidence of severe storm weather and coastal flooding. These climate impacts have and are expected to continue to have costly economic impacts on coastal infrastructure, decrease community and ecosystem resilience in coastal habitats, and increase vulnerability and displacement of socially and economically marginalized coastal communities.





The National Climate Assessment & The Global Change Research Program

The National Climate Assessment is a scientific report synthesized by the US Global Change Research Program.  The Program, established by Presidential Initiative in 1989 and mandated by Congress in 1990, is made up of 13 federal agencies that “conduct or use research on global change and its impacts on society." The purpose of the Program is “to assist the Nation and the world to understand, assess, predict and respond to human-induced and natural processes of global change” (GlobalChange.gov).

Chapter Writing Process

Chapter 8: Coastal Effects was developed by two Coordinating Lead Authors, five Chapter Authors, one Review Editor and four US Global Change Research Program Coordinators. Key messages were initially developed at a Chapter Lead Authors meeting; the team identified key vulnerabilities to focus on through 'ongoing interactions of the author team with coastal managers, planners, and stakeholders as well as a review of the existing literature.'

Tips for Chapter Review

Each chapter is broken down into sections by “Key Messages.” Some chapters may also begin with an executive summary or introduction before delving into the details of each Key Message. Each one- to two-sentence Key Message is followed by a short section that contains a summary of the literature and data that support and expand upon the message.

At the end of each chapter is a final “Traceable Accounts” section, which gives a brief overview of how the chapter was developed. This section then goes on to address the following for each Key Message: (1) describes where evidence for that key message was drawn from, including major projects and particularly critical studies, (2) acknowledges major uncertainties in conclusions and related data, and (3) classifies scientists’ confidence in conclusions.




Chapter 8 Key Messages

  • Coastal Economies and Property are Already at Risk
  • Coastal Environments are Already at Risk
  • Social Challenges Intensified


Key Message 1: Coastal Economies and Property are Already at Risk

‘America’s trillion-dollar coastal property market and public infrastructure are threatened today by the ongoing increase in the frequency, depth, and extent of tidal flooding due to sea level rise, with cascading impacts to the larger economy. Higher storm surges due to sea level rise and the increased probability of heavy precipitation events exacerbate the risk. Under a higher scenario (RCP8.5), many coastal communities will be transformed by the latter part of this century, and even under lower scenarios (RCP4.5 or RCP2.6), many individuals could suffer significant financial impacts as chronic high tide flooding leads to higher costs and lower property values. Actions to plan for and adapt to more frequent and severe coastal flooding may decrease direct losses and cascading economic impacts.’

Increasing severity of storms and tides have already resulted in costly infrastructure changes on the East Coast. Charleston, SC and Miami Beach, FL have installed pumping stations to clear floodwaters from the streets, while other coastal cities mobilize first responders frequently to close flooded streets. The New York Times recently published an article and photos on flooding impacts. 

Cited data and figures include:

  • Coastal flooding and erosion rates
  • 'Frequency of compound events with both surge and heavy precipitation'
  • Model projections of the 'frequency, depth and extent of both high tide and more severe, damaging coastal flooding'
  • Economic valuation of coastal properties
  • Economic value of coastal economies and infrastructure, such as 'coastal seaports for access to goods and services,' and 'critical energy infrastructure'

Data sources include:

  • Documented impacts to coastal properties and infrastructure
  • Satellite and tide gauge data
  • Projections from digital elevation models
  • Well-documented importance of coastal economies and infrastructure; economic ripple effects of impacts to property markets

Uncertainties include:

  • 'Magnitude of [sea level rise] that will occur and how it will vary across different regions' with different emissions levels.
  • 'Adaptive responses to sea level rise risk and impacts, including individual action and public policy development.'


Key Message 2: Coastal Environments are Already at Risk

Fisheries, tourism, human health, and public safety depend upon healthy coastal ecosystems. However, coastal ecosystems are being transformed, degraded, or lost due to climate change impacts, particularly sea level rise and higher numbers of extreme weather events. Restoring and conserving coastal ecosystems and adopting natural and nature-based infrastructure solutions can enhance community and ecosystem resilience to climate change and help ensure the continued health and viability of these environments and our coastal communities. Adapting to degradation of habitat integrity and quality may enhance community and ecosystem resilience and decrease both direct and indirect impacts.’

Coastal habitats such as wetlands in the Gulf of Mexico and marshes along the Atlantic coast provide natural buffers to erosion and break or slow down tidal waves. In turn, these habitats protect coastal communities and provide recreational opportunities. Sea level rise is resulting in habitat loss and degradation of these important ecosystems.

Cited data and figures include:

  • Benefits of coastal ecosystems to fisheries, shoreline erosion prevention, water quality, and recreation
  • Rate of loss of coastal wetlands and marsh degradation
  • Improved resilience of coastal communities from 'natural and nature-based infrastructure'

Data sources include:

  • Scientific literature on 'coastal fisheries, tourism, and human health and safety.'
  • Growing body of research on coastal restoration and 'living shorelines.'

Uncertainties include: 

  • 'Exact amount of coastal habitat loss that is due to climate change versus other human stressors or multiple stressors'. 
  • The amount of 'storm and erosion risk reduction' that is provided by different restoration techniques. 


Key Message 3: Social Challenges Intensified

'As the pace of coastal flooding and erosion accelerates, climate impacts along our coasts are exacerbating preexisting social inequities as communities face difficult questions on determining who will pay for current impacts and future adaptation strategies and if, how, or when to relocate vulnerable communities. These questions challenge existing legal frameworks; coastal communities will be among the first in the nation to test climate relevant legal frameworks and policies against these impacts. The answers to these questions will establish precedents that will affect both coastal and non-coastal regions.'

About 13 million people are potentially at risk from sea-level rise and will need to migrate. Many property owners cannot afford to modify their homes or move away without selling their property because of circumstances related to insurance and financial capital. These communities are more vulnerable to climate impacts including increased flood frequency. Pathways forward for these communities are unclear in the absence of clear policies and legal precedent.

Cited data and figures include: 

  • Exacerbation of existing, 'deeply ingrained inequities'
  • Observations from the 2017 hurricane season and a case study of adaptation to high tide flooding in Norfolk, Virginia
  • Adaptation strategies available to coastal property owners

Data sources include:

  • Reports and scientific literature
  • New tools 'to quantify risks and vulnerabilities along the coast,' such as the 'Coastal Community Social Vulnerability index and the Coastal Economic Vulnerability Index.'

Uncertainties include: 

  • How 'different types of coastal effects (chronic flooding v. storms) will impact areas and communities along the coast,' given 'the degree of variation between communities.'



Are you a scientist at the University of Washington? Attend the UW Program on Climate Change's workshop for this chapter's review. More details here



Note that all single quotes ‘’ cite from the Chapter Two draft text; material in double quotes “” may come from any of the sources below.

"Chapter 8: Coastal Effects Chapter" In Fourth National Climate Assessment. US Global Change Research Program. Chapter Lead: Elizabeth Fleming, USACE.

"About USGCRP." United States Global Change Research Program. Retrieved from: www.globalchange.gov/about









Contributor: PhD Student, Freshwater Ecology