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Northwest Regional Climate Change
Washington, Oregon, Idaho and Western Montana
Information from the U.S. Global Change Research Program, June, 2009
Higher Temperatures and Precipitation Change
Over the past century the regional annual average temperature of the Washington, Oregon and Idaho region rose by about 1.5° Fahrenheit. Some areas experienced an average temperature increase of up to 4° Fahrenheit. Over the next century climate models project another rise of between 3 and 10° Fahrenheit.
Significant precipitation changes are also expected although these are more difficult to predict. Winter precipitation is expected to increase, while summer precipitation is projected to decrease. These changes in precipitation will impact water supplies, snowpack thickness, stream discharge, sea level, forests, and many other aspects of life and environment of the Northwest United States. A number of these impacts are featured below.
| Rising water temperatures will stress salmon |
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Salmon and other coldwater species will experience additional stresses as a result of rising water temperatures and declining summer streamflows.
Northwest salmon populations are already at historically low levels due to variety of human-induced stresses. Climate change affects salmon throughout their life stages and poses an additional stress. Studies suggest that about a third of the current habitat for the Northwest's salmon and other coldwater fish will no longer be suitable for them by the end of this century due to climate change. Photo copyright by iStockPhoto / Oksanaphoto. |
| Wildfires will challenge forests and ecosystems |
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Increased insect outbreaks, wildfires, and changing species composition in forests will pose challenges for ecosystems and the forest products industry.
Higher summer temperatures and earlier spring snowmelt are expected to increase the risk of forest fires by increasing summer moisture deficits; this pattern has already been observed in recent decades. Drought stress and higher temperatures will decrease tree growth in most low- and mid-elevation forests and will also increase the frequency and intensity of mountain pine beetle and other insect attacks, further increasing fire risk and reducing timber production, an important part of the regional economy. Photo copyright by iStockPhoto / P. Pattavina. |
| Sea-level rise will cause flooding and erosion |
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Sea-level rise along vulnerable coastlines will result in increased erosion and the loss of land.
Climate change is expected to exacerbate many of the stresses and hazards currently facing the coastal zone. Sea-level rise will increase erosion of the coast and cause the loss of beaches and significant coastal land areas. Among the most vulnerable parts of the coast is the heavily populated south Puget Sounds region, which includes the cities of Olympia, Tacoma, and Seattle, Washington. Landsat GeoCover image by NASA. |
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| Climate change will have a number of severe impacts on the northwestern states of Washington, Idaho and Oregon. This page illustrates a number of the more significant impacts. Map by Geology.com and MapResources.. |
| Declining snowpack will reduce water supplies |
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Declining springtime snowpack leads to reduced summer streamflows, straining water supplies.
The Northwest is highly dependent on temperature-sensitive springtime snowpack to meet growing and often competing water demands such as municipal and industrial uses, agricultural irrigation, hydropower production, navigation, recreation, and in-stream flows that protect aquatic ecosystems including threatened and endangered species. Higher temperatures are causing more winter precipitation to fall as rain rather than snow and are contributing to earlier snowmelt. Further declines in snowpack are projected, reducing the amount of water available during the warm season. Photo copyright by iStockPhoto / M. Blache. |
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