This website is the digital version of the 2014 National Climate Assessment, produced in collaboration with the U.S. Global Change Research Program.

For the official version, please refer to the PDF in the downloads section. The downloadable PDF is the official version of the 2014 National Climate Assessment.

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Welcome to the National Climate Assessment

The National Climate Assessment summarizes the impacts of climate change on the United States, now and in the future.

A team of more than 300 experts guided by a 60-member Federal Advisory Committee produced the report, which was extensively reviewed by the public and experts, including federal agencies and a panel of the National Academy of Sciences.

Explore the effects of climate change
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Changes in the timing of streamflow reduce water supplies for competing demands. Sea level rise, erosion, inundation, risks to infrastructure, and increasing ocean acidity pose major threats. Increasing wildfire, insect outbreaks, and tree diseases are causing widespread tree die-off.

Explore how climate change is affecting the Northwest.



The Northwest region includes the states of Idaho, Oregon, and Washington. The Highlights section below offers a high-level overview of climate change impacts on this region, including the four Key Messages and selected topics. (see Ch. 21: Northwest)

Key Message: Water-related Challenges

Changes in the timing of streamflow related to changing snowmelt have been observed and will continue, reducing the supply of water for many competing demands and causing far-reaching ecological and socioeconomic consequences.

Key Message: Coastal Vulnerabilities

In the coastal zone, the effects of sea level rise, erosion, inundation, threats to infrastructure and habitat, and increasing ocean acidity collectively pose a major threat to the region.

Key Message: Impacts on Forests

The combined impacts of increasing wildfire, insect outbreaks, and tree diseases are already causing widespread tree die-off and are virtually certain to cause additional forest mortality by the 2040s and long-term transformation of forest landscapes. Under higher emissions scenarios, extensive conversion of subalpine forests to other forest types is projected by the 2080s.

Key Message: Adapting Agriculture

While the agriculture sector’s technical ability to adapt to changing conditions can offset some adverse impacts of a changing climate, there remain critical concerns for agriculture with respect to costs of adaptation, development of more climate resilient technologies and management, and availability and timing of water.



Rising summer temperatures and changing water flows threaten salmon and other fish species.

The Northwest’s economy, infrastructure, natural systems, public health, and agriculture sectors all face important climate change related risks. Impacts on infrastructure, natural systems, human health, and economic sectors, combined with issues of social and ecological vulnerability, will unfold quite differently in largely natural areas, like the Cascade Range, than in urban areas like Seattle and Portland,10 or among the region’s many Native American tribes.11,12

Insects and Fire in Northwest Forests Insects and Fire in Northwest Forests Details/Download

Seasonal water patterns shape the life cycles of the region’s flora and fauna, including iconic salmon and steelhead, and forested ecosystems.13 Adding to the human influences on climate, human activities have altered natural habitats, threatened species, and extracted so much water that there are already conflicts among multiple users in dry years. As conflicts and trade-offs increase, the region’s population continues to grow. Particularly in the face of climate change, the need to seek solutions to these conflicts is becoming increasingly urgent.

Future Shift in Timing of Streamflows Future Shift in Timing of Streamflows Details/Download

Nisqually River Delta

In Washington’s Nisqually River Delta, large-scale estuary restoration to assist salmon and wildlife recovery provides an example of adaptation to climate change and sea level rise. After a century of isolation behind dikes, much of the Nisqually National Wildlife Refuge was reconnected with tidal flow in 2009 by removal of a major dike and restoration of 762 acres, with the assistance of Ducks Unlimited and the Nisqually Indian Tribe. This reconnected more than 21 miles of historical tidal channels and floodplains with Puget Sound.9 A new exterior dike was constructed to protect freshwater wetland habitat for migratory birds from tidal inundation, future sea level rise, and increasing river floods.

Observed regional warming has been linked to changes in the timing and amount of water availability in basins with significant snowmelt contributions to streamflow. By 2050, snowmelt is projected to shift three to four weeks earlier than the last century’s average, and summer flows are projected to be substantially lower, even for a scenario that assumes emissions reductions (B1).8 These reduced flows will require trade-offs among reservoir system objectives,14 especially with the added challenges of summer increases in electric power demand for cooling and additional water consumption by crops and forests.

Climate change will alter Northwest forests by increasing wildfire risk, insect and disease outbreaks, and by forcing longer-term shifts in forest types and species. Many impacts will be driven by water deficits, which increase tree stress and mortality, tree vulnerability to insects, and fuel flammability. By the 2080s, the median annual area burned in the Northwest would quadruple relative to the 1916-2007 period to 2 million acres (range 0.2 to 9.8 million acres) under a scenario that assumes continued increases in emissions through mid century and gradual declines thereafter (A1B).6


  1. Bailey, R. G., 1995: Description of the Ecoregions of the United States (2nd ed.). 1995. Misc. Pub. No. 1391. U.S. Department of Agriculture, Forest Service. URL | Detail

  2. Eidenshink, J., B. Schwind, K. Brewer, Z. Zhu, B. Quayle, and S. Howard, 2007: A project for monitoring trends in burn severity. Fire Ecology, 3, 3-21. URL | Detail

  3. Elsner, M. M., L. Cuo, N. Voisin, J. S. Deems, A. F. Hamlet, J. A. Vano, K. E. B. Mickelson, S. Y. Lee, and D. P. Lettenmaier, 2010: Implications of 21st century climate change for the hydrology of Washington State. Climatic Change, 102, 225-260, doi:10.1007/s10584-010-9855-0. | Detail

  4. Hamlet, A. F., M. McGuire Elsner, G. S. Mauger, S. - Y. Lee, I. Tohver, and R. A. Norheim, 2013: An overview of the Columbia Basin Climate Change Scenarios project: Approach, methods, and summary of key results. Atmosphere-Ocean, 51, 392-415, doi:10.1080/07055900.2013.819555. URL | Detail

  5. Isaak, D. J., S. Wollrab, D. Horan, and G. Chandler, 2011: Climate change effects on stream and river temperatures across the northwest US from 1980–2009 and implications for salmonid fishes. Climatic Change, 113, 499-524, doi:10.1007/s10584-011-0326-z. URL | Detail

  6. Littell, J. S., E. E. Oneil, D. McKenzie, J. A. Hicke, J. A. Lutz, R. A. Norheim, and M. M. Elsner, 2010: Forest ecosystems, disturbance, and climatic change in Washington State, USA. Climatic Change, 102, 129-158, doi:10.1007/s10584-010-9858-x. | Detail

  7. Lynn, K., O. Grah, P. Hardison, J. Hoffman, E. Knight, A. Rogerson, P. Tillmann, C. Viles, and P. Williams, 2013: Tribal communities. Climate Change in the Northwest: Implications for Our Landscapes, Waters, And Communities, P. Mote, Dalton, M.M., and Snover, A.K., Eds., Island Press, 224. | Detail

  8. ,, 2011: Ch. 5: Impacts in the next few decades and coming centuries. Climate Stabilization Targets: Emissions, Concentrations, and Impacts over Decades to Millennia,, Committee on Stabilization Targets for Atmospheric Greenhouse Gas Concentration, The National Academies Press, 298. URL | Detail

  9. Smith, W. B., P. D. Miles, C. H. Perry, and S. A. Pugh, 2009: Forest Resources of the United States, 2007. General Technical Report WO-78. 336 pp., U.S. Department of Agriculture. Forest Service, Washington, D.C. URL | Detail

  10. Solecki, W., and C. Rosenzweig, 2012: U.S. Cities and Climate Change: Urban, Infrastructure, and Vulnerability Issues, Technical Input Report Series, U.S. National Climate Assessment.. URL | Detail

  11. ,, 2012: Forest Service, Insect & Disease Detection Survey Data Explorer. U.S. Department of Agriculture, U.S. Forest Service. URL | Detail

  12. ,, 2010: Rising to the Urgent Challenge: Strategic Plan for Responding to Accelerating Climate Change. 32 pp., U.S. Fish and Wildlife Service, U.S. Department of the Interior, Washington, D.C. URL | Detail

  13. ,, 2012: National Monitoring Trends in Burn Severity (MTBS) Burned Area Boundaries Dataset. U.S. Geological Survey. URL | Detail

  14. Voggesser, G., K. Lynn, J. Daigle, F. K. Lake, and D. Ranco, 2013: Cultural impacts to tribes from climate change influences on forests. Climatic Change, 120, 615-626, doi:10.1007/s10584-013-0733-4. | Detail

The National Climate Assessment summarizes the impacts of climate change on the United States, now and in the future.

A team of more than 300 experts guided by a 60-member Federal Advisory Committee produced the report, which was extensively reviewed by the public and experts, including federal agencies and a panel of the National Academy of Sciences.

United States Global Change Research Program logo United States Global Change Research Program participating agency logos