Title: Fourth National Climate Assessment, Chapter 24: Northwest

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 24 Writing Process; Tips for Chapter Review
  3. Details: Key Messages; Summary of Three Key Messages


Source: Mark Stevens, Creative Commons


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 24, “Northwest,” dives into how  the region’s natural resource economy and  cultural heritage, 'deeply embedded within the natural environment,' will continue to be challenged by substantial warming in the region. As the Northwest continues ‘to warm during all seasons under all future emissions scenarios,’ impacts will be felt in both mountain areas, where there will be an increase in snow-pack loss and higher risk for insect infestations and wildfires, as well as ocean environments, which will experience changes 'such as warmer waters, altered chemistry, sea level rise, and shifts in the marine ecosystems.'  Climate-related changes in mountain and ocean environments 'will affect the Northwest’s natural resource economy, cultural heritage, built infrastructure, recreation, and the health and welfare of Northwest residents.' 




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 24: Northwest was developed by two Coordinating Lead Authors, five Chapter Authors, one Review Editor and four US Global Change Research Program Coordinators. Since the assessment focused on 'different aspects of the interaction between humans, the natural environment, and climate change... the author team required a depth and breadth of expertise that went beyond climate change science, and included social science, economics, health, Tribal communities, frontline communities, climate adaptation, as well as expertise in agriculture, forestry, hydrology, coastal and ocean dynamics, and ecology.' Chapter development consisted of technical discussions at workshops, teleconferences, and via email by chapter authors, and included stakeholder meetings and other outside input through 'comments submitted by the public, interested stakeholders, the National Academies of Sciences, and Federal agencies.'

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

  • Natural Resource Economy
  • Natural World / Cultural Heritage
  • Infrastructure
  • Health
  • Frontline Communities


Key Message 1: Natural Resource Economy

'Climate change is already affecting the Northwest’s diverse natural resources which support sustainable livelihoods and provide a robust foundation for Tribal and rural communities. Increasing temperatures, changing precipitation patterns, and changes in coastal ocean waters have already reduced agricultural and fishery productivity, while also providing new business opportunities for parts of the natural resource economy. Climate change is expected to continue affecting the natural resource sector, valued at over $180 billion per year, but the economic consequences will depend on future market dynamics and adaptation efforts. Proactive management can increase the resilience of natural resources and economies.'

Cited data and figures include:

  • 'Decreases in low- and mid-elevation snowpack and accompanying decreases in summer streamflow will impact snow- and water-based recreation, such as downhill and cross-country skiing, snowmobiling, boating, rafting, and fishing.'

  • 'Specialty crops, including apples and other tree fruits, are already experiencing changes. Earlier high spring temperatures have led to earlier flowering, which can lead to a mismatch with the availability of pollinators required for fruit setting.'

  • Projected impacts on Northwest fisheries ‘associated with ocean warming, acidification, and harmful algal blooms.’ This is expected to include ‘extensive fisheries closures across all of the region’s coastal fisheries, with severe economic and cultural effects on commercial and subsistence shellfish industries.'

Data sources include:

Uncertainties include:

  • 'Impacts on the economic viability of natural resource-based economies in the region,' such as 'the degree to which individual sectors are integrated into global commodity markets.'
  • 'Effects of potential increases in supply volatility' in timber markets, and 'the consequences for investment and ultimately on harvest and milling jobs.'
  • 'How individual actors will respond to climate changes.'
  • 'How precisely [climate impacts] will affect natural resource managers’ financial security, as well as other factors important to sustainable livelihoods and community well-being.'



Key Message 2: Natural World / Cultural Heritage

'Valued aspects of Northwest heritage and quality of life—the natural environment, wildlife, outdoor recreation, and Tribal cultures—will change with the climate. Increasing temperatures, reduced water availability, changing snow conditions, forest fires, habitat fragmentation, and other changes are endangering the well-being of a wide range of wildlife, threatening popular recreational activities and tribal subsistence and culture. For the Tribes, the health and vitality of the salmon runs is a direct indicator of the wider health of the region.'

Cited data and figures include:

  • Projected habitat loss / fragmentation and increased mortality ‘of waterfowl, trout and salmon and, other coldwater fish. amphibians, wolverines, lynxes, and snowshoe hares’ from ‘Droughts, wildfires, reduced snowpack and persistence, shifted flood timing, and heat stress.'
  • High risk of salmon, 'one of the most important First Foods for Northwest Tribes' for 'subsistence, economical, and ceremonial purposes,' to climate change impacts. Risks are a result of projected 'decreasing summer flows due to changes in seasonal precipitation and reduced snowpack, habitat loss through increasing storm intensity and flooding, and physiological and behavioral sensitivity and increasing mortality due to warmer stream and ocean temperatures, and cascading food web effects due to ocean acidification.'
  • ‘Multiple lines of evidence’ verifying ‘that reduced snowfall and snowpack in the future will adversely impact winter and snow-based recreation fewer skiing visitation rates. This will also adversely affect summer water-based recreation such as boating and rafting, although warmer temperatures in the future can increase demand for water-based recreation and visitations rates to parks.'

Data sources include:

  • Peer-reviewed studies
  • NOAA and USGCRP Reports

Uncertainties include: 

  • 'The perceived importance of future recreation opportunities' prioritization in people's quality of life, despite the direct reduction of recreational opportunities.'
  • 'Effects of climate change on game species;' climate impacts could have a positive or negative effect on certain game species depending on 'which [climate] processes may dominate consequences for game, and how managers might be ablet o effectively adapt to changing climate.'


Key Message 3: Infrastructure

'Existing water, transportation, and energy infrastructure already face challenges from flooding, landslides, drought, wildfire, and heat waves. Future climate change raises the risk for many of these extreme events, potentially compromising the reliability of water supplies, hydropower, and transportation across the region. Isolated communities and those with systems that lack redundancy are the most vulnerable. Adaptation strategies that address more than one sector, or are coupled with social and environmental co-benefits, can increase resilience.'

Cited data and figures include: 

  • Investigations 'highlighting the vulnerability of water supply, hydropower, and transportation' to 'extreme events such as flooding, landslides, drought, wildfire and heat waves.'
  • Projected heavy rainfall events, which 'can lead to slope instabilities and landslides, which can close roadways and railways.'
  • Projected increase in wildfires, which 'can result in road and railway closures, reduced water quality in reservoirs, and impacts on the energy sector.'

Data sources include:

  • Peer-reviewed studies

  • Reports by Seattle City Light, Washington State Department of Transportation and the US Department of Energy

Uncertainties include: 

  • Demographic shifts and the important of different infrastructure; fluctuations in 'migration to and within the region' may change 'the relative importance of different types of infrastructure.'
  • Non-climate stresses and interaction with climate-related stresses
  • The 'role of redundancy in minimizing or managing impacts. Metrics for determining the extent to which networking or emergency/back-up systems yield adaptive capacity are not currently available at the regional scale.'



Are you a scientist at or near 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 2: Our Changing Climate." In Fourth National Climate Assessment. US Global Change Research Program. Chapter Lead: Katharine Hayhoe, Texas Tech University.

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









Contributor: M.S. Student, Aquatic and Fishery Sciences